Characteristics of COPD tidal breathing patterns measured by structured light plethysmography (SLP): An age, gender, BMI matched study

Abstract

It has been reported that tidal breathing measured with SLP could reflect differences between patients with COPD and in health (De Boer, W. et al. ERJ 2014; 44: 58 P1985). The data also suggested that there could be an influence of age. We therefore compared tidal breathing patterns in a cohort of 25 COPD and 25 healthy subjects matched for age, gender and BMI to examine how tidal breathing parameters and their variability differ between COPD and health. Five minutes of resting tidal breathing was acquired from each subject using a Thora-3Di ™ (PneumaCare, Cambridge, UK) SLP device. Median and interquartile range (IQR) of 12 breath-by-breath tidal breathing parameters were calculated for each subject. Parameters included timing indices, measures of thoraco-abdominal asynchrony (TAA), relative thoracic contribution and measures quantifying the shape of flow-volume loops. One way analysis of variance (ANOVA) was used to test for differences between the two groups. Respiratory rate (RR) was found to be higher in COPD (p<0.05). Inspiratory time (Ti) and its variability were both significantly lower in COPD (p<0.01 and p<0.001 respectively). Parameters derived from Ti (e.g. duty cycle and Ti/Te) were also found to differ (lower in COPD). TAA and IE50 were higher in COPD (p<0.05 and p<0.01 respectively). Time to peak tidal expiratory flow over expiratory time (TPTEF/TE) was shorter (p<0.01) and considerably less variable (p<0.001) in COPD. Tidal breathing patterns in COPD patients are different from healthy subjects and this difference is reflected in SLP derived tidal breathing parameters and their variability.