Decompression sickness: Difference between revisions

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   Name          = Caisson disease  
   Name          = Caisson disease  
[decompression sickness] |
[decompression sickness] |
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{{CMG}}
{{CMG}} {{AE}} {{MIR}} {{JK}}
{{SI}}
{{SK}} Decompression illness; DCS; the diver's disease; the bends; Caisson disease; aerobullosis
 
==Overview==
Decompression sickness (DCS) is a multi-organ condition characterized by a varied clinical manifestations resulting from an exposure to reduced barometric pressures that leads to a normally dissolved inert gases (mainly nitrogen) in body fluids and tissues to come out of physical solution, and develops a free gas phase by forming an intravascular and extravascular bubbles. The likelihood of DCS is associated with the extent of bubble formation which subsequently causes minor symptoms from a few bubbles formation to a large bubble presenting with the multiorgan failure and death. The severity and nature of the DCS injury vary from mild systemic, musculoskeletal and cutaneous manifestations to severe, life-threatening neurological and cardiorespiratory complications. It is mostly observed in underwater decompression diving activities (e.g SCUBA) and depressurisation events such as emerging from a caisson, flying in an unpressurised aircraft at altitude, and extravehicular activity from spacecraft. The clinical presentation can show an individual susceptibility by varying from day to day under the similar circumstances. The classification of types of DCS based on its symptoms has evolved over years since its origin and research conducted to prevent it. It is not common to report it if the divers follow the recommended guidelines by using dive tables or dive computers to limit their period of exposure and control their rate of ascent speed. If DCS is suspected, it is treated by airway stabilization, high flow oxygen, and hyperbaric therapy in a recompression chamber. An early treatment ensures a significantly higher recovery rate.
 
==Historical Perspective==
{{Wikisource1911Enc|Caisson Disease}}
*1670: Sir Robert Boyle described the first case of DCS in animals by conducting an experiment on a viper in a vacuum and observing the bubble formation in its eye with significant physical symptoms of discomfort. <ref name="DCS Acott">Acott, C. (1999). "A brief history of diving and decompression illness". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801 </ref>
*1841: Jacques Triger proposed that the two miners while working in the pressurised caisson work developed the symptoms of DCS and thus, documented the first case of DCS in humans. <ref name="DCS Acott">Acott, C. (1999). "A brief history of diving and decompression illness". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801 </ref>
*1847: The French physicians B. Pol and T.J. Watelle explained the effectiveness of recompression in caisson workers for the use of the treatment of DCS. <ref name="DCS Acott">Acott, C. (1999). "A brief history of diving and decompression illness". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801 </ref> <ref name="DCS Hill"> Hill, L (1912). Caisson sickness, and the physiology of work in compressed air. London E. Arnold </ref>
*1857: Felix Hoppe-Seyler supported Boyle's study findings. He further observed that the bubble formation is the underlying cause of sudden death in compressed air workers and recommended recompression therapy as the mode of treatment. <ref name="DCS Huggins"> Huggins, Karl E. (1992). "Dynamics of decompression workshop". Course Taught at the University of Michigan. ; Huggins 1992, chpt. 1 page 8 </ref>
*1861:  Bucquoy proposed the hypothesis by comparing an injection of air in the veins with the blood gases returning to the free state under the process of decompression. <ref>Trucco, Jean-Noël; Biard, Jef; Redureau, Jean-Yves; Fauvel, Yvon (3 May 1999). "Table Marine National 90 (MN90): Version du 03/05/1999" (PDF). Comité interrégional Bretagne & Pays de la Loire; Commission Technique Régionale. (in French). F.F.E.S.S.M. </ref>
*1868: Alfred Le Roy de Méricourt labelled DCS as an occupational hazard for the sponge divers. <ref name="DCS Hill"> Hill, L (1912). Caisson sickness, and the physiology of work in compressed air. London E. Arnold </ref>
*1873: Dr. Andrew Smith studied 110 DCS cases during the construction of the Brooklyn Bridge and coined the terms "caisson disease" and "compressed air illness". Similarly, the term "the bends" was extracted from the fashionable ladies of the period "the Grecian Bend" as the workers emerging from pressurized construction on the Brooklyn Bridge adopted a posture similar to them.<ref name="DCS Acott">Acott, C. (1999). "A brief history of diving and decompression illness". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801 </ref>  <ref name="DCS Huggins"> Huggins, Karl E. (1992). "Dynamics of decompression workshop". Course Taught at the University of Michigan. ; Huggins 1992, chpt. 1 page 8 </ref> <ref name="pmid15686275">{{cite journal| author=Butler WP| title=Caisson disease during the construction of the Eads and Brooklyn Bridges: A review. | journal=Undersea Hyperb Med | year= 2004 | volume= 31 | issue= 4 | pages= 445-59 | pmid=15686275 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15686275  }} </ref>
*1878: Paul Bert found that the nitrogen gas bubbles released from tissues and blood during or after decompression are responsible for the development of the DCS and further showed that breathing oxygen after developing DCS can help in relieving its symptoms. <ref> Bert, P. (1878). "Barometric Pressure: researches in experimental physiology". Translated By: Hitchcock MA and Hitchcock FA. College Book Company; 1943 </ref>
*1889–90: Ernest William Moir made the first medical airlock when he realized that recompression is the main modality of the treatment to prevent the workforce digging the Hudson River Tunnel dying from DCS. <ref> John L. Phillips, The Bends: Compressed Air in the History of Science, Diving, and Engineering, Yale University Press (1998) - Google Books p 103 </ref> <ref>Moon, Richard (March 2000). "The Natural Progression of Decompression Illness and Development of Recompression Procedures" (PDF). SPUMS Journal. 30 (1): 39 </ref>
*1908:John Scott Haldane prepared the first recognized decompression table for the British Admiralty which was based on experiments performed on goats using an end point of symptomatic DCS. <ref name="DCS Acott">Acott, C. (1999). "A brief history of diving and decompression illness". South Pacific Underwater Medicine Society Journal. 29 (2). ISSN 0813-1988. OCLC 16986801 </ref> <ref name="pmid20474365">{{cite journal| author=Boycott AE, Damant GC, Haldane JS| title=The Prevention of Compressed-air Illness. | journal=J Hyg (Lond) | year= 1908 | volume= 8 | issue= 3 | pages= 342-443 | pmid=20474365 | doi=10.1017/s0022172400003399 | pmc=2167126 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20474365  }} </ref>
*1912: Chief Gunner George D. Stillson of the [[United States Navy]] created a program to evaluate and refine Haldane's tables which subsequently led to the first publication of the United States Navy Diving Manual and the establishment of a Navy Diving School in Newport, Rhode Island. <ref>Stillson, GD (1915). "Report in Deep Diving Tests". US Bureau of Construction and Repair, Navy Department. Technical Report </ref>
 
==Classification==
 
*In 1960, The ''Golding Classification'' was introduced and categorized DCS into type 1 DCS and type 2 DCS. <ref>Golding FC , Griffi ths P , Hempleman HV , Paton WDM , Walder DN . Decompression sickness during construction of the Dartford tunnel . Br J Ind Med 1960 ; 17 : 167 – 80 </ref>
 
'''''Table 1 shows the Golding classification of DCS:'''''
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | FEATURES
 
! style="background:#4479BA; color: #FFFFFF;" | TYPE 1
 
! style="background:#4479BA; color: #FFFFFF;" | TYPE 2
 
|-
 
| style="background:#DCDCDC;" align="center" | Systems involved
 
| Joints, skin, and lymphatics
 
| Neurological, inner ear, and cardiopulmonary
 
|-
 
| style="background:#DCDCDC;" align="center" | Onset of symptoms
 
| Build in intensity
 
| Gradual or abrupt
 
|-
 
| style="background:#DCDCDC;" align="center" | Severity
 
| Mild
 
| Severe
 
|}
 
*This classification is not frequently used in making the diagnosis of DCS following upgradation of the treatment protocols and variable presentations of signs and symptoms. <ref name="DCS Brubakk"> {{cite book | last = Brubakk | first = Alf | title = Bennett and Elliott's physiology and medicine of diving | publisher = Saunders | location = Edinburgh New York | year = 2003 | isbn = 978-0-7020-2571-6 }} </ref>
 
*All the manifestations, whether DCS or [[arterial gas embolism]] (AGE), were categorized under the general term “[[decompression illness (DCI)]]” when the exact diagnosis cannot be finalized because both of them develops from the gas bubble formation in the body, have overlapping of their spectra of signs and symptoms, and similar treatment methods. <ref>Francis, T James R; Smith, DJ (1991). "Describing Decompression Illness". 42nd Undersea and Hyperbaric Medical Society Workshop. 79(DECO)5–15–91. </ref>
 
==Pathophysiology==
 
*The pathophysiology of DCS is in accordance with '''''Henry’s law'''''. It states that the solubility of a gas in a liquid is directly proportional to the amount of the pressure exerted on the gas and liquid. Thus, the amount of inert gases (eg, nitrogen, helium) dissolved in the blood and tissues increases at higher pressure, and hence the development of DCS depends on the depth and the duration of the dive.
 
*During a dive, the partial pressure of nitrogen and oxygen increases which results in creating a diffusion gradient favoring an uptake of nitrogen into the bloodstream and tissues. The physiology of the lungs is to functions as a vehicle for the gaseous exchange and elimination from the body under normal circumstances. As the atmospheric pressure decrease during the ascent, more nitrogen precipitates from the tissues into the bloodstream and then diffuses back into the alveoli for exhalation process. If ascent occurs too rapidly or the elimination gradient is so steep, the gas quickly dissipates from the tissues and blood forming small air bubbles. This process is called ''“out gassing”'' or ''“off gassing”''. Conversely, a slow ascent favors an equilibrium to be achieved gradually, and prevents the rapid changes in the partial pressure of nitrogen in the bloodstream. Hence, the amount of bubble formation depends on the depth and duration of the dive, and the rate of the ascent. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
*Venous bubbles may form ''de novo'' or result from the intravascular release of tissue bubbles. The venous gas emboli usually get filtered at an arteriole level on reaching the lungs. However, the bubbles may pass directly into the arterial circulation if the pulmonary arterial pressure (PAP) rises after underwater diving. <ref name="DCS Edmonds"> Edmonds, Lowry, Pennefather, Walker. Diving and Subaquatic Medicine 4th edition Arnold 2002 </ref> <ref>Gorman, Des. Accidental arterial gas embolism. Emergency Medicine. 14(4):364-370, December 2002</ref>
 
#Bubbles ''primarily'' travel to vital organs such as the nervous system; and get lodged in arterioles and capillary beds causing a mass effect. These bubbles obstruct venous outflow and occlude arteries, as well as cause a shearing force on endovascular surfaces and impairs vascular integrity during their transit. The disturbed vascular permeability consequently leads to hemoconcentration, disturbance of microvascular flow, and a breakdown in the blood brain barrier. <ref> NHS Commissioning Board. April 2013. Clinical Commissioning Policy: Hyperbaric Oxygen Therapy </ref>
#Bubbles cause ''secondary'' multiple biochemical effects by activating platelets, complement, leucocytes and the clotting cascade; and hence, results in an inflammatory response in the affected tissues. <ref>Kindwall E and Whelan H, Hyperbaric Medicine Practice, 3rd Edition (2008), Chapter 4 page 71-89 </ref>
#''Autochthonous'' or ''extravascular'' bubbles arise spontaneously, and are more likely to form in tissues with high gas content and poor perfusion because the large amount of gas in the tissues such as spinal cord white matter, adipose tissue, and periarticular tissue cannot be removed by the low perfusing blood volume. <ref name="DCS Edmonds"> Edmonds, Lowry, Pennefather, Walker. Diving and Subaquatic Medicine 4th edition Arnold 2002 </ref>
 
*Bubbles are responsible for the proximate cause of damage, whereas the several pro-inflammatory activated pathways leads to the progression of an injury. Thus, DCS can have an evolving course with inflammatory mediated manifestations worsening with a period of time.
 
==Clinical Features==
 
*'''''Clinical presentation''''': It is frequently idiosyncratic as its "typical" pattern gives an atypical presentation due to the origin of the bubble formation in any part of the body. The US Navy listed the symptoms of DCS in a decreasing order of their overall prevalence in '''''Table 2:''''' <ref name="DCS Powell">{{cite book | last = Powell | first = Mark | title = Deco for divers : a diver's guide to decompression theory and physiology | publisher = AquaPress | location = Southend-on-Sea, Essex | year = 2008 | isbn = 978-1-905492-07-7 }} </ref>
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | Symptoms
 
! style="background:#4479BA; color: #FFFFFF;" | Features in %
 
|-
 
| style="background:#DCDCDC;" align="center" | Local joint pain
 
| 89
 
|-
 
| style="background:#DCDCDC;" align="center" | Arm symptoms
 
| 70
 
|-
 
| style="background:#DCDCDC;" align="center" | Leg symptoms
 
| 30
 
|-
 
| style="background:#DCDCDC;" align="center" | Dizziness
 
| 5.3
 
|-
 
| style="background:#DCDCDC;" align="center" | Paralysis
 
| 2.3
 
|-
 
| style="background:#DCDCDC;" align="center" | Shortness of breath
 
| 1.6
 
|-
 
| style="background:#DCDCDC;" align="center" | Extreme fatigue
 
| 1.3
 
|-
 
| style="background:#DCDCDC;" align="center" | Collapse/unconsciousness
 
| 0.5
 
|}
 
 
*'''''Onset''''': The median time to symptom/sign onset is 30 minutes and severe neurologic symptoms might present as early as within 10 minutes; and however, majority of symptoms and signs develops within 24 to 48 hours of emerging from the water. The U.S. Navy and Technical Diving International have published a table that documents time to onset of first presenting symptom. The table does not differentiate between types of DCS, or types of symptom. <ref>U.S. Navy Supervisor of Diving (2008). U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. vol.5. U.S. Naval Sea Systems Command. pp. 20–25</ref> <ref>TDI Decompression Procedures Manual (Rev 1c), page 38 </ref>
'''''Table 3 shows the time of onset of symptoms among DCS suspected cases:'''''
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | Time to onset
 
! style="background:#4479BA; color: #FFFFFF;" | Percentage of cases
 
|-
 
| style="background:#DCDCDC;" align="center" | Within 1 hour
 
| 42%
 
|-
 
| style="background:#DCDCDC;" align="center" | Within 3 hour
 
| 60%
 
|-
 
| style="background:#DCDCDC;" align="center" | Within 8 hour
 
| 83%
 
|-
 
| style="background:#DCDCDC;" align="center" | Within 24 hour
 
| 98%
 
|-
 
| style="background:#DCDCDC;" align="center" | Within 48 hour
 
| 100%
 
|}
 
*''Joints'' DCS is most frequently noticed in shoulders, elbows, knees, and ankles. ''Shoulder'' is the most common site for altitude and bounce diving; and the ''knees'' and ''hip'' joints for saturation and compressed air work. The symptoms of limb bends arises from increased intermedullary pressure in the ends of long bones; and gas phase separation along ligaments and tendon sheaths, and thus presenting with an extreme discomfort from the simple mechanical distension and movement.
*''Dermatological'' manifestations are due to the blood extravasated from the cutaneous vessels as a consequence of bubble induced endothelial injury.
*''Pulmonary'' DCS ("the chokes") is rarely reported in divers; and believed to arise from an extremely huge load of venous bubbles in the pulmonary artery which results in an elevated pulmonary artery and right ventricular pressures, and further increasing the interstitial fluid and hence, leads to the development of the chokes or difficult breathing.
*''Spinal cord'' DCS have two interrelated mechanisms. The first is obstruction of venous outflow of the spinal cord in the epidural plexus which relatively have a slow blood perfusion rate. Once this process develops, it results in an ongoing and progressive diminution of blood flow to the cord, and thereafter, the second process proceeds with the in-situ bubble formation within the tissue of the spinal cord. <ref name="DCS Powell">{{cite book | last = Powell | first = Mark | title = Deco for divers : a diver's guide to decompression theory and physiology | publisher = AquaPress | location = Southend-on-Sea, Essex | year = 2008 | isbn = 978-1-905492-07-7 }}</ref> <ref>Frans Cronje (5 August 2014). All That Tingles Is Not Bends (video). DAN Southern Africa </ref>
 
'''''Table 4 shows symptoms and signs of different DCS types:''''' <ref name="DCS Brubakk"> {{cite book | last = Brubakk | first = Alf | title = Bennett and Elliott's physiology and medicine of diving | publisher = Saunders | location = Edinburgh New York | year = 2003 | isbn = 978-0-7020-2571-6 }} </ref>
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | DCS type
 
! style="background:#4479BA; color: #FFFFFF;" | Bubble location
 
! style="background:#4479BA; color: #FFFFFF;" | Signs and symptoms
 
|-
 
| style="background:#DCDCDC;" align="center" | Musculoskeletal: BENDS
 
| Mostly large joints (elbows, shoulders, hip, wrists, knees, ankles)
 
|
*Characteristics: Localized deep pain, ranging from mild to excruciating; dull ache (sometimes); sharp pain (rarely)
*Aggravating factor: Active and passive motion of the joint
*Relieving factor: Bending the joint to a comfortable position
*Onset: Immediate or few hours later in case of altitude induced DCS
 
|-
 
| style="background:#DCDCDC;" align="center" | Cutaneous: SKIN BENDS
 
| Skin
 
|
*Site: Itching around the ears, face, neck, arms, and upper torso
*Formication: Sensation of tiny insects crawling over the skin
*Cutis Marmorata: Mottled or marbled skin usually around the shoulders, upper chest and abdomen with itching
*Pitting edema: Swelling of the skin accompanied by tiny scar-like skin depressions
 
|-
 
| style="background:#DCDCDC;" align="center" | Neurologic
 
| Brain
 
|
*Most common: Headache and visual disturbances
*Visual changes: Spots in visual field (scotoma), tunnel vision, double vision (diplopia), or blurry vision 
*Confusion or memory loss
*Unexplained extreme fatigue or behavior changes
*Seizures, dizziness, vertigo, nausea, vomiting and unconsciousness may occur 
 
|-
 
| style="background:#DCDCDC;" align="center" | Neurologic
 
| Spinal cord
|
*Abnormal sensations such as burning, stinging, and tingling around the lower chest and back
*Symptoms may spread from the feet up and may be accompanied by ascending weakness or paralysis 
*Girdling abdominal or chest pain
|-
 
| style="background:#DCDCDC;" align="center" | Neurologic
 
| Peripheral Nerves
 
|
*Urinary and rectal incontinence
*Abnormal sensations, such as numbness, burning, stinging, tingling and paresthesia 
*Muscle weakness or twitching
 
|-
 
| style="background:#DCDCDC;" align="center" | Constitutional
 
| Whole body
 
|
*Headache
*Unexplained fatigue 
*Generalized malaise, poorly localized aches
 
|-
 
| style="background:#DCDCDC;" align="center" | Audiovestibular
 
| Inner ear
 
|
*Loss of balance
*Dizziness, vertigo, nausea, vomiting 
*Hearing loss
 
|-
 
| style="background:#DCDCDC;" align="center" | Pulmonary CHOKES
 
| Lungs
 
|
*Dry persistent cough
*Burning chest pain under the sternum, aggravated by breathing 
*Shortness of breath
 
|-
 
| style="background:#DCDCDC;" align="center" | Dysbaric osteonecrosis <ref name="urlDecompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition">{{cite web |url=https://www.msdmanuals.com/professional/injuries-poisoning/injury-during-diving-or-work-in-compressed-air/decompression-sickness |title=Decompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition |format= |work= |accessdate=}}</ref>
 
| Bones
 
|
*Late manifestation and often occurs without any previous symptoms
*An insidious form caused by prolonged or closely repeated exposures to increased pressure
*Typically found in people working in compressed air and in deep commercial rather than recreational divers
*Deterioration of shoulder and hip articular surfaces cause chronic pain and severe joint disability
 
|}
 
==Differential Diagnosis==
*Differential diagnosis is the process by which medical personnel rule out which of the potential condition is most likely responsible for the presenting symptoms when two or more probable conditions have overlapping symptoms among the diving-related injuries.
*An alternative diagnosis should also be suspected if severe symptoms begin more than six hours following decompression without an altitude exposure or if any symptom occurs more than 24 hours after surfacing. <ref>Moon, Richard E (1998). "Assessment of patients with decompression illness". South Pacific Underwater Medicine Society Journal. 28 (1). </ref>
 
'''''Table 5 below shows various different medical conditions mimicking the DCS:''''' <ref name="DCS Richard">Richard D Vann, Frank K Butler, Simon J Mitchell, Richard E Moon. Decompression illness. Vol 377 January 8, 2011; pg: 153-164 </ref>
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | Medical condition
 
! style="background:#4479BA; color: #FFFFFF;" | Clinical characteristics
 
|-
 
| style="background:#DCDCDC;" align="center" | Arterial Gas Embolism (AGE) <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
|
*Pulmonary Barotrauma: It usually occurs when the air expands to cause the lung rupture and releases gas bubbles directly into the arterial circulation.
*Typical presentation: A diver who surfaces unconscious and remains so, or who loses consciousness within minutes of surfacing.
*A true medical emergency condition
*Rapid evacuation to a treatment facility is paramount.
 
|-
 
| style="background:#DCDCDC;" align="center" | Inner-ear barotrauma
 
|
*Usually occurs during descent
*Tinnitus, hearing loss, and persistent vertigo <ref>Klingmann C, Praetorius M, Baumann I, Plinkert PK. Barotrauma and decompression illness of the inner ear: 46 cases during treatment and follow-up. Otol Neurotol 2007; 28: 447–54</ref>
*Middle-ear barotrauma: Conductive hearing loss seen
*Both inner-ear and middle-ear barotrauma are usually preceded by difficulty in equalizing middle-ear pressure
*Alternobaric vertigo: transient vertigo during compression or decompression arises because of asymmetric middle-ear pressure equilibration <ref>Farmer JC Jr. Diving injuries to the inner ear. Ann Otol Rhinol Laryngol Suppl 1977; 86 (1 Pt 3 suppl 36): 1–20</ref>
 
|-
 
| style="background:#DCDCDC;" align="center" | Middle-ear or maxillary sinus overinflation
 
|
*It is caused by gas expansion during ascent and an obstructed eustachian tube or sinus ostium
*Compresses the facial nerve causes unilateral upper and lower facial weakness, <ref>Molvaer OI, Eidsvik S. Facial baroparesis: a review. Undersea Biomed Res 1987; 14: 277–95</ref> or
*Compression of branches of the trigeminal nerve causes hypoaesthesia of the face <ref name="DCS Butler">Butler FK, Bove AA. Infraorbital hypesthesia after maxillary sinus barotrauma. Undersea Hyperb Med 1999; 26: 257–59</ref>
|-
 
| style="background:#DCDCDC;" align="center" | Contaminated diving gas and oxygen toxic effects
 
|
*Carbon monoxide poisoning: contaminated breathing gas can cause encephalopathy and convulsions.
*Oxygen toxicity: most common in divers using enriched oxygen breathing mixtures; and can cause convulsions at depth.
 
|-
 
| style="background:#DCDCDC;" align="center" | Musculoskeletal strains or trauma sustained <ref name="DCS Butler">Butler FK, Bove AA. Infraorbital hypesthesia after maxillary sinus barotrauma. Undersea Hyperb Med 1999; 26: 257–59</ref>
 
|
*Time of onset (e.g.: before, during, or after diving) and history of trauma or strain are helpful to rule it out.
*Pain is usually accompanied by tenderness or position-related or motion-related exacerbation on physical examination.
 
|-
 
| style="background:#DCDCDC;" align="center" | Seafood toxin ingestion
 
|
*Ingestion of toxins (e.g.: ciguatera, puffer fish, paralytic shellfish poisoning )
*Often associated with gastrointestinal symptoms, and can cause neurological manifestations within hours after ingestion <ref>Eastaugh J, Shepherd S. Infectious and toxic syndromes from fi sh and shellfi sh consumption. A review. Arch Intern Med 1989; 149: 1735–40</ref>
|-
 
| style="background:#DCDCDC;" align="center" | Immersion pulmonary edema


{{SI}}
|
*This disorder usually begins during descent or at depth, whereas the onset of cardiorespiratory DCS occurs after the dive
*They might get confused since both cause dyspnea and cough <ref>Adir Y, Shupak A, Gil A, Peled N, et al. Swimming-induced pulmonary edema: clinical presentation and serial lung function. Chest 2004; 126: 394–99</ref>
 
|-
 
| style="background:#DCDCDC;" align="center" | Water aspiration
 
|
*Water aspiration could be mistaken for cardiorespiratory DCS
*Both can cause pulmonary edema, although the diver is usually aware of aspiration
 
|-
 
| style="background:#DCDCDC;" align="center" | Coincidental, unrelated acute neurological disorder 
 
|
*Diagnosis of stroke, hypothermia, hypoglycemia, and spinal hematoma is made with conventional techniques
 
|-
 
| style="background:#DCDCDC;" align="center" | Thermal stress
 
|
*Usually occur due to cold exposure but sometimes excessive heat can be responsible
 
|}
 
==Epidemiology and Demographics==
 
*The incidence of DCS, fortunately, is rare.
*Recreational divers: It is estimated in about 2 to 4/10,000 dives.
*Commercial divers: It can be higher ranging from 1.5-10 per 10,000 dives due to prior history of minor musculoskeletal injuries.
*Its prevalence depends on the length and depth of the dive.
*The risk for DCS is 2.5 times greater for males in relation to females. <ref name="PollockButeau2017">{{cite journal|last1=Pollock|first1=Neal W.|last2=Buteau|first2=Dominique|title=Updates in Decompression Illness|journal=Emergency Medicine Clinics of North America|volume=35|issue=2|year=2017|pages=301–319|issn=07338627|doi=10.1016/j.emc.2016.12.002}}</ref>
 
==Risk Factors==
*Various environmental, diving and individual factors are related to the predisposition of DCS.
* In 2005, DeNoble et al conducted a study to find the association of various risk factors with the DCS<ref>DeNoble, PJ; Vann, RD; Pollock, NW; Uguccioni, DM; Freiberger, JJ; Pieper, CF (2005). "A case-control study of decompression sickness (DCS) and arterial gas embolism (AGE)". Undersea and Hyperbaric Medical Society</ref>
**''Multiple risk factors studied'': age, gender, body mass index, smoking, asthma, diabetes, cardiovascular disease, previous history of DCI, number of the years since certification, number of dives in the last year, number of diving days, number of dives in a repetitive series, last dive depth, nitrox use, and drysuit use.
**''No significant correlation'' with DCS: asthma, diabetes, cardiovascular disease, smoking, or body mass index.
**''Positive correlation'' (higher risk): increased diving depth, previous DCS episodes, multiple consecutive days of diving and being male.
**''Negative correlation'' (lower risk): nitrox and drysuit use, higher frequency of diving in the past year, increasing age, and years since certification possibly as indicators of more extensive training and experience.
 
===Environmental factors===
*'''Magnitude of the pressure reduction ratio''': DCS is more likely to be experienced with a larger pressure reduction ratio in comparison to a smaller reduction. <ref name="DCS Dehart">{{cite book | last = DeHart | first = Roy | title = Fundamentals of aerospace medicine | publisher = Lippincott Williams & Wilkins | location = Philadelphia | year = 2002 | isbn = 978-0-7817-2898-0 }} </ref>
*'''Temperature''': Warm conditions may favor nitrogen uptake which results in an increased level of dissolved nitrogen and hence, putting a diver at higher risk of “out gassing” during ascent phase. Contrarily, the cold conditions slows the process; however, no definitive studies have demonstrated a direct relationship between thermal conditions and development of DCS. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
*'''Repetitive exposures''': A shorter periods of break among similar repetitive dives and ascents to altitudes above 5,500 metres (18,000 ft) will raise the risk of DCS because excessive nitrogen remains dissolved in body tissues for at least 12 hours after each dive, and hence, repeated dives within 1 day predisposes the divers to it.<ref name="DCS Dehart">{{cite book | last = DeHart | first = Roy | title = Fundamentals of aerospace medicine | publisher = Lippincott Williams & Wilkins | location = Philadelphia | year = 2002 | isbn = 978-0-7817-2898-0 }} </ref>
*'''Post dive air travel''': Divers who ascend to altitude soon after a dive increase their possibility of developing DCS even if the dive was performed within the dive table safe limits. <ref name="DCS Baset"> Bassett, Bruce E (1982). "Decompression Procedures for Flying After Diving, and Diving at Altitudes above Sea Level". US Air Force School of Aerospace Medicine Technical Report. SAM-TR-82-47</ref>
*'''Diving before travelling to altitude''': DCS can occur even without flying if a diver moves to a high-altitude location on land immediately after diving; for example, scuba divers in Eritrea who drive from the coast to the Asmara plateau at 2,400 m (7,900 ft) increase their chances of DCS. <ref name="DCS Lipman">{{cite book | last = Lippmann | first = John | title = Deeper into diving : an in-depth review of decompression procedures, and of the physical and physiological aspects of deeper diving | publisher = J.L. Publications | location = Melbourne Australia | year = 2005 | isbn = 978-0-9752290-1-9 }} </ref>
*'''Ambient temperature''': A very cold ambient temperatures may increase the risk of altitude DCS. However, increasing ambient temperature during decompression following the dives in cold water may reduce the risk levels. <ref name="DCS Fryere">{{cite book | last = Fryer | first = David | title = Subatmospheric decompression sickness in man | publisher = Technical P | location = London | year = 1969 | isbn = 978-0-85102-023-5 }}</ref> <ref>Gerth, Wayne A; Ruterbusch, VL; Long, Edward T (2007). "The Influence of Thermal Exposure on Diver Susceptibility to Decompression Sickness". United States Navy Experimental Diving Unit Technical Report. NEDU-TR-06-07</ref>
 
===Diving factors===
*'''Rate of ascent''': A rate of ascent shows a positive correlation with faster the ascent, greater the risk. The U.S. Navy Diving Manual indicates that ascent rates greater than about 20 m/min (66 ft/min) from the diving depth increases the possibility of DCS, while other recreational dive tables such as the Bühlmann tables require an ascent rate of 10 m/min (33 ft/min) with the last 6 m (20 ft) taking at least one minute to lower its incidence. A diver exposed to a rapid decompression rate of ascent of above 5,500 metres (18,000 ft) has a greater risk of altitude DCS in comparison to being exposed to the same altitude but at a lower rate of ascent. <ref name="DCS Dehart">{{cite book | last = DeHart | first = Roy | title = Fundamentals of aerospace medicine | publisher = Lippincott Williams & Wilkins | location = Philadelphia | year = 2002 | isbn = 978-0-7817-2898-0 }} </ref> <ref name="DCS Lipman">{{cite book | last = Lippmann | first = John | title = Deeper into diving : an in-depth review of decompression procedures, and of the physical and physiological aspects of deeper diving | publisher = J.L. Publications | location = Melbourne Australia | year = 2005 | isbn = 978-0-9752290-1-9 }} </ref>
*'''Duration of diving''': A longer duration of the dive, the greater risk of DCS. Similarly, a longer flights, especially to altitudes of 5,500 m (18,000 ft) and above, holds a higher risk of altitude DCS. <ref name="DCS Dehart">{{cite book | last = DeHart | first = Roy | title = Fundamentals of aerospace medicine | publisher = Lippincott Williams & Wilkins | location = Philadelphia | year = 2002 | isbn = 978-0-7817-2898-0 }} </ref>
*'''Diving at altitude''': Diving in water whose surface altitude is above 300 m (980 ft) have a higher risk of developing DCS; for example, Lake Titicaca is at 3,800 m (12,500 ft) and diving in it without using versions of decompression tables or dive computers that are modified for high-altitude predisposes the divers to DCS. <ref name="DCS Baset"> Bassett, Bruce E (1982). "Decompression Procedures for Flying After Diving, and Diving at Altitudes above Sea Level". US Air Force School of Aerospace Medicine Technical Report. SAM-TR-82-47</ref>
 
===Individual factors===
*'''[[Dehydration]]''': Drinking isotonic saline or adequate hydration will raise the serum surface tension which is helpful in controlling bubble size and hence, reduces the chances of DCS in aviators. Therefore, maintaining adequate hydration is recommended. <ref name="DCS Lipman">{{cite book | last = Lippmann | first = John | title = Deeper into diving : an in-depth review of decompression procedures, and of the physical and physiological aspects of deeper diving | publisher = J.L. Publications | location = Melbourne Australia | year = 2005 | isbn = 978-0-9752290-1-9 }} </ref> <ref name="DCS Fryere">{{cite book | last = Fryer | first = David | title = Subatmospheric decompression sickness in man | publisher = Technical P | location = London | year = 1969 | isbn = 978-0-85102-023-5 }}</ref>
*'''Patent foramen ovale (PFO)''': At birth, a hole between the atrial chambers of the heart in the fetus gets normally closed by a flap with the first breath. However, in about 20% of adults, where the flap does not seal completely, allows blood through the hole during coughing or activities that raise chest pressure. During diving, PFO can allow venous blood with microbubbles of inert gas to bypass the lungs, where the bubbles would otherwise be filtered out by the lung capillary system, and return directly to the arterial system (including arteries to the brain, spinal cord and heart). In the arterial system, bubbles are highly dangerous because they block circulation and cause infarction. In the brain, infarction results in stroke; whereas in the spinal cord, it may predispose to paralysis. <ref name="DCS Lipman">{{cite book | last = Lippmann | first = John | title = Deeper into diving : an in-depth review of decompression procedures, and of the physical and physiological aspects of deeper diving | publisher = J.L. Publications | location = Melbourne Australia | year = 2005 | isbn = 978-0-9752290-1-9 }} </ref> <ref>Moon, Richard E; Kisslo, Joseph (1998). "PFO and decompression illness: An update". South Pacific Underwater Medicine Society Journal. 28 (3). ISSN 0813-1988. OCLC 16986801 </ref>
*'''Age''': An increasing age (especially >42 years of age) has been associated with a higher incidence of altitude DCS. <ref name="DCS Fryere">{{cite book | last = Fryer | first = David | title = Subatmospheric decompression sickness in man | publisher = Technical P | location = London | year = 1969 | isbn = 978-0-85102-023-5 }}</ref>
*'''Previous injury''': Divers with a previous history of recent joint or limb injuries may have a higher susceptibility to development of the decompression-related bubbles. <ref> Karlsson, L; Linnarson, D; Gennser, M; Blogg, SL; Lindholm, Peter (2007). "A case of high doppler scores during altitude decompression in a subject with a fractured arm". Undersea and Hyperbaric Medicine. 34 (Supplement). ISSN 1066-2936. OCLC 26915585 </ref>
*'''Body type''': A diver with a high body fat content stores about the half the total amount of the nitrogen which predisposes them to a higher chances of DCS. This is due to five times greater solubility of nitrogen in fat than water, and hence, resulting in a higher levels of total body dissolved nitrogen during elevated atmospheric pressure. <ref name="DCS Fryere">{{cite book | last = Fryer | first = David | title = Subatmospheric decompression sickness in man | publisher = Technical P | location = London | year = 1969 | isbn = 978-0-85102-023-5 }}</ref> <ref name="BoycottDamant2009">{{cite journal|last1=Boycott|first1=A. E.|last2=Damant|first2=G. C. C.|title=Experiments on the Influence of Fatness on Susceptibility to Caisson Disease|journal=Epidemiology and Infection|volume=8|issue=4|year=2009|pages=445–456|issn=0950-2688|doi=10.1017/S0022172400015862}}</ref>
*'''Alcohol consumption''': It increases chances of dehydration and inhibits pituitary release of antidiuretic hormone (ADH); and therefore may increase susceptibility to DCS. <ref name="DCS Fryere">{{cite book | last = Fryer | first = David | title = Subatmospheric decompression sickness in man | publisher = Technical P | location = London | year = 1969 | isbn = 978-0-85102-023-5 }}</ref> Contrarily, another study found no correlation between alcohol consumption and developing DCS. <ref>{{cite journal|title=RSA Abstracts|journal=Alcoholism: Clinical and Experimental Research|volume=29|year=2005|pages=6A–172A|issn=01456008|doi=10.1111/j.1530-0277.2005.tb03524.x}}</ref>
*'''Work and exercise''':  DCS is strongly related with the level of work or exercise done at depth or shortly after diving because it promotes increased inert gas uptake. Therefore, any kind of strenuous exercise will promote bubble formation, and lighter exercise during ascent or stop phase will favor gas excretion. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
*'''[[Asthma]]''': Asthmatics are generally advised not to dive due to a theoretical risk of bronchospasm triggered by cold or changing environments, inability to have an immediate response to an asthma attack while being submerged, and supposed increased barotrauma during ascent. However, more studies are warranted as there is limited data to support preventing them from diving. Well-controlled asthmatics with normal PFTs can occasionally be permitted to dive, however, an assessment should be made on a case-by-case basis. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
==Diagnosis==
*DCS is primarily a clinical diagnosis assessed with a thorough and detailed dive history from a conscious patient and the clinical examination, including the neurological exam.
*The specific symptoms/signs and their particular time of onset (table 3 and 4) aid in suspecting and establishing the diagnosis.
*However, the relief of symptoms by recompression will make the definitive confirmation of the probable diagnosis.
*Hence, an immediate treatment should be begun with no delay for further diagnostic work up.
 
===Diagnostic criteria===
In 2004 Freiberger identified important five diagnostic factors in their order of importance using simulated diving injury cases:<ref>Freiberger JJ, Lyman SJ, Denoble PJ, et al. Consensus factors used by experts in the diagnosis of decompression illness. Aviat Space Environ Med 2004;75(12): 1023–8 </ref>
*(1) A neurologic symptom as the primary presenting symptom,
*(2) onset time to symptoms,
*(3) joint pain as a presenting symptom,
*(4) any relief after recompression treatment, and
*(5) maximum depth of the last dive
 
===Laboratory findings===
*DCS is associated with hemoconcentration, and elevated serum CK is seen in severe AGE.
*However, none of the laboratory studies make a definitive diagnosis of DCS. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
===Radiological findings===
*No imaging study can confirm the diagnosis of DCS.
*''Bubble formation'' can occasionally be identified on MRI or CT scans; however, they are not considered the reliable method to rule out DCS due to their low sensitivity level in making the diagnosis.
*Although, they might be used to rule out the other differential disorders that presents with the similar signs and symptoms (eg, herniated intervertebral disk, ischemic stroke, central nervous system hemorrhage).
*These studies should be performed with no delay as prompt intervention is important in the successful management of the DCS.
 
====Chest and Joints Radiography====
*Pneumothorax, pneumomediastinum, pulmonary overexpansion injury, or pulmonary edema should always be ruled out with chest radiographs.
*Radiographs rarely detect ''bubble formation'' in joints affected by pain.
*Skeletal x-rays are not considered diagnostic for dysbaric osteonecrosis which may show joint degeneration; and hence cannot be used to differentiate between different joint disorders. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref> <ref name="DCS Richard">Richard D Vann, Frank K Butler, Simon J Mitchell, Richard E Moon. Decompression illness. Vol 377 January 8, 2011; pg: 153-164 </ref>
 
====Computed Tomography Scan====
*'''''Head CT''''': A “normal” head CT is not reliable in excluding DCS due to the very low chances of visibility of ''vascular gas bubbles'' on CT films in the cases of suspected DCS. However, it should be strongly considered in any patient who presented with an altered mental status in order to evaluate alternative diagnoses, such as subdural or epidural hematoma. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref> <ref>Benson J, Adkinson C, Collier R. Hyperbaric oxygen therapy of iatrogenic cerebral arterial gas embolism. Undersea Hyperb Med 2003; 30: 117–26</ref>
 
*'''''Chest CT''''': An extrapulmonary air can be detected on it, but it should be avoided due to its high radiation exposure level. <ref name="DCS Richard">Richard D Vann, Frank K Butler, Simon J Mitchell, Richard E Moon. Decompression illness. Vol 377 January 8, 2011; pg: 153-164 </ref>
 
====Magnetic Resonance Imaging====
*MRI can be falsely reassuring for detecting the spinal cord or brain abnormalities related to DCS.
*However, it can diagnose ischemic lesions of the brain or spinal cord due to the etiologies other than DCS. <ref>Gempp E, Blatteau JE, Stephant E, Pontier JM, Constantin P, Peny C. MRI fi ndings and clinical outcome in 45 divers with spinal cord decompression sickness. Aviat Space Environ Med 2008; 79: 1112–16</ref>
 
===Other diagnostic studies===
*'''''Doppler ultrasonography''''' and '''''Echocardiography''''': They are not considered the diagnostic tests for DCS; but done to rule out right to left shunt and for research purposes into venous gas emboli. <ref>Gempp E, Blatteau JE, Pontier JM, Balestra C, Louge P. Preventive eff ect of pre-dive hydration on bubble formation in divers. Br J Sports Med 2009; 43: 224–28</ref>
*'''''Neurophysiological tests''''' (eg, audiometry and electronystagmography for inner-ear decompression sickness): They can usually be delayed until after recompression. <ref name="DCS Richard">Richard D Vann, Frank K Butler, Simon J Mitchell, Richard E Moon. Decompression illness. Vol 377 January 8, 2011; pg: 153-164 </ref>
 
*'''''Non invasive pulmonary diagnostic test''''': None of them are used in making or excluding the diagnosis. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
*'''''Pulmonary diagnostic procedures (e.g.: Bronchoscopy)''''': None is required in making or excluding the diagnosis. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
*'''''Pathology/Cytology/Genetics Study''''': None is considered in making or excluding the diagnosis. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
Although laboratory and radiological analyses are helpful for detection of DCS related abnormalities in some cases; however, these studies are not considered as the deciding factor for the start of the recompression therapy, and hence, recompression should be given with no delay unless there is a strong suspicion of other non-diving related etiologies (eg, cerebral hemorrhage). <ref name="DCS Richard">Richard D Vann, Frank K Butler, Simon J Mitchell, Richard E Moon. Decompression illness. Vol 377 January 8, 2011; pg: 153-164 </ref>
 
==Treatment==
The several elements to the effective management of DCS consist of initial treatment including on-the-scene evaluation and first aid; transportation; and definitive medical treatment.
 
===On the scene first aid===
*The foundation of first aid is the basic life support.
*An initial management should focus on the treatment and stabilization of ABC's (airway, breathing, and circulation) in the patients with an altered mental status or loss of consciouness.
*All DCS suspected cases should have initial treatment with high flow oxygen at 15ltr/min via a non-rebreathe mask or pocket masks regardless of their oxygen saturation levels.
*This high-flow 100% oxygen enhances nitrogen washout by widening the nitrogen pressure gradient between the lungs and the circulation, thus accelerating reabsorption of embolic bubbles. <ref name="urlDecompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition">{{cite web |url=https://www.msdmanuals.com/professional/injuries-poisoning/injury-during-diving-or-work-in-compressed-air/decompression-sickness |title=Decompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition |format= |work= |accessdate=}}</ref>
*An early ''oxygen first aid'' is important and may reduce symptoms substantially, but this should not change the recommended treatment plan.
*However, an initial oxygen breathing may clears the symptoms of air embolism and serious DCS, but they may reappear later due to which always contact DAN at +1-919-684-9111 or a dive physician in all the cases of suspected DCI, even if the symptoms and signs appear to have resolved. <ref name="urlwww.diversalertnetwork.org">{{cite web |url=https://www.diversalertnetwork.org/health/decompression/Signs-and-symptoms-of-DCS |title=www.diversalertnetwork.org |format= |work= |accessdate=}}</ref>
 
{{familytree/start |summary=Sample 1}}
{{familytree | | | | | | | | A01 | | | | |A01=Decompression sickness}}
{{familytree | | | | |,|-|-|-|^|-|-|-|-|.| | | }}
{{familytree | | | B01 | | | | | | | | B02 | | |B01=Mild Symptoms: <br>•Inhalation of oxygen with FiO2 1.0; <br>•Fluid administration (i.v. if possible,otherwise oral in unconscious patient) |B02=Severe Symptoms with pain, neurological and/or pulmonary impairment}}
{{familytree | | | |!| | | | | | | | | |!| }}
{{familytree | | | C01 | | | | | | | |C02| |C01=Complete relief of symptoms within 30 minutes|C02= Emergency treatment: <br>•Flat supine position; <br>•CPR if necessary; <br>•Insufflation of 100% inspired Oxygen; <br>•Intubation when unconscious; <br>•Intravenous line; <br>•Infusion therapy; <br>•HBOT as soon as possible}}
{{familytree |,|-|-|^|.| | | | | | | | |!| | }}
{{familytree |!| | | |D01|-|-|-|-|-|D02| | |D01=If no|D02=Hyperbaric Oxygen Therapy: <br>•Treatment protocol most widespread: Table 6 USN; <br>•When intubated: paracentesis recommended; <br>•Lung ventilated at both sides?; <br>•Pneumothorax?}}
{{familytree |E01| | | | | | |,|-|-|-|^|-|-|.| | | |E01=If yes|}}
{{familytree | |!| | | | | | |F01| | | | | |F02|F01=Further drug therapy (scientifically not finally proven); <br>•Corticosteroids, Aspirin, Lidocaine|F02=Further measures: <br>•Foley catheters; <br>•Renal protection; <br>•Early rehabilitation measures; <br>•Physiotherapeutic excercise between treatments}}
{{familytree | |G01| | | | | | | | | | | | | |G01=Hospitalisation for 24h}}
{{familytree/end}}
'''''Figure 1: Treatment algorithm of Decompression Sickness (DCS)'''''<ref name="TetzlaffShank2003">{{cite journal|last1=Tetzlaff|first1=Kay|last2=Shank|first2=Erik S.|last3=Muth|first3=Claus M.|title=Evaluation and management of decompression illness—an intensivist’s perspective|journal=Intensive Care Medicine|volume=29|issue=12|year=2003|pages=2128–2136|issn=0342-4642|doi=10.1007/s00134-003-1999-1}}</ref>
 
===Fluid administration===
*It is indicated to minimize the dehydration and restore lost intravascular volume.
*Oral resuscitation fluid (or plain water) is indicated for alert patients with mild manifestations.
*Isotonic IV fluid resuscitation and maintenance IV fluids should be administered to those with serious manifestations in order to counteract interstitial fluid shifts and decrease in plasma volume arising from an endothelial injury.
*Insert a catheter if there is any suspicion of the patient having urinary retention. <ref name="urlDecompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition">{{cite web |url=https://www.msdmanuals.com/professional/injuries-poisoning/injury-during-diving-or-work-in-compressed-air/decompression-sickness |title=Decompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition |format= |work= |accessdate=}}</ref>
 
===Positioning and transportation===
*The supine position or the recovery position should be preferred in case vomiting occurs.
*The Trendelenburg position and the left lateral decubitus position (Durant's maneuver) have beneficial effect in cases where air emboli are suspected; however, these positions are no longer recommended for prolonged duration due to concerns regarding cerebral edema. <ref name="urlDecompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf">{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK537264/ |title=Decompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf |format= |work= |accessdate=}}</ref>
*It is essential that the suspected cases should be stabilized at the nearest medical center before transportation to a recompression chamber.
*However, patients with severe symptoms need an evacuation to a suitable recompression facility because time to treatment and severity of the injury are important determinants of outcome; and hence, transport should not be delayed for the performance of nonessential procedures. 
 
'''''Aeromedical transport''''':
*Instructions to fly the patient “as low as safely possible” should be given to helicopter transport.
*Pressurized aircraft with 1 atmosphere internal pressure is preferred. 
*Unpressurized aircraft such as helicopters: The flight altitude should be limited to 300 m or 1000 ft if possible, and oxygen should be given continuously. <ref name="PollockButeau2017">{{cite journal|last1=Pollock|first1=Neal W.|last2=Buteau|first2=Dominique|title=Updates in Decompression Illness|journal=Emergency Medicine Clinics of North America|volume=35|issue=2|year=2017|pages=301–319|issn=07338627|doi=10.1016/j.emc.2016.12.002}}</ref> 
*Commercial aircraft, although pressurized, typically have a cabin pressure equivalent to 2438 m (8000 ft) at normal cruise altitude, but it may precipitate DCS symptoms. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref> <ref name="urlDecompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition">{{cite web |url=https://www.msdmanuals.com/professional/injuries-poisoning/injury-during-diving-or-work-in-compressed-air/decompression-sickness |title=Decompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition |format= |work= |accessdate=}}</ref>
 
===Definitive treatment===
 
====Hyperbaric Oxygen Therapy (HBOT)====
*The definitive treatment is hyperbaric oxygen (HBOT) therapy which delivers the pure 100% oxygen at a pressure substantially higher than that of atmospheric pressure in recompression chambers.
*Delays of > 4 hours from the time of injury to recompression correlate with a significant increase in the incidence of residual symptoms following therapy and hence, it should be initiated as soon as possible. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
=====Indication=====
*All the patients, except those whose symptoms are limited to itching, skin mottling, and fatigue, may be treated with oxygen therapy alone; however these patients should be observed for any kind of further deteriorating condition. <ref name="urlDecompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition">{{cite web |url=https://www.msdmanuals.com/professional/injuries-poisoning/injury-during-diving-or-work-in-compressed-air/decompression-sickness |title=Decompression Sickness - Injuries; Poisoning - MSD Manual Professional Edition |format= |work= |accessdate=}}</ref>
 
=====Effects of Recompression therapy=====
*Bubble crushing: As per Boyles law, increasing pressure decreases the volume of bubbles.
*Flushing out the nitrogen bubbles with oxygen delivery by improving gradient.
*Healing damaged tissue with hyperbaric oxygen <ref name="urlDecompression Illness - RCEMLearning">{{cite web |url=https://www.rcemlearning.co.uk/reference/decompression-illness/#1567502920236-96a835e2-60e9 |title=Decompression Illness - RCEMLearning |format= |work= |accessdate=}}</ref>
 
=====Equipment=====
*Monoplace chamber: An acrylic tube sized chamber which have a capacity of one patient
*Multiplace chamber: It is sized to accommodate one or more patients with one or more technicians or other medical personnel. They are designed to allow patients, tenders or equipment to be transferred into and out of the chamber while treatment is ongoing. <ref name="urlwww.diversalertnetwork.org">{{cite web |url=https://www.diversalertnetwork.org/health/decompression/Signs-and-symptoms-of-DCS |title=www.diversalertnetwork.org |format= |work= |accessdate=}}</ref> <ref>Kindwall, EP; Goldmann, RW; Thombs, PA (1988). "Use of the Monoplace vs. Multiplace Chamber in the Treatment of Diving Diseases". Journal of Hyperbaric Medicine; 3(1). Undersea and Hyperbaric Medical Society, Inc. pp. 5–10</ref>
 
=====Regimen=====
*A common HBOT regimen: The U.S. Navy Treatment Table 6 (USN 2008).
*Regimen protocol:
**HBOT chamber is brought to 2.8 atmospheres absolute (ATA), (equivalent of depth of 60 feet/18 meters) over a few minutes; and
**Then 100% FiO2 is initiated.
**100% FiO2 is used for 20 minutes at a time, alternating with 5 minute intervals of room air breathing to reduce the risk of oxygen toxicity.
**Upon completion, the pressure is increased by no more than 1 foot/minute, with a prolonged period of equilibration at 30 feet.
**The total therapy time is about 5 hours.
**The therapy can be continued daily for several days until no further improvement is seen in the patient's symptoms. <ref name="urlwww.diversalertnetwork.org">{{cite web |url=https://www.diversalertnetwork.org/health/decompression/Signs-and-symptoms-of-DCS |title=www.diversalertnetwork.org |format= |work= |accessdate=}}</ref> <ref name="DCS manual">U.S. Navy Supervisor of Diving (2008). "Chapter 20: Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism". U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. volume 5. U.S. Naval Sea Systems Command. p. 41</ref>
 
=====Mechanism of action=====
*The mechanism of HBOT is twofold.
**An elevated atmospheric pressure in the chamber increases the partial pressure of gases and dissolution of nitrogen back into liquid (Henry’s law), and the increased pressure also decreases the volume of gas present in the body (Boyle’s law).
**An increased FiO2 results in decreased partial pressure of nitrogen in inspired gas. This enhances the diffusion gradient of nitrogen out of body tissues, favoring exhalation and elimination from the body, and blunting the neutrophillic response to injured endothelium. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
 
=====Risks=====
<ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref> <ref name="HeyboerSharma2017">{{cite journal|last1=Heyboer|first1=Marvin|last2=Sharma|first2=Deepali|last3=Santiago|first3=William|last4=McCulloch|first4=Norman|title=Hyperbaric Oxygen Therapy: Side Effects Defined and Quantified|journal=Advances in Wound Care|volume=6|issue=6|year=2017|pages=210–224|issn=2162-1918|doi=10.1089/wound.2016.0718}}</ref>
*'''Barotrauma''':
**Middle ear barotrauma: most common adverse effect of HBOT; generally requires supportive care. Bilateral tympanostomy tubes may be required in severe cases.
**Pulmonary barotrauma: risk of pneumothorax; chest tube can be inserted.
**Pneumomediastinum: managed conservatively.
**Similar mechanism and management as barotrauma caused by diving.
*'''Oxygen toxicity''':
**Pulmonary toxicity: small airways dysfunction observed on exceeding the treatment duration and pressure beyond the recommended therapeutic protocols.
**CNS toxicity: generalized tonic-clonic seizures occur with an incidence of approximately 1-4 per 10,000 patient treatments. Risk is higher in patients who are hypercapnic, acidemia and/or septic.
*'''Seizures''': mechanisms not well-understood.
**CNS toxicity: managed by decreased FiO2 with same elevated atmospheric pressure.
**Ocular toxicity: myopia can be seen in those who undergo prolonged daily therapy.
*'''Confinement anxiety''': Managed with anxiolytics.
*'''Fire''': due to elevated FiO2.
 
====In-water recompression (IWR) therapy====
*It is beneficial only with a substantial amount of planning, support, equipment and personnel; appropriate water conditions; and suitable patient status.
*Critical challenges can arise from the changes in the patient's consciousness, oxygen toxicity, gas supply, and even thermal stress.
*An unsuccessful IWR may leave the patient in worse shape than had the attempt not been made.
*Hence, it would be suitable for an organized and disciplined group of divers with suitable equipment and practical training in the procedure. <ref name="urlDecompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf">{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK537264/ |title=Decompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf |format= |work= |accessdate=}}</ref> <ref name="urlwww.diversalertnetwork.org">{{cite web |url=https://www.diversalertnetwork.org/health/decompression/Signs-and-symptoms-of-DCS |title=www.diversalertnetwork.org |format= |work= |accessdate=}}</ref>
 
[[Image:Oxymask.JPG|right|thumb|145px|Breathing pure oxygen to remove nitrogen from the bloodstream]]
 
====Adjuvant treatment====
*Aspirin, NSAIDs, and corticosteroids have all been studied and shown no beneficial use in the management of DCS. However, they may mask the symptoms and exacerbate micro-haemorrhages caused by DCS resulting in a permanent sequelae.
*Opiates should also be avoided as they can increase the risk of oxygen toxicity.
*Oxygen is usually sufficient to control pain. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref> <ref name="urlDecompression Illness - RCEMLearning">{{cite web |url=https://www.rcemlearning.co.uk/reference/decompression-illness/#1567502920236-96a835e2-60e9 |title=Decompression Illness - RCEMLearning |format= |work= |accessdate=}}</ref>
 
====Follow-up evaluation and return to diving====
*Follow-up treatments along with physical therapy is required in the severe cases where significant residual neurological dysfunction may be present even after the most aggressive treatment.
 
*Clearing a diver after DCS to return to diving is a complex undertaking with potential medical and legal risks. A careful risk and benefit assessment to ensure that the diver is completely asymptomatic and back to his or her pre-dive baseline function must be conducted by both the diver and the physician. A referral of the patient to a diving medicine specialist is appropriate in case of improperly clearing a diver to return to diving keeping in mind the potential life-threatening implications. Divers should be instructed to refrain from diving for the remainder of their lives in the cases where the risks clearly outweigh the benefits. Furthermore, a diver who has had multiple bouts of DCS even if symptoms were not severe and resolves completely must take special considerations. In such cases, a Diving Medical Specialist must be consulted to determine if diving can be resumed safely.
 
*The physician must also consider when it is safe for a patient to fly home or drive at altitude. A retrospective review of 126 DCS cases demonstrated that those who flew home on commercial flights < 72 hours after recompression had a higher likelihood of recurrence of symptoms and signs of DCS. Similarly, physicians should be wary if patients must drive through high-altitude areas, as the drop in atmospheric pressure could, at least theoretically, potentiate a recurrence. <ref name="urlwww.pulmonologyadvisor.com">{{cite web |url=https://www.pulmonologyadvisor.com/home/decision-support-in-medicine/pulmonary-medicine/diving-medicine-and-medical-complications-of-diving-dcs-and-barotrauma/ |title=www.pulmonologyadvisor.com |format= |work= |accessdate=}}</ref>
*The US Navy has recommended the guidelines for returning to diving after treatment with limited time off for the professional divers as their operations should not get compromised; whereas diving is not a livelihood for the recreational divers, so a more conservative approach should be adopted to further minimize the chance for the recurrence of a diving injury. <ref name="DCS dan"> {{cite web |url=https://www.diversalertnetwork.org/medical/articles/Decompression_Illness_What_Is_It_and_What_Is_The_Treatment |title=Decompression Illness: What Is It and What Is The Treatment? — DAN &#124; Divers Alert Network — Medical Dive Article |format= |work= |accessdate=}} </ref>
 
'''''Table 6 elaborate the recommendations given by the US Navy for return to diving:'''''
 
{| class="wikitable" style="text-align:center"
 
|-
 
! style="background:#4479BA; color: #FFFFFF;" | Clinical features
 
! style="background:#4479BA; color: #FFFFFF;" | Professional Divers
 
! style="background:#4479BA; color: #FFFFFF;" | Recreational divers
 
|-
 
| style="background:#DCDCDC;" align="center" | Pain-only DCI with no neurological symptoms
 
| May resume diving two to seven days after treatment
 
|A minimum of two weeks without diving is recommended
 
|-
 
| style="background:#DCDCDC;" align="center" | Minor neurological symptoms
 
| May resume diving two to four weeks after treatment depending on symptom severity
 
| Six weeks without diving is recommended
 
|-
 
| style="background:#DCDCDC;" align="center" | Severe neurological symptoms or any residual symptoms
 
|  Must be reevaluated three months after treatment and get clearance from a Diving Medical Officer
 
| No further diving is recommended
 
|}


{{EH}}
==Prognosis==
Prognosis is severity dependent. It also depends upon on other factors such as the time to recompression, availability and time to surface oxygen, previous episode, and supportive care. <ref name="urlDecompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf">{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK537264/ |title=Decompression Sickness (DCS, Bends, Caisson Disease) - StatPearls - NCBI Bookshelf |format= |work= |accessdate=}}</ref>


'''''Synonyms and keywords:''''' decompression illness, DCS, the diver's disease, the bends, caisson disease
==Prevention==
*Avoided by limiting the depth and duration of dives to a range that does not need decompression stops during ascent (called no-stop limits) or by ascending with decompression stops as specified in published guidelines (eg, the decompression table in the US Navy Diving Manual). <ref name="DCS manual">U.S. Navy Supervisor of Diving (2008). "Chapter 20: Diagnosis and Treatment of Decompression Sickness and Arterial Gas Embolism". U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010, revision 6. volume 5. U.S. Naval Sea Systems Command. p. 41</ref> <ref name="DCS navy">US Navy Diving Manual Rev. 7 Change A. SS521-AG-PRO-010 / 0910-LP-115-1921. US DIVING MANUAL_REV7_ChangeA-6.6.18.pdf; Apr 2018 </ref> 


==Overview==
*Wearing a portable dive computer that continually tracks depth and time at depth and calculates a decompression schedule. Computer divers should be cautious in approaching no-decompression limits, especially when diving deeper than 100 feet (30 meters).


'''Decompression sickness''' '''(DCS)''', '''the diver’s disease''', '''the bends''', or '''caisson disease''' is the name given to a variety of symptoms suffered by a person exposed to a reduction in the [[pressure]] surrounding their body. It is a type of [[Diving hazards and precautions|diving hazard]] and [[dysbarism]].
*Making a safety stop for a few minutes at about 4.6 m (15 ft) below the surface. <ref name="DCS navy">US Navy Diving Manual Rev. 7 Change A. SS521-AG-PRO-010 / 0910-LP-115-1921. US DIVING MANUAL_REV7_ChangeA-6.6.18.pdf; Apr 2018 </ref>


==Clinical Scenarios==
*Recreational divers should dive conservatively, whether they are using dive tables or computers.  
'''Decompression sickness''' can happen in these situations:
* A diver ascends rapidly from a dive or does not carry out [[decompression stops]] after a long or deep dive.
* An unpressurized [[aircraft]] flies upwards.
* The [[cabin pressurization]] system of an aircraft fails.
* Divers flying in any aircraft shortly after diving. Pressurized aircraft are not risk-free since the cabin pressure is not maintained at sea-level pressure. Commercial aircraft cabin pressure is often maintained to about 8,000 feet above sea level.
* A worker comes out of a pressurized [[Caisson (engineering)|caisson]] or out of a [[mining|mine]], which has been pressurized to keep water out.
* An [[astronaut]] exits a space vehicle to perform a space-walk or [[extra-vehicular activity]] where the pressure in his [[spacesuit]] is lower than the pressure in the vehicle.


[[Image:Preparing for recompression.jpg|right|thumb|200px|This surfacing diver must enter a [[recompression chamber]] to avoid the bends.]]
*Experienced divers often select a table depth (versus actual depth) of 10 feet (3 meters) deeper than called for by standard procedure. This practice is highly recommended for all divers, especially when diving in cold water or under strenuous conditions. <ref name="DCS dan"> {{cite web |url=https://www.diversalertnetwork.org/medical/articles/Decompression_Illness_What_Is_It_and_What_Is_The_Treatment |title=Decompression Illness: What Is It and What Is The Treatment? — DAN &#124; Divers Alert Network — Medical Dive Article |format= |work= |accessdate=}} </ref>


These situations cause inert gases, generally [[nitrogen]], which are normally dissolved in body fluids and tissues, to come out of physical [[solution]] (''i.e.'', outgas) and form gas [[bubble]]s.
*Avoiding the risk factors noted above (deep/long dives, exercise at depth or after a dive) will decrease the chance of DCS.  


According to [[Henry's Law|Henry’s Law]], when the [[pressure]] of a [[gas]] over a [[liquid]] is decreased, the amount of gas dissolved in that liquid will also decrease. One of the best practical demonstrations of this law is offered by opening a [[soft drink]] can or bottle. When you remove the cap from the bottle, you can clearly hear gas escaping and see bubbles forming in the soda. This is [[carbon dioxide]] gas coming out of solution as a result of the pressure inside the container reducing to [[atmospheric pressure]].
====Altitude DCS: Things to remember====
* Altitude DCS is a risk every time you fly in an un-pressurized aircraft above 18,000 feet (or at a lower altitude if you scuba dive prior to the flight).
* Be familiar with the signs and symptoms of altitude DCS. Monitor all aircraft occupants, including yourself, any time you fly an unpressurized aircraft above 18,000 feet.
* Avoid unnecessary strenuous physical activity prior to flying an un-pressurized aircraft above 18,000 feet, and for 24 h after the flight.
* Even if you are flying a pressurized aircraft, altitude DCS can occur as a result of a sudden loss of cabin pressure (in-flight rapid decompression).
* Put on your [[oxygen mask]] immediately and switch the regulator to 100% oxygen.
* Begin an emergency descent and land as soon as possible. Even if the symptoms disappear during descent, you should still land and seek medical evaluation while continuing to breathe oxygen.
*If one of your symptoms is joint pain, keep the affected area still; do not try to work the pain out by moving the joint around.
* After exposure to an in-flight rapid decompression, do not fly for at least 24 h. In the meantime, stay vigilant for the possible onset of delayed symptoms or signs of altitude DCS. If you present delayed symptoms or signs of altitude DCS, seek medical attention at once.
* Keep in mind that breathing 100% oxygen during flight (ascent, en route, descent) without oxygen pre-breathing before take-off does not prevent altitude DCS.
* Do not ignore any symptoms or signs that go away during the descent. This could confirm that you are suffering altitude DCS. You should be medically evaluated from an aviation authority medical officer, aviation medical examiner (AME), military flight surgeon, or a hyperbaric medicine specialist. Be aware that a physician not specialized in aviation or hypobaric medicine may not be familiar with this type of medical problem. Therefore, be your own advocate.
* If there is any indication that you may have experienced altitude DCS, do not fly again until you are cleared to do so.
* Allow at least 24 hours to elapse between scuba diving and flying.
* Be prepared for a future emergency by finding where [[hyperbaric chamber]]s are available in your area of operations. However, keep in mind that not all of the available hyperbaric treatment facilities have personnel qualified to handle altitude DCS emergencies. To obtain information on the locations of hyperbaric treatment facilities capable of handling altitude DCS emergencies, call the Diver's Alert Network at (USA phone number) (919) 684-9111.


Similarly, nitrogen is an inert gas normally stored throughout the human body, such as tissues and fluids, in physical [[solution]]. When the body is exposed to decreased pressures, such as when flying an un-pressurized aircraft to altitude or during a [[Scuba diving|scuba]] ascent through water, the nitrogen dissolved in the body outgases. If nitrogen is forced to come out of solution too quickly, bubbles form in parts of the body causing the signs and [[symptom]]s of the "bends" which can be itching skin and [[rash]]es, [[joint]] pain, [[sensory system]] failure, [[paralysis]], and [[death]].
'''''FOR MORE INFORMATION''''': 
*Divers Alert Network: [[www.diversalertnetwork.org]] 24-hour emergency hotline, 919-684-9111
*Duke Dive Medicine: [[www.dukedivemedicine.org]] Physician-to-physician consultation, 919-684-8111
*Undersea and Hyperbaric Medical Society
*US Navy Diving Manual


An [[air embolism]], caused by other processes, can have many of the same symptoms as DCS. The two conditions are grouped together under the name [[decompression illness]] or DCI.
==Decompression sickness in popular culture==
*In the 1880s, DCS became known as ''The Bends'' because afflicted individuals characteristically arched their backs in a manner reminiscent of a then-popular women's fashion called the [[Grecian Bend]].
*A diver with DCS flying in an aircraft was part of the plot in the episode ''[[Airborne (House episode)|Airborne]]'' of [[House (TV series)|''House, M.D.'']], first aired Tuesday [[April 11]], [[2007]].
*Rock band [[Radiohead]] released an album entitled ''[[The Bends]]'', a reference to DCS.
*DCS played a part in the anime visual novel "Ever 17"
* A character in the series "Dive" by [[Gordan Korman]] experiences a case of DCS.
*In an episode of "[[Jackie Chan Adventures]]" titled Clash of the Titanics, Jackie experienced DCS.
*[[Box (comics)|Roger Bochs]], a character in the [[Marvel Comics]] series [[Alpha Flight]], experiences DCS after battling alongside the [[Avengers (comics)|Avengers]] in [[Atlantis (Marvel Comics)|Atlantis]].


==History==
==References==
{{Wikisource1911Enc|Caisson Disease}}
{{Reflist|2}}
*1841: First documented case of decompression sickness, reported by a mining engineer who observed pain and muscle cramps among [[coal miner]]s working in [[mine shaft]]s  air-pressurized to keep water out.
*1867: The submarine pioneer [[Julius H. Kroehl]] died of decompression sickness during experimental dives with the [[Sub Marine Explorer]].
*1869: An early case resulting from diving activities while wearing an [[standard diving dress|air-pumped helmet]].
*1872: [[Washington Roebling]] suffered from caisson disease while working as the chief engineer on the [[Brooklyn Bridge]]. (He took charge after his father [[John Augustus Roebling]] died of [[tetanus]].) Washington's wife Emily helped manage the construction of the bridge, after his sickness confined him to his home in [[Brooklyn]]. He battled the after-effects of the disease for the rest of his life.


==Predisposing factors==
== External links ==
*'''Magnitude of the pressure reduction''': A large pressure reduction is more likely to cause DCS than a small one. For example, the ambient pressure halves by ascending during a dive from 10 metres / 33 feet (2 bar) to the surface (1 bar), or by flying from sea level (1 bar) to an altitude of 16,000 feet / 5,000 metres (0.5 bar) in an un-pressurized aircraft. Diving and then flying shortly afterwards increases the pressure reduction as does diving at high altitude.
* [http://www.scuba-doc.com/dcsprbs.html Decompression Sickness: Prevention, Risks, Exercise, PFO, References, Links]* [http://science.howstuffworks.com/question101.htm What causes the bends?]* [http://www.livescience.com/animalworld/whale_bends_041224.html Whales Suffer From Bends]* [http://www.divernet.com/medical/qanda0200.htm UK Sport Diving Medical Committee: Bone Necrosis]* [http://www.diversalertnetwork.org/medical/articles/index.asp Divers Alert Network: diving medicine articles]* [http://www.ndc.noaa.gov/dp_forms.html Dive Tables from the NOAA]{{Consequences of external causes}}[[Category:SCUBA]][[Category:Diving medicine]][[Category:Aviation medicine]][[Category:Medical emergencies]][[cs:Dekompresní nemoc]][[da:Trykfaldssyge]][[de:Dekompressionserkrankung]][[es:Síndrome de descompresión]][[it:Malattia da decompressione]][[hu:Keszon-betegség]][[nl:Caissonziekte]][[ja:減圧症]][[pl:Choroba dekompresyjna]][[pt:Doença de descompressão]][[ru:Декомпрессионная болезнь]][[fi:Sukeltajantauti]][[sv:Tryckfallssjuka]][[uk:Кесонна хвороба]][[zh:減壓症]]{{WikiDoc Sources}}
*'''Repetitive exposures''': Repetitive dives or ascents to altitudes above 18,000 feet within a short period of time (a few hours) also increase the risk of developing altitude DCS.
*'''Rate of ascent''': The faster the ascent, the greater the risk of developing altitude DCS. An individual exposed to a rapid decompression (high rate of ascent) above 18,000 feet has a greater risk of altitude DCS than being exposed to the same altitude but at a lower rate of ascent.
*'''Time at altitude''': The longer the duration of the flight to altitudes of 18,000 feet and above, the greater the risk of altitude DCS.
*'''Age''': There are some reports indicating a higher risk of altitude DCS with increasing age.
*'''Previous injury''': There is some indication that recent joint or limb injuries may predispose individuals to developing "the bends."
*'''Ambient temperature''': There is some evidence suggesting that individual exposure to very cold ambient temperatures may increase the risk of altitude DCS.
*'''Body Type''': Typically, a person who has a high body fat content is at greater risk of altitude DCS. Due to poor blood supply, nitrogen is stored in greater amounts in fat tissues. Although fat represents only 15 percent of a normal adult body, it stores over half of the total amount of nitrogen (about 1 litre) normally dissolved in the body.
*'''Exercise''': When a person is physically active, or performing strenuous activity before or after a dive (such as rowing to and from a dive site), there is greater risk of DCS.*'''Rate of Air Consumption''': If you tend to consume more air than what may be considered "normal" for scuba diving, you will certainly be more susceptible to DCS if you skirt the no-decompression limits.*'''Alcohol consumption/dehydration''': While conventional wisdom would have one believe that the after effects of [[alcohol]] consumption increase the susceptibility to DCS through increased dehydration and decreased [[motor coordination]]/[[mental acuity]], one study concluded that alcohol consumption did not increase the risk of DCS.<ref>http://depts.washington.edu/adai/pubs/pres/LeighRSAPoster.pdf</ref>. The high surface tension of water is generally regarded as helpful in controlling bubble size, hence staying hydrated is recommended by most experts.* '''[[Patent foramen ovale]]''': A hole between the atrial chambers of the [[heart]] in the fetus is normally closed by a flap with the first breaths at birth. In up to 20 percent of adults the flap does not seal, however, allowing blood through the hole with coughing or other activities which raise chest pressure. In diving, this can allow blood with microbubbles in the venous blood from the body to return directly to the arteries (including arteries to the brain, spinal cord and heart) rather than pass through the lungs, where the bubbles would otherwise be filtered out by the lung capillary system. In the arterial system, bubbles ([[arterial gas embolism]]) are far more dangerous because they block circulation and cause [[infarction]] (tissue death, due to local loss of blood flow). In the brain, infarction results in [[stroke]], in the spinal cord it may result in [[paralysis]], and in the heart it results in [[myocardial infarction]] ([[myocardial infarction|heart attack]]).==Signs and symptoms==Bubbles can form anywhere in the body, but symptomatic sensation is most frequently observed in the shoulders, elbows, knees, and ankles.This table gives symptoms for the different DCS types.  The "bends" (joint pain) accounts for about 60 to 70 percent of all altitude DCS cases, with the shoulder being the most common site. These types are classifed medically as DCS I. [[Neurological]] symptoms are present in 10 to 15 percent of all DCS cases with headache and visual disturbances the most common. DCS cases with neurological symptoms are generally classified as DCS II. The "chokes" are rare and occur in less than two-percent of all DCS cases.  Skin manifestations are present in about 10 to 15 percent of all DCS cases.{| cellspacing="0" border="1" bgcolor="white"|+ '''Table 1. '''Signs and symptoms of decompression sickness.|- ! DCS Type! Bubble Location! Signs & Symptoms (Clinical Manifestations)|- ! BENDS| Mostly large joints of the body<br>(elbows, shoulders, hip,<br>wrists, knees, ankles)|* Localized deep pain, ranging from mild (a "niggle") to excruciating. Sometimes a dull ache, but rarely a sharp pain.* Active and passive motion of the joint aggravates the pain.* The pain may be reduced by bending the joint to find a more comfortable position.* If caused by altitude, pain can occur immediately or up to many hours later.|- ! rowspan="3" | NEUROLOGIC| Brain|* Confusion or memory loss* Headache* Spots in visual field ([[scotoma]]), tunnel vision, double vision ([[diplopia]]), or blurry vision* Unexplained extreme fatigue or behaviour changes* Seizures, dizziness, [[Vertigo (medical)|vertigo]], [[nausea]], [[vomit]]ing and unconsciousness may occur, mainly due to [[labyrinthitis]]|- | Spinal Cord|* Abnormal sensations such as burning, stinging, and tingling around the lower chest and back* Symptoms may spread from the feet up and may be accompanied by ascending weakness or [[paralysis]]* Girdling abdominal or chest pain|- | Peripheral Nerves|* Urinary and rectal [[incontinence]]* Abnormal sensations, such as numbness, burning, stinging and tingling ([[paresthesia]])* Muscle weakness or twitching|- ! CHOKES| Lungs|* Burning deep chest pain (under the [[sternum]])* Pain is aggravated by breathing* Shortness of breath ([[dyspnea]])* Dry constant cough|- ! SKIN BENDS| Skin|* Itching usually around the ears, face, neck arms, and upper torso* Sensation of tiny insects crawling over the skin* Mottled or marbled skin usually around the shoulders, upper chest and abdomen, with itching* Swelling of the skin, accompanied by tiny scar-like skin depressions ([[pitting edema]])|}==Treatment==Recompression is the only effective treatment for severe DCS, although rest and oxygen (increasing the percentage of oxygen in the air being breathed via a tight fitting [[oxygen mask]]) applied to lighter cases can be effective. Recompression is normally carried out in a [[recompression chamber]]. In diving, a high-risk alternative is [[in-water recompression]].[[Oxygen first aid]] treatment is useful for suspected DCS casualties or divers who have made fast ascents or missed decompression stops. Most fully closed-circuit [[rebreather]]s can deliver sustained high concentrations of oxygen-rich [[breathing gas]] and could be used as an alternative to pure [[open-circuit]] oxygen [[resuscitator]]s.==Common pressure reductions that cause DCS==The main cause of DCS is a reduction in the pressure surrounding the body. Common ways in which the required reduction in pressure occur are:* leaving a high atmospheric pressure environment* rapid ascent through water during a dive* ascent to altitude while flying===Leaving a high pressure environment===The original name for DCS was [[industrial injury|caisson disease]]; this term was used in the 19th century, when large engineering excavations below the [[water table]], such as with the [[pier]]s of [[bridge]]s and with [[tunnel]]s, had to be done in [[caisson (engineering)|caisson]]s under pressure to keep water from flooding the excavations. Workers who spend time in high pressure atmospheric pressure conditions are at risk if they leave that environment and reduce the pressure surrounding them.DCS was a major factor during construction of [[Eads Bridge]], when 15 workers died from what was then a mysterious illness, and later during construction of the [[Brooklyn Bridge]], where it incapacitated the project leader [[Washington Roebling]].===Ascent during a dive===DCS is best known as an [[diving disorders|injury]] that affects scuba divers. The pressure of the surrounding water increases as the diver descends and reduces as the diver ascends. The risk of DCS increases by diving long or deep without slowly ascending and making the [[decompression stops]] needed to eliminate the inert gases normally, although the specific risk factors are not well understood. Some divers seem more susceptible than others under identical conditions.There have been known cases of bends in [[snorkeller]]s who have made many deep dives in succession. DCS may be the cause of the disease [[taravana]] which affects South Pacific island natives who for centuries have dived without equipment for food and [[pearl]]s.Two linked factors contribute to divers' DCS, although the complete relationship of causes is not fully understood:* deep or long dives: inert gases in [[breathing gas]]es, such as [[nitrogen]] and [[helium]], are absorbed into the tissues of the body in higher concentrations than normal ([[Henry's Law]]) when breathed at high pressure.* fast ascents: reducing the ambient pressure, as happens during the ascent, causes the absorbed gases to come back out of solution, and form "micro bubbles" in the [[blood]]. Those bubbles will safely leave the body through the [[lung]]s if the ascent is slow enough that the volume of bubbles does not rise too high.The physiologist [[John Haldane]] studied this problem in the early 20th century, eventually devising the method of staged, gradual decompression, whereby the pressure on the diver is released slowly enough that the nitrogen comes gradually out of solution without leading to DCS. Bubbles form after every dive: slow ascent and [[decompression stops]] simply reduce the volume and number of the bubbles to a level at which there is no injury to the diver. Severe cases of decompression sickness can lead to death. Large bubbles of gas impede the flow of oxygen-rich blood to the [[brain]], [[central nervous system]] and other vital organs.Even when the change in pressure causes no immediate symptoms, rapid pressure change can cause permanent [[bone]] injury called [[dysbaric osteonecrosis]] (DON) "bone cell death from bad pressure". DON can develop from a single exposure to rapid decompression. DON is diagnosed from lesions visible in X-ray images of the bones. Unfortunately, X-rays appear normal for at least 3 months after the permanent damage has occurred; it may take 4 years after the damage has occurred for its effects to become visible in the X-ray images. [http://divermag.com/archives/sep98/divedoctor_sep98.html]====Avoidance====[[Decompression tables]] and [[dive computer]]s have been developed that help the diver choose depth and duration of [[decompression stops]] for a particular dive profile at depth.Avoiding decompression sickness is not an exact science. Accidents can occur after relatively shallow and short dives. To reduce the risks, divers should avoid long and deep dives and should ascend slowly. Also, dives requiring [[decompression stops]] and dives with less than a 16 hour interval since the previous dive increase the risk of DCS. There are many additional risk factors, such as age, obesity, fatigue, use of alcohol, dehydration and a [[Atrial septal defect|patent foramen ovale]]. In addition, flying at high altitude less than 24 hours after a deep dive can be a precipitating factor for decompression illness.[[Astronauts]] aboard the [[International Space Station]] preparing for [[Extra-vehicular activity]] "camp out" at low atmospheric pressure (approximately 10 psi = 700 [[mbar]]) spending 8 sleeping hours in the [[airlock]] chamber before their [[spacewalk]]. Their [[spacesuit]]s can operate at 4.7 psi = 330 mbar for maximum flexibility.====Helium====[[Nitrogen]] is not the only [[breathing gas]] that causes DCS. Gas mixtures such as [[trimix]] and [[heliox]] include [[helium]], which can also be implicated in decompression sickness.Helium both enters and leaves the body faster than nitrogen, and for dives of three or more hours in duration, the body almost reaches saturation of helium. For such dives the decompression time is shorter than for nitrogen-based breathing gases such as air.There is some debate as to the decompression effects of helium for shorter duration dives. Most divers do longer decompressions, whereas some groups like the [[WKPP]] have been pioneering the use of shorter decompression times by including [[decompression stops#Deep stops|deep stops]].Decompression time can be significantly shortened by breathing rich [[nitrox]] (or pure [[oxygen]] in very shallow water) during the decompression phase of the dive. The reason is that the nitrogen outgases at a rate proportional to the difference between the ppN<sub>2</sub> ([[partial pressure]] of nitrogen) in the diver's body and the ppN<sub>2</sub> in the gas that he or she is breathing; but the likelihood of bubbles is proportional to the difference between the ppN<sub>2</sub> in the diver's body and the total surrounding air or water pressure.===Ascent to altitude===People flying in un-pressurized [[aircraft]] at [[high altitude]], such as stowaways, or passengers in a cabin that has experienced rapid decompression, or pilots in an open cockpit, can suffer from decompression sickness. Even [[Lockheed U-2]] pilots experienced altitude DCS in the mid-'50s during the [[Cold War]] flying over their targets. Divers who dive and then fly in aircraft are at risk even in pressurized aircraft because the cabin air pressure is less than the air pressure at sea level. The same applies to divers going into higher elevations by land after diving. Altitude DCS became a commonly observed problem associated with high-altitude balloon and aircraft flights in the 1930s. In present-day aviation, technology allows civilian aircraft (commercial and private) to fly higher and faster than ever before. Though modern aircraft are safer and more reliable, occupants are still subject to the stresses of high-altitude flight and the unique problems that go with these lofty heights. A century-and-a-half after the first DCS case was described, our understanding of DCS has improved and a body of knowledge has accumulated; however, this problem is far from being solved. Altitude DCS is still a risk to the occupants of modern aircraft.There is no specific altitude threshold that can be considered safe for everyone below which it can be assured that no one will develop altitude DCS. However, there is very little evidence of altitude DCS occurring among healthy individuals at [[pressure altitude]]s below 18,000 feet who have not been scuba diving. Individual exposures to pressure altitudes between 18,000 and 25,000 feet have shown a low occurrence of altitude DCS. Most cases of altitude DCS occur among individuals exposed to pressure altitudes of 25,000 feet or higher. A US Air Force study of altitude DCS cases reported that only 13 percent occurred below 25,000 feet The higher the altitude of exposure, the greater the risk of developing altitude DCS. It is important to clarify that although exposures to incremental altitudes above 18,000 feet show an incremental risk of altitude DCS they do not show a direct relationship with the severity of the various types of DCS (see Table 1).[[Arterial gas embolism]] and DCS have very similar treatment because they are both the result of gas bubbles in the body. Their spectra of symptoms also overlap, although those from arterial gas embolism are more severe because they often cause [[infarction]] and tissue death as noted above. In a diving context, the two are joined under the general term of [[decompression illness]]. Another term, [[dysbarism]], encompasses decompression sickness, arterial gas embolism, and [[barotrauma]].Ascent to altitude can happen without flying in places such as the [[Ethiopia]] and [[Eritrea]] highland (8000 feet = about 1.5 miles above sea level) and the [[Peru]] and [[Bolivia]] [[altiplano]]  and [[Tibet]] (2 to 3 miles above sea level). ====Medical treatment====Mild cases of the "bends" and skin bends (excluding mottled or marbled skin appearance) may disappear during descent from high altitude but still require medical evaluation. If the signs and symptoms persist during descent or reappear at ground level, it is necessary to provide [[Hyperbaric oxygen therapy|hyperbaric oxygen treatment]] immediately (100-percent oxygen delivered in a high-pressure chamber). Neurological DCS, the "chokes," and skin bends with mottled or marbled skin lesions (see Table 1) should always be treated with hyperbaric oxygenation. These conditions are very serious and potentially fatal if untreated.====Effects of breathing pure oxygen====[[Image:Oxymask.JPG|left|thumb|145px|Breathing pure oxygen to remove nitrogen from the bloodstream]]One of the most significant breakthroughs in altitude DCS research was oxygen pre-breathing. Breathing pure oxygen before exposure to a low-barometric pressure decreases the risk of developing altitude DCS. Oxygen pre-breathing promotes the elimination or washout of nitrogen from body tissues. Pre-breathing pure oxygen for 30 minutes before starting ascent to altitude reduces the risk of altitude DCS for short exposures (10 to 30 minutes only) to altitudes between 18,000 and 43,000 feet. However, oxygen pre-breathing has to be continued without interruption with in-flight, pure oxygen to provide effective protection against altitude DCS. Furthermore, it is very important to understand that breathing pure oxygen only during flight (ascent, en route, descent) does not decrease the risk of altitude DCS, and should not be used instead of oxygen pre-breathing.Although pure oxygen pre-breathing is an effective method to protect against altitude DCS, it is logistically complicated and expensive for the protection of civil aviation flyers, either commercial or private. Therefore, it is only used now by military flight crews and astronauts for their protection during high altitude and space operations.====Scuba diving before flying====<!-- [This is stated above.] A scuba diver breathes air under pressure higher than sea level atmospheric. This makes more nitrogen dissolve in the body (body nitrogen saturation). The deeper the scuba dive, the greater the rate of body nitrogen saturation.-->The rule about decompression sickness risk on ascending to lower surrounding pressure, does not stop at sea level (even though decompression tables stop at sea level), but continues when a diver soon after diving goes into air pressure much less than at sea level. Altitude DCS can occur during exposure to altitudes as low as 5,000 feet or less. This can happen:# In an [[airliner]] at high altitude the cabin pressure is usually '''not''' at full sea level pressure, but like the air pressure at approx. 8,000 feet altitude.# At high altitudes on land: e.g. if you scuba dive in [[Eritrea]], and then go onto the [[Asmara]] plateau (''where Eritrea's main airport is''), which is about 8000 feet or 1.5 miles or 2400 meters above sea level.# Occasionally in [[cave diving]], "[[Torricellian chamber]]s" are found; they are full of water at less than atmospheric pressure. They arise when the water level drops and there is no way for air to get into the chamber.====What to do if altitude DCS occurs====* Put on your [[oxygen mask]] immediately and switch the regulator to 100% oxygen.* Begin an emergency descent and land as soon as possible. Even if the symptoms disappear during descent, you should still land and seek medical evaluation while continuing to breathe oxygen.* If one of your symptoms is joint pain, keep the affected area still; do not try to work pain out by moving the joint around.* Upon landing seek medical assistance from an aviation authority medical officer, aviation medical examiner (AME), military flight surgeon, or a hyperbaric medicine specialist. Be aware that a physician not specialized in aviation or hypobaric medicine may not be familiar with this type of medical problem. Therefore, be your own advocate.* Definitive medical treatment may involve the use of a hyperbaric chamber operated by specially trained personnel.* Delayed signs and symptoms of altitude DCS can occur after return to ground level whether or not they were present during flight.====Things to remember===={{tone|section}}* Altitude DCS is a risk every time you fly in an un-pressurized aircraft above 18,000 feet (or at lower altitude if you scuba dive prior to the flight).* Be familiar with the signs and symptoms of altitude DCS (see Table 1). Monitor all aircraft occupants, including yourself, any time you fly an unpressurized aircraft above 18,000 feet.* Avoid unnecessary strenuous physical activity prior to flying an un-pressurized aircraft above 18,000 feet, and for 24 h after the flight.* Even if you are flying a pressurized aircraft, altitude DCS can occur as a result of sudden loss of cabin pressure (in-flight rapid decompression).* After exposure to an in-flight rapid decompression, do not fly for at least 24 h. In the meantime, stay vigilant for the possible onset of delayed symptoms or signs of altitude DCS. If you present delayed symptoms or signs of altitude DCS, seek medical attention at once.* Keep in mind that breathing 100% oxygen during flight (ascent, en route, descent) without oxygen pre-breathing before take off does not prevent altitude DCS.* Do not ignore any symptoms or signs that go away during the descent. This could confirm that you are suffering altitude DCS. You should be medically evaluated as soon as possible.* If there is any indication that you may have experienced altitude DCS, do not fly again until you are cleared to do so by an aviation authority medical officer, an aviation medical examiner, a military flight surgeon, or a hyperbaric medicine specialist.* Allow at least 24 hours to elapse between scuba diving and flying.* Be prepared for a future emergency by finding where [[hyperbaric chamber]]s are available in your area of operations. However, keep in mind that not all of the available hyperbaric treatment facilities have personnel qualified to handle altitude DCS emergencies. To obtain information on the locations of hyperbaric treatment facilities capable of handling altitude DCS emergencies, call the Diver's Alert Network at (USA phone number) (919) 684-8111.== Decompression sickness in popular culture ==* In the 1880's, Decompression sickness became known as ''The Bends'' because afflicted individuals characteristically arched their backs in a manner reminiscent of a then popular women's fashion called the [[Grecian Bend]].* A diver with decompression sickness flying in an aircraft was part of the plot in the episode ''[[Airborne (House episode)|Airborne]]'' of [[House (TV series)|''House, M.D.'']], first aired Tuesday [[April 11]], [[2007]].* Rock band [[Radiohead]] released an album entitled ''[[The Bends]]'', a reference to decompression sickness.* Decompression sickness played a part in the anime visual novel "[[Ever 17]]"* A character in the series "Dive" by [[Gordan Korman]] experiences a case of Decompression sickness.* In an episode of "[[Jackie Chan Adventures]]" titled Clash of the Titanics, Jackie experienced decompression sickness* [[Box (comics)|Roger Bochs]], a character in the [[Marvel Comics]] series [[Alpha Flight]], experiences decompression sickness after battling alongside the [[Avengers (comics)|Avengers]] in [[Atlantis (Marvel Comics)|Atlantis]].== References ==<references/>== External links ==* [http://www.scuba-doc.com/dcsprbs.html Decompression Sickness: Prevention, Risks, Exercise, PFO, References, Links]* [http://science.howstuffworks.com/question101.htm What causes the bends?]* [http://www.livescience.com/animalworld/whale_bends_041224.html Whales Suffer From Bends]* [http://www.divernet.com/medical/qanda0200.htm UK Sport Diving Medical Committee: Bone Necrosis]* [http://www.diversalertnetwork.org/medical/articles/index.asp Divers Alert Network: diving medicine articles]* [http://www.ndc.noaa.gov/dp_forms.html Dive Tables from the NOAA]{{Consequences of external causes}}[[Category:SCUBA]][[Category:Diving medicine]][[Category:Aviation medicine]][[Category:Medical emergencies]][[cs:Dekompresní nemoc]][[da:Trykfaldssyge]][[de:Dekompressionserkrankung]][[es:Síndrome de descompresión]][[it:Malattia da decompressione]][[hu:Keszon-betegség]][[nl:Caissonziekte]][[ja:減圧症]][[pl:Choroba dekompresyjna]][[pt:Doença de descompressão]][[ru:Декомпрессионная болезнь]][[fi:Sukeltajantauti]][[sv:Tryckfallssjuka]][[uk:Кесонна хвороба]][[zh:減壓症]]{{WikiDoc Sources}}

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Synonyms and keywords: Decompression illness; DCS; the diver's disease; the bends; Caisson disease; aerobullosis

Overview

Decompression sickness (DCS) is a multi-organ condition characterized by a varied clinical manifestations resulting from an exposure to reduced barometric pressures that leads to a normally dissolved inert gases (mainly nitrogen) in body fluids and tissues to come out of physical solution, and develops a free gas phase by forming an intravascular and extravascular bubbles. The likelihood of DCS is associated with the extent of bubble formation which subsequently causes minor symptoms from a few bubbles formation to a large bubble presenting with the multiorgan failure and death. The severity and nature of the DCS injury vary from mild systemic, musculoskeletal and cutaneous manifestations to severe, life-threatening neurological and cardiorespiratory complications. It is mostly observed in underwater decompression diving activities (e.g SCUBA) and depressurisation events such as emerging from a caisson, flying in an unpressurised aircraft at altitude, and extravehicular activity from spacecraft. The clinical presentation can show an individual susceptibility by varying from day to day under the similar circumstances. The classification of types of DCS based on its symptoms has evolved over years since its origin and research conducted to prevent it. It is not common to report it if the divers follow the recommended guidelines by using dive tables or dive computers to limit their period of exposure and control their rate of ascent speed. If DCS is suspected, it is treated by airway stabilization, high flow oxygen, and hyperbaric therapy in a recompression chamber. An early treatment ensures a significantly higher recovery rate.

Historical Perspective

Template:Wikisource1911Enc

  • 1670: Sir Robert Boyle described the first case of DCS in animals by conducting an experiment on a viper in a vacuum and observing the bubble formation in its eye with significant physical symptoms of discomfort. [1]
  • 1841: Jacques Triger proposed that the two miners while working in the pressurised caisson work developed the symptoms of DCS and thus, documented the first case of DCS in humans. [1]
  • 1847: The French physicians B. Pol and T.J. Watelle explained the effectiveness of recompression in caisson workers for the use of the treatment of DCS. [1] [2]
  • 1857: Felix Hoppe-Seyler supported Boyle's study findings. He further observed that the bubble formation is the underlying cause of sudden death in compressed air workers and recommended recompression therapy as the mode of treatment. [3]
  • 1861: Bucquoy proposed the hypothesis by comparing an injection of air in the veins with the blood gases returning to the free state under the process of decompression. [4]
  • 1868: Alfred Le Roy de Méricourt labelled DCS as an occupational hazard for the sponge divers. [2]
  • 1873: Dr. Andrew Smith studied 110 DCS cases during the construction of the Brooklyn Bridge and coined the terms "caisson disease" and "compressed air illness". Similarly, the term "the bends" was extracted from the fashionable ladies of the period "the Grecian Bend" as the workers emerging from pressurized construction on the Brooklyn Bridge adopted a posture similar to them.[1] [3] [5]
  • 1878: Paul Bert found that the nitrogen gas bubbles released from tissues and blood during or after decompression are responsible for the development of the DCS and further showed that breathing oxygen after developing DCS can help in relieving its symptoms. [6]
  • 1889–90: Ernest William Moir made the first medical airlock when he realized that recompression is the main modality of the treatment to prevent the workforce digging the Hudson River Tunnel dying from DCS. [7] [8]
  • 1908:John Scott Haldane prepared the first recognized decompression table for the British Admiralty which was based on experiments performed on goats using an end point of symptomatic DCS. [1] [9]
  • 1912: Chief Gunner George D. Stillson of the United States Navy created a program to evaluate and refine Haldane's tables which subsequently led to the first publication of the United States Navy Diving Manual and the establishment of a Navy Diving School in Newport, Rhode Island. [10]

Classification

  • In 1960, The Golding Classification was introduced and categorized DCS into type 1 DCS and type 2 DCS. [11]

Table 1 shows the Golding classification of DCS:

FEATURES TYPE 1 TYPE 2
Systems involved Joints, skin, and lymphatics Neurological, inner ear, and cardiopulmonary
Onset of symptoms Build in intensity Gradual or abrupt
Severity Mild Severe
  • This classification is not frequently used in making the diagnosis of DCS following upgradation of the treatment protocols and variable presentations of signs and symptoms. [12]
  • All the manifestations, whether DCS or arterial gas embolism (AGE), were categorized under the general term “decompression illness (DCI)” when the exact diagnosis cannot be finalized because both of them develops from the gas bubble formation in the body, have overlapping of their spectra of signs and symptoms, and similar treatment methods. [13]

Pathophysiology

  • The pathophysiology of DCS is in accordance with Henry’s law. It states that the solubility of a gas in a liquid is directly proportional to the amount of the pressure exerted on the gas and liquid. Thus, the amount of inert gases (eg, nitrogen, helium) dissolved in the blood and tissues increases at higher pressure, and hence the development of DCS depends on the depth and the duration of the dive.
  • During a dive, the partial pressure of nitrogen and oxygen increases which results in creating a diffusion gradient favoring an uptake of nitrogen into the bloodstream and tissues. The physiology of the lungs is to functions as a vehicle for the gaseous exchange and elimination from the body under normal circumstances. As the atmospheric pressure decrease during the ascent, more nitrogen precipitates from the tissues into the bloodstream and then diffuses back into the alveoli for exhalation process. If ascent occurs too rapidly or the elimination gradient is so steep, the gas quickly dissipates from the tissues and blood forming small air bubbles. This process is called “out gassing” or “off gassing”. Conversely, a slow ascent favors an equilibrium to be achieved gradually, and prevents the rapid changes in the partial pressure of nitrogen in the bloodstream. Hence, the amount of bubble formation depends on the depth and duration of the dive, and the rate of the ascent. [14]
  • Venous bubbles may form de novo or result from the intravascular release of tissue bubbles. The venous gas emboli usually get filtered at an arteriole level on reaching the lungs. However, the bubbles may pass directly into the arterial circulation if the pulmonary arterial pressure (PAP) rises after underwater diving. [15] [16]
  1. Bubbles primarily travel to vital organs such as the nervous system; and get lodged in arterioles and capillary beds causing a mass effect. These bubbles obstruct venous outflow and occlude arteries, as well as cause a shearing force on endovascular surfaces and impairs vascular integrity during their transit. The disturbed vascular permeability consequently leads to hemoconcentration, disturbance of microvascular flow, and a breakdown in the blood brain barrier. [17]
  2. Bubbles cause secondary multiple biochemical effects by activating platelets, complement, leucocytes and the clotting cascade; and hence, results in an inflammatory response in the affected tissues. [18]
  3. Autochthonous or extravascular bubbles arise spontaneously, and are more likely to form in tissues with high gas content and poor perfusion because the large amount of gas in the tissues such as spinal cord white matter, adipose tissue, and periarticular tissue cannot be removed by the low perfusing blood volume. [15]
  • Bubbles are responsible for the proximate cause of damage, whereas the several pro-inflammatory activated pathways leads to the progression of an injury. Thus, DCS can have an evolving course with inflammatory mediated manifestations worsening with a period of time.

Clinical Features

  • Clinical presentation: It is frequently idiosyncratic as its "typical" pattern gives an atypical presentation due to the origin of the bubble formation in any part of the body. The US Navy listed the symptoms of DCS in a decreasing order of their overall prevalence in Table 2: [19]
Symptoms Features in %
Local joint pain 89
Arm symptoms 70
Leg symptoms 30
Dizziness 5.3
Paralysis 2.3
Shortness of breath 1.6
Extreme fatigue 1.3
Collapse/unconsciousness 0.5


  • Onset: The median time to symptom/sign onset is 30 minutes and severe neurologic symptoms might present as early as within 10 minutes; and however, majority of symptoms and signs develops within 24 to 48 hours of emerging from the water. The U.S. Navy and Technical Diving International have published a table that documents time to onset of first presenting symptom. The table does not differentiate between types of DCS, or types of symptom. [20] [21]

Table 3 shows the time of onset of symptoms among DCS suspected cases:

Time to onset Percentage of cases
Within 1 hour 42%
Within 3 hour 60%
Within 8 hour 83%
Within 24 hour 98%
Within 48 hour 100%
  • Joints DCS is most frequently noticed in shoulders, elbows, knees, and ankles. Shoulder is the most common site for altitude and bounce diving; and the knees and hip joints for saturation and compressed air work. The symptoms of limb bends arises from increased intermedullary pressure in the ends of long bones; and gas phase separation along ligaments and tendon sheaths, and thus presenting with an extreme discomfort from the simple mechanical distension and movement.
  • Dermatological manifestations are due to the blood extravasated from the cutaneous vessels as a consequence of bubble induced endothelial injury.
  • Pulmonary DCS ("the chokes") is rarely reported in divers; and believed to arise from an extremely huge load of venous bubbles in the pulmonary artery which results in an elevated pulmonary artery and right ventricular pressures, and further increasing the interstitial fluid and hence, leads to the development of the chokes or difficult breathing.
  • Spinal cord DCS have two interrelated mechanisms. The first is obstruction of venous outflow of the spinal cord in the epidural plexus which relatively have a slow blood perfusion rate. Once this process develops, it results in an ongoing and progressive diminution of blood flow to the cord, and thereafter, the second process proceeds with the in-situ bubble formation within the tissue of the spinal cord. [19] [22]

Table 4 shows symptoms and signs of different DCS types: [12]

DCS type Bubble location Signs and symptoms
Musculoskeletal: BENDS Mostly large joints (elbows, shoulders, hip, wrists, knees, ankles)
  • Characteristics: Localized deep pain, ranging from mild to excruciating; dull ache (sometimes); sharp pain (rarely)
  • Aggravating factor: Active and passive motion of the joint
  • Relieving factor: Bending the joint to a comfortable position
  • Onset: Immediate or few hours later in case of altitude induced DCS
Cutaneous: SKIN BENDS Skin
  • Site: Itching around the ears, face, neck, arms, and upper torso
  • Formication: Sensation of tiny insects crawling over the skin
  • Cutis Marmorata: Mottled or marbled skin usually around the shoulders, upper chest and abdomen with itching
  • Pitting edema: Swelling of the skin accompanied by tiny scar-like skin depressions
Neurologic Brain
  • Most common: Headache and visual disturbances
  • Visual changes: Spots in visual field (scotoma), tunnel vision, double vision (diplopia), or blurry vision
  • Confusion or memory loss
  • Unexplained extreme fatigue or behavior changes
  • Seizures, dizziness, vertigo, nausea, vomiting and unconsciousness may occur
Neurologic Spinal cord
  • Abnormal sensations such as burning, stinging, and tingling around the lower chest and back
  • Symptoms may spread from the feet up and may be accompanied by ascending weakness or paralysis
  • Girdling abdominal or chest pain
Neurologic Peripheral Nerves
  • Urinary and rectal incontinence
  • Abnormal sensations, such as numbness, burning, stinging, tingling and paresthesia
  • Muscle weakness or twitching
Constitutional Whole body
  • Headache
  • Unexplained fatigue
  • Generalized malaise, poorly localized aches
Audiovestibular Inner ear
  • Loss of balance
  • Dizziness, vertigo, nausea, vomiting
  • Hearing loss
Pulmonary CHOKES Lungs
  • Dry persistent cough
  • Burning chest pain under the sternum, aggravated by breathing
  • Shortness of breath
Dysbaric osteonecrosis [23] Bones
  • Late manifestation and often occurs without any previous symptoms
  • An insidious form caused by prolonged or closely repeated exposures to increased pressure
  • Typically found in people working in compressed air and in deep commercial rather than recreational divers
  • Deterioration of shoulder and hip articular surfaces cause chronic pain and severe joint disability

Differential Diagnosis

  • Differential diagnosis is the process by which medical personnel rule out which of the potential condition is most likely responsible for the presenting symptoms when two or more probable conditions have overlapping symptoms among the diving-related injuries.
  • An alternative diagnosis should also be suspected if severe symptoms begin more than six hours following decompression without an altitude exposure or if any symptom occurs more than 24 hours after surfacing. [24]

Table 5 below shows various different medical conditions mimicking the DCS: [25]

Medical condition Clinical characteristics
Arterial Gas Embolism (AGE) [14]
  • Pulmonary Barotrauma: It usually occurs when the air expands to cause the lung rupture and releases gas bubbles directly into the arterial circulation.
  • Typical presentation: A diver who surfaces unconscious and remains so, or who loses consciousness within minutes of surfacing.
  • A true medical emergency condition
  • Rapid evacuation to a treatment facility is paramount.
Inner-ear barotrauma
  • Usually occurs during descent
  • Tinnitus, hearing loss, and persistent vertigo [26]
  • Middle-ear barotrauma: Conductive hearing loss seen
  • Both inner-ear and middle-ear barotrauma are usually preceded by difficulty in equalizing middle-ear pressure
  • Alternobaric vertigo: transient vertigo during compression or decompression arises because of asymmetric middle-ear pressure equilibration [27]
Middle-ear or maxillary sinus overinflation
  • It is caused by gas expansion during ascent and an obstructed eustachian tube or sinus ostium
  • Compresses the facial nerve causes unilateral upper and lower facial weakness, [28] or
  • Compression of branches of the trigeminal nerve causes hypoaesthesia of the face [29]
Contaminated diving gas and oxygen toxic effects
  • Carbon monoxide poisoning: contaminated breathing gas can cause encephalopathy and convulsions.
  • Oxygen toxicity: most common in divers using enriched oxygen breathing mixtures; and can cause convulsions at depth.
Musculoskeletal strains or trauma sustained [29]
  • Time of onset (e.g.: before, during, or after diving) and history of trauma or strain are helpful to rule it out.
  • Pain is usually accompanied by tenderness or position-related or motion-related exacerbation on physical examination.
Seafood toxin ingestion
  • Ingestion of toxins (e.g.: ciguatera, puffer fish, paralytic shellfish poisoning )
  • Often associated with gastrointestinal symptoms, and can cause neurological manifestations within hours after ingestion [30]
Immersion pulmonary edema
  • This disorder usually begins during descent or at depth, whereas the onset of cardiorespiratory DCS occurs after the dive
  • They might get confused since both cause dyspnea and cough [31]
Water aspiration
  • Water aspiration could be mistaken for cardiorespiratory DCS
  • Both can cause pulmonary edema, although the diver is usually aware of aspiration
Coincidental, unrelated acute neurological disorder
  • Diagnosis of stroke, hypothermia, hypoglycemia, and spinal hematoma is made with conventional techniques
Thermal stress
  • Usually occur due to cold exposure but sometimes excessive heat can be responsible

Epidemiology and Demographics

  • The incidence of DCS, fortunately, is rare.
  • Recreational divers: It is estimated in about 2 to 4/10,000 dives.
  • Commercial divers: It can be higher ranging from 1.5-10 per 10,000 dives due to prior history of minor musculoskeletal injuries.
  • Its prevalence depends on the length and depth of the dive.
  • The risk for DCS is 2.5 times greater for males in relation to females. [32]

Risk Factors

  • Various environmental, diving and individual factors are related to the predisposition of DCS.
  • In 2005, DeNoble et al conducted a study to find the association of various risk factors with the DCS[33]
    • Multiple risk factors studied: age, gender, body mass index, smoking, asthma, diabetes, cardiovascular disease, previous history of DCI, number of the years since certification, number of dives in the last year, number of diving days, number of dives in a repetitive series, last dive depth, nitrox use, and drysuit use.
    • No significant correlation with DCS: asthma, diabetes, cardiovascular disease, smoking, or body mass index.
    • Positive correlation (higher risk): increased diving depth, previous DCS episodes, multiple consecutive days of diving and being male.
    • Negative correlation (lower risk): nitrox and drysuit use, higher frequency of diving in the past year, increasing age, and years since certification possibly as indicators of more extensive training and experience.

Environmental factors

  • Magnitude of the pressure reduction ratio: DCS is more likely to be experienced with a larger pressure reduction ratio in comparison to a smaller reduction. [34]
  • Temperature: Warm conditions may favor nitrogen uptake which results in an increased level of dissolved nitrogen and hence, putting a diver at higher risk of “out gassing” during ascent phase. Contrarily, the cold conditions slows the process; however, no definitive studies have demonstrated a direct relationship between thermal conditions and development of DCS. [14]
  • Repetitive exposures: A shorter periods of break among similar repetitive dives and ascents to altitudes above 5,500 metres (18,000 ft) will raise the risk of DCS because excessive nitrogen remains dissolved in body tissues for at least 12 hours after each dive, and hence, repeated dives within 1 day predisposes the divers to it.[34]
  • Post dive air travel: Divers who ascend to altitude soon after a dive increase their possibility of developing DCS even if the dive was performed within the dive table safe limits. [35]
  • Diving before travelling to altitude: DCS can occur even without flying if a diver moves to a high-altitude location on land immediately after diving; for example, scuba divers in Eritrea who drive from the coast to the Asmara plateau at 2,400 m (7,900 ft) increase their chances of DCS. [36]
  • Ambient temperature: A very cold ambient temperatures may increase the risk of altitude DCS. However, increasing ambient temperature during decompression following the dives in cold water may reduce the risk levels. [37] [38]

Diving factors

  • Rate of ascent: A rate of ascent shows a positive correlation with faster the ascent, greater the risk. The U.S. Navy Diving Manual indicates that ascent rates greater than about 20 m/min (66 ft/min) from the diving depth increases the possibility of DCS, while other recreational dive tables such as the Bühlmann tables require an ascent rate of 10 m/min (33 ft/min) with the last 6 m (20 ft) taking at least one minute to lower its incidence. A diver exposed to a rapid decompression rate of ascent of above 5,500 metres (18,000 ft) has a greater risk of altitude DCS in comparison to being exposed to the same altitude but at a lower rate of ascent. [34] [36]
  • Duration of diving: A longer duration of the dive, the greater risk of DCS. Similarly, a longer flights, especially to altitudes of 5,500 m (18,000 ft) and above, holds a higher risk of altitude DCS. [34]
  • Diving at altitude: Diving in water whose surface altitude is above 300 m (980 ft) have a higher risk of developing DCS; for example, Lake Titicaca is at 3,800 m (12,500 ft) and diving in it without using versions of decompression tables or dive computers that are modified for high-altitude predisposes the divers to DCS. [35]

Individual factors

  • Dehydration: Drinking isotonic saline or adequate hydration will raise the serum surface tension which is helpful in controlling bubble size and hence, reduces the chances of DCS in aviators. Therefore, maintaining adequate hydration is recommended. [36] [37]
  • Patent foramen ovale (PFO): At birth, a hole between the atrial chambers of the heart in the fetus gets normally closed by a flap with the first breath. However, in about 20% of adults, where the flap does not seal completely, allows blood through the hole during coughing or activities that raise chest pressure. During diving, PFO can allow venous blood with microbubbles of inert gas to bypass the lungs, where the bubbles would otherwise be filtered out by the lung capillary system, and return directly to the arterial system (including arteries to the brain, spinal cord and heart). In the arterial system, bubbles are highly dangerous because they block circulation and cause infarction. In the brain, infarction results in stroke; whereas in the spinal cord, it may predispose to paralysis. [36] [39]
  • Age: An increasing age (especially >42 years of age) has been associated with a higher incidence of altitude DCS. [37]
  • Previous injury: Divers with a previous history of recent joint or limb injuries may have a higher susceptibility to development of the decompression-related bubbles. [40]
  • Body type: A diver with a high body fat content stores about the half the total amount of the nitrogen which predisposes them to a higher chances of DCS. This is due to five times greater solubility of nitrogen in fat than water, and hence, resulting in a higher levels of total body dissolved nitrogen during elevated atmospheric pressure. [37] [41]
  • Alcohol consumption: It increases chances of dehydration and inhibits pituitary release of antidiuretic hormone (ADH); and therefore may increase susceptibility to DCS. [37] Contrarily, another study found no correlation between alcohol consumption and developing DCS. [42]
  • Work and exercise: DCS is strongly related with the level of work or exercise done at depth or shortly after diving because it promotes increased inert gas uptake. Therefore, any kind of strenuous exercise will promote bubble formation, and lighter exercise during ascent or stop phase will favor gas excretion. [14]
  • Asthma: Asthmatics are generally advised not to dive due to a theoretical risk of bronchospasm triggered by cold or changing environments, inability to have an immediate response to an asthma attack while being submerged, and supposed increased barotrauma during ascent. However, more studies are warranted as there is limited data to support preventing them from diving. Well-controlled asthmatics with normal PFTs can occasionally be permitted to dive, however, an assessment should be made on a case-by-case basis. [14]

Diagnosis

  • DCS is primarily a clinical diagnosis assessed with a thorough and detailed dive history from a conscious patient and the clinical examination, including the neurological exam.
  • The specific symptoms/signs and their particular time of onset (table 3 and 4) aid in suspecting and establishing the diagnosis.
  • However, the relief of symptoms by recompression will make the definitive confirmation of the probable diagnosis.
  • Hence, an immediate treatment should be begun with no delay for further diagnostic work up.

Diagnostic criteria

In 2004 Freiberger identified important five diagnostic factors in their order of importance using simulated diving injury cases:[43]

  • (1) A neurologic symptom as the primary presenting symptom,
  • (2) onset time to symptoms,
  • (3) joint pain as a presenting symptom,
  • (4) any relief after recompression treatment, and
  • (5) maximum depth of the last dive

Laboratory findings

  • DCS is associated with hemoconcentration, and elevated serum CK is seen in severe AGE.
  • However, none of the laboratory studies make a definitive diagnosis of DCS. [14]

Radiological findings

  • No imaging study can confirm the diagnosis of DCS.
  • Bubble formation can occasionally be identified on MRI or CT scans; however, they are not considered the reliable method to rule out DCS due to their low sensitivity level in making the diagnosis.
  • Although, they might be used to rule out the other differential disorders that presents with the similar signs and symptoms (eg, herniated intervertebral disk, ischemic stroke, central nervous system hemorrhage).
  • These studies should be performed with no delay as prompt intervention is important in the successful management of the DCS.

Chest and Joints Radiography

  • Pneumothorax, pneumomediastinum, pulmonary overexpansion injury, or pulmonary edema should always be ruled out with chest radiographs.
  • Radiographs rarely detect bubble formation in joints affected by pain.
  • Skeletal x-rays are not considered diagnostic for dysbaric osteonecrosis which may show joint degeneration; and hence cannot be used to differentiate between different joint disorders. [14] [25]

Computed Tomography Scan

  • Head CT: A “normal” head CT is not reliable in excluding DCS due to the very low chances of visibility of vascular gas bubbles on CT films in the cases of suspected DCS. However, it should be strongly considered in any patient who presented with an altered mental status in order to evaluate alternative diagnoses, such as subdural or epidural hematoma. [14] [44]
  • Chest CT: An extrapulmonary air can be detected on it, but it should be avoided due to its high radiation exposure level. [25]

Magnetic Resonance Imaging

  • MRI can be falsely reassuring for detecting the spinal cord or brain abnormalities related to DCS.
  • However, it can diagnose ischemic lesions of the brain or spinal cord due to the etiologies other than DCS. [45]

Other diagnostic studies

  • Doppler ultrasonography and Echocardiography: They are not considered the diagnostic tests for DCS; but done to rule out right to left shunt and for research purposes into venous gas emboli. [46]
  • Neurophysiological tests (eg, audiometry and electronystagmography for inner-ear decompression sickness): They can usually be delayed until after recompression. [25]
  • Non invasive pulmonary diagnostic test: None of them are used in making or excluding the diagnosis. [14]
  • Pulmonary diagnostic procedures (e.g.: Bronchoscopy): None is required in making or excluding the diagnosis. [14]
  • Pathology/Cytology/Genetics Study: None is considered in making or excluding the diagnosis. [14]

Although laboratory and radiological analyses are helpful for detection of DCS related abnormalities in some cases; however, these studies are not considered as the deciding factor for the start of the recompression therapy, and hence, recompression should be given with no delay unless there is a strong suspicion of other non-diving related etiologies (eg, cerebral hemorrhage). [25]

Treatment

The several elements to the effective management of DCS consist of initial treatment including on-the-scene evaluation and first aid; transportation; and definitive medical treatment.

On the scene first aid

  • The foundation of first aid is the basic life support.
  • An initial management should focus on the treatment and stabilization of ABC's (airway, breathing, and circulation) in the patients with an altered mental status or loss of consciouness.
  • All DCS suspected cases should have initial treatment with high flow oxygen at 15ltr/min via a non-rebreathe mask or pocket masks regardless of their oxygen saturation levels.
  • This high-flow 100% oxygen enhances nitrogen washout by widening the nitrogen pressure gradient between the lungs and the circulation, thus accelerating reabsorption of embolic bubbles. [23]
  • An early oxygen first aid is important and may reduce symptoms substantially, but this should not change the recommended treatment plan.
  • However, an initial oxygen breathing may clears the symptoms of air embolism and serious DCS, but they may reappear later due to which always contact DAN at +1-919-684-9111 or a dive physician in all the cases of suspected DCI, even if the symptoms and signs appear to have resolved. [47]
 
 
 
 
 
 
 
Decompression sickness
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Mild Symptoms:
•Inhalation of oxygen with FiO2 1.0;
•Fluid administration (i.v. if possible,otherwise oral in unconscious patient)
 
 
 
 
 
 
 
Severe Symptoms with pain, neurological and/or pulmonary impairment
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Complete relief of symptoms within 30 minutes
 
 
 
 
 
 
 
Emergency treatment:
•Flat supine position;
•CPR if necessary;
•Insufflation of 100% inspired Oxygen;
•Intubation when unconscious;
•Intravenous line;
•Infusion therapy;
•HBOT as soon as possible
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
If no
 
 
 
 
 
Hyperbaric Oxygen Therapy:
•Treatment protocol most widespread: Table 6 USN;
•When intubated: paracentesis recommended;
•Lung ventilated at both sides?;
•Pneumothorax?
 
 
 
 
 
 
 
If yes
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Further drug therapy (scientifically not finally proven);
•Corticosteroids, Aspirin, Lidocaine
 
 
 
 
 
Further measures:
•Foley catheters;
•Renal protection;
•Early rehabilitation measures;
•Physiotherapeutic excercise between treatments
 
Hospitalisation for 24h
 
 
 
 
 
 
 
 
 
 
 
 
 

Figure 1: Treatment algorithm of Decompression Sickness (DCS)[48]

Fluid administration

  • It is indicated to minimize the dehydration and restore lost intravascular volume.
  • Oral resuscitation fluid (or plain water) is indicated for alert patients with mild manifestations.
  • Isotonic IV fluid resuscitation and maintenance IV fluids should be administered to those with serious manifestations in order to counteract interstitial fluid shifts and decrease in plasma volume arising from an endothelial injury.
  • Insert a catheter if there is any suspicion of the patient having urinary retention. [23]

Positioning and transportation

  • The supine position or the recovery position should be preferred in case vomiting occurs.
  • The Trendelenburg position and the left lateral decubitus position (Durant's maneuver) have beneficial effect in cases where air emboli are suspected; however, these positions are no longer recommended for prolonged duration due to concerns regarding cerebral edema. [49]
  • It is essential that the suspected cases should be stabilized at the nearest medical center before transportation to a recompression chamber.
  • However, patients with severe symptoms need an evacuation to a suitable recompression facility because time to treatment and severity of the injury are important determinants of outcome; and hence, transport should not be delayed for the performance of nonessential procedures.

Aeromedical transport:

  • Instructions to fly the patient “as low as safely possible” should be given to helicopter transport.
  • Pressurized aircraft with 1 atmosphere internal pressure is preferred.
  • Unpressurized aircraft such as helicopters: The flight altitude should be limited to 300 m or 1000 ft if possible, and oxygen should be given continuously. [32]
  • Commercial aircraft, although pressurized, typically have a cabin pressure equivalent to 2438 m (8000 ft) at normal cruise altitude, but it may precipitate DCS symptoms. [14] [23]

Definitive treatment

Hyperbaric Oxygen Therapy (HBOT)

  • The definitive treatment is hyperbaric oxygen (HBOT) therapy which delivers the pure 100% oxygen at a pressure substantially higher than that of atmospheric pressure in recompression chambers.
  • Delays of > 4 hours from the time of injury to recompression correlate with a significant increase in the incidence of residual symptoms following therapy and hence, it should be initiated as soon as possible. [14]
Indication
  • All the patients, except those whose symptoms are limited to itching, skin mottling, and fatigue, may be treated with oxygen therapy alone; however these patients should be observed for any kind of further deteriorating condition. [23]
Effects of Recompression therapy
  • Bubble crushing: As per Boyles law, increasing pressure decreases the volume of bubbles.
  • Flushing out the nitrogen bubbles with oxygen delivery by improving gradient.
  • Healing damaged tissue with hyperbaric oxygen [50]
Equipment
  • Monoplace chamber: An acrylic tube sized chamber which have a capacity of one patient
  • Multiplace chamber: It is sized to accommodate one or more patients with one or more technicians or other medical personnel. They are designed to allow patients, tenders or equipment to be transferred into and out of the chamber while treatment is ongoing. [47] [51]
Regimen
  • A common HBOT regimen: The U.S. Navy Treatment Table 6 (USN 2008).
  • Regimen protocol:
    • HBOT chamber is brought to 2.8 atmospheres absolute (ATA), (equivalent of depth of 60 feet/18 meters) over a few minutes; and
    • Then 100% FiO2 is initiated.
    • 100% FiO2 is used for 20 minutes at a time, alternating with 5 minute intervals of room air breathing to reduce the risk of oxygen toxicity.
    • Upon completion, the pressure is increased by no more than 1 foot/minute, with a prolonged period of equilibration at 30 feet.
    • The total therapy time is about 5 hours.
    • The therapy can be continued daily for several days until no further improvement is seen in the patient's symptoms. [47] [52]
Mechanism of action
  • The mechanism of HBOT is twofold.
    • An elevated atmospheric pressure in the chamber increases the partial pressure of gases and dissolution of nitrogen back into liquid (Henry’s law), and the increased pressure also decreases the volume of gas present in the body (Boyle’s law).
    • An increased FiO2 results in decreased partial pressure of nitrogen in inspired gas. This enhances the diffusion gradient of nitrogen out of body tissues, favoring exhalation and elimination from the body, and blunting the neutrophillic response to injured endothelium. [14]
Risks

[14] [53]

  • Barotrauma:
    • Middle ear barotrauma: most common adverse effect of HBOT; generally requires supportive care. Bilateral tympanostomy tubes may be required in severe cases.
    • Pulmonary barotrauma: risk of pneumothorax; chest tube can be inserted.
    • Pneumomediastinum: managed conservatively.
    • Similar mechanism and management as barotrauma caused by diving.
  • Oxygen toxicity:
    • Pulmonary toxicity: small airways dysfunction observed on exceeding the treatment duration and pressure beyond the recommended therapeutic protocols.
    • CNS toxicity: generalized tonic-clonic seizures occur with an incidence of approximately 1-4 per 10,000 patient treatments. Risk is higher in patients who are hypercapnic, acidemia and/or septic.
  • Seizures: mechanisms not well-understood.
    • CNS toxicity: managed by decreased FiO2 with same elevated atmospheric pressure.
    • Ocular toxicity: myopia can be seen in those who undergo prolonged daily therapy.
  • Confinement anxiety: Managed with anxiolytics.
  • Fire: due to elevated FiO2.

In-water recompression (IWR) therapy

  • It is beneficial only with a substantial amount of planning, support, equipment and personnel; appropriate water conditions; and suitable patient status.
  • Critical challenges can arise from the changes in the patient's consciousness, oxygen toxicity, gas supply, and even thermal stress.
  • An unsuccessful IWR may leave the patient in worse shape than had the attempt not been made.
  • Hence, it would be suitable for an organized and disciplined group of divers with suitable equipment and practical training in the procedure. [49] [47]
Breathing pure oxygen to remove nitrogen from the bloodstream

Adjuvant treatment

  • Aspirin, NSAIDs, and corticosteroids have all been studied and shown no beneficial use in the management of DCS. However, they may mask the symptoms and exacerbate micro-haemorrhages caused by DCS resulting in a permanent sequelae.
  • Opiates should also be avoided as they can increase the risk of oxygen toxicity.
  • Oxygen is usually sufficient to control pain. [14] [50]

Follow-up evaluation and return to diving

  • Follow-up treatments along with physical therapy is required in the severe cases where significant residual neurological dysfunction may be present even after the most aggressive treatment.
  • Clearing a diver after DCS to return to diving is a complex undertaking with potential medical and legal risks. A careful risk and benefit assessment to ensure that the diver is completely asymptomatic and back to his or her pre-dive baseline function must be conducted by both the diver and the physician. A referral of the patient to a diving medicine specialist is appropriate in case of improperly clearing a diver to return to diving keeping in mind the potential life-threatening implications. Divers should be instructed to refrain from diving for the remainder of their lives in the cases where the risks clearly outweigh the benefits. Furthermore, a diver who has had multiple bouts of DCS even if symptoms were not severe and resolves completely must take special considerations. In such cases, a Diving Medical Specialist must be consulted to determine if diving can be resumed safely.
  • The physician must also consider when it is safe for a patient to fly home or drive at altitude. A retrospective review of 126 DCS cases demonstrated that those who flew home on commercial flights < 72 hours after recompression had a higher likelihood of recurrence of symptoms and signs of DCS. Similarly, physicians should be wary if patients must drive through high-altitude areas, as the drop in atmospheric pressure could, at least theoretically, potentiate a recurrence. [14]
  • The US Navy has recommended the guidelines for returning to diving after treatment with limited time off for the professional divers as their operations should not get compromised; whereas diving is not a livelihood for the recreational divers, so a more conservative approach should be adopted to further minimize the chance for the recurrence of a diving injury. [54]

Table 6 elaborate the recommendations given by the US Navy for return to diving:

Clinical features Professional Divers Recreational divers
Pain-only DCI with no neurological symptoms May resume diving two to seven days after treatment A minimum of two weeks without diving is recommended
Minor neurological symptoms May resume diving two to four weeks after treatment depending on symptom severity Six weeks without diving is recommended
Severe neurological symptoms or any residual symptoms Must be reevaluated three months after treatment and get clearance from a Diving Medical Officer No further diving is recommended

Prognosis

Prognosis is severity dependent. It also depends upon on other factors such as the time to recompression, availability and time to surface oxygen, previous episode, and supportive care. [49]

Prevention

  • Avoided by limiting the depth and duration of dives to a range that does not need decompression stops during ascent (called no-stop limits) or by ascending with decompression stops as specified in published guidelines (eg, the decompression table in the US Navy Diving Manual). [52] [55]
  • Wearing a portable dive computer that continually tracks depth and time at depth and calculates a decompression schedule. Computer divers should be cautious in approaching no-decompression limits, especially when diving deeper than 100 feet (30 meters).
  • Making a safety stop for a few minutes at about 4.6 m (15 ft) below the surface. [55]
  • Recreational divers should dive conservatively, whether they are using dive tables or computers.
  • Experienced divers often select a table depth (versus actual depth) of 10 feet (3 meters) deeper than called for by standard procedure. This practice is highly recommended for all divers, especially when diving in cold water or under strenuous conditions. [54]
  • Avoiding the risk factors noted above (deep/long dives, exercise at depth or after a dive) will decrease the chance of DCS.

Altitude DCS: Things to remember

  • Altitude DCS is a risk every time you fly in an un-pressurized aircraft above 18,000 feet (or at a lower altitude if you scuba dive prior to the flight).
  • Be familiar with the signs and symptoms of altitude DCS. Monitor all aircraft occupants, including yourself, any time you fly an unpressurized aircraft above 18,000 feet.
  • Avoid unnecessary strenuous physical activity prior to flying an un-pressurized aircraft above 18,000 feet, and for 24 h after the flight.
  • Even if you are flying a pressurized aircraft, altitude DCS can occur as a result of a sudden loss of cabin pressure (in-flight rapid decompression).
  • Put on your oxygen mask immediately and switch the regulator to 100% oxygen.
  • Begin an emergency descent and land as soon as possible. Even if the symptoms disappear during descent, you should still land and seek medical evaluation while continuing to breathe oxygen.
  • If one of your symptoms is joint pain, keep the affected area still; do not try to work the pain out by moving the joint around.
  • After exposure to an in-flight rapid decompression, do not fly for at least 24 h. In the meantime, stay vigilant for the possible onset of delayed symptoms or signs of altitude DCS. If you present delayed symptoms or signs of altitude DCS, seek medical attention at once.
  • Keep in mind that breathing 100% oxygen during flight (ascent, en route, descent) without oxygen pre-breathing before take-off does not prevent altitude DCS.
  • Do not ignore any symptoms or signs that go away during the descent. This could confirm that you are suffering altitude DCS. You should be medically evaluated from an aviation authority medical officer, aviation medical examiner (AME), military flight surgeon, or a hyperbaric medicine specialist. Be aware that a physician not specialized in aviation or hypobaric medicine may not be familiar with this type of medical problem. Therefore, be your own advocate.
  • If there is any indication that you may have experienced altitude DCS, do not fly again until you are cleared to do so.
  • Allow at least 24 hours to elapse between scuba diving and flying.
  • Be prepared for a future emergency by finding where hyperbaric chambers are available in your area of operations. However, keep in mind that not all of the available hyperbaric treatment facilities have personnel qualified to handle altitude DCS emergencies. To obtain information on the locations of hyperbaric treatment facilities capable of handling altitude DCS emergencies, call the Diver's Alert Network at (USA phone number) (919) 684-9111.

FOR MORE INFORMATION:

Decompression sickness in popular culture

  • In the 1880s, DCS became known as The Bends because afflicted individuals characteristically arched their backs in a manner reminiscent of a then-popular women's fashion called the Grecian Bend.
  • A diver with DCS flying in an aircraft was part of the plot in the episode Airborne of House, M.D., first aired Tuesday April 11, 2007.
  • Rock band Radiohead released an album entitled The Bends, a reference to DCS.
  • DCS played a part in the anime visual novel "Ever 17"
  • A character in the series "Dive" by Gordan Korman experiences a case of DCS.
  • In an episode of "Jackie Chan Adventures" titled Clash of the Titanics, Jackie experienced DCS.
  • Roger Bochs, a character in the Marvel Comics series Alpha Flight, experiences DCS after battling alongside the Avengers in Atlantis.

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