Inspiratory Muscle Training for People With Heart Failure

Heart failure is frequently associated with inspiratory muscle weakness, which contributes to dyspnea, reduced exercise capacity, impaired quality of life, and adverse cardiovascular outcomes. Although inspiratory muscle training (IMT) is a recommended adjunct to cardiovascular rehabilitation, the optimal training modality remains uncertain, particularly among patients with reduced and preserved ejection fraction. This randomized controlled trial will evaluate the efficacy of a novel inspiratory muscle training protocol using tapered flow resistive loading (TFRL) compared with conventional threshold loading (TL) and usual care. A total of 108 clinically stable patients with heart failure (NYHA class II-III) will be enrolled. Participants will be stratified according to heart failure phenotype (reduced or preserved ejection fraction) and allocated to one of three groups: TFRL, TL, or control. Both training interventions will be performed for 8 weeks in combination with supervised exercise-based cardiac rehabilitation. Primary and secondary outcomes will include inspiratory muscle strength and endurance, exercise capacity, pulmonary function, dyspnea, skeletal muscle oxygenation, autonomic balance, arterial stiffness, and health-related quality of life. The study is powered to detect moderate between-group differences and interaction effects with 80% statistical power and a two-sided alpha level of 0.05. Changes over time and between groups will be analyzed using analysis of covariance (ANCOVA), adjusting for baseline inspiratory muscle strength. The trial aims to determine whether TFRL provides superior clinical and physiological benefits compared with conventional inspiratory muscle training and whether treatment responses differ according to heart failure phenotype.

Inclusion Criteria: * History of symptomatic heart failure (NYHA functional class I and III). * Participants able to understand and respond to the instructions given in the study * Participants with stable disease at the moment of inclusion in this study. * Unaltered dose and type of medication up to three months before the start of the study Exclusion Criteria: * Participants unable to perform a valid baseline cardiopulmonary exercise test. * Participants with unstable angina, acute myocardial infarction, and/or heart surgery within the past three months. * Participants with other concomitant cardiac or neurological disease. * Participants with difficulties in maintaining a proper mouth seal or unable to avoid air leakage during pulmonary function testing. * Participants in other non-pharmacological study will be also excluded. * Current smokers. * Cardiac acute decompensation.