Abstract
IntroductionMetabolic simulators (MS) produce simulated human breaths for the purpose of verification of cardiopulmonary exercise test (CPET) equipment. MS should produce consistent identical breaths with known CO2 and O2 gas concentrations over a range of breath rates and tidal volumes. Reliability of a CPET metabolic cart depends on ongoing quality control and maintenance of the device, including intermittent verification with a MS. We compared two MS devices against two standard CPET systems.MethodsThe Vacumed 17056 (Vacumetrics, Ventura, CA) and Relitech (Relitech Systems BV, Nijkerk, The Netherlands) were used with two standard metabolic carts (Vyntus CPX and Vyntus ONE, both Vyaire Medical, Mettawa, IL, United States). Tidal volume (VT) was set at 2 and 3 L and breathing frequency ranged from 20 to 80 breaths per minute for each MS. At each set point, we measured three sets of 40 breaths. Primary outcome parameters collected were VT, oxygen consumption (O2), carbon dioxide production (CO2), and respiratory exchange ratio (RER).ResultsVT, RER, O2, and CO2 results as obtained from both MS were all within the limits of acceptability, at both tidal volume settings, and all ventilatory rates. No significant trends were identified for either MS device. The Relitech MS produced tidal volumes that were closer to the target VT for both CPET carts at both VT and all rates, but the results of both MS were within acceptable ranges.ConclusionVerification of CPET equipment using either the VM or RT metabolic simulator, producing highly accurate and predictable simulated breaths of known composition, enabling CPET laboratory managers to rely on subject test data obtained during cardiopulmonary exercise testing.
Highlights
Metabolic simulators (MS) produce simulated human breaths for the purpose of verification of cardiopulmonary exercise test (CPET) equipment
Mean VT results were significantly closer to the set point for the Relitech than for the Vacumed, but all results for both simulators were within acceptability ranges
Oxygen uptake and carbon dioxide output flow rates as measured by Vyntus CPX and Vyntus ONE are shown in the Bland-Altman plots in Figures 3, 4
Summary
Metabolic simulators (MS) produce simulated human breaths for the purpose of verification of cardiopulmonary exercise test (CPET) equipment. Reliability of a CPET metabolic cart depends on ongoing quality control and maintenance of the device, including intermittent verification with a MS. The data from CPET provide a highly accurate evaluation of linked physiological systems—ventilation, pulmonary gas exchange, circulation, and metabolic processes—against a known workload (American Thoracic Society, 2003). Research often compares CPET machines against a metabolic simulator (Casaburi et al, 1997; Porszasz et al, 2007; Beijst et al, 2013; Van Iterson et al, 2016; Levett et al, 2018; Radtke et al, 2019), evidence that the metabolic simulators themselves are accurate and reproducible has been lacking (American Thoracic Society, 2003) CPET laboratories must have confidence that the external systems used for calibration or verification are certified, accurate, and reliable “gold standards.” To date, research often compares CPET machines against a metabolic simulator (Casaburi et al, 1997; Porszasz et al, 2007; Beijst et al, 2013; Van Iterson et al, 2016; Levett et al, 2018; Radtke et al, 2019), evidence that the metabolic simulators themselves are accurate and reproducible has been lacking (American Thoracic Society, 2003)
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