Cardiopulmonary exercise performance in prematurely born children

Prematurely born children have reduced peak V̇o₂ compared with their peers, inferentially attributed to ventilatory limitation. The primary purpose of this study was to compare exercise ventilation and cardiac output in a sample of childhood survivors of lung disease of prematurity with those of a control group to elucidate reasons for lower peak V̇o₂. A secondary aim was to describe and compare the ventilatory response to incremental exercise. Thirty-two children, aged 8-9 y, were recalled for lung function and progressive exercise tests. Fifteen of them also performed submaximal exercise with measurement of cardiac output (indirect [CO₂] Fick) and physiologic dead space. Results were compared with those of term-born, age- and sex-matched, control children. Pulmonary function tests showed mild airflow limitation. Peak V̇o₂ was lower in prematurely born children compared with control children, and was correlated with lean body mass. Their heart rate-V̇o₂ relationship and stroke volume were similar to that of term-born control children. Children with a history of bronchopulmonary dysplasia and hyaline membrane disease as infants exhibited greater exercise hyperpnea than did healthy control children, because of higher breathing frequency, and maintained lower end-tidal Pco₂ during submaximal exercise. Physiologic dead space normalized for body weight was similar in preterm and term-born children. Lower peak V̇o₂ in this population is not caused by cardiopulmonary factors, but is best predicted by lean body mass. Ventilation did not limit exercise performance, although it appears that breathing during exercise is regulated differently in prematurely born children than in term- born children.