The Egyptian Journal of Bronchology (Nov 2017)
Nocturnal heart rate variability in obstructive sleep apnea syndrome: effect of automatic positive airway pressure
Abstract
Abstract Background The cyclic hypoxemia and arousal characteristic of obstructive sleep apnea (OSA) causes dysregulation in the autonomic nervous system (ANS) resulting in cardiac rhythm disturbances. Positive airway pressure therapy in OSA results in ANS regulation. This study aimed at investigating the effects of automatic positive airway pressure (APAP) over nocturnal heart rate variability (HRV) in OSA and to further identify this effect in hypertensive versus normotensive OSA patients. Patients and methods A total of 25 patients (four with moderate and 21 with severe OSA) were included (male/ female: 22/3; mean age 49.52±15.69 years). Patients were subdivided into two groups: 13 (52%) normotensive and 12 (48%) hypertensive patients. Two overnight sleep studies with polysomnographic-based nocturnal HRV were carried out: the first study was diagnostic, whereas the second one was an APAP titration study. Results APAP results in significant reduction in most of time and frequency-domain indexes [except for standard deviation of average NN interval (SDANN, P=0.106), HRV triangular index (HRV TI, P=0.057), and high-frequency power (HF, P=0.109)]; RR interval (P=0.024), standard deviation of all RR intervals (SDNN, P=0.012), mean of the standard deviation of all RR intervals for all 5-min segments (SDNN Index, P=0.009), square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD, P=0.002), number of pairs of adjacent RR intervals differing by more than 50 ms in the entire analysis interval (NN50 count, P=0.004), NN50 count divided by the total number of all RR intervals (%NN50, P=0.001), total power (P=0.010), very low-frequency power (VLF, P=0.018), low-frequency power (LF, P=0.008), and low frequency/high frequency (LF/HF, P=0.012). HRV did not differ significantly between the two groups either before or after APAP; however, most of the time-domain and frequency-domain HRV indexes decreased significantly with APAP in the hypertensive group. Conclusion Nocturnal HRV improved with APAP in OSA. APAP was more beneficial in terms of ANS regulation in OSA patients with coexisting hypertension than normotensive OSA patients.
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