Forced expiratory time: a composite of airway narrowing and airway closure

Abstract

Forced expiratory time (FET) has long been felt to reflect important physiological information about lung function but exactly how has never been clear. Here, we use a model analysis to assess the contributions of airway narrowing versus airway closure to FET in a population of individuals and find support for the theory that FET correlates positively with FEV1 if the amounts of lung emptying over a forced expiration vary from predicted values more than variations in the rates of lung emptying, whereas the correlation is negative in the opposite case.