WHAT'S THE IMPORTANCE OF LEAK RATE?

[Spottymaldoon]

Having finally got my Encore Pro to work, I want to ask a couple of questions about leak rate.

If there is a good explanation of this already to be found, please could somebody point me in the right direction?

Otherwise, I shall ask:

(1) What is the importance of leak rate and what causes it to change?

(2) If I use a nose-mask and open my mouth, one of two things happens: (a) my nose is pressurized and I breathe quite normally through my mouth alone (b) I seem to breathe through my nose and air leaks out of my mouth!
Question here is how does APAP respond to (a) and to (b)?
Can (a) or (b) be identified in Encore analysis, by looking at the data?

(3) On my RemstarAuto M series I click the 'go left' button twice and see a parameter "System leak" which displays a very low number ..around 4 to 8 L/min but this is clearly not the same as the 'leak rate' reported in Encore for the same night. What is this?

best,
Spotty

[bdp522]

For #1; leak rate is important because that's how you tell if your having leaks. Leaks mean you are not getting optimal treatment. You need to get leaks under control to get effective therapy.

for #2; A cpap will raise the pressure slightly to accomodate small leaks(it trys to maintain the set pressure). I'm not sure how the apap handles it. I do know that if it is a large leak the machine will shut off after a while. The encore data will show this in the graph. You will see the line go to the amout of leak.

for #3; Don't have an M, can't even guess at it.

If you are mouth breathing you need a full face mask or you need to tape your mouth shut.

I'm sure some of the more knowledgable members will be by shortly to give more complete answers.

Brenda

[Bearded_One]

A cpap will raise the pressure slightly to accomodate small leaks(it trys to maintain the set pressure). I'm not sure how the apap handles it.

A CPAP does not raise the pressure, a CPAP machine attempts to maintain the constant prescribed pressure. A CPAP increases the airflow to compensate for leakage.

An APAP responds in the same way as a CPAP, the difference is that the pressure for an APAP is dynamic rather than constant.

xPAP machines can deal with minor leaks without a problem,

[dsm]

Leak rate is the amount of air designed to escpae from your particular mask. All masks (except some special ones) need to leak an amount of air to clear the excess CO2 that builds up.

At 10 CMS a given mask will have a particular leak rate, at 11CMS the extra pressure means a bit more air will exit through the exhaust vents used to leak the air, and so on ...

Most masks come with a fixed leak-rate chart showing the actual fixed leak for a particular CMS pressure.

Some cpap machines allow you to enter a mask type (usually their own brand) and thus the nightly data from that brand should if there is a good mask seal, show zero leak for the night in the nightly detailed data.

Some other brands don't have these internal tables & thus when you look at your nightly data you see a nightly leak rate & have to deduct the fixed leak rate for the CMS in question for the mask in question, from the nightly leak rate in order to deduce any actual accidental leak vs the fixed leak.

For myself, irrespective of what machine I actually use, I do find it very convenient when the software for the particular brand, shows only accidental leak in the nightly data charts. Saves me messing around trying to work it out.

DSM

[dataq1]

Incidentially, My DME told me that my encore pro data showed that I had a leak rate that indicated that the mask seal was very poor. As I recall the leak was somewhere about 37-40l/min. I knew that the mask wasn't leaking, but could not convince the RT at my DME. The RT called my doctor to request a script to purchase a different mask. I told my doc, no leaks as far as I could tell.
Eventually I called Respironics and talked with their tech people. They confirmed that the leak shown in respironics Encore Pro was the total leak, including the air passing thru the exhalation ports. I called the RT, she still didn't believe me, so I got the Respironics tech service and the RT on conference call. Finally she was persuaded.
Sometimes you just have to educate the "experts"... particularly when they are looking for another sale!
Good Luck, and very good questions!

[Goofproof]

bdp522, is right on, If you use a Nasal interface and the pressure isn't sealed by your mouth you can be loosing the pressure need to keep your airway open, Lots of people tape or seal their lips, some use FF Masks that cover the mouth and nose.

Chin straps usually are useless. The machine trys to cover the leak but it's like trying to air a flat tire, the seal has to be there before it will inflate. Jim

[NightHawkeye]

(1) What is the importance of leak rate and what causes it to change?

(2) If I use a nose-mask and open my mouth, one of two things happens: (a) my nose is pressurized and I breathe quite normally through my mouth alone (b) I seem to breathe through my nose and air leaks out of my mouth!
Question here is how does APAP respond to (a) and to (b)?
Can (a) or (b) be identified in Encore analysis, by looking at the data?

My experience with mouth breathing has been that the Remstar APAP I use does compensate effectively for it. In my case, your description b) applies with the mouth breathing not really breathing, but like air escaping through the mouth at a small rate. In fact, the leak rate is small enough that I rarely even have dry mouth from it. The Encore Pro data does show the leak rate going up and down a lot through the night, but only shows a large leak occasionally every few nights. I also believe that my mouth leak is largely from air returning from the stomach.

If I could use a full-face mask I might get a little better therapy, but FFM's and I aren't compatible. Consequently, I stick with nasal masks and get pretty effective therapy anyway.

Just my experience, of course. Your mileage will differ.

Regards,
Bill

[Spottymaldoon]

Thanks for the responses. My take out is that leakage is literally what it implies - all the air that doesn't remain in the system - intentional leakage from the couplings and mask vent, leakage from a poor face seal and (even) mouth leakage with a nose mask.

I also take out that leakage isn't bad so long as (a) it is not enough to cause the pressure to fall significantly and (b) so long as you are not disturbed by it.

With mouth leakage, anatomically, I think this is passage of air from the pharynx to the mouth and don't you think that would cause the pressure in the pharynx to drop - the reverse of what xPAP is meant to do?

Also, with a nose mask, if you breathe through your mouth and your nose is still fully pressurized, wouldn't the machine take this to mean you have stopped breathing, raise the pressure and register a major apnea?

Encore seems to put a lot of stress on leakage so I wondered if it meant something other than the above, many thanks.

Spotty

[dsm]

[quote="Spottymaldoon"]Thanks for the responses. My take out is that leakage is literally what it implies - all the air that doesn't remain in the system - intentional leakage from the couplings and mask vent, leakage from a poor face seal and (even) mouth leakage with a nose mask.

I also take out that leakage isn't bad so long as (a) it is not enough to cause the pressure to fall significantly and (b) so long as you are not disturbed by it.

With mouth leakage, anatomically, I think this is passage of air from the pharynx to the mouth and don't you think that would cause the pressure in the pharynx to drop - the reverse of what xPAP is meant to do?

Also, with a nose mask, if you breathe through your mouth and your nose is still fully pressurized, wouldn't the machine take this to mean you have stopped breathing, raise the pressure and register a major apnea?

Encore seems to put a lot of stress on leakage so I wondered if it meant something other than the above, many thanks.

Spotty

[REMmaster]

[quote="Spottymaldoon"]Thanks for the responses. My take out is that leakage is literally what it implies - all the air that doesn't remain in the system - intentional leakage from the couplings and mask vent, leakage from a poor face seal and (even) mouth leakage with a nose mask.

I also take out that leakage isn't bad so long as (a) it is not enough to cause the pressure to fall significantly and (b) so long as you are not disturbed by it.

With mouth leakage, anatomically, I think this is passage of air from the pharynx to the mouth and don't you think that would cause the pressure in the pharynx to drop - the reverse of what xPAP is meant to do?

Also, with a nose mask, if you breathe through your mouth and your nose is still fully pressurized, wouldn't the machine take this to mean you have stopped breathing, raise the pressure and register a major apnea?

Encore seems to put a lot of stress on leakage so I wondered if it meant something other than the above, many thanks.

Spotty

[xzombie]

So how do I find the automatic leak rate for my mask. I don't recall getting any manuals with that. I actually have 2 - Ultra mirage II and Activa (both nasal).

[bdp522]

First, Thankyou Bearded one for correcting my error.

Second, look here for leak rates;
http://www.internetage.com/cpapinfo/leak-rates-1.html


Brenda

[NightHawkeye]

My take out is that leakage is literally what it implies - all the air that doesn't remain in the system - intentional leakage from the couplings and mask vent, leakage from a poor face seal and (even) mouth leakage with a nose mask.

Absolutely correct.

I also take out that leakage isn't bad so long as (a) it is not enough to cause the pressure to fall significantly and (b) so long as you are not disturbed by it.

Also correct. Interestingly, Respironics software even hides large constant leaks from the Encore Pro display. The machine still records the leakage but but if it's constant, then it's assumed to be mask leakage, I suppose, and Encore Pro simply subtracts it out without displaying the value. I found this out by accident one night when I discovered a big difference between the leak values displayed in MyEncore and Encore Pro. It was only after I became curious about the anomaly that I discovered that my machine and humidifier were not properly connected. A large volume of air had been escaping at the coupling junction.

So, even if you have minor leakage through your mouth the machine can still provide adequate therapy. Various descriptors have been used to describe these minor mouth leaks, such as: "mouth leaks", "mouth puffs", "blowfish", etc. When that leak becomes a torrent, however, then therapy can be affected. Also, if a mouth leak occurs quickly, then therapy may also be compromised because the machine tends to responds slowly to leaks.

With mouth leakage, anatomically, I think this is passage of air from the pharynx to the mouth and don't you think that would cause the pressure in the pharynx to drop - the reverse of what xPAP is meant to do?

True in many cases. However, many folks, including myself, have experienced what appears to be air coming back up from the stomach rather than leaking directly from the nasal passages. It's unclear that such leakage has any real impact upon therapy. Both types of leakage can wake you up though, so at least in that respect they both can be detrimental to therapy.

Also, with a nose mask, if you breathe through your mouth and your nose is still fully pressurized, wouldn't the machine take this to mean you have stopped breathing, raise the pressure and register a major apnea?

What seems to happen with Respironics machines is that if the leak occurs quickly, the machine doesn't always respond to it. I've seen instances of oxygen desaturation in my oximeter data which occur at the beginning of leak indications in the Encore Pro data, but for which no indication of apneas or hypopneas is recorded. Instead of recording an apnea, the machine slowly raises the air flow to compensate for the leak, while also attempting to maintain constant pressure.

Encore seems to put a lot of stress on leakage so I wondered if it meant something other than the above . . .

Leakage can clearly be an important factor in therapy. In the early days of CPAP therapy (and for cheaper machines even now) the machines simply moved a constant volume of air. The machines included no provisions for measuring pressure. If there were no leaks, then the patient received constant therapy pressure and effective therapy. However, when leaks occurred, then the pressure dropped and therapy was compromised. Many of the better machines now directly measure air pressure and by doing so are able to compensate for leaks to some extent, but there are limits to the effectiveness of the compensation.

No doubt, manufacturers will continue to make improvements in this aspect of machine performance to benefit your therapy.

Regards,
Bill

[Spottymaldoon]

Again, thanks to all for their time and trouble giving responses. DSM I think we're saying the same thing but using different words.

NightHawkeye said:

However, many folks, including myself, have experienced what appears to be air coming back up from the stomach rather than leaking directly from the nasal passages.

I find this very interesting. May I ask why you think air is coming from the stomach? I assume this is a steady stream, rather than a 'burp' mechanism and, if so, that would imply the lower esophagal sphincter stays open (abnormal).

Now, I do find that after therapy I have a lot more gas in my abdomen than I had before I started - to the point of discomfort in fact. Displayed by burping and .. otherwise. Seems a logical outcome because only the epiglottis prevents pressurized air going to the stomach and any time you swallow you'll send in extra air.

I am sure this topic has come up before, if so, please direct me to any past threads rather than obliging me and boring others!

Best,
Spotty

[dsm]

Nighthawkeye did a good coverage (better than my sparse one )

One leak that comes back to haunt us is the air that escapes into our stomachs (usually as we breathout against the incoming pressure) & that then comes back as burtps or worse.

The burps can be reorded as snores

DSM