Pulse Oximetry

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is pulse oximetry?

Pulse oximetry is the use of a device—a pulse oximeter—to measure oxygen levels in the blood. The device reports your oxygen saturation level (O2 sat), or the percentage of hemoglobin in the blood that is bound to oxygen.

Hemoglobin is the part of the blood that carries oxygen molecules throughout the body. Your oxygen saturation level is a percentage of much oxygen your blood is carrying compared to the maximum it can carry.

Normal oxygen saturation levels as measured by pulse oximetry are 95 to 100% for adults. If your oxygen saturation drops below 90%, you may need medical treatment and supplemental oxygen.

Why is pulse oximetry performed?

Pulse oximetry can quickly, easily and painlessly measure blood oxygen levels. A lower-than-normal pulse oximetry result suggests the body may not be getting the oxygen it needs to function efficiently. When your oxygen levels are low, the heart may pump harder or faster to try to increase the amount of oxygen in your blood. If oxygen levels remain low for too long, cell and organ damage can occur.

Pulse oximetry allows healthcare providers and patients to monitor oxygen levels and intervene with medical treatment if necessary. Prompt treatment of low oxygen levels can prevent damage to the body.

Who performs pulse oximetry?

In healthcare settings, physicians, nurses, respiratory therapists and nursing assistants may perform pulse oximetry. Patients, family members and caregivers can also perform pulse oximetry at home.

The pulse oximeters used by healthcare providers are prescription oximeters that have undergone clinical testing to confirm their accuracy. Healthcare providers also undergo training to ensure proper use of pulse oximetry.

The pulse oximeters that can be purchased over the counter or online do not necessarily undergo clinical testing and do not undergo review by the U.S. Food and Drug Administration. Pulse oximeters purchased by consumers may not be as accurate as those in hospitals and clinics.

Who performs pulse oximetry?

Most pulse oximeters include a small clip-like device that is gently placed on the tip of one finger. Some pulse oximetry probes can be placed on an earlobe instead. In healthcare settings, the probe may include a sticky adhesive and may be placed on either your forehead or finger.

The probe emits red and infrared light. Because red light is primarily absorbed by deoxygenated blood and infrared light by oxygenated blood, the device can measure your oxygen saturation level. It typically takes only a few seconds to perform pulse oximetry.

If continuous monitoring of blood oxygen levels is desired, clinicians can secure the probe in place and monitor your oxygen saturation levels from moment to moment, for as long as necessary.

What are the risks and potential complications of pulse oximetry?

Pulse oximetry is very safe. If the pulse oximetry probe is held in place with adhesive over a period of time, there is a risk of skin irritation.

How do I prepare for pulse oximetry?

If you are wearing fingernail polish, you may be asked to remove your polish from at least one finger prior to pulse oximetry. Nail polish can interfere with the absorption of light from the pulse oximeter and may lead to inaccurate readings.

What can I expect after pulse oximetry?

Your healthcare provider will probably share your pulse oximetry reading with you almost immediately. If your oxygen saturation level is in the normal range (95 to 100%), additional intervention may not be necessary.

If your oxygen saturation level is low, your healthcare provider will consider your pulse oximetry reading in the context of your overall health. Lower-than-normal oxygen saturation levels may be expected for some people with certain medical conditions, such as chronic obstructive pulmonary disease (COPD).

In a hospital setting, physicians often order supplemental oxygen if your oxygen saturation level is less than 90%. Your healthcare providers will also work to detect and correct the underlying cause of your lower oxygen levels, if possible.

If you are at home and detect low blood oxygen levels, call your healthcare provider. Your healthcare provider will tell you what to do next. If your oxygen levels are low and you are having difficulty breathing, seek immediate care (call 911).

Periodic rechecks of your blood oxygen levels via pulse oximetry help your healthcare providers monitor your health and adjust your treatment plan, if needed.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jun 27
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