Can't Go Higher Than 6L on a Nasal Cannula? Poppycock!

We've had access to nasal cannulas since the 1960s, and early studies determined the best flow rates. Back then, it was believed that the maximum effective flow rate was 6 liters per minute (LPM). Higher flows, it was thought, wouldn’t make a difference. Well, since then, we’ve proved that idea is poppycock.

It happens too often. I get called to a patient's room because the SpO₂ is less than 88%. The nurse has already turned the nasal cannula up to 6 LPM and says, "I would have turned it up higher, but we were taught you can't go higher than 6 LPM on a nasal cannula."

So, I come in, turn the flow up to 8 LPM, and the SATs come up to 88%. The nurse looks surprised and says, "Oh, I was taught you can't do that."

Well, here's the thing: if it works, it works—so why not use it? But I still hear, "But we were told not to!"

And that’s the real issue. Somewhere along the way, outdated rules about flow limits became ingrained in practice without a full understanding of why. Traditional nasal cannulas are often recommended for flows up to 6 LPM to avoid discomfort or drying out the nasal passages. Additionally, as mentioned earlier, flows higher than 6 LPM were once believed to be ineffective. However, in acute situations, improving oxygenation must take priority. If increasing the flow achieves the desired result and the patient tolerates it, why not use it?

It's time to rethink rigid rules and prioritize what truly benefits the patient in the moment.

Today, nasal cannulas can deliver flows up to 15 liters per minute and even higher, often with great success. If you’re in a pinch with a patient on 6 LPM and their oxygen saturation (SAT) is still under 88%, there’s no reason you can’t turn the nasal cannula up to 8 or even 10 LPM. I’ve seen this work just fine.

Rather than immediately running to grab a mask or high-flow nasal cannula equipment, simply increasing the cannula flow rate beyond 6 LPM can buy you valuable time. This quick adjustment allows you to focus on stabilizing the patient or addressing other needs in the room. Once the patient is stable, or you’ve completed your immediate tasks, you can then set up the necessary high-flow equipment to provide the oxygen they need.

If you aren’t nearby and a nurse reports that the patient’s oxygen saturation (SAT) is low, you can reassure them it’s okay to turn up the nasal cannula flow as high as needed to maintain adequate SATs. This approach helps the patient in the moment while buying you time to get to them. Whether you’re finishing your current task or walking to the patient’s location, this quick action can make a significant difference in stabilizing the situation until you arrive.

In many cases, this approach can prevent unnecessary delays and help ensure better patient outcomes. So, let’s put the outdated 6 LPM myth to rest and use the tools we have with confidence.