Nitrous oxide and oxygen came in cylinders. Metal was needed for munitions and was therefore in short supply. Obtaining a supply of nitrous oxide was therefore difficult.
Nitrous oxide was used during the First World War (often without oxygen) for short operations. It could be used by skilled administrators with local anaesthesia for abdominal surgery and high leg amputations.
Oxygen was discovered by Joseph Priestley in 1774. Modern medical use of oxygen became more popular in 1917 due to the work of J S Haldane.
First isolated in 1804 by Friedrich Sertürner in Germany and distributed in 1817. It was more widely used after the invention of the hypodermic needle in 1853. It was used to treat wounded soldiers in Advanced Dressing Stations during the First World War, and was developed for self-administration in World War Two.
First produced in 1910, this derivative of morphine, omnopon is a powerful analgesic. In the First World War, it was given to wounded soldiers suffering from shock in Casualty Clearing Stations.