Signal-correction errors in the EasyOne Pro LAB multiple-breath washout device significantly impact outcomes in children and adults.

Oestreich, Marc-Alexander; Wyler, Florian; Buess, Christian; Etter, Blaise; Ramsey, Kathryn A; Latzin, Philipp (2024). Signal-correction errors in the EasyOne Pro LAB multiple-breath washout device significantly impact outcomes in children and adults. Journal of applied physiology, 136(3), pp. 460-471. American Physiological Society 10.1152/japplphysiol.00096.2022

Text oestreich-et-al-2024-signal-correction-errors-in-the-easyone-pro-lab-multiple-breath-washout-device-significantly.pdf - Accepted Version Restricted to registered users only until 26 January 2025. Available under License Publisher holds Copyright. Download (2MB) | Request a copy

BACKGROUND

Multiple-breath washout (MBW) is an established technique to assess functional residual capacity (FRC) and ventilation inhomogeneity in the lung. Indirect calculation of nitrogen concentration requires accurate measurement of gas concentrations.

AIM

To investigate the accuracy of the CO2 concentration and molar mass (MM) values used for the indirect calculation of nitrogen concentration in a commercial MBW device (EasyOne Pro LAB (EOPL), ndd Medizintechnik AG, Switzerland) and its impact on outcomes.

METHODS

We used high-precision gas mixtures to evaluate CO2 and MM sensor output in-vivo and in-vitro. We developed updated algorithms to correct for observed errors and assessed the impact on MBW outcomes and FRC measurement accuracy compared to body plethysmography.

RESULTS

The respiratory exchange ratio (RER)-based adjustment of the measured CO2 signal used in the EOPL led to an overestimated CO2 signal (range -0.1; 1.0%). In addition, an uncorrected dependence on humidity was identified. These combined effects resulted in an overestimation of expired nitrogen concentrations (range -0.7; 2.6%), and consequently MBW outcomes. Corrected algorithms reduced the mean (SD) cumulative expired volume by 15.8% (9.7%), FRC by 6.6% (3.0%), and lung clearance index by 9.9% (7.6%). Differences in FRC between the EOPL and body plethysmography further increased.

CONCLUSION

Inadequate signal correction causes RER- and humidity-dependent expired nitrogen concentration errors and overestimation of test outcomes. Updated algorithms reduce average signal error, however, RER values far from the population average still cause measurement errors. Despite improved signal accuracy, the updated algorithm increased the difference in FRC between the EOPL and body plethysmography.

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