You may not recognize its name, but you’ve probably seen an oximeter before (perhaps in a doctor’s office or hospital): the oximeter is an instrument that allows you to measure and monitor the degree of oxygen saturation in the blood. There is no difference between an oximeter and a pulse oximeter – they are always the same instrument. This device, costing a few euros, can be useful for monitoring coronavirus symptoms, along with other respiratory conditions.
Just like a thermometer reads temperature, the oximeter (which clips onto your finger) reads blood oxygen levels and heart rate. But unlike thermometers, which practically everyone has at home, pulse oximeters are not as popular. COVID-19, however, could change all of that.
What is an oximeter?
A oximeter is a device that measures oxygen levels (or oxygen saturation) in the blood, particularly peripheral oxygen saturation, since it is detected peripherally (externally) on a finger, or on an ear. Oxygen saturation is an important value, because blood (especially the proteins in red blood cells) carries oxygen throughout the body and releases it into the tissues.
Pulse oximeters also measure pulse rate, in terms of heartbeats per minute – this can also indicate how well the body’s tissues are “perfused” or supplied with blood and, ultimately, oxygen.
In terms of COVID-19, an oximeter can help detect or monitor respiratory problems associated with COVID-19 pneumonia. The devices can be especially useful for those suffering from shortness of breath with already diagnosed COVID-19, either to keep an eye on progress or to determine when an emergency room visit is worthwhile.
How do you use an oximeter?
The device attaches to the finger, or to the earlobe. Most commonly, it is a clip to be placed on the finger, and it transmits the wavelengths of the light emitted to a sensor that accurately calculates the oxygen saturation in the blood. This wavelength makes it possible to detect hemoglobin, a protein in the blood that carries oxygen: the light absorbed by the blood varies with the oxygen saturation of hemoglobin.
The best way to test is seated, and typically the chosen finger to hook the oximeter to is the middle finger. Make sure you remove polish from your nails, avoid using the device on cold fingers, and sit without moving too much: if you have cold fingers, you wear nail polish or if you shake, a correct reading may not be found.
What is a normal oximeter reading?
For a healthy person with no lung problems, a reading between 96-100% represents a normal blood oxygen level. WHO lowers this by 1%, stating that any value between 95 and 100% is normal, and any reading below 94% should be evaluated by a doctor. An oximeter reading below 90% is considered a “clinical emergency“, and according to the WHO should be treated urgently.
If you think you have COVID and are using the oximeter to measure your oxygen level, be sure to keep a log of the readings so you can assess if there are any changes. Plus, numbers aren’t the only thing you should be focusing on. Write down how you felt at the time of reading, such as whether you felt good or suffered from shortness of breath.
It is important to keep track of the second number and also the heart rate, so that you can report them to your doctor. According to the WHO, a normal heart rate (aged 10 years or more) varies between 60 and 100 beats per minute.
Are smartphone apps valid?
For now, it’s definitely best to refer to fingertip oximeters – there are some smartphone apps that claim to measure oxygen levels, but recent research by the Oxford “COVID-19 Evidence Service” team has shown that none of them are reliable enough to replace a real oximeter.
Below is a selection of the best pulse oximeters currently available on Amazon.