The body maintains a stable level of<unk> for the most part by chemical processes of aerobic metabolism associated with breathing. Using the respiratory system, red blood cells, specifically the hemoglobin, gather oxygen in the lungs and distribute it to the rest of the body. The needs of the body's blood oxygen may fluctuate such as during exercise when more oxygen is required or when living at higher altitudes. A blood cell is said to be "saturated" when carrying a normal amount of oxygen. Both too high and too low levels can have adverse effects on the body.
Oxygen saturation 
Blood gas tension
Respiratory rate
Oxygenation index
Blood pressure
Fraction of inspired oxygen
Heart rate
Breathing gas