When possible, preoxygenation with face mask oxy-gen should precede all airway management inter-ventions. Oxygen is delivered by mask for several minutes prior to anesthetic induction. In this way, the functional residual capacity, the patient’s oxy-gen reserve, is purged of nitrogen. Up to 90% of the normal FRC of 2 L following preoxygenation is filled with O 2. Considering the normal oxygen demand of 200–250 mL/min, the preoxygenated patient may have a 5–8 min oxygen reserve. Increasing the duration of apnea without desaturation improves safety, if ventilation following anesthetic induction is delayed. Conditions that increase oxygen demand (eg, sepsis, pregnancy) and decrease FRC (eg, mor-bid obesity, pregnancy) reduce the apneic period before desaturation ensues.
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