Expiratory variability index (EVI) is associated with the severity of acute bronchial obstruction in small children: A proof-of-concept study

Abstract

Background: Lung function testing in small children is cumbersome. However, reduced variability of tidal breathing recorded using impedance pneumography (IP) during sleep was recently found to be a potential objective marker of wheeze in children aged 1-5 years. We aimed to investigate how an acute bronchial obstruction (BO) and its severity, and recovery thereof reflect in expiratory variability index (EVI). Methods: EVI was measured using a wearable IP system (Ventica®) during sleep in 40 healthy controls (aged 1.5-5.9 years) and 30 patients hospitalized due to acute BO (aged 1.3-5.3 years). In healthy controls, EVI was measured for 1-3 nights at their homes. Patients were measured for several nights during hospitalization, as practically feasible, and at home 2 and 4 weeks post-discharge. Results: We received 79 EVI results from 39 controls and 139 from 30 patients. 90% had previous BO episodes, 30% used asthma controller medication before and 100% after hospitalization. Compared to controls, EVI was significantly lower during hospitalization (P