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Introduction: Measurement of lung function aids diagnosis and treatment of respiratory conditions, but spirometry is not possible in young children. SLP is a novel technique for measuring chest and abdominal wall movement during tidal breathing that would allow us to obtain measurements in patients where this is not currently possible. Aims: We investigated the use of SLP for measuring tidal breathing in children aged 3-17 years. Methods: Using a Thora-3Di™ (PneumaCare, Cambridge, UK), a structured light pattern was projected onto the chest and abdomen of a seated child. Movement with respiration is captured using stereo-photogrammetry to produce a trace of tidal breathing. Clinically-useful respiratory indices can be calculated such as respiratory rate (RR), inspiratory time ratio (Ti/Ttot) and ratio of inspiratory to expiratory flow at 50% of tidal movement (IE50). The relative contribution of chest wall movement to total movement (RC2Tot) can also be captured. Results: 44 children (22 female) aged 3-17 years underwent assessment with SLP. Normative data are summarized in the table below. Conclusion: We have demonstrated the feasibility of obtaining objective measures of tidal breathing using SLP in children.

Lung function assessment is important in diagnosing and monitoring treatment in asthma. Conventional spirometry requires effort and cooperation of the patient, is challenging in young children and therefore not performed routinely. Structured light plethysmography (SLP) is a non-contact means of assessing lung function that may be useful in such cases. The aim of this study was to assess the use of SLP in determining changes in tidal breathing parameters following treatment with bronchodilator in children with acute asthma. Children admitted to the ward with asthma and on regular bronchodilator treatment were recruited for participation (n=33). Assessment of tidal breathing using a Thora-3Di ™ SLP device was carried out pre- and post-bronchodilator treatment. One-tailed t-tests were used to determine significant changes in tidal breathing parameters determined by SLP. Results showed that the rib-cage versus abdominal contribution to breathing decreased significantly following bronchodilator intervention (46% to 42%, p=0.016) towards the value seen in normative data for the same age group (40%). Other parameters such as respiratory rate, inspiratory time ratio (Ti/Ttot) and ratio of inspiratory to expiratory flow at 50% of tidal movement (IE50) were not significantly affected by bronchodilator treatment. However, variability of Ti/Ttot (as determined by coefficient of variation) did reduce following intervention (0.122 to 0.109, p=0.049). We have shown that SLP can be used in children with acute asthma to acquire objective measures of tidal breathing, and that changes in symmetry such as rib-cage contribution to breathing can be quantified.