The 88-92% Rule: Why "Lower" Oxygen isn't always bad with COPD

If you live with chronic obstructive pulmonary disease (COPD), you may have noticed something confusing. Most healthy people are told their oxygen level should be 95 to 100 percent. But many COPD patients hear something very different: “We like your oxygen between 88 and 92 percent.”

Wait a second. Why would a doctor be okay with a number that low?

As a respiratory therapist, I’ve been asked this question many times over the years. And the answer often surprises people. The goal isn’t perfect oxygen numbers. The goal is safe oxygen levels.

What your oxygen levels mean

Before explaining why, it helps to understand what that number actually means. When a nurse or respiratory therapist clips a small device over your finger – called a pulse oximeter – it measures something called oxygen saturation. This tells us how much oxygen is attached to the red blood cells in your bloodstream.

Think of your red blood cells like little delivery trucks carrying oxygen through your body. Oxygen saturation simply tells us how full those trucks are. If your oxygen saturation is 98 percent, that means about 98 out of every 100 oxygen-carrying spots in your blood are filled. For healthy people, that number usually runs between 96 and 100 percent.¹

But COPD lungs work differently – and that’s where the 88 to 92 percent rule comes in.

COPD lungs work differently

Healthy lungs move oxygen into the blood and remove carbon dioxide without much trouble. When everything is working normally, oxygen levels stay high without much effort.

COPD lungs are different. The airways are damaged, and air gets trapped. Some parts of the lungs receive oxygen but not enough blood flow, while other parts receive blood flow but not enough oxygen. Respiratory therapists call this V/Q mismatch.²

You don’t need to remember that term. The important thing is that COPD lungs simply don’t exchange gases as efficiently as healthy lungs. Because of this, many people with COPD naturally run lower oxygen levels – and for them, that may be completely normal.

This is where things get interesting. You might have heard someone say that giving too much oxygen will “knock out a COPD patient’s drive to breathe.” That idea gets repeated a lot, but it’s not the whole story.

What usually happens is something a little different. When very high levels of oxygen are given, it can change how blood flows through damaged areas of the lungs. Blood gets sent to parts of the lungs that aren’t working well, which can cause carbon dioxide to build up in the bloodstream. When carbon dioxide rises too high, patients may become sleepy, confused, or lethargic.³

So instead of pushing oxygen levels as high as possible, doctors often aim for a safe middle range. That range is usually 88 to 92 percent.⁴

At that level, the body still gets enough oxygen to keep the organs working while lowering the risk of carbon dioxide buildup. Think of it as a balance point. Too little oxygen is dangerous. But in severe COPD, too much oxygen can sometimes create problems as well. Doctors aim for the sweet spot in the middle.

Is the 88-92% range right for everyone?

There are exceptions. If you become very sick or have a bad flare-up, your oxygen levels may drop too low. In those situations, we can safely give higher levels of oxygen in the hospital, where you can be closely monitored.

It’s also important to remember that this rule doesn’t apply to everyone with COPD. Some patients need higher oxygen levels, while others do well at slightly lower numbers. Your doctor or respiratory therapist looks at the whole picture – your symptoms, blood gas tests, and how you feel – not just the number on the monitor.⁵

What this means for you

If you’ve ever seen your oxygen reading around 90 percent and worried that something was wrong, you’re not alone. But for many people living with COPD, that number may be exactly where their doctors want it.

It doesn’t mean your care team is ignoring the problem. It means they are carefully balancing oxygen therapy to keep you breathing as safely and comfortably as possible.

So, now you know. If you’re worried or wondering whether your oxygen levels are safe, this is a great conversation to have with your healthcare provider.