Area under the Maximum Expiratory Flow-Volume Curve – A Sensitive Parameter in the Evaluation of Airway Patency

Abstract

Background: The most frequently used parameters for assessing bronchoconstriction and bronchodilation are forced expiratory volume in 1 s (FEV₁) and peak expiratory flow (PEF). Objectives: To assess the sensitivity of other parameters after induced bronchoconstriction and bronchodilation. Methods: From maximum expiratory flow-volume (MEFV) curves, forced vital capacity, FEV₁, PEF, maximum expiratory flows (MEF) at 25, 50 and 75% of vital capacity and the area under the MEFV curve (A_ex) were measured in two groups of asthmatic children after induced bronchoconstriction and bronchodilation, and in children with cystic fibrosis (CF) after bronchodilation. Results: In 142 asthmatics without airway obstruction, bronchoconstriction was induced by inhalation of 1% histamine aerosol. The 20% fall in A_ex compared to baseline was found in all asthmatics, while the 20 and 15% falls in FEV₁ were noted in 36 and 65% of the patients, respectively. Other parameters were less sensitive or interpretation was problematic. Another110 asthmatics with mild-moderate airway obstruction were treated with various bronchodilators. The 20% increase in A_ex was observed in all asthmatics, while the 20% increase in FEV₁ was found in only 33% of the patients and the 15% increase in FEV₁ in 51%. In 9CF children, the pattern of changes in A_ex and FEV₁ after bronchodilation was similar to that in asthmatics. Conclusions: A_ex was a sensitive and less problematic parameter in the evaluation of airway patency in comparison with FEV₁ and other parameters measured from the MEFV curve in our study patients.