Airway obstruction is associated with reduced variability in specific parts of the tidal breathing flow–volume curve in young children

Published in: ERJ Open Research 2019

Authors: Ville-Pekka Seppä, Anton Hult, Javier Gracia-Tabuenca, Marita Paassilta, Jari Viik, Davor Plavec and Jussi Karjalainen

Lung function testing in subjects with limited cooperation, such as young children, the elderly or the disabled, is often extremely challenging even when using methods that need a low level of cooperation like impulse oscillometry (IOS). Hence, measurement and analysis of tidal breathing have been studied as an alternative option for conventional lung function methods in detecting airway obstruction. However, attempts to determine clinically useful obstruction-related tidal breathing indices, such as peak points or line fits from the tidal breathing flow–volume (TBFV) curves, have produced very limited outcomes. A more recent approach has focused on looking at the tidal breathing curve variability over time. The tidal breathing indices and the mathematical methods for their quantification analysed in early studies have been diverse; for instance, approximate entropy [1, 2] and noise limit of the flow signal [3], interquartile range of various tidal breathing indices [4, 5], and coefficient of variability of tidal volume [6]. A common finding has been that lower airway obstruction is associated with reduced variability in the tidal breathing pattern.

Impedance pneumography is a method that enables continuous measurement of TBFV curves during sleep at night [7, 8]. The aim of this study was to determine if the obstruction-related reduction in tidal breathing pattern variability is contained within a specific part of the TBFV curve by analysing nocturnal impedance pneumography measurements from wheezy (asthmatic) and healthy young children.

We conclude that the obstruction-related reduction in the variability of the TBFV curve occurs in its specific parts, being the most discriminative at 15–45% of the expired volume in young children with recurrent wheeze.

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