Nasal cannulas belong in the nose

As an RT, I'm certain that all of you guys, like myself, have come across the elderly patient with a nasal cannula stuffed into his mouth. We probably find ourselves explaining why the cannula does not belong in the mouth more than anything else.

This brings me to RT Cave Rule #10

RT Cave Rule #10: Nasal cannulas do not belong in mouths. Not only is this not necessary, it is unsanitary. The nasal passages and sinuses act as a reservoir for oxygen entering via the nasal cannula. Even if the patient is a mouth breather, or has a stuffy nose, the patient will still entrain oxygen via a properly inserted nasal cannula.

I find that most of the time I only have to explain this once, and the practice stops. However, we have our repeat offenders who insist that in certain situations that nasal cannula belongs in the mouth.

What one must be aware of is that a nasal cannula is a low flow oxygen device, which means that it will not guarantee a certain amount of oxygen gets to the lungs. As respiratory rate and tidal volume change, the amount of oxygen entrained increases and decreases.

Let's take one specific scenario that occurs often. You have a patient whose sats were consistently 93% all day on 2lpm. Now it is midnight, and the nurses assistant finds the patients sat is 89% on 2lpm. She relays this information to the nurse and the nurse assesses the situation and determines one of the following:

1. The patient is in a deep sleep


2. The patient is mouth breathing


3. The patient is has a stuffy nose

Thus, she decides that the nasal cannula should be placed in the mouth. Then, an hour later, the RT comes around and does one of the following actions:

1. He takes the cannula out of the mouth and places it back where it belongs, and leaves it at that.


2. He takes the cannula out of the mouth, and proceeds to educate the RN as to why this is not necessary and not sanitary.


3. He does nothing. He's tired and doesn't want to deal with it at the moment. Or, he's explained it so many times already he doesn't see what the point would be.

I have found myself in all three of these scenarios. Most of the time if it is a new nurse I explain why the cannula should not be in the mouth, but if it's a habitual offender, I might do action 1 or 3.

Okay, so the patient has a stuffy nose. The oxygen will find a way to work its way around the stuffy stuff, and make it to the patient's lungs.

Okay, so the patient is a mouth breather. The oxygen will still be entrained into the nasal passages and to the nasal sinuses and will still be entrained.

Okay, so the patient's sats have dropped. Check the connections. Turn up the oxygen. Assess the patient. Consider the patient's age and history and decide if it might not be normal for that patient to have a slightly lowered sat while from time to time, and leave the oxygen where it is.

Consider this too: it is normal for aging patients to have lower sats. It is also normal for elderly and chronically ill patients (like COPDers) to have decreased sats when they are sleeping. And, in the case of some COPD patients, sats in the high 80s can often be normal. So know your patient's history.

If the patient is in respiratory distress, or if you continue to be perplexed or concerned about the low sat, call RT. That's what we are here for. But -- please -- do not place the cannula in the mouth.

Think of it this way: would you want something that was stuffed into your nose in your mouth. I wouldn't. If a patient needs more oxygen, there are other options.