Abstract
In persons with asthma, a deep inhalation (DI) to total lung capacity may lead to bronchoconstriction. The intensity of this effect has been shown to correlate positively with the severity of inflammatory airflow obstruction and the level of methacholine airway responsiveness. The correlates of lung volume history effects in the general population, however, are unknown. We analyzed combined maximal and partial expiratory flow-volume data, pre- and postbronchodilator spirometry data, and methacholine challenge data from 89 middle-aged and older men participating in the Normative Aging Study. The ratio of maximal to partial expiratory flow rates (VM/VP) was significantly correlated with methacholine airway responsiveness, even after adjustment for age and baseline FEV1. The direction of this correlation indicated that men with higher VM/VP ratios (i.e., greater dilator effect of a DI) tended to have greater methacholine airway responsiveness. Subjects with a higher VM/VP ratio also tended to have a greater response to a bronchodilator. These results suggest that, in the general population, airway responsiveness relates in part to airway smooth muscle tone. The correlations suggest that this relatively simple maneuver might play a role in future epidemiologic studies.
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