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Evaluation of bronchodilator responses in patients with "irreversible" emphysema

Respiratory Investigation Unit, Dept of Medicine, Queen's University, Kingston, Ontario, Canada

CORRESPONDENCE: D.E. O'Donnell, Richardson House, 102 Stuart Street, c/o Kingston General Hospital, Kingston, Ontario, Canada, K7L 2V7. Fax: 1 6135491459

Keywords: Bronchodilators, chronic obstructive pulmonary disease, emphysema, inspiratory capacity, lung hyperinflation, reversibility criteria

Received: February 19, 2001
Accepted July 11, 2001

This work was supported by the Ontario Ministry of Health.

Given the emerging physiological and clinical rationale for pharmacological lung-volume reduction, assessment of volume responses to bronchodilators is likely to be highly relevant in chronic obstructive pulmonary disease (COPD). The authors examined the magnitude of lung-volume reduction after acute bronchodilator treatment in patients with advanced emphysema.

Eighty-four stable patients with emphysema (mean±sem forced expiratory volume in one second (FEV₁): 32±1% predicted) performed spirometry and body plethysmography before and 15–30 min after 200 µg salbutamol. Only irreversible patients with a postbronchodilator change in FEV₁ <10% pred were considered in this study.

Postsalbutamol, the majority of subjects (83%) had significant improvements in one or more lung volumes: on average, residual volume (RV), functional residual capacity (FRC), inspiratory capacity (IC), forced vital capacity and slow vital capacity changed by –18±2, –10±1, 8±1, 9±1 and 7±1% pred (p<0.0005 each). Total lung capacity (TLC) decreased 0.12±0.04 L (p<0.01). Change in IC reflected change in FRC (r=–0.60, p<0.0005), but more strongly in the 57% of patients with no significant change in TLC (r=–0.93, p<0.0005). The magnitude and frequency of volume responses were greatest in patients with the most severe COPD; for example, RV decreased by 0.51±0.09 L (23±4% pred) and 0.27±0.04 L (14±2% pred) in severe and moderate subgroups, respectively.

Significant reductions in lung hyperinflation occurred in the absence of a change in forced expiratory volume in one second after low-dose salbutamol in a majority of patients with advanced emphysema; the greatest changes occurred in those with the most severe disease.