The reversibility of increased airways resistance in chronic heart failure measured by impulse oscillometry

Abstract

BackgroundPatients with chronic heart failure complain of breathlessness and fatigue on exercise. Airways resistance is increased and lung compliance is reduced in chronic heart failure patients. The aim of this study was to determine whether the pulmonary abnormalities are reversible and whether any improvements lead to changes to exercise capacity or symptoms. MethodsTwelve patients with stable chronic heart failure and 10 matched controls underwent repeated assessment of airways resistance using impulse oscillometry and peak exercise testing with metabolic gas exchange after receiving nebulized saline as placebo or combined salbutamol and ipratropium bromide in a double-blind crossover randomized fashion. ResultsPatients had lower peak oxygen consumption and a steeper slope relating ventilation to carbon dioxide production than controls. Bronchodilators reduced peripheral airways resistance in patients (0.53 versus 0.38, P<.02) and controls (0.21 versus 0.19, P<.005) and increased measures of compliance in both groups. There was no effect on the peak oxygen consumption, exercise time, ventilation to carbon dioxide slope, or anaerobic threshold. There was an increase in peak tidal volume (Vt) in both groups but this did not lead to an increase in peak ventilation. The slope relating symptoms to ventilation (ie, Borg/Ve) was significantly reduced in the patients after bronchodilators (17%±8%, P<.05). The relationship between the improvement in Vt and reduction in gradient of the Borg/Ve slope was significant (r=.40, P<.05). ConclusionsNebulized bronchodilators improve airways resistance, lung reactance, and peak tidal volume during exercise in chronic heart failure but do not increase peak exercise capacity. They do, however, reduce the symptom of breathlessness.