| Abstract: | Cala, S. J., P. Sliwinski, M. G. Cosio, and R. J. Kimoff.Effect of topical upper airway anesthesia on apnea duration through the night in obstructive sleep apnea. J. Appl.Physiol. 81(6): 2618-2626, 1996. It haspreviously been reported that the duration of obstructive apneasincreases from the beginning to the end of the night (M. Charbonneau,J. M. Marin, A. Olha, R. J. Kimoff, R. D. Levy, and M. Cosio.Chest 106: 1695-1701, 1994). The purpose of this study wasto test the hypothesis that stimulation of upper airway (UA) sensoryreceptors during obstructed inspiratory efforts contributes to arousaland apnea termination and that a progressive attenuation of thismechanism through the night contributes to apnea lengthening. Westudied seven patients (six men, one woman) with severe obstructivesleep apnea (apnea-hypopnea index = 93 ± 26 events/h) during twoconsecutive nights of polysomnographic monitoring. On one night (randomorder), we performed topical UA anesthesia with 0.2% tetracaine and onthe control night, sham anesthesia. We measured apnea duration,esophageal pressure (Pes) during apneas, and apneicO2 desaturation. Consistent withprevious findings, apnea duration, number of efforts per apnea, andpeak Pes at end apnea increased from the beginning to the end of the control nights. UA anesthesia produced a significant increase in apneaduration at the beginning of the night but no change in apnea length atthe end of the night. Peak Pes and the rate of increase in Pes duringthe anesthesia nights were greater than during control nights, but therate of increase in Pes was similar for the beginning and end of thecontrol and anesthesia nights. These findings suggest that UA sensoryreceptors play a role in mediating apnea termination at the beginningof the night but that the contribution of these receptors diminishes asthe night progresses such that greater inspiratory efforts arerequired to trigger arousal, leading to apnea prolongation. |
