(02-06-2015, 09:20 AM)Evie1 Wrote: ...My New Dr. said to put it on Auto Mode, 7 to 13, but woke up in the middle of the night and put it back down to straight 7 cm of pressure because I keep waking up. I then put Auto back on a tighter range a few days later ...
My AHI has always been in "normal limits" , Although the AHI for 4am to 6am ranges anywhere about 3 to 10 AHI. .... It seems to be only CA 's... I have been on auto mode for about 2 weeks so I figured that the CA's should have gone down by now. The CA's usually come around when pressures are at 7cm or 8 cm range at 4am to 6 am...
You seem like a bright person, so I think you will be able to figure this all out.
When I was 5-20, I had a couple nights where I got woken up when the pressure went to 18-20, and it seemed more like xPAP runaway than the machine responding properly to events (at least looking at it in SleepyHead) so I topped it off at 14 to prevent that, and it has not done it since. I have the same machine you have.
My sleep doc said "straight 8", which I tried for a while, then tinkered with 8-14 and then 10-14, and each change lowered AHI significantly (now 1.8) over the last 5 months.
The little graph that shows what pressure was when events are happening in SH (the lowest graph on the page) can be a little misleading, as it refers to exhalation pressure rather than inhalation pressure, so if you have EPR on, it subtracts that from the inhalation pressure (which is what the xPAP is set to). So if you have EPR on and set to 3, an event that happens at an inhalation pressure of 10 will register there as happening at a pressure of 7, so you have to make that leap to really know what pressure events are accumulating at. Kind of a gotcha, as one would expect such a graph to track the inhalation pressure that the xPAP is set to.
Another thing that I think is a good idea is that when you wake up, for me a process that can take 10-15 minutes before I get physically out of bed, as soon as you are sure you are not going to fall back to sleep, either take the mask off (allow auto-stop to kill the blower) or stop the machine.
The reason I recommend that is that wrassling around and changing position as I wake up seems to mean my breathing becomes irregular while doing that, very naturally, and the machine sometimes flags that as hypos or CAs, which are then actually false positives. There is no EEG so the xPAP has no idea whether you are asleep or not, and still flags what it perceives as events.
If you extend that line of thinking, this means that every time you change position during the night could be triggering your xPAP to flag false positive events.
Now, about the CAs; I think CAs are definitely scarier than OAs because OAs are a logistical issue, a physical blockage that can be prevented with xPAP, and have nothing to do otherwise with your CNS's attempt to breathe normally. The "central" in "central apnea" refers to events that are considered failures of the central nervous system to attempt to breathe normally. That, to me, is scary.
But I think there are a lot of false positives there. I had virtually none in my home test unaided by xPAP (AHI of 55.7, CI under 1, HI under 3), but I have had about twice as many CAs as OAs every single night on xPAP, at any pressure. So they are not coming from me, they are coming from the xPAP. And others report much the same thing.
And lowering the top IPAP range pressure is supposed to lower CAs indicating that higher pressure causes more CAs to be reported. And it seems, from my experience, that xPAP pressure causing CAs is behind that, and that it is causing false positives at lower pressure too, just fewer of them. There is some sort of mechanism at work here causing CAs to flag that may not actually be CAs.
It does not make sense that pressure can interfere with the nervous system's respiratory response; it's not like therapeutic pressure can prevent you from exhaling, or even inhaling; respiration continues regardless.
The part of respiration that induces you to inhale is because respiration feedback knows when you need to, and possibly pressure fools that by causing more oxygen to circulate via the turbulence of the Venturi effect which means more oxygen molecules reach receptors in the lung even after reaching past the top of the flow waveform than would normally, so your body has what it needs and does not induce another breath as quickly, and maybe that fools the xPAP into seeing that as a CA if that extends the time between breaths long enough.
The term "stopped breathing" is a misnomer, and should probably be referred to as "paused" or "delayed breath". Its not like you actually "stop breathing", because if you did "stop breathing" you would no longer be here.
My only disclaimer here is that I honestly have no informed idea regarding why false positives for CA occur, but many people still do report this. I am only speculating because no one seems to be able to answer why I have CAs with xPAP that never existed without it. xPAP doesn't even treat CA because it can't. Certainly none of this is definitive proof, but there is also no definitive disproof of this theory. Respiration that is good enough to prevent significant desat is not always a perfect repetitive waveform over 300-400 breaths, even in non-sufferers. So I would take the CAs reported with a giant grain of salt.