Heart rate variability and cardio-respiratory coupling during sleep in patients prior to bariatric surgery

Obesity is associated with increased cardiac risk of morbidly and mortality and for the development and progression of obstructive sleep apnea (OSA). Severity of obesity negatively affects the heart rate variability (HRV) in patients with indication for bariatric surgery (BS). The purpose of this study is to determine if the severity of obesity alters the autonomic cardiac regulation and the cardio-respiratory coupling during sleep using spectral analysis of HRV and respiration variability signals (RS) in patients prior to BS. Twenty-nine consecutive preoperative BS and ten subjects (controls) underwent polysomnography. The spectral and cross-spectral parameters of the HRV and RS were computed during different sleep stages (SS). Spectral analysis of the HRV and RV indicated lower respiration regularity during sleep and a lower HRV in obese patients (OP) during all SS when compared with controls (p < 0.05). Severely (SO) and super-obese patients (SOP) presented lower values of low frequency/high frequency (LF/HF) ratio and LF power during REM sleep and higher HF power (p < 0.05), while morbidly obese (MO) patients presented lower LF/HF ratio and LF power in SS-S2 and higher HF power when compared to controls (p < 0.05). The cross-spectral parameters showed that SOP presented lower percentage of tachogram power coherent with respiration in SS-S3 when compared to controls (p < 0.05). Patients prior to BS presented altered HRV and RV in all SS. SO, MO, and SOP presented altered cardio-respiratory coupling during sleep, and these alterations are related with severity of obesity and OSA parameters.