APAP Does Not Work As Good as BiPap?

[Darth Vader Look]

Here you go DSM:

Respironics Patent for Auto

[Guest]

DVL,

Thanks - I have it.

Now I don't suppose you have a link to the Bipap Pro 2 patent ?

or the Bipap S/T one.

I have done some looking but not located them myself.

Thanks

DSM

[Ric]

DVL, thanks for the link, yes that's what I was looking for. This time I will save a copy. True enuf, the current software probably only vaguely resembles the original description. On the other hand I would be surprised if the general "idea" of upping the pressure, then holding off because of an indeterminate finding of a possible "central", was not somehow represented in the current algorithm. On the other other hand, I am disinclined to disassemble the C object code just to find out, (although it would be fun).

...for this converse conclusion, cortical arousal data would need to be present to support that cortical arousals occurred for all seemingly terminated apneas and were therefore exclusively responsible.

Yes, I see your point, it is a question of who/what deserves credit for jump-starting the breathing process. It would be nice to have a bedside EEG to answer some of these questions. (It would be nice to have one to answer some of the threads relating to delta-wave activity pre- and post-xPAP therapy). Another fun project that probably won't see the light, THIS lifetime. *sigh*

[-SWS]

It would be nice to have a bedside EEG to answer some of these questions. (It would be nice to have one to answer some of the threads relating to delta-wave activity pre- and post-xPAP therapy). Another fun project that probably won't see the light, THIS lifetime. *sigh*

Ric, I've priced them on eBay, and I realize that makes me one very, very sick and twisted lab rat.

DSM, yes, APAPs are necessarily preemptive. However, APAPs are necessarily responsive as well. I will come back to this thread in a couple/few days and highlight an APAP algorithm designer's objectives and constraints regarding that rate of pressure rise with respect to the amount of pressure to clear highly variable apneas.

This kind of discussion is much too addictive for me and I have clients angrily waiting with pitch forks in hand. Thank goodness I had the foresight to dull the tines when they weren't looking.

[-SWS]

DSM, let’s revisit your hypothetical scenario: 1) an APAP user is sound asleep on his side, 2) APAP pressure is running at 9 cm, 3) that APAP user suddenly rolls on his back, 4) he then very suddenly experiences a positional-aggravated apnea that is heavier now that he is in the supine position, and 5) that sudden heavy apnea requires a pressure of 12 cm (3 cm above the current 9 cm). The question at hand is what does the APAP do in response to this scenario?

The good news is the above scenario is an improbable one. I say that because the scenario necessarily implies the following contradictory sequence of events: 1) the APAP user first incurs a sleep stage shift so that voluntary muscle control can happen, and 2) the patient instantly experiences a severe apnea as if he were in the deeper stages of sleep where autonomic muscle control and obstructive apneas tend to occur. I believe the typical sequence of events goes something like this: 1) the APAP user first incurs a sleep stage shift where voluntary muscle control is possible, 2) the patient uses that voluntary muscle control to coordinate limbs and torso into the supine position, 3) the patient then very gradually transitions back into deeper stages of sleep (where autonomic muscle control takes over and obstructive apneas are most inclined to occur). So the very first apnea will not happen with the shift to supine position. It will happen after transitioning into deeper sleep. And in all likelihood that supine apnea will be just as precursor-characteristic as any other supine apnea that occurs immediately following transition into the same stage of sleep. So I really don’t think the “turning onto the back” scenario is as problematic for an APAP as most of us might initially suspect.

My understanding is that there are cases where patients do very quickly manifest apneas during sleep onset and stage transitions, regardless of shifts in sleeping position. In this latter case an ideal APAP machine would still manage to correctly characterize SDB-event distribution, SDB density, SDB sequence, and even certain statistical pressure metrics, such that subsequent similar SDB sequences would be recognized and handled effectively. A pattern and probability based algorithm might also be inherently capable of recognizing certain uncharacteristic SDB patterns, as long as those patterns simply met basic recognition criteria. Unfortunately with even the most ideal pattern and probability based algorithm, an SDB distribution that is either sparse or void of discernable patterns may actually result in an APAP machine treating the SDB patient largely via reactive software routines versus preemptive ones---specifically in the case where precursor type SDB events also happen to be uncharacteristically sparse or void. And depending on the end treatment result, this hypothetical patient might very well be a better candidate for fixed-pressure CPAP or even Bi-Level treatment.

Not to short-change you of that scenario where an APAP machine has to increase pressure 3 cm or even more to address an apnea that is significantly heavier than the algorithm had predicted. You and I both know that happens. One key question that I do not yet have an answer to is just how often this problematic scenario occurs. The talented APAP data-set miners among us may just come up with a way for us to get a rough idea of whether this is a significant problem. To simply spot significant numbers of occurrences of lengthy time spent in apnea while pressure increases is enough to identify this as a problem. However, for lack of accompanying cortical arousal data this type of data mining would not reveal the exact degree of this problem. Anyway, DSM, I will post how I believe any APAP algorithm must handle this particular challenge in my next post.

[dsm]

SWS,

Yes - a fair reply. I think you probably realised that the scenario was fairly simplistic just to make it easy to follow but you are quite right. The rolling onto back is going to introduce a sequence of pre-cursor events & by the time an apnea occurs hopefully the machine has already closed the gap needed.

What would (as you say) be very helpful is any data held by any of our members here, where they show an OSA event & the pressure pattern & changes before it.

As said before if AUTOs could 'kill' full OSAs before they occurred, they wouldn't show up as OSAs in the stats.

********

I have been working my way through the patent data DVL provided and it makes very interesting reading.

I would have enjoyed being a designer of this gear had I ever heard of it back when progressing through my career.

********

DSM

[-SWS]

As said before if AUTOs could 'kill' full OSAs before they occurred, they wouldn't show up as OSAs in the stats.

Thanks, DSM. When you get some time would you mind elaborating on the above statement? I'm not certain I understand what your definition of a "full OSA" is, for instance. And would you mind expanding a bit on the underlying logic of that statement---or point me to a past post that elaborates? That sounds like a very important characterizing statement regarding the operation of an APAP, and I'm not certain I know precisely what the statement means.

Does that statement mean an APAP is unable to completely prevent any obstructive apneas at all? And that the supporting logic for that statement is essentially: "Any residual apneas reflected in AI prove that APAPs are uncapable of preventing all apneas?"

As you can see I'm confused to high heaven about exactly what that statement means. I'm sure I'm reading that statement and its underlying logic wrong.

[dsm]

SWS,

Possibly terminology. What I am meaning by a full OSA event is when flow has ceased by a blockage. I though if I didn't qualify the description, it could easily appear to mean something else.

#Elaboration:
By 'kill' a blockage I really mean 'clear a blockage', - can the machine clear a blockage due to an apnea quicker than the patient naturally will. This particular point gets back to how long the average 'blockage' lasts vs the extreme (your mention of 3 mins).

I suspect the answer is yes & no - put another way, the machine wins some and loses some.

We are working with very limited tools (English language) in describing complex environments

Cheers

DSM

[NightHawkeye]

What would (as you say) be very helpful is any data held by any of our members here, where they show an OSA event & the pressure pattern & changes before it.

As said before if AUTOs could 'kill' full OSAs before they occurred, they wouldn't show up as OSAs in the stats.

Can I be the guinea pig, here?

Here's a chart of my AHI:

Can anyone tell where I switched to fixed pressure from APAP? or even where I switched from APAP to BiPAP-auto? The clue is where the time in apnea dropped in half.

Here's the chart of time in apnea.

Note the abrupt shift that occurred in May when I switched to fixed pressures. Clearly, the auto algorithms weren't clearing my apneas as effectively as fixed pressure. I'll also add that because of aerophagia, I'm handicapping the fixed pressure a bit. I know from tests already that if I increase pressure from where it's been the past few weeks, my apneas drop more, but aerophagia, and the associated pain, goes up dramatically.

I've already reached my conclusion regarding APAP's, and my conclusion is that the Respironics APAP algorithm cannot change pressure rapidly enough to pre-empt apneas. The data is unequivocal.

Regards,
Bill

[-SWS]

I've already reached my conclusion regarding APAP's, and my conclusion is that the Respironics APAP algorithm cannot change pressure rapidly enough to pre-empt apneas. The data is unequivocal.

Hey, Bill. Welcome. It's very good to see you in this part of the thread! And I'm glad that you posted that. I would, indeed, like for us to go through your charts as if they were a case study. However, can you also please clarify for me?

When you say that your conclusion is that "the Respironics APAP algorithm cannot change pressure rapidly enough to preempt apneas" is that conclusion intended as an SDB patient population generalization or is it intended as an observation relative to your particular case? Also, is that conclusion intended as a generalization for all or even most apneas, or rather, is that conclusion intended as an observation that there are indeed some cases where apneas cannot be adequately preempted?

Thanks!

[NightHawkeye]

When you say that your conclusion is that "the Respironics APAP algorithm cannot change pressure rapidly enough to preempt apneas" is that conclusion intended as an SDB patient population generalization or is it intended as an observation relative to your particular case?

That's certainly a valid question, SWS. First, I'm not sure if my data represents a sample size of one or a sample size of two, because the data was collected with both the Remstar-auto and the BiPAP-auto. Even though the algorithms would be different, I'll assume that the differences are mostly in the sensor mechanisms, which means for operational purposes the machines should operate essentially the same. So maybe a sample size of one is appropriate.

Hmm . . ., now what to make of a sample size of one? Obviously, it's much better than a sample size of zero. A sample size of one usually provides a useful mean value but absolutely no information on variance.

To resolve this, one might ask if my apnea is typical? Probably not. My apnea tends to occur in clusters during REM sleep only. At other times I have no apnea.

On the other hand though, my apnea pattern is exactly the kind of apnea pattern that APAP's are advertised as being good for since my pressure requirements typically change radically throughout the night.

Also, is that conclusion intended as a generalization for all or even most apneas, or rather, is that conclusion intended as an observation that there are indeed some cases where apneas cannot be adequately preempted?

Once the machine gets to treatment pressure my incidence of apnea is low. However, what I've typically seen in my data is a smattering of apneas on the leading edge of pressure increases. This I take to mean that the machine simply cannot respond quickly enough to pre-empt the apneas.

The pressure range of change is on the order of 3 cm or 4 cm. I set the lower limit at 5 cm and the upper limit at 14 cm, but most nights the machine runs up to a maximum of around 9 cm, and occasionally higher.

I'm sure raising the lower limit would have helped, but that wasn't a good option for me because of aerophagia. Besides, if I'd raised it more than 2 cm, then the APAP function wouldn't really be doing much, would it?

FWIW, as a tangential issue, I do want to try another experiment with the BiPAP-auto to see if I can start with my current settings and let it run in auto over a narrower range than previously to see if that is more effective for me.

Regards,
Bill

[Guest]

I've already reached my conclusion regarding APAP's, and my conclusion is that the Respironics APAP algorithm cannot change pressure rapidly enough to pre-empt apneas. The data is unequivocal.

Since I was about to order the Remstar APAP, that's not what I wanted to hear. Would this be true for everyone using the Respironics APAP? That it can't work fast enough to preempt apneas? If your beginning pressure is high enough so it doesn't have so far to go up to preempt apneas does it still not work right?

I've been doing a lot of research and was about to upgrade from my Fisher & Paykel and order the Respironics APAP mostly because of the overwhelmingly good reviews on this board, but this fact changes everything. If it can't preempt apneas, why spend the extra money?

Can the Resmed APAP change pressure rapidly enough to preempt apneas? Or should I steer clear of all APAPs and stick with a regular CPAP machine? Which one would you recommend?

[NightHawkeye]

Excellent questions, Guest, and the very reasons this topic has been continuing off and on under various threads for some time.

Regards,
Bill

[Guest]

Thanks, I'm learning a lot here. I think I'll give up on the APAP idea. The whole reason for considering it was because I was under the impression those machines could preempt apneas and that the pressure could fluctuate all night long if it needed to in order to do that. If more people knew this isn't true, I bet they wouldn't be recommending them so much. I still want a new machine though and I know I want to try one with software so I can see how I'm doing. What would you recommend?

[NightHawkeye]

I still want a new machine though and I know I want to try one with software so I can see how I'm doing. What would you recommend?

Since you asked for my recommendation, I'd still recommend an APAP, although I suspect that the minimum pressure needs to be set close to the 90% pressure to eliminate the sort of residual apneas which show up in my own data, and then open the APAP maximum pressure up a little above that. An APAP gives you more options, just be sure to keep realistic expectations.

Just my $0.02 though. I'm not an expert by any means. After five months I'm still working to get my apnea controlled as well as I'd like it to be.

Regards,
Bill