Inspiratory Muscle Weakness and Dyspnea in Chronic Heart Failure

Dyspnea is a common, disabling symptom in chronic heart failure, yet the underlying mechanisms remain unknown. The respiratory muscle pump is composed of skeletal muscles whose strength directly influences the pump's performance. Respiratory muscle weakness is important in the dyspnea experienced by some patients with pulmonary disease; however, the role of the respiratory muscle pump in the dyspnea of chronic heart failure has not previously been examined. To assess respiratory muscle strength and its relation to dyspnea during daily activity, we measured maximum inspiratory and expiratory mouth pressures as indices of respiratory muscle strength and the baseline dyspnea index in nine stable, chronic cardiac pump failure patients who had no evidence of primary lung disease, and in nine age- and sex-matched healthy control subjects. The chronic heart failure patients, when compared with their matched control subjects, had reduced inspiratory and expiratory muscle strength, and both inspiratory and expirat...