• Guangfa Wang, Maosen Chen, Jian Bian, and Bing He.
• Dept. of Pulmonary Medicine, The 1st Hospital, Peking University, Beijing 100034, China.
• Zhonghua Jie He He Hu Xi Za Zhi. 2002 Apr 1;25(4):199-203.

ObjectiveTo investigate the instant effects of continuous positive airway pressure (CPAP) on EEG spectral power changes in obstructive sleep apnea syndrome (OSAS) patients.Methods26 OSAS patients were included. The diagnosis was made by polysomnography (PSG). The CPAP pressure was titrated during the first night of therapy. During another night in two weeks after the diagnostic study, the patients accepted the whole night CPAP treatment while PSG was monitored. C(3)/A(2) was analyzed by using fast fourier transform (FFT). Spectral edge frequency (SEF), median power frequency (MPF), alpha index, beta index, delta index and theta; index during CPAP therapy were compared with those parameters before treatment.ResultsSleep architecture was improved significantly during therapy. The ratio of slow wave sleep (SWS) deficiency reduced from 19/26 to 10/26 (P = 0.0250). There were more times of REM sleep (1.81 +/- 0.25) vs (2.65 +/- 0.17) (P = 0.023). A significant increase of total SWS time over total sleep time (TST) (2.9 +/- 1.1)% vs (6.0 +/- 1.2)% (P = 0.043) was observed, as well as total REM sleep time over TST (12.0 +/- 1.7)% vs (21.1 +/- 1.6)% (P = 0.001). Total stage I and stage II time over TST reduced greatly [from (85.1 +/- 2.1)% to (73.0 +/- 1.9)% (P = 0.000)]. So did the number of wake after sleep onset [from (12.2 +/- 1.3) to (9.4 +/- 1.0) (P = 0.033). The total number of stage I, stage II decreased from (46.4 +/- 4.2) to (36.7 +/- 2.4), but the difference was not significant (P = 0.051). Spectral analysis of EEG showed a decrease of mean SEF in total sleep period (TSP) (14.4 +/- 0.4) Hz vs (13.6 +/- 0.3) Hz (P = 0.003), stage I (15.4 +/- 0.4) Hz vs (14.8 +/- 0.5) Hz (P = 0.040), stage II (13.7 +/- 0.3) Hz vs (12.8 +/- 0.3) Hz (P = 0.007) and REM sleep (15.0 +/- 0.5) Hz vs (13.8 +/- 0.6) Hz (P = 0.028), as well as 0.018 and 0.047]. delta index was increased in stage II sleep (P = 0.030) but not in other sleep stages. CPAP had no obvious influence on theta; index (P > 0.05). The median of SEF in TSP (14 vs 13) Hz (P = 0.0056), stage I (16 vs 15) Hz (P = 0.04) and stage II (13 vs 13) Hz (P = 0.002). Changes of MPF were not as significant as that of SEF, but mean MPF was decreased during TSP and stage IV. CPAP significantly reduced mean beta index [from (8.4 +/- 0.5)% to (7.5 +/- 0.5)% (P = 0.012)] in total sleep period as well as in stage I, II, III and IV sleep (P < 0.015). alpha index in TSP, stage III and IV sleep was decreased significantly (P = 0.045, 0.018 and 0.047 respectively). delta index was increased in stage II sleep (P = 0.030) but not in other sleep stages. CPAP had no obvious influence on theta; index (P > 0.05).ConclusionsCPAP has an acute effect in improving the sleep architecture and EEG power spectrum. The SEF, beta index and alpha index are more sensitive than MPF, delta index and theta; index to CPAP therapy. These changes may be related to the recovery of cerebral function in OSAS patients after CPAP therapy. More studies need to be conducted to investigate how these changes happen and their relation to daytime cerebral function.

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