Support Care Cancer. 2020 Jan 4. doi: 10.1007/s00520-019-05094-4. [Epub ahead of print]
Aerobic exercise prescriptions in clinical populations commonly involve target intensities based on cardiopulmonary exercise tests (CPET). CPETs are often discontinued prior to a patient achieving true maximum oxygen consumption (VO2 max) which can adversely affect exercise dose and efficacy monitoring; however, reasons for early discontinuation are poorly reported. Accordingly, we explored the CPET termination reasons in persons with cancer participating in exercise intervention studies.
This study comprised of an exploratory, descriptive analysis of retrospective CPET data (VO2 and anaerobic threshold) and termination reasons in a convenience sample of people with cancer participating in exercise intervention studies in a single laboratory. CPETs were standardized using the modified Bruce treadmill protocol with expired gas collection and analysis using a metabolic cart. VO2 max was considered “met” when participants demonstrated (a) oxygen consumption plateau or (b) two of the following criteria: rating of perceived exertion ≥ 9/10, respiratory exchange ratio ≥ 1.15, and/or heart rate of 95% of age-predicted maximum. The frequency and distribution of reasons for test termination relative to the number of CPET exposures for the participants were reported.
Forty-four participants engaged in exercise studies between February 2016 and March 2018 provided data for the analysis. Participants completed up to three CPETs during this period (total of 78 CPETs in the current analysis). Eighty-six percent of all CPETs were terminated prior to achieving VO2 max verification criteria and no tests resulted in an oxygen consumption plateau. For those that did not demonstrate achievement of VO2 max verification criteria, reasons for discontinuation were distributed as follows: equipment discomfort-49%, volitional peak-36%, and physical discomfort-14.9%. For those who met VO2 max criteria, volitional peak was the most common reason for test termination (45.5%), followed by physical discomfort (36.4%), and equipment discomfort (18.2%).
In our sample of cancer survivors, VO2 max criteria were infrequently met with equipment discomfort being a primary reason for participant-driven test termination. Protocol and equipment considerations are necessary for interpretation and application of CPET findings in clinical practice.