BALTIMORE – Continuous positive airway pressure (CPAP) may supersede supplemental oxygen and patient education for improving one key marker of cardiac electrophysiological autonomic function during sleep, but supplemental oxygen may have the upper hand in improving a second key electrophysiological biomarker, according to results of a multicenter, randomized clinical trial presented at the annual meeting of the Associated Professional Sleep Societies.
Dr. Jenie George
“Based on these findings, it appears that there are opposing alterations in both frequency and time domain in heart rate variability indices in the CPAP versus oxygen groups,” said Jenie George, MD, of the Cleveland Clinic.
The study evaluated 3-month outcomes of frequency-based heart rate variability (HRV) indices obtained with ECG from sleep studies in 203 patients with obstructive sleep apnea and increased cardiovascular risk in the Heart Biomarker Elevation in Apnea Treatment (HeartBEAT) trial. The interventions were either CPAP, supplemental oxygen, or healthy lifestyle education. Dr. George noted that HRV is a noninvasive tool to evaluate autonomic function by quantifying changes in intervals between sinus beats during sleep.
On the high-frequency power index, patients on CPAP had a 9% reduction versus a 19% increase for those on supplemental oxygen, Dr. George said. However for the low frequency to high frequency ratio, the CPAP group had a 4% increase, whereas the oxygen group had a 34% reduction.
The increase of low frequency to high frequency ratio in the CPAP group is a reflection of sympathovagal balance – the ratio between low-frequency and high-frequency powers – while the changes in high-frequency power in the CPAP patients reflect changes in sinoatrial node electrophysiological function, Dr. George said.
Strengths of the study were its use of data from a large clinical trial, careful preprocessing of ECG data, and consideration of the influence of oxygen in sleep apnea and of confounding influences, such as medications. Limitations of the study, Dr. George noted, include the absence of sleep-wake data and acknowledgment that HRV measures are accepted surrogates of autonomic imbalance but that they are not direct measures.
The next steps for the current research, Dr. George said, include an analysis of how respiratory events influence HRV indices in CPAP and supplemental oxygen. Future trials should be designed to examine how the two interventions affect direct measures of autonomic function and consider a longer follow-up duration, she said.
Dr. George had no financial relationships to disclose. The trial received support from the National Heart, Lung, and Blood Institute and the National Center for Research Resources.
SOURCE: George J et al. Sleep 2018, Abstract 0444.