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FRC is key in obesity.
Additional Information
Functional residual capacity (FRC) is the volume left in the lungs at the end of a tidal volume breath. One way to think about FRC is as a reservoir of oxygen that continues to supply gas exchange even after a patient stops breathing (i.e. after RSI). The rate of oxygen consumption (VO2) determines how quickly this reservoir gets depleted (safe apnea time). FRC is significantly decreased in obesity. VO2 is also higher in obese patients. Both of these factors decrease the length of safe apnea time in obese patients.
Consequently, pre-oxygenation with NIPPV and/or BVM with PEEP is key to increasing FRC and as a result, the safe apnea time while intubating obese patients.
References
Russotto V, Casey JD, Myatra SN, et al. Airway management in critically ill patients with obesity. Intensive Care Med. 2026;52(6):1256-1268. doi:10.1007/s00134-026-08454-x