[Relationship between lung function and nocturnal hypoxemia in patients with obstructive sleep apnea syndrome].

OBJECTIVE

To explore the relationship between the changes of lung function resulted from position changes and obesity, and nocturnal hypoxemia in patients with obstructive sleep apnea syndrome.

METHOD

34 patients with obstructive sleep apnea syndrome were detected by polysomnography with lung function and blood gas analysis in sitting and supine positions during wake, and the relationship between results of lung function and blood gas analysis, IBW% to the AI, and < 90% T (percentage of the duration of SaO2 below 90% to total sleep time) was analyzed.

RESULT

The mean age of the patients was 44 +/- 13 years. The AI was 36 +/- 22 time.hour-1. On changing from sitting to supine position, PaO2, VC%, ERV, FRC, FRC%, RV%, TLC% decreased significantly, especially ERV and FRC%, which decreased 47% and 29% respectively. AI had positive correlation with VC% (r = 0.477, P < 0.01) and TLC% (r = 0.443, P < 0.01) in supine position, < 90% T had negative correlation with PaO2(r = -0.479, P < 0.01) and ERV (r = -0.416, P < 0.05) in sitting position. The IBW% had negative correlation with VC% in sitting (r = -0.547, P < 0.01) and supine position (r = -0.491, P < 0.01). IBW% also had negative correlation with ERV in sitting (r = -0.523, P < 0.01) and supine (r = -0.413, P < 0.01) position and FRC (r = -0.402, P < 0.05) in sitting position. The IBW% had positive correlation with the < 90% T(r = 0.514, P < 0.01).

CONCLUSION

These results suggest that positional changes and obesity have effects on lung function in patients with OSAS, and lead to the deterioration of hypoxemia during apnea.