Impact of Inspiratory Muscle Training on Inspiratory Muscle Metaboreflex in Patients with Heart Failure with Preserved Ejection Fraction

INTRODUCTION: High inspiratory muscle work elicits respiratory muscle metaboreflex activation, contributing to increases in mean arterial pressure (MAP) and decreases in leg blood flow in adults at rest. Patients with heart failure with preserved ejection fraction (HFpEF) have exaggerated cardiovascular responses with inspiratory muscle metaboreflex activation. The purpose of this study was to investigate the effect of inspiratory muscle training (IMT) on respiratory muscle metaboreflex-mediated cardiovascular responses in patients with HFpEF. METHODS: 13 patients with HFpEF (6M/7F; 69±9 years; 33±5kg/m 2 ) underwent evaluation of cardiovascular responses to inspiratory resistive breathing tasks (IRBT) at 60% maximal inspiratory pressure (MIP) pre- and post-IMT. Beat-by-beat blood pressure and heart rate were measured using finger plethysmography. Vastus lateralis blood flow index (BFI) was measured using near infrared spectroscopy and indocyanine green dye. Vastus lateralis vascular resistance index was calculated. IMT consisted of 30 repetitions/day, 7 days/week for 8 weeks at 40% MIP. RESULTS: MIP increased from 71±21 to 95±25cmH 2 O following IMT (p<0.01). Following 8 weeks of IMT, the increases in MAP (Pre-IMT: 15±6 vs. Post-IMT: 9±6mmHg; p<0.01) and heart rate (Pre-IMT: 9±6 vs. Post-IMT: 6±5 beats/min, p=0.03) during the 60% IRBT were attenuated compared to pre-IMT. The % increase in vastus lateralis vascular resistance index during the 60% IRBT was smaller post-IMT than pre-IMT (Pre-IMT: 87±53 vs. Post-IMT: 47±34%, p<0.01). The % decrease in vastus lateralis BFI during the 60% IRBT was attenuated post-IMT than pre-IMT (Pre-IMT: -33±14 vs. Post-IMT: -23±12%; p<0.01). CONCLUSION: IMT attenuates the inspiratory muscle metaboreflex-mediated cardiovascular responses in patients with HFpEF.