To investigate the possible association between residual sleepiness (RS) and central sleep apnea events in patients with obstructive sleep apnea syndrome (OSAS) following continuous positive airway pressure (CPAP) treatment, as well as the effects of adaptive servo-ventilation (ASV) on RS.
Following correct application of CPAP treatment and exclusion of other sleepiness-associated disorders, 50 patients with moderate-to-severe OSAS were recruited, including 26 patients with RS (RS group) and 24 patients without RS (control group). The treatment of one month's auto-CPAP (AutoCPAP) followed by one week ASV with autoCS2 ventilator was performed. Comparisons were made separately before treatment, on AutoCPAP and ASV treatments in both groups of the following parameters: polysomnographic parameters including central sleep apnea index (CSAI), micro-arousal index (MAI), etc; daytime Epworth sleepiness score (ESS), and possibly sleepiness-associated factor, i.e., plasma tumor necrosis factor-alpha (TNF-alpha). Plasma TNF-alpha levels were measured by enzyme linked immunosorbent assay (ELISA). t test and single factor analysis of variances were used for comparison between two groups and within group respectively. q test was used for couple comparison within group at 3 different stages. Pearson correlation test was performed for correlation analysis between 2 variables.
Before treatment there was no significant difference between two groups in apnea hypopnea index (AHI), MAI, minimal pulse oxygen saturation (minSpO2), ESS and plasma TNF-alpha levels (t: 0.630, 1.223, 0.691, 0.764 and 0.19 2, all P > 0.05). However, the CSAI in RS group was significantly higher than that in the control group [(7.19 +/- 1.75) times/h vs (3.37 +/- 1.04) times/h, t = 4.097, P < 0.05)]. After 1 month's AutoCPAP treatment there was a significant decrease in AHI, CSAI, MAI and ESS in both groups (q: 0.87-112.55, all P < 0.05), but CSAI, MAI and ESS in the RS group than those in the control group [CSAI: (7.19 +/- 1.75) times/h vs (3.37 +/- 1.04) times/h, t = 9.473, P < 0.05; MAI: (9.00 +/- 1.95) times/h vs (2.36 +/- 0.66) times/h, t = 14.385, P < 0.05; ESS: 9.54 +/- 0.51 vs 5.42 +/- 1.32, t = 2.857, P < 0.05). On one weeks' ASV treatment there was such a further significant decrease in CSAI, MAI and daytime ESS in the RS group and the control group. In addition, compared with the plasma TNF-alpha level before treatment in the RS group, there was no statistical difference on AutoCPAP treatment but a significant decrease on ASV treatment. Plasma TNF-alpha levels were positively correlated with ESS (r = 0.503, P < 0.01) and MAI (r = 0.545, P < 0.01).
RS in OSAS patients following CPAP treatment was associated with their CSAI before and during treatment. By effectively eliminating CSA events with ASV, RS was significantly improved, which suggested that ASV was effective in treatment of RS. The elevation of plasma TNF-alpha level was correlated with the severity of sleepiness and may be involved in the pathogenesis of RS.