The contribution of inspiratory muscles function to exercise limitation in heart failure: pathophysiological mechanisms

Contextualização: A insuficiência cardíaca (IC) acarreta alterações histológicas, metabólicas e funcionais dos músculos inspiratórios. A fraqueza dos músculos inspiratórios, que ocorre em 30% a 50% dos pacientes com IC, associa-se com a redução da capacidade funcional, prejuízos para a qualidade de vida e piora no prognóstico desses indivíduos. Objetivos: Discutir os mecanismos fisiopatológicos que potencialmente explicam o papel da musculatura inspiratória na limitação ao exercício, abordando-se os reflexos que controlam a ventilação e a circulação durante o exercício. Método: Foram realizadas pesquisas na base de dados PUBMED, utilizando os termos inspiratory muscles, inspiratory muscle training, metaborreflex e chemoreflex e incluindo estudos publicados desde 1980. Resultados: A fraqueza muscular inspiratória está relacionada com intolerância ao exercício e com exacerbação do quimiorreflexo e do metaborreflexo inspiratório na IC. O metaborreflexo inspiratório pode ser atenuado pelo treinamento muscular inspiratório ou pelo treinamento aeróbico, melhorando o desempenho ao exercício. Conclusões: Os pacientes com IC podem apresentar alterações da função muscular inspiratória associadas com hiperatividade quimiorreflexa e metaborreflexa inspiratória, as quais podem agravar a intolerância ao exercício.Background: Heart failure induces histological, metabolic and functional adaptations in the inspiratory muscles. This inspiratory muscle weakness, which occurs in 30% to 50% of the heart failure patients, is associated with reduction in the functional capacity, reduction in the quality of life and with a poor prognosis in these individuals. Objectives: The objective of this review was to discuss the pathophysiological mechanisms that may explain the role of the inspiratory muscles in the exercise limitation with focus in the reflexes that control the ventilation and the circulation during the exercise. Method: We performed searches in the PUBMED database using the terms “inspiratory muscles”, “inspiratory muscle training”, “metaboreflex” and chemoreflex” and including studies published since 1980. Results: Inspiratory muscle weakness is associated with exercise intolerance and with an exaggerated inspiratory chemoreflex and metaboreflex in heart failure. The inspiratory metaboreflex may be attenuated by the inspiratory muscle training or by the aerobic exercise training improving the exercise performance. Conclusions: Patients with heart failure may present changes in the inspiratory muscle function associated with inspiratory chemoreflex and metaboreflex hyperactivity, which exacerbate the exercise intolerance

Inspiratory Muscle Training Improves Blood Flow to Resting and Exercising Limbs in Patients With Chronic Heart Failure

ObjectivesWe 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.BackgroundInspiratory muscle training improves functional capacity of patients with CHF, but the mechanisms of this effect are unknown.MethodsEighteen 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.ResultsWith 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.ConclusionsIn 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

Current insights of inspiratory muscle training on the cardiovascular system: a systematic review with meta-analysis

Background: Cardiorespiratory limitation is a common hallmark of cardiovascular disease which is a key component of pharmacological and exercise treatments. More recently, inspiratory muscle training (IMT) is becoming an effective complementary treatment with positive effects on muscle strength and exercise capacity. We assessed the effectiveness of IMT on the cardiovascular system through autonomic function modulation via heart rate variability and arterial blood pressure. Methods: Randomized controlled trials (RCTs) were identified from searches of The Cochrane Library, MEDLINE and EMBASE to November 2018. Citations, conference proceedings and previous reviews were included without population restriction, comparing IMT intervention to no treatment, placebo or active control. Results: We identified 10 RCTs involving 267 subjects (mean age range 51–71 years). IMT programs targeted maximum inspiratory pressure (MIP) and cardiovascular outcomes, using low ( n =6) and moderate to high intensity ( n =4) protocols, but the protocols varied considerably (duration: 1–12 weeks, frequency: 3–14 times/week, time: 10–30 mins). An overall increase of the MIP (cmH 2 O) was observed (−27.57 95% CI −18.48, −37.45, I 2 =64%), according to weighted mean difference (95%CI), and was accompanied by a reduction of the low to high frequency ratio (−0.72 95% CI−1.40, −0.05, I 2 =50%). In a subgroup analysis, low- and moderate-intensity IMT treatment was associated with a reduction of the heart rate (HR) (−7.59 95% CI −13.96, −1.22 bpm, I 2 =0%) and diastolic blood pressure (DBP) (−8.29 [−11.64, −4.94 mmHg], I 2 =0%), respectively. Conclusion: IMT is an effective treatment for inspiratory muscle weakness in several populations and could be considered as a complementary treatment to improve the cardiovascular system, mainly HR and DBP. Further research is required to better understand the above findings

Association between inspiratory muscle weakness and slowed oxygen uptake kinetics in patients with chronic obstructive pulmonary disease

INTRODUCTION: Patients with chronic obstructive pulmonary disease (COPD) may have poor inspiratory muscle function, which reduces minute and alveolar ventilation, leading to increased hypoxemia and slow pulmonary oxygen uptake ( O2) kinetics. However, little is known about the effect of inspiratory muscle weakness (IMW) on oxygen uptake kinetics in patients with COPD. Thus, we tested the hypothesis that COPD patients with IMW have slowed O2 kinetics. METHODS: An observational study was conducted including COPD patients with moderate to severe airflow limitation and a history of intolerance to exercise. Participants were divided into two groups: (IMW+; n = 22) (IMW-; n = 23) of muscle weakness. RESULTS: Maximal inspiratory (PImax), maximal expiratory (PEmax), maximal sustained inspiratory (PImaxsustained), and maximal endurance inspiratory muscle strength were lower in IMW+ patients (36 ± 9.5 cmH2O; 52 ± 14 cmH2O; 20 ± 6.5 cmH2O; 94 ± 84 s, respectively) than in IMW- patients (88 ± 12 cmH2O; 97 ± 28 cmH2O; 82.5 ± 54 cmH2O; 559 ± 92 s, respectively; pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author