An oximeter, also known as a “pulse oximeter,” is a medical device that is used to check a person’s blood oxygen level in a way that is quick and non-invasive. 

It consists of a small monitor that is clipped onto the finger. Then, it calculates the oxygen levels of the blood, which is displayed as a percentage, called the oxygen saturation level (SpO2). 

Oximeters have long been used in hospitals and clinics and even by people going on high-altitude treks. However, it has gained widespread household use during the current Covid-19 pandemic as a tool to help detect and monitor symptoms.

Pulse oximeters are used to detect low blood oxygen levels (called hypoxemia). This can tell doctors and other medical professionals how well someone’s heart pumps oxygen throughout their body.

So, it is used to monitor several conditions that affect blood oxygen levels, such as asthma, anaemia, lung cancer, pneumonia, pulmonary diseases, heart attack or heart failure, and Covid-19.

Apart from checking blood oxygen levels, an oximeter can also be used for the following purposes:

• To check whether someone requires help breathing
• To assess how well someone is responding to a ventilator
• To evaluate how a person’s lung medication is working
• To monitor someone’s oxygen levels during or after a surgical procedure
• To determine how helpful supplemental oxygen therapy is to someone

You might be wondering, how does an oximeter work? It uses small beams of light that are passed through the body (completely painlessly). They measure the changes in the light absorption in the blood, and by doing so, the machine can calculate the amount of oxygen in the blood. It also calculates the heart rate or pulse. 

But how does someone actually use it? Well, this is how to use a pulse oximeter:

• Make sure your hand is relaxed, warm, and below heart level.
• Then clamp the oximeter device onto your index finger (sometimes it might need to be placed on the earlobe or toe).
• Keep it on for a few minutes until it shows the readings for the pulse and oxygen saturation (the numbers might jump around for a few seconds, so look for one steady number).
• In some cases, this process might need to be repeated, or kept on for a significant amount of time (such as during a hospital stay, during a surgery, or while monitoring physical activity capabilities).
• As soon as the test is over, the device will be removed. 

(Note that the pulse oximeter has a 2% error window. Essentially, this means that the readings might be 2% higher or lower than the actual blood oxygen level. Other factors like movement, temperature changes, henna, or nail polish can also affect the accuracy.)

There are two readings that are visible on the display of most oximeters – the pulse rate and the blood oxygen saturation level. 

The pulse rate, or the heart rate, is the number of times your heart beats in the span of a minute. For most healthy adults, a normal pulse range is between 60 to 100 beats per minute. However, this may change or fluctuate due to things like illness, exercise, and intense emotions. Additionally, in general, women tend to have faster heart rates than men. 

The oxygen level shown on an oximeter is just the percentage of how much oxygen is in your blood (as compared to the maximum amount it can hold). This is called the oxygen saturation level (SpO2), and a normal reading is usually between 95 and 100%.

However, it may be lower in the case of certain medical conditions such as chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome, asthma, congenital heart defects, or collapsed lungs. But, if you do not have such a condition and it is lower than 92-90%, you might want to consult your doctor.

The heart rate, or pulse, is used to measure how fast your heart is beating.  A heart rate that is too rapid (known as tachycardia) can be a sign of certain medical conditions, like an infection, anaemia, or heart disease. On the other hand, a low heart rate (called bradycardia) can be caused by some heart conditions and the use of some medications. 

On the other hand, the oxygen saturation level tells you how much oxygen your blood, and thus your body is getting. This oxygenated blood keeps all the parts of your body healthy and working. Not having enough blood oxygen can result in there being an inadequate oxygen supply to the organs and tissues of the body, which can affect the brain or heart.

The pulse oximeter test is quick and painless and can be completed in minutes. For most people, readings can be taken twice a day. However, for certain health conditions, it can be necessary to take readings every hour. You should check with your doctor to know exactly how often you should check your oxygen levels.

Pulse oximeters are used to detect low blood oxygen levels (or hypoxemia). Since one of the early signs of a Covid-19 infection is weakened lungs and low blood-oxygen levels, it can be useful to have access to an oximeter during the ongoing pandemic. 

However, it is important to note that pulse oximeters cannot detect Covid-19. It merely shows the oxygen saturation level for a short time interval. Therefore, it cannot be used to detect or diagnose the disease. Additionally, some people may feel very ill and have high oxygen levels, while others may feel fine but have poor oxygen levels.

If you display any of the signs or symptoms of Covid-19, or have been in contact with who has it, the only way to know for sure is to get tested.

However, if you have already been diagnosed with Covid-19, it can be helpful to use a pulse oximeter to check oxygen levels to know if they drop and you need medical care.

If possible, talk to your family physician about getting a pulse oximeter to use at home during the pandemic.