Heart Rate Variability in Obstructive Sleep Apnea.

Abstract

Introduction: Obstructive Sleep Apnea (OSA) is characterized by repeated episodes of upper airway obstruction leading to increased airway resistance and respiratory effort, producing oxygen desaturation, hypercapnia and central nervous system arousal. The intermittent hypoxemia and carbon-dioxide retention is responsible for the changes in autonomic and hemodynamic responses to sleep. Heart rate variability (HRV) is a marker of autonomic activity and can be analyzed using time-domain and frequency-domain methods. This study was undertaken to compare the HRV in patients with Obstructive Sleep Apnea Syndrome (OSAS) and normal subjects. Methods: Heart rate variability in 30 controls (Group I) and 30 patients with Obstructive Sleep Apnea Syndrome (Group II) aged 35-45 yrs was studied by using electrocardiographic data obtained during Polysomnography. Low frequency (LF) power, High frequency (HF) power and Low frequency/ High frequency ratio (LF/HF) were analyzed using frequency-domain analysis. Results: There was a significant difference (p <0.001) in LF power and LF/HF ratio of patients with OSAS when compared to the controls, with the values of the OSAS patients being higher, indicating a strong sympathetic activity and a significant difference (p <0.001) in HF power, with the values of the OSAS patients being lower, suggesting parasympathetic blunting. Conclusion: In our study, there was evidence of increased Sympathetic activity and a Parasympathetic attenuation in patients with Obstructive Sleep Apnea. Further studies can evaluate the usefulness of HRV indices for the non-invasive screening of asymptomatic patients suspected to have OSAS.