Acute bronchodilator therapy does not reduce wasted ventilation during exercise in COPD

Publication date: Available online 22 March 2018 Source:Respiratory Physiology & Neurobiology Author(s): Amany F. Elbehairy, Katherine A. Webb, Pierantonio Laveneziana, Nicolle J. Domnik, J. Alberto Neder, Denis E. O’Donnell This randomized, double-blind, crossover study aimed to determine if acute treatment with inhaled bronchodilators, by improving regional lung hyperinflation and ventilation distribution, would reduce dead space-to-tidal volume ratio (VD/VT); thus contributing to improved exertional dyspnea in COPD. Twenty COPD patients (FEV1 = 50 ± 15%predicted;mean ± SD) performed pulmonary function tests and symptom-limited constant-work rate exercise at 75% peak-work rate (with arterialized capillary blood gases) after nebulized bronchodilator (BD;ipratropium 0.5mg + salbutamol 2.5 mg) or placebo (PL;normal saline). After BD versus PL: Functional residual capacity decreased by 0.4L (p = 0.0001). Isotime during exercise after BD versus PL (p < 0.05): dyspnea decreased: 1.2 ± 1.9 Borg-units; minute ventilation increased: 3.8 ± 5.5L/min; IC increased: 0.24 ± 0.28L and VT increased 0.19 ± 0.16L. There was no significant difference in arterial CO2 tension or VD/VT, but alveolar ventilation increased by 3.8 ± 5.5L/min (p = 0.02). Post-BD improvements in respiratory mechanics explained 51% of dyspnea reduction at a standardized exercise time. Bronchodilator-induced improvements in respiratory mech...
Source: Respiratory Physiology and Neurobiology - Category: Respiratory Medicine Source Type: research