Respiratory muscle function and exercise intolerance in heart failure.

Inspiratory muscle weakness (IMW) is prevalent in patients with chronic heart failure (CHF) caused by left ventricular systolic dysfunction, which contributes to reduced exercise capacity and the presence of dyspnea during daily activities. Inspiratory muscle strength (estimated by maximal inspiratory pressure) has independent prognostic value in CHF. Overall, the results of trials with inspiratory muscle training (IMT) indicate that this intervention improves exercise capacity and quality of life, particularly in patients with CHF and IMW. Some benefit from IMT may be accounted for by the attenuation of the inspiratory muscle metaboreflex. Moreover, IMT results in improved cardiovascular responses to exercise and to those obtained with standard aerobic training. These findings suggest that routine screening for IMW is advisable in patients with CHF, and specific IMT and/or aerobic training are of practical value in the management of these patients.