It measures the content of oxygenated hemoglobin in your red cells. While not as accurate as a blood test, it is readily available. Oxygen saturation
is expressed as a percentage, a number ranging from 0 to 100, normally on room air, the oxygen saturation is greater than 98%. The saturation reflects the content in the blood reasonably well in the range of normal range of acid levels and oxygen in most individuals. However, the saturation is affected by the amount of inhaled oxygen, the respiratory drive to pull oxygen into your lungs, changes in acid levels in the blood (such as seen in severe infections or kidney failure
), problems with the lungs itself (such as excess fluid or pneumonia
). After surgery, the combined effects of anesthesia
and narcotics tend to depress the respiratory system
, such that oxygen is not being drawn into the lungs (usually because of oversedation). This leads to less oxygen in the lungs and a drop in the oxygen levels and thus a drop in the saturation - thus the term: "de-sat" or desaturation. This can be easily remedied by reducing narcotics, or reversing narotic effect (e.g. Narcan
), arousing the individual, and/or adding supplemental oxygen. Thus the use of the oxygen mask
, which increases the saturation, but does not address the reason for oversedation.