Pulse oximeter – How it works

During a 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 of light absorption in oxygenated or deoxygenated blood. This is a painless process.

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

Pulse oximeter - How it works
Pulse oximeter – How it works

Pulse oximeter accuracy

Universal access to pulse oximeters around the world is often limited by cost and has important consequences for public health. Low-cost pulse oximeters are increasingly available with limited oversight from regulatory agencies.

Many inexpensive pulse oximeters sold to consumers show very inaccurate readings. Unexpectedly, the accuracy of some inexpensive pulse oximeters tested here performed similarly to the more expensive, ISO-approved units when measuring hypoxia in healthy subjects.

However, further development of low-cost and accurate oximeters for use in clinical practice is feasible.

The Food and Drug Administration (FDA) requires that all pulse oximeters marketed for medical use in the United States have been tested and certified.

The great majority of calibration and confirmation tests are done on healthy volunteer subjects.

Pulse oximeter for home use

The oxygen concentration is measured with a device called a pulse oximeter. Although not many people know it, it is a medical device originally developed in Japan that later spread to the rest of the world.

The pulse oximeter makes it possible to measure the saturated oxygen concentration (SpO2) —oxygen bound to hemoglobin— immediately, projecting two types of light with different wavelengths on the fingertip and analyzing the light that is filtered without being absorbed.

The more oxygen is bound to the hemoglobin, the lighter the red hue of the light. The oxygen concentration in blood is calculated by digitizing the intensity of the color.

Fingertip pulse oximeter

Current pulse oximeter models have been greatly simplified, a small clamp-like sensor device is attached to the fingertip to measure heart rate and oxygen concentration, and displays them on a small, built-in screen.

The maximum concentration is 100% and the normal value is between 99% and 96%. A concentration below 90% is considered too low and is treated immediately by supplying oxygen to the patient.

  • The vital signs that are usually measured in the hospital are four:
    1. blood pressure
    2. heart rate
    3. respiratory rate and
    4. temperature
  • But the concentration of oxygen in the blood is such an important value for life that the pulse oximeter is said to measure the fifth.

More on this story

Pulse Oximeters: Answering Your Frequently Asked Questions

Which finger is best for pulse oximeter

Which finger is best for pulse oximeter?

As per the studies, your right hand’s middle finger shows the best results. Make sure to take off any nail polish and avoid using cold fingers as the readings may not show correctly.

Pulse oximeter normal reading

Pulse oximeter Normal Reading

Blood gas measurements provide critical information regarding oxygenation, ventilation, and acid-base status.

Fingertip Pulse Oximeters

Pulse Oximeters

  • What is the best pulse oximeter?
  • What is a normal oxygen saturation level?
  • Are any oximeters made in the USA?
How to increase perfusion index?

How to increase perfusion index?

First, you have to understand the perfusion index and the Spo2 values (Plethysmograph).