Congenital central hypoventilation syndrome and ventilatory responses during cardiopulmonary exercise testing

Background: Previous studies have shown evidence of hypoxemia and hypercapnia during cardiopulmonary exercise test (CPET) evaluation in children with congenital central hypoventilation syndrome (CCHS). However, there are no longitudinal studies which compared CPET findings to polysomnogram (PSG) or PHOX2B mutation, to date.

Objectives: To describe the longitudinal CPET findings in a cohort of children with CCHS and correlate the findings to the PSG results.

Methods: This retrospective study was conducted in children with CCHS followed in the Long-term Ventilation Program at SickKids, Toronto, Canada between September, 2013 and January, 2020. CCHS genetic mutation, age of diagnosis, ventilatory support, family history, disease associations of CCHS, CPETs, and PSG parameters were recorded and analyzed.

Results: A total of nine patients with CCHS (46 CPETs and 46 PSGs) were enrolled. Four (44.4%) children had polyalanine repeat mutations. The mean (SD) age at the time of diagnosis and duration of ventilatory usage were 3.2 ± 3.4 years and 11.5 ± 2.8 years, respectively. All abnormal CPETs had hypercapnia in at least 1 phase of the exercise test. Hypercapnia (12/46; 26.1%) at peak of exercise was the most common abnormality. None of the children experienced an oxygen desaturation below 90%. End-tidal CO₂ (PetCO₂ ) at rest and at peak exercise in the CPETs were significantly correlated with PSG TcCO₂ while PetCO₂ at anaerobic threshold was correlated with CO₂ in pre-PSG capillary blood gas.

Conclusion: Nocturnal hypoventilation may impact the CPET results in CCHS children. Serial CPETs should be considered standard clinical care for all CCHS children.