How Does A Pulse Oximeter Work?

Checking the oxygen levels of your blood can now be done at home. In this article, find out how a Pulse Oximeter works and why a dedicated electronic device should be preferred to a smartwatch.

pulse oximeter

Pulse Oximetry is a way to measure the oxygen levels in your blood. Initially used in hospitals, the technology has evolved to the point that you can do this at home! So, how does it work? Are the smartwatches as good as the full-sized home units?

Oximeters work by clipping them onto your finger, where pulses of light are sent through. The absorption of red (660 nm) and infra-red (940 nm) lights is directly linked to the blood oxygenation levels.

Watch Oximeters, while impressive, are not always as accurate as a dedicated unit. Today we will discuss Pulse Oximeters in a little more detail, citing practical uses in the home, how they work won a more granular level, and why smartwatches may not be the best choice for your primary Oximeter.  

Not just for doctors anymore – A Pulse Oximeter’s uses in the home

Formerly only used by highly-trained medical professionals, Pulse Oximeters were deemed useful enough to become automated and easy to use.

They provide valuable information on the amount of oxygen carried by the red blood cells quickly and non-invasively. In the current COVID-19 pandemics, oximeters are an easy way to check on silent hypoxia at the early stages of the disease.


Home uses of your Pulse Oximeter include:

  • Assessing COVID-19 recovery through blood oxygenation readings
  • Monitor your child’s breathing to minimize the chances of Sudden infant death syndrome (SIDS). The Wellue BabyO2 monitor is a top-of-the-line example of this.
  • Determining the effects of increased physical activity in the elderly or patients with lung or heart diseases
  • Identifying the presence of Sleep Apnea and similar conditions which affect nighttime breathing
  • Determining the efficacy of new medications for lung disease
  • Checking oxygen to determine sensitivity to high-altitude travel and to explain shortness of breath

As you can see, using this technology is a great advantage for keeping on top of your health. So, how does it all work? Let’s take a more in-depth look at Pulse Oximeter technology in this modern age.

How Pulse Oximeters work

While we briefly touched the subject, let’s delve a little deeper into Pulse Oximeter function. If you are giving yourself a Pulse Oximeter reading, it will go something like this. First, a small clamp is placed on the finger, a toe, or even your earlobe.

Next, pulses of light are flashed through the attachment and depending on how the light is absorbed the unit can determine your blood oxygen level, without resorting to needles. This produces a reading typically listed as O2sat or SaO2. Healthy blood will typically be at an 99% level of Oxygenation and if it’s not, then this is something that you need to know.

If the reading is correct, then you may require medication to facilitate easier breathing or possibly supplemental oxygen. If it is the latter, then your Pulse Oximeter reading will help determine how much is required, and if the former, then your Oximeter can help determine if the prescribed treatment is effective.

Good to know that the fingernail polish color will not impact the readings. Somehow, recent studies showed that artificial nails such as gel-based ones can overestimate the measurements and should be removed before using the device.

Is a smartwatch Oximeter as good as a full-sized one?

Fitness trackers such as Fitbit, Huawei’s GT2, and Apple’s 6 series watches are the latest craze these days, and they have a lot of interesting features. Predominantly used in heart rate monitoring, these devices can sometimes even post values online to keep track of your health regimen and make recommendations (or let your significant other knows that you are skipping exercise!).

These are exciting features, and lately, Pulse Oximetry has been thrown into the mix. We can’t recommend them against home units at this point, unfortunately. The biggest problem is that you are generally not going to get the kind of accuracy you’d want to bet your health on.

The most significant way to tell is by reading the disclaimers. If you are considering a smartwatch as your primary Oximeter, then be sure to give the fine print a review. Manufacturers of these products know how accurate or how ‘ballpark figure’ the readings will be. So, if you see a disclaimer stating that you should not rely on these readings for medical conditions, then you have your answer right there in front of you.

Can you get useful information from them? Certainly. The technology is growing in leaps and bounds, but when it comes to checking your blood’s oxygen levels for something vitally serious, we suggest choosing an FDA-approved device.

A full-sized Pulse Oximeter performs one function, and that’s all that you need. After all, when you need a screwdriver, do you reach for a multi-tool from the toolbox?

Of course not. The right tool for the right job is the way to go. Until the technology has been clinically validated, the prudent choice will be the full-sized Pulse Oximeter. Smartwatches can’t provide the type of granular reading that is NEEDED.

How do Pulse Oximeters compare with ABG readings?

When you hear someone telling you that you need to go to the doctor to get a reading, instead of utilizing your handy Pulse Oximeter, what they are usually talking about is an Arterial Blood Gas (ABG) reading.

An ABG is a more invasive means of reading the oxygen levels in your blood. It differs from a Pulse Oximeter because an ABG is a direct reading of your blood’s oxygen levels, while a Pulse Oximeter is an indirect one. This makes ABG readings the most accurate, but they are also the most invasive, involving blood draw to obtain a hospital lab sample.

Pulse oximeter measurements are highly accurate, and unless a doctor tells you otherwise, it will be the best way to go. You can get the accurate SaO2 reading that you need to stay on top of your health without poking yourself to do it, and it’s nothing short of amazing.

Some final words on Pulse Oximeters

As you can see, while Pulse Oximeters come in a few different flavors, based on how the technology works, a dedicated home unit is going to be your best choice. Whether you are safeguarding your own or your child’s sleep and breathing, keeping abreast of oxygen saturation levels during the pandemic, or assessing lung function improvements when taking medication – A Pulse Oximeter makes perfect sense.

As they say, ‘prepare and prevent’ is always better than to ‘repair and repent’. Be smart, be safe, and thanks for reading!

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