Author: David Rosenberg, M.D. Educational Pearls Preoxygenation is done before rapid sequence intubation, and should be done even if SaO2 is at 100%. Preoxygenation is done to fill the lungs with oxygen rather than ambient air, which is only 20% O2. While the patient is paralyzed, the O2-filled lungs will continue to oxygenate venous blood, buying you more time for intubation.   BiPAP is an effective tool for pre-oxygenation. References: https://lifeinthefastlane.com/ccc/preoxygenation/