Objective: To evaluate the effect of long-term treatment with continuous positive airway pressure (CPAP) on the heart rate variability (HRV) of obstructive sleep apnea (OSA) patients.
Material and Method: Patients with moderate to severe OSA who had never used CPAP treatment were enrolled. Short recording HRV analysis was performed at baseline then at one, three, and six months after CPAP treatment. The measurement included low frequency HRV (LF), high frequency HRV (HF), low frequency to high frequency ratio (LHR), and standard deviation of R-R intervals (SDNN). All domains were measured both during spontaneous and deep breathing.
Results: There were 10 patients in the present study, all were men with the mean age of 45 years, mean body mass index 29.3 kg/m2, mean apnea-hypopnea index 60.9 events/hour, and mean average CPAP usage 4.8 hours/night. The HRV showed no significant change after one and three months of CPAP treatment. At 6 months, the only significant change was the SDNN measured after deep breathing (28.80 + 9.83 vs. 34.43 + 14.23 millisecond, p = 0.032).
Conclusion: One aspect of heart rate variability in moderate to severe obstructive sleep apnea patients was improved after six month’s continuous positive airway pressure treatment.

Keywords: Obstructive sleep apnea, Continuous positive airway pressure, Heart rate variability