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General Discussion on any topic relating to CPAP and/or Sleep Apnea.
NCHawk
 
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Bad mask fit and low ANI?

Postby NCHawk on Mon Feb 20, 2012 9:13 am

For the last month or so I've noticed something strange with my CPAP readings. Every so often when I check the info reading in the morning it will show a "bad mask fit" but also a low AHI. I use Sleepyhead, but don't check the readings every day and when I do I can't always remember which days this happened so I haven't been able to verify if there's any correlation between the bad mask fit and things like leakages.

Would a bad mask fit affect the AHI reading? Is there anything I should be looking for in the Sleepyhead graphs (some of which I'm not sure I understand anyway) to figure out what's going on?

Mary Z
 
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Re: Bad mask fit and low ANI?

Postby Mary Z on Mon Feb 20, 2012 9:18 am

Sorry, don't have any definitive answers for you, but I understand AHI readings are affected by large mask leakage. If Your AHI is consistently low, maybe not so much.
I would hope you could find a mask that fits well, though.

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Mask: Wisp Nasal CPAP Mask with Headgear - Fit Pack
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Additional Comments: PR System One Remstar BiPap Auto AS Advanced.
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Pugsy
 
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Re: Bad mask fit and low ANI?

Postby Pugsy on Mon Feb 20, 2012 10:32 am

NCHawk wrote:Would a bad mask fit affect the AHI reading? Is there anything I should be looking for in the Sleepyhead graphs (some of which I'm not sure I understand anyway) to figure out what's going on?


If mask fit and associated leak were really bad it is possible that the machine can't sense the events that might be happening and possibly give you a false low AHI. It all depends on how bad the leak and did it affect the scoring capabilities of the machine.

For S9 Resmed machines...using SleepyHead what you see on the leak graph is all excess leak because ResMed machines already subtract the intentional venting for the mask...so look at the leak graph and the leak line ......see how much of the time is spent at, near or above the 24 L/min line...that is where ResMed says that the leaks can impact therapy and the machines scoring ability.

If minimal time is spent at or above 24 L/min...then you can probably rely on the AHI number you see but if you spend a large amount of time in large leak territory then the time there may not reflect true event reporting and thus possibly would affect overall AHI. Short lived spikes to that 24 L/min line aren't the end of the world but if you spend half the night there...then yeah, it could impact your data and it may be missing some events.

I had a large leak the other night but it was 30 minutes out of 8 1/2 hours. Not the end of the world but more than I would want to see and that much leak is unusual for me. 30 minutes of possibly lost data isn't going to impact the overall AHI hugely. Now if it had been 3 hours...yeah.

So look at the leak line itself and eyeball how much time is spent close to or above that 24 L/min line and you will have an indication as to how much you can rely on the data that is shown.

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Machine: PR System One REMStar 60 Series BiPAP Auto with Bi-Flex
Mask: AirFit™ P10 For Her Nasal Pillow CPAP Mask with Headgear
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robysue
 
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Re: Bad mask fit and low ANI?

Postby robysue on Mon Feb 20, 2012 2:15 pm

NCHawk wrote:For the last month or so I've noticed something strange with my CPAP readings. Every so often when I check the info reading in the morning it will show a "bad mask fit" but also a low AHI. I use Sleepyhead, but don't check the readings every day and when I do I can't always remember which days this happened so I haven't been able to verify if there's any correlation between the bad mask fit and things like leakages.
By "bad mask fit", do you mean Mr. Red Frowny Face is paying you a visit in the short version of the Sleep Quality Report when you check the S9's LCD in the morning?

If so, then you need to understand the meaning of Mr. Red Frowny Face's appearance. He shows up on the short Sleep Quality report when your 70% leak rate is AT or ABOVE 24 L/min. In other words, Mr. Red Frowny Face only shows up when your unintentional leak rate is AT or ABOVE 24 L/min for at least 30% of the night. This is when the Resmed engineers believe both the SIZE and overall LENGTH of the unintentional leaks are LARGE enough to adversely affect both your therapy and your data.

To give you an idea of just how bad the leaks have to be to get Mr. Red Frowny to show up in the morning, consider this: 30% of one hour is 18 minutes. If you sleep 7 hours, that means that you have to have 126 minutes (just over 2 hours) of leaks above 24 L/min for Mr. Red Frowny Face to show up.

So, yes, there is a most definite correlation between Mr. Red Frowny Face and leakages. Look at your SH data. Find days where your leak line is frequently above 24 L/min or is above 24 L/min for extended periods of time or both. Those are the days where Mr. Red Frowny Face was likely to show up.

And why this has just started to happen intermittently in the last month or so?

Possible culprits: Is the mask cushion beginning to deteriorate? Are you doing some significant mouth breathing on some nights? Spring allergies kick in yet? That could induce the mouth breathing. Are you sleeping in a very different position some nights? Was the hose (and mask) properly assembled on those nights? Any chance the humidifier cover was not completely clicked shut?

Would a bad mask fit affect the AHI reading? Is there anything I should be looking for in the Sleepyhead graphs (some of which I'm not sure I understand anyway) to figure out what's going on?

Yes Mr. Red Frowny Face affects the AHI reading: Resmed engineers have set the threshold for Mr. Red Frowny Face's visits at the level where they believe leaks are a SERIOUS issue that indicate that both your therapy and your data could be compromised. That means:

1) The leaks are high enough that the machine may not be able to detect events correctly. Hence the reported AHI number may be lower than it actually is.

2) The leaks are high enough that the machine may not be able to effectively maintain enough pressure in your airway to keep it from collapsing. Hence you may be having more (possibly many more) events that you usually have with therapy.

Looking at the data in SH will let you determine whether the problem on a given night is one or more very long and large leaks or whether the problem is caused by very, very numerous but short-lived large leaks. But beyond that I'm not sure what else the leak line will tell you about the problem.

My advice? Treat a visit from Mr. Red Frowny Face seriously. When you see him, make a written note so you DON'T loose track of the dates he shows up. Make any additional notes about your impression of the night while it is fresh in your mind: Did you wake up? A lot or a little? Any evidence you took your mask off in your sleep? Did you wake up with a dry mouth--either in the morning or during some time in the night? Did the spouse say you were snoring? Does the spouse remember any weird noises coming from your mouth or your mask? Did you reassemble the equipment that day? Did you swap the hose or mask cushion out for a different one? Use the leak line data in SH to figure out WHEN you had the large leak and how long it lasted. And try to correlate what you see in SH with your written impressions about what went bump in the night: One really long large leak with a vague memory of either taking the mask off or waking up without the mask indicates one problem; dozens of minute or two long large leaks with a vague memory of fighting "face farts" most of the night indicates another problem; and waking up with a dry mouth or the wife reporting weird noises points to a third kind of problem.

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NCHawk
 
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Re: Bad mask fit and low ANI?

Postby NCHawk on Tue Feb 21, 2012 9:29 am

robysue wrote:
NCHawk wrote:For the last month or so I've noticed something strange with my CPAP readings. Every so often when I check the info reading in the morning it will show a "bad mask fit" but also a low AHI. I use Sleepyhead, but don't check the readings every day and when I do I can't always remember which days this happened so I haven't been able to verify if there's any correlation between the bad mask fit and things like leakages.
By "bad mask fit", do you mean Mr. Red Frowny Face is paying you a visit in the short version of the Sleep Quality Report when you check the S9's LCD in the morning?

If so, then you need to understand the meaning of Mr. Red Frowny Face's appearance. He shows up on the short Sleep Quality report when your 70% leak rate is AT or ABOVE 24 L/min. In other words, Mr. Red Frowny Face only shows up when your unintentional leak rate is AT or ABOVE 24 L/min for at least 30% of the night. This is when the Resmed engineers believe both the SIZE and overall LENGTH of the unintentional leaks are LARGE enough to adversely affect both your therapy and your data.

To give you an idea of just how bad the leaks have to be to get Mr. Red Frowny to show up in the morning, consider this: 30% of one hour is 18 minutes. If you sleep 7 hours, that means that you have to have 126 minutes (just over 2 hours) of leaks above 24 L/min for Mr. Red Frowny Face to show up.

So, yes, there is a most definite correlation between Mr. Red Frowny Face and leakages. Look at your SH data. Find days where your leak line is frequently above 24 L/min or is above 24 L/min for extended periods of time or both. Those are the days where Mr. Red Frowny Face was likely to show up.

And why this has just started to happen intermittently in the last month or so?

Possible culprits: Is the mask cushion beginning to deteriorate? Are you doing some significant mouth breathing on some nights? Spring allergies kick in yet? That could induce the mouth breathing. Are you sleeping in a very different position some nights? Was the hose (and mask) properly assembled on those nights? Any chance the humidifier cover was not completely clicked shut?

Would a bad mask fit affect the AHI reading? Is there anything I should be looking for in the Sleepyhead graphs (some of which I'm not sure I understand anyway) to figure out what's going on?

Yes Mr. Red Frowny Face affects the AHI reading: Resmed engineers have set the threshold for Mr. Red Frowny Face's visits at the level where they believe leaks are a SERIOUS issue that indicate that both your therapy and your data could be compromised. That means:

1) The leaks are high enough that the machine may not be able to detect events correctly. Hence the reported AHI number may be lower than it actually is.

2) The leaks are high enough that the machine may not be able to effectively maintain enough pressure in your airway to keep it from collapsing. Hence you may be having more (possibly many more) events that you usually have with therapy.

Looking at the data in SH will let you determine whether the problem on a given night is one or more very long and large leaks or whether the problem is caused by very, very numerous but short-lived large leaks. But beyond that I'm not sure what else the leak line will tell you about the problem.

My advice? Treat a visit from Mr. Red Frowny Face seriously. When you see him, make a written note so you DON'T loose track of the dates he shows up. Make any additional notes about your impression of the night while it is fresh in your mind: Did you wake up? A lot or a little? Any evidence you took your mask off in your sleep? Did you wake up with a dry mouth--either in the morning or during some time in the night? Did the spouse say you were snoring? Does the spouse remember any weird noises coming from your mouth or your mask? Did you reassemble the equipment that day? Did you swap the hose or mask cushion out for a different one? Use the leak line data in SH to figure out WHEN you had the large leak and how long it lasted. And try to correlate what you see in SH with your written impressions about what went bump in the night: One really long large leak with a vague memory of either taking the mask off or waking up without the mask indicates one problem; dozens of minute or two long large leaks with a vague memory of fighting "face farts" most of the night indicates another problem; and waking up with a dry mouth or the wife reporting weird noises points to a third kind of problem.


One thing that did occur to me yesterday evening is that it's been a while since I changed my pillows, which I'm going to do today, and that may have been a contributing factor. Of course, ever since I realized that I had been getting Mr. Red Frowny Face after a long stretch of not getting him I haven't seen him, but I will make a point in the future of taking the time to jot down any of the things you mentioned. So far I've never taken my mask off in my sleep, so that couldn't be an issue. I don't have a wife who could tell me about snoring or other weird noises; I suppose I could try asking my cats, but I suspect they wouldn't be much help. I do occasionally wake up with dry mouth, but haven't noticed any correlation bewtween that and any other problems.

Thanks for the help. I've only had my S9 for about a year now, and I'm still getting used to the idea of having access to any information other than how many hours I slept.


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