Benefit of selective respiratory muscle training on exercise capacity in patients with chronic congestive heart failure

Background: Diminished respiratory muscle strength and endurance have been demonstrated in patients with heart failure. This may contribute to exertional dyspnea and reduced exercise capacity in these patients. The purpose of this study was to investigate whether selective respiratory muscle training could alleviate dyspnea and improve exercise performance in patients with chronic congestive heart failure. Methods and Results: Fourteen patients with chronic heart failure (left ventricular ejection fraction, 22±9%) were enrolled in a supervised respiratory muscle training program. This consisted of three weekly sessions of isocapnic hyperpnea at maximal sustainable ventilatory capacity, resistive breathing, and strength training. Maximum sustainable ventilatory capacity, maximum voluntary ventilation, maximal inspiratory and expiratory pressures, peak V̇O₂, and the 6-minute walk test were measured before (pre) and after (post) 3 months of training. Eight patients completed the training program. Respiratory muscle endurance was improved with training, as evidenced by increases in maximal sustainable ventilatory capacity (pre, 48.6±10.7 versus post, 76.9±14.5 L/min; P<.05) and in maximal voluntary ventilation (pre, 100±36 versus post, 115±39 L/min; P<.05). Respiratory muscle strength was also increased with training as maximal inspiratory (pre, 64±31 versus post, 78±33 cm H₂O; P<.01) and expiratory (pre, 94±30 versus post, 133±53 cm H₂O; P<.001) pressures rose. Submaximal and maximal exercise capacity were significantly improved with selective respiratory muscle training as the 6-minute walk (pre, 1101±351 versus post, 1421±328 ft; P<.001) and peak exercise V̇O₂ (pre, 11.4±3.3 versus post, 13.3±2.7 mL · kg^-1 · min^-1; P<.05) both significantly increased. Dyspnea during activities of daily living was subjectively improved in the majority of trained patients. Dyspnea quantified by the Borg scale was significantly reduced during progressive isocapnic hyperpnea but not during bicycle exercise. No statistically significant improvement in maximal sustainable ventilatory capacity, maximum voluntary ventilation, maximal inspiratory or expiratory mouth pressures, 6-minute walk, or peak V̇O₂ was observed in the 6 patients who did not complete the training program. Conclusions: Selective respiratory muscle training improves respiratory muscle endurance and strength, with an enhancement of submaximal and maximal exercise capacity in patients with heart failure. Dyspnea during activities of daily living was subjectively improved in the majority of trained patients.