Objective: To study the characteristics of pharyngeal respiratory pressure before and after onset of airflow obstruction events in obstructive sleep apnea hypopnea syndrome (OSAHS).
Methods: The respiratory pressure in nasopharynx, oropharynx, and hypopharynx in 8 patients with OSAHS and 9 normal persons were evaluated through catheter manometer. Base on mean respiratory pressure and the ratio of negative respiratory pressure persistent time, the characteristics of pharyngeal respiratory pressure before and after the event onset were analyzed.
Results: During sleep, the pharyngeal respiratory pressure in normal persons had similar and periodical wave shape. The ratio of negative respiratory pressure persistent time was less than 0.5. In patients with OSAHS, when the obstruction of airflow happened, the pharyngeal respiratory pressure fluctuated violently, the wave shape became irregular, and the negative expiratory pressure was evident. The mean respiratory pressure was 1 to 2 order of magnitude larger than in normal persons, even reaching -990 Pa. The ratio of persistent negative pressure time was larger than normal. During the intermittent period, the wave shape of pharyngeal respiratory pressure was regular and periodical, the pressure wave shape was different from onset of obstruction. However, in the intermittent period, the mean respiratory pressure, the ratio of negative respiratory pressure persistent time, and other characteristics were still statistically different from normal persons (P < 0.05).
Conclusions: During the intermittent period, the pharyngeal respiratory pressure in patients with OSAHS during sleep is basically different from the pharyngeal respiratory pressure in normal person. The characteristics of pharyngeal respiratory pressure in intermittent period indicates that both structural and functional abnormalities in pharyngeal cavity in patients with OSAHS, which affect the respiratory airflow during sleep are inherent. The effects are more prominent during onset period, suggesting that the characteristics of the pharyngeal pressure of breathing during the onset period will be more important to the mechanism of airflow obstruction.