New CPET Model Reflects Altitude-Related Impacts and Improves Accuracy

Research study background

Researchers in the Heart Institute at Children’s Hospital Colorado have developed and reported the first normative values for pediatric cardiopulmonary exercise testing (CPET) performed at moderate altitude. Moderate altitude typically refers to an elevation range of approximately 4,900 to 8,200 feet (1,500 to 2,500 meters) above sea level. This work addresses a critical gap in existing interpretive data, derived from sea-level populations that overlook the physiological differences associated with changes in elevation.

Accurate interpretation of CPET results, which assess exercise capacity and cardiovascular response to exercise, is particularly important for clinical decision-making in patients with congenital heart disease (CHD).

In this retrospective study, the new norms were compared against the widely used traditional models created by Cooper and Bruce and the updated model by Burstein. The study authors evaluated 1,154 maximal CPETs from a diverse cohort of 6- to 18-year-olds tested on a treadmill or cycle ergometer between 2014 and 2023. Tests were conducted at four Children’s Colorado exercise labs located between approximately 5,184 to 6,926 feet (1,580 to 2,111 meters) above sea level. All participants had normal cardiac structure and function and completed CPETs for symptoms during exercise and/or family history of cardiac disease.

Key testing parameters included peak oxygen consumption (VO₂ peak), peak heart rate (HR), peak ventilation (VE) and respiratory exchange ratio (RER). The team conducted separate analyses for the treadmill and cycle ergometer, developing polynomial regression models with independent variables including age, gender, body mass index and ethnicity to predict CPET testing parameters. These models were applied to a validation cohort for both exercise modalities, using root mean square error to evaluate predictive accuracy.

Overall, results demonstrated that existing models overestimated exercise parameters and were poor predictors of actual exercise values. The new model outperformed the existing models in all exercise variables except resting systolic blood pressure, where the Burstein model was more accurate. In addition, predicted VO2 values in all existing models were higher than the study authors’ equation, suggesting altitude significantly affects the differences between the models.

Clinical implications:

These new altitude-specific normative values, derived from the largest known reported pediatric exercise dataset, provide a critical framework for improving diagnostic accuracy and patient management. For patients with CHD who live at moderate elevation, the new model could reduce the risk of misdiagnosing normal exercise performance as pathological and enhance clinical decision-making for improved outcomes. This work underscores the importance of considering altitude when developing normative exercise data.