A pilot study quantifying the shape of tidal breathing waveforms using centroids in health and COPD

Abstract

During resting tidal breathing the shape of the expiratory airflow waveform differs with age and respiratory disease. While most studies quantifying these changes report time or volume specific metrics, few have concentrated on waveform shape or area parameters. The aim of this study was to derive and compare the centroid co-ordinates (the geometric centre) of inspiratory and expiratory flow-time and flow-volume waveforms collected from participants with or without COPD. The study does not aim to test the diagnostic potential of these metrics as an age matched control group would be required. Twenty-four participants with COPD and thirteen healthy participants who underwent spirometry had their resting tidal breathing recorded. The flow-time data was analysed using a Monte Carlo simulation to derive the inspiratory and expiratory flow-time and flow-volume centroid for each breath. A comparison of airflow waveforms show that in COPD, the breathing rate is faster (17 ± 4 vs 14 ± 3 min(-1)) and the time to reach peak expiratory flow shorter (0.6 ± 0.2 and 1.0 ± 0.4 s). The expiratory flow-time and flow-volume centroid is left-shifted with the increasing asymmetry of the expired airflow pattern induced by airway obstruction. This study shows that the degree of skew in expiratory airflow waveforms can be quantified using centroids.

Tidal breathing patterns derived from structured light plethysmography in COPD patients compared with healthy subjects

“…The current study also revealed a marked shortening of inspiratory time (ie, median tI) in the COPD cohort, and, as a consequence, ratios derived from this parameter (tI/tE and tI/tTot) were also reduced. A similar shortening of tI and associated ratios was recorded in COPD patients who participated in earlier studies employing PNT or OEP to measure tidal breathing 6,8,10. Also, the median tPTEF SLP /tE was reduced in patients with COPD compared with healthy subjects.…”

“…A number of studies have reported that patients with COPD can be differentiated from their healthy counterparts using tidal breathing patterns 5–10. Therefore, this feasibility study investigated whether parameters derived from SLP – a novel and noncontact, light-based method for measuring tidal breathing – are also able to detect differences between breathing patterns in patients with COPD and subjects with no respiratory disease.…”

“…This study examined whether SLP could detect differences in tidal breathing patterns between a cohort of patients with COPD and a cohort of healthy subjects, as has been reported in other studies using more traditional techniques 5–7,9,10…”

“…Patterns of natural breathing at rest (or “tidal breathing”) have long been reported to differ between patients with respiratory disease and healthy subjects. Evidence to support such observations has grown over the past 15 years, as a number of studies have reported the effects of conditions such as COPD on tidal breathing patterns 5–10…”

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

“…In three of these flow patterns [18][19][20], flow rate was plotted against time. In the remainder [21], the flow pattern was presented as a plot of tidal volume versus time which was numerically integrated to yield flow rate versus time plot after acquisition.…”