Incorporating Cardiopulmonary Function Testing Into Care
A child with a heart condition is likely to undergo a range of tests to reveal abnormalities in that organ’s structure and functioning. During cardiopulmonary exercise testing (CPET), physiologists take a different approach and put the pulmonary, cardiovascular, and skeletal muscle systems to work together to assess a child’s overall aerobic fitness. “This information tells us how well the heart's pumping, how well a treatment is working, or, if they’ve been in an exercise program, how conditioned their muscles are,” says Aimee Layton, PhD, director of the Columbia’s pediatric exercise laboratory. “Then we work with the medical team to figure out how that pertains to surgical outcomes or prognosis.”
During CPET testing, lab members place a child on a treadmill or stationary bike modified to accommodate a smaller body, and fit him or her with a device to breathe into. As the child performs exercises of increasing intensity, lab equipment measures the maximum oxygen that is delivered to and extracted by their muscle cells—called peak VO2. The resulting measures of cardiorespiratory fitness and endurance provide additional insights to the diagnostic puzzle, Dr. Layton says.
Cardiologists at Columbia prescribe CPET annually or biannually for their patients who are doing well, to track any changes over time. They may also prescribe CPET to determine whether an adolescent is capable of playing a high school sport, or to assess a child who is beginning to get short of breath while playing. “It's fun working with the kids, especially on sports clearances, where we can help a child get to do what they love,” says Dr. Layton. “If they don’t pass the test, we can determine the point at which they start to have problems, and their cardiologists may use a medication to suppress the heart rate to allow them to do the activity, or they may restrict how much they can do. Sometimes we need to place temporary, pretty stringent exercise restrictions on the patient for their safety.”
If a child who needs CPET is really young and has trouble using the equipment, lab members can use stress testing and estimate their peak VO2 based on how far they get in the stress test. The lab also assesses young adults with hypertension or congenital heart disease into their twenties or sometimes even early thirties.
Columbia’s pulmonology team prescribes CPET to diagnose children with lung disease or asthma; in that case Dr. Layton measures carbon dioxide output, an informative measure of overall function, and whether their airway is becoming constricted when they exercise.
While CPET is becoming standard of care at major children’s hospitals, especially for children with congenital heart defects, many pediatric cardiologists don't use the testing or don't use it as often as they could, says Dr. Layton. “It's not used much among pediatric cardiologists in the community because it's not always accessible, and there are a lot of nuances with exercise testing. If you don't do it all the time, then it's hard to have the rapport with the patient that’s needed to get consistent results.”
