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[Pressure] tweaking pressures for Bilevel
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justMongo Offline

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Post: #11
RE: tweaking pressures for Bilevel
(01-31-2014 02:09 AM)robysue Wrote:  
(01-30-2014 04:51 PM)justMongo Wrote:  I am only able to read out my AHI and AI. (I have the custom data card and reader for the S8 -- but, cannot get things to play nice.)
My AHI exceeds 5. My AI is about 2.
The HI = AHI = AI, so if your AHI > 5 and your AI is around 2, then the HI is at 3 or higher.

Quote:So, I conclude that my Hypos are pushing my AHI above 5.
That's a reasonable conclusion. You might want to up just the IPAP by a cm or two and leave it there for a week or so to see what happens to the AHI and the AI (and hence the HI).

Quote:Looking at my 4 year old titration data, I showed occasional CA's at higher pressures. As I look at that data, I don't understand why they settled on 14/9. Other, than I think they were running out of time.

[Image: Titration_08AUG2009.jpg]
If you look at the data carefully, you will notice that 14/9 appears to be high enough to control the OAs and the Hs (the #OAs = 0 and #Hs = 0), although it looks as though you got mighty little sleep at that pressure setting. Above IPAP = 14 and EPAP = 9, you'll notice that the number of centrals grows with the pressures. That's probably why they didn't go with a higher pressure setting.

In my non-sleep professional, non-doctor view, I think the question to ask is why didn't they just go with a pressure setting of 13/6. Your sleep efficiency was good and there were no obstructive events in the 21 minutes at that pressure. Or perhaps 13/7 when you had 40 minutes of REM sleep with no obstructive events. (But there were 3 CAs in the 57 minutes at 13/7.)

Out of curiosity: Have you ever tried sleeping at 13/7 or 13/6 to see if the AHI goes down instead of up??


And by the way, those ridiculously high AHIs based on 1-3 CAs at pressures of 15/8, 15/10, 15/11, and 17/10 are based on ridiculously small amounts of sleep. For example, let's look at the AHI computation for 15/8. There's one CA scored at 15/8, but the reported AHI = 150. Here's how that number was computed:

According to the data, they had you at 15/8 for a whopping 3.8 minutes. And your sleep efficiency at 15/8 is reported as 10.5%. In other words, you were only asleep for 10.5% of the 3.8 minutes that the pressure was at 15/8. And 10.5% of 3.8 minutes is a grand total of 0.339 minutes, which equals 23.94 seconds. Let's round that to 24 seconds and note that 24 seconds = 0.4 minutes, and 0.4 minutes is 10.52% of 3.8 minutes. So it's likely that at a pressure setting of 15/8, you slept for a whopping 24 seconds. And in those 24 seconds you had one central apnea. Since AHI for 15/8 is equal to (# of events)/(Sleep time at 15/8 measured in [i]hours[/], we first have to convert the 24 seconds of sleep time to hours:

24 seconds = 24/60 minutes = 0.4 minutes = 0.4/60 hours = 0.00667 hours of sleep at 15/8 cm.

So the AHI at 15/8 is scored as:

(1 CA)/(0.00667 hours of sleep at 15/8) = 150.0 when rounded to one decimal place.

And finally, was this a split study? There are only 3 hours of time recorded in the pressure data. Did they have you sleep without the mask for the first part of the night and then wake you up to put the mask on your nose for the rest of the night?

Yes, this was a split night study. It took me quite some time to initiate sleep that night. When switched over to the titration phase, I think little time was left. For some reason, I did desaturate badly during REM sleep. Since my PSAO2 was low throughout the study, my Rx calls for 2 LPM O2 to be injected into my xPAP flow.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
01-31-2014 05:19 AM
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Sleepster Offline
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Post: #12
RE: tweaking pressures for Bilevel
I think you have a case you could argue with a doctor for a prescription for a newer machine that will record more data. You certainly need it to be able to evaluate your therapy. Of course, there would have to be significant complaints from the patient concerning lack of quality sleep and the like.

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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
01-31-2014 08:50 AM
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PaytonA Offline
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Post: #13
RE: tweaking pressures for Bilevel
(01-31-2014 02:24 AM)robysue Wrote:  
(01-30-2014 05:21 PM)PaytonA Wrote:  Mongo,

Looking over that titration data, I think that I would have selected 17/12 or 18/9
There was NO sleep recorded at either of these pressures. In fact there was NO sleep recorded at any pressure level at or above 17/12. That's why all those pressures have an AHI = 0.0.

Quote:It just makes sense to my brain that one should not pick pressures that gave zero events if subsequent higher pressures resulted in some events.
You have to get somesleep time for the AHI numbers to be meaningful. And it looks as though there was mighty little sleep scored after the pressures were raised past 15/8.

I sure did miss the fact that there was no sleep occurring at the higher pressures. I guess that it did not even cross my mind that a tech would proceed without any sleep occurring. Thanks for pointing that out.

PaytonA
01-31-2014 11:56 AM
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