During RSI, bag-mask ventilation before laryngoscopy improves oxygenation: PreVent

  • N Engl J Med

  • curated by Jenny Blair, MD
  • Clinical Essentials
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  • During endotracheal intubation, bag-mask ventilation before laryngoscopy leads to better oxygen saturation and fewer desaturations, without additional adverse events.
  • Number needed to treat to avoid severe hypoxemia: 9.
  • Editorial: "findings provide a strong suggestion that the practice [of bag-mask ventilation after induction] is not harmful.”

Why this matters

  • For patients undergoing rapid sequence intubation (RSI), ventilating during pre-laryngoscopy delay is debated, with concerns about hypoxia rivaling concerns about aspiration.

Key results

  • Bag-mask vs no-ventilation groups:
    • Lowest O2 saturation: 96% (interquartile range [IQR], 87%-99%) vs 93% (IQR, 81%-99%); P=.01.
    • Severe hypoxemia (saturation
    • Similar rates of aspiration, new opacity on chest x-ray. 

Study design

  • Randomized multicenter unblinded pragmatic PreVent (n=401). 
  • Critically ill ICU adults undergoing tracheal intubation and induction were randomly assigned to:
    • Ventilation with bag-mask device, or 
    • No ventilation between induction and laryngoscopy. 
  • Outcome: lowest oxygen saturation between induction and 2 minutes after intubation. 
  • Funding: NIH.


  • Patients with high aspiration risk excluded.
  • Unknown if results generalize to emergency departments, prehospital setting.
  • Underpowered to assess aspiration risk.
  • Bag-mask group received more bag-mask ventilation during induction, potentially increasing oxygen reserve.
  • Not designed to assess patient-centered outcomes.

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