OBJECTIVES: We tested the hypothesis that inspiratory muscle loading could result in exaggerated peripheral vasoconstriction in resting and exercising limbs and that inspiratory muscle training (IMT) could attenuate this effect in patients with chronic heart failure (CHF) and inspiratory muscle weakness.
BACKGROUND: Inspiratory muscle training improves functional capacity of patients with CHF, but the mechanisms of this effect are unknown.
METHODS: Eighteen patients with CHF and inspiratory muscle weakness (maximal inspiratory pressure <70% of predicted) and 10 healthy volunteers participated in the study. Inspiratory muscle loading was induced by the addition of inspiratory resistance of 60% of maximal inspiratory pressure, while blood flow to the resting calf (CBF) and exercising forearm (FBF) were measured by venous occlusion plethysmography. For the patients with CHF, blood flow measurements as well as ultrasound determination of diaphragm thickness were made before and after a 4-week program of IMT.
RESULTS: With inspiratory muscle loading, CHF patients demonstrated a more marked reduction in resting CBF and showed an attenuated rise in exercising FBF when compared with control subjects. After 4 weeks of IMT, CHF patients presented hypertrophy of the diaphragm and improved resting CBF and exercise FBF with inspiratory muscle loading.
CONCLUSIONS: In patients with CHF and inspiratory muscle weakness, inspiratory muscle loading results in marked reduction of blood flow to resting and exercising limbs. Inspiratory muscle training improves limb blood flow under inspiratory loading in these patients.
PMID: 18436118 DOI: 10.1016/j.jacc.2007.12.045

OBJECTIVE: To determine whether the impact of inspiratory muscle weakness on inspiratory muscle training (IMT) affects inspiratory function and exercise capacity in chronic heart failure (CHF) patients.
DATA SOURCES: Electronic searches were performed using the Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials, Cochrane Systematic Review, Embase, MEDLINE, and Physiotherapy Evidence Database (PEDro) databases up to August 2013.
STUDY SELECTION: Articles were included if participants had CHF and were >18 years old; the design was a randomized controlled trial; intervention was IMT; measurements were of inspiratory muscle function or exercise capacity; and the articles were published in English, Portuguese, or Spanish. Of the 1455 articles identified in the database searches, 9 studies met the inclusion criteria.
DATA EXTRACTION: Two independent reviewers selected and extracted information from articles and assessed the quality of the studies using the PEDro scale. The 2 reviewers discussed disagreements until consensus was achieved.
DATA SYNTHESIS: Meta-analyses compared IMT with controls/sham for maximal inspiratory pressure, sustained maximal inspiratory pressure, 6-minute walk distance, peak oxygen consumption, and minute ventilation after IMT. Subgroup analyses compared those with and without muscle weakness. CHF with inspiratory muscle weakness showed greater gains in the 6-minute walk distance and peak oxygen consumption compared with those with normative maximal inspiratory pressure. The mean quality analysis score was 7.1, and scores ranged from 6 to 10.
CONCLUSIONS: The results emphasize the importance of evaluating the inspiratory muscles to identify patients with CHF and inspiratory muscle weakness; subgroup that showed better results after IMT.
Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
KEYWORDS: Breathing exercises; Exercise tolerance; Heart failure; Rehabilitation; Respiratory muscles
PMID: 24631801 DOI: 10.1016/j.apmr.2014.02.022

AIMS: Vent-HeFT is a multicentre randomized trial designed to investigate the potential additive benefits of inspiratory muscle training (IMT) on aerobic training (AT) in patients with chronic heart failure (CHF).
METHODS AND RESULTS: Forty-three CHF patients with a mean age of 58 ± 12 years, peak oxygen consumption (peak VO2 ) 17.9 ± 5 mL/kg/min, and LVEF 29.5 ± 5% were randomized to an AT/IMT group (n = 21) or to an AT/SHAM group (n = 22) in a 12-week exercise programme. AT involved 45 min of ergometer training at 70-80% of maximum heart rate, three times a week for both groups. In the AT/IMT group, IMT was performed at 60% of sustained maximal inspiratory pressure (SPImax ) while in the AT/SHAM group it was performed at 10% of SPImax , using a computer biofeedback trainer for 30 min, three times a week. At baseline and at 3 months, patients were evaluated for exercise capacity, lung function, inspiratory muscle strength (PImax ) and work capacity (SPImax ), quality of life (QoL), LVEF and LV diameter, dyspnoea, C-reactive protein (CRP), and NT-proBNP. IMT resulted in a significantly higher benefit in SPImax (P = 0.02), QoL (P = 0.002), dyspnoea (P = 0.004), CRP (P = 0.03), and NT-proBNP (P = 0.004). In both AT/IMT and AT/SHAM groups PImax (P < 0.001, P = 0.02), peak VO2 (P = 0.008, P = 0.04), and LVEF (P = 0.005, P = 0.002) improved significantly; however, without an additional benefit for either of the groups.
CONCLUSION: This randomized multicentre study demonstrates that IMT combined with aerobic training provides additional benefits in functional and serum biomarkers in patients with moderate CHF. These findings advocate for application of IMT in cardiac rehabilitation programmes.
© 2014 The Authors. European Journal of Heart Failure © 2014 European Society of Cardiology.
KEYWORDS: Aerobic training; Chronic heart failure; Exercise; Inspiratory muscle training; Quality of life; Rehabilitation; Vent-HeFT trial
PMID: 24634346 DOI: 10.1002/ejhf.70

PURPOSE: To evaluate the effect of inspiratory muscle training (IMT) on cardiac autonomic modulation and on peripheral nerve sympathetic activity in patients with chronic heart failure (CHF).
METHODS: Functional capacity, low-frequency (LF) and high-frequency (HF) components of heart rate variability, muscle sympathetic nerve activity inferred by microneurography, and quality of life were determined in 27 patients with CHF who had been sequentially allocated to 1 of 2 groups: (1) control group (with no intervention) and (2) IMT group. Inspiratory muscle training consisted of respiratory exercises, with inspiratory threshold loading of seven 30-minute sessions per week for a period of 12 weeks, with a monthly increase of 30% in maximal inspiratory pressure (PI(max)) at rest. Multivariate analysis was applied to detect differences between baseline and followup period.
RESULTS: Inspiratory muscle training significantly increased PI(max) (59.2 ± 4.9 vs 87.5 ± 6.5 cmH(2)O, P = .001) and peak oxygen uptake (14.4 ± 0.7 vs 18.9 ± 0.8 mL·kg(-1)·min(-1), P = .002); decreased the peak ventilation (VE)/carbon dioxide production (VCO(2)) ratio (35.8 ± 0.8 vs 32.5 ± 0.4, P = .001) and the VE/VCO(2) slope (37.3 ± 1.1 vs 31.3 ± 1.1, P = .004); increased the HF component (49.3 ± 4.1 vs 58.4 ± 4.2 normalized units, P = .004) and decreased the LF component (50.7 ± 4.1 vs 41.6 ± 4.2 normalized units, P = .001) of heart rate variability; decreased muscle sympathetic nerve activity (37.1 ± 3 vs 29.5 ± 2.3 bursts per minute, P = .001); and improved quality of life. No significant changes were observed in the control group.
CONCLUSION: Home-based IMT represents an important strategy to improve cardiac and peripheral autonomic controls, functional capacity, and quality of life in patients with CHF. 論文へ

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). PMID: 18360185 DOI: 10.1097/01.HCR.0000314203.09676.b9