Multiscale entropic assessment of autonomic dysfunction in patients with obstructive sleep apnea and therapeutic impact of continuous positive airway pressure treatment

Abstract

ObjectiveObstructive sleep apnea (OSA) is an independent risk factor for cardiovascular disease because of its associated autonomic nervous and vascular regulatory dysfunctions. We tested the hypothesis that the multiscale entropy (MSE) approach to heart rate variability analysis may be used for evaluating OSA severity through simultaneous assessment of these abnormalities. MethodsA total of 147 subjects were divided into four groups according to apnea–hypopnea index (AHI) from polysomnography (PSG): Snoring without OSA (5 > AHI, n = 31), mild (5 ≤ AHI < 15, n = 31), moderate (15 ≤ AHI < 30, n = 41), and severe (AHI ≥ 30, n = 44) OSA. Of the patients, 41 receiving continuous positive airway pressure (CPAP) treatment were included for comparison. For each subject, two segments of electrocardiographic (ECG) signals (both at stage N2) were used for R-R interval (RRI) analysis, including a 10-minute recording 10 minutes after falling asleep (ie, early phase) and another 10-minute segment at 3 hours (ie, late phase). Heart rate variability as reflected in changes in RRI between the two segments was assessed with small-scale multiscale entropy index (MEISS, sum of sample entropy from time scale from 1 to 5) and large-scale multiscale entropy index (MEILS, scale from 6 to 10). ResultsIncrease in MEILS in the late phase of sleep was noted in both the normal snoring and CPAP groups (P < 0.01). Although the moderate OSA group exhibited MEISS drop in the late phase (P < 0.02), both MEISS and MEILS decreased in the late phase in the severe OSA group (P < 0.001, P < 0.02). However, no differences were noted in mild OSA subjects in both parameters. ConclusionThe results demonstrated significant severity-dependent deterioration in autonomic and vascular regulatory function in patients with OSA as reflected in the reductions in MEISS and MEILS, respectively, and notable improvement after CPAP treatment. The MEI obtainable through PSG may indicate not only OSA severity and physiological status but also therapeutic outcome for OSA patients.