Acute Unloading of the Work of Breathing Extends Exercise Duration in Patients With Heart Failure

摘要: Objectives. This study investigated whether maximal exercise performance can be improved by acutely decreasing the work of breathing in these patients. Background. Exertional dyspnea is a frequent limiting symptom patients with heart failure. It may result from increased breathing. Methods. Fifteen failure and nine age-matched normal subjects underwent two tests. Subjects exercised twice randomized, single-blind manner using room air (RA) 79% helium/21% oxygen mixture (He). Respiratory gas analysis, Borg scale recordings perceived near infrared spectroscopy an accessory respiratory muscle were obtained during exercise. Results. In there was no significant difference peak uptake (Vo2) ([mean ± SD] RA 38 8 vs. He 35 7 ml/kg per min), duration (RA 724 163 762 123 s) or minute ventilation 97 27 28 liters/min, all p = NS). Only three control thought that subjectively easier. contrast, average 146 s longer 868 293 1,014 338, < 0.01). Peak Vo2(RA 19 4 18 5 min) 53 12 15 liters/min) unchanged (both The quotient at lower 1.05 0.08 0.98 0.06, 0.05). Thirteen easier (p 0.02 group). Conclusions. failure, pulmonary factors, including airflow turbulence, contribute to performance. Therapeutic interventions aimed attenuating beneficial. (J Am Coll Cardiol 1997;29:590–6)