What Are Safe Oxygen Levels?

Some people in this community require oxygen therapy. Another term for this is supplemental oxygen therapy. Others in this community wonder if they would benefit from oxygen therapy. So, how do you know if you need oxygen? What are safe oxygen levels? Here’s what to know.

When is room air oxygen not enough?

Room air contains 21% oxygen.1 For healthy people, this is plenty of oxygen. However, for some people with heart disease, this is not enough. With heart failure, your heart becomes a weaker pump. Over time it becomes less effective at pumping oxygen-rich blood through your body. This may cause your oxygen levels to drop.

When oxygen levels drop, you may become short of breath or winded. The most likely time for this to occur is when you are exerting yourself. This is because your heart has to work harder when you are active. However, for some with heart failure, this may occur only while you are sleeping. For others, it may be an all-day thing.

When this happens, you may require more than 21% oxygen to maintain safe oxygen levels. Thankfully, there are many devices that can deliver up to 100% oxygen if you need it. However, before I explain these devices, I figured I’d explain oxygen levels.

What is the most accurate oxygen level?

The most accurate oxygen level we monitor is the partial pressure of arterial oxygen (PaO2). This is the level of oxygen that is in your arterial blood. It is obtained by an invasive test. The test is called an Arterial Blood Gas (ABG). While most other blood tests can be done with a simple venous poke, an ABG requires arterial blood. The most common location it is drawn from is an artery on the backside of your wrist. Once drawn, your blood is run through a machine.2

The gas we are interested in is PaO2. This is short for “partial pressure of arterial oxygen.” It is the most accurate measure of how much oxygen is in your arterial blood. Your PaO2 is measured as follows:2

  • Normal is 60-106
  • Mild hypoxia is 60-79
  • Moderate hypoxia is 40-79
  • Severe hypoxia is less than 40

Hypoxia is a medical term meaning that your arterial oxygen level is lower than normal. Obviously, if it gets too low you may start to feel short of breath or winded. So, our goal is to find out where you stand and find a device to get it back to normal and keep it there. Our goal is to keep your PaO2 above 60.2

What is an easier oxygen level to get?

Thankfully, we don’t always have to draw your blood to determine your oxygen level because we have pulse oximeters. A pulse oximeter is a simple device that slips over your finger. It sends a light through your finger to measure your SpO2. This is basically your oxygen saturation (sat). It’s a percentage. It tells us what percentage of oxygen you inhale gets to your arterial blood.

Learning your SpO2 is easy and even better, it can be used to predict what your PaO2 is. As a general rule of thumb, we are usually hoping for a 90% sat or better.

An understanding of the basics

So, there are a couple of ways of determining your oxygen level. Your doctor may choose to do the more invasive ABG test. This will get an accurate PaO2 level for one point in time which can be very helpful.

However, the most common and easiest oxygen level to get is your SpO2. This can be checked at every doctor visit. A neat thing about pulse oximeters is they are easily portable. So, now we have devices that allow us to monitor your SpO2 while you are walking, and even while you are sleeping.

Now you understand the basic oxygen levels. You now know what oxygen levels are safe, or at least what oxygen level goals we are seeking.

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