Expression of bronchodilator response: comparison of four indices

AbstractSeveral indices have been suggested to express the bronchodilator response but there is no agreement on what is the ideal expression. The forced expiratory volume in 1 s (FEV1) was measured in 190 patients of bronchial asthma before and after inhalation of 200 μg salbutamol. Four different indices of bronchodilator response were calculated. The change in FEV1 was expressed as absolute value (ΔFEV1), as a percentage of initial FEVl (ΔFEVl% initial), as a percentage of the predicted normal value (ΔFEVl% predicted) and as a percentage of maximum achievable reversibility, i.e. the difference between predicted and initial values (ΔFEV1% [predicted–initial]). A significant negative correlation was observed between ΔFEVl initial and initial FEV1% predicted (r=−0.33, P