(03-26-2015, 09:36 AM)Terry Wrote: ...
My expectation is based on physics and math.
Well, that certainly clears that up.
I base my opinion on physics also. But mine is only an opinion, not an expectation of surety. And math? There is no math that can explain this, and to think so would indicate a pretty fuzzy idea of what math even is, unless you would care to enlighten us.
Oh, and this is also supported by tons of anecdotal evidence on this forum and others, and various other sources.
I also don't think a machine that flags an event when I simply hold my breath while awake while changing sleeping positions (something most of us do unconsciously) or if I purposely breathe shallowly and calls that a sleep apnea event
can be very good at all in being accurate about what it is reporting.
My PSG split sleep study with xPAP showed no CAs. My home sleep study with no xPAP also showed no CAs. Yet every night with xPAP my CAs are twice what my other events are, or at least as reported. And they flag at low pressure levels. Explain that with physics and math, both of which I hold degrees in.
I'll explain part of it for you.
The xPAP alone doesn't have a good ability to distinguish an actual CA, especially when you are awake, so many are false positives, and here is exactly why: the algorithm for CAs is to sense a halt in respiration, FOT the airway to determine if it is open, then wait and see if respiration returns within a prescribed time. If not, a flag is thrown. It really doesn't get much more sophisticated than that, because there is no magic bullet that will tell the xPAP more about what is going on from simply relying on sensing respirational feedback in the pressure system.
That is not an indication of a CA event, that is an indication that respiration paused for longer than normal without the airway being restricted, which is not the definition of a central nervous system-caused apnea event, only an indication that there was halted respiration.
That is all it can detect. It can't detect an actual CA, because there is no way to do that. It can only detect conditions that indicate that there MAY have been clues that MAY be describing a CA event, with no proof positive either way. So it is more akin to a wild-assed guess based on limited information. Which leaves the door wide open for false positives, meaning the xPAP does NOT have a "pretty good idea" whether there was an actual CA event or not. It's plenty smart, just not smart enough to do that.
xPAP in a PSG study probably also throws false positives, but those are thrown out because the other, better PSG data collected at the same time recognizes them as false positives, something the xPAP can't seem to do on its own.
And that probably explains completely why a patient presenting with no CA events without therapy, also presenting with no CA events in the PSG study with xPAP, might present with reported
CA events when the therapy is in place and is only
reported by the xPAP itself. Some of those are very likely false positives, and that is supported by reports from experts in numerous articles, not to mention in person directly to me by a practicing neurologist with a fellowship in sleep medicine. I've already googled and read the articles, so if you want to google them and read them too, be my guest. Be sure to include all of the experts that say this is not what is happening, too, because that will not take very long at all, since it appears that none have.
Don't get me wrong, I am totally on board with xPAP, I think it is a godsend. It is rare for any medical condition to have a therapy with virtually 100% effectiveness, virtually no side-effects, and is very minimally invasive. Its a miracle. It changed my life.
And the technology is amazing and well-advanced. But that does not mean it is perfect, or that there is a good way for an xPAP to accurately flag CA events. Everything has limitations. The $10,000 Apple Watch will still need to be charged every night. Not every problem has a perfect solution.