To the Editor:—
Preoxygenation is a simple but vitally important method to expand the time after induction of anesthesia and paralysis until the patient is endangered by hypoxia. 1This additional time may be lifesaving in “cannot ventilate–cannot intubate” situations. Although it had been discussed by the American Society of Anesthesiologists Task Force on the Management of the Difficult Airway to include a statement on “routine” preoxygenation of every patient—if possible—before induction of general anesthesia (J. L. Benumof, M.D., written communication with W. S., September 2000), the current version of the difficult airway algorithm 2contains no such statement. Anesthesiologists often argue that, for the patient, the mask represents a significant discomfort and that many patients find preoxygenation objectionable.
We recently have tested this hypothesis in 100 patients using an anonymous standard quality control inquiry with additional questions about oxygen mask tolerance. Simultaneously, 76 anesthesiologists were interviewed anonymously about their estimation of patient discomfort during preoxygenation.
Patients and anesthesiologists estimated the discomfort on a continuous scale from 1 (no discomfort) to 10 (maximum discomfort). The results are shown in figure 1. Preoperatively, the patients expected a moderate discomfort caused by the mask (median 2), whereas postoperatively, the patients mentioned no discomfort (median 1, P < 0.01 vs. preoperatively, Wilcoxon signed rank test). The anesthesiologists overestimated patient discomfort caused by the mask significantly, with a median of 5 (P < 0.01 vs. preoperative and postoperative estimation of patient discomfort, Krustal–Wallis one-way analysis of variance followed by the Dunn multiple comparison procedure). Patient discomfort during preoxygenation was not different from the discomfort during other established procedures, such as the placement of an intravenous line (P = 0.3).
Only very few patients experience significant discomfort caused by the mask during preoxygenation. A marked overestimation of the average patient discomfort by the anesthesiologist may contribute to the reluctance sometimes seen to use routine preoxygenation.