Objective: 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
Design: Blinded subjects underwent
two maximal incremental exercise tests in random order on an upright
bicycle ergometer: one with and one without added dead space.
Setting: Tertiary-care university teaching hospital.
Subjects: Seven patients with stable chronic heart failure
(mean ± SEM left ventricular ejection fraction, 27 ± 3%).
Results: 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
Conclusion: 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.