How to Use a Pulse Oximeter?

The factors that lead to faulty readings include Nail Polish...

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As the coronavirus continues to spread, a small medical device called a pulse oximeter has started to fly off the shelves. COVID-19 causes initial unnoticeable low arterial oxygen saturation and hypoxia. Therefore, pulse oximeters have been proposed in the early detection of COVID-19 infections. Studies of reliability show mixed results, but many doctors are advising patients to get one, making it the go-to gadget of the pandemic. The demand has spiked to such an extraordinary degree that you may not be able to buy one right now in your local pharmacy or online.

So, what is a pulse oximeter and how can it be used in COVID -19 Pandemic?

COVID-19 can lead to what’s called COVID pneumonia, an infection in which the lung’s air sacs fill with fluid or pus. But, it’s possible that someone infected with the novel coronavirus might be in the early stages of COVID pneumonia, including a drop in blood oxygen level, without experiencing any difficulty in breathing.

Pulse oximetry, a non-invasive and painless device, helps in measuring the oxygen levels in the blood. It can rapidly detect even small changes in the concentration of oxygen in blood carried to the extremities furthest from the heart, including the legs and the arms.

How to Use it & Basic Principle of Function:

To obtain the pulse oximetry reading, a small clamp-like device is placed on a finger, earlobe, or toe. Small beams of light pass through the blood in 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. Moreover, the pulse oximeter not only detects the oxygen saturation levels but can also monitor the heart rate.

A study conducted by Basaranoglu G (2015) [1], compared the oxygen saturation in the fingers of both hands with the pulse oximetry. They found that the right middle finger and right thumb have a statistically significantly higher value when compared with the left middle finger in right-hand dominant volunteers. They concluded that the right middle finger and right thumb have the most accurate value that reflects the arterial oxygen saturation.

Reading and Interpretation

An oxygen saturation level of 95% is considered normal for most healthy individuals. However, a level of 92% indicates potential hypoxemia or deficiency in oxygen reaching tissues in the body.

how to use pulse oximeter?

Hear Rate Range (beats per minute)

  • Newborn – 2years: 100-180bpm
  • 2-10 yrs: 60-140bpm
  • 10yrs – adult: 50-100bpm

How accurate is the pulse oximeter?

The oxygen level from a pulse oximeter is reasonably accurate. However, most oximeters give a reading + 2% in comparison to the saturation level obtained by an arterial blood gas. For example, if your oxygen saturation reads 94% on the pulse oximeter, it may be actually anywhere from 92 to 96%


Factors that can interfere with the accuracy of the readings include:

  1. Patient movement
  2. Cold Hands
  3. Nail Polish
  4. Smoking

The best reading, therefore, is achieved when the patients’ hand is warm, relaxed, and held below the level of your heart. If the patient is a smoker, unfortunately, the reading on oximeter may be higher than the actual oxygen saturation. This is because smoking increases carbon monoxide levels in the blood, and the oximeter cannot tell the difference between the gas carbon monoxide from oxygen.


  1. Basaranoglu G, et al. Comparison of SpO2 values from different fingers of the hands. Springerplus2015;4:561.


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