see: [RCH Nitrous Oxide Oxygen Mix](x-devonthink-item://A8575F8D-29A2-4CBF-83D5-2E2B42698C17) [Austin - nitrous oxide toxicity](x-devonthink-item://A8B1FF54-123F-4101-8CA4-A62ECB63D607) #paeds #anaesthetics **contraindications in ED** - gas-filled space: [[pneumothorax]], [[Bowel obstruction]], severe head injuries or recent brain surgery - airway or breathing compromise: severe COPD or current asthma exacerbation - [[Diving injuries and Dysbarism|Decompression illness]] or recent dive - patient requiring > 50% oxygen - intoxication or depressed conscious state - pregnancy (relative) - pulmonary hypertension - ↑ risk of N2O-induced bone marrow suppression (eg methionine synthase deficency, homocystinuria, methylmalonic academia)