What is pulse oximetry?
A pulse oximetry test may clip to a finger to read blood flow.
Every system and organ in the body needs oxygen to survive. Without oxygen, cells begin to malfunction and eventually die. Cell death can cause severe symptoms and ultimately lead to organ failure.
The body transports oxygen to the organs by filtering it through the lungs. The lungs then distribute oxygen into the blood via hemoglobin proteins in red blood cells. These proteins provide oxygen to the rest of the body.
Pulse oximetry measures the percentage of oxygen in hemoglobin proteins, called oxygen saturation. Oxygen saturation usually indicates how much oxygen is getting to the organs.
Normal oxygen saturation levels are between 95 and 100 percent. Oxygen saturation levels below 90 percent are considered abnormally low and can be a clinical emergency.
How it works
Oxygen is distributed into the blood in red blood cells.
Pulse oximeters are clip-on devices that measure oxygen saturation. The device may be attached to a finger, a wrist, a foot, or any other area where the device can read blood flow.
Oxygen saturation can drop for many reasons, including:
suffocation
choking
infections, such as pneumonia
drowning
diseases, such as emphysema, lung cancer, and lung infections
inhaling poisonous chemicals
heart failure or a history of heart attacks
allergic reactions
general anesthesia
sleep apnea
Pulse oximeters work by shining a light through a relatively transparent area of the skin. The light shines through to a detector positioned on the other side of the skin.
For example, when a pulse oximeter is clipped onto a finger, one side of the clip shines the light, and the other detects it.
The amount of light absorbed by the blood indicates the oxygen saturation. A pulse oximeter does not directly measure oxygen saturation but instead uses a complex equation and other data to estimate the exact level.