Role of Respiratory Function in Exercise Limitation in Chronic Heart Failure

To test the hypothesis that respiratory function contributes to limit maximal exercise performance in patients with chronic heart failure by using the technique of dead space loading during exercise. Blinded subjects underwent two maximal incremental exercise tests in random order on an upright bicycle ergometer: one with and one without added dead space. Tertiary-care university teaching hospital. Seven patients with stable chronic heart failure (mean ± SEM left ventricular ejection fraction, 27 ± 3%). Subjects were able to significantly increase their peak minute ventilation during exercise with added dead space when compared with control exercise (57.4 ± 5.9 vs 50.0 ± 5.6 L/min; p < 0.05). Peak oxygen uptake, workload, heart rate, and exercise duration were not significantly different between the added dead space and control tests. Breathing pattern was significantly deeper and slower at matched levels of ventilation during exercise with added dead space. Because patients with chronic heart failure had significant ventilatory reserve at the end of exercise and were able to further increase their maximal minute ventilation, we conclude that respiratory function does not contribute to limitation of exercise in patients with chronic heart failure.