Oxygen and Pulse Monitors ? Uses, Readings and How They Work

A pulse oximetry device is used to measure your oxygen saturation level. This simple device offers a painless, non-invasive way to gauge how well oxygen is being sent to the parts of your body furthest from your heart, like your arms and legs.

The readings help doctors determine whether a patient needs extra oxygen.

The History of Pulse Oximetry

German physician Karl Matthes created the first two-wavelength ear oxygen saturation meter in 1935. His was the first device to measure oxygen saturation levels. Glenn Allan Millikan was the creator of the original oximeter in the 1940s.

Bioengineers Takuo Aoyagi and Michio Kishi developed pulse oximetry in 1972. They used the ratio of red to infrared light absorption to determine oxygen saturation.

By 1987, pulse oximetry had become part of the standard of care when administering general anesthetic in the United States.

The Importance of Pulse Oximetry

Every single organ and system in the body requires oxygen to survive. When cells are deprived of oxygen, they eventually begin to malfunction and die. Cell death can ultimately lead to organ failure.

Your lungs filter the oxygen you breathe and then distribute that oxygen into the blood through the hemoglobin proteins in red blood cells. These proteins are what provide your organs, tissues and every cell in your body with oxygen.

Pulse oximetry measures the percentage of oxygen in these proteins, which indicates how much oxygen your organs are receiving.

Uses for Pulse Oximetry

Pulse oximetry devices are used to determine whether there’s enough oxygen in the blood. This information may be needed in a few different scenarios, including:

  • Checking to see how well a person handles increased activity levels.
  • During or after a procedure that requires sedation.
  • To check for sleep apnea.
  • To gauge how well lung medications are working.
  • To determine whether an oxygen concentrator is needed to help with breathing, or to see how well a ventilator is working.

A physician may also use this device to check the health of a person with a health condition that affects blood oxygen levels, which includes:

  • Anemia
  • Heart failure
  • Heart attack
  • Pneumonia
  • Lung cancer
  • Asthma
  • COPD

In some cases, a doctor may recommend using a pulse monitor to measure oxygen saturation during exercise. Physical activity can improve a patient’s overall fitness and stamina, but it can also result in shortness of breath. A finger pulse monitor can help patients keep an eye on their oxygen levels while being active.

That being said, anyone who experiences shortness of breath, dizziness and/or difficulty breathing should see a doctor right away.

Doctors may also use the device for other reasons. No matter the reason, it’s important to understand that the test is quick and painless.

Pulse Oximetry Readings

Pulse oximetry tests have fairly high accuracy rates, especially when high-quality equipment is used.

Most machines will provide results that are within a 2% difference of actual oxygen levels. That being said, there are many variables that may affect the accuracy of the reading.

Body temperature, movement and even nail polish can affect the outcome of the test.

Doctors will typically look for a reading of at least 89%, the level needed to ensure that your cells (and body) are healthy. A temporary reading that is lower than 89% is not believed to cause damage, but repeat instances of low oxygen saturation levels may indicate a problem and potential damage.

A normal, healthy individual will have an oxygen saturation level of 95%. A reading of 92% may indicate an oxygen deficiency. In other words, your tissues may not be receiving enough oxygen to stay healthy.

A reading under 90% is considered abnormal and may indicate a medical emergency. There are many reasons why oxygen saturation levels can drop, including:

  • Choking
  • Suffocation
  • Inhaling poisonous chemicals
  • Allergic reactions
  • Certain infections
  • Drowning
  • Sleep apnea
  • General anesthesia
  • Heart failure
  • Certain diseases, such as lung cancer and emphysema
  • Poor circulation or cold hands
  • Bilirubin levels
  • Changes in the pulse
  • Lipids in the blood plasma
  • Carbon monoxide poisoning

How the Device Works

A pulse oximetry device uses a probe, which is a clip-like device, to check oxygen levels. The probe is placed on a body part, such as the ear or a finger. Light is used to measure how much oxygen is in the blood.

Let’s say the probe is attached to your finger. The probe will then shine a light through your finger. Sensors will determine how much oxygen is in your blood based on how the light passes through your finger.

The probe is equipped with two LEDs: one infrared and one red. The LEDs transmit the lights’ wavelengths to a photodetector on the other side of the probe.

The device will then calculate the results and display a number on the screen. That number refers to the percentage of oxygen in the blood. The device can also measure your pulse rate.

The entire process is painless and non-invasive. Once the test is over, the probe will be removed.

Are There Any Side Effects?

A pulse oximetry device is non-invasive, so there is little risk of side effects. But some people may experience sensitivity, redness and minor irritation after use.

If the probe is fitted very tightly and for a prolonged period of time, the device may actually cut off oxygen to that part of the body. Changes in skin color, numbness and tingling are all signs that the probe is fitted too tightly.

The biggest risk is a false reading. The accuracy of the device, as mentioned previously, largely depends on having a correct fit and keeping still during the test.

If used to check for sleep apnea, for example, a person may roll over while sleeping and loosen the device, which would set off a false alert.

Because they’re so simple and easy to use, pulse oximeters are now available for consumers to purchase. Some companies market these devices to parents of infants who are concerned about sudden infant death syndrome (SIDS) and sleep accidents. But thus far, there is no research that supports claims these devices actually prevent accidents or SIDS.


About the author

Tim Brewer

Tim is a professional caregiver who has helped hundreds of seniors gain back their freedom and independence. He has been actively helping the senior community for 20+ years.

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