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The Pros and Cons of Using a Pulse Oximeter
Are you getting enough oxygen when you breathe?

Finger mounted pulse oximeter. Photo by Stefan Bellini.
Finger mounted pulse oximeter.
Photo by Stefan Bellini.

Whenever I go into my doctor's office for a checkup, they put a little clip on my finger. It looks like a thick clothespin or something you would use to secure a bag of chips. Within a few seconds, some numbers pop up.

That device is called a pulse oximeter. It measures heart rate and blood oxygen levels. It works by shining a light on the area being measured and calculating the percentage of oxygen in red blood cells, also known as oxygen saturation.

Red blood cells carry oxygen from your lungs to your organs. A normal range for most healthy people is between 95 and 100 percent. However, medical conditions can lower that number. If you have asthma, anemia, are experiencing an allergic reaction, COPD, emphysema, pneumonia, have sleep apnea or are going through cancer treatments your number can be lower. Smoking and vaping can bring that number down as well.

A low reading can also be an early warning sign you're getting sick. A level of 92 percent indicates a condition known as hypoxemia. That may mean you're not getting enough oxygen to keep your cells and your body healthy. Readings below 90 percent are considered abnormally low and may indicate a clinical emergency.

Consistently low readings indicate your body is working harder than it should, and in extreme cases can cause permanent damage to organs. If a medical professional documents regular readings below 88%, medicare will pay for oxygen therapy and oxygen equipment.

In the last few years, the price of pulse oximeters has dropped so significantly, you can now pick up a reasonably reliable one for around $30. That means you can track your oxygen levels at home, whenever you want.

There are some benefits to home monitoring.

People who aren't sleeping well could wear one overnight. A drop or multiple drops in oxygen levels could indicate sleep apnea or severe snoring.

Anyone taking drugs that affects breathing can use one to learn if there's a problem. Regular monitoring can also alert people to chronic respiratory or cardiovascular conditions. Then doctors can decide if supplemental oxygen is necessary.

Do masks prevent you from getting enough oxygen?

I decided to get one to answer a question many of my clients have. Since wearing a mask is currently required while training, I wanted to make sure everyone was getting enough oxygen during their workout.

I started with my trainers. I asked them to take their reading before and after an intense cardio session. We used different thicknesses and types of masks, including one session with a fitted N95 respirator. The results surprised me.

With 10 different sessions, the average drop in oxygen levels was less than 1%. In two people, the oxygen levels increased in the final reading. Keep in mind that the accuracy of these devices can vary by 2%. So in practical terms, there was no statistical change after 30 minutes of intense cardio, even though they were breathing through a mask.

The results I obtained, cannot be used as a benchmark for everyone. The testing wasn't done under rigorous clinical conditions, we had no control group and the sample size was too small. The value was the information provided to those involved in the test. After going over results with a doctor, they felt reassured their mask wearing workouts weren't hurting them.

Anyone that's concerned about oxygen deprivation from wearing a mask, should definitely consider testing themselves with a pulse oximeter. If for no other reason than to put your mind at ease.

If you're considering monitoring yourself, you need to be aware of several issues.

If your fingernails are too long, your fingers may not fit properly in the machine and you'll get a bad result. Dark nail polish and dirty fingers can also cause inaccurate readings. Testing on someone with darker skin can over-estimate the reading if the actual number is below 80%. Test where skin color is lightest.

Medical issues can create false readings. High levels of carbon monoxide can throw the readings off. People suffering from smoke inhalation, heavy cigarette smokers and someone with carbon monoxide poisoning shouldn't use a pulse oximeter.

Someone suffering from anemia or anyone with blood volume deficiencies like hypovolemia, hypotension and hypothermia may not get accurate readings. High levels of methemoglobin, a form of hemoglobin that does not carry oxygen can also cause problems.

Testing on anyone with cold hands or in a cold environment can be challenging. The same is true if you're testing around particularly bright lights. Since a pulse oximeter uses light to get the reading, really bright lights could interfere.

What fingers to use.

Health technicians typically place the device on the index fingers. One clinical study showed the highest reading came from the third finger on the dominant hand. That means right handed people should use the middle finger on the right hand and left handed people should use the middle finger on the left hand. Whichever finger works best you should continue to use so your results are consistent.

Don't just buy a pulse oximeter and blindly believe the results. If you want to use one, ask your doctor if using one might be beneficial for you. Check to see if you have underlying conditions that would make the results invalid. If your doctor recommends one, ask about the best way to use it in your particular situation.

Martina Bevis wearing pulse oximeter.
Wearing a pulse oximeter after an intense cardio session.

Want to Buy a Pulse Oximeter?

Wirecutter, a New York Times Company that reviews and recommends products, suggests starting with the Food and Drug Administration’s 510(k) Premarket Notification Database and searching for “oximeter.”

(From The New York Times article: What's a Pulse Oximeter, and Do I Really Need One at Home? By Tara Parker-Pope, April 24, 2020.)

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