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How A Small Device Called A Pulse Oximeter Measures Blood Oxygen Levels

December 19, 2022

A pulse oximeter is a small device that can measure the oxygen saturation in your blood.

Pulse oximetry is useful for people with chronic lung or heart conditions, who need to monitor how well oxygen is being sent from the heart and lungs out to the furthest parts of the body.

To use a pulse oximeter, you'll clip the device on your toe, finger, or earlobe — here's to use it properly so you can get an accurate reading.

A pulse oximeter is a small device that typically clips on to your finger, toe, or earlobe to measure oxygen levels in the blood.


Pulse oximetry is a quick and easy way to determine how well oxygen is being sent from the heart and lungs out to the furthest parts of the body, which can help determine if your heart and lungs are functioning properly.


Pulse oximeters can be used to gauge warning signs for chronic lung or heart conditions, and may help determine whether you should seek medical attention for the coronavirus.


Here's what you need to know about what exactly a pulse oximeter measures, how it works, and how you can use it properly.


What does a pulse oximeter measure?

A pulse oximeter measures the oxygen saturation of your blood. Essentially, this percentage is a calculation of how much oxygen is in the blood, with 100% being 'fully saturated' and the optimal level.


And while this simple non-invasive medical tool is available over the counter in many pharmacies, it's not necessary for most people.



Those with lung or heart conditions — such as chronic obstructive pulmonary disease (COPD) or heart failure — may be prescribed home oxygen therapy by their doctor, says Rizzo, and a pulse oximeter can help them to monitor whether the use of oxygen at home is improving their condition or not.


Pulse oximeters have also been used to indicate severe cases of COVID-19. That's because the coronavirus can cause a decrease in blood oxygen levels — though if this occurs, it's likely that you'll recognize other symptoms before needing to use a pulse oximeter.


In fact, Rizzo says that oxygen saturation by itself is often not the best indicator of medical conditions, and other symptoms are just as important to tell your doctor.


Other warning signs of low blood oxygen levels may include:


Increased heart rate

increased breathing rate

Feeling shortness of breath or gasping for air

Inability to do an activity that you did before without getting out of breath


How to read a pulse oximeter

According to WHO, a reading of 95% to 100% on the pulse oximeter is considered healthy and isn't a cause for concern.


If you have no underlying medical conditions, your levels should generally be at 95 or higher. But for people with chronic conditions, it's important to talk with your doctor about what the appropriate reading should be for you, and when you should seek medical attention.


For reference, lower levels of blood oxygen saturation may indicate:


Blocked airways

Difficulty breathing

Lung infection

Poor blood circulation

Drug interference from anesthesia, muscle relaxants, or anaphylaxis

In addition, if your pulse oximeter reading drops during exercise, Rizzo says it can be a sign of an underlying lung or heart condition and you should speak with your doctor.