Oxygen saturation (medicine)
Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal blood oxygen levels in humans are considered 95–100 percent. If the level is below 90 percent, it is considered low resulting in hypoxemia. Blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels. Oxygenation occurs when oxygen molecules () enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.
Suicide bag
Inhalation of oxygen deficient or oxygen free gas not only fails to replenish oxygen used in normal metabolism, but causes the blood passing through the capillaries of the gas exchange regions of the lungs to lose residual oxygen in relation to the concentration difference between the oxygen in the alveolar air and in the blood in the alveolar capillaries. This causes a far quicker drop in blood oxygen level than holding the breath. The deoxygenated blood then passes through the systemic circulation to the vital organs, including the brain, and rapidly lowers oxygen concentrations below the level required to sustain consciousness, and when it is insufficient to keep the heart functioning, cardiac arrest will occur. For the most people, an alveolar oxygen tension of less than or 4% by volume at atmospheric pressure is not sufficient to support consciousness.