Usefulness of cardiac parasympathetic index in CPAP‐treated patients with obstructive sleep apnea: A preliminary study

Abstract

Cardiac autonomic indexes, including cardiac parasympathetic index and cardiac sympathetic index, have been reported to accurately identify patients with sleep disorders such as obstructive sleep apnea. Our study aimed to assess cardiac autonomic indexes in patients with obstructive sleep apnea before and during a single full‐night continuous positive airway pressure therapy using a combined approach. Our simultaneous heart rate variability‐polysomnographic study included 16 never‐treated obstructive sleep apnea patients. Two patients dropped out. Patients underwent combined recordings in two consecutive days, at baseline and during a single full‐night of acute continuous positive airway pressure treatment. We calculated cardiac parasympathetic index and cardiac sympathetic index as night/day ratio for high‐frequency and low‐frequency heart rate variability spectral components, respectively. Continuous positive airway pressure treatment significantly reduced cardiac autonomic indexes values in comparison with baseline values (cardiac parasympathetic index: p < .0001; cardiac sympathetic index: p = .001). After acute continuous positive airway pressure treatment, the percentage of decrease of cardiac parasympathetic index was greater than that of cardiac sympathetic index (51.02 ± 15.72 versus 34.64 ± 26.93). A positive statistical correlation was also found between decrease of cardiac parasympathetic index and decrease of apnea–hypopnea index after continuous positive airway pressure (p < .001). This study improves the knowledge on cardiac autonomic modulation during acute continuous positive airway pressure therapy in obstructive sleep apnea. Our results demonstrate that both autonomic indexes decreased significantly after a single‐night of acute continuous positive airway pressure therapy. Cardiac parasympathetic index more than cardiac sympathetic index was related to decrease of apnea–hypopnea index after continuous positive airway pressure therapy, thus representing a potential help in everyday clinical practice.

Acute Effect of Positive Airway Pressure on Heart Rate Variability in Obstructive Sleep Apnea

“…Previous studies have examined the effect of CPAP on sympathetic hyperactivity in OSA patients, and repeatedly demonstrated a significant reduction in LF during both acute CPAP treatment [21,25,27] and long-term CPAP treatment [18,21,24]. In a prospective longitudinal study, HRV was analyzed during the first night of CPAP treatment and after 2 years of CPAP treatment in 30 patients with moderate to severe OSA [21].…”

“…An increase in parasympathetic activity may be linked to an increase in hydraulic pressure, which could be initiated by the carotid aortic chemoreceptor in response to hypoxemia [38]. Patients with OSA displayed a noteworthy decrease in HF with CPAP treatment compared to their baseline measurements [23,25]. Our finding of a significant decrease in HF during CPAP titration in moderate to severe OSA patients accords well with those of previous studies, suggesting that CPAP treatment may improve HRV by way of reducing not only sympathetic activity but also parasympathetic activity.…”

“…There is mounting evidence that continuous positive airway pressure (CPAP) treatment improves HRV in patients with OSA [18,21,[23][24][25][26][27][28]. A significant decrease in sympathetic hyperactivity, as assessed by HRV, was demonstrated both on the first night of CPAP titration [21,25,27] and after long-term CPAP treatment [18,21,24,28]. However, several studies reported no significant change in sympathetic activity after CPAP treatment [29][30][31].…”