Objectives Few data on alveolar hypoventilation in Prader-Willi syndrome (PWS) are available.The respiratory follow-up of these patients is not standardized. The objectives of this study were to evaluate the prevalence of alveolar hypoventilation in pediatrics and to identify its risk factors.

Study design This retrospective study included children with PWS recorded by polysomnography (PSG) with transcutaneous carbon dioxide (CO2) measurement (PtcCO2) or expired CO2 (ETCO2), between 2007 and 2021, in a tertiary hospital center. The primary outcome was the presence of alveolar hypoventilation defined as partial pressure of carbon dioxide (pCO2) ? 50 mmHg during ? 2% of sleeping time.

Results Among the 57 included patients (38 boys, median [range] age: 4.8 years [0.1-15.6], 60% treated with GH, 37% obese), 19 (33%) had moderate to severe OSAS (obstructive apneahypopnea index ? 5/h) and 20 (35%) had hypoventilation. The median (range) pCO2 max was 49 mmHg (38-69). 25% of patients with hypoventilation were not symptomatic. Hypoventilation was significantly more frequent with age (a majority between 8 and 16 years) and GH treatment, and independent from sex, BMI, obstructive or central apnea-hypopnea index.

Conclusion The frequency of alveolar hypoventilation in children and adolescents with PWS is of concern and increases with age. A regular screening by oximetry-capnography would seem to be indicated whatever the sex, the BMI, the rate of obstructive or central apneas, the presence of a GH treatment or not.

Key words Prader-Willy syndrome, child, polysomnography, sleep-disordered breathing, alveolar hypoventilation, growth hormone