At what level is low blood oxygen harmful for children with copd?

See below. Children usually don't have copd, this is a disease of the adult. Children may have congenital lung diseases but the physiology of those is not the same as copd. Blood oxygen levels less than 90% are generally not desired. Hope this helps.
See below. I assume you are referring to "children with bpd." oxygen saturation below 90% while awake would require further evaluation and change in treatment modality.