Should mask leak cause increased pressure?

[serabeth]

This might be a weird question, but if I purposely loosen a strap to the point where I have a leak, would this cause my auto cpap machine to increase the pressure?

I had about 4 or 5 days in a row where I seemed to be having issues with mask leak where the pressure on my auto cpap would fairly rapidly increase to the maximum setting.

Then suddenly, I had an entire week where the pressure just stayed at the minimum and did not increase. I was curious as to whether I could get it to increase again by purposely inducing a mask leak, and I was unable to do so.

Is this normal, or should I be calling my DME to check the machine? I’ve only had it for slightly over a month now.

[LSAT]

Yes..it's normal. It's the only way to compensate for the leak. Your profile says you are using an Auto machine, but it also says you are using fixed pressure at 11.

[serabeth]

Yes..it's normal. It's the only way to compensate for the leak. Your profile says you are using an Auto machine, but it also says you are using fixed pressure at 11.

I’ll update that. It should say 11-16 for my pressure settings.

[Pugsy]

You need to understand increasing pressure and increasing flow rate (air movement)...not necessarily the same thing.


Over simplification example....if your pressure setting was fixed 5 cm...the machine won't/can't increase the pressure to 10 cm to try to compensate for a big leak. It won't change the pressure itself. Now it may increase the air flow a little to try to keep that 5 cm pressure steady. In the face of some really big leaks some machines will actually back off on the pressure and you see a big drop in the pressure line during a big leak which is the machine's way of trying to maybe get things under control. Palerider has a good example of that...he will be around later and likely share it.

More air flow doesn't necessarily mean more pressure. They aren't the same thing.

[serabeth]

You need to understand increasing pressure and increasing flow rate (air movement)...not necessarily the same thing.


Over simplification example....if your pressure setting was fixed 5 cm...the machine won't/can't increase the pressure to 10 cm to try to compensate for a big leak. It won't change the pressure itself. Now it may increase the air flow a little to try to keep that 5 cm pressure steady. In the face of some really big leaks some machines will actually back off on the pressure and you see a big drop in the pressure line during a big leak which is the machine's way of trying to maybe get things under control. Palerider has a good example of that...he will be around later and likely share it.

More air flow doesn't necessarily mean more pressure. They aren't the same thing.

So it could just be that it increases the air flow to compensate for the leak and still maintains the pressure at 11? I wonder why it rapidly increased to 16 for 4 nights in a row then but won’t increase at all now. I guess maybe I was a bit more congested from allergies for those 4 days. But I have a full face mask and could breathe through my mouth instead of my nose as needed.

[Pugsy]

So it could just be that it increases the air flow to compensate for the leak and still maintains the pressure at 11?

Correct.

I wonder why it rapidly increased to 16 for 4 nights in a row then but won’t increase at all now. I guess maybe I was a bit more congested from allergies for those 4 days. But I have a full face mask and could breathe through my mouth instead of my nose as needed.

I think you just answered your own question....the machine increased the pressure to 16 (or whatever) because of flow reductions in your airway brought on by the allergy symptoms. That's what auto adjusting machine algorithms will do.
It can't know that the reduced airway air flow is in the nose from allergies...all it knows is the air in the airway isn't moving as much as it would like so it increases the pressure in an effort to help you open up the airway.

When you see the pressure line climb...the machine is fighting something it doesn't like going on in the airway.
If you happened to have a bit of a leak at the same time that's just a coincidence.

[serabeth]

I think you just answered your own question....the machine increased the pressure to 16 (or whatever) because of flow reductions in your airway brought on by the allergy symptoms. That's what auto adjusting machine algorithms will do.
It can't know that the reduced airway air flow is in the nose from allergies...all it knows is the air in the airway isn't moving as much as it would like so it increases the pressure in an effort to help you open up the airway.

When you see the pressure line climb...the machine is fighting something it doesn't like going on in the airway.
If you happened to have a bit of a leak at the same time that's just a coincidence.

Thanks! I appreciate your replies! I tried asking my doctor during my compliance appointment, but she spoke to me in a whiny, condescending voice and refused to even acknowledge that I had issues with leak and that my pressure had increased to max because her summary page said I was fine. She eventually rolled her eyes and looked and saw that I did have high pressure and mask leak for several days but just shrugged and said she would see me in 6 months. The summary print out of my visit had no notes and she had not gone over the results of my sleep study with me =\.

She acted like I was incredibly stupid for purposely causing a leak in my mask to test if the pressure would increase and said no patient had ever done that before. If she’d just explained the air flow vs pressure like you did, I would’ve understood and not worried about it. I suspect she has no understanding of it herself to be honest .

Anyways, thanks again for the help!

[Pugsy]

I suspect she has no understanding of it herself to be honest .

She probably doesn't understand how the machine works and she isn't the first and won't be the last.
Unless someone actually uses this stuff and thinks things through..they don't have a clue how things really work.
It's not rocket science but it does take a bit of actual education and thinking to sort through this stuff.
Doctors aren't trained in the mechanics of things...only in the basics of diagnosis and the most basic treatment options...when something off happens they have no training to help them sort out what might be going on.

[palerider]

This might be a weird question, but if I purposely loosen a strap to the point where I have a leak, would this cause my auto cpap machine to increase the pressure?

NO, Never.

If the leak is bad enough, your machine will REDUCE pressure.

I had about 4 or 5 days in a row where I seemed to be having issues with mask leak where the pressure on my auto cpap would fairly rapidly increase to the maximum setting.

You've got it backwards... higher pressure causes more leak, not the other way around.

[palerider]

Yes..it's normal. It's the only way to compensate for the leak.

This is wrong.

The machine will increase the air FLOW in order to maintain the air pressure, up to a point, at which time the machine will drop the pressure in order to try and get the mask to seal.

Auto machines *NEVER* increase pressure in response to leaks, that would be stupid, more pressure would just make the leaks *worse*.

[palerider]

I wonder why it rapidly increased to 16 for 4 nights in a row then but won’t increase at all now. I guess maybe I was a bit more congested from allergies for those 4 days. But I have a full face mask and could breathe through my mouth instead of my nose as needed.

You'd have to look at the sleepyhead data and see what was going on.

There's always a reason, flow limitations, snores, hypopneas, apneas. those are the *only* reason that pressure increases.

[serabeth]

You'd have to look at the sleepyhead data and see what was going on.

There's always a reason, flow limitations, snores, hypopneas, apneas. those are the *only* reason that pressure increases.

Thank you for the info! I assume if your airway clears up that it adjusts back down too? My app always says my 90% pressure is 12 but whenever I check, it’s 11. Maybe because I need less pressure when I’m awake so it adjusts back down.

[Pugsy]

90/95 % numbers of anything just mean you were at OR BELOW that number for 90/95 % of the night.
The or below part of the definition is often overlooked and people tend to think it's where we spent 90/95% of the night and nothing is further from the truth.
90/95% numbers are just numbers that don't really mean much despite everyone wanting them to mean something.
They are easily skewed upwards by a relatively brief excursion higher.

[serabeth]

90/95 % numbers of anything just mean you were at OR BELOW that number for 90/95 % of the night.
The or below part of the definition is often overlooked and people tend to think it's where we spent 90/95% of the night and nothing is further from the truth.
90/95% numbers are just numbers that don't really mean much despite everyone wanting them to mean something.
They are easily skewed upwards by a relatively brief excursion higher.

Oh, I assumed it meant I was at 12 90% of the time. Thanks! I need to just go to sleep and stop obsessing over whether my machine is working properly, I think lol. I keep getting concerned over nothing . I was afraid it wasn’t working because I was tired this morning, but that could’ve been because I had to wake up at 7 am for my appointment when I usually get up at 9:15 am for work. I have to get up early tomorrow too ugh .

[palerider]

You'd have to look at the sleepyhead data and see what was going on.

There's always a reason, flow limitations, snores, hypopneas, apneas. those are the *only* reason that pressure increases.

Thank you for the info! I assume if your airway clears up that it adjusts back down too? My app always says my 90% pressure is 12 but whenever I check, it’s 11. Maybe because I need less pressure when I’m awake so it adjusts back down.

The 90% number is meaningless, other than as an arbitrary statistic.

Get sleepyhead, and look at what the pressure did throughout the night.

And, yes, shortly after whatever breathing issues you're having settle down, the machines start drifting the pressure slowly back down to whatever the minimum set pressure is... (which is why getting the min pressure set right is the most important thing about an auto machine... if the min pressure is too low, you'll spend the night in a cycle of event, pressure raise, pressure drop, event... over and over.