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High leak rate but relatively lower AHI - bettis1 - 03-21-2015
I have been using my CPAP for approx. 4 months. Initially my pressure was set at 9, then 10, then 12, and now 14 for the last month. I began using a Mirage Liberty, then a Mirage Quattro but my AHI remained in the high 20-30 range and my 90% leak rate was usually below 20 and often in single digits. Neither of those masks were comfortable to me.
When my doc raised my pressure to 14 I began to use an F&P Simplus mask. That mask is much more comfortable to me and my AHI has been in the 3-7 range. However, my 90% leak rate is in the 40-50 range.
The Simplus seems to have a good seal around the edge and the only air flow that I can feel is the escape from the panel of holes in the front. These holes have no valve and part of the input air escapes there whether I am breathing or not.
My vendor told me that some masks normally have a higher leak rate than others. Is this normal with the Simplus?
If that is the case, it would seem that there should be some adjustment to the software to take that into consideration.
Thanks,
Bob
RE: High leak rate but relatively lower AHI - Sleepster - 03-21-2015
Hi bettis. Yes, there is a way to account for the differences in leak rates of the masks. You select the mask type on the machine's menu.
To really figure this out you need to look at the leak graph. If there are extended periods of time when the leak rate is elevated, those are times when the mask is leaking. These times could interfere with the quality of your sleep in two ways. The machine may not be able to maintain enough pressure and your airway collapses causing an apnea, hypopnea, or flow limitation. Even if this is not occurring, the leak could be waking you up.
The Simplus mask comes in three sizes, so you may need a different size. Also, try lowering the mask a bit. Don't let it ride too high on the bridge of your nose. I lower mine so that its bottom just laps over my chin.
RE: High leak rate but relatively lower AHI - Nyre - 03-21-2015
Hello and welcome to the board. Lots of great info and advice is given here. I'm not familiar with your machine. Is it data capable? If so have you thought about using the software sleepyhead? A lot of detailed information can be gathered from its reports and give you a good look at your treatment.
RE: High leak rate but relatively lower AHI - trish6hundred - 03-21-2015
Hi bettis1,
WELCOME! to the forum.!
Much success to you as you continue your CPAP therapy and good luck in finding a mask that works well for you.
RE: High leak rate but relatively lower AHI - bettis1 - 03-21-2015
Thanks, Sleepster. I appreciate the info. I am using the medium Simplus and I believe that is the correct size for me. It comes to the bottom of the fold in my chin and I believe that the large would be too long. I will try to move mine down some tonight.
I will dig deeper into the machine menu tomorrow and see what adjustments I can make to the leak.
Nyre, yes, I have been using Sleepyhead since I started and have found it to be very helpful. I am still learning more and more about interpreting the data. Interestingly, neither my sleep doc nor my vendor were aware of the software and both were surprised at the amount of information that I questioned them about. Neither of them are particularly helpful and seem most interested in moving on to the next awaiting patient. I have resigned myself to learning this thing myself, with the help of this Forum.
I had a private dental practice for 40 years and then taught in a dental school for 10 years after I retired from private practice so I am very familiar with the respiratory mechanism. I'm just learning the nuts and bolts of this apparatus and how to best utilize it. I'm also pretty attuned to practitioners who seem focused on goals other than patient care.
Bob
RE: High leak rate but relatively lower AHI - truetopath - 03-21-2015
Unfortunately, it's simply a business for too many of the sleep docs and DME's out there. I wish you the best of luck with your cpap therapy.
RE: High leak rate but relatively lower AHI - Terry - 03-21-2015
(03-21-2015, 04:26 PM)bettis1 Wrote: My vendor told me that some masks normally have a higher leak rate than others. Is this normal with the Simplus?
If that is the case, it would seem that there should be some adjustment to the software to take that into consideration.
There are two kinds of leaks: "Intentional leak" and "Everything else" 8-)
All masks have an air-bleed hole to exhaust air from the hose and mask. This is how you get fresh air: regardless of how you're breathing, the machine's blower sucks up air, blows it down the hose and a percentage goes out the air-bleed hole.
If the hole was plugged, you wouldn't be getting any fresh air or oxygen and it would get very "exciting" very quickly. Intentional leaks are good.
The intentional leak rate is described in the brochure that came with the mask and varies according to your machine's pressure, but you really don't need to be concerned with it, except that at very low pressures (~4), some masks don't ventilate enough fresh air. As long as the only leaks are where they should be, everything will be just fine.
The other leaks are from the mask not sealing well against your face. These are annoying because the make the humidifier use water faster and not work as well, and if they're bad enough, prevent your machine from being able to tell what kind of events you're having and respond to them.
If you're not getting any/much mask leakage, you can pretty much ignore the intentional leak. If should be just fine.
You can tell what kind of leak you have by finding the leak rate and pressure at any given time, in sleepyhead and comparing it to the chart that came with your mask. If you're leaking a lot more than the chart indicates, you have a problem with fit, or possibly your mouth is opening.
You can sometimes tell what kind of leak you have by how you feel. If your mouth and throat feel like they've been stuffed full of toilet paper, you're probably opening your mouth. If not, it's probably leaking out around the mask somewhere.
Terry
RE: High leak rate but relatively lower AHI - bettis1 - 03-22-2015
Thanks for that information, Terry. If I am reading the Simplus info graph right, my max exhaust flow should be somewhere around 41 for my pressure of 14 cm H2O. Last night was a relatively good one with an AHI of 2.43 and a 90% leak rate of 27. The night before was less satisfactory with an AHI of 5.2 and a 90% leak rate of 46.
Sleepster, I couldn't keep my medium mask at the bottom of my chin without the top closing off my nostrils so I will see about getting a large version to try tomorrow.
Thanks to all for your assistance. I'm in the "two steps forward-one step back" phase but overall, I am very pleased with the improvement in my sleep…and that is the goal!
Bob
RE: High leak rate but relatively lower AHI - swaziman - 03-23-2015
I found that I reduced my leaks by tightening the mask on my face. I know popular feeling is that the mask creates its own seal and doesn't need to be tight, but I disagree. My face relaxes during the night, the mask warms up, sweat makes it slippery and the result is major leaks.
RE: High leak rate but relatively lower AHI - bettis1 - 03-23-2015
Thanks swaziman. I've also noticed that my leaks seem to increase after I have been asleep for several hours. I attribute that to the relaxation of the facial tissues and their response to the pressure of the mask over time.
Many of the mask manufacturers counsel us not to tighten the mask "too tight". That is a pretty indefinite suggestion and I'm sure that "just right" (like the Three Bear's porridge) is an individual determination.
Bob