Sustained effect of continuous positive airway pressure on baroreflex sensitivity in congestive heart failure patients with obstructive sleep apnea.

BACKGROUND: Patients with either heart failure or obstructive sleep apnea have a reduced baroreflex sensitivity for heart rate, a sign of poor prognosis. We previously demonstrated that nocturnal application of continuous positive airway pressure to heart failure patients with obstructive sleep apnea increased baroreflex sensitivity acutely, but it is not known whether these effects persist into wakefulness. OBJECTIVE: To determine whether treating obstructive sleep apnea in heart failure patients with continuous positive airway pressure improves baroreflex sensitivity during wakefulness. METHODS: Spontaneous baroreflex sensitivity was assessed during wakefulness in 33 heart failure patients (left ventricular ejection fraction < or = 45%) with obstructive sleep apnea (apnea-hypopnea index > or = 20). Subsequently, baroreflex sensitivity was reassessed 1 month after patients were randomly allocated to nocturnal continuous positive airway pressure treatment or no treatment (control). RESULTS: Compared with the 14 control patients, the 19 continuous positive airway pressure-treated patients experienced a greater increase in baroreflex sensitivity [median, (25%, 75%)] [from 5.4 (2.2, 8.3) to 7.9 (4.4, 9.4) ms/mmHg; P = 0.01] and left ventricular ejection fraction (P < 0.001). In addition, daytime systolic blood pressure and heart rate decreased more in the continuous positive airway pressure group (from 122 +/- 15 to 113 +/- 12 mmHg; P = 0.02, and from 66 +/- 8 to 62 +/- 8 bpm; P < 0.001, respectively) than in the control group. CONCLUSION: Treatment of coexisting obstructive sleep apnea by continuous positive airway pressure in heart failure patients improves baroreflex sensitivity during wakefulness in addition to improving left ventricular ejection fraction and lowering blood pressure and heart rate. These data indicate that the improved autonomic regulation of heart rate in heart failure patients treated for obstructive sleep apnea during sleep persists into wakefulness.

Continuous positive airway pressure increases heart rate variability in heart failure patients with obstructive sleep apnoea.

Patients with heart failure or OSA (obstructive sleep apnoea) have reduced HF-HRV (high-frequency heart rate variability), indicating reduced cardiac vagal modulation, a marker of poor prognosis. CPAP (continuous positive airway pressure) abolishes OSA in patients with heart failure, but effects on daytime HF-HRV have not been determined. We hypothesized that, in patients with heart failure, treatment of coexisting OSA by CPAP would increase morning HF-HRV. In 19 patients with heart failure (left ventricular ejection fraction <45%) and OSA (>/=20 apnoeas and hypopnoeas/h of sleep), HF-HRV was quantified before and 1 month after randomization to a control or CPAP-treated group. In the control group (n=7), there were no changes in HF-HRV over the 1 month study during wakefulness in the morning. In the CPAP-treated group (n=12) HF-HRV increased significantly during wakefulness in the morning [from 2.43+/-0.55 to 2.82+/-0.50 log(ms(2)/Hz); P=0.002] due to an increase in transfer function between changes in lung volume and changes in HF-HRV (92.37+/-96.03 to 219.07+/-177.14 ms/l; P=0.01). In conclusion, treatment of coexisting OSA by nocturnal CPAP in patients with heart failure increases HF-HRV during morning wakefulness, indicating improved vagal modulation of heart rate. This may contribute to improved prognosis.