Role of respiratory function in exercise limitation in chronic heart failure

Objective: To test the hypothesis that respiratory function contributes to limit maximal exercise performance in patients with chronic heart failure b y using the technique of dead space loading during exercise. Design: Blinded subjects underwent two maximal incremental exercise tests i n random order on an upright bicycle ergometer: one with and one without ad ded dead space. Setting: Tertiary-care university teaching hospital. Subjects: Seven patients with stable chronic heart failure (mean +/- SEM le ft ventricular ejection fraction, 27 +/- 3%). Results: Subjects were able to significantly increase their peak minute ven tilation during exercise with added dead space when compared with control e xercise (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 differe nt between the added dead space and control rests, Breathing pattern was si gnificantly deeper and slower at matched levels of ventilation during exerc ise with added dead space. Conclusion: Because patients with chronic heart failure had significant ven tilatory reserve at the end of exercise and were able to further increase t heir maximal minute ventilation, we conclude that respiratory function does not contribute to limitation of exercise in patients with chronic heart fa ilure.