Effects of CPAP therapy on the sympathovagal balance and arterial stiffness in obstructive sleep apnea.

Objective: Increased arterial stiffness and sympathovagal imbalance are noted in patients with obstructive sleep apnea (OSA). It has been thought that continuous positive airway pressure (CPAP) therapy can have beneficial effects on the vascular function in such cases. However, it is not yet clear whether the improvement of sympathovagal balance by CPAP might be related to reduction of the arterial stiffness, independent of changes in the blood pressure.
Methods: In 50 consecutive eligible patients with OSA (apnea-hypopnea index>/=20/hour) receiving CPAP therapy, the brachial-ankle pulse wave velocity (baPWV), heart rate variability (LF, HF and LF/HF ratio), baroreceptor sensitivity (BRS), plasma levels of C-reactive protein (CRP), and endothelial function as assessed by changes in the forearm blood flow before and after reactive hyperemia (END) were measured before and after 3-months' CPAP therapy.
Results: Significant decrease of the LF/HF ratio, plasma levels of CRP, baPWV and heart rate were observed after 3 months' CPAP therapy. The change in the baPWV following 3-months' CPAP therapy was significantly correlated with the change in the LF/HF ratio and mean blood pressure (MBP), but not with that of the BRS, CRP or END after the therapy. Multivariate linear regression analysis demonstrated a significant correlation between the change in the LF/HF ratio and that in the baPWV (beta=0.305, p=0.041), independent of the changes in the MBP, plasma CRP levels and heart rate.
Conclusions: Improvement of the sympathovagal balance by CPAP therapy may be significantly related to decreased stiffness of the central to middle-sized arteries, independent of the changes in the blood pressure and vascular endothelial status.
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