The effect of specific inspiratory muscle training on the sensation of dyspnea and exercise tolerance in patients with congestive heart failure

Background and Aim: It has been previously shown that the inspiratory muscles of patients with congestive heart failure (CHF) are weaker than those of normal persons. This weakness may contribute to the dyspnea and limit exercise capacity in these patients. To evaluate the effect of specific inspiratory muscle training (SIMT) on inspiratory muscle performance, lung function, dyspnea and exercise capacity in patients with moderate heart failure. Patients and methods: 20 patients with CHF (NYHA junctional class II-III) were recruited for the study and were randomized into 2 groups: 10 patients consisted the study group and received SIMT and 10 patients were assigned to the control group and got sham training. Subjects in both groups trained daily, for 1/2 hour, 6 times/week, for 3 months. The subjects started breathing at a resistance equal to 15% of their PImax for one week and the resistance was then increased incrementally to 60%. Spirometry, inspiratory muscle strength (PImax at RV) and endurace (the relationship between PmPeak and PImax), the 12-min walk test and peak VO2 were performed before, and at the end of the training period. Results: All patients in the training group showed an increase in all the inspiratory muscle strength (mean PImax increased from 46.5±4.7 to 63.6±4.0 cm H₂O, p<0.005), and endurance (mean PmPeak/PImax from 478±3.6 to 67.7±1.7 %, p<0.05) while it remained unchanged in the control group. This was associated with a small, but significant increase in FVC, a significant increase in the distance walked (458±29 to 562±32 m, p<0.01) and an improvement in the dyspnea index score, in the training group. No statistically significant change in the mean peak VO2 was noted in both groups. Conclusions: SIMT resulted in increased inspiratory muscle strength and endurance. This increase in inspiratory muscle performance was associated with decreased dyspnea, increase in submaximal exercise capacity. SIMT may prove to be a complimentary therapy in patients with CHF.