Nocturnal oxygen and hypercapnic ventilatory response in patients with congestive heart failure

Patients with congestive heart failure and Cheyne-Stokes respiration have a low arterial oxygen saturation, especially during sleep, which can be increased by breathing oxygen. Chronic alterations in blood gases are known to modulate the hypercapnic ventilatory response (HCVR). We therefore evaluated whether the HCVR is influenced by nocturnal nasal oxygen in patients with heart failure and Cheyne-Stokes respiration. Twenty patients with chronic congestive heart failure and a left ventricular ejection fraction less than or equal to 35% (mean 18.3% +/- SD 6.0% as well as 25 healthy control subjects were studied. The patients were assigned to 1 week each of nocturnal nasal oxygen and room air with a flow of 41 min (-1) in a randomized cross-over fashion. After each week resting ventilation and HCVR were evaluated by the rebreathing technique. Breathing oxygen during the night for 1 week increased the basal nocturnal oxygen saturation from 92.5% 1.6% to 96.5% +/- 0.9% (P<0.000 01) and reduced Cheyne-Stokes respiration. HCVR was 1.22 +/- 0.90 1 min (-1) mmHg(-1) after nocturnal room air and did not differ from that in the control subjects (1.31 +/- 0.61 1 min (-1) mmHg (-1)). In the patients HCVR decreased to 0.91 +/- 0.521 min(-1) mmHg(-1) after nocturnal oxygen (P=0.019). There were no significant changes with nocturnal oxygen in resting minute ventilation, respiratory rate or end-tidal PCO2. We conclude that nocturnal nasal oxygen reduces HCVR in patients with congestive heart failure and Cheyne-Stokes respiration.