INTRODUCTION: Inspiratory muscle training (IMT) offers an alternative to exercise training (ExT) in the most severely deconditioned heart failure patients who are unable to exercise. We conducted a meta-analysis to determine magnitude of change in peak VO2, six minute walk distance (6MWD), Quality of Life measured by the Minnesota Living with Heart Failure Questionnaire (MLWHFQ), maximal inspiratory pressure (PI max) and ventilatory equivalent for carbon dioxide (VE/VCO2 slope) with IMT.
METHODS: A systematic search was conducted of randomized, controlled trials of IMT therapy in CHF patients using Medline (Ovid) (1950-February 2012), Embase.com (1974-February 2012), Cochrane Central Register of Controlled Trials and CINAHL (1981-February 2012). The search strategy included a mix of MeSH and free text terms for the key concepts heart failure, inspiratory or respiratory muscle training, exercise training
RESULTS: The eleven included studies contained data on 287 participants: 148 IMT participants and 139 sham or sedentary control. Compared to control groups, CHF patients undergoing IMT showed a significant improvement in peak VO2 (+1.83 ml kg(-1) min(-1), 95% C.I. 1.33 to 2.32 ml kg(-1) min(-1), p<0.00001); 6 MWD (+34.35 m, 95% C.I. 22.45 to 46.24 m, p<0.00001); MLWHFQ (-12.25, 95% C.I. -17.08 to -7.43, p<0.00001); PImax (+20.01, 95% C.I. 13.96 to 26.06, p<0.00001); and VE/VCO2 slope (-2.28, 95% C.I. -3.25 to -1.30, p<0.00001).
CONCLUSIONS: IMT improves cardio-respiratory fitness and quality of life to a similar magnitude to conventional exercise training and may provide an initial alternative to the more severely de-conditioned CHF patients who may then transition to conventional ExT.
KEYWORDS: Cardiorespiratory fitness; Exercise training; Inspiratory muscle training; Left ventricular dysfunction; Quality of life
PMID: 22560934 DOI: 10.1016/j.ijcard.2012.04.029

Brief Summary: This research aims to evaluate the effects of inspiratory muscle training (IMT) on apnea hypopnea index, sleepiness, sleep quality, cognitive function, motor task, executive function, quality of life, chemoreflex sensitivity and vagal modulation of heart rate in patients with heart failure and obstructive sleep apnea syndrome.
Detailed Description: Patients with heart failure will be selected through the Outpatient of the Rio Grande do Sul, for convenience. Subsequently, patients will be subjected to test respiratory muscle strength (manometer), respiratory muscle endurance, portable polysomnography, sleepiness, sleep quality, cognitive function (mini-mental state examination), motor task (execution of a sequence of digital movements), executive function, quality of life (SF-36), maximum exercise testing, chemoreflex sensitivity (peripheral chemoreflex by transient hypoxia and central chemoreflex by hypercapnic hyperoxia) and vagal modulation of heart rate (spectral analysis) before the start of the training protocol. Patients will be randomized to inspiratory muscle training or control group. Inspiratory muscle training will be performed for 30 minutes a day, 7 days a week, for 12 weeks with muscle training device (PowerBreathe). There will be a weekly monitoring in the Clinical Research Center of the institution where the maximal inspiratory pressure (MIP) and respiratory training techniques will be reassessed and readjusted (30% of MIP). The control group will be submitted to respiratory training techniques with muscle training device (PowerBreathe) without load. After this period, all initial tests will be reassessed. A group study with 15 heart failure patients without obstructive sleep apnea syndrome will be included.

It is well-known that muscle weakness and deconditioning play an important role in low exercise capacity of patients with HF. Interestingly, not only peripheral muscles are impaired, but also respiratory muscles. Studies have shown that patients with HF may have, in addition to decreasing maximal inspiratory muscle strength and endurance, metabolic and structural impairments in diaphragm fibers. Moreover, exercise capacity and weakness of inspiratory muscles have been associated with low quality of life and poor prognosis, which make the addition of inspiratory muscle training (IMT) reasonable in cardiovascular rehabilitation.The specifications of the loads to be imposed during IMT is the main factor determining the outcome. Studies of IMT have highlighted the need for a fixed inspiratory workload during exercise. Thus, purpose of this report was to perform a randomized clinical trial of the effects of addition of high-intensity vs. low-intensity IMT to combined aerobic and resistance Exercise in patients with heart failure.

BACKGROUND: In congestive heart failure (CHF), the prognostic significance of impaired respiratory muscle strength has not been established.
METHODS AND RESULTS: Maximal inspiratory pressure (Pi(max)) was prospectively determined in 244 consecutive patients (207 men) with CHF (ischemic, n=75; idiopathic dilated cardiomyopathy, n=169; age, 54+/-11 years; left ventricular ejection fraction [LVEF], 22+/-10%). Pi(max) was lower in the 244 patients with CHF than in 25 control subjects (7.6+/-3.3 versus 10.5+/-3.7 kPa; P=0.001). The 57 patients (23%) who died during follow-up (23+/-16 months; range, 1 to 48 months) had an even more reduced Pi(max) (6.3+/-3.2 versus 8.1+/-3.2 kPa in survivors; P=0.001). Kaplan-Meier survival curves differentiated between patients subdivided according to quartiles for Pi(max) (P=0.014). Pi(max) was a strong risk predictor in both univariate (P=0.001) and multivariate Cox proportional hazard analyses (P=0.03); multivariate analyses also included NYHA functional class, LVEF, peak oxygen consumption (peak VO(2)), and norepinephrine plasma concentration. The areas under the receiver-operating characteristic curves for prediction of 1-year survival were comparable for Pi(max) and peak VO(2) (area under the curve [AUC], 0.68 versus 0.73; P=0.28), and they improved with the triple combination of Pi(max), peak VO(2), and LVEF (AUC, 0.82; P=0.004 compared with AUC of Pi(max)).
CONCLUSIONS: In patients with CHF, inspiratory muscle strength is reduced and emerges as a novel, independent predictor of prognosis. Because testing for Pi(max) is simple in clinical practice, it might serve as an additional factor to improve risk stratification and patient selection for cardiac transplantation.
PMID: 11331255 DOI: 10.1161/01.cir.103.17.2153

OBJECTIVE: To investigate the significance of respiratory muscle weakness in chronic heart failure and its relation both to maximum oxygen consumption during cardiopulmonary exercise testing and to skeletal muscle (quadriceps) strength.
SUBJECTS: Seven healthy men aged 54.9 (SEM 4.3) years and 20 men with chronic heart failure aged 61.4 (1.6) years (P = 0.20) with radionuclide left ventricular ejection fraction of 25.4 (3.0)%.
METHODS: Mouth pressures during maximum static inspiratory effort (PImax) at functional residual capacity (FRC) and residual volume (RV) were measured in all subjects and taken as indices of inspiratory muscle strength. Similarly, mouth pressures during maximum static expiratory effort (PEmax) at FRC and total lung capacity (TLC) were taken as indices of expiratory muscle strength. Cardiopulmonary exercise testing was performed in all subjects. All controls and 15 heart failure patients also had their right quadriceps muscle strength measured.
RESULTS: There was respiratory muscle weakness in heart failure patients, with reduction of PImax at FRC (59.7) (6.3) v 85.6 (9.6) cm H2O, P = 0.045), PEmax at FRC (94.8 (6.2) v 134.6 (9.1) cm H2O, P = 0.004), and PEmax at TLC (121.7 (8.5) v 160.7 (13) cm H2O, P = 0.028). PImax at RV was also reduced but this did not reach statistical significance (77.3 (6.6) v 89.3 (13) cm H2O, P = 0.44). There was also significant weakness of the right quadriceps muscle (308.5 (22) v 446.2 (28) N, P = 0.001). PImax at both FRC and RV correlated with maximum oxygen consumption (r = 0.59, P = 0.006, and r = 0.45, P = 0.048 respectively) but not PEmax. There was, however, no significant correlation between PImax and right quadriceps strength.
CONCLUSIONS: Respiratory muscle weakness is seen in chronic heart failure. The results suggest that inspiratory muscles are important in determining maximum oxygen consumption and exercise tolerance in these patients. The lack of correlation between respiratory and right quadriceps muscle strength further suggests that the magnitude and time course of respiratory and locomotor muscle weakness may differ in individual patients. Treatment aimed at improving the function of the involved muscle groups may alleviate symptoms.
PMID: 7488451 PMCID: PMC484043 DOI: 10.1136/hrt.74.4.381