Low levels of oxygen in the blood—a condition known as hypoxia—can be a symptom of COVID-19, even when you don’t have shortness of breath or other symptoms. As many of us keep tabs on possible signs of the virus from home, pulse oximeters are the latest hot item to fly off shelves and into online shopping baskets.
According to the Federal Drug Administration (FDA), fingertip pulse oximeters may be a helpful tool to monitor blood oxygen levels. But there are limitations to using the devices and a risk of inaccurate pulse ox readings.
What is a pulse oximeter?
If you’ve heard the term “finger, please” in a medical office or hospital, you’re familiar with a pulse oximeter. The small electronic device clips onto your fingertip to measure heart rate and how much oxygen is in your blood.
Like taking your temperature or blood pressure, getting a pulse oximeter reading is standard practice in medical offices and a good way to know how well your body is working. It’s also used to track blood oxygen levels during surgery and is an especially useful to evaluate patients who have lung or heart conditions.
Here’s how it works:
- Infrared light emitted from one side of the device passes through the fingernail, skin, tissue and blood.
- A sensor on the other side of the pulse oximeter measures the amount of light that passes through the finger without being absorbed by the tissue and blood.
- Using the light measurement, the device calculates the percentage of oxygen in the red blood cells and displays a pulse oximeter reading.
Pulse oximetry is quick, painless and completely noninvasive. That makes it a welcome alternative to arterial blood draws traditionally used to check oxygen blood levels. Nonprescription pulse oximeters can be purchased for home use at some pharmacies and stores and online. (Yes, Amazon really does stock everything.)
Can a pulse oximeter detect COVID?
COVID-19 can cause inflammation in the lungs, which can diminish oxygen in the blood. But COVID can also be tricky. Some people with the virus might feel very sick and have normal blood oxygen levels. Others may feel well but have poor oxygen levels. Therefore, a pulse oximeter isn’t a reliable tool to diagnosis COVID.
The American Lung Association says patients with symptoms of COVID-19 really should focus on other signs of the virus, including fever, respiratory rate, pulse, cough and shortness of breath. Low pulse oximetry readings are just one sign or symptom.
If you have symptoms of the virus or have been in close contact with someone who has it, the best way to tell if you have COVID is to get tested.
How do I use a pulse oximeter at home?
If you use a pulse oximeter at home, follow the manufacturer instructions included with your device to ensure you get the most accurate reading. In general:
- Sit in an upright position, if possible.
- Place unit on your index or middle finger.
- Make sure your hand is warm, relaxed and held below heart level.
- Sit still and keep your hand steady in a resting position.
- Wait about a minute until the reading displays one steady number. Do not press the pulse oximeter while the reading is being taken.
How do I interpret a pulse oximeter reading?
Your pulse oximeter will display two results: blood oxygen level (SpO2) and pulse rate (PR).
Interpreting SpO2 levels:
- Normal oxygen saturation readings, or SpO2, range from 95 to 100%
- A person is considered hypoxic if an SpO2 reading is below 90%. This means you may not be getting enough oxygen in your blood to meet your body’s needs.
- A severe hypoxic state is 85% or lower for more than 2 minutes.
Blood oxygen levels can vary for people with certain medical conditions, such as lung disease. Your doctor can let you know what is “normal” for you.
A normal pulse rate should be between 60 and 100.
Multiple factors can affect the accuracy of pulse oximeter readings, including:
- Something blocking the infrared light, such as nail polish, artificial fingernails or a tattoo.
- Cold hands or poor circulation.
- Skin thickness.
- Current tobacco use. Smoking increases carbon monoxide levels in the blood. A pulse oximeter can’t tell the difference between blood carrying oxygen and blood carrying carbon monoxide.
- Skin pigmentation. Studies suggest that pulse oximeters may be less accurate in people who have dark skin color.
- Anemia and other nutritional deficiencies.
- Direct bright light on sensor.
Some patients with low oxygen levels may not show any of these symptoms. Only a medical provider can diagnose a medical condition, such as hypoxia.
What is a normal Sp02 oxygen level for COVID-19 patients?
If you have COVID-19 and you’re using a pulse oximeter at home to monitor your oxygen levels, your Sp02 (oxygen saturation) reading should consistently stay around 90 to 92%. If that number dips lower, contact a medical provider.
A pulse oximeter is just one way to gauge blood oxygen. Other signs or symptoms of low oxygen levels include:
- Bluish coloring in the face, lips or fingernails.
- Shortness of breath, difficulty breathing or a cough that worsens.
- Restlessness or discomfort.
- Chest pain or tightness.
- Fast or racing pulse.
What is silent hypoxia?
Hypoxia is typically accompanied by shortness of breath or chest pain. But amid the pandemic, a more serious phenomenon has emerged.
Silent hypoxia, also known as happy hypoxia, occurs when oxygen levels in the body are abnormally low, but the individual may appear well and not have any other major symptoms. Severe cases of this form of oxygen deprivation can cause serious damage to vital organs if left undetected and untreated for too long.
How much should I pay for a pulse oximeter?
According to Consumer Reports, over-the counter pulse oximeters usually cost $25 to $100. The FDA does not review these products and they do not require a prescription. Reliability of these devices can be wide ranging. Studies show many consumer-grade pulse oximeters do not provide accurate readings, while others provide readings similar to FDA-approved pulse oximeters.
Medical-grade pulse oximeters are typically used in clinics and hospital settings and are labeled “for medical use” and “FDA approved.” These devices require a prescription and can range from $70 to $250.
Should I have a pulse oximeter in my home first aid kit?
In the event you or a family member gets COVID-19, you’ll want to stock up on some necessary supplies. But should a pulse oximeter be included alongside your thermometer, tissues and fever reducers?
Here’s what some of the experts think:
- The American Lung Association believes a pulse oximeter may be a recommended tool to use under the guidance of your health care provider, but focus on other COVID-19 symptoms, too.
- Pulmonologists at Yale Medicine believe pulse oximetry is most beneficial among patients who have clear COVID symptoms, such as cough, fever and shortness of breath.
- Other research indicates that earlier detection of silent hypoxia might keep more COVID patients off ventilators.
In a nutshell, a pulse oximeter could help if you have COVID, especially if you have an underlying condition, such as heart or lung disease. But before you click “buy,” talk with your doctor or a friendly provider at Indigo Urgent Care.
COVID symptoms? Indigo Urgent Care is here for you
If you or someone in your family has COVID symptoms, has been exposed to someone with the virus or needs a clearance test, schedule an appointment at Indigo Urgent Care. We’re here every day to get you evaluated, tested and on your way. We can also help address your concerns about pulse oximeter readings.
You can also check your symptoms with Indy, your virtual assistant. She’s always there to evaluate your symptoms and get you the care your need now—at an Indigo Urgent Care near you or via our convenient Online Care services, available 24/7.