Victor Hoffstein

Postural Changes in Respiratory Airflow Pressure and Resistance in Nasal, Hypopharyngeal, and Pharyngeal Airway in Normal Subjects

We investigated the effect of posture on nasal and pharyngeal resistance 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 pharyngeal resistance was approximately four to six times lower than the nasal resistance. Only pharyngeal resistance was significantly increased 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 recumbency and to 0.05 ± 0.04 Pa/mL per second in left lateral recumbency. Mean nasal and pharyngeal resistances doubled upon assumption of a supine posture, but this difference was not statistically significant. There was no significant difference in pharyngeal resistance beween inspiration and expiration. Finally, there was a strong linear relationship between pharyngeal pressure and pharyngeal resistance (r = .98, p < .0001). We concluded that in normal awake subjects 1) pharyngeal resistance increases with assumption of a supine posture, 2) the walls of the pharynx are not compliant enough to alter their resistance in response to inspiratory and expiratory pressure changes, and 3) it may be possible to infer pharyngeal resistance from measurements of pressure alone, without measurement of airflow.

Upper airway pressures in snorers and nonsnorers during wakefulness and sleep

OBJECTIVEnTo compare upper airway pressures in snorers and nonsnorers during sleep and wakefulness.nnnDESIGNnCase series of snorers and nonsnoring controls.nnnSETTINGnSleep clinic of a university hospital.nnnMETHODSnWe used open catheters to measure differential nasopharyngeal and hypopharyngeal pressures in 8 nonapneic snorers with excessive daytime tiredness and 10 healthy nonsnoring controls. Measurements were performed during sleep (with the mouth taped to ensure exclusively nasal breathing) and wakefulness. When awake, the subjects were either seated (with the head neutral, flexed, extended, or rotated) or recumbent (dorsal and lateral positions).nnnMAIN OUTCOME MEASURESnComparison of pressures within the group as a function of body position and between the groups as a function of snoring.nnnRESULTSnDifferential nasal and pharyngeal pressures were similar in seated snorers and nonsnorers independently of head position. Assumption of recumbency resulted in significantly increased pharyngeal pressures in nonsnorers (26 +/- 18 Pa seated vs. 52 +/- 46 Pa recumbent, p < .05) and snorers (50 +/- 35 Pa seated vs. 93 +/- 38 recumbent, p < .01). The increase was higher in snorers than nonsnorers. During snoring, sleep differential pharyngeal pressures in snorers were markedly increased compared to quiet sleep (567 +/- 450 Pa during snoring epochs vs. 117 +/- 82 Pa during nonsnoring epochs, p < .01).nnnCONCLUSIONSnCompared to nonsnorers, recumbent nonapneic snorers have elevated differential pharyngeal pressures indicative of increased upper airway resistance and reduced airway patency; this is present during wakefulness and sleep.