Cardiopulmonary Exercise Tests in People with Chronic Stroke: Interpretation and Clinical Application

Objective To understand in people with stroke: 1) reasons for cardiopulmonary exercise test termination, 2) how frequently secondary criteria indicating a maximal test are met, and 3) how additional clinical measures provide context to interpreting test data. Design A secondary analysis from the Promoting Recovery Optimization of Walking Activity in Stroke (NCT02835313) clinical trial. Setting Four outpatient rehabilitation clinics. Participants People with chronic stroke able to walk without assistance of another person. Intervention Participants (n = 250) were randomized into a high-intensity treadmill or a step activity monitoring group. Cardiopulmonary exercise tests were conducted pre- (n = 247) and post-intervention (n = 185). Main Measures The primary measure was reason for cardiopulmonary exercise test termination. Secondary measures included: oxygen consumption, ventilatory threshold, peak heart rate, respiratory exchange ratio, six-minute walk test, and fastest walking speed. General Linear Mixed Methods were used to determine the fixed main effects of group and time, and their interaction for outcome variables.

There were 4 categories of test termination. Only 1.9% of tests achieved the threshold to confirm a maximal aerobic effort. Despite one group receiving a high-intensity walking intervention, there were no between group differences in oxygen consumption or ventilatory threshold. There were significant differences between groups in measures of walking capacity.

Analyses indicate few with chronic stroke demonstrate a maximal aerobic effort on a cardiopulmonary exercise test. If the cardiorespiratory system is not thoroughly taxed during these tests in people with chronic stroke, interpreting results as their cardiorespiratory fitness should be done cautiously. Clinical Messages People with stroke rarely (< 2%) attain an aerobic maximum on cardiopulmonary exercise tests. People with chronic stroke, frequently stop these tests due to biomechanical reasons which could reflect neuromuscular impairments, not cardiorespiratory impairments. Interpretation of test results as a measure of solely cardiorespiratory fitness or to prescribe exercise should be done cautiously in people with chronic stroke. Competing Interest Statement The authors have declared no competing interest. Funding Statement The study was funded by the NIH/NICHD, Promoting Recovery Optimization with WALKing Exercise after Stroke (PROWALKS), 1R01 HD086362-01; NIH/NICHD, Predoctoral Training in Physical Therapy and Rehabilitation Research, T32HD007490-23; NIH/NIGMS Center of Biomedical Research Excellence in Cardiovascular Health, P20GM113125; NIH NICHD/NCMRR R25HD105583. This research has been supported in part from a PODS Award from the Foundation for Physical Therapy Research. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Institutional Review Board (IRB) of the University of Delaware (UD) gave ethical approval for this work. IRB Protocol Number: 878153-57. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All data produced in the present study are available upon reasonable request to the authors.