PURPOSE: To assess the effects of inspiratory muscle training (IMT) on autonomic activity, endothelial function, and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in patients with chronic heart failure.
METHODS: Using age- and sex-matched controlled study, 23 patients (mean left ventricular ejection fraction 29 +/- 2%) were assigned to either a high-intensity training group (n = 14), New York Heart Association (NYHA) class II (n = 9)/III (n = 5), or a low-intensity training group (n = 9), NYHA class II (n = 6)/III (n = 3), exercising at 60% and 15% of sustained maximum inspiratory pressure (SPImax), respectively, 3 times per week for 10 weeks. Before and following IMT, patients underwent cardiopulmonary exercise testing and dyspnea evaluation on exertion. Sympathovagal balance was assessed by heart rate variability (HRV) from 24-hour electrocardiogram and endothelial function, using venous occlusion plethysmography. Serum levels of NT-proBNP were determined.
RESULTS: High-intensity training group improved maximum inspiratory pressure (PImax, 105.4 +/- 5.3 vs 79.1 +/- 5 cm H2O, P = .001), SPImax (511 +/- 42 vs 308 +/- 28 cm H2O/sec/10, P = .001), peak oxygen consumption (19 +/- 1.2 vs 17.1 +/- 0.7 mL.kgmin, P = .01) and dyspnea (17.6 +/- 0.2 vs 18.1 +/- 0.1, P = .02). Endothelium-dependent vasodilation, HRV, and NT-proBNP levels were not altered. Low-intensity training group increased only the PImax (97.6 +/- 11.3 vs 84.2 +/- 8.7 cm H2O, P = .03).
CONCLUSIONS: Improvement in dyspnea and exercise tolerance after IMT were not associated with changes in markers of HRV, endothelial function, and NT-proBNP in patients with mild to moderate chronic heart failure. Further studies on the effects of IMT in advanced heart failure would be worthwhile.
PMID: 18360185 DOI: 10.1097/01.HCR.0000314203.09676.b9

BACKGROUND AND PURPOSE: Persons with chronic heart failure (HF) have poor ventilatory muscle strength, and this weakness is associated with dyspnea. The purpose of this study was to examine the effects of inspiratory muscle training (IMT) on ventilatory muscle strength and dyspnea in patients with chronic HF.
SUBJECTS: Fourteen patients (mean age [+/-SD] = 52 +/- 8.5 years) with end-stage cardiomyopathy and chronic HF (mean left ventricular ejection fraction = 23% +/- 13% and New York Heart Association class = 3.6 +/- 0.6) participated in the study.
METHODS: Inspiratory muscle training was performed at 20% of maximal inspiratory pressure (MIP) for 5 to 15 minutes, three times a day, for 8 weeks. Dyspnea was evaluated at rest and during exercise.
RESULTS: Both MIP and maximal expiratory pressure (MEP) were greater after 2 weeks of IMT (51 +/- 21 to 63 +/- 23 cm H2O and 85 +/- 22 to 96 +/- 19 cm H2O, representing 24% and 13% improvement). Dyspnea scores at rest and during exercise decreased after 2 weeks (2.0 +/- 0.7 to 1.3 +/- 0.5 and 3.6 +/- 0.5 to 2.6 +/- 0.6, representing 29% and 28% improvement) and plateaued throughout the remainder of IMT. Baseline MEP was related to the percentage of change in MEP after IMT (r = -.72), and several measures of pulmonary function were related to the degree of improvement in dyspnea after IMT (r = -.57 to -.82) and in MIP after IMT (r = .71).
CONCLUSION AND DISCUSSION: Improvements in MIP, MEP, and dyspnea were found after 2 weeks of IMT. Greater pulmonary function was associated with greater improvement in dyspnea and ventilatory muscle strength after IMT. These improvements may decrease the dependency and impairment associated with chronic HF.
PMID: 9256871 DOI: 10.1093/ptj/77.8.830

OBJECTIVES: This study sought to evaluate the effects of inspiratory muscle training in inspiratory muscle strength, as well as in functional capacity, ventilatory responses to exercise, recovery oxygen uptake kinetics, and quality of life in patients with chronic heart failure (CHF) and inspiratory muscle weakness. ,br>BACKGROUND: Patients with CHF may have reduced strength and endurance in inspiratory muscles, which may contribute to exercise intolerance and is associated with a poor prognosis.
METHODS: Thirty-two patients with CHF and weakness of inspiratory muscles (maximal inspiratory pressure [Pi(max)] <70% of predicted) were randomly assigned to a 12-week program of inspiratory muscle training (IMT, 16 patients) or to a placebo-inspiratory muscle training (P-IMT, 16 patients). The following measures were obtained before and after the program: Pi(max) at rest and 10 min after maximal exercise; peak oxygen uptake, circulatory power, ventilatory oscillations, and oxygen kinetics during early recovery (VO2/t-slope); 6-min walk test; and quality of life scores.
RESULTS: The IMT resulted in a 115% increment Pi(max), 17% increase in peak oxygen uptake, and 19% increase in the 6-min walk distance. Likewise, circulatory power increased and ventilatory oscillations were reduced. The VO2/t-slope was improved during the recovery period, and quality of life scores improved.
CONCLUSIONS: In patients with CHF and inspiratory muscle weakness, IMT results in marked improvement in inspiratory muscle strength, as well as improvement in functional capacity, ventilatory response to exercise, recovery oxygen uptake kinetics, and quality of life.
PMID: 16487841 DOI: 10.1016/j.jacc.2005.09.052

BACKGROUND: Muscle weakness has been suggested to result from the deconditioning that accompanies decreased activity levels in chronic cardiopulmonary diseases. The benefits of standard exercise programmes on exercise capacity and muscular strength in disease and health are well documented and exercise capacity is a significant predictor of survival in patients with chronic heart failure (CHF). Selective respiratory muscle training has been shown to improve exercise tolerance in CHF and such observations have been cited to support the suggestion that respiratory muscle weakness contributes to a reduced exercise capacity (despite biopsies showing the metabolic profile of a well trained muscle).
AIMS: This study aimed to determine the effects of selective inspiratory muscle training on patients with chronic coronary artery disease to establish if an improved exercise capacity can be obtained in patients that are not limited in their daily activities.
METHODS: Nine male patients performed three exercise tests (with respiratory and diaphragm function assessed before the third test) then undertook a 4-week programme of inspiratory muscle training. Exercise tolerance, respiratory and diaphragmatic function were re-assessed after training.
RESULTS: Exercise capacity improved from 812+/-42 to 864+/-49 s, P<0.05, and velocity of diaphragm shortening increased (during quiet breathing from 12.8+/-1.6 to 19.4+/-1.1 mm s(-1), P<0.005, and sniffing from 71.9+/-9.4 to 110.0+/-12.3 mm s(-1), P<0.005). In addition, five from nine patients were stopped by breathlessness before training; whereas only one patient was stopped by breathlessness after training.
CONCLUSION: The major findings in this study were that a non-intensive 4-week training programme of resistive breathing in patients with chronic coronary artery disease led to an increase in exercise capacity and a decrease in dyspnoea when assessed by symptom limited exercise testing. These changes were associated with significant increases in the velocity of diaphragmatic excursions during quiet breathing and sniffing. Patients that exhibited small diaphragmatic excursions during quiet breathing were most likely to improve their exercise capacity after the training programme. However, the inspiratory muscle-training programme was not associated with any significant changes in respiratory mechanics when peak flow rate, forced expiratory volume and forced vital capacity were measured. The resistive breathing programme used here resulted in a significant increase in the velocity of diaphragm movement during quiet breathing and sniffing. In other skeletal muscles, speed of contraction can be determined by the relative proportion of fibre types and muscle length (Jones, Round, Skeletal Muscle in Health and Disease. Manchester: University Press, 1990). The intensity of the training programme used here, however, is unlikely to significantly alter muscle morphology or biochemistry. Short-term training studies have shown that there can be increases in strength and velocity of shortening that do not relate to changes in muscle biochemistry or morphology. These changes are attributed to the neural adaptations that occur early in training (Northridge et al., Br. Heart J. 1990; 64: 313-316). Independent of the mechanisms involved, this small, uncontrolled study suggests that inspiratory muscle training may improve exercise capacity, diaphragm function and symptoms of breathlessness in patients with chronic coronary artery disease even in the absence of heart failure.
PMID: 10935679 DOI: 10.1016/s1388-9842(99)00027-6

BACKGROUND: Patients with chronic heart failure have a lower inspiratory muscle strength and fatigue endurance.
AIM: To assess the effects of selective training of respiratory muscles in patients with heart failure.
PATIENTS AND METHODS: Twenty patients with stable chronic heart failure, aged 58.3 +/- 3 years with an ejection fraction of 28 +/- 9%, were subjected to respiratory muscle training with threshold valves. The load was fixed in 30% of maximal inspiratory pressure (PImax) in 11 and in 10% of PImax in nine. Two sessions of 15 minutes, 6 days per week, during 6 weeks were done. Degree of dyspnea (Mahler score), maximal oxygen uptake, distance walked in 6 minutes, respiratory muscle function and left ventricular ejection fraction were measured before and after training.
RESULTS: Both training loads were associated to an improvement in dyspnea (+2.7 +/- 1.8 and +2.8 +/- 1.8 score points with 30% PImax and 10% PImax respectively), maximal oxygen uptake (from 19 +/- 3 to 21.6 +/- 5 and from 16 +/- 5 to 18.6 +/- 7 ml/kg/min with 30% PImax and 10% PImax respectively, p < 0.05), PImax (from 78 +/- 22 to 99 +/- 22 and from 72 +/- 34 to 82.3 cm H20 with 30% PImax and 10% PImax respectively), sustained PImax (from 63 +/- 18 to 90 +/- 22 and from 58 +/- 3 to 69 +/- 3 cm H20 with 30% PImax and 10% PImax respectively), and maximal sustained load (from 120 +/- 67 to 195 +/- 47 and from 139 +/- 120 to 192 +/- 154 g with 30% PImax and 10% PImax respectively). The distance walked in 6 min only increased in subjects trained at 30% PImax (from 451 +/- 78 to 486 +/- 68 m).
CONCLUSIONS: Selective training of respiratory muscles results in a functional improvement of patients with chronic heart failure.
PMID: 11351463