Mouth versus nasal breathing

[IDRIck]

First time poster here... Just started using a CPAP machine yesterday with a full face mask. Had a great night of sleep. AHI was 3.6 (last night) versus 130 during my sleep study! Wahoo, awesome improvement!

I've always been a mouthbreather. Several visits to MD's, including an ENT, with no success. Just can't get enough air through my nose. I'll start gasping for air within 5 minutes if forced to breath through my nose only. Last night on the CPAP, all the breathing was through my mouth and very comfortable with the humidifier. I know I should not believe everything I read on the internet but there are URL's that claim mouth breathing causes the same problems as untreated sleep apnea. Is this an accepted scientific view?

[trish6hundred]

Hi IDRIck, WELCOME! to the forum.!
Glad your first night went so well. Best of luck to you and hang tight for more responses to your post.

[Sleepster]

I know I should not believe everything I read on the internet but there are URL's that claim mouth breathing causes the same problems as untreated sleep apnea. Is this an accepted scientific view?

Of course not. That's why they make full face masks. I'm glad you were able to sleep well with your mask.

[PaulaO2]

What Sleepster said. The part of your body that is getting blocked by apnea events is your throat. So as long as the air pressure from the machine is getting there, you're good.

And if you mean mouth breathing during the day is the same as untreated apnea, that would still be wrong. It's the throat, not the mouth. Air gets to lungs either way.

[zonk]

full face mask will allow you the option to breathe thru your nose and/or your mouth
You want leak to be below 24 L/min ... its not the end of world if it goes over for a while
prolong leak over 24 L/min can affect the accuracy of data and sleep quality

[genes]

First time poster here... Just started using a CPAP machine yesterday with a full face mask. Had a great night of sleep. AHI was 3.6 (last night) versus 130 during my sleep study! Wahoo, awesome improvement!

I've always been a mouthbreather. Several visits to MD's, including an ENT, with no success. Just can't get enough air through my nose. I'll start gasping for air within 5 minutes if forced to breath through my nose only. Last night on the CPAP, all the breathing was through my mouth and very comfortable with the humidifier. I know I should not believe everything I read on the internet but there are URL's that claim mouth breathing causes the same problems as untreated sleep apnea. Is this an accepted scientific view?

IDRICK
I agree that the comments about mouth breathing problems with cpap do not apply when you use a full face mask. We are fortunate that full face masks have improved a lot the last few years. I tried to find a good full face mask maby 5 -10 years ago and it seemed like they were all poorly built and leaked. The full face masks now seem much better to me.

As far as the comment "mouth breathing causes the same problems as untreated sleep apnea. Is this an accepted scientific view?"

I have said something similar in the past. I was referring to mouth breathing while wearing a nasal mask. I have concluded that cpap treatment does not work while mouth breathing with a nasal mask so in a way it causes the same problems as untreated sleep apnea.

My opinion is based on engineering calculations so I guess it is my scientific view. Because I conclude this does not make it an accepted scientific view. There must be other engineers or technicians out there who are familiar with fluid mechanics who could do an independent analysis and either agree or disagree with me. I would like someone else to share thoughts with on these calculations.

I concluded that if you breath in thru your mouth while wearing a nasal cpap your airway and lung pressure must go negative (below atmospheric) or air could not flow from outside your mouth to your lungs.

Also when you exhale thru your mouth your lung and airway pressure will be positive but likely below your cpap set pressure.

Since cpap treatment requires a positive pressure in your airway cpap treatment does not work when you breath in thru your mouth with a nasal cpap.

My calculations use the following
1) The perfect gas law PV=NRT
2) The Bernoulli energy equation E = Pressure head + elevation head + velocity head.
3) E(1) = E(2) + energy loss from point 1 to point 2
4) H Loss in conduit is K f l/d Vsq /2g

I started with the first commercial cpap 27 years ago and was told by the support people that it did not matter if I breathed thru my mouth but I continued to have problems until I finally concluded on my own that I needed to eliminate mouth breathing which I did. I have had better results ever since. I guess because of this I tell everybody I know on cpap to eliminate mouth breathing so that they do not go thru what I did.

GeneS

[archangle]

Forget the Bernoulli (Venturi) effect.

From a practical standpoint, I can't believe the magnitude of the Venturi effect is significant in terms of mouth breathing. The velocity and passage size of the air involved and the density of air is too low to cause a significant pressure drop. Real world practical air venturi devices involve a lot more air flow to generate significant pressures.

I'll have to sit down and do some calculations at some time, but I've got to figure out some way to model the cross sectional area of the airway.

When you calculated the pressure drop, how did you model the airway? What cross sectional area did you assume for the passageway where the trachea joins the "pipe" between the nose and the mouth? Without some assumption for the cross sectional area of that "tube" and the size of cross sectional area of the tube, you can't calculate the pressure drop due to the Bernoulli/Venturi effect.

However, mouth breathing with nasal masks does reduce the effectiveness of CPAP. If the leak rate is too high, the machine can't keep the pressure in your airway high enough due to the limited amount of air the machine can pump, and the friction through the hose, mask, and your nasal passages.

If the liters per minute leak rate is low enough, you may not lose enough pressure to make the therapy ineffective, but the airflow will disturb you and it will dry out your nose and mouth. Even a small mouth leak the machine can easily handle will leave me with dry mouth and nasal passages, even with humidity.

I think even doctors and DMEs now realize that mouth leaks are a problem.

[genes]

Forget the Bernoulli (Venturi) effect.

From a practical standpoint, I can't believe the magnitude of the Venturi effect is significant in terms of mouth breathing. The velocity and passage size of the air involved and the density of air is too low to cause a significant pressure drop. Real world practical air venturi devices involve a lot more air flow to generate significant pressures.

Archangle
The Bernoulli equation and how I am using is shown on the following link.
http://www.ohiomedical.com/UserFiles/Fil...ystems.pdf
I know it is not quite the same application but I think the same principals pretty much apply.
Is this the same equation that you are using?
The bernoulli equation explains how the pressure will drop in the direction of flow due to friction and minor losses and also due to the venturi effect. I do not know what real world practical air venturi devices are. I think the venturri effect as you mentioned could be a big factor in sleep apnea. If your airway is constricted say behind your tongue as is common the cross sectional area is already significantly reduced thru the obstruction and then expands again after the obstruction. Due to the smaller flow area thru the obstruction the velocity would increase a lot which would be accompanied by a similar decrease in airway pressure to satisfy bernoulli's equation. This drop in airway pressure thru the area that is already obstructed could very likely trigger the airway to collapse in the constriction resulting in an apnea. Is this what you mean by venturri effect?
GeneS

I'll have to sit down and do some calculations at some time, but I've got to figure out some way to model the cross sectional area of the airway.

When you calculated the pressure drop, how did you model the airway? What cross sectional area did you assume for the passageway where the trachea joins the "pipe" between the nose and the mouth? Without some assumption for the cross sectional area of that "tube" and the size of cross sectional area of the tube, you can't calculate the pressure drop due to the Bernoulli/Venturi effect.

Archangle
It has been quite a while since I have done calculations on this so I am going to have to get into it again. It is necessary to make assumptions that can be put into the equations. I thought it would be interesting to try to model breathing without and with cpap using variables for airway size, flow, friction factors, obstructions etc. You could then write a computer program and then change the variables and see how the airway pressure changed etc. I do not know when and if I will have time to do this but it would be interesting to do.
GeneS

However, mouth breathing with nasal masks does reduce the effectiveness of CPAP. If the leak rate is too high, the machine can't keep the pressure in your airway high enough due to the limited amount of air the machine can pump, and the friction through the hose, mask, and your nasal passages.

Archangle
Right now we differ a little here. I think that when you breath in with your mouth with a nasal mask your airway and lung pressure has to be negative or air would not flow in. Since atmospheric pressure is zero air would flow out of your mouth instead of in if your airway pressure was positive. To me that means that cpap is not working at all when you breath in since cpap requires a positive airway pressure.
GeneS

If the liters per minute leak rate is low enough, you may not lose enough pressure to make the therapy ineffective, but the airflow will disturb you and it will dry out your nose and mouth. Even a small mouth leak the machine can easily handle will leave me with dry mouth and nasal passages, even with humidity.

Archangle
I agree a small leak is different than mouth breathing with cpap. A machine may be able to compensate for a small leak but I do not think it is possible for it to compensate for mouth breathing with cpap.
GeneS

I think even doctors and DMEs now realize that mouth leaks are a problem.

Archangle
I agree that mouth breathing and leaks are better understood now than when I started in 1985. Cpap was still an experiment then. I do not think that the DME's and Doctors understood cpap and treatment then. I am just glad that Dr. Sullivan invented cpap and that Respironics came out with a cpap in 1985. I know that they had a number of patent disputes later on but we have been fortunate to always have cpap when we needed it.
GeneS

[archangle]

I agree that mouth breathing and leaks are better understood now than when I started in 1985. Cpap was still an experiment then. I do not think that the DME's and Doctors understood cpap and treatment then. I am just glad that Dr. Sullivan invented cpap and that Respironics came out with a cpap in 1985. I know that they had a number of patent disputes later on but we have been fortunate to always have cpap when we needed it.
GeneS

Some of us are still learning. Unfortunately, a lot of doctors aren't trying to learn, they think they're gods and aren't really trying to learn. A lot of them are also still stuck in the medieval days of dataless CPAP machines and don't use the very valuable data a modern CPAP machine provides.

[genes]

Some of us are still learning. Unfortunately, a lot of doctors aren't trying to learn, they think they're gods and aren't really trying to learn. A lot of them are also still stuck in the medieval days of dataless CPAP machines and don't use the very valuable data a modern CPAP machine provides.

[/quote]

Archangle
I am still learning too. I went years without a data capable machine. The early machines either did not adjust or had knobs or other ways to change pressures. I adjusted my pressure by how I felt during the day and based on comments my wife said about my sleeping( like elbowing me in the side when I snored or had apnea's while using cpap) . I was lucky enough to get the codes for the electronic cpaps so I adjusted them the same way. The newer data capable cpaps are great. They let us fine tune our treatment and can save thousands of dollars on tests. It is hard (not really) to understand how it is ok to spend so much on sleep tests, doctors, etc. and then cut corners on the most important items. The Cpap machines and masks. It is also hard to understand how it is ok that 90% or so of people with sleep apnea go untreated. Smart machines could help reach more people also. I was lucky because my doctor would let me get whatever cpap that I wanted but I usually had to pay cash for it. If we could show the doctors that smart cpaps would save money without reducing their fees they might promote smart machines.
GeneS