How Does A Pulse Oximeter Measure Heart Rate

A pulse oximeter is a small and light device that looks like a clip. You attach it to a part of your body like the fingers, toes, or earlobes as a non-invasive way of measuring your oxygen saturation level. These devices can quickly detect even the slightest changes of oxygen levels in your blood to see how much of it is carried to the extremities far away from the heart i.e. hands and legs.

Oximetry refers to the measuring and monitoring of the level of saturation of oxygen in the blood.

Heart Rate

The heart rate is defined as the estimated number of times that the heart contracts per minute. Normal heart rate ranges between 60 and 100 beats per minute for adults.

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When the heart beats, it forces blood to be transported throughout the body. During each contraction, blood gets squeezed into the capillaries slightly increasing their capacity. The volume decreases between the heartbeats. As a result, there are changes in the amount of light such as red or infrared light that gets transmitted through the capillaries. Although these fluctuations are quite minute, they get can be measured by the pulse oximeter.

Blood Oxygen Levels (SpO2)

The measurement is done by assessing the oxygen-carrying pigment found in red blood cells – hemoglobin. The pigment can exist in the oxidized or reduced forms denoted as HbO2 and Hb respectively.

pulse oximeter principle

One interesting fact about hemoglobin is that it reflects and absorbs light. This property makes it possible to compare the relative intensities.

The level of blood oxygen saturation is usually expressed as a percentage. The normal reading of a healthy person should be 95% or higher. A SpO2 of below 92% suggests that the blood is poorly saturated with oxygen. Insufficient oxygen levels can result in several health problems like chest pain, increased heart rate, and shortness of breath.

How does a pulse oximeter work ?

These devices are commonly used in critical care settings like hospital emergency rooms, by pulmonologists in their office to check the pulse, by pilots in unpressurized aircraft, or by fitness enthusiasts in gyms.

why is pulse ox important

There are two main methods through which a pulse oximeter works:

  1. Measures the light transmitted through a tissue – transmissive oximetry
  2. Measures the light transmitted by a tissue –reflectance oximetry

In a nutshell, a pulse oximeter works by measuring changes in frequencies of light absorption in oxygenated and deoxygenated blood.

Once the test is done, the caregiver will determine what mode of treatment is appropriate. If you’re using it at home, consult with a doctor on what to do if the readings go above or below a certain reading.

how to measure heart rate

Uses and Purposes

The main reason for which a pulse oximeter is used is to check how effective the heart is in pumping oxygen through the blood vessels. It’s commonly used to monitor the health of individuals with the following conditions:

  • Asthma
  • Anemia
  • Pneumonia
  • Lung cancer
  • Heart failure
  • Heart attack
  • Congenital heart defects

The oximeter checks:

  • Whether or not a patient needs help breathing
  • Oxygen levels after a surgical procedure
  • If a ventilator is being helpful
  • If lung medication is working well
  • If supplemental oxygen therapy is effective
  • How well a person tolerates increased physical activity

How do I go about selecting the right pulse oximeter ?

A pulse oximeter must give accurate readings. How do you choose one that is best for your needs? Here are some questions that you need to ask yourself:

  1. How accurate are the oximeter’s readings?
  2. How easy is it to use? Is the display large enough? Will the oximeter tell you if your finger is placed correctly?
  3. Can the device work on several different patients and still give accurate results even for those with darker skin or low blood circulation?
  4. Will it work on different patient size ranges including very small fingers and large ones?
  5. Check to see who offers the best warranty and excellent customer service. Will they help if you have a problem with the oximeter?
  6. Durability and reliability. How long is the machine expected to remain functional?
  7. Is the oximeter environmentally friendly or does it introduce hazardous materials into the environment?
  8. Lastly, check to see if the oximeter can be integrated into other systems


You can count on these heart rate monitoring devices to give you a quick and accurate insight on your blood oxygen levels. This is very empowering as it allows you to respond quickly to any alarming changes depending on your lifestyle.

The human eye cannot be trusted to make a trustworthy judgment when it comes to detecting a person’s oxygenation status. If you have hypoxia resulting from heart conditions or breathing problems you should get a personal pulse oximeter for in-house use to get objective results that are more reliable.

To get pulse rate instantly you can check out – Best Blood Pressure Watch

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