UMEM Educational Pearls

Preoxygenation in Critically Ill Patients

  • Achieving adequate preoxygenation and denitrogenation prior to intubating critically ill patients can be challenging.
  • Critically ill patients have physiologic alterations (i.e., derangements in oxygen consumption, anemia, reduced cardiac output, air space disease) that can markedly reduce safe apnea time.
  • For patients with significant air space disease and shunt physiology, noninvasive ventilation (NIV) can decrease shunt fraction, increase functional residual capacity, improve PaO2, and lengthen safe apnea time.
  • Importantly, NIV should be used for at least 3 minutes to achieve improvements in alveolar recruitment.
  • It is also important to remove NIV just prior to larygnoscopy, as alveoli will begin to derecruit when NIV is removed.


Mosier JM, Hypes CD, Sackles JC. Understanding preoxygenation and apneic oxygenation during intubation in the critically ill. Intensive Care Med. 2017; 43:226-8.