Daily validation using a metabolic simulator after regular calibration increases the quality of cardiopulmonary...

Gas exchange measurements, such as oxygen uptake ( $\dot{V}{O}_2$ ) and carbon dioxide output ( $\dot{V}C{O}_2$ ), of cardiopulmonary exercise testing (CPET), are the key and gold standard for human cardiopulmonary functional evaluation. However, in terms of quality control, they are unstable and inaccurate. We used a metabolic simulator (MS) to detect measurement errors and enhance quality control.

In the Fuwai CPET laboratory, we performed CPET after systems had: (I) passed all the steps of regular system calibrations for flow and the partial pressure of O₂ and CO₂; and (II) passed the MS validation of $\dot{V}{O}_2$ and $\dot{V}C{O}_2$ at low, medium, and high metabolic rates (MRs) daily from 2014 to 2023 for eight different CPET carts/systems. The absolute percentage difference of the 1^st validation of both $\dot{V}{O}_2$ and $\dot{V}C{O}_2$ was calculated as follows: |[(measured - ideal) / ideal] × 100%|. A difference of <10% was set as the 1^st validation pass standard to run the laboratory, while a difference of ≥10% was classified as a 1^st validation failure. The absolute percentage difference of the 1^st validation among the eight carts/systems was compared using the Kruskal-Wallis H test. The rate of the 1^st validation failure, the number of validation days, and the median absolute percentage difference of the 1^st validation among the different CPET carts/systems were clustered using the hierarchical clustering method.

In total, we completed 1,810 validation days for the eight CPET carts/systems, and found a 10,860 absolute percentage difference of the 1^st validation of $\dot{V}{O}_2$ and $\dot{V}C{O}_2$ . The number of validation days completed by each cart/system and the 1^st validation failure rates were as follows: 8 (87.50%), 10 (90.00%), 54 (48.15%), 349 (43.27%), 20 (45.00%), 759 (21.21%), 525 (29.52%), and 85 (22.35%), respectively. The overall absolute percentage difference of the 1^st validation of each cart/system was 7.32% (P₂₅, P₇₅: 3.67%, 13.82%), 9.12% (P₂₅, P₇₅: 3.33%, 30.4%), 6.82% (P₂₅, P₇₅: 4.31%, 9.06%), 5.40% (P₂₅, P₇₅: 2.60%, 8.26%), 4.90% (P₂₅, P₇₅: 2.21%, 9.68%), 4.32% (P₂₅, P₇₅: 2.17%, 6.78%), 5.62% (P₂₅, P₇₅: 2.96%, 8.19%), and 5.35% (P₂₅, P₇₅: 2.55%, 7.81%), respectively. The Kruskal-Wallis H test results revealed significant differences among the eight carts/systems (H=274.86, P<0.001), and the pairwise comparisons showed that cart/system F had the lowest absolute percentage difference of 4.32% (P₂₅, P₇₅: 2.17%, 6.78%). The hierarchical cluster classified carts/systems A and B as one cluster, carts/systems C, E, and H as another cluster, and carts/systems D, F, and G as yet another cluster.

Using an MS can decrease measurement errors and variability for CPET. It can also improve the quality control of CPET.