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Learning About Using a Pulse Oximeter

What is a pulse oximeter?

A pulse oximeter is a device that checks to see how much oxygen your blood is carrying.

Usually a small clip is put on the end of your finger. The device shines a light beam through the skin. It estimates your oxygen level by measuring the percentage of your blood that's carrying oxygen. Your oxygen level (or oxygen saturation, SpO2) shows on the display screen.

A pulse oximeter also displays your heart rate or pulse rate. It is important not to get these numbers confused with your oxygen level (SpO2).

Pulse oximeters are used in doctors' offices and hospitals. Some people use one at home.

Why is it used?

A pulse oximeter is used to watch for changes in oxygen levels. Your doctor may suggest using one at home if you have a condition that affects your oxygen level. Your test results and changes in your symptoms are used together to check your health and make decisions.

How do you use a pulse oximeter?

Follow the instructions that come with your oximeter. Here are the steps:

  1. Be sure your hand is warm.
  2. Sit quietly for a few minutes.
  3. Turn on your oximeter. It is important to keep the oximeter sensors clean and to protect your oximeter from bright lights.
  4. Keep your nail facing up. Clip the device on the end of a finger. Use a finger that doesn't have nail polish or an artificial nail. If you have nail polish or an artificial nail that you cannot remove, sometimes the oximeter will give better results if you turn it on its side before clipping it on the end of your finger.
  5. Hold your finger still and below the level of your heart.
  6. You'll see results in a few seconds. Wait until you see one steady number for the oxygen level.

Your doctor can help you know what numbers are normal for you.

Ask your doctor how often to check your oxygen level. Your doctor may suggest checking it at different times, during exercise, or anytime your symptoms get worse. Keep a record of your levels, and watch for changes. Watch for new or worse symptoms. Your doctor can tell you what to do if you notice your levels are getting lower.

What affects your results?

Many things can affect your results from a pulse oximeter. These include darker skin colours, skin thickness, tobacco use, irregular heart rate, bright lights or sunlight, and poor blood flow in your finger. The device also may not show accurate results if you have cold hands or if you wear nail polish or artificial nails.

If any of these apply to you, a pulse oximeter may miss low oxygen levels. You may not know that your levels are low and that you need medical care. So it's important to watch for symptoms along with changes in your oxygen levels. Talk with your doctor about symptoms you may have with low oxygen levels. These symptoms include fatigue, weakness, and shortness of breath.

When should you call for help?

Your doctor probably told you what numbers to watch for when you use your pulse oximeter. If not, here is some guidance.

If you have certain health problems, like COPD, your oxygen level may always be lower than 95%. Ask your doctor what oxygen number you should expect when using your pulse oximeter. Find out which number is a sign that you should call for help.

Watch closely for changes in your health, and be sure to contact your doctor or nurse advice line if:

  • Your oxygen level is getting lower over time.
  • You are worried about your levels.
  • You have new symptoms or your symptoms get worse.
  • You are not getting better as expected.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

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