Respiratory failure mechanical ventilation
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Hadeel Maksoud M.D.[2]
Overview
Mechanical ventilation aims to correct abnormalities in oxygenation of the blood and tissues, reduce the respiratory effort and prevent dynamic hyperinflation. Different modes of ventilation are available to suit each patient's individual needs, such as assisted-control ventilation.
Mechanical ventilation
Mechanical ventilation aims to correct abnormalities in oxygenation of the blood and tissues, reduce the respiratory effort and prevent dynamic hyperinflation.
Principles of Mechanical Ventilation
- Mechanical ventilation is basically used to:[1]
Indications
- Life threatening respiratory failure:[2][3][4][5]
- Severe respiratory failure with failure of non-invasive ventilation (NIV) in addition to rapid, shallow breathing, cardiopulmonary arrest, and severe hemodynamic compromise.
- Failure of noninvasive ventilation:
- Indications of failed NIV include:
- A lack of improvement in arterial carbon dioxide tension (PaCO2) and pH within 1.5 - 2 hours
- Encephalopathy
- Agitation
- Unclearable secretions
- Intolerable mask interface
- Decreased oxygen saturation
- Hemodynamic instability
- Indications of failed NIV include:
- Arterial blood gas abnormalities
- Incorrectable hypoxemia despite oxygen supplementation
- Severe respiratory acidosis unresponsive to therapy and/or NIV
Endotracheal intubation
- Endotracheal intubation acts as the connection between the ventilator and the patient.[6][4]
- Intubation can be performed endotracheally or through a tracheostomy.
- The tube must be placed correctly, and this is confirmed through:
- Chest x-ray
- Chest auscultation
- Carbon dioxide detector
- Proper cuff pressure must be maintained and not exceed 25mmHg
- The airways should be suctioned to ensure patency of the airway:
- Suctioning may occur through an open or closed circuit suction catheter.
- Routine suctioning is not recommended as this may lead to complications such as:
- Desaturation
- Arrhythmia
- Bronchospasm
- Cough
- Entry of secretions into the lower respiratory tract
- The endotracheal tube insertion depth varies by gender and is measured from the lower incisors:
- In males: 23cm
- In females: 21cm
- The tube is affixed in place using tape to prevent accidental extubation or further downward movement toward the main bronchus.
Types of Mechanical Ventilation
Positive pressure and negative pressure ventilation
- There are two ways in which a pressure gradient may be created to allow air into the lungs:[7][8][3]
Controlled and patient-initiated ventilation
- Ventilatory support may be controlled or patient-initiated:
- Controlled ventilation will deliver support independent of the patient's respiratory efforts
- Patient-controlled ventilation allows ventilation to be delivered in sync with the patient's own spontaneous breathing. In this type of ventilation, the patient's breathing is detected through pressure and airflow trigger mechanisms.
Pressure-targeted and volume-targeted ventilation
- With positive pressure ventilation, pressure or volume may be an independent variable:
- In volume-targeted ventilation, the tidal volume is set by the physician or respiratory assistant, the pressure in this case is a dependent variable.
- This means that airway pressure is the result of a set tidal volume and inspiratory volume, along with the patient's lung compliance, resistance and muscular activity.
- In pressure-targeted ventilation, airway pressure is set, and the volume is dependent.
- The tidal volume in this scenario is a result of inspiratory time, along with the patient's lung compliance, resistance and muscular activity.
- In volume-targeted ventilation, the tidal volume is set by the physician or respiratory assistant, the pressure in this case is a dependent variable.
Ventilator Modes
Ventilation modes include:[9][10][11][12][13][14]
- Pressure support ventilation (PSV)
- It may be described as patient-initiated and pressure-targeted ventilation.
- Patients with unstable respiratory drives should not be put on this mode; as the patient's respiratory efforts change, bronchospasm and varying degrees of auto–positive end-expiratory pressure (auto-PEEP) may ensue.
- Intermittent mandatory ventilation (IMV)
- This type of ventilation delivers mandatory breaths at a set frequency, tidal volume, and inspiratory flow rate.
- The patient may still breathe at their own will between the breaths delivered from the machine, and the machine may respond to those breaths.
- However, IMV has the disadvantage of possibly causing dynamic hyperinflation.
- This ventilator has since been improved to deliver breathes that are in sync with the patient's own spontaneous breathing efforts and is known as synchronized IMV or SIMV.
- Assist-control ventilation
- A fixed tidal volume and inspiratory flow rate is set, regardless of the rate of respiration.
- Simultaneously, a backup rate is set that delivers a minimum number of breaths per minute.
- In this way, if the patient does not meet the minimum amount of breaths per minute set, then the machine will take over.
- Volume-control mode
- In this type of ventilation, the respiratory rate, tidal volume, and inspiratory flow rate are fixed.
- Heavily sedated and/or paralyzed patients are recommended for this ventilation mode.
- Pressure-control mode
- In this type of ventilation, the airway pressure is raised and then set by a fixed period per minute.
- A physician or respiratory therapist may also set the inspiratory-to-expiratory (I:E) ratio or the inspiratory time.
- Heavily sedated and/or paralyzed patients are recommended for this ventilation mode.
- Pressure-control inverse-ratio ventilation (PCIRV)
- This ventialtion mode is a variation of pressure-control ventilation.
- The difference between simple pressure-control ventilation and pressure-control inverse-ratio ventilation is:
- Inspiration is set to be longer than expiration
- The I:E ratio doesn't exceed 3:1.
Ventilator-induced Lung Injury
- Mechanical ventilation may cause a range of lung injuries, namely those that caused by excessive airway pressures, known as a barotrauma.[15][16]
- Barotrauma includes:
- Pneumothorax
- Pneumomediastinum
- Subcutaneous and pulmonary interstitial emphysema
- Also pulmonary edema may occur as a result of injury to the lung parenchyma and altered permeability of the microcirculation.
- Barotrauma includes:
- In severely ill patients, the signs of barotrauma may not be noticeable, the earliest signs may include:
- Deep sulcus sign
- Anterior air collection in the cardiophrenic angle
References
- ↑ Frat JP, Thille AW, Mercat A, Girault C, Ragot S, Perbet S, Prat G, Boulain T, Morawiec E, Cottereau A, Devaquet J, Nseir S, Razazi K, Mira JP, Argaud L, Chakarian JC, Ricard JD, Wittebole X, Chevalier S, Herbland A, Fartoukh M, Constantin JM, Tonnelier JM, Pierrot M, Mathonnet A, Béduneau G, Delétage-Métreau C, Richard JC, Brochard L, Robert R (June 2015). "High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure". N. Engl. J. Med. 372 (23): 2185–96. doi:10.1056/NEJMoa1503326. PMID 25981908.
- ↑ Davidson AC, Banham S, Elliott M, Kennedy D, Gelder C, Glossop A, Church AC, Creagh-Brown B, Dodd JW, Felton T, Foëx B, Mansfield L, McDonnell L, Parker R, Patterson CM, Sovani M, Thomas L (April 2016). "BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults". Thorax. 71 Suppl 2: ii1–35. doi:10.1136/thoraxjnl-2015-208209. PMID 26976648.
- ↑ 3.0 3.1 Confalonieri M, Garuti G, Cattaruzza MS, Osborn JF, Antonelli M, Conti G, Kodric M, Resta O, Marchese S, Gregoretti C, Rossi A (February 2005). "A chart of failure risk for noninvasive ventilation in patients with COPD exacerbation". Eur. Respir. J. 25 (2): 348–55. doi:10.1183/09031936.05.00085304. PMID 15684302.
- ↑ 4.0 4.1 Phua J, Kong K, Lee KH, Shen L, Lim TK (April 2005). "Noninvasive ventilation in hypercapnic acute respiratory failure due to chronic obstructive pulmonary disease vs. other conditions: effectiveness and predictors of failure". Intensive Care Med. 31 (4): 533–9. doi:10.1007/s00134-005-2582-8. PMID 15742175.
- ↑ Slutsky AS (December 1993). "Mechanical ventilation. American College of Chest Physicians' Consensus Conference". Chest. 104 (6): 1833–59. PMID 8252973.
- ↑ Tobin MJ, Perez W, Guenther SM, Lodato RF, Dantzker DR (August 1987). "Does rib cage-abdominal paradox signify respiratory muscle fatigue?". J. Appl. Physiol. 63 (2): 851–60. doi:10.1152/jappl.1987.63.2.851. PMID 3654445.
- ↑ Shorr AF, Sun X, Johannes RS, Yaitanes A, Tabak YP (November 2011). "Validation of a novel risk score for severity of illness in acute exacerbations of COPD". Chest. 140 (5): 1177–1183. doi:10.1378/chest.10-3035. PMID 21527510.
- ↑ Tabak YP, Sun X, Johannes RS, Gupta V, Shorr AF (September 2009). "Mortality and need for mechanical ventilation in acute exacerbations of chronic obstructive pulmonary disease: development and validation of a simple risk score". Arch. Intern. Med. 169 (17): 1595–602. doi:10.1001/archinternmed.2009.270. PMID 19786679.
- ↑ Leung P, Jubran A, Tobin MJ (June 1997). "Comparison of assisted ventilator modes on triggering, patient effort, and dyspnea". Am. J. Respir. Crit. Care Med. 155 (6): 1940–8. doi:10.1164/ajrccm.155.6.9196100. PMID 9196100.
- ↑ Tobin MJ, Jubran A, Laghi F (April 2001). "Patient-ventilator interaction". Am. J. Respir. Crit. Care Med. 163 (5): 1059–63. doi:10.1164/ajrccm.163.5.2005125. PMID 11316635.
- ↑ Ward ME, Corbeil C, Gibbons W, Newman S, Macklem PT (July 1988). "Optimization of respiratory muscle relaxation during mechanical ventilation". Anesthesiology. 69 (1): 29–35. PMID 3389564.
- ↑ Marini JJ, Smith TC, Lamb VJ (November 1988). "External work output and force generation during synchronized intermittent mechanical ventilation. Effect of machine assistance on breathing effort". Am. Rev. Respir. Dis. 138 (5): 1169–79. doi:10.1164/ajrccm/138.5.1169. PMID 3202477.
- ↑ Imsand C, Feihl F, Perret C, Fitting JW (January 1994). "Regulation of inspiratory neuromuscular output during synchronized intermittent mechanical ventilation". Anesthesiology. 80 (1): 13–22. PMID 8291702.
- ↑ Jubran A, Van de Graaff WB, Tobin MJ (July 1995). "Variability of patient-ventilator interaction with pressure support ventilation in patients with chronic obstructive pulmonary disease". Am. J. Respir. Crit. Care Med. 152 (1): 129–36. doi:10.1164/ajrccm.152.1.7599811. PMID 7599811.
- ↑ Petrof BJ, Legaré M, Goldberg P, Milic-Emili J, Gottfried SB (February 1990). "Continuous positive airway pressure reduces work of breathing and dyspnea during weaning from mechanical ventilation in severe chronic obstructive pulmonary disease". Am. Rev. Respir. Dis. 141 (2): 281–9. doi:10.1164/ajrccm/141.2.281. PMID 2405757.
- ↑ MacIntyre NR, Cheng KC, McConnell R (January 1997). "Applied PEEP during pressure support reduces the inspiratory threshold load of intrinsic PEEP". Chest. 111 (1): 188–93. PMID 8996015.