Background: 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. The respiratory muscles can be trained for both strength and endurance.
Hypothesis: The present study was designed 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.
Methods: Twenty patients with CHF (NYHA functional class II-III) were recruited for the study. The subjects were randomized into two groups: 10 patients were included in the study group and received SIMT and 10 patients were assigned to the control group and received sham training. Subjects in both groups trained daily, 6 times/week, for one-half h, for 3 months. The subjects started breathing at a resistance equal to 15% of their PImax for 1 week and the resistance was then increased incrementally to 60%. Spirometry, inspiratory muscle strength (assessed by measuring the PImax at residual volume), and endurance (expressed by the relationship between PmPeak and PImax), the 12-min walk test, and peak VO2 were performed before the beginning and at the end of the training period.
Results: All patients in the training group showed an increase in the inspiratory muscle strength [mean (+/- standard error of the mean) PImax increased from 46.5 +/- 4.7 to 63.6 +/- 4.0 cm H2O, p < 0.005], and endurance (mean PmPeak/PImax from 47.8 +/- 3.6 to 67.7 +/- 1.7%, p < 0.05), while they remained unchanged in the control group. This was associated in the training group with a small but significant increase in forced vital capacity, a significant increase in the distance walked (458 +/- 29 to 562 +/- 32 m, p < 0.01), and an improvement in the dyspnea index score. No statistically significant change in the mean peak VO2 was noted in either group.
Conclusions: Specific inspiratory muscle training resulted in increased inspiratory muscle strength and endurance. This increase was associated with decreased dyspnea, increase in submaximal exercise capacity, and no change in maximal exercise capacity. This training may probe to be a complementary therapy in patients with congestive heart failure.