Forced vital capacity as a primary clinical outcome measure of bronchodilator reversibility in chronic obstructive pulmonary disease

Abstract

BackgroundSpirometry is the most reproducible and objective measurement of airflow limitation. The effectiveness of inhaled bronchodilator in individual patients with chronic obstructive pulmonary disease (COPD) is assessed by comparing measurements from pulmonary function tests made before and after administration. Generally forced expiratory volume in one second (FEV1) is the marker used with the global initiative for COPD (Global Initiative for Chronic Obstructive Lung Disease) guidelines. An increase in FEV1 that is both greater than 0.2 l and 12% above the prebronchodilator FEV1 value is considered significant.The aim of this study is to assess forced vital capacity (FVC) as a clinical outcome measure of bronchodilator reversibility in patients with COPD.Patients and methodsThis was a prospective study conducted on 163 patients with COPD at Suez Chest Hospital during the period from first of October 2016 till the end of March 2017. Patients were diagnosed based on clinical and spirometric criteria, and then reversibility test was done using inhaled short-acting B2-agonist. All patients were subjected to COPD Assessment Test questionnaire.ResultsOverall, 14.11% of patients had significant increase in FEV1, whereas 54.6% of patients had significant increase in FVC after bronchodilator inhalation. There was a highly significant positive correlation in FEV1 and FVC value before and after bronchodilator inhalation, and there was a highly significant direct correlation between ΔFEV1 and ΔFVC. There was a statistically significant relation between age and COPD Assessment Test score and ΔFVC.ConclusionΔFEV1 underestimates the true effect of bronchodilator as airway obstruction increases. The addition of ΔFVC to the evaluation will help physicians to better interpret airways reversibility tests, particularly in more severe patients, without adding spirometric maneuvers or measurements. Patients with COPD, even if nonresponders in terms of FEV1, may benefit from bronchodilators because they can breathe at a lower lung volume owing to reduced air-trapping, notwithstanding the fact that they are still flow limited. ΔFVC correlates better than ΔFEV1with the degree of airway obstruction and the clinical status of the patients.