The effects of nasal continuous positive airway pressure on platelet activation in obstructive sleep apnea syndrome

Objective: A case-controlled study to assess the effects of nasal continuous positive airway pressure (CPAP) on platelet activation in patients with obstructive sleep apnea (OSAS) syndrome. Methods: We recruited 65 patients with suspected OSAS for this study. Blood samples were taken with the patient in the supine position in the morning immediately after polysomnography, and 1 night and 3 months after the start of nasal CPAP therapy to measure an index of platelet activation (IPA(+)), which reflected both the quantity and quality of platelet activation. Significant OSAS was defined as an apnea-hypopnea index (AHI) of greater than or equal to 10 events per hour. Results: There were 42 patients with significant OSAS and 23 control subjects with AHI < 10 events per hour. The mean (+/- SD) age for the OSAS patients was 48 +/- 9 years, the mean body mass index was 30.7 +/- 4.8, the mean AHI was 47 +/- 25 events per hour, the mean arousal index (AI) was 37 23 events per hour, and the mean minimum arterial oxygen saturation was 74 +/- 11%. Following multiple linear regression analyses of the clinical and polysomnography parameters, AI was the independent factor that correlated best with the baseline IPA(+) (beta-coefficient, 0.386; p = 0.006). Following nasal CPAP treatment with a mean objective CPAP compliance of 3.9 +/- 1.9 h per night, there was a significant decrease in IPA(+) from 15.1 +/- 12.2 U (at baseline) to 12.2 +/- 5.2 U (p < 0.001) and 9.8 +/- 4.3 U (p = 0.005), respectively, after 1 night and 3 months, whereas no significant change was noted among the control subjects. Using univariate analysis of variance to compare the changes in IPA(+) between the two groups at 3 months with adjustment for the baseline value, nasal CPAP reduced IPA(+) by 5.63 (SE, 1.85), whereas IPA(+) increased in control subjects by 1.33 (SE, 1.27) [least-squared mean difference between groups, 3.34; 95% confidence interval, 0.42 to 6.26; p = 0.026]. Conclusions: OSAS, through repeated episodes of arousals, may lead to platelet activation, which can be reduced by nasal CPAP therapy.