Tidal breathing parameters measured using structured light plethysmography in healthy children and those with asthma before and after bronchodilator

Abstract

Structured light plethysmography (SLP) is a light‐based, noncontact technique that measures tidal breathing by monitoring displacements of the thoracoabdominal (TA) wall. We used SLP to measure tidal breathing parameters and their within‐subject variability (v) in 30 children aged 7–16 years with asthma and abnormal spirometry (forced expiratory volume in 1 sec [FEV1] <80% predicted) during a routine clinic appointment. As part of standard care, the reversibility of airway obstruction was assessed by repeating spirometry after administration of an inhaled bronchodilator. In this study, SLP was performed before and after bronchodilator administration, and also once in 41 age‐matched controls. In the asthma group, there was a significant increase in spirometry‐assessed mean FEV1 after administration of bronchodilator. Of all measured tidal breathing parameters, the most informative was the inspiratory to expiratory TA displacement ratio (IE50SLP, calculated as TIF50SLP/TEF50SLP, where TIF50SLP is tidal inspiratory TA displacement rate at 50% of inspiratory displacement and TEF50SLP is tidal expiratory TA displacement rate at 50% of expiratory displacement). Median (m) IE50SLP and its variability (vIE50SLP) were both higher in children with asthma (prebronchodilator) compared with healthy children (mIE50SLP: 1.53 vs. 1.22, P < 0.001; vIE50SLP: 0.63 vs. 0.47, P < 0.001). After administration of bronchodilators to the asthma group, mIE50SLP decreased from 1.53 to 1.45 (P = 0.01) and vIE50SLP decreased from 0.63 to 0.60 (P = 0.04). SLP‐measured tidal breathing parameters could differentiate between children with and without asthma and indicate a response to bronchodilator.

Tidal breathing parameters measured by structured light plethysmography in children aged 2-12 years recovering from acute asthma/wheeze compared with healthy children

“…This is in contrast to our findings in children with nonacute asthma where a significant decrease in IE50 SLP was observed following bronchodilator administration (Hmeidi et al. ). In this previous study, it was known that the children had a lower forced expiratory volume in 1 sec (FEV 1 ) prior to the bronchodilator intervention and that the reduction in IE50 SLP following bronchodilator treatment was associated with an increase in % predicted FEV 1, indicating a bronchodilator response.…”

“…Elevated IE50 has been reported in other populations, including in our previous studies in children aged 7–16 years with nonacute asthma (Hmeidi et al. ) and adults with COPD (Motamedi‐Fakhr et al. ).…”

“…It is of note that in the previous study in children with nonacute asthma, IE50 SLP remained significantly higher than normal after bronchodilation (Hmeidi et al. ). Our observations in the present study may suggest that, although considered in the recovery phase, these children were still experiencing the effects of respiratory exacerbation.…”

“…Tidal breathing was measured using an SLP device (Thora‐3Di™, PneumaCare Ltd., Ely, Cambridgeshire, UK), as previously described (Hmeidi et al. ). Briefly, a grid of light was projected onto the TA wall and changes in the grid pattern were recorded using two digital cameras in the scanner head of the SLP device (Fig.…”

“…Methods for calculation of tidal breathing parameters obtained from SLP have been reported in detail elsewhere (Hmeidi et al. ). The categories of parameters are described briefly below.…”