Objective: To evaluate the effects of continuous positive airway pressure (CPAP) on daytime sleepiness in patients with severe obstructive sleep apnea syndrome (OSAS).
Methods: Retrospective evaluations were performed for 70 consecutive patients at the medical sleep center, West China Hospital, Sichuan University from May 2013 to October 2013. They were all diagnosed with severe OSAS and underwent overnight CPAP titration. Their mean age and body mass index (BMI) were (42.7 ± 8.4) years and (29.2 ± 4.2) kg/m(2) respectively. The sleep structure, hypoxia and objective sleepiness was compared between baseline and CPAP titration. And correspondence analysis was performed between multiple sleep latency tests (MSLT) and other sleep and expiratory parameters.
Results: Comparing to the baseline polysomnogram (PSG) levels, CPAP titration significantly decreased apnea hypopnea index (AHI) ((4.4 ± 2.7) vs (67.7 ± 18.9)/h), significantly shortened the longest apnea time (24.0 (16.5, 29.6) vs 61.3(51.0, 74.8) s) and raised the lowest oxygen saturation ((84.8 ± 8.8)% vs (54.4 ± 18.7)%).Furthermore, the percentage of stage 3 (N3%) (18.2(12.5, 25.6)% vs 2.4 (0.1, 8.2)%), the percentage of stage rapid eye movement (REM) sleep (REM%) ((22.3 ± 7.7)% vs (12.7 ± 5.8)%) and sleep perception improved significantly (89.1(88.3, 91.2)% vs 82.7(82.7, 87.0)%, all P < 0.05).Furthermore, CPAP also significantly improved their mean sleep latency of multiple sleep latency test (MSLT) ((8.5 ± 3.8) vs (4.8 ± 2.3) min, P < 0.05); the mean sleep latency of MSLT was negatively correlated with AHI, the percentage of stage 1 (N1%) and the longest apnea (r = -0.501,-0.308,-0.309,-0.501, all P < 0.01); but positively correlated with REM%, N3%, mean oxygen saturation and minimal oxygen saturation during CPAP titration (r = 0.235,0.394,0.398,0.440, all P < 0.05).
Conclusion: CPAP significantly improves nocturnal oxygen desaturation, sleep architecture and objective sleepiness in patients with severe OSAS.