Differences in the Measurement of Functional Residual Capacity Between Body Plethysmographs of Two Manufacturers.

Body plethysmography is a fundamental method for the assessment of static lung volumes. Although equipment is provided by several manufacturers, there are no established cross-vendor tools for quality control. In the process of quality control and analysis of data on hyperinflation from the large COPD cohort COSYCONET, hints appeared that plethysmographs of different vendors might yield different values for static lung volumes. Functional residual capacity (FRC) differed about 0.67 litres between plethysmographs of the manufacturer Vyaire and Ganshorn. Absolute differences of residual lung volume (RV) and total lung capacity (TLC) were similar. It appears undeniable that differences of this magnitude have an impact on clinical interpretation. Thus, device harmonization seems to be required.