Should EPAP=titrated pressure

[hrc54]

Hi all-

I own a Bi-pap auto. My current pressure is 16/13. My question (to those
who are on Bipap) is are your EPAP pressure equal to your titrated pressure
& your IPAP is 3-4 points higher than that?

My sleep doctor wasn't sure & admitted that some sleep docs prescribe that.
I thought the EPAP pressure was 3-4 lower than IPAP & IPAP was your titrated pressure. I know there was a thread 2-3 weeks ago about this.

Bob

[blarg]

You have an auto, why not give it a bit of a range and see what it says?

The whole idea of BiPAP is to give exhale relief, so it seems strange to me to set EPAP to your titrated pressure....

[dsm]

I discussed this with my respiratory specialist & he was adamant (& I guess right) when he said that the whole purpose of the sleep study titration is to arrive at a CMS setting the keeps obstructions to an aceptable minimum for a given person & to set any pressure lower than that defeated the purpose of the titration study.

But despite this discussion, I set my bilevel IPAP=titration & EPAP 3 below titration & I am quite satisfied with this plus my AHI numbers are typically below 1.0 so I can justify to myself this set up.

The Resmed EPR has a clever answer to this issue as when in EPR mode you set the main CMS to titration (equiv to IPAP=titration) then select a 1 2 or 3 cms pressure drop for the breathe out cycle. This is equiv to EPAP = 1 2 or 3 cms lower than IPAP. But!, when the EPR algorith detects problems (OSA) it suspends the EPR thus temporarily raising EPAP up to IPAP until the machine detects the OSA as resolved it self at which time it reactivates EPR.

The Respironics BiPap AUTO offers a very good solution as well because you get to set a range of pressure & all going well the machine can detect OSA episodes & raise both pressures if required, to maintain the set gap between IPAP & EPAP.

IMHO, the big unknown re changing pressures such as with AUTOs though, is the extent that dynamic pressure changes occuring over time (such as with an AUTO) are the cause of mixed apnea in that people do get used to a particular pressure & increasing it may well be the cause of subsequent pressure induced centrals even if over time the person could get used to the higher pressure. So I am now wondering if the information recently published on 'complex apnea' where they state that a key characteristic is that it is resistant to cpap, may actually be resistant to cpap that employs varying the pressures (an Auto) .

I would like to devise some tests to see if this can be indicated in anyway. One idea I have come up with (open to discussion) is for example to collect data for 3 nights with a fixed cpap setting of 13, then switch to 15 & run it for 3 nights at that. The theory being that if I am sucepible to complex apnea that includes pressure induced centrals, they will show up clearly on night 4 of the above test (allowing that 13 & 15 CMS are in the critcal range for myself when it comes to any likely pressure sensitivity).

#2: If the test did show a jump in AI or HI on night 4, the next prediction is that these numbers would then drop back over nights 5 & 6 as I got used to the higher pressure over time.

Back to your Bipap Auto. Because it is an auto, you don't have to worry about setting epap=titration

DSM



_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, resmed, bipap, Titration, CPAP, AHI, auto

[rested gal]

I own a Bi-pap auto. My current pressure is 16/13. My question (to those who are on Bipap) is are your EPAP pressure equal to your titrated pressure & your IPAP is 3-4 points higher than that?

My sleep doctor wasn't sure & admitted that some sleep docs prescribe that.
I thought the EPAP pressure was 3-4 lower than IPAP & IPAP was your titrated pressure. I know there was a thread 2-3 weeks ago about this.

Bob

It's my understanding that in a true bi-level titration at a sleep lab, where they are setting TWO pressures (one for EPAP, one for IPAP) the EPAP is set first....and is set at a pressure that eliminates all APNEAS. Then the titration proceeds on up with the IPAP to knock out any residual hypopneas, flow limitations and snores.

I know that sounds counter-intuitive. One would think a higher pressure would be needed to get rid of APNEAS and a lower pressure handle HYPOPNEAS.

But that's not the way I've seen it explained by sleep techs. It seems that a lower pressure (often 9 or 10) is sufficient to completely prevent APNEAS, but more pressure is needed to keep the throat well and truly open...to prevent hypopneas and flow limitations.

And when you look at it this way, it makes sense: getting the throat open "somewhat" is preventing full or almost full collapse (apneas.) Doesn't take as much pressure to keep the throat open "somewhat". But to prevent the throat from having ANY COLLAPSE at all, it takes more pressure. More pressure to prevent even partial collapse (hypopneas.) More pressure to keep the throat absolutely and completely open.

An old topic about bi-level titration was here:

viewtopic.php?t=1926
Mar 18, 2005 subject: Questionable advice from Pulmomologist

"Titrator", who was a sleep tech explained how a bi-level titration is done.

Something that I didn't pay much attention to at the time because I had never tried at bipap machine back then was this quote from the guy who started the topic:

The RT from my DME said by raising the higher setting from 13 to about 17, it would actually help make my exhalation easier than it would be at a constant cpap of 13.

And because I had a bit of trouble exhaling at a cpap of 13, the RT said a BiPap setting of 17/13 would actually be easier for me to exhale than a setting of 13/10. Supposedly, a higher inhalation setting would help the exhalation.

This point intrigues me, I have no idea if the RT is right or not, and I would really appreciate you comments especially on this on this.

I've found what Andy's RT said to be true...for me, anyway. I can use straight cpap at 9 and it feels like work to exhale against the 9 coming in. Not objectionable and I get used to it after a few minutes, but...a bit of effort nonetheless. A feeling of breathing out against at least some resistance.

However, with bipap delivering 11 or 12 coming in and 9 for exhaling, the exhalation feels like nothing at all. I've often said, it feels like breathing out into an empty hose. Right from the very first breaths....no having to "get used to it." I think Andy's RT was exactly right about "higher inhalation pressure would help exhalation." It's apparently the relative difference between EPAP/IPAP that gives the extreme comfort of breathing out with a bi-level machine.

So, if a person had had only a titration for a single cpap pressure (not a real bi-level titration) BUT was using either just a bipap or the bipap auto, I'd say that EPAP should be set at (or very close under) a person's prescribed "cpap" pressure...and the IPAP set 3 - 5 cms above it. That's just my opinion, and I'm not a doctor.

With the BiPAP Auto operating in ABPAP or AbFLE (auto bipap with or without "bi-flex") however, you don't have to be that exact about where you set either the EPAP or the IPAP as long as you have the IPAP higher than "prescribed single pressure" would be.

In either auto-titrating mode, the bipap auto will find (hopefully ideally -- there can always be exceptions! ) the correct EPAP to use and correct IPAP to use, varying them separately as needed throughout the night. And regardless of how far apart the range betweeen EPAP and IPAP you've set, the bipap auto will start out the night using only two cms more inhalation pressure than whatever you have set the EPAP at. Neither one will go up unless necessary. Each will work independently of the other as far as the PS "leash" allows.

For my take on that leash:
viewtopic.php?t=15666
Dec 08, 2006 subject: Question for BiPap users - UPDATED 12/14/2006

I own a BiPAP Auto also. Using it in AbFLE mode (auto bipap with bi-flex enabled) my current pressure setting is 9 EPAP / 16 IPAP. The machine starts out the night using 9 for exhaling (EPAP) and 11 for inhaling (IPAP).

The "leash" (PS setting) that I set between EPAP and IPAP on my machine lets them range as far apart as 7 cms apart -- the difference between 9/16. Sixteen minus nine = seven.

Most of most nights, the machine uses 9 EPAP, 11 or 12 IPAP. Occasionally the IPAP will range up a little more, but the EPAP rarely ever rises above 9. Doesn't anywhere near 16.

9 or 10 were the pressures that worked best for me in two different nights of full cpap (single pressure) titrations. That's why I chose "9" for EPAP in my bipap auto.

[rested gal]

I discussed this with my respiratory specialist & he was adamant (& I guess right) when he said that the whole purpose of the sleep study titration is to arrive at a CMS setting the keeps obstructions to an aceptable minimum for a given person & to set any pressure lower than that defeated the purpose of the titration study.

But despite this discussion, I set my bilevel IPAP=titration & EPAP 3 below titration & I am quite satisfied with this plus my AHI numbers are typically below 1.0 so I can justify to myself this set up.

dsm, What EPAP/IPAP setting are you using? Is your IPAP set at the 15 that was a mistaken number, or at the 13 that was your "real" cpap titration number?

Oct 08, 2006 subject: Surprise surprise
viewtopic.php?t=14176

Went to my sleep specialist today - haven't seen him since before going on cpap in mid 2005. Here is a frank and honest report on the meeting that took place & some of the matters discussed. Contained a few surprises for me

In his hello he read the summary from my sleep study saying "and your titration recommendation was 13".

WHAT says I, I was told 15!. In fact I phoned the sleep clinic back when setting up my machine to ask if the handwritten note stating the titration cms was a 13 or a 15 as it was not easy to read. The clinic came back with 15. So for over 18months (until I recently lowered the cms to 13 based on my own home study) I had been running the machines at 15 as the main cms setting.

The difference between 14 and 15 for me is that it has always been the threshold for mask leaks - and all the other extra surprises we get when we go to higher cms settings (aerophagia etc:)..

The other point that this sleep specialist made during discussions & going over the results of some of the testing I had done, was that the titration of 13 IS THE MINIMUM cms they recommend for cpap for me. It is the number at which I am likely to have events if my pressure is set below that number.
He pointed out that me setting my epap to 8 was too low and that was why the bad results had shown up with the bilevel set to 8/15. He stated again that the titration number was in effect the epap!. It is the threshold at which AI & HI events are best contained!.

[-SWS]

Now for a slightly different opinion of traditional BiLevel pressure requirements. I've seen sleep techs describe various BiLevel titration procedures. We've also anecdotally read of some sleep docs setting their patients' EPAP pressure at CPAP-equivalent pressure. Yet we've also anecdotally read of yet other sleep docs setting EPAP pressure three or four points below CPAP-equivalent pressure----and achieving great AHI results for those patients. In the real world of sleep medicine, both of these BiLevel pressure-setting protocols are implemented in vast numbers.

So what does that imply? To me it implies that critical mass-related airway closures probably occur at different points in the inspiratory and expiratory phases for different patients. I personally don't think it's likely that the phase-related timing of critical airway closures is identical across the SDB patient population. Why would we expect it to be?

I believe that patients manifesting critical airway closures as early as end-expiration require EPAP pressures that are equivalent to CPAP, in order to clear the airway. And patients manifesting airway closures that only become "obstruction-critical" during inspiration can, indeed, get by nicely with EPAP pressures set three, four, and sometimes five points below a CPAP-equivalent pressure (for the sake of expiratory comfort).

How else might we explain the fact that some purely obstructive patients can get away with low AHI's while EPAP pressure is set so significantly below CPAP----all the while yet other obstructive patients actually require EPAP pressure to be set at a higher CPAP-equivalent pressure to achieve those same low AHIs? I can't think of any other purely obstructive theories, other than "we don't all occlude at the same exact moment during respiration". There's clearly some respiratory phase-related variation occurring in the SDB patient population. And your phase-distribution of critical occlusions will dictate whether you can get away with EPAP set several points below CPAP, or if you require EPAP to be set as high as CPAP-equivalent pressures.

That's been my story all along, and I'm still stickin' to it! .

[-SWS]

Doug, so far this thread has been largely about timeliness of airway inflation. That timeliness being driven by when the occlusion becomes critical relative to EPAP and IPAP deliveries---and making sure that if the occlusion overlaps both phases with "critical closure mass", then EPAP needs to be just as high as CPAP would have been to clear the obstruction.

I could be wrong, but I thought you mentioned that you and Frequenseeker had initially decreased AHI by lowering your IPAP value to more closely approach EPAP. You thus initially had a somewhat vast IPAP/EPAP spread, you closed the gap by lowering IPAP (as opposed to raising EPAP), and you still managed to drop your AHI significantly.

If so, that's a whole different physiologic mechanism than your doctor described.

Two Scenarios Decribed So Far:
1) Your doctor's explanation: Vast IPAP/EPAP spread, with EPAP too low to address expiration occlusions (remedy for this scenario would have been to raise EPAP)

2) Doug's Experiment: Vast IPAP/EPAP spread; Rather than raising EPAP as in the doctor's scenario above, you dropped IPAP to achieve a much narrower spread. The results were that you achieved much better AHI's, hinting that you very likely eliminated some timing-related skewing of the central drive itself (versus addressing expiratory obstructions as your doctor suggested---after all, EPAP stayed the same in this scenario!)

So, Doug.... I'm inclined to believe your first retrospective take about what happened, was the correct analysis all along. And that while your doctor's advice was both prudent and prevalent, it did not apply to what transpired in that very first experimental step that you and Frequen took (before I managed to get involved).

My guess is that if your sleep doc had that extra tidbit of information, he too would have characterized what happened correctly as well. What's your take on all that, Doug? .

[rested gal]

There's clearly some respiratory phase-related variation occurring in the SDB patient population. And your phase-distribution of critical occlusions will dictate whether you can get away with EPAP set several points below CPAP, or if you require EPAP to be set as high as CPAP-equivalent pressures.

I agree absolutely with that, -SWS.

we've also anecdotally read of yet other sleep docs setting EPAP pressure three or four points below CPAP-equivalent pressure----and achieving great AHI results for those patients.

Another thought why that could work well, besides "respiratory phase-related variation" ....

Given how a cpap (single pressure) titration is often aimed at "worst case scenario" (on one's back and in REM) I can also imagine the single pressure titration might arrive at considerably more pressure than is needed most of the time by some people who may rarely, if ever, actually sleep on their back at home.

I can see how those people also could get great AHI results from EPAP set considerably lower than the titrated, prescribed cpap single pressure...if "worst case scenario" position (on back) PLUS stage (in REM) wasn't happening together very often most nights, regardless of when their airway collapse usually happens -- at end of exhalation or beginning of inhalation.

As you said, however: "we don't all occlude at the same exact moment during respiration." What you've pointed out no doubt has more bearing than anything else with what EPAP/IPAP pressures will be most effective.

[-SWS]

All good points IMHO, Rested Gal. One of these days I'd love to get you at a patient conference, or out on a cruise ship, or something like that... just to glean your general thoughts and observations for a few days.

To add yet more speculation to some of the conjecture, observations, and even fact already in this thread... There may also be significant numbers of BiLevel patients out there needing to sacrifice a few AHI points to achieve an overall more comfortable night of sleep.

Sleep comfort can certainly be compromised by airway occlusions. However, I think it's clear that for many patients, sleep comfort can also be compromised by higher pressures. There just may be plenty of patients and even doctors out there who feel compelled to balance these two potential "sleep-comfort detractors" by dialing the pressure just a little lower than what would have been the best pressure for an optimum AHI. In other words, for many of us, optimum AHI numbers may not equate to optimum sleep comfort.

In my opinion, BiLevel pressure therapy (and even PAP therapy in general) can sometimes be very complex and very individualized.

[dsm]

Quick response (heading out soon)

I had my PB330 machine set at 15 ipap and 8 epap (but had BPM set at 6 as it is an S/T type machine). This seemed ok - was a great improvement to me over a declining benefit when I had been on cpap/auto.

But as an aside (& in advance of explaining the next test), I believe the reason it seemed to work ok was that the machine was in S/T mode & I suspect the BPM of 6 was hiding a problem (excessive HI numbers) that later showed up when I did tests using a VPAP III S run in S mode (I did this switch to VPAP III from PB330 to get the detailed nightly data as my PB330 does not record it).

Back to the 15/8 - when I switched to a VPAP III S run in S mode, the above settings were producing AHI numbers in excess of 40-50 !!!
(see http://www.internetage.com/cpapdata/ )

After discussion with Frequenseeker & some test suggestions from SWS I (over a few days) upped the EPAP and lowered the IPAP. So IPAP ultimately came down 2 points & EPAP went up 2 points - now my IPAP=13 & my EPAP=10 and has pretty well remained so apart from a few variations tried from time to time (several times I went 10/14 but felt it was not as comfortable so always reverted to 10/13, I also tried 9/12 but got odd breathing results & quickly reverted to 10/13)

On 10/13 I immediately began scoring AHI under 3.0 - a dramatic improvement over the VPAP III S results as shown in the linked to charts (remembering though that on the PB330 I felt & thought I was doing quite ok & attribute this to it being in S/T mode whereas the 1st VPAP III I tried was only an S mode machine - leads me to suspect that T mode when activated, can supress many AI & HI problems).

After achieving the above, I had a scheduled visit to my respiratory specialist - it was then I learned from him that the titration had been for 13 all along & the 15 was a transcription error by the sleep clinic.

Some several weeks back I reverted to a Remstar Auto set 10/14 and was getting AHI scores under 1.0 - I used it for just under 2 weeks. I think my av was about 12.7 CMS or thereabouts.

My preference though, was to go back to the PB330 Bilevel running at 10/13 and using a BPM of 6 (I have become addicted to T mode ). I still haven't come up with a good justification as to why I feel so much happier with this S/T mode Bilevel but of all the many machines I have tried, I feel very comfortable with this particular one. I do want to compare it to the VPAP III S/T set up in a similar config. One possibility is that the AHI will be a lot lower because the BPM of 6 is kicking in and preventing HIs that were a big contributor to the very high AHI scores when using the VPAP III S machine.

So I now also have a Bipap Auto and the VPAP III S/T. The BipapAuto unfortunately does what all the other Bipap AutoTrak machines I have do & that is for me it flips Ipap to Epap far too soon & is not comfortable for me when I am struggling with nose breathing or nasal congestion. It is a pity there are so few adjustments on these AutoTrak Bipaps.

So in summary:

I BOTH lowered IPAP by 2 and increased EPAP by 2 to get to where Iam now & the results are for me now outstanding & very satisfying.

DSM

### Tidied up parts of the content & added some bits

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): bipap, Titration, CPAP, AHI, auto

[-SWS]

Excellent post, Doug! Thanks so much! .

[dsm]

I own a Bi-pap auto. My current pressure is 16/13. My question (to those who are on Bipap) is are your EPAP pressure equal to your titrated pressure & your IPAP is 3-4 points higher than that?

My sleep doctor wasn't sure & admitted that some sleep docs prescribe that.
I thought the EPAP pressure was 3-4 lower than IPAP & IPAP was your titrated pressure. I know there was a thread 2-3 weeks ago about this.

Bob

It's my understanding that in a true bi-level titration at a sleep lab, where they are setting TWO pressures (one for EPAP, one for IPAP) the EPAP is set first....and is set at a pressure that eliminates all APNEAS. Then the titration proceeds on up with the IPAP to knock out any residual hypopneas, flow limitations and snores.

I know that sounds counter-intuitive. One would think a higher pressure would be needed to get rid of APNEAS and a lower pressure handle HYPOPNEAS.

But that's not the way I've seen it explained by sleep techs. It seems that a lower pressure (often 9 or 10) is sufficient to completely prevent APNEAS, but more pressure is needed to keep the throat well and truly open...to prevent hypopneas and flow limitations.

And when you look at it this way, it makes sense: getting the throat open "somewhat" is preventing full or almost full collapse (apneas.) Doesn't take as much pressure to keep the throat open "somewhat". But to prevent the throat from having ANY COLLAPSE at all, it takes more pressure. More pressure to prevent even partial collapse (hypopneas.) More pressure to keep the throat absolutely and completely open.

An old topic about bi-level titration was here:

viewtopic.php?t=1926
Mar 18, 2005 subject: Questionable advice from Pulmomologist

"Titrator", who was a sleep tech explained how a bi-level titration is done.

Something that I didn't pay much attention to at the time because I had never tried at bipap machine back then was this quote from the guy who started the topic:

The RT from my DME said by raising the higher setting from 13 to about 17, it would actually help make my exhalation easier than it would be at a constant cpap of 13.

And because I had a bit of trouble exhaling at a cpap of 13, the RT said a BiPap setting of 17/13 would actually be easier for me to exhale than a setting of 13/10. Supposedly, a higher inhalation setting would help the exhalation.

This point intrigues me, I have no idea if the RT is right or not, and I would really appreciate you comments especially on this on this.

I've found what Andy's RT said to be true...for me, anyway. I can use straight cpap at 9 and it feels like work to exhale against the 9 coming in. Not objectionable and I get used to it after a few minutes, but...a bit of effort nonetheless. A feeling of breathing out against at least some resistance.

However, with bipap delivering 11 or 12 coming in and 9 for exhaling, the exhalation feels like nothing at all. I've often said, it feels like breathing out into an empty hose. Right from the very first breaths....no having to "get used to it." I think Andy's RT was exactly right about "higher inhalation pressure would help exhalation." It's apparently the relative difference between EPAP/IPAP that gives the extreme comfort of breathing out with a bi-level machine.

So, if a person had had only a titration for a single cpap pressure (not a real bi-level titration) BUT was using either just a bipap or the bipap auto, I'd say that EPAP should be set at (or very close under) a person's prescribed "cpap" pressure...and the IPAP set 3 - 5 cms above it. That's just my opinion, and I'm not a doctor.

With the BiPAP Auto operating in ABPAP or AbFLE (auto bipap with or without "bi-flex") however, you don't have to be that exact about where you set either the EPAP or the IPAP as long as you have the IPAP higher than "prescribed single pressure" would be.

In either auto-titrating mode, the bipap auto will find (hopefully ideally -- there can always be exceptions! ) the correct EPAP to use and correct IPAP to use, varying them separately as needed throughout the night. And regardless of how far apart the range betweeen EPAP and IPAP you've set, the bipap auto will start out the night using only two cms more inhalation pressure than whatever you have set the EPAP at. Neither one will go up unless necessary. Each will work independently of the other as far as the PS "leash" allows.

For my take on that leash:
viewtopic.php?t=15666
Dec 08, 2006 subject: Question for BiPap users - UPDATED 12/14/2006

I own a BiPAP Auto also. Using it in AbFLE mode (auto bipap with bi-flex enabled) my current pressure setting is 9 EPAP / 16 IPAP. The machine starts out the night using 9 for exhaling (EPAP) and 11 for inhaling (IPAP).

The "leash" (PS setting) that I set between EPAP and IPAP on my machine lets them range as far apart as 7 cms apart -- the difference between 9/16. Sixteen minus nine = seven.

Most of most nights, the machine uses 9 EPAP, 11 or 12 IPAP. Occasionally the IPAP will range up a little more, but the EPAP rarely ever rises above 9. Doesn't anywhere near 16.

9 or 10 were the pressures that worked best for me in two different nights of full cpap (single pressure) titrations. That's why I chose "9" for EPAP in my bipap auto.

RG,

That is one good post

In looking back at my experience with the 8/15 setting on the VPAP III, I did become concerned at the gap between the IPAP & EPAP being the main cause of the very high AHI scores. On reflection & after my RT's comments, I then wondered if it was the EPAP being set at 8 that was really the main culprit.

To this day I am still not sure but following the logic in your post it seems likely to have been the EPAP of 8 that was the culprit. Also SWS offered some interesting observations in another post elsewhere re epap cycle being just as prone to OSA as the ipap cycle.

As I have done various test over time, I have observed one other interesting thing, if I have been on a fixed cpap cms or fixed ipap/epap set of pressures, for some while (days) and then I make a slight change - up or down - to the pressures, this seems to trigger a night of odd breathing including what I suspect are pressure induced centrals. Again in recent months I did some variations to my PB330 machine (set it to cpap mode & then later to I/E mode (normally it is in A/C mode which is same as S/T mode - but PB call it 'Assist Control')).

In straight CPAP mode, I had the least problems when changing pressures but as you have explained so well, I too really like that pressure differential between inhale & exhale and it is that ipap/epap gap that makes using a Bilevel CPAP so easy to do even if the epap is set high.

The problem though with any pressure over 14, is that is when I get constant mask leaks & air into my eyes & squekas as the air slips out. This has become increasingly so as I have lost weight. When my face was bigger, the mask was a better fit - point here is that I would not want to go back to 15 cms or above no matter what type of machine as managing the mask is a PITB.

DSM

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): bipap, hose, Titration, CPAP, DME, AHI, auto, Bi-Level Machine

[Snoredog]

you may have been better off just taking a poll

cause it could be one way or the other.

[Guest]

Snoredog,

Actually, anytime I drop epap below 10 the AHI goes up as far as I have seen thus far. I will do a test soon where I go back to 8 CMS when I get round to testing with the VPAP III S/T, initially just in S mode. The liklihood IMHO is that the AHI will go up markedly when epap=8.

I will also try other tests such as setting 10/16 & look at the AHI. I think it may go up a bit, but HI is what I expect will go up most of all, if not all.

Then I will activate the BPM set at 6 for both the above tests as my theory is that T mode with a 3+ gap between epap/ipap does have the ability to supress some of the AI HI scoring that I believe will be produced while just in S mode in these tests.

Am now betting that lowering epap will do the real harm but I wouldn't bet any real money on the outcome.

DSM

[-SWS]

I will also try other tests such as setting 10/16 & look at the AHI. I think it may go up a bit, but HI is what I expect will go up most of all, if not all.

Am now betting that lowering epap will do the real harm but I wouldn't bet any real money on the outcome.

Doug, my general hunch is that an EPAP that is simply too low to clear expiratory-end-phase apneas is a fairly common caveat. PSG BiLevel titrations probably address that caveat quite well more often than not. My guess is that a less-common problem might be that an IPAP/EPAP spread that is too wide can, indeed, throw respiratory timing off a bit.

However, these two physiologic effects are probably not even mutually exclusive---meaning that it's probably possible to have an elevated AHI from both problems contributing or acting together. As an example: Let's say I set myself up with an IPAP/EPAP setting of 18/8 and achieve an AHI of a nice, round 40. I then experiment with a setting of 15/8 and achieve a new AHI of say 28. Next I try a setting of 15/12 and achieve an AHI of only 3 or 4. On that first hypothetical experiment where I decrease IPAP by 3 cm, my AHI hypothetically goes down a bit---presumably a central or respiratory drive improvement rather than having addressed more obstructions. Then on the second iteration, it actually becomes unclear just how much of that improvement can be attributed to clearing obstructions and how much can be attributed to avoiding central dysregulation. Of course, with a PSG, there is less guess work.

Most importantly, Doug, please don't experiment with the induction of respiratory drive desynchronization or even obstructive apneas if you have a great treatment already worked out. I don't like to see my message board friends go from feeling great to feeling poorly just to solve our curiosity. Besides, we gotta leave some work for the paid scientists and researchers. .

typos fixed on edit