O018 Improvement in Obstructive Sleep Apnoea Improves Heart Rate response to Obstructive Respiratory events in Children with Down syndrome.

BACKGROUND: Children with Down syndrome (DS) have a much higher predisposition to obstructive sleep apnoea (OSA) compared to typically developing (TD) children. Children with DS have a lower heart rate (HR) response to respiratory event termination compared with TD children matched for age, sex and OSA severity, but the effect of improvement in OSA severity over time or with treatment is unknown. We compared the HR surge at event termination in children with DS with improved OSA to those with unimproved OSA 2 y following baseline study. METHODS: 24 children (3-19 y at baseline) were included. Children were grouped into Improved (decrease in obstructive apnoea hypopnoea index (OAHI) to ≤ 50% of baseline OAHI; n=12; 7 treated between studies) and Unimproved (n=12; 2 treated between studies). Beat-to-beat HR was averaged 10s before (pre), during and the peak after (post) each obstructive event during sleep, and expressed as percentage change. RESULTS: 583 obstructive events at baseline and 435 at follow up were identified. % change in HR from during the event to post event was greater at follow up (mean±sem, 22.4%±0.9%) than baseline (19.0%±0.8%; p<0.01) in the improved group, but reduced at follow up (16.8%±1.1%) compared with baseline (21.1%±0.7%; p<0.001) in the unimproved group and was greater at follow up in the improved group than in the unimproved group (p<0.001). CONCLUSION: These results suggest that the dampened HR response to events seen in DS is reversible, adding weight to the need for diagnosis and management of OSA in this population.