Lung Clearance Index: A New Measure of Ventilation Inhomogeneity in Childhood Respiratory Diseases

Abstract: Conventional spirometry has long been considered the primary test for assessing respiratory function deficits in children and adults. However, the need to perform forced breathing maneuvers can make it challenging to perform these examinations in an uncooperative child. For these reasons, techniques such as gas dilutions and the Multiple-Breath-Washout (MBW) method have been implemented because they allow for early assessment of damage to the small airways. These methods permit the determination of the possible presence of ventilatory inhomogeneity in the lungs by analyzing the clearance of an inert gas used as a tracer. The equipment consists of a mass spectrometer combined with a flow meter. The Lung Clearance Index (LCI) is most often used to evaluate ventilatory inhomogeneity. This narrative review aimed to review the literature on technical and practical aspects of the MBW test and evaluate the clinical implications of the LCI in pediatric respiratory disease.