CONGENITAL CENTRAL HYPOVENTILATION SYNDROME - CARDIORESPIRATORY RESPONSES TO MODERATE EXERCISE, SIMULATING DAILY ACTIVITY

Children with congenital central hypoventilation syndrome (CCHS) lack normal awake ventilatory responses to hypoxia and hypercarbia, yet eng age in daily activities typical of similarly aged children. Our patien ts with CCHS are assessed annually with a walking treadmill protocol t o 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 durati ons and reach tower 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, venti lation, and heart rate than normal children. Seven children with CCHS [mean age, 6.9 +/- 3.0 (SD) years] who required 24 h/day ventilatory s upport (diaphragm pacers while awake and mechanical Ventilation asleep ) and 7 controls performed a walking protocol on a treadmill with prog ressive increments in speed and incline. Hemoglobin saturations (SaO(2 )), end-tidal carbon dioxide concentrations (E(T)CO(2)), and heart rat es (HR) were recorded at baseline conditions, during activity and duri ng recovery. There were no significant differences between children wi th CCHS and controls in baseline values, duration of activity, peak sp eed, and incline achieved during walking and recovery time to baseline once the treadmill had stopped. However, children with CCHS became si gnificantly 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 opportu nity to adjust clinical management in children with CCHS by providing specific recommendations to parents about appropriate levels of activi ty for their children with CCHS. Although such was not the intent of t he current research, this study will suggest further investigation int o improved ventilatory support for these children during exercise. (C) 1995 Wiley-Liss, Inc.