Use of Oxygen Pulse in Predicting Doppler-Derived Maximal Stroke Volume in Adolescents

Clinical exercise physiologists and physicians administering stress tests in the young have used oxygen pulse as a surrogate measure of stroke volume. It is important to recognize 1) the accuracy of O₂ pulse in predicting maximal stroke volume during exercise, and 2) the normal pattern of O₂ pulse during a progressive exercise test. This study examined both of these issues in a cohort of 44 healthy adolescent males and females (ages 14-16 years) who performed routine progressive cycle exercise to exhaustion. Gas exchange variables were measured by standard open circuit techniques. Stroke volume at rest and during exercise was assessed by the Doppler ultrasound method. At peak exercise O₂ pulse correlated closely with stroke volume (r = .73) with a SEE of 12.6 ml·beat⁻¹. Values of maximal O₂ pulse in nonathletic boys and girls were 13.3 ± 2.5 and 11.0 ± 1.7 ml·beat⁻¹, respectively. After the initial workload, a steady rise was observed in O₂ pulse, entirely reflecting an increasing arterial venous oxygen difference, with a slope of approximately 4 ml/beat per 100 watts work load. The findings support the use of O₂ pulse as a valid predictor of stroke volume during exercise in youth with a moderately high level of accuracy.