Abstract
Introduction: Progressive chronic heart failure slows the recovery of microvascular oxygen delivery and utilization, which produce deleterious implications to exercise capacity. Respiratory muscle unloading can enhance the responses to exercise thereby allowing a closer matching between skeletal muscle oxygen delivery and utilization in patients with chronic heart failure (CHF). Hypothesis: We reasoned that noninvasive ventilation administered by proportional assisted ventilation (PAV) could accelerate skeletal muscle reoxygenation after high intensity exercise in CHF humans. To test this hypothesis, we conducted a study with 12 patients with stable CHF who were randomized to receive PAV or sham ventilation during high-intensity constant work exercise and compared the effects of these interventions on oxygen pulmonary (O2p), cardiac output and [[Unable to Display Character: &#8710;]][deoxi-Hb+Mb] off kinetics. Methods: Twelve patients with CHF (NYHA class II and III and left ventricle ejection fraction= 26±9%) underwent two high-intensity, constant-work rate (80% peak) cycle ergometer tests receiving PAV or sham ventilation. Off-exercise kinetics of the primary component of oxygen uptake, an index of fractional oxygen extraction by near infrared spectroscopy (~[[Unable to Display Character: &#8710;]][deoxy-Hb+Mb]) in the vastus lateralis) and cardiac output (QT) by impedance cardiography were assessed. Results: PAV significantly accelerated the recovery of O2p when compared with sham τ = 56±22 vs. 77±42s, respectively, p<0.05). Interestingly, PAV was associated with faster fractional O2 extraction (~[[Unable to Display Character: &#8710;]][deoxy-Hb+Mb] by near-infrared spectroscopy) (τ= 31±19 vs. 42±22s, respectively, p<0.05) . In addition, kinetics of QT were significantly faster with PAV than sham (τ = 39±22 vs. 78±46s, respectively, p<0.05). Conclusions: These data indicate that PAV has beneficial effects on recovery of muscle metabolism and central hemodynamics after high-intensity exercise in CHF patients. Financial Support: FAPESP 2009-01842-0
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