NOCTURNAL OXYGEN AND HYPERCAPNIC VENTILATORY RESPONSE IN PATIENTS WITH CONGESTIVE-HEART-FAILURE

Patients with congestive heart failure and Cheyne-Stokes respiration h ave a low arterial oxygen saturation, especially during sleep, which c an be increased by breathing oxygen. Chronic alterations in blood gase s are known to modulate the hypercapnic ventilatory response (HCVR). W e therefore evaluated whether the HCVR is influenced by nocturnal nasa l oxygen in patients with heart failure and Cheyne-Stokes respiration. Twenty patients with chronic congestive heart failure and a left vent ricular ejection fraction less than or equal to 35% (mean 18.3% +/- SD 6.0% as well as 25 healthy control subjects were studied. The patient s 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 e ach week resting ventilation and HCVR were evaluated by the rebreathin g technique. Breathing oxygen during the night for 1 week increased th e 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 f rom 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) aft er nocturnal oxygen (P=0.019). There were no significant changes with nocturnal oxygen in resting minute ventilation, respiratory rate or en d-tidal PCO2. We conclude that nocturnal nasal oxygen reduces HCVR in patients with congestive heart failure and Cheyne-Stokes respiration.