Pulse oximeters have been flying off the shelves during the COVID-19 pandemic. We decode
how they work.
Back when TikTok reigned strong in India, there were hundreds of videos of people showing
that wearing a mask did not inhibit oxygen saturation. One user Emily Lyoness, who has
moderate persistent asthma, recorded herself wearing a spectrum of masks — from a reusable
fabric mask to a P100 mask — and tested her oxygen levels by clipping a pulse oximeter to
her index finger. The oxygen reading on the device wavered between 98 and 99.
People with COVID-19 often need oxygenation support, so this tool, a staple for many
doctors, has become something of a necessity for the layperson. Oximeters have been flying
off the shelves for many households’ first aid kits, largely because they are non-invasive,
low-cost, easy to use, and effective at detecting hypoxemia (low blood oxygen levels).
Device must-know’s
It comprises a monitor which contains the batteries and display; a probe, which consists of
light emitting diodes or LEDs and a light detector called a photo-detector. This probe senses
the user’s pulse.
There are two important readings: the pulse rate, recorded as beats per minute (60 to 100 is
the safe range); and the oxygen saturation of haemoglobin in arterial blood, the reading of
which is recorded as SpO2). Normal readings range from 95% to 100%; anything less, and
the user should get medical assistance from a doctor. If your oximeter has alarms, atypical
readings will set them off.
The mechanism clips onto the user’s forefinger, though some oximeters have been known to
be clipped onto one’s big toe or even the ear, depending on the model. According to the
World Health Organization’s Pulse Oximetry Training Manual, one must use the oximeter
with patience. Once clipped on, it requires about 10 seconds to get an accurate reading.
A pulmonologist based in Jaipur and chief editor of Lung India, Dr Virendra Singh points out
that pulse oximeters are not COVID-19 detectors. He states, one cannot use the pulse
oximeter as a sole detector for any respiratory issues. It is only meant to give readings for a
small time interval
When buying an oximeter, do be wary of the brand names. There are oximeters selling on ecommerce
platforms that will work for a month at most before giving out, and may cost as
much as about ₹2,000.
We’d suggest going to your pharmacy. Most Indian pharmacies have partnered with
legitimate names in the medical device sub-industry to provide cost-effective and reliable
pulse oximeters. Those who want to support India-made pulse oximeters can look to
AmbiTech, Oxysat, or Home Medix, among other names.
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