Journal of Clinical Monitoring and Computing

, Volume 28, Issue 1, pp 67–74 | Cite as

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

  • E. M. Williams
  • T. Powell
  • M. Eriksen
  • P. Neill
  • R. Colasanti
Original Research


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.


Flow–volume loop Spirometry Airflow obstruction Monte Carlo simulation 



Breathing rate (breaths min−1)


Tidal expiratory flow limitation


Expiratory flow centroid, BF corrected expiratory flow centroid


Inspiratory flow centroid, BF corrected inspiratory flow centroid


Forced expiratory flow in one second


Forced vital capacity


Flow volume centroid ratio (FECC:VECC)


Expiratory flow/volume centroid


Monte Carlo simulation


Peak inspiratory flow (L s−1)


Peak expiratory flow (L s−1)


Expiratory time centroid, BF corrected expiratory time centroid


Inspiratory time centroid, BF corrected inspiratory time centroid


Inspiratory/total breath time


Post-peak expiratory flow/duration of expiration


Change in post-peak expiratory flow at 20 % of expiration (°)


Change in post-peak expiratory flow at 80 % of expiration (°)


Expiratory volume centroid, BF corrected expiratory volume centroid


Inspiratory volume centroid, BF corrected inspiratory volume centroid


Conflict of interest



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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • E. M. Williams
    • 1
  • T. Powell
    • 1
  • M. Eriksen
    • 2
  • P. Neill
    • 3
  • R. Colasanti
    • 4
  1. 1.Faculty of Life Sciences and EducationUniversity of South WalesPontypriddUK
  2. 2.Volusense ASOsloNorway
  3. 3.Royal Glamorgan HospitalLlantrisantWales, UK
  4. 4.Computation InstituteUniversity of ChicagoChicagoUSA

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