Oxygen, is a lung friendly chemical element discovered by three researchers, working independently in the 1770's in England, Sweden, and France. Abundant in the earth's atmosphere for 2.3-2.4 billion years, air is typically 21% oxygen, required by humans for proper cell metabolism. Scientists contend that during a period of geologic history oxygen constituted 35% of the earth's atmosphere. Such a high concentration of oxygen was too high to sustain life on earth as we know it. 21% is optimal for sustaining life on our planet.
Aside from it being essential for cellular metabolism in humans, oxygen is used by humans for: residential heating, combustion engines, production of steel, plastics, and textiles. The use of supplemental oxygen for therapeutic purposes is common for medical conditions such as trauma, resuscitation, shock, hypothermia, COPD, cystic fibrosis, cluster headaches, carbon monoxide poisoning, etc. A canister of oxygen for medicinal home use costs $150 in Brazil and $400 in the USA. Oxygen can be administered by several different means, including nasal cannula, face mask, and hyperbolic chamber.
Hyperbolic chambers are used primarily to regulate oxygen levels in closed chambers used by divers in submersibles or submarine activity. Such chambers have been in use for more than 100 years, since 1904. Since oxygen has vasoconstrictive effects on the human circulatory system, those who explore the ocean deep looking for sunken treasure or researchers of marine hyperbolic chambers when transitioning in descent or ascent to change cabin pressure. Without such regulation divers can develop "palsy" or "the bends", a type of paralysis which will lead to death.