Methacholine Challenge Test (MCT) in Healthy Adults

Knowledge of Methacholine Challenge Test (MCT) and impedance Oscillometry (IOS) is limited. Only three studies have included adult patients, and none of these with healthy controls. The three studies have combined IOS and spirometry in the same test, although it is not recommended to perform IOS after a test that requires deep breathing, e.g. FEV1 measurement. Deep breathing is considered to affect the impedance via reduced tone in the smooth muscle.