Abstract
BackgroundThe 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 methodsA 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.ResultsAPAP 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.ConclusionNocturnal 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.
Highlights
Positive airway pressure (PAP) is the standard treatment for patients with moderate-to-severe obstructive sleep apnea (OSA) − a sleep-related breathing disorder (SRBD) characterized by episodic complete or partial upper airway occlusion during sleep [1]
Time-domain indexes included the average length between each QRS complex, the standard deviation of all RR intervals (SDNN), the mean of the standard deviation of all RR intervals for all 5 min segments (SDNN index), the square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD), the number of pairs of adjacent RR intervals differing by more than 50 ms in the entire analysis interval (NN50 count), the NN50 count divided by the total number of all RR intervals [NN50 of total heart rate (HR) (%)], standard deviation of average NN interval (SDANN), and the total number of RR intervals divided by the maximum height of the histogram excluding boundaries (HRV triangular index)
A total of 25 (22 males and three females) patients with obstructive sleep apnea syndrome (OSAS) with a mean age of 49.52±15.69 years and mean BMI of 39.14±8.00 kg/m2 were included in this study; four patients had moderate OSAS, whereas the remaining 21 patients had severe OSAS
Summary
Positive airway pressure (PAP) is the standard treatment for patients with moderate-to-severe obstructive sleep apnea (OSA) − a sleep-related breathing disorder (SRBD) characterized by episodic complete or partial upper airway occlusion during sleep [1]. The respiratory event-related cyclic hypoxemia and arousal characteristic of OSA causes dysregulation in the autonomic nervous system (ANS) in the form of enhanced sympathetic activity, and such impairment is thought to be the substrate necessary for heart rate variability (HRV) and the development of cardiac arrhythmias [12,13,14,15,16,17,18,19]. The cyclic hypoxemia and arousal characteristic of obstructive sleep apnea (OSA) causes dysregulation in the autonomic nervous system (ANS) resulting in cardiac rhythm disturbances. 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
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