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Confused about AHI results
08-11-2015, 12:55 PM
My experience is that flow limitations are a precursor but not necessarily every time. So, if you have OAs with no precursors the machine will only respond to the OAs and not as aggressively as it does to flow limitations. If this happens consistently, you might want to consider CPAP mode.
Exactly right PatonA. I have seen that on another family members graphs. He was on cpap and I had him try apap to see if he could get by with less pressure than he was using with cpap. His condition worsened according to the read-outs, and he was happy to return to cpap and tell me to quit trying to help him.
I have zoomed in on the OA's that I feel are improperly flagged and they seem to be legitimate 10 and 14 second interruptions. Even so, I still find it hard to believe that I pause breathing for 14 secs. while wide awake and well aware of my breathing, yet not realize it. I see no gasp afterwards or increased breathing rate either. Also noted that the pressure didn't increase on the first couple of those OA's but did later when the next six of them occurred somewhat closer together. It's like the machine didn't believe it either.
I'll ignore them and hope the machine does better when I'm asleep. edit: And may consider cpap for myself!
08-11-2015, 03:24 PM
Dude and Payton:
Very interesting thoughts, indeed -- my in-lab sleep study was done in CPAP mode, ultimately titrating to 11 cmH2O and EPR of 2 cmH2O, at which settings I had no OSAs, Hs or CAs. I've been on APAP since starting therapy 2 months ago. I've experimented with different settings, gradually increasing the lower setting from 7 to my current setting of 9, and increasing the upper limit from 11 to my current setting of 13.4. I've also had EPR off and now have it back on at 2 cmH2O.
I am curious whether a fixed CPAP pressure of 11 and EPR of 2 may provide better therapy results. I hate to mess things up (except for my early morning CAs, I now seem to have adjusted well to therapy and am getting decent results), but curiosity may prevail.
08-11-2015, 04:53 PM
Well, this is beginning to look like there is another tinkerer in the crowd. Gee, I never mess with things when they are going well (that would be a big fat lie) Some of us just can not resist.
My motto is, "You'll never know if you don't try." With that in mind, I always leave a trail of bread crumbs so I'll have an even bigger mess to clean up later.
As for setting a proper minimum cpap pressure to get better therapy than using an apap with a range of pressures, the correct answer is, "It depends." I'll be happy to confuse you on that issue.
Consider a case using an apap where the anatomy of your throat is such that there is a flap hanging there that offers very little resistance to air flow until it approaches a certain position in relationship to the unique shaped air passage that is is capable of blocking. When it reaches that position, it snaps forward (imagine a check valve) and seals off the air flow completely. Now you can imagine that it could likely take less pressure to keep it from encroaching into that critical position so having a standing minimum pressure could be the key to preventing the closure from happening. This could be defined as a "No warning type" of event that could not be anticipated by the software and would occur in a split second, well before the pressure could ramp up. If that repeated itself several times over a period of 10 minutes, the pressure would finally get ramped up enough (due solely to the events being flagged) to handle the circumstances. Unfortunately you have registered approximately 5 OA's before it got control. Then lets imagine that all that pressure increase woke you up. That could start the entire process over. You can easily imagine that having a proper minimum standing pressure could have prevented all this bothersome activity.
On the other hand, if you have a gradually decreasing air flow (imagine a slowly closing gate valve) due to the relaxing of the airway, which we could call an "Early warning" type, then a properly set apap will ramp up in time to prevent any bothersome activity and prevent any OA's from being flagged. That assumes you had the minimum set close to the needed level so it could rise to the occasion rapidly.
So there you have it, it depends on what type of restriction you have and how tolerant you are to pressure changes. Does the door slam shut or is it closing slowly? What's best for one person may be worse for someone else. We're all different, except me, I'm indifferent.
That's just one example, there are other scenarios that can give the same results. This is my short answer. You don't want to hear my long answer.
HTH (since it wore me out)
08-11-2015, 06:53 PM
i'm going to mull this over for a bit. I usually subscribe to the "if it ain't broke, don't fix it" viewpoint, but on the efficacy of apnea therapy I'd like to do better than just OK. I might experiment a little to see what happens.
Thanks guys -- I appreciate your thoughts!
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