Get That Out Of Your Mouth

"Her sats were in the high 80s. So, I took the nasal cannula out of her nose and put it into her mouth." 

I cringe every time I hear this. And I hear it at least once a month. Multiply that by 22 years and you get 264 times. That's 264 times someone has said that to me, or something similar.

Back in the day I'd take the cannula out of that person's mouth and put it back into their nose where it belongs. 

For crying out loud! It's called a nasal cannula, not mouth cannula. Just the idea that someone puts something that was in a person's nose and puts it into their mouth sounds gross to me. How about you? 

"But, the sats shot up from 88% to 95% after I did it!"

Yes! True. But you can accomplish the same thing by other methods. You can turn the flow from 2lpm to 3 lpm or higher if needed. You can use a mask. You can use a Venturi Mask. That's what they were invented for. You can use a simple mask. So many better ways to increase oxygen and oxygen levels than by inserting a gross cannula into a person's mouth. 

I have tried explaining the science to people. In the past, I have explained how the sinuses act as reservoirs. As 100% oxygen enters the nares from the cannula, it builds up in the sinuses. When you inhale you are inhaling this oxygen plus some room air. So, you are still getting oxygen.

"But they have a stuffy nose!"

So! They still have sinuses. Air is still getting in.

"But they are mouth breathers!"

So. Even if you breathe in through your mouth, you are still going to entrain air and oxygen from the sinuses. You will still be inhaling that oxygen. 

"But... But... the oxygen sat went up when I did it." 

Fine. 

So, this is when I give up. And I no longer use science. Today, I just keep quiet about it. If the nurse wants to put a nasal cannula into a person's mouth, and the patient lets it happen, I just keep silence. 

If I say anything, it's "Gross!" 

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.