Pulse oximetry is a non-invasive and painless test that measures your oxygen saturation, or the amount of oxygen in your blood. It can quickly detect small changes in the efficiency with which oxygen is transported to the limbs (including legs and arms) furthest from the heart. A pulse oximeter is a small clip-like device that can be attached to body parts such as toes or earlobes. It is most commonly found on the fingers and is usually used in intensive care settings such as emergency rooms or hospitals. Some doctors, such as pulmonologists, may use it in the office.
Purpose of using an oximeter
Pulse oximetry may be used to see if there is enough oxygen in the blood. This information is needed in many kinds of situations. It may be used:
- During or after surgery or procedures that use sedation
- To see how well lung medicines are working
- To check a person’s ability to handle increased activity levels
- To see if a ventilator is needed to help with breathing, or to see how well it’s working
- To check, a person has moments when breathing stops during sleep (sleep apnea)
Working principle
The device works by shining 2 lights (one red light and one infrared light) through your fingertip. Absorption of these lights can differ significantly between blood loaded with oxygen and blood lacking of oxygen. Blood loaded with oxygen absorbs more infrared light and lets more red light pass through it. Blood with not enough oxygen tends to absorb more red light and lets more infrared light pass through it. It is fast, simple and non-invasive (needle-free).
Normal and low blood oxygen levels
A normal blood oxygen level varies between 75 and 100 millimeters of mercury (mm Hg).
A blood oxygen level below 60 mm Hg is considered low and may require oxygen supplementation, depending on a doctor’s decision and the individual case.
When blood oxygen level is too low compared to the average level of a healthy person, it can be a sign of a condition known as hypoxemia. This means that the body has difficulty delivering oxygen to all of its cells, tissues, and organs.
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