Medical oxygen is mostly concentrated oxygen which is a minimum of 90% pure with moisture removed to a -100 deg F dew-point and has quite a few uses especially in the restoration of tissue oxygen tension by improving oxygen availability in a wide range of conditions.
Nitrogen is significantly important to the chemical industry where it is used to make fertilisers, nitric acid, nylon, dyes and explosives. In order to make these products, nitrogen must first be reacted with hydrogen to produce ammonia which is done by the Haber process.
Also known as laughing gas, nitrous oxide is a colourless, non-flammable gas, with a slightly metallic scent and taste when it is at room temperature. At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen. It is particularly useful in surgery and dentistry because of its anaesthetic properties.
Carbon dioxide is most often used in the medical field as an insufflation gas for minimal invasive surgery in order to enlarge and stabilize body cavities and to provide better visibility of the surgical area in question.
Helium is the second-lightest gas and is colourless, odourless, insipid and non-toxic in nature. It has a low boiling point, low density, low solubility, high thermal conductivity and inertness, so it proves useful for quite a few applications.