Effect of heart failure and physical training on the acute ventilatory response to hypoxia at rest and during exercise.
Barlow CW., Qayyum MS., Davey PP., Paterson DF., Robbins PA.
We studied the acute ventilatory response to hypoxia (AHVR) in 10 patients with chronic heart failure (CHF) and in 10 subjects with normal left 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 oxygen consumption. The AHVR was not significantly different between the patients 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 during constant light exercise (2.37 +/- 0.48 vs. 2.86 +/- 0.55 litres/min/% arterial desaturation). Both groups showed evidence of improved physical fitness after training with increases in maximum oxygen consumption 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 trained 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 litres/min/% arterial desaturation) or during constant light exercise (2.52 +/- 0.69 vs. 2.24 +/- 0.37 litres/min/% arterial desaturation). Moreover, these responses did not differ from those in the untrained state (see above). The AHVR increased during exercise compared with rest in both groups (p < 0.05). The AHVR is not substantially altered in patients with CHF compared to subjects with NLVF. Physical training may reduce ventilation during exercise, but it has relatively little or no effect on the AHVR. However, exercise increases the AHVR in patients with CHF, as it does in normals.