Significance

Low levels of oxygen in the blood can signal poor lung or heart function. A low pulse oximetry reading may indicate the need for supplemental oxygen.

Test

The health-care provider attaches a flexible clip, typically to a fingertip or earlobe. Wires run from the clip to a device called an oximeter. In the case of a routine doctor visit, the clip remains in place for just a moment. Critical-care patients can wear it continuously without discomfort.

How it Works

Oxygen-hungry blood absorbs less infrared light. The inner portion of the pulse oximetry clip has a light on one side that emits infrared waves, and a device on the other side that measures absorption rates. As your blood beats through your fingertip/earlobe, the information passes to the oximeter, which calculates the percent of oxygen saturation in the blood.

Uses

Beyond calculating whether a patient might need supplemental oxygen, pulse oximetry can help determine if medications used to treat asthma, emphysema or other lung conditions are working. When used overnight or with exercise, pulse oximetry might also indicate problems like sleep apnea or exercise-induced asthma.

Limitations

While pulse oximetry is valuable, it is much less accurate than other, more invasive studies such as arterial blood gas analysis.

Source:

National Institutes of Health: Lung Function Tests

Mayo Clinic: Emphysema