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| {{SK}} Apnoea | | {{SK}} Apnoea |
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| '''See also:''' [[Sleep apnea]]
| | ==[[Apnea overview|Overview]]== |
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| '''Apnea''', '''apnoea''', or '''apnœa''' ([[Greek language|Greek]] απνοια, from α-, privative, πνεειν, to breathe) is a technical term for suspension of external [[respiration (physiology)|breathing]]. During apnea there is no movement of the [[muscle]]s of respiration and the volume of the [[lung]]s initially remains unchanged. Depending on the patency (openness) of the airways there may or may not be a flow of gas between the [[lungs]] and the environment; [[gas exchange]] within the lungs and [[cellular respiration]] is not affected. Apnea can be voluntarily achieved (i.e., "'''holding one's breath'''"), [[recreational drug use|drug]]-induced (e.g., [[opiate]] toxicity), mechanically induced (e.g., strangulation), or it can occur as a consequence of neurological disease or [[Physical trauma|trauma]].
| | ==[[Apnea historical perspective|Historical Perspective]]== |
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| ==Mechanism== | | ==[[Apnea classification|Classification]]== |
| Under normal conditions, humans cannot store much oxygen in the body. Apnea of more than approximately one minute's duration therefore leads to severe lack of oxygen in the [[circulatory system|blood circulation]]. Permanent [[brain damage]] can occur after as little as three minutes and [[death]] will inevitably ensue after a few more minutes unless ventilation is restored. However, under special circumstances such as [[hypothermia]], [[hyperbaric oxygenation]], apneic oxygenation (see below), or [[extracorporeal membrane oxygenation]], much longer periods of apnea may be tolerated without severe consequences.
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| Untrained humans cannot sustain voluntary apnea for more than one or two minutes. The reason for this is that the rate of breathing and the volume of each breath are tightly regulated to maintain constant values of [[carbon dioxide|CO<sub>2</sub>]] tension and [[pH]] of the [[blood]]. In apnea, CO<sub>2</sub> is not removed through the lungs and accumulates in the blood. The consequent rise in CO<sub>2</sub> tension and drop in pH result in stimulation of the respiratory centre in the brain which eventually cannot be overcome voluntarily.
| | ==[[Apnea pathophysiology|Pathophysiology]]== |
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| When a person is immersed in water, physiological changes due to the [[mammalian diving reflex]] enable somewhat longer tolerance of apnea even in untrained persons. Tolerance can in addition be trained. The ancient technique of free-diving requires breath-holding, and world-class free-divers can indeed hold their breath underwater up to depths of 223 metres and for more than eight minutes. An '''apneist''', in this context, is someone who can hold their breath for a long time.
| | ==[[Apnea causes|Causes]]== |
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| ==Hyperventilation== | | ==[[Apnea differential diagnosis|Differentiating Apnea from other Diseases]]== |
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| Many people have discovered, on their own, that voluntary [[hyperventilation]] before beginning voluntary apnea allows them to hold their breath for a longer time. Some of these people incorrectly attribute this effect to increased [[oxygen]] in the blood, not realizing that it is actually due to a decrease in CO<sub>2</sub> in the blood and lungs. Blood leaving the lungs is normally fully saturated with [[oxygen]], so [[hyperventilation]] of normal air cannot increase the amount of [[oxygen]] available. Lowering the CO<sub>2</sub> concentration increases the time before the respiratory center becomes stimulated, as described above.
| | ==[[Apnea epidemiology and demographics|Epidemiology and Demographics]]== |
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| '''This error has led some people to use [[hyperventilation]] as a means to increase their diving time, not realizing that there is a danger that their body may exhaust its [[oxygen]] while underwater, before they feel any urge to breathe, and that they can suddenly lose consciousness — a [[shallow water blackout]] — as a result. If a person loses consciousness underwater, especially in fresh water, there is a considerable danger that they will drown. An alert diving partner would be in the best position to rescue such a person.'''
| | ==[[Apnea risk factors|Risk Factors]]== |
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| ==Apneic oxygenation== | | ==[[Apnea natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
| Because the exchange of gases between the blood and airspace of the lungs is independent of the movement of gas to and from the lungs, enough oxygen can be delivered to the circulation even if a person is apneic. This phenomenon (''apneic oxygenation'') is explained as follows:
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| With the onset of apnea, an underpressure develops in the airspace of the lungs, because more oxygen is absorbed than CO<sub>2</sub> is released. With the airways closed or obstructed, this will lead to a gradual collapse of the lungs. However, if the airways are patent (open), any gas supplied to the upper airways will follow the pressure gradient and flow into the lungs to replace the oxygen consumed. If pure oxygen is supplied, this process will serve to replenish the oxygen stores in the lungs. The uptake of oxygen into the blood will then remain at the usual level and the normal functioning of the organs will not be affected.
| | ==Diagnosis== |
| | [[Apnea history and symptoms| History and Symptoms]] | [[Apnea physical examination | Physical Examination]] | [[Apnea laboratory findings|Laboratory Findings]] | [[Apnea chest x ray|Chest X Ray]] | [[Apnea CT|CT]] | [[Apnea MRI|MRI]] | [[Apnea ultrasound|Ultrasound]] | [[Apnea other imaging findings|Other Imaging Findings]] | [[Apnea other diagnostic studies|Other Diagnostic Studies]] |
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| However, no CO<sub>2</sub> is removed during apnea. The [[partial pressure]] of CO<sub>2</sub> in the airspace of the lungs will quickly equilibrate with that of the blood. As the blood is loaded with CO<sub>2</sub> from the metabolism, more and more CO<sub>2</sub> will accumulate and eventually displace oxygen and other gases from the airspace. CO<sub>2</sub> will also accumulate in the tissues of the body, resulting in [[respiratory acidosis]].
| | ==Treatment== |
| | [[Apnea medical therapy|Medical Therapy]] | [[Apnea surgery|Surgery]] | [[Apnea primary prevention|Primary Prevention]] | [[Apnea secondary prevention|Secondary Prevention]] | [[Apnea cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Apnea future or investigational therapies|Future or Investigational Therapies]] |
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| Under ideal conditions (i.e., if pure oxygen is breathed before onset of apnea to remove all nitrogen from the lungs, and pure oxygen is insufflated), apneic oxygenation could theoretically be sufficient to provide enough oxygen for survival of more than one hour's duration in a healthy adult. However, accumulation of carbon dioxide (described above) would remain the limiting factor.
| | ==Case Studies== |
| | [[Apnea case study one|Case#1]] |
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| Apneic oxygenation is more than a physiologic curiosity. It can be employed to provide a sufficient amount of oxygen in thoracic surgery when apnea cannot be avoided, and during manipulations of the airways such as [[bronchoscopy]], [[intubation]], and surgery of the upper airways. However, because of the limitations described above, apneic oxygenation is inferior to extracorporal circulation using a heart-lung machine and is therefore used only in emergencies and for short procedures.
| | ==Related Chapters== |
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| ===Complete Differential Diagnosis of the Causes of Apnea=== | |
| (In alphabetical order)
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| *[[Achondroplasia]]
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| *[[Anemia of prematurity]]
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| *[[Angina tonsillaris]]
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| *[[Arnold-Chiari malformation]]
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| *[[Asthma]]
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| *[[Ataxic respiration]]
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| *[[Atrial fibrillation]]
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| *[[Automatic Positive Airway Pressure]]
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| *[[Biot's respiration]]
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| *[[Body fat redistribution (BFR) syndrome]]
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| *[[Breastfeeding]]
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| *[[Bupivacaine]]
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| *[[Carbon dioxide]]
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| *[[Cheyne-Stokes respiration]]
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| *[[Chlordiazepoxide]]
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| *[[Chondrodystrophy]]
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| *[[Chronic Airway-Digestive Inflammatory Disease (CAID)]]
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| *[[Congenital Central Hypoventilation Syndrome]]
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| *[[Cyanide]]
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| *[[Delayed sleep phase syndrome]]
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| *[[Deviated septum]]
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| *[[Diazepam]]
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| *[[Down syndrome]]
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| *[[Drowning]]
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| *[[Empty nose syndrome]]
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| *[[Gaucher's disease]]
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| *[[Glycine encephalopathy]]
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| *[[Hunter syndrome]]
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| *[[Hypercapnia]]
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| *[[Hyperpituitarism]]
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| *[[Hypersomnia]]
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| *[[Infant respiratory distress syndrome]]
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| *[[Iron deficiency anemia]]
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| *[[Joubert syndrome]]
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| *[[Levobupivacaine]]
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| *[[Lidocaine]]
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| *[[Marfan syndrome]]
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| *[[Mucopolysaccharidosis]]
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| *[[Nasal congestion]]
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| *[[Obesity hypoventilation syndrome]]
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| *[[Obstruction]]
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| *[[Oxymorphone]]
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| *[[Pancuronium]]
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| *[[Panic disorder]]
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| *[[Polycystic ovary syndrome]]
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| *[[Premature birth]]
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| *[[Propofol]]
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| *[[Pulmonary atresia]]
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| *[[Ropivacaine]]
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| *[[Sodium thiopental]]
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| *[[Strychnine]]
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| *[[Tonic-clonic seizure]]
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| *[[Toxidrome]]
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| *[[Trazodone]]
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| *[[Upper Airway Resistance Syndrome (UARS)]]
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| ===Complete Differential Diagnosis of the Causes of ...===
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| (By organ system)
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| {|style="width:80%; height:100px" border="1"
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| |style="height:100px"; style="width:25%" border="1" bgcolor="LightSteelBlue" | '''Cardiovascular'''
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| |style="height:100px"; style="width:75%" border="1" bgcolor="Beige" | No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Chemical / poisoning'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Dermatologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Drug Side Effect'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Ear Nose Throat'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Endocrine'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Environmental'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Gastroenterologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Genetic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Hematologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Iatrogenic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Infectious Disease'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Musculoskeletal / Ortho'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Neurologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Nutritional / Metabolic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Obstetric/Gynecologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Oncologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Opthalmologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Overdose / Toxicity'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Psychiatric'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Pulmonary'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Renal / Electrolyte'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Rheum / Immune / Allergy'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Sexual'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Trauma'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Urologic'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |-bgcolor="LightSteelBlue"
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| | '''Miscellaneous'''
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| |bgcolor="Beige"| No underlying causes
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| |-
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| |}
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| ==References==
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| <div class="references-small">
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| <!--See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the <ref(erences/)> tags-->
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| <references/>
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| </div>
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| *J.F.Nunn; ''Applied Respiratory Physiology''; Butterworth-Heinemann Ltd; ISBN 0-7506-1336-X (4th edition, 1993)
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| ==See also==
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| *[[Hypopnea]] | | *[[Hypopnea]] |
| *[[Sleep apnea]] | | *[[Sleep apnea]] |
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| *[http://www.AwakeInAmerica.org/ Awake in America] - national non-profit focused on sleep and sleep disorders, and works with individuals around the United States in establishing community education groups and outreach programs. | | *[http://www.AwakeInAmerica.org/ Awake in America] - national non-profit focused on sleep and sleep disorders, and works with individuals around the United States in establishing community education groups and outreach programs. |
| *[http://www.menshealth.com/cda/article.do?site=MensHealth&channel=health&category=other.diseases.ailments&conitem=98f183b403517010VgnVCM200000cee793cd____&page=4 menshealth] | | *[http://www.menshealth.com/cda/article.do?site=MensHealth&channel=health&category=other.diseases.ailments&conitem=98f183b403517010VgnVCM200000cee793cd____&page=4 menshealth] |
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| [[ca:Apnea]] | | [[ca:Apnea]] |