EFFECT OF HEART-FAILURE AND PHYSICAL-TRAINING ON THE ACUTE VENTILATORY RESPONSE TO HYPOXIA AT REST AND DURING EXERCISE

We studied the acute ventilatory response to hypoxia (AHVR) in 10 pati ents with chronic heart failure (CHF) and in 10 subjects with normal l eft ventricular function (NLVF) before and after 8 weeks of home-based physical training. Subjects were studied at rest and during constant cycle exercise at a work rate equivalent to 40% of their maximum oxyge n consumption. The AHVR was not significantly different between the pa tients with CHF and those with NLVF either at rest (1.32 +/- 0.19 vs. 1.63 +/- 0.20 litres/min/% arterial desaturation; mean +/- SE) or duri ng constant light exercise (2.37 +/- 0.48 vs. 2.86 +/- 0.55 litres/min /% arterial desaturation). Both groups showed evidence of improved phy sical fitness after training with increases in maximum oxygen consumpt ion of 11 +/- 2.7% (p < 0.01) for the group with NLVF and of 8 +/- 3.2 % (p < 0.05) for the group with CHF. Values for the AHVR in the traine d state were not significantly different between the patients with CHF and those with NLVF either at rest (1.23 +/- 0.24 vs. 1.63 +/- 0.22 l itres/min/% arterial desaturation) or during constant light exercise ( 2.52 +/- 0.69 vs. 2.24 +/- 0.37 litres/min/% arterial desaturation). M oreover, these responses did not differ from those in the untrained st ate (see above). The AHVR increased during exercise compared with rest in both groups (p < 0.05). The AHVR is not substantially altered in p atients with CHF compared to subjects with NLVF. Physical training may reduce ventilation during exercise, but it has relatively little or n o effect on the AHVR. However, exercise increases the AHVR in patients with CHF, as it does in normals.