Reproducibility and validity of a handheld spirometer

Abstract

Background: Handheld spirometers have several advantages over desktop spirometers, but worries persist regarding reproducibility and validity of data from handheld spirometers. We undertook an independent examination of the EasyOne handheld spirometer.

Methods: The laboratory testing included reproducibility and validity testing with a waveform generator. We used standard American Thoracic Society waveforms for in-line testing, calibration adaptor testing, and testing during compression of the mouthpiece. The clinical testing involved repeated tests with 24 spirometry-naïve volunteers and comparison to spirometry results from laboratory (volume-sensing dry rolling seal) spirometer.

Results: The EasyOne exceeded standard thresholds for acceptability with the American Thoracic Society waveforms. In-line testing yielded valid results from the EasyOne. Between the EasyOne and the reference spirometer readings the mean +/- SD difference was 0.03 +/- 0.23 L for forced vital capacity (FVC) and -0.06 +/- 0.09 L for forced expiratory volume in the first second (FEV(1)). The calibration adaptor showed no appreciable problems. Extreme compression of the mouthpiece reduced the measured values. In clinical testing the coefficients of variation and limits of agreement were, respectively, 3.3% and 0.24 L for FVC, 2.6% and 0.18 L for FEV(1), and 1.9% and 0.05 for the FEV(1)/FVC ratio. The EasyOne readings were lower than those from the reference spirometer; the differences were: -0.12 L for FVC, -0.17 L for FEV(1), and -0.02 for FEV(1)/FVC. The limits of agreement were within criteria for FVC but not for the FEV(1), possibly due to a training effect.

Conclusion: The EasyOne spirometer yielded generally reproducible results that were generally valid, compared to the values from the laboratory spirometer. The use of the EasyOne in clinical, occupational, and research settings seems justified.

Figure 1

The EasyOne Diagnostic spirometer and spirette.

Figure 2

Setup for in-line EasyOne comparisions with the dry rolling seal HF5 spirometer

Figure 3

Bland-Altman plots of the difference vs. mean value in measurements of the forced vital capacity (Panel A) and the forced expiratory volume in one second (Panel B) from the EasyOne and laboratory spirometry from in-line testing. The solid lines of the Bland-Altman plots are regression lines of mean differences vs. mean values which allow for proportionality of mean differences vs. mean values (which is suggested by the non-zero slope of the line for FVC). The dashed lines are the 95% limits of agreement around the regression lines.

Figure 4

Bland-Altman plots of the difference vs. mean value in measurements of the forced vital capacity (Panel A) and the forced expiratory volume in one second (Panel B) from the EasyOne and laboratory spirometry in clinical testing among spirometry-naïve volunteers. The solid lines of the Bland-Altman plots are regression lines of mean differences vs. mean values which allow for proportionality of mean differences vs. mean values. The dashed lines are the 95% limits of agreement around the regression lines.