To determine the influence of changes in nasal pressure (Pn) on airflow mechanics in the upper airway, we examined the effect of elevations in Pn on upper airway resistance and critical pressure (Pcrit) during stage I/II sleep in six patients with obstructive sleep apnea. When Pn was elevated above a Pcrit, periodic occlusions of the upper airway were eliminated and inspiratory airflow limitation was demonstrated by the finding that inspiratory airflow (V̇I) became maximal (V̇I(max)) and independent of fluctuations in hypopharyngeal pressure (Php) when Php fell below a specific Php (Php'). As Pn was elevated, V̇I vs. Php demonstrated 1) marked decreases in early and late inspiratory resistances from 75.9 ± 34.7 and 54.6 ± 19.0 to 8.0 ± 1.7 and 7.6 ± 1.6 cmH2O·l-1·s (P < 0.05), respectively, and 2) increases in early and late inspiratory Php' to levels that exceeded Pcrit by 3.0 ± 0.6 and 3.1 ± 0.7 cmH2O, respectively, at the highest level of Pn applied (P < 0.01). This latter findings suggests that elevations in Pn result in increases in Pcrit. We suggest that elevations in Pn produce distinct alterations in upper airway resistance and collapsibility, which may influence oppositely the level of airflow through the upper airway during sleep.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of applied physiology|
|State||Published - Jan 1 1989|
ASJC Scopus subject areas
- Physiology (medical)