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How Pulse Oximeter Works? Advantages And Uses Of Pulse Oximeter

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What is a pulse oximeter?

How pulse oximeter works?

Pulse oximeter is a device that instantly measures the level of the oxygen (saturation) in your blood. It is a portable clip-like device that is fixed onto your finger, toe, or ear lobe. It measures the amount of oxygen reaching to these body parts that are furthest from your heart. In a matter of seconds, it displays the level of oxygen in your blood and your pulse rate. In this article, we will cover uses and advantages of pulse Oximeter and also know How pulse oximeter works?


Advantages of Pulse Oximeter –

There are the advantages of pulse oximeter and the device doesn’t need any specific medical training and can be used by anyone because of the following advantages.

• Easy to use- fixing the device and reading the results doesn’t need any specific training.

• Instant results- provides quick and real-time results. It can be kept in place to provide continuous monitoring of oxygen saturation. this is one of the main advantage from all advantages of pulse oximeter.

• Portable- small portable device that can be carried anywhere. You may use it at home, in a hospital, or while traveling to someplace.

• Painless procedure- it doesn’t require to prick your skin to take out a sample of blood.

• Require minimal power supply- in the form of small batteries.

How pulse oximeter works?

The pulse oximeter works by measuring the amount of light absorbed by your blood. After the knowledge of advantages of pulse oximeter you would really like to learn how pulse oximeter works?

Once the device is fixed and switched on, it passes flashes of red and infra-red lights across the blood in your finger. The oxygen-rich and oxygen-poor blood absorb the lights differently. The transmitted lights are then collected by the device and calculated to provide the oxygen level.

The oxygen level measured by the device is denoted as SpO2 (peripheral capillary oxygen saturation).

The device also depicts your pulse rate- indicating the number of times your beats in a minute.

Why pulse oximeter is used?

As we have already talked about advantages of pulse oximeter above this is really important to know why you should use pulse oximeter?, the pulse oximeter checks the amount of blood oxygen, reaching to the peripheries of your body. So, the device can be used to detect any condition that reduces the blood oxygen level.

This can occur due to any condition that affects:



Diseases of the lung reducing its capacity to absorb oxygen into the blood.

• Pneumonia- fluid accumulation in air space- seen in infections including COVID-19

• Asthma


• Lung cancer



Diseases reducing the ability of the heart to throw blood to various body parts

• Heart attack

• Heart failure

• Congenital heart defects



Diseases reducing the ability of blood to carry oxygen

• Anemia

Apart from the above diseases, the oximeter is also used for some specific situations. Here, the device monitors the person during a treatment or a procedure.

• To monitor the blood oxygen level when the person is on a ventilator

• To check the response of medicines on lungs

• To monitor a person’s condition during or after surgery

• To check one’s ability to manage increased physical activity

• To perform a sleep study- to detect if someone’s stops breathing momentarily while sleeping

Why pulse oximeter is used in COVID-19?

Well, As you already know about the advantages of pulse oximeter, but you should know why you should use pulse oximeter in covid 19. The virus causing COVID-19 upon entering your lungs causes damage to the cells. This leads to the inflammation (swelling) and pneumonia in the lungs. Both conditions reduce the ability of the lungs to absorb oxygen from inhaled air leading to a fall in blood oxygen level.

The pulse oximeter helps in COVID-19 by detecting the fall in blood oxygen levels.

The level of oxygen saturation (SpO2) in the blood is 95-100% with healthy lungs.

• When the blood oxygen levels fall below 95%, the person typically develops oxygen deficiency (hypoxia).

• When the oxygen level falls further below 85%, then the body develops severe deficiency, which may cause damage to the organs.

The fall in oxygen levels is usually associated with the development of breathlessness, which is an important sign of worsening of the condition in COVID-19. Thus, it warrants hospital admission and medical help.


Silent hypoxia

However, some cases of COVID-19 have shown no development of breathlessness or significant symptoms with the fall in oxygen levels. Some patients were found looking normal even with oxygen levels as low as 50% SpO2. This unusual condition is termed as silent hypoxia or happy hypoxia.

The silent hypoxia seen in COVID-19 can be easily overlooked due to the absence of troubled breathing or other gross symptoms. This makes the oximeter a very useful device to detect early stage of the COVID-19, when the condition is clinically silent.

This use is more important for the people who are

• Home quarantined, or

• People with high risk such as lung disease, heart disease, diabetes or obesity.

What pulse oximeter reading means?

The pulse oximeter tells you two things,

• The oxygen concentration in your blood

• Pulse rate


Oxygen saturation (SpO2)Inference
96% to 100%Normal
<95%Potentially low oxygen in blood
<85%Significantly low oxygen in blood

Note: SpO2 close to 90, falling consistently should warrant medical help.


Pulse rate (beats/minute)Inference
60 to 100Normal
 >100Fast heartbeat (Tachycardia)
<60Slow heartbeat (Bradycardia)

Are pulse oximeter accurate?

The pulse oximeter is fairly accurate in measuring the blood oxygen level. It is highly accurate when measuring high level of oxygen in the blood (with accuracy of 90% at SpO2 92% or above). It gives an accuracy of 2% higher or lower than the actual reading.

The pulse oximeter accuracy falls down with decreased blood oxygen levels. It becomes less accurate below 80% oxygen saturation.

What factors can reduce the accuracy?

Some factors that impacts the acquisition of reading can affect the results. These are as follows:

Nail polish or artificial nail- remove it and take a reading

Skin pigmentation or very dark skin

Strong light- avoid very intense ambient light

Cold skin- warm the skin

Decreased blood flow

Excessive movement- avoid moving your limb or body

Abnormal hemoglobin or carboxyhemoglobin

Low blood oxygen level (SpO2 below 80%)


False normal resultFalse low reading
 CarboxyhemoglobinSevere anemia
 Type II diabetes possible (might occur with HbA1c levels>7)Abnormal hemoglobin types (Sickle hemoglobin, methemoglobinemia, sulfhemoglobinemia)
Venous congestion


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