Sleep-related hypoventilation in children with Prader-Willi syndrome: Experience from two UK paediatric sleep centres

Although most children with Prader-Willi syndrome (PWS) have obstructive sleep apnoea syndrome (OSAS), the prevalence of sleep-related hypoventilation is unknown. We hypothesized that children with PWS have hypercapnia for higher proportion of sleep time (ST) than age- and BMI-matched control children with similar obstructive apnoea-hypopnoea index (OAHI). Methods: Children with PWS undergoing nocturnal polygraphy prior to growth hormone commencement were matched for age, BMI z-score and OAHI to otherwise healthy children with snoring, adenotonsillar hypertrophy and/or obesity. The interaction between PWS diagnosis and OSAS severity (OAHIu003e5/h vs. ≤5/h) regarding their effect on %ST with transcutaneous CO 2 (PtcCO 2 )u003e45 mmHg was explored using a general linear model. Results: 48 children with PWS and 93 controls were included (3.9±4.1 y.o. vs. 4.1±4 y.o.; BMI z-score 0.73±1.91 vs. 0.78±1.66; OAHI 3.2±6.7 vs. 2.7±6.2/h, respectively; Pu003e0.05 for all). For OAHIu003e5, children with PWS and controls had greater difference in %ST with PtcCO 2 u003e45 (PWS: 76.6±24.7% vs. controls: 40.3±37.2%) than for OAHI≤5 (PWS: 22.6±32.1% vs. controls: 17.9±27.1%). More specifically, the interaction between PWS and OSAS severity regarding their effect on %ST with PtcCO 2 u003e45 was significant after adjustment for age, gender and BMI z-score (P=0.03). Results did not change when hypoventilation was defined as PtcCO 2 u003e50 mmHg. Conclusion: During sleep, children with PWS and OSAS hypoventilate disproportionately to the degree of upper airway obstruction. This has potential pathophysiological implications but also demonstrates that simple oximetry studies are inadequate to monitor this group of patients.