The human body needs approx. 400 litres of oxygen (O2) each day. Oxygen keeps the cells in your body alive and functioning. Transporting this amount of oxygen requires a "carrier" – haemoglobin. The oxygen becomes attached to the haemoglobin in red blood cells and is then supplied to the organs via the bloodstream
Oxygen saturation (SaO2) = percentage of haemoglobin molecules that are carrying O2 in the arterial blood.
In healthy people, oxygen saturation is around 94% to 98%.