RecruitingDevice studyComparison of a Demand Oxygen DeliveryConducting a randomized control trial of oxygen in children with Down syndrome to treat moderate to severe obstructive sleep apnea. The aim of the study is to conduct a comparison between the 2 methods of oxygen delivery during sleep in 15 children from Cincinnati Children's Hospital and Children's Hospital of Los Angeles. 2 polysomnographies will be performed, one with continuous flow and the second with pulse flow.