Talk to Pediatrician on Cardiac Issue

Aoa my new born baby have a Down syndrome patient and two hole in heart.now he is thirty five days old almost previous thirty days admit in hospital because he suffer from nimoniya. Two days ago children hospital Lahore discharge baby and they said nimoniya almost clear and you should arrange oxygen cylinder at home because some time baby need oxygen but baby twinty four hours need oxygen whenever put out the oxygen baby oxygen level fall thirty six,fourthy I’m very worried about this situation please recommend expert medicine and advise I will also attach echo report and medicine