What Is Pulse Oximetry?

What to expect when undergoing this test

Hand with pulse oximeter
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In This Article

Pulse oximetry is a way of determining the oxygen level in your blood, which is an important indicator of your overall health. The test is noninvasive, which means it doesn't use a needle or other instrument that pierces the skin. Instead, pulse oximetry uses a probe or sensor that is placed on the forehead, earlobe, fingertip or even on the bridge of the nose to determine your blood oxygen levels. It's often used in emergency rooms or critical care settings, though it may also be used in some doctors' offices.

Purpose of Test

Pulse oximetry is a means of measuring oxygen saturation or the percentage of hemoglobin saturated with oxygen in arterial blood. This can be a useful tool in the management of chronic obstructive pulmonary disease (COPD) and other lung conditions to check pulmonary function, or how well your lungs are working.

In COPD, your doctor can use pulse oximetry to determine whether you need supplemental oxygen, and how much oxygen you might need. In the case of a sudden worsening of your condition, your doctor might use pulse oximetry to determine if you should be hospitalized.

There are many other conditions and situations where pulse oximetry provides useful information. For example, an anesthesiologist might use pulse oximetry to monitor your blood oxygen levels during or after sedation for surgery. In addition, in sleep apnea, pulse oximetry may detect times when a person's breathing stops.

Pulse oximeters are widely used in hospitals, clinics, doctor's offices, and homes. They're generally accurate and provide spot-on readings of oxygen saturation levels. This can be a valuable tool, especially in emergency situations. One recent study of COPD patients using pulse oximeters showed that the devices were highly effective in predicting when COPD symptoms suddenly got worse, known as exacerbations.

Risks and Contraindications

While there are generally no physical risks or side effects to using a pulse oximeter, like any medical device, pulse oximeters have their downsides, such as false readings. For example, studies have shown that the devices tend to be less accurate in critically ill patients and newborns.

An oximetry reading shouldn't be used as the sole indicator that something is medically wrong. Patients using a pulse oximeter at home (especially if the readings are conducted as spot checks or as one- or two-night measurements) are also cautioned to use common sense and interpret the readings with caution. Call your healthcare provider before taking any further action if a reading is out of the ordinary.

Other negatives to using pulse oximeters include:

  • They may provide a false reading. For example, you can be severely short of breath, but your oxygen saturation reading may be normal.
  • They may be ineffective in the presence of certain conditions, including cardiac or respiratory arrest, cardiac arrhythmias, shock, carbon monoxide poisoning, conditions that cause poor circulation or poor perfusion to the tissues, arteriovenous fistulas, cold extremities, edema, tremors, shivering, rigor, or muscle twitching. Even wearing black, green, or blue nail polish can affect the readings.
  • They may lag behind your condition. For example, the blood oxygen level (PaO2) could potentially decrease to a critical level before the decreased SpO2 (oxygen saturation reading) is displayed on the monitor.

Although widely accepted in clinical and home settings, pulse oximetry should never replace arterial blood gas analysis (considered the gold standard of blood oxygen measurement) and/or sound medical advice from your doctor. It should only be used as a screening tool when low blood oxygen levels are suspected.

During the Test

Your blood contains hemoglobin, which carries oxygen molecules from your lungs to where they're needed in your body. In pulse oximetry, we're actually measuring how much of the hemoglobin in your blood is carrying oxygen, and how much is not.

The procedure itself is fairly quick and should be painless:

  1. The device gently clamps onto your finger or another body part to measure your oxygen saturation.
  2. The probe that's clipped or placed on you uses light in specific wavelengths to measure oxygen saturation of your hemoglobin. Hemoglobin that's carrying oxygen absorbs this light differently than hemoglobin that isn't carrying oxygen, and the data collected by the probe will show the difference.

Since this is a simple procedure (about as easy as taking your blood pressure), pulse oximetry can be performed virtually anywhere: at your doctor's office, in the hospital, or at home.

In fact, you can purchase wearable pulse oximetry monitors for your wrist that will track your blood oxygen levels around the clock and potentially alert your physician or caregivers if the levels fall too low. You also can buy fingertip clip-on devices that will transmit blood oxygenation data to your smartphone.

Interpreting Results

Normal oxygen saturation levels range between 95 percent and 100 percent. Oxygen saturation levels in COPD and in other conditions, such as asthmalung cancerheart failure, and pneumonia, are typically lower.

Pulse oximetry should not replace, but rather complement, the use of spirometry in the diagnosis and management of chronic respiratory illnesses like COPD.

Pulse oximetry monitors are also useful for monitoring supplemental oxygen therapy, to determine if your levels should be titrated up or down depending on your needs.

Never titrate your oxygen levels without specific instructions from your healthcare provider.

A Word From Verywell

Pulse oximetry is a painless way to get an accurate measure of your blood oxygen saturation levels, and is a great tool for determining lung function, disease progression, and how well certain treatment methods are working.

However, never rely on a pulse oximeter to determine how you should be feeling. If your oxygen saturation level is normal but you're severely short of breath and/or are experiencing other troubling symptoms, seek emergency medical attention and notify your healthcare provider as soon as possible.

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Article Sources

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