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. 2020 Aug;31(6):636-642.
doi: 10.1111/pai.13257. Epub 2020 May 13.

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

Ville-Pekka Seppä  1 , Mirjana Turkalj  2   3   4 , Anton Hult  1 , Ivana Maloča Vuljanko  5 , Davor Plavec  4   6 ; Collaborators; Damir Erceg  2   3   4 , Giorgie Petković  5
Affiliations

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

Ville-Pekka Seppä et al. Pediatr Allergy Immunol. 2020 Aug.

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 < .0001) having significant correlation with number of days to discharge (r = -.38, P = .004). At 2 or 4 weeks post-discharge, EVI was not significantly different from the controls (P = .14, P = .49, respectively). EVI was significantly associated with chest auscultation findings (P = .0001) being 17.5 (4.9) (median, IQR) with normal auscultation, 15.6 (7.4) in those with prolonged expiration and 11.4 (6.8) in those with wheeze and/or rales and crackles.

Conclusions: EVI was found to be a sensitive, objective marker of acute BO, showing strong association with changes in clinical status in wheezy children aged 1-5 years.

Keywords: asthma; home monitoring; impedance pneumography; lung function; obstruction; pediatric; tidal breathing; wheeze.

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Conflict of interest statement

VPS holds patents relating to impedance pneumography. VPS and AH are employees of Revenio Group corporation that commercializes impedance pneumography technology. MT reports grants and personal fees from Revenio, during the conduct of the study; personal fees from Pliva; personal fees from Boehringer Ingelheim; personal fees from Belupo; personal fees from AbbVie; personal fees from Novartis; and personal fees from MSD, outside the submitted work; IMV reports grants and personal fees from Revenio, during the conduct of the study. DP reports grants, personal fees and non‐financial support from Revenio, during the conduct of the study; grants and personal fees from GlaxoSmithKline; personal fees and non‐financial support from Menarini; personal fees from Pliva; personal fees and non‐financial support from Boehringer Ingelheim; personal fees from Belupo; personal fees from AbbVie; personal fees from Novartis; personal fees from MSD; personal fees from Chiesi; and personal fees and non‐financial support from Philips, outside the submitted work.

Figures

Figure 1
Figure 1
Sketch of the measurement set‐up
Figure 2
Figure 2
EVI values of the healthy controls and the patients at different time points. See Table 2 for sample sizes. The rectangles cover 25‐75 percentile range, middle lines denote median, and the whiskers extend to extrema, excluding outliers, defined as being farther than 1.5 times IQR from the closer quartile
Figure 3
Figure 3
ROC curves of EVI value according to chest auscultation findings (only patients). Most of the abnormal auscultation findings (83%) occurred during inpatient period (while children received continuous bronchodilator therapy)
See this image and copyright information in PMC

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