P137 Diagnosis of nocturnal hypoventilation in children with neuromuscular disorders by polysomnography – a survey of clinical practice in Australia and New Zealand

BACKGROUND: Diagnosis of nocturnal hypoventilation requires measurement of pCO2 during sleep, which can occur via exhaled gas (capnography) or transcutaneous methods. Different national and international definitions of hypoventilation exist, which may contribute to significant variation in clinical practice. METHODS: An electronic survey was completed by pediatric sleep physicians in Australia and New Zealand to determine how pCO2 was measured during polysomnography, what pCO2 data was available to reporting physicians/included in the report and which definitions of hypoventilation physicians use. RESULTS: More than two thirds (70%) of physicians indicated that in their centre pCO2 was collected via transcutaneous measurement only and 30% by both transcutaneous and end-tidal measurement. Twelve definitions of hypoventilation were used, including published definitions from the American Academy of Sleep Medicine manual and the pediatric Australasian Sleep Association/Australasian Sleep Technologists Association recommendations. The most commonly used definition was an increase in pCO2 >50mmHg for >25% total sleep time. The percentage of total sleep time with pCO2 >50mmHg was routinely included in the report and/or easily available in the raw data for 70% of physicians. DISCUSSION: There was significant variation and lack of standardisation within Australia and New Zealand when measuring and reporting pCO2 during polysomnography as well as definitions of hypoventilation used by pediatric sleep physicians. The Australasian Sleep Association/Australasian Sleep Technologists Association recommendations were not frequently used, possibly due to relevant information not being available to reporting physicians, recommendations being irrelevant and/or outdated and excessive cognitive load associated with remembering multiple definitions.