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.
Another 110 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 9 CF 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.