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Inadequate peak expiratory flow meter characteristics detected by a computerised explosive decompression device
  1. M R Miller1,
  2. P R Atkins2,
  3. O F Pedersen3
  1. 1Department of Medicine, University of Birmingham, Birmingham, UK
  2. 2Department of Electronic and Electrical Engineering, University of Birmingham, Birmingham, UK
  3. 3Department of Occupational and Environmental Medicine, University of Aarhus, Aarhus, Denmark
  1. Correspondence to:
    Dr M R Miller, University of Birmingham, Department of Medicine, Selly Oak Hospital, Birmingham B29 6JD, UK;
    m.r.miller{at}bham.ac.uk

Abstract

Background: Recent evidence suggests that the frequency response requirements for peak expiratory flow (PEF) meters are higher than was first thought and that the American Thoracic Society (ATS) waveforms to test PEF meters may not be adequate for the purpose.

Methods: The dynamic response of mini-Wright (MW), Vitalograph (V), TruZone (TZ), MultiSpiro (MS) and pneumotachograph (PT) flow meters was tested by delivering two differently shaped flow-time profiles from a computer controlled explosive decompression device fitted with a fast response solenoid valve. These profiles matched population 5th and 95th centiles for rise time from 10% to 90% of PEF and dwell time of flow above 90% PEF. Profiles were delivered five times with identical chamber pressure and solenoid aperture at PEF. Any difference in recorded PEF for the two profiles indicates a poor dynamic response.

Results: The absolute (% of mean) flow differences in l/min for the V, MW, and PT PEF meters were 25 (4.7), 20 (3.9), and 2 (0.3), respectively, at PEF ≈500 l/min, and 25 (10.5), 20 (8.7) and 6 (3.0) at ≈200 l/min. For TZ and MS meters at ≈500 l/min the differences were 228 (36.1) and 257 (39.2), respectively, and at ≈200 l/min they were 51 (23.9) and 1 (0.5). All the meters met ATS accuracy requirements when tested with their waveforms.

Conclusions: An improved method for testing the dynamic response of flow meters detects marked overshoot (underdamping) of TZ and MS responses not identified by the 26 ATS waveforms. This error could cause patient misclassification when using such meters with asthma guidelines.

  • peak expiratory flow
  • peak flow meters
  • lung function
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Supplementary materials


  • .

    Web-only Tables

    Files in this Data Supplement:

    • [View PDF] - Details of PEF, FEV1, and FVC for the 26 ATS waveforms together with the RT, DT, and the frequency limit for 95% and 99% of the power spectrum for these waveforms and profiles A and B
    • [View PDF] - Delivered rise time (RT) and 90% dwell time (DT) in ms recorded using the pneumotachograph when the mini-Wright meter was positioned upstream, and their difference from the input RT and DT for the 26 ATS profiles delivered by an optimal pump system

Footnotes

  • Funding: EC Contract MAT1-CT-930032.

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