Sleep and posture.

Computer-assisted open catheter studies of 10 healthy, nose-breathing men in dorsal and in lateral recumbent sleep demonstrated stable intrasubject transpharyngeal differential pressures and airflow resistances. They averaged 19.6 Pa (+/- standard deviation [SD] 11.9) and 0.103 Pa/cm3 per second (+/- SD 0.065) in the dorsal posture and stage II sleep during quiet breathing and were not significantly different in the lateral posture or in stage I sleep. Five subjects were snorers, and their pharyngeal airflow pressures and resistances increased substantially during quiet breathing on assumption of recumbency and much more in sleep. In the 5 subjects who were nonsnorers, postural changes were not significant and sleep increases were moderate. During snoring, transpharyngeal pressures and resistances increased even further, averaging 188 Pa and 1.02 Pa/cm3 per second for the whole group. Transpharyngeal differential pressures and hypopharyngeal transmural pressures frequently exceeded 300 Pa in inspiration and in expiration during periods of snoring. Yet, transpharyngeal differential pressures and resistances did not reveal appreciable differences between phases that would indicate compliant change of pharyngeal cross section. Breathing frequency was unchanged, but ventilation was significantly diminished at elevated upper airway resistances (P < .01). Transpharyngeal resistances and differential pressures varied independently from widely differing nasal resistances. As with our earlier studies, pressure measurements alone clearly demonstrated breathing patterns and events.