Pulse oximeter: Here is all you need to know

These devices have a probe or sensor that looks like a plastic bag clip to be placed onto your fingertip, toe or ear lobe.

Published: 30th April 2021 06:15 AM  |   Last Updated: 30th April 2021 05:25 PM   |  A+A-

KOCHI: A pulse oximeter is a small device that painlessly and quickly measures your oxygen saturation level, or how much oxygen in your blood. These devices have a probe or sensor that looks like a plastic bag clip to be placed onto your fingertip, toe or ear lobe. A small screen on the probe displays an estimate of blood oxygen levels is in your limbs or other body parts. 

How does it work?
Light-emitting diodes, or LEDs, inside of the pulse oximeter probe give off multiple colours of light, including red. The light shines through the tissues of your fingertip, and the sensor on the other side picks it. Pulse oximeters check the density of light to estimate the number of blood cells carrying oxygen. 

What can affect Pulse oximetry readings?
A pulse oximeter reading is an estimate and may not always be accurate. As the light travels through your fingernail and tissue, several things can affect the accuracy of the SpO2 reading, including:
Skin colour: Skin with more pigment may cause some pulse oximeters to give slightly higher readings.
Problems in the circulation system: Poor blood circulation in your hands and fingers may cause lower readings.

Dr Tinku Joseph K 

Cold hands: Having cold hands may cause lower readings.
Wet skin: Water or sweat on the skin may reflect the light and affect the measurement.
Bright light: Exterior bright light may interfere with the light detector and cause inaccuracy 
Thick fingernails: Thick nails can block the light penetration and may cause lower readings.
Fingernail polish: Black, blue, and green nail polish may cause significantly lower readings.
Bruises or tattoos on the fingertips: Both may cause inaccurate readings. Try choosing a different finger or limb for a more accurate reading.

Understanding Pulse oximeter readings 

  • A blood oxygen saturation level of 95 to 100 per cent on your pulse oximeter is a normal reading for healthy adults and kids.
  • If your reading is lower than this more than once, contact your doctor right away.

Signs of low blood oxygen levels

  • Difficulty in breathing 
  • Fast & shallow breathing
  • Confusion
  • Blue tinged lips or face

Caring of your Pulse oximeter

  • Keep the battery fully charged
  • Disinfect with an alcohol swab after usage

Tips for taking readings with a pulse oximeter

  • Make sure your hands aren’t too cold or hot, or wet or sweaty.
  • Keep your hand and fingers still. Don’t move while you’re taking the reading.
  • Avoid placing the pulse oximeter probe on a fingernail that has nail polish or on tattooed skin

(The author is the Chief of International Pulmonology at Amrita Institute of Medical Sciences, Kochi) 


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