What is a Pulse Oximeter and How Does it Work?
The pulse oximeter has almost become a household name. It rose to the limelight back in 2020 during the peak of the COVID-19 pandemic.
People were buying them for at-home monitoring to keep an eye on their oxygen levels because sometimes, low oxygen saturation was the only symptom of a serious infection.
They're everywhere now, from your doctor’s office to your local pharmacy or even on Amazon. If you’ve yet to come across it, it’s a little device that clips onto your finger at the doctor’s office or maybe even in your own home. While it might seem pretty basic, it’s doing a lot more than you might think.
Pulse Oximeter: What Exactly Does it Do?
The primary job of a pulse oximeter is to measure how well oxygen is being delivered to the parts of your body that need it most: your organs, muscles, and tissues. Your body relies on oxygen to function, and without enough of it, things can go downhill pretty quickly.
A pulse oximeter measures your oxygen saturation level. This is essentially the percentage of oxygen-carrying haemoglobin in your blood. Haemoglobin is the protein in your red blood cells responsible for transporting oxygen throughout your body. When you see your SpO2 reading, it tells you how much of your blood is loaded with oxygen.
The other thing the pulse oximeter measures is your pulse rate. Your heart pumps blood in waves, and as it does, it creates tiny changes in the amount of blood in your finger (or wherever you have the device attached).
The oximeter detects those changes and turns them into a number that represents your heartbeats per minute.
How Exactly Does a Pulse Oximeter Work?
The pulse oximeter uses light, specifically, red and infrared light. When you slide your finger into the device, it shines these lights through your skin. The sensor on the other side of the clip then measures how much of each type of light is absorbed by your blood.
Oxygenated blood absorbs more infrared light, while deoxygenated blood absorbs more red light. Based on these absorption levels, the device calculates your oxygen saturation level.
The device measures the difference between the two types of absorption. For you, this means that the pulse oximeter is constantly checking to see how many of your red blood cells are fully loaded with oxygen.
If the majority are oxygen-rich, it gives a reading closer to 100%. If more are oxygen-poor, the number drops, and that’s when you or your doctor might need to take action.
When you clip that little device onto your finger (or sometimes your toe or earlobe), within seconds, it gives you two numbers: your SpO2 and your pulse rate. It’s fast, it’s painless, and it’s surprisingly accurate.
It’s usually your finger or earlobe they use for this, primarily because these areas have tons of blood flow and are thin enough for light to pass through easily. The fingertip, especially, has a perfect balance of those traits, making it ideal for accurate readings.
Pulse oximeters used in hospitals and medical settings typically have an accuracy rate of 95% to 98%. And for most home-use models, accuracy falls within 2% to 3% of a clinical measurement. That’s pretty impressive when you consider how quickly and non-invasively they work.
But it’s not a perfect tool. There are a few factors that can affect the accuracy. For example, cold fingers can reduce blood flow, making it harder for the device to get a good reading.
Nail polish, especially dark colours, can interfere with the light sensors. And if you’re moving around too much, the readings can become less reliable.
Why Should You Care About Oxygen Saturation?
You’re probably wondering why your SpO2 matters so much. It’s simple. Your body runs on oxygen. Every part of you needs it, and when your levels dip below a certain point, you can start experiencing symptoms like shortness of breath, dizziness, or even more serious complications like organ damage.
Normally, healthy oxygen saturation levels should sit between 95% and 100%. Anything below 90% is considered low and could indicate a condition called hypoxemia, which means your body isn’t getting the oxygen it needs.
The thing is, you might not always feel different if your oxygen levels drop, which is why a pulse oximeter is so handy. It can detect low oxygen levels before you even realise there’s a problem.
This is particularly important for people with conditions like chronic obstructive pulmonary disease (COPD), asthma, or even COVID-19, where oxygen levels can drop suddenly without you noticing.
Who Needs a Pulse Oximeter?
Pulse oximeters are essential for anyone dealing with respiratory or cardiac issues, but their use isn’t limited to people with medical conditions. Athletes, for example, often use them during training to make sure their bodies are getting enough oxygen during intense workouts.
If you’ve ever had surgery, your doctor probably monitored your oxygen levels closely afterwards. That’s because anaesthesia can affect your breathing, and low oxygen levels during recovery can lead to complications.
And let's not forget about newborn babies. In many hospitals, pulse oximeters are used to check for congenital heart defects right after birth.
What’s the Difference Between a Medical-Grade Pulse Oximeter and a Consumer One?
When you’re choosing a pulse oximeter, you might think they’re all the same. After all, they all give you a number that tells you your oxygen levels, right? Well, not quite.
One of the biggest differences between a medical-grade pulse oximeter and a consumer one is accuracy. They’re required to meet strict guidelines set by organisations like the Therapeutic Goods Administration (TGA).
These guidelines ensure that the devices are accurate within a very small margin of error, usually within 2% of your actual oxygen saturation levels. So, if your true oxygen saturation is 95%, a medical-grade device will give you a reading somewhere between 93% and 97%.
On the other hand, consumer-grade pulse oximeters often don’t need to meet these same stringent standards. While they might still give you a ballpark figure, they could be off by a much larger margin, sometimes up to 5% or more. A reading of 90% on a consumer-grade oximeter could actually be much lower, dangerously low, and you wouldn't even know it.
Conclusion
At the end of the day, the pulse oximeter might seem like a simple device, but it’s more powerful than it appears. It’s a small device, but it could make a big difference in your health, especially when you know how to use it and what those numbers really mean for you.