Axial CT measurements of the cross-sectional area of the oropharynx in adults with obstructive sleep apnea syndrome.

PURPOSE To determine whether narrowing of the oropharynx increases during relaxation in patients with severe obstructive sleep apnea syndrome. MATERIALS The study included 23 adult men in whom polysomnography had established a diagnosis of obstructive sleep apnea syndrome. Subjects had an average of 53 episodes of sleep apnea per hour, with each episode lasting 40 seconds or more. Oxygen saturation dropped an average of 22% during sleep. Hypnotic relaxation was induced in all patients, and high-resolution CT scans with sagittal and coronal reconstruction of the oropharynx were obtained in the awake state and during the relaxation state using the same parameters. The cross-sectional area of the oropharynx was measured in a minimum of 10 CT axial sections in each case. RESULTS In all patients, the narrowest cross-sectional area of the oropharynx was smaller during hypnotic relaxation than in the awake state. The average difference between both measures was 42%. In the awake state, the measurements ranged from 15 to 55 mm2 (average, 38 mm2). During hypnotic relaxation, they ranged from 0 to 35 mm2. Oxygen saturation during hypnotic relaxation dropped in all patients from 9% to 17% (average, 14%). No episodes of sleep apnea were observed during hypnotic relaxation. CONCLUSIONS In patients with obstructive sleep apnea, airways were demonstrably smaller in diameter during hypnotic relaxation than during the awake state.