Non-invasive ultrasonic cardiac output monitoring in exercise testing.

Background: The purpose of this study was to evaluate the relationship of breath-by-breath oxygen uptake (VO(2)) and CO, cardiac index (CI), stroke volume (SV) and heart rate (HR) determined by a non-invasive continuous wave (CW) Doppler-based system (USCOM) in healthy adolescent and adult athletes during exercise treadmill testing.

Methods: Twenty athletes were enrolled for a standardized ramp treadmill test including transthoracic echocardiography at rest, incremental breath-by-breath spiroergometry, lactate kinetics and CW Doppler.

Results: VO(2) max was 51+/-11 ml/min/kg in the adolescent cross country skiers (CI 8.