The following is the summary of  “Variability in Cardiopulmonary Exercise Testing Biologic Controls” published in the January 2023 issue of Respiratory Care January by DeCato, et al.

Cardiopulmonary exercise testing is an increasingly prevalent test and is regarded as the acknowledged standard for determining exercise capability. To evaluate the instrument for use in quality control, it is necessary to quantify the variability. Although biologic control testing is recommended by guidelines, there is no information on how to conduct such tests. In order to provide a realistic means of assessing and performing biologic control testing, researchers set out to characterize the variability of oxygen consumption (V^O2), carbon dioxide production (V^CO2), and minute ventilation (VE) at different work rates under steady-state conditions in multiple subjects over the course of a year.

Investigators conducted a single-center, prospective study with 4 healthy volunteers (2 males and 2 women). On a computer-controlled cycle ergometer, subjects exercised for 6 minutes at a steady work rate ranging from 25 to 100 W. Since the transition to steady state occurs in discrete increments, they averaged the data over the preceding 120 s at each work rate. For each subject across all 4 work rates and all repetitions, we give descriptive statistics, including mean, median, range, SD, and coefficient of variation (CoV). Given the normative nature of these data, z-scores were employed, with a value of larger than 1.96 z-scores being used to signify considerable test variability.

Subjects performed 16–39 biocontrol studies throughout 1-y. All subjects had a mean CoV of 6.59% in V^O2, 6.41% in V^O2, and 6.32% in VE. Changes in V^O2, V^CO2, and VE of 9.4-18.1%, 9.6-18.1%, and 9-21.5%, respectively, were correlated to z-scores of 1.96 across all 4 workloads. They conclude that steady-state measurements of V^O2, V^CO2, and VE acquired by biocontrol testing are subject to long-term fluctuation. Utilizing ± 1.96 z-scores allows one to assess if a result exceeds predicted variability, which may necessitate inquiry of the instrument.

Source: rc.rcjournal.com/content/68/1/38