What is a Pulse Oximeter?
A pulse oximeter is a device that can quickly and painlessly measure the amount of oxygen in your blood. Pulse oximeters are also available for home use or in a smart phone app, but these devices may not be accurate and they are not regulated by the FDA.
If you have been to a doctor’s office or hospital in the last 30 years, you probably have had a pulse oximeter put on your fingertip to measure your pulse and the amount of oxygen being carried by your red blood cells, called your oxygen saturation. Pulse has always been easy to measure, but before pulse oximeters, getting an oxygen saturation level required a blood draw from an artery, called arterial blood gas (ABG). ABG is a painful test that requires a skilled health care provider or technician.
How Accurate Is a Pulse Oximeter?
A pulse oximeter uses a light source that shines through your fingertip. By measuring the amount of light that passes through your fingertip, the device can estimate how much oxygen is being carried by your red blood cells. This procedure has become such a common part of physical exams that it has been called a fifth vital sign, along with temperature, pulse, respiratory rate, and blood pressure.
Pulse oximeters that are used in a doctor’s office or health care facility are regulated and tested by the FDA. This type of pulse oximeter can also be prescribed by a doctor for home use. An example would be a patient who has lung disease and needs to check oxygen levels frequently. To be approved by the FDA, these devices are checked against oxygen saturation measured by an ABG. They must be accurate to within two to three percent of an ABG.
Pulse oximeters are also available for home use without a prescription, but these are not regulated by the FDA. Smart phone apps for pulse oximetry are a recent addition. These devices are not intended for medical evaluation. They are intended for general wellness or as a way for athletes or pilots to check their oxygen level.
During the recent COVID-19 epidemic, many people purchased over-the-counter pulse oximeters to check their oxygen saturation because it became commonly known that a low oxygen saturation could be a sign of a COVID infection. The FDA became alarmed about the use of OTC devices and issued a safety communication to doctors and consumers. The FDA warned that OTC pulse oximeters might not be accurate, especially in certain people. These devices might not be accurate in people with dark skin, cold skin, thick skin, or poor circulation. They might also be affected by nail polish, dirty nails, or artificial fingernails.
Do You Need a Pulse Oximeter Reading Chart?
Although you will find pulse oximeter charts on the internet, you really don’t need a chart. Pulse oximeters are easy to read. They give you your pulse and oxygen saturation right on the device. You just have to remember a few numbers. A normal oxygen saturation is 95 to 100 percent. If your oxygen saturation drops below 92 percent, you should contact your health care provider. If it falls below 88, you should get immediate medical attention.
Remember that pulse oximetry is only an estimate of oxygen saturation. A health care provider will look for other signs and symptoms of low oxygen saturation based on pulse oximetry and may do an ABG. Low oxygen saturation may occur in these conditions:
- COVID or other infections of the lungs, like pneumonia
- A blood clot that travels to the lung
- After surgical anesthesia
- With some medications that suppress breathing (like opioid drugs)
- Long term lung conditions like COPD, asthma, or lung cancer
- Heart disease
- Sleep apnea
How to Use a Pulse Oximeter at Home
Unless you have a condition that requires you to keep track of your oxygen saturation, you don’t need a home pulse oximeter. If you want to try one of these devices, keep in mind that OTC devices are not always reliable. When using an OTC device, it is also important to know the signs and symptoms of low oxygen saturation, which may include:
- A blue tint to the lips, face, or fingernails, called cyanosis
- Difficulty breathing or shortness of breath on exertion
- An unexplained and persistent cough
- Cheat pain or tightness
- A racing pulse
If you use one of these devices, follow the directions that come with the device. Before you put it on your finger and remove any nail polish or artificial nails. Make sure your hand is warm, relaxed, and positioned below the level of your heart. Be still until the reading shows up on the device. If you are in good health, it is unlikely that you will have any drop on oxygen saturation without other signs or symptoms. Pay more attention to trends over time than a single reading. If in doubt, contact your health care provider.
While at-home pulse oximeters are not regulated by the FDA, they are a convenience for when you need to regularly check your oxygen saturation.
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