Two women wearing oxygen delivery devices, cannula, oxygen mask, breathing, getting enough air

Oxygen Levels and Supplemental Oxygen

When you have a chronic lung disease like COPD, doctors will often monitor your oxygen levels. If your oxygen levels are low, doctors may prescribe supplemental oxygen. So, what are oxygen levels, and what is supplemental oxygen? Here’s all you need to know.

What is oxygen saturation (SpO2)?

This is often referred to as the fifth vital sign, as it is often taken along with your other vitals: heart rate, respiratory rate, blood pressure, and temperature. It’s an estimate (and usually a very close estimate) of the percentage of oxygen you are inhaling that gets to your bloodstream. It is generally recorded as SpO2, which means peripheral oxygen saturation. A normal SpO2 is 98%, although greater than 90% is considered acceptable. In some special cases of severe COPD, your doctor may find that less than 90% is acceptable for you.

What is a pulse oximeter?

Most hospitals have these now as standard equipment. They are small devices that slip over a finger, toe, or earlobe. In fact, they have been around long enough now that they can be purchased at stores like Amazon or Walmart for as little as $20. They measure your oxygen saturation. You can talk to your doctor about whether you should have one at home, although some people who require oxygen find it nice knowing what their oxygen levels are, allowing them to increase or decrease their oxygen intake as necessary (of course, with permission from their doctors).

What is arterial blood gas (ABG)?

While most blood tests require venous blood, this test requires arterial blood, or freshly oxygenated blood. The best place to draw it is on the thumb side of the inside of your wrist where the radial artery is close to the surface. It is important because it measures your arterial gases: oxygen and carbon dioxide.

What is arterial oxygen saturation (SaO2)?

This is the same as SpO2 although it is considered to be accurate as it is measured directly from your arterial blood. Normal is 98%, although greater than 90% is considered acceptable.

What is partial pressure of arterial oxygen (P02)?

This is an accurate measurement of inhaled oxygen that gets inhaled into your blood. A level of 80-100 is considered normal. 60-80 is considered mild hypoxemia, or mildly low blood oxygen level. Anything greater than 60 is often considered acceptable.

Why is a pulse oximeter such a useful tool?

It’s nice because a 60 PO2 usually correlates well with an SpO2 and Sao2 of 90%, which explains why 90% saturation is generally considered acceptable. This is important because it allows you to measure your oxygen levels simply with a non-invasive pulse oximeter rather than having to undergo an invasive blood draw. So, this allows your doctor to conveniently check your oxygen levels in the office, or even for you to do so in the convenience of your own home.

Why is an ABG useful?

Chances are your doctor will want to obtain an accurate measure of your arterial oxygen levels just to make sure they correlate with your SpO2 reading. Likewise, an ABG can also provide your doctor with lots of other useful information such as I explain in my post, “What Is An ABG?”

What is supplemental oxygen?

It is when your lungs require more oxygen than what is provided to you in room air to oxygenate your blood. Room air contains about 21% oxygen, so supplemental oxygen would entail inhaling anywhere from 21% to 100% oxygen.

What devices supply supplemental oxygen?

The most common device used to provide it to you is a nasal cannula. This is a lightweight and easy to tolerate plastic device with prongs that enter your nares. A low flow enters your nose and your lungs along with oxygen in room air. Usually, this provides your lungs with all the supplemental oxygen needed to adequately maintain healthy and normal oxygen levels in your arterial blood.

When is supplemental oxygen needed?

Supplemental oxygen is usually indicated when your oxygen saturations are consistently less than 90% or your PO2 is less than 60. Medicaid will only pay for supplemental oxygen if you qualify. Their qualification requires that a caregiver measuring your oxygen saturation while you’re walking. If it drops below 88% you qualify.

What happens if I qualify for supplemental oxygen?

Your doctor’s office will set you up with an appointment by the home health care provider of your choice. This person will bring all the equipment you need to your home and teach you how to use it. You will probably use an oxygen concentrator, which is a small machine that turns room air into pure oxygen for you to inhale. You will hook up your nasal cannula to this concentrator. Your provider will probably also provide you with some oxygen tanks to use for when you leave your home. Oxygen tanks also work nice should the electricity go out and your concentrator stop working.


Low oxygen levels due to COPD may cause you to feel short of breath. Supplemental oxygen can help you breathe easier, and it’s also proven to help you live better and longer with COPD. So, with a diagnosis of COPD, your doctor will want to monitor your oxygen levels so supplemental oxygen can be prescribed when needed.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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