SpO2: What is it? Measurement Benefits, Limitations, Effects of Low Oxygen Saturation and Indications

Hemoglobin is the protein that carries oxygen in the blood.

By definition, peripheral oxygen saturation (Spo2) is a measure of peripheral capillary oxygen saturation.

This measurement is an estimate of the amount of oxygen in our blood expressed as a percentage of the amount of hemoglobin oxygenated to total hemoglobin.

Most people have heard of hemoglobin in relation to the blood disorder, anemia. Peripheral oxygen saturation (SpO2) measurements are used to estimate arterial blood saturation (SaO2).

However, the validity of the relationship between peripheral oxygen saturation (SpO2) and arterial blood saturation (SaO2) depends on a number of factors, including the adequacy of peripheral perfusion.

Given recent data questioning the reproducibility of the saturation level (measured by peripheral oxygen saturation) at short time intervals in patients with idiopathic pulmonary fibrosis (IPF).

What is a normal peripheral oxygen saturation level (Spo2)?

Peripheral oxygen saturation (Spo2) represents peripheral capillary oxygen saturation, an estimate of the amount of oxygen in the blood.

More specifically, it is the percentage of oxygenated hemoglobin (oxygen-containing hemoglobin) compared to the total amount of hemoglobin in the blood (oxygenated and non-oxygenated hemoglobin).

Peripheral oxygen saturation (Spo2) is an estimate of arterial oxygen saturation or SaO2, which refers to the amount of oxygenated hemoglobin in the blood.

Hemoglobin is a protein that carries oxygen in the blood. It is found inside red blood cells and gives them their red color.

Peripheral oxygen saturation (Spo2) can be measured using pulse oximetry, an indirect, non-invasive method (meaning it does not involve the introduction of instruments into the body).

It works by emitting and then absorbing a wave of light that passes through the blood vessels (or capillaries) at the fingertip.

A variation in the light wave passing through the finger will give the value of the peripheral oxygen saturation (Spo2) measurement because the degree of oxygen saturation causes variations in the color of the blood.

Pulse oximetry is usually a fairly accurate test. This is especially true when using high-quality equipment found in most doctor’s offices or hospital settings.

This value is represented by a percentage and always provides results within a 2 percent difference both ways of what it actually is.

If your reading was 82 percent, for example, your true oxygen saturation level may be 80 to 84 percent. However, the quality of the waveform and the assessment of the person must be considered.

Factors such as movement, temperature, or nail polish can affect accuracy.

Normally, more than 89 percent of your blood must carry oxygen. This is the level of oxygen saturation necessary to keep your cells and your body healthy.

If your percentage says 98%, this means that each red blood cell is made up of 98% oxygenated and 2% non-oxygenated hemoglobin. The normal values ​​of peripheral oxygen saturation (Spo2) vary between 95 and 100%.

While oxygen saturation below this temperature is not believed to temporarily cause harm, repeated or consistent instances of low oxygen saturation levels can be detrimental.

Good oxygenation of the blood is necessary to supply the energy your muscles need to function, which is increased during a sporting activity.

If your peripheral oxygen saturation (Spo2) value is below 95%, that could be a sign of poor blood oxygenation, also called hypoxia.

When is SpO2 Measurement Beneficial?

It seems that every week a new technology is released that allows people to access more data related to their physical condition.

From watches that track your movement based on satellite positioning to cell phones that can read a person’s heart rate with the touch of a finger, there is no information that has not been rotated.

Finding a fitness tracker is not the problem, sometimes the difficult thing is to determine which readings are beneficial and which are not.

Helping reduce biometrics that is conducive to your specific fitness goals can save you not only money, but also the headache of figuring out your tracker’s features.

One of the most promising fitness tracking devices is pulse oximeters. This relatively new fitness tracker for the health / fitness industry.


Pulse oximetry is particularly suitable for non-invasive continuous measurement of oxygen saturation in the blood. Rather, blood gas levels must be determined in a laboratory with a sample of blood drawn.

Pulse oximetry is useful in any environment where a patient’s oxygenation is unstable, including intensive care, operations, recovery, emergency and hospitalization settings, pilots in non-pressurized aircraft, for the assessment of oxygenation of any patient and for determine the effectiveness or need for supplemental oxygen.


To quantify hemoglobin, the device uses additional wavelengths of light beyond the two standard ones.

Since pulse oximetry measures only the percentage of bound hemoglobin, a falsely high or falsely low reading will occur when hemoglobin binds to something other than oxygen:

Hemoglobin has a higher affinity for carbon monoxide than oxygen, and a high reading can occur even though the patient is truly hypoxemic.

Effects of low oxygen saturation

When your body’s oxygen saturation percentage drops below 95%, you will begin to experience the effects of hypoxemia .

Hypoxemia means that there is a low amount of oxygen in the blood; This leads to hypoxia or low oxygen level in the tissues.

These conditions can lead a person to have shortness of breath, headaches, fainting, and even confusion.

How is SpO2 measured?

Pulse oximetry is used to measure the oxygen saturation of the blood. This measurement technique is a non-invasive calculation of peripheral oxygen saturation.

This technique also provides a measure of the individual’s cardiorespiratory function. Pulse oximetry used to be used only in clinical practice for patients.

Now biometric tracking devices are using it with a target audience from the fitness and athletic performance populations. Pulse oximeters are useful in the hospital setting.

During a pulse oximetry reading, a small clamp-shaped device is placed on a finger, earlobe, or toe. Small rays of light pass through the blood on the finger, measuring the amount of oxygen.

It does this by measuring changes in light absorption in oxygenated or deoxygenated blood. This is a painless process.

The pulse oximeter will be able to tell you your oxygen saturation levels along with your heart rate.

Steps of the procedure

Pulse oximetry can be used in both outpatient and outpatient settings. In some cases, your doctor may recommend that you have a pulse oximeter for use at home. The pulse oximetry process is as follows:

Most commonly, a clip-like device will be placed on your finger, earlobe, or toe. You may feel a small amount of pressure, but there is no pain or pinching. In some cases, a small probe can be placed on your finger or forehead with a sticky adhesive.

You may be asked to remove nail polish if it is attached to a finger. You will keep the probe on for as long as necessary to monitor your pulse and oxygen saturation.

When monitoring physical activity capabilities, this will be during the length of exercise and during the recovery period. During surgery, the tube will be attached beforehand and removed once you are awake and no longer under supervision.

Sometimes it will only be used to take a single reading very quickly. After the test is complete, the clip or probe will be removed.

After the test is complete, your care provider will have the readings available immediately. This will help them determine if other tests or treatments are needed.

If you are evaluating how successful your oxygen supplementation therapy is, for example, a reading that is still on the low side could indicate a need for more oxygen.

Your healthcare provider will be able to tell you what the next steps are. If you are using pulse oximetry at home, they will inform you how often to take your readings and what to do if they exceed or fall below certain levels.

Pulse Oximetry Measurement Applications in Fitness

While pulse oximetry may not have many applications in the general physical population, it may have useful application in sport-specific situations.

These types of situations include when people exercise at levels that are below, above or above their maximum amount of oxygen (VO2 max).

Peripheral oxygen saturation (Spo2) measurement can be beneficial during these specific exercises to show athletes and their coaches the specific work rate an athlete can maintain before their bodies begin to require more oxygen than is produced .

When individuals can look back at their data after a workout, they will be able to see their oxygen saturation percentage trend lines fall.

When the oxygen percentage begins to trend downward, this means that you are working above the limit of your body.

How can it be applicable?

By knowing your body’s limits, you can tailor your workouts to increase your body’s maximum amount of oxygen by “pushing” your own limits.

For example, a cyclist could ride in multiple two-minute intervals increasing their power until they reach a point where oxygen saturation begins to decrease.

This app does not only apply to solo cyclists, but to many different disciplines of sport in general that require an athlete to reach high and sustainable limits over a certain period of time; runners, cross-country skiing, and swimmers are some examples.

Another application for the use of pulse oximetry can be in high altitude events. People involved in high altitude climbing can use peripheral oxygen saturation (Spo2) biometrics to help track their body’s limits and oxygen levels.

A climber can use this measure to help them moderate their effort levels during an ascent.

If you saw that during a certain part of your effort, that is, with increasing altitude, the percentage of oxygen is decreasing; they could determine if that specific workload was in a sustainable range.

If their oxygen saturation levels drop, this can help them re-evaluate their effort. It may mean slowing down your ascent rate or continuing the ascent may not be in your best interest for your body’s health.

Data is constantly evolving in the fitness industry and the ability to produce marginal improvements is constantly being tested.

The fairly new market for pulse oximeters for collecting fitness data is just one of many new products to be introduced.

There are specific clinical and sports applications where the information is beneficial. Determining if you are part of this population of individuals can help you determine if you need to invest in measuring your oxygen saturation.

Pulse oximetry

Pulse oximetry is a non-invasive method to measure the oxygen saturation in a person’s blood, which is often referred to as SpO2 or “The Fifth Vital Sign” (the first 4 are your pulse, temperature, blood pressure and Breathing frequency).

It is a method of monitoring the oxygen saturation (SO2) of a person.

Although your peripheral oxygen saturation (SpO2) reading is not always identical to the more desirable arterial oxygen saturation (SaO2) reading from the arterial blood gas analysis, the two are correlated well enough for the safe method, convenient, non-invasive and inexpensive pulse oximetry.

Why do doctors use it?

Pulse oximetry is a method that doctors use to quickly assess and monitor a patient’s respiratory function.

It is also used to determine which patients may suffer from hypoxia and should have additional tests.

Self-monitoring of your blood oxygen level

Until recently, doctors were the only ones using pulse oximeters, usually in a clinical setting.

But as these tools are now more common (understand that they are smaller and cheaper), automatic monitoring of peripheral oxygen saturation (Spo2) has become a reality.

In fact, everyone can benefit from tracking their peripheral oxygen saturation (Spo2).

Being a healthy young man or woman does not mean that you will not benefit from preventive follow-up for respiratory problems.

Since monitoring your blood oxygenation can give you an early warning signal (plus, you’ll have a history of measurements to show your doctor, which they are likely to welcome).

If you are a mountaineer or athlete who is training at high altitudes to increase your endurance, measuring your blood oxygen saturation is very important as it can reveal life-threatening hypoxic conditions.

This easy-to-use method is also great for people affected by a wide variety of chronic conditions, such as asthma and chronic obstructive pulmonary disease (COPD), as it helps them quickly assess the severity of their condition.

When should I measure my SpO2?

You can measure your blood oxygen level at rest, during, or after physical activities.

Pulse oximetry is a quick, non-invasive, and completely painless test. There is no risk, apart from possible skin irritation from the adhesive used in some types of probes.

It can quickly detect even small changes in the efficiency of oxygen transport to the extremities farthest from the heart, including the legs and arms.