Does bag mask ventilation before endotracheal intubation help?
Does bag-mask ventilation (BMV) during tracheal intubation of critically ill adults prevent hypoxemia without increasing the risk of aspiration following administration of an induction agent- until the time by which the intubation happens?
Bag-mask ventilation (BMV) and endotracheal intubation (ETI) are the two alternatives available for airway management during the advanced cardiac life support phase of cardiopulmonary resuscitation of patients with out-of-hospital cardiorespiratory arrest.
Currently >1.5 million patients undergo ETI annually in US alone. However, while saving life and organ ~ 2 out of 5 intubations in the intensive care unit (ICU) are still complicated by hypoxemia, which may lead to cardiac arrest and death. The reason is that rapid-sequence induction involves an inherent delay of 45-90 seconds between medication administration (sedation, induction agent and a neuro-muscular blocking agent) and initiation of laryngoscopy.
The question is whether providing positive-pressure ventilation with a BMV during this interval prevents hypoxemia without increasing any complication. This issue has been debated for last 5 decades because while BMV may help in reducing hypoxemia, there is an inherent risk of gastric or oropharyngeal aspiration and therefore risk-benefit ratio of this strategy needs to be addressed.
The process of endotracheal intubation
Currently the practice of ETI involves,
- Period of pre-oxygenation- There are four ways to provide pre-oxygenation with 100% inspired oxygen in any patient
-
- Provide 5 to 10 deep breaths (vital capacity)
- Provide 4 minutes of regular breaths (tidal volume)
- Provide apneic oxygenation
- BMV
- This is followed by the administration of an induction agent (such as propofol or etomidate) and a neuromuscular blocking agent (succinylcholine, rocuronium etc).
- Rapid-sequence intubation, within 60 seconds of induction.
The point under discussion is whether positive pressure ventilation with a bag-mask device (BMV) during tracheal intubation of critically ill adults would prevent hypoxemia without increasing the risk of aspiration following the administration of induction agent (until the time by which the intubation happens).
PreVent Trial
PreVent trial, a multicenter, randomised trial which was recently published in NEJM sought to investigate the effects of BMV on hypoxemia during tracheal intubation of critically ill adults.
- The primary outcome was the lowest oxygen saturation observed during the interval between induction and 2 minutes after tracheal intubation
- The secondary outcome was the incidence of severe hypoxemia, defined as an oxygen saturation of <80%; it was found that patients receiving BMV had higher oxygen saturations (96% in the BMV group vs. 93% in the no-ventilation group; P = 0.01) and a lower incidence of severe hypoxemia (10.9% in the BMV group vs. 22.8% in the no-ventilation group; relative risk, 0.48; 95% confidence interval [CI], 0.30 to 0.77) than those receiving no ventilation
Furthermore the concern regarding aspiration was also laid to rest; aspiration occurring in 2.5% cases in the BMV group vs. 4.0% in the no-ventilation group (P = 0.41).
Thus all the critically ill patients undergoing endo-tracheal intubation in the in-hospital setting should undergo bag mask ventilation before the intubation is actually performed.
