Changes in heart rate variability (HRV) in patients with severe
and moderate obstructive sleep apnea before and after acute
CPAP therapy during nocturnal polysomnography
Introduction: Obstructive sleep apnea is an important risk factor for cardiovascular disease.
Noninvasive positive pressure ventilation is the standard treatment of this disease, and it can
reduce mortality in patients. Dysfunction of the autonomic system is one of the reasons for an
increased risk of cardiovascular disease in these patients. The purpose of the present study was
to investigate the effect of positive airway pressure (PAP) therapy on heart rate variability (HRV)
indices. Methods: The study population was comprised of 55 patients, who underwent nocturnal
polysomnography for the diagnosis of obstructive sleep apnea and PAP titration on the same night.
The levels of continuous positive airway pressure (CPAP) and bilevel positive airway pressure were
adjusted to relieve obstructive sleep apnea, hypopnea, and desaturation. The patients’ heart changes
and cardiac characteristics were recorded before and after the start of routine CPAP therapy.
Finally, the cases’ sleep and polysomnography tests were analyzed and interpreted in collaboration
with a sleep specialist and their cardiac changes with the aid of a cardiologist before and after
treatment with CPAP. Results: The participants were 55 patients at a mean age of 57.04±12.9
years. There were 34 (61.8%) male and 21 (38.2%) female cases. PAP therapy on the same night
resulted in a decreased standard deviation of the N-N interval index (p=0.036) and a low-frequency
index (p=0.021), as well as increased high-frequency index (p<0.001) and low frequency / high
frequency ratios (p=0.008). Conclusion: Our findings indicate a relative improvement in the
activity of the autonomic system in patients with obstructive sleep apnea after 1 night of PAP
therapy. Overwhelming evidence suggests that improvement in the sympathetic balance can reduce
the risk of cardiovascular disease in patients