Florian Wyler1, Marc-Alexander H Oestreich2, Bettina Sarah Frauchiger3, Kathryn A Ramsey4, Philipp T Latzin5. 1. Division of Paediatric Respiratory Medicine and Allergology, Department of Paediatrics, grid.5734.5University of Bern, Bern, Switzerland. 2. Division of Paediatric Respiratory Medicine and Allergology, Department of Paediatrics, University of Bern, Bern, Switzerland. 3. Division of Paediatric Respiratory Medicine and Allergology, Department of Paediatrics, grid.412353.2University Children's Hospital Bern, Bern, Switzerland. 4. Marsico Lung Institute, grid.10698.36University of Bern, Chapel Hill, NC, United States. 5. Division of Paediatric Respiratory Medicine, grid.412353.2University Children's Hospital Bern, Bern, Switzerland.
Abstract
RATIONALE: Nitrogen multiple-breath washout is an established technique to assess functional residual capacity and ventilation inhomogeneity in the lung. Accurate measurement of gas concentrations is essential for the appropriate calculation of clinical outcomes. OBJECTIVES: We investigated the accuracy of oxygen and carbon dioxide gas sensor measurements used for the indirect calculation of nitrogen concentration in a commercial multiple-breath washout device (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and its impact on functional residual capacity and lung clearance index. METHODS: High precision calibration gas mixtures and mass spectrometry were used to evaluate sensor output. We assessed the impact of corrected signal processing on multiple-breath washout outcomes in a dataset of healthy children and children with cystic fibrosis using custom analysis software. RESULTS: We found inadequate correction for the cross sensitivity of the oxygen and carbon dioxide sensors in the Exhalyzer D device. This results in an overestimation of expired nitrogen concentration, and consequently multiple-breath washout outcomes. Breath-by-breath correction of this error reduced the mean (SD) cumulative expired volume by 19.6 (5.0)%, functional residual capacity by 8.9 (2.2)%, and lung clearance index by 11.9 (4.0)%. It also substantially reduced the level of the tissue nitrogen signal at the end of measurements. CONCLUSIONS: Inadequate correction for cross sensitivity in the oxygen and carbon dioxide gas sensors of the Exhalyzer D device leads to an overestimation of functional residual capacity and lung clearance index. Correction of this error is possible and could be applied by re-analyzing the measurements in an updated software version.
RATIONALE: Nitrogen multiple-breath washout is an established technique to assess functional residual capacity and ventilation inhomogeneity in the lung. Accurate measurement of gas concentrations is essential for the appropriate calculation of clinical outcomes. OBJECTIVES: We investigated the accuracy of oxygen and carbon dioxidegas sensor measurements used for the indirect calculation of nitrogen concentration in a commercial multiple-breath washout device (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and its impact on functional residual capacity and lung clearance index. METHODS: High precision calibration gas mixtures and mass spectrometry were used to evaluate sensor output. We assessed the impact of corrected signal processing on multiple-breath washout outcomes in a dataset of healthy children and children with cystic fibrosis using custom analysis software. RESULTS: We found inadequate correction for the cross sensitivity of the oxygen and carbon dioxide sensors in the Exhalyzer D device. This results in an overestimation of expired nitrogen concentration, and consequently multiple-breath washout outcomes. Breath-by-breath correction of this error reduced the mean (SD) cumulative expired volume by 19.6 (5.0)%, functional residual capacity by 8.9 (2.2)%, and lung clearance index by 11.9 (4.0)%. It also substantially reduced the level of the tissue nitrogen signal at the end of measurements. CONCLUSIONS: Inadequate correction for cross sensitivity in the oxygen and carbon dioxidegas sensors of the Exhalyzer D device leads to an overestimation of functional residual capacity and lung clearance index. Correction of this error is possible and could be applied by re-analyzing the measurements in an updated software version.
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Authors: Sotirios Fouzas; Anne-Christianne Kentgens; Olga Lagiou; Bettina Sarah Frauchiger; Florian Wyler; Ilias Theodorakopoulos; Sophie Yammine; Philipp Latzin Journal: ERJ Open Res Date: 2022-03-14
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