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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(ms2/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. [ABSTRACT FROM AUTHOR]

Background. Patients with end-stage renal disease (ESRD) have a reduced exercise capacity as assessed by peak oxygen uptake (VO2peak). Nocturnal haemodialysis (NHD) augments uraemic clearance and vascular responsiveness to nitric oxide and lowers blood pressure (BP) and peripheral resistance. Methods. To assess the impact of NHD on exercise duration and capacity, 13 consecutive ESRD patients [age: 41 ± 3; (mean ± SEM)] and healthy normal subjects (n = 14) matched for age and body mass index exercised to peak effort (VO2peak) as determined by open-circuit spirometry during a graded cycle ergometer test with a ramp increase in work rate (by 17 watts/min). Results. Exercise was performed before, 2 and 3–6 months after conversion from conventional haemodialysis (CHD) (3 sessions per week; 4 h per session) to NHD (5–6 sessions per week; 6–8 h per session). Exercise duration increased progressively [from 617 ± 50 (CHD) to 634 ± 47 (NHD 2 months) to 682 ± 55 [NHD 3–6 months], P = 0.03) as did exercise capacity, expressed as percent of predicted (based on age, sex and body size) VO2peak, [from 66 ± 8 (CHD) to 72 ± 6 (NHD 2 months) to 75 ± 6% (NHD 3–6 months), P Conclusion. Enhanced uraemia control by NHD improved both exercise duration and capacity. When coupled with augmented uraemia management, an increase in physical activity, perhaps due to more effective oxygen delivery or improved muscle metabolism, has the potential to improve the quality of life of patients with ESRD. [ABSTRACT FROM AUTHOR]