S108 Respiratory volume tracking and structured light plethysmography in the assessment of breathing pattern disorder

Introduction Breathing pattern disorder (BPD) causes dyspnoea and is commonly misdiagnosed as, or co-exists with, chronic respiratory disease, especially asthma. Clinical management and research are difficult in the absence of validated objective methods for diagnosis and assessment. We aimed to investigate two novel methods for the assessment of BPD. Respiratory Volume Tracking (RVT) allows visualisation of tidal breathing over time and in relation to maximal inspiratory and expiratory reserve volumes. Structured light plethysmography (SLP) images and measures chest and abdominal wall movement during breathing by projecting a checkerboard pattern of light onto the chest wall. Methods We recruited participants with severe asthma and/or BPD from the regional severe asthma clinic. All participants had demographic details recorded, then performed spirometry, RVT and SLP. Ethical approval was obtained and participants provided written informed consent. Results 20 healthy controls, 12 people with asthma and 10 with BPD completed the study, 33% male, mean (SD) age 45 (18) yrs. Mean (SD)%predicted FEV1 was lowest in the asthma group [86.3 (18.5)] versusBPD [99.4 (18.4)] and healthy [102.6 (14.0), ANOVA p=0.043]; median (range) expiratory reserve volume%predicted was highest in the healthy group [111.9 (40.2–189.0)]versus asthma [68.3 (13.6–212.8)] or BPD [77.1 (27.1–176.3), Kruskal-Wallis p=0.029]. Visual inspection of the RVT traces confirmed abnormal breathing patterns in 5/12 in the asthma group and 8/10 in the BPD group (see examples in figure 1). Data using SLP were available for 32 participants. The within-individual variability was highest for ribcage contribution to thoraco-abdominal movement in the BPD group (Kruskal-Wallis p=0.015) and lowest for time to reach peak tidal expiratory flow/expiratory time in asthma (Kruskal-Wallis p=0.005). Conclusion Abnormalities in breathing pattern can be assessed visually using RVT, and quantified using SLP. Using the latter we found increased within-individual variability in chest wall movement relative to overall thoraco-abdominal movement in BPD. Future work will investigate how the data provided by each technique correlates within individuals.