Current Needs Assessment for Using Lung Clearance Index for Asthma in Clinical Practice

Purpose of Review: Asthma pathophysiology has shown that remodeling of the bronchial airways mainly affects the small rather than large airways. The severity of asthma is conventionally measured by forced expiratory volume 1 (FEV1) but this maneuver is insensitive to changes in distal airways with smaller diameter. The aim of this review is to evaluate the current evidence supporting LCI as a clinical tool for assessing small airways disease in asthma patients, as well as whether it is useful as a treatment response parameter in severe therapy‐resistant asthma (STRA) patients. Recent Findings: There is an increasing need for novel tests that can assess distal airway disease in asthma. Lung Clearance Index (LCI) may be a useful test for assessing more severe airway obstruction and the persistence of small airway disease. LCI measurement has been shown to be more sensitive than spirometry in cystic fibrosis (CF), but its clinical utility in asthma has not been thoroughly investigated. LCI abnormalities may be a sensitive marker for the persistence of small distal airway disease and may be associated with a more severe asthma endotype unresponsive to inhaled glucocorticoids. Summary: There is a need to identify other lung function tests for asthma that can identify early airway remodeling while simultaneously measuring the rate of lung function impairment. When compared to other conventional methods, multiple-breath washout (MBW) measures the lung clearance index (LCI), a more sensitive predictor of early airway disease that is feasible to perform in children. The goal of this review is to evaluate the current evidence of LCI as a clinical tool in asthma patients.