You have seen the runner gasp for air at the end of the race. The athletic term Oxygen Debt was coined because of the inadequate amount of oxygen to oxidize and remove the lactic acid from high-energy production oxygen deprivation. People who are out of shape gasp for air after minimal exercise. People feel invigorated after getting a breath of fresh air outside after leaving a stuffy room. The first thing that people who are very ill receive in the hospital is pure oxygen.
Oxygen deprivation is one of the main causes of weakening of the immune system.
In the inverse, increased oxygenation strengthens the immune system. It is not hard to realize how important oxygen is.