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

作者：Elbehairy Amany F; Webb Katherine A; Laveneziana Pierantonio; Domnik Nicolle J; Neder J Alberto; O'Donnell Denis E^*

来源：Respiratory Physiology & Neurobiology, 2018, 252: 64-71.

DOI：10.1016/j.resp.2018.03.012

• COPD
• Bronchodilators
• Exercise
• Dyspnea
• Wasted ventilation

This randomized, double-blind, crossover study aimed to determine if acute treatment with inhaled broncho-dilators, by improving regional lung hyperinflation and ventilation distribution, would reduce dead space-to tidal volume ratio (V-D/V-T); 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=.0001). Isotime during exercise after BD versus PL (p < .05): dyspnea decreased: 1.2 +/- 1.9 Borg-units; minute ventilation increased: 3.8 +/- 5.5 L/min; IC increased: 0.24 +/- 0.28 L and V-T increased 0.19 +/- 0.16 L. There was no significant difference in arterial CO2 tension or V-D/V-T, but alveolar ventilation increased by 3.8 +/- 5.5 L/min (p=.02). Post-BD improvements in respiratory mechanics explained 51% of dyspnea reduction at a standardized exercise time.
Bronchodilator-induced improvements in respiratory mechanics were not associated with reduced wasted ventilation - a residual contributory factor to exertional dyspnea during exercise in COPD.

• 出版日期2018-6