What Are The Main Difference Between SpO2 Vs SaO2?

Blood oxygen saturation level varies according to the medium of blood(Vein, tissue, artery). SpO2 and Sao2 are exactly the same factors in Blood saturation level tracking.

The main difference- Both SpO2 and SaO2 measure Arterial Blood Oxygen Saturation level but SpO2 refers to Peripheral Blood OxygenSaturation Level. Where SaO2 refers to Arterial Blood Oxygen Saturation detection. Both have different clinical importance.

On this page, we are going to discuss the parameters that distinguish both Blood Oxygen Saturation monitoring.

Difference Between SpO2 VS SaO2

SaO2 is Arterial Blood Oxygen Saturation. SpO2 is Peripheral Blood Oxygen Saturation. 
It measures functional and non-functional hemoglobin. It measures only functional hemoglobin.  
SaO2 is measured by Invasive Oximetry. SpO2 is measured by Non-invasive Oximetry. 
It can not be easily checked at home. SpO2 can be easily checked at home. 
It requires professional skill to Run the SaO2 test. Anyone can check SpO2 at home. 
The blood Gas analyzer checks SaO2. Pulse OX, Smartwatches check SpO2. 

Blood Oxygen Saturation Area

As the name state, the detection area of SpO2 is in the Peripheral arteries. But Arterial Blood gives the SaO2 results.

Hemoglobin Type

In SpO2 monitoring, only functional hemoglobin is taken as a factor of measurement. Where SaO2 takes both functional and Non-functional hemoglobin.


The measurements of SpO2 are operated by non-invasive methods. Pulse OX or SpO2 smartwatches is capable to detect Peripheral blood oxygen saturation.

Blood Gas Analyzer machine measures SaO2, pH level, and other gas presence in Arterial Blood.

Clinical Situation

SpO2: Peripheral blood oxygen saturation level describes several physical treatments such as surgery unit care, hypoxemia, and COPD(Chronic obstructive pulmonary disease) patient care. This quality of oxygen presence maintains the heart, kidney, and brain health.

SaO2: The Arterial blood oxygen level emphasizes the presence of oxygen that improves the level of metabolism and Respiratory function. Poor distribution of Oxygen in arteries may harm the heart as well as brain function.

Less than 60% of SaO2 causes Hypoxemia. The symptoms are seen in the skin, nails, and toe becoming blueish which is called Cyanosis.

What Is SpO2?

The word SpO2 refers to Peripheral Oxygen Saturation Level. It is a comparison of the amount of Oxygenated and total hemoglobin (Oxy-hemoglobin & Deoxy-hemoglobin) in your Blood. SpO2 level is represented in percentage.

Now, you might be bothered about the Normal Range of Blood Oxygen Saturation.

A good SpO2 is between 95%-99% in healthy lungs. With lung disease, the normal Oxygen Saturation level will differ and can be told by professional clinicians.

What is SpO2

If the candidate is having less than 94% to 90% for a long period of time, he or she might be given an external oxygen supply.

Check 3 types of Oxygen delivery methods.

In various kinds of clinical situations such as post-anesthetic care, emergency unit, and surgery; SpO2 measurement becomes a crucial clinical process.

How To Check SpO2?

To check Peripheral Oxygen saturation levels, we can use a doctor-recommended device called Pulse Oximeter. The reason why we recommending to use a Pulse OX is the high usability of measuring SpO2 at home.

Blood Oxygen Saturation level tracking using SpO2 is a non-invasive way to check the SpO2 level.

Checking SpO2 Using Pulse OX

A Pulse OX is a clip-like device that can be attached to any thin skin such as a finger, earlobe, or toe for infants. Then the device will use Red and Infrared lights to measure oxygenated Hemoglobin in your Blood.

The amount of Oxygenated Hemoglobin is compared to the total amount of Hemoglobin in blood in percentage will the SpO2 level.

To know more check how to use Oximeter for checking the SpO2 level.

On the other hand, you can use a Smartwatch to check SpO2. A smartwatch can give an overall measurement using Reflectance Oximetry. You can check the data on the smartwatch display instantly.

For more information, you must check the SpO2 levels in the fitness tracking App.

Best Devices To Check SpO2

Zacurate Pro Pulse OX

With 12 Months of warranty, Zacurate Pro series 500DL offers 2X AAA batteries and a silicone cover to protect the oximeter screen from dust and dirt. This device is capable to measure pulse rate, pulse strength, and SpO2 level within just 10 seconds. In addition, the brand states that this is the only LED Pulse Oximeter with that displays up to 100% SpO2 level.

It has a smart spring system and a finger chamber for ages 12 to above.

If you are going to the hills and mountains for climbing, skiing, or biking this pulse OX will not disappoint you. You can take advantage of this device to check Oxygen saturation levels in high altitudes.

Key Benefits
  • Large LED Screen
  • Reading Shows Upto 100%
  • Accurate And Quick Calculation
  • Wide Finger Varieties

FaceLake ® FL400 Pulse Oximeter

With 2 AAA batteries, users can get this device within an affordable budget. The device takes 24 seconds to calculate the whole data with Spo2 and Pulse rate. You have multiple benefits such as a heart rate bar graph, Lanyard Loophole, comfortable finger operating chamber, low battery indicator, Blood oxygen saturation level, and average heart rate.

To operate the device you just need 1 button. In addition, the package includes Nylon carrying case, Facelake Neck Lanyard, 1-year full warranty.

Key Benefits
  • Hypoallergenic Medical Grade Silicone Finger Chamber
  • 1 Button Control
  • Quick Result
  • Easy Display Interface

Garmin Forerunner 245

Bluetooth, smartphone integration, advanced dynamics, and quality music control. GPS technology makes it useful for athletes like runners, climbers, or bikers.

There are numerous advanced sports modes to make your day successful with custom workouts on Garmin connect fitness community. Blood Oxygen saturation level detection, heart rate, sleep, safety, and tracking features will support every step during working hours.

At last, we have to raise the point of 7 days of battery life, 6 hours GPS mode, and highly durable Corning Gorilla Glass.

Key Benefits
  • GPS Tracking
  • SpO2 monitoring
  • Good Battery Life
  • Custom workout training

What Is SaO2?

In medical, the word saturation is also used as Sat. Hence, the SaO2 stats to the Arterial Blood Oxygen Saturation Level. It is represented in the percentage of binding sites along with Hemoglobin, bound with Oxygen in the arterial blood.

We must include that here we are not talking about venous blood. In SaO2, we talk about Arteris which carry oxygenated hemoglobin. The percentage of SaO2 may differ based on body temperature, pH level, and Partial Pressure of Carbon di-Oxide(PaCO2).

SaO2 definition and Calculation

Now, let’s talk about how you can practically check the SaO2.

How To Check SaO2?

Look, as mentioned earlier, SaO2 measurement is done from the arterial Blood Oxygen presence. Therefore, a non-invasive way of measuring blood Oxygen level tracking could not perform this test. To check SaO2 we run a test called BGT: Blood Gas Test or Blood Gas Saturation Test.

This is a complete clinical process where you need to give a few drops of blood. This blood will send to the Blood Gas Analyzer to check the SaO2 level.

Low SpO2 levels affect a cardiac or respiratory arrest. Interruption in heart and brain function is found due to low oxygen saturation in Hemoglobin.

Lack of oxygen in the blood causes a disease called hypoxemia. For instance, people with low oxygen saturation level causes tissue damage that is also considered Hypoxia.

Check Hypoxemia symptoms and treatments.

There are some critical symptoms that happen due to lack of oxygen absorption in the blood such as Cyanosis. Here we can see a blueish discoloration of the skin due to inadequate amount of oxygen circulation.

Click here to check how a smartwatch detects sleep.

Best Devices To Check SaO2

A blood Gas Analyzer is an electrical device used for Blood Gas Tests. It is a piece of medical equipment that is not preferred by patients themselves.

To check SaO2 in the device, we need to take liquid blood as a sample for the test. Thereafter the blood is sent to device mechanism that can be operated by professionals.

Radiometer is one of the mentionable Blood Gas Analyzer systems manufacturers. Epoc, Rapid are the two most recommended devices for blood gas testings by Simens-Healthineers.

Till now, we are talking about the difference between SpO2 and SaO2. It’s time to take a look at the similarities.

Some Common Factors Between SpO2 And SaO2

In the discussion of SpO2 as well as SaO2, we can figure out some similarities. Let’s talk about it.

  1. Both describe the amount of Oxygenated Hemoglobin in the arterial blood
  2. The number of Spo2 and SaO2 describe some health conditions like surgical procedures, Anemic conditions, Lung disease, Hypoxemia
  3. Both methods describe the Oxygen saturation level
  4. In both tests, Hemoglobin plays a vital role
  5. Percentage(%) is the limit of both SpO2 & Sao2

Thanks for reading guys. It’s important to mention that I am not a professional doctor. Therefore this article is totally for educational purposes. But I have tried my best to describe the complex topics.

Feel free to share it.