POSTURAL CHANGES IN RESPIRATORY AIR-FLOW PRESSURE AND RESISTANCE IN NASAL, HYPOPHARYNGEAL, AND PHARYNGEAL AIRWAY IN NORMAL SUBJECTS

We investigated the effect of posture on nasal and pharyngeal resistan ce in 12 healthy subjects studied during wakefulness. Airway pressure and airflow were measured with subjects seated and in dorsal and left lateral recumbency, during inspiration and expiration. We found that p haryngeal resistance was approximately four to six times lower than th e nasal resistance. Only pharyngeal resistance was significantly incre ased upon assumption of a supine posture, from 0.02 +/- 0.01 Pa/mL per second when seated to 0.06 +/- 0.05 Pa/mL per second in dorsal recumb ency and to 0.05 +/- 0.04 Pa/mL per second in left lateral recumbency. Mean nasal and pharyngeal resistances doubled upon assumption of a su pine posture, but this difference was not statistically significant. T here was no significant difference in pharyngeal resistance beween ins piration and expiration. Finally, there was a strong linear relationsh ip between pharyngeal pressure and pharyngeal resistance (r =.98, p <. 0001). We concluded that in normal awake subjects 1) pharyngeal resist ance increases with assumption of a supine posture, 2) the walls of th e pharynx are not compliant enough to alter their resistance in respon se to inspiratory and expiratory pressure changes, and 3) it may be po ssible to infer pharyngeal resistance from measurements of pressure al one, without measurement of airflow.