Oxygen was known to be the only element that supports respiration as early as 1800 and was first used in the medical field in 1810. However, it took about 150 years for the gas to be used throughout medicine. In the early to mid 20th century oxygen therapy became rational and scientific, and today modern medicine could not be practiced without the support that oxygen supplies.
Medical oxygen is used to:
provide a basis for virtually all modern anaesthetic techniques
restore tissue oxygen tension by improving oxygen availability in a wide range of conditions such as COPD, cyanosis, shock, severe hemorrhage, carbon monoxide poisoning, major trauma, cardiac/respiratory arrest.