Cardiopulmonary Capacity in Children During Exercise Testing: The Differences Between Treadmill and Upright and...

Area of Science:

• Pediatric Cardiology
• Exercise Physiology
• Pulmonology

Background:

• Cardiopulmonary exercise testing (CPET) is crucial for assessing cardiopulmonary health and prognosis in children with cardiac and pulmonary conditions.
• Simultaneous imaging techniques like cardiac MRI and PET-scan with exercise testing necessitate understanding normal cardiopulmonary function across various postures.
• Knowledge of children's normal cardiopulmonary responses in different body positions and exercise modalities is limited.

Purpose of the Study:

• To investigate the impact of different body positions on cardiopulmonary function during CPET in healthy children.
• To compare cardiopulmonary responses between treadmill and various bicycle exercise positions (sitting, tilted, supine).

Main Methods:

• Thirty-one healthy children (ages 9, 12, 15) underwent four CPETs: one treadmill (modified Bruce protocol) and three bicycle tests (sitting, 45° tilt, supine).
• Bicycle tests used a 20-watt ramp protocol with continuous ECG and breath-by-breath gas exchange measurements.
• Transthoracic echocardiography assessed cardiac structure/function and aortic diameter; Doppler measured aortic blood velocity.
• Pulmonary function tests, including maximum voluntary ventilation, were performed before each CPET.

Main Results:

• Peak oxygen uptake (VO2) was significantly lower in all bicycle tests compared to the treadmill test (p < 0.05).
• Corrected peak VO2 (ml kg-0.67 min-1) was lower in the supine position versus the upright bicycle test, but relative peak VO2 (ml kg-1 min-1) showed no difference.
• Peak heart rate decreased progressively from treadmill to upright bicycle to supine tests.
• No significant differences in peak stroke volume or cardiac output were observed between bicycle modalities.

Conclusions:

• Peak cardiac output is comparable between upright and supine bicycle tests.
• Supine bicycle testing results in lower heart rate and corrected peak VO2 compared to upright.
• Treadmill testing elicits higher absolute and relative peak VO2.
• Both upright and supine bicycle CPETs are clinically applicable despite observed differences in physiological responses.