Objective: the reversibility of chronic obstructive pulmonary disease (COPD) is evaluated mainly by FEV(1) after bronchodilators. However, lung volumes also change significantly in COPD, but few studies addressed the characteristics of the changes in post bronchodilator airflow and lung volume in patients with COPD. This study was carried out to evaluate the difference of FEV(1) response and forced vital capacity (FVC) response to bronchodilators in patients with COPD as well as the impact of severity of COPD on the flow and volume reversibility.
Methods: 465 patients with COPD (male 426, female 39), aged 67.1 +/- 8.3 (42 approximately 86) yrs were enrolled from Jan. 2006 to Aug. 2008. The severity of COPD was graded according to the GOLD criteria. The change and rate of change of FVC and FEV(1) 20 minutes after inhalation of salbutamol 400 microg via spacer were measured and compared. Positive response to the bronchodilator was determined as FEV(1) or FVC increased 12% as well as 200 ml or above. The impacts of severity on flow and volume response were also studied.
Results: post-bronchodilator FEV(1) increased 117 ml with a 13.2% improvement on average compared with baseline. Post-bronchodilator FVC increased 258 ml and improved by 14.0% on average. The rate of positive reversibility in FEV(1) and FVC was 18.7% (87/465) and 44.1% (205/465), respectively. The improvement of FEV(1) decreased as a function of the severity of COPD. In contrast, the improvement of FVC was increased in those with more severe disease.
Conclusion: the improvement of lung volume is more significant and maybe more important than airflow response in patients with COPD, especially in those with severe disease. In addition to FEV(1), the reversibility of COPD should also be evaluated by FVC.