Abstract
STUDY OBJECTIVES: Evaluate the relative contributions of weight status and obstructive sleep apnea (OSA) to cardiopulmonary exercise responses in children. DESIGN: Prospective, cross-sectional study. Participants underwent anthropometric measurements, overnight polysomnography, spirometry, cardiopulmonary exercise function testing on a cycle ergometer, and cardiac doppler imaging. OSA was defined as ≥ 1 obstructive apnea or hypopnea per hour of sleep (OAHI). The effect of OSA on exercise function was evaluated after the parameters were corrected for body mass index (BMI) z-scores. Similarly, the effect of obesity on exercise function was examined when the variables were adjusted for OAHI. SETTING: Tertiary pediatric hospital. PARTICIPANTS: Healthy weight and obese children, aged 7-12 y. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Seventy-one children were studied. In comparison with weight-matched children without OSA, children with OSA had a lower cardiac output, stroke volume index, heart rate, and oxygen consumption (VO2 peak) at peak exercise capacity. After adjusting for BMI z-score, children with OSA had 1.5 L/min (95% confidence interval -2.3 to -0.6 L/min; P = 0.001) lower cardiac output at peak exercise capacity, but minute ventilation and ventilatory responses to exercise were not affected. Obesity was only associated with physical deconditioning. Cardiac dysfunction was associated with the frequency of respiratory-related arousals, the severity of hypoxia, and heart rate during sleep. CONCLUSIONS: Children with OSA are exercise limited due to a reduced cardiac output and VO2 peak at peak exercise capacity, independent of their weight status. Comorbid OSA can further decrease exercise performance in obese children.