Fact-Check: Can Oximeters Show ‘Oxygen Level’ of Pens & Biscuits?
Though not 100 per cent accurate, oximeters can give us a rough idea about our blood oxygen level.
A video going viral showing a pulse oximeter displaying the “oxygen levels” of biscuits, pens and other non-living things has left people confused and wondering if the pulse oximeters are a "scam".
However, we studied the working of an oximeters and found that it detects oxygen levels based on the amount of infrared light falling on its sensors. Therefore, it is possible that it might display a reading even when a non-living thing is placed in between it's sensors.
The video shows a person place two biscuits inside an oximeter and turning it on, following which the oximeter shows a reading.
The person in the video says, "We can see that the oxygen level of the biscuit is 99 and heart beat is 110. So, does the biscuit have a heart, does it have oxygen in it?"
He then goes on to say that the sellers are duping people in the name of coronavirus and selling fake oximeters.
A similar video had gone viral a few days ago where a child could be see putting a pen in the oximeter and the oximeter showing a reading.
The background voice of man can be heard saying, "Media is unnecessarily scaring people. Sketch pen has a heartbeat of 200 and oxygen level of 98. What sort of hypocrisy is this? Beware of this.”
WHAT WE FOUND OUT
To the check if the claim made in the viral video was true, we looked up the working of the an oximeter.
Pulse oxymetery has been used to monitor patients in the critical care settings. Dr Takuo Aoyagi has been credited with inventing pulse oximetry in 1974, that measures the oxygen saturation in the blood.
According to the US Food and Drug Authority (FDA), oxygen saturation values are between 95 and 100 percent for most healthy individuals, but sometimes can be lower in people with lung problems.
The pulse oximeter has a light-emitting diode (LED) and a sensor and gives an indication of the relative concentration of oxyhemoglobin and deoxyhemoglobin depending on the ratio of absorbance of red and infrared light. The absorption of light on the sensor will vary with each heart beat as the when the amount of arterial blood that is present increases.
British Lung Foundation () explains the functioning of the device - "A pulse oximeter measures how much light is absorbed by your blood. This tells us how much oxygen your blood contains. The pulse oximeter shines 2 lights through your fingertip or earlobe: one red light and one infrared light.
"Blood containing lots of oxygen absorbs more infrared light and lets more red light pass through it. Blood without enough oxygen absorbs more red light and lets more infrared light pass through it. If your blood cells do not have enough oxygen, they will appear bluer," it adds.
DO INANIMATE OBJECTS HAVE A "OXYGEN LEVELS"?
We reached out to Dr TV Venkateswaran, senior scientist at Vigyan Prasar, New Delhi, for us to understand why the readings were seen while checking non-living things.
If we put an inanimate object, such as a dead person's finger, in the pulse oximeter, it will give us a reading because the red light will pass through the finger. However, what we will not see is the pulse signature, like we find in a living person. People think they only need to see the numbers, but they also need to see the pulse.Dr TV Venkateswaran, senior scientist at Vigyan Prasar
It is important to note that none of the oximeters are 100 percent accurate, however, they do give a fair idea about one's blood saturation levels.
Dr Venkateswaran told us that the readings could be affected by the variations in the thickness of the fingers, movement, temperature, or nail polish.
According to the FDA, pulse oximeters are least accurate when oxygen saturations are less than 80 percent and most accurate when the oxygen levels are between 90-100 percent. Therefore, the FDA advises to monitor trends over time instead of absolute thresholds.
The Ministry of Health and Family Welfare (MoHFW) released a list of to 'dos and don'ts' in a document titled "Home care tips for managing COVID-19". The ministry recommended people having COVID-19 and undergoing home treatment to monitor their oxygen levels with a pulse oximeter 3-4 times in a day.
IndiaCOVIDSOS, a volunteer group consisting of scientists, clinicians, engineers, policy-makers and epidemiologists, has recently published a video explaining how to use a pulse oximeter at home.
Evidently, the claim that oximeters are a "scam" for showing readings for inanimate objects is false. The oximeter might display a reading when varying intensity of light passes through an object and falls on the detector.
However, it must also be noted that the quality of non-approved, over-the-counter devices, or digital apps can be inaccurate and there is no data available on that so far.
(This story has been published as a part of The Quint’s COVID-19 fact-check project targeting rural women. It was flagged to us by our partner organisation Video Volunteers.)
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