Recovery curves of oxygen uptake, following submaximal exercise, were studied in normal children and children with acyanotic and cyanotic congenital heart disease.
Oxygen uptake in normal children and patients with acyanotic heart disease returned rapidly to resting level following exercise. In cyanotic children, O2 uptake, following exercise, was greater at comparable work loads and returned to resting levels more slowly. The ventilation required to achieve a given O2 uptake was significantly greater than that in normal children, while heart rate was not as high as expected for the degree of their exhaustion.
The findings suggest that cyanotic children had a decreased efficiency of ventilation, exercised at a relatively greater percentage of their maximal working capacity, and had a noticeably decreased aerobic capacity compared to normal children or those with acyanotic heart disease.
Drakonakis AC, Halloran KH. Oxygen Consumption During Recovery From Exercise in Children With Congenital Heart Disease. Am J Dis Child. 1974;128(5):651–656. doi:10.1001/archpedi.1974.02110300061008