Ventilatory assistance improves exercise endurance in stable congestive heart failure

We postulated that ventilatory assistance during exercise would improve cardiopulmonary function, relieve exertional symptoms, and increase exercise endurance (T-lim) in patients with chronic congestive heart failure (CHF). After baseline pulmonary function tests, 12 stable patients with advanced CHF (ejection fraction, 24 +/- 3% [mean +/- SEM]) performed constant-load exercise tests at approximately 60% of their predicted maximal oxygen consumption ((V)over dot o(2)max) while breathing each of control (1 cm H2O), continuous positive airway pressure optimized to the maximal tolerable level (CPAP = 4.8 +/- 0.2 cm H2O) or inspiratory pressure support (PS = 4.8 +/- 0.2 cm H2O), in randomized order. Measurements during exercise included cardioventilatory responses, esophageal pressure (Pes), and Borg ratings of dyspnea and leg discomfort (LD). At a standardized time near end-exercise, PS and CPAP reduced the work of breathing per minute by 39 +/- 8 and 25 +/- 4%, respectively (p < 0.01). In response to PS: T-lim increased by 2.8 +/- 0.8 min or 43 +/- 14% (p < 0.01); slopes of LD-time, (V)over dot o(2)-time, (V)over dot co(2)-time, and tidal Pes-time decreased by 24 +/- 10, 20 +/- 11, 28 +/- 8, and 44 +/- 9%, respectively (p < 0.05); dyspnea and other cardioventilatory parameters did not change. CPAP did not significantly alter measured exercise responses. The increase in Tli, was explained primarily by the decrease in LD-time slopes (r = -0.71, p < 0.001) which, in turn, correlated with the reductions in (V)over dot o(2)-time (r = 0.61, p < 0.01) and tidal Pes-time (r = 0.52, p < 0.01). in conclusion, ventilatory muscle unloading with PS reduced exertional leg discomfort and increased exercise endurance in patients with stable advanced CHF.