Physiologic decrease of ventilatory response to exercise in the second decade of life in healthy children.

BACKGROUND

Cardiopulmonary exercise testing is increasingly used in children with congenital heart defects. Because of changes related to growth, the interpretation of exercise test results heavily relies on the presence of normative data. There is growing interest in the assessment of the ventilatory response to exercise in children with congenital heart disease, but normative data are lacking.

METHODS

We studied 243 consecutive children (age, 13.2 ± 2.1 years; 128 boys) with maximal cardiopulmonary exercise testing. All children had normal clinical examination and echocardiograms. In all children, the slope of the relationship between minute ventilation and carbon dioxide production (VE/VCO(2) slope) was calculated using both only data until the respiratory compensation point (VE/VCO(2RC)) and using data until peak exercise (VE/VCO(2Peak)).

RESULTS

The exercise test was maximal in all children (peak respiratory exchange ratio, 1.2 ± 0.1). For all the cohorts, VE/VCO(2Peak) slope was 28.2 ± 3.7; and VE/VCO(2RC) slope was 24.5 ± 3.0, whereas peak oxygen uptake was 94.6% ± 14.0% of predicted value. Baseline spirometric function was normal in all children (vital capacity, 100% ± 14% and forced expired volume in the first second 97% ± 13% of predicted). From the age of 10 to 16 years, we observed a progressive decrease in both VE/VCO(2Peak) and VE/VCO(2RC) slopes (-0.833 and -0.705 per each year), with the highest reduction observed in boys. Gender-specific percentiles for both VE/VCO(2Peak) and VE/VCO(2RC) slopes were constructed.

CONCLUSION

Ventilatory response to exercise expressed as VE/VCO(2) slope seems to decrease progressively in the second decade of life. Because of age-related changes, interpretation of VE/VCO(2) slopes in this age range should be based on the reported percentiles rather than on the absolute values.