Preoxygenation of the morbidly obese with obstructive sleep apnea.

Morbid obesity is associated with a more rapid decrease in oxygen saturation during apnea following induction of anesthesia, compared to patients who have normal weight1. This is particularly hazardous as morbid obesity, complicated by obstructive sleep apnea, may be associated with an increased risk of difficult tracheal intubation and difficult face mask ventilation2. These morbidly obese patients, with a body mass index >35 kg/m2, a history of obstructive sleep apnea, a neck circumference >17 inch, a short thyromental distance, and a Mallampati class III, suggest difficult mask ventilation, difficult tracheal intubation, as well as rapid oxyhemoglobin desatruation during apnea (Fig. 1).