Inspiratory muscle training using an incremental endurance test alleviates dyspnea and improves functional status in patients with chronic heart failure.

BACKGROUND

The benefits of inspiratory muscle training (IMT) in patients with chronic heart failure (CHF) have been inadequately studied.

DESIGN AND METHODS

Using a prospective, age and sex-matched controlled study, we investigated 35 patients with moderate to severe CHF (NYHA class II-III and left ventricular ejection fraction 24.4+/-1.3% [mean+/-SEM]). An incremental respiratory endurance test using a fixed respiratory workload was provided by software with an electronic mouth pressure manometer interfaced with a computer. The training group (n=20) exercised at 60% of individual sustained maximal inspiratory pressure (SMIP) and the control group (n=15) at 15% of SMIP. All patients exercised three times weekly for 10 weeks. Pulmonary function, exercise capacity, dyspnea and quality of life were assessed, pre- and post-training.

RESULTS

The training group significantly increased both maximum inspiratory pressure (Pimax), (111+/-6.8 versus 83+/-5.7 cmH2O, P<0.001), and SMIP (527822+/-51358 versus 367360+/-41111 cmH2O/sec x 10(-1), P<0.001). Peak VO2 increased after training (17.8+/-1.2 versus 15.4+/-0.9 ml/kg/min, P<0.005), as did the six-minute walking distance (433+/-16 versus 367+/-22 meters, P<0.001). Perceived dyspnea assessed using the Borg scale was reduced for both the treadmill (12.7+/-0.57 versus 14.2+/-0.48, P<0.005) and the walking (9+/-0.48 versus 10.5+/-0.67, P<0.005) exercise tests and the quality of life score was also improved (21.1+/-3.5 versus 25.2+/-4, P<0.01). Resting heart rate was significantly reduced with training (77+/-3.3 versus 80+/-3 beats/min, P<0.05). The control group significantly increased Pimax (86.6+/-6.3 versus 78.4+/-6.9 cmH2O, P<0.05), but decreased SMIP (274972+/-32399 versus 204661+/-37184 cmH2O/sec x 10(1), P<0.005). No other significant effect on exercise capacity, heart rate, dyspnea, or quality of life was observed in this group.

CONCLUSION

Inspiratory muscle training using an incremental endurance test, successfully increases both inspiratory strength and endurance, alleviates dyspnea and improves functional status in CHF.