In medicine oxygen saturation (SO2), commonly abbreviated as "sats", measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. At low partial pressures of oxygen, most hemoglobin is deoxygenated.
Saturation of Peripheral Oxygen (SpO2) is an estimation of the oxygen saturation level usually measured with a pulse oximeter device.
Pulse oximetry is a non-invasive method allowing the monitoring of the oxygenation of a patient's hemoglobin.
A sensor is placed on a thin part of the patient's anatomy, usually a fingertip or earlobe, or in the case of a neonate, across a foot, and a light containing both red and infrared wavelengths is passed from one side to the other. Changing absorbance of each of the two wavelengths is measured, allowing determination of the absorbencies due to the pulsing arterial blood alone, excluding venous blood, skin, bone, muscle, fat, and (in most cases) fingernail polish. Based upon the ratio of changing absorbency of the red and infrared light caused by the difference in color between oxygen-bound (bright red) and oxygen unbound (dark red or blue, in severe cases) blood hemoglobin, a measure of oxygenation (the per cent of hemoglobin molecules bound with oxygen molecules) can be made.
Pulse oximeters are of critical importance in emergency medicine and are also very useful for patients with respiratory or cardiac problems.
You should know oximetry is not a complete measure of respiratory sufficiency. A patient suffering from hypoventilation (poor gas exchange in the lungs) given 100% oxygen can have excellent blood oxygen levels while still suffering from respiratory acidosis due to excessive carbon dioxide.
It is also not a complete measure of circulatory sufficiency. If there is insufficient blood flow or insufficient hemoglobin in the blood (anemia), tissues can suffer hypoxia despite high oxygen saturation in the blood that does arrive.
Spo2- 95% and above Normal healthy individual
Spo2- 91% - 95% Clinically acceptable, but low. Patient may be a smoker, or be unhealthy.
Spo2- 70% - 90% Hypoxemia. Unhealthy and unsafe level.
Spo2- below 70% Extreme lack of oxygen, ischemic diseases may occur.
An SaO2 (arterial oxygen saturation) value below 90% is termed hypoxemia. Hypoxaemia (or hypoxemia) is an abnormal deficiency in the concentration of oxygen in arterial blood.
Hypoxia is an abnormally low oxygen availability to the body or an individual tissue or organ.
Here are a few or the many causes of hypoxia- a decrease in oxygen saturation of the blood caused by sleep apnea, hypopnea (abnormally shallow breathing or slow respiratory rate) or inadequate pulmonary ventilation (e.g., in chronic obstructive pulmonary disease or respiratory arrest).