Measurement of reversibility of airways obstruction: which parameters to use?

The bronchodilator test with increasing doses of terbutaline in chronic obstructive pulmonary disease patients

There is no uniform consensus on the dose of bronchodilator to be used in the bronchodilator test (BDT). The objective of the study was to determine the dose of inhaled terbutaline that can safely achieve a greater number of positive BDT in patients with chronic obstructive pulmonary disease (COPD). The study was prospective and single blinded. One-hundred and fifty patients with stable COPD were included. Their mean (+/-SD) age was 67.4 (8.8) years. Their mean forced expiratory volume in the first second (FEV1) was 1.14 (0.48) l (41% of the predicted value). A baseline spirometry was performed and a second 20 min after the inhalation of placebo. Three consecutive doses of 500 microg of inhaled terbutaline were administered and a new spirometry was performed after each one. A multivariate analysis based on the comparison of the repeated means was performed in order to analyse the spirometric changes achieved after the different doses of bronchodilator. The increase of FEV1 and forced vital capacity (FVC) with the two first doses of terbutaline was statistically significant; the increase of the peak expiratory flow (PEF) was significant after the three doses administered. The number of positive BDT were 40, 47 and 60 after each dose of terbutaline (P=0.004). The higher dose of terbutaline was more useful in identifying patients with significant bronchoreversibility and, moreover, was well tolerated. We suggest that this dose (1500 microg) should be routinely used in performing the BDT.