Congenital central hypoventilation syndrome: Cardiorespiratory responses to moderate exercise, simulating daily activity

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Abstract
Children with congenital central hypoventilation syndrome (CCHS) lack normal awake ventilatory responses to hypoxia and hypercarbia, yet engage in daily activities typical of similarly aged children. Our patients with CCHS are assessed annually with a walking treadmill protocol to assess physiologic responses to different levels of simulated daily activity. We hypothesized that children with CCHS (compared with age- and sex-matched healthy controls) would (1) exercise for shorter durations and reach lower peak speed and incline on the treadmill; (2) become more hypoxemic, more hypercarbic, and develop less tachycardia during activity; and (3) take longer to return to baseline oxygenation, ventilation, and heart rate than normal children. Seven children with CCHS [mean age, 6.9 ± 3.0 (SD) years] who required 24 h/day ventilatory support (diaphragm pacers while awake and mechanical ventilation asleep) and 7 controls performed a walking protocol on a treadmill with progressive increments in speed and incline. Hemoglobin saturations (SaO2), end-tidal carbon dioxide concentrations (ETCO2), and heart rates (HR) were recorded at baseline conditions, during activity and during recovery. There were no significant differences between children with CCHS and controls in baseline values, duration of activity, peak speed, and incline achieved during walking and recovery time to baseline once the treadmill had stopped. However, children with CCHS became significantly more hypoxemic and hypercarbic during activity (P < 0.05), and they had a lower percent increase in HR during treadmill walking than controls (P < 0.05). These results offer the clinician an opportunity to adjust clinical management in children with CCHS by providing specific recommendations to parents about appropriate levels of activity for their children with CCHS. Although such was not the intent of the current research, this study will suggest further investigation into improved ventilatory support for these children during exercise. Pediatr Pulmonol. 1995; 20:89–93.