The effects of adaptive servo ventilation on cerebral vascular reactivity in patients with congestive heart failure and sleep-disordered breathing

Study Objective: Hypercapnic cerebral vascular reactivity (HCVR) is reduced in patients with congestive heart failure (CHF) and sleep-disordered breathing (SDB); this may be associated with an increased risk of stroke. We tested the hypothesis that reversal of SDB in CHF patients using adaptive servo ventilation (ASV) would increase morning HCVR. Design: Interventional, cross-over clinical study. Setting: Research sleep laboratory. Patients: Ten CHF patients with SDB, predominantly obstructive sleep apnea. Interventions: The HCVR was measured from the change in middle cerebral artery velocity, using pulsed Doppler ultrasound. HCVR was determined during the evening (before) and morning (after) 1 night of sleep on ASV and 1 night of spontaneous sleep (control). Measurements and Results: Compared with the control situation, ASV decreased the apnea-hypopnea index (group mean ± SEM, control: 48 ± 12, ASV: 4 ± 1 events per hour). HCVR was 23% lower in the morning, compared with the evening, on the control night (evening: 1.3 ± 0.2, morning: 1.0 ± 0.2 cm/sec per mm Hg, P <0.05) and 27% lower following the ASV night (evening: 1.5 ± 0.2, morning: 1.1 ± 0.2 cm/sec per mm Hg, P <0.05). The effect of ASV on the evening-to-morning reduction in HCVR was not significant, compared with the control night (0.02 cm/sec per mm Hg, 95% confidence interval: -0.28, 0.32 P = 0.89). Conclusions: In CHF patients with SDB, HCVR was reduced in the morning compared with the evening. However, removal of SDB for 1 night did not reverse the reduced HCVR. The relatively low morning HCVR could be linked with an increased risk of stroke.