Spirometric Correlates of Improvement in Exercise Performance after Anticholinergic Therapy in Chronic Obstructive Pulmonary Disease

Abstract

We wished to determine which resting spirometric parameters best reflect improvements in exercise tolerance and exertional dyspnea in response to acute high-dose anticholinergic therapy in advanced COPD. We studied 29 patients with stable COPD (FEV 1 5 40 6 2% predicted (%pred); mean 6 SEM) and moderate to severe chronic dyspnea. In a double-blind placebo-controlled cross-over study, pa- tients performed spirometry and symptom-limited constant-load cycle exercise before and 1 h after receiving 500 m g of nebulized ipratropium bromide (IB) or saline placebo. There were no significant changes in spirometry, exercise endurance, or exertional dyspnea after receiving placebo. In response to IB (n 5 58): FEV 1 , FVC, and inspiratory capacity (IC) increased by 7 6 1%pred, 10 6 1%pred, and 14 6 2%pred, respectively (p , 0.001), with no change in the FEV 1 /FVC ratio. After receiving IB, ex- ercise endurance time (Tlim) increased by 32 6 9% (p , 0.001) and slopes of Borg dyspnea ratings over time decreased by 11 6 6% (p , 0.05). Percent change (% D ) in Tlim correlated best with D IC%pred (p 5 0.020) and change in inspiratory reserve volume ( D TLC%pred) (p 5 0.014), but not with D FVC%pred, D PEFR%pred, or D FEV 1 %pred. Change in Borg dyspnea ratings at isotime near end exercise also correlated with D IC%pred (p 5 0.04), but not with any other resting parameter. Changes in spirometric measurements are generally poor predictors of clinical improvement in re- sponse to bronchodilators in COPD. Of the available parameters, increased IC, which is an index of reduced resting lung hyperinflation, best reflected the improvements in exercise endurance and dys- pnea after IB. IC should be used in conjunction with FEV 1 when evaluating therapeutic responses in COPD. O'Donnell DE, Lam M, Webb KA. Spirometric correlates of improvement in exercise performance after anticholinergic therapy in chronic obstructive pulmonary disease. AM J RESPIR CRIT CARE MED 1999;160:542-549. In patients with advanced chronic obstructive pulmonary dis- ease (COPD), improvement in lung mechanics, alleviation of dyspnea, and increased activity levels are desirable therapeu- tic goals. In this population, studies that are designed to evalu- ate the impact of interventions, such as bronchodilator ther- apy, increasingly incorporate these important clinical outcome measures. We have shown that measurements of dynamic lung hyperinflation, exercise endurance, and Borg ratings of exer- tional dyspnea intensity can be used to evaluate therapeutic responses reliably, being both reproducible and responsive (1). Relief of exertional dyspnea following both b 2 -agonist and anticholinergic therapy has been shown to correlate well with reduction of dynamic lung hyperinflation, as measured by se- rial inspiratory capacity (IC) measurements during exercise, in