Day-to-day Variability Indices improve utility of Oscillometry in Paediatric Asthma

Abstract

AbstractBackgroundOscillometry may be a feasible and sensitive tool for objective remote monitoring of paediatric asthma.MethodsSchool-aged cohorts of healthy, well controlled and poorly controlled asthma (defined as ≥2 exacerbations within the preceding 12m) performed daily home-based oscillometry for 3-4 months (C-100 tremoflo, Thorasys Ltd), alongside objective measures of asthma control (ACQ weekly, ACT monthly), medication use (Hailie®) and exacerbations.Day-to-day variability was calculated as coefficient of variation (CV) for resistance at 5Hz (R5), reactance (X5) and Area under reactance curve (AX). We examined the ability to differentiate asthma from health and correlations with asthma control and exacerbation burden. Clinical exacerbation phenotypes were examined using principal component analysis and k-means clustering of oscillometry, symptoms, breathing parameters and symptoms.ResultsFeasibility was 74.9 ± 16.0% in health (n=13, over 93.7 ± 16.2 days) and 80.6 ± 12.9% in asthma (n=42, over 101.6 ± 24.9 days; 17 well controlled 27 poor asthma control). Significantly higher day-to-day variability in all oscillometry indices occurred in asthma, vs. health, and with worsening asthma control. CV R5 when clinically stable (CV R5 stable) was the best discriminator of asthma from health (AUC 0.87, p=0.00001). CV R5 correlated with all measures of asthma control and asthma exacerbation burden, r 0.41-0.52 (all p<0.01). Two exacerbation phenotypes were found based on oscillometry data in the pre- exacerbation period, characterised by severity of impairment of R5, X5, AX and CV R5 (n=12 more severe). Findings were similar using post-exacerbation period oscillometry data (n=8 more severe). Symptoms did not differ across clusters.ConclusionsHome-based oscillometry monitoring was highly feasible over extended periods in school-aged asthmatics. Utility was evidenced by improved ability to differentiate asthma from health, reflect asthma control and exacerbation burden and phenotype exacerbations.TAKE HOME MESSAGES-It is highly feasible to perform daily parent-supervised FOT monitoring for extended periods up to 4 months duration in school-aged children-In contrast to single-session based oscillometry indices, day-to-day variability in oscillometry indices were significantly higher in children with asthma compared to healthy controls, and differentiated levels of asthma control. The best performing parameter was CV R5.-All day-to-day variability indices correlated with measures of asthma control, with the best performing parameter CV R5 during stable periods (i.e., not including exacerbation periods).-Amongst asthmatics, day-to-day variability was greater during exacerbation periods than during non-exacerbation periods. Day-to-day variability correlated with measures of exacerbation burden, with the strongest correlations observed with CV R5 during stable periods-Day-to-day variability identified two distinct clusters of exacerbation, which were not identified by conventional measures or symptom based assessment.AUTHOR CONTRIBUTIONSConception and design: PDR, CT, GGKRecruitment, acquisition, analysis and/or interpretation of data: JH, AW, KH, SP, EdQA, AB, PF, DF, GJ, CP, CT, GGK, PDRWriting the manuscript or revising it critically: JH, AW, KH, SP, EdQA, AB, PF, DF, GJ, CP, HS, GGK, CT, PDR