Ventilatory Response to CO2 During Exercise in Patients With Congenital Central Hypoventilation Syndrome.
Congenital central hypoventilation syndrome (CCHS) is characterized by a markedly impaired ventilatory response to CO2 due to central chemoreceptor dysfunction. Although inadequate ventilation and hypercapnia during exercise have been reported, ventilatory response during exercise has not been quantitatively evaluated in CCHS. This study aimed to quantify ventilatory response during exercise and compare it with that at rest.
Ten patients with genetically confirmed CCHS underwent cardiopulmonary exercise test (CPET) using a stepwise incremental treadmill protocol with breath-by-breath respiratory gas analysis. CPET was terminated when end-tidal CO2 (EtCO2) increased by at least 2% (15.2 mmHg) from baseline. Ventilatory response to CO2 (VRCO2) was calculated as Δminute volume (MV)/ΔEtCO2/body weight (mL/min/mmHg/kg). VRCO2 at rest was measured using the CO2 rebreathing method. Data are presented as median (interquartile range [IQR]).
Age was 13.5 (12.3-15.5) years, and exercise duration was 5 min 53 s (4 min 47 s-6 min 56 s). Although MV increased during exercise, SpO2 decreased and EtCO2 increased, indicating hypoventilation. VRCO2 during exercise was 2.27 (1.61-3.16), not significantly different from VRCO2 at rest, 1.56 (1.07-2.83) (p = 0.85). VRCO2 was markedly lower than values in healthy children (34.6 (29.3-42.8)). No patients reported dyspnea, and no serious adverse events occurred.
VRCO2 during exercise remains profoundly low in CCHS. No significant difference from VRCO2 at rest was detected, suggesting persistent impairment of CO2-driven ventilatory control despite increased metabolic demand. These findings provide insight into exercise-related hypoventilation in CCHS and underscore the importance of objective physiological assessment to support cautious and individualized clinical judgment rather than subjective symptoms.
Ten patients with genetically confirmed CCHS underwent cardiopulmonary exercise test (CPET) using a stepwise incremental treadmill protocol with breath-by-breath respiratory gas analysis. CPET was terminated when end-tidal CO2 (EtCO2) increased by at least 2% (15.2 mmHg) from baseline. Ventilatory response to CO2 (VRCO2) was calculated as Δminute volume (MV)/ΔEtCO2/body weight (mL/min/mmHg/kg). VRCO2 at rest was measured using the CO2 rebreathing method. Data are presented as median (interquartile range [IQR]).
Age was 13.5 (12.3-15.5) years, and exercise duration was 5 min 53 s (4 min 47 s-6 min 56 s). Although MV increased during exercise, SpO2 decreased and EtCO2 increased, indicating hypoventilation. VRCO2 during exercise was 2.27 (1.61-3.16), not significantly different from VRCO2 at rest, 1.56 (1.07-2.83) (p = 0.85). VRCO2 was markedly lower than values in healthy children (34.6 (29.3-42.8)). No patients reported dyspnea, and no serious adverse events occurred.
VRCO2 during exercise remains profoundly low in CCHS. No significant difference from VRCO2 at rest was detected, suggesting persistent impairment of CO2-driven ventilatory control despite increased metabolic demand. These findings provide insight into exercise-related hypoventilation in CCHS and underscore the importance of objective physiological assessment to support cautious and individualized clinical judgment rather than subjective symptoms.
Authors
Ikeda Ikeda, Hasegawa Hasegawa, Yamada Yamada, Wasa Wasa, Kanabuchi Kanabuchi
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