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dsm wrote:If there is a lack of min PS then I see some challenges. The data is really inadequate for assessing the capability of the unit.

Doug, could you expand the underlying rationale of your above statement for me?

I'm trying to understand just how a lower achieved PS of say 1 or 2, for instance, has anything to do with compromising "data assessment" on any machine. Thanks!

-SWS wrote:

dsm wrote:If there is a lack of min PS then I see some challenges. The data is really inadequate for assessing the capability of the unit.

Doug, could you expand the underlying rationale of your above statement for me?

I'm trying to understand just how a lower achieved PS of say 1 or 2, for instance, has anything to do with compromising "data assessment" on any machine. Thanks!

SWS,

Meanings

1) The data we have on the BipapSV is really inadequate for assessing the machine.

2) The data given for the BipapSV makes no mention of a Min PS & to me that is a fundamental weakness of the Bipap Auto (no min PS). Which takes me back to 1

Basically, we need a lot more info before anyone can make *serious* comparisons.


D

dsm wrote:SWS,

Meanings

1) The data we have on the BipapSV is really inadequate for assessing the machine.

Okay. Now I understand exactly what you mean by "data", Doug. You're really talking about the information we have available for our own assessments, and not any kind of "data assessment" that algorithmically executes inside an auto/adaptive SV machine. You can probably now understand my initial confusion about your statement.

dsm wrote:2) The data given for the BipapSV makes no mention of a Min PS & to me that is a fundamental weakness of the Bipap Auto (no min PS).

Okay. Once again I now understand that you are referring to the "information given" on the marketing literature", and you don't actually mean "data given" in the literal sense. Sorry I initially misinterpreted that, Doug. However, this "lack of min PS" on the Respironics Auto SV is a function of extra or optional modalities. So far I don't personally view that as a fundamental weakness. So far I see it as a functional extension of the PS range (on the lower end of that PS range).

dsm wrote:Basically, we need a lot more info before anyone can make *serious* comparisons.

If you're talking about operational comparisons, then we have plenty of information for some very serious exploratory discussions. The information I have peeked at thus far includes patents, both provider's manuals, and marketing literature.

However, if you're talking about efficacy achieved across CSA/CSR patient populations, then you are absolutely right, Doug! Unfortunately we have yet to get that kind of comparative epidemiological data for even APAP machines. But we do have plenty of individual anecdotes about APAP use and plenty of highly-uncontrolled data submissions from individuals using various APAP models.

Back to examining operational differences between the two auto/adaptive SV machines. So far my take is that one of the biggest operational differences between these two machines is in how each algorithm samples and targets patient flow: Resmed targets minute volume (more delivery-targeted points per inspiratory cycle) versus the Respironics machine that targets peak flow (essentially one key delivery-targeted point per inspiratory cycle). It remains to be seen just how these two different flow-targeting approaches will compare across patient populations. However, my own vague and highly unqualified hunch is that the CSDB patient population in general just may end up faring better with Resmed's targeting of minute volume. However, as you point out, Doug, that kind of information/data just isn't available yet.

dsm wrote:The data given for the BipapSV makes no mention of a Min PS & to me that is a fundamental weakness of the Bipap Auto (no min PS).

-SWS wrote:...this "lack of min PS" on the Respironics Auto SV is a function of extra or optional modalities. So far I don't personally view that as a fundamental weakness. So far I see it as a functional extension of the PS range (on the lower end of that PS range).

Right, if you have a bilevel anything, by definition you have PS, and consequently a PSmin. A PSmin of 0.0 cmH2O (going from CPAP to ASV vs BiPAP to ASV)? Hmmm, interesting thought.

Fundamentally, ASV is still ASV. Even though you are monitoring Peak Flow:



The actual response has to be Pressure Support:

-SWS wrote:my own vague and highly unqualified hunch is that the CSDB patient population in general just may end up faring better with Resmed's targeting of minute volume.

I still think the biggest obstacle in ASV is addressing the patients with poor Sleep Efficiencies and a lot of Wake/1 transition, which messes up baseline calculations. If AutoSV can overcome that, with either a low PSmin, low "Back-Up Rate", longer Monitoring Window (will 4 minutes vs 3 do it?) or simply less aggressive attack by using Peak Flow instead of Minute Ventilation, then that might open this up as a viable option for some folks.

Speaking of "Back-Up Rate" in re: AdaptSV, I don't really think it works that way. That implies that a patient can never drop below 15. Yet this guy was f <15 for most of the night:



It's Target Ventilation that's the trigger, not rate.
SAG

DSM and SAG have hit upon something very key.
We don't understand enough of the algorithms of either machine - and by looking at measured results, that SAG offers is our only real way of gaining insight into how the machine(s) can help CSDB or other variants of SA.

SAG, walk all of us through the graphs in the last post.

The Tidal Volume shows considerable fluxuation, and then it begins to vary a small amount. Is this an apnea or hypopnea? In other works the breathing is shallow? and an event occurs.

The VT than changes dramatically.

During the point where the VT is not varying, the backup rate of the machine, since it has no significant patient breathing to use as input, reverts to whatever the algorithm's default rate might be. And in this case
it happens to fall below 15. And the $5000 question is why, if the literature claims the backup rate is 15 when no other inputs are available.

Have I missed anything else, put more into laymans terms, for those of us semi sleep deprived that don't want to think about the complex descriptions?

StillAnotherGuest wrote:

dsm wrote:The data given for the BipapSV makes no mention of a Min PS & to me that is a fundamental weakness of the Bipap Auto (no min PS).

-SWS wrote:...this "lack of min PS" on the Respironics Auto SV is a function of extra or optional modalities. So far I don't personally view that as a fundamental weakness. So far I see it as a functional extension of the PS range (on the lower end of that PS range).

Right, if you have a bilevel anything, by definition you have PS, and consequently a PSmin. A PSmin of 0.0 cmH2O (going from CPAP to ASV vs BiPAP to ASV)? Hmmm, interesting thought.

Agreed. Here's where PS min of zero fits everybody's definition: automatically going from CPAP to ASV and back to CPAP. That functional scenario entails going from PS of zero to some positive value of PS and once again back down to PS of zero.

But when you see Respironics list BiPAP as one modality and BiPAP+PS as another modality, then PS here takes on a distinctly different functional definition than ordinary BiLevel. When this machine automatically transitions from delivering ordinary BiPAP to delivering BiPAP+PS, then as you correctly point out BiLevel delivery occurs during both modi.

Yet Respironics very clearly distinguishes what they call "BiPAP" and "PS" as two separate system output functions for this machine. When this system automatically delivers "BiPAP", it very clearly delivers constant IPAP and constant EPAP because measured patient flow is not out of bounds. The algorithmic decision to deliver "BiPAP" only (and not the "BiPAP+PS" modality) occurs because patient flow is simply not out-of-bounds. Regardless, when any servo-feedback system delivers consecutive cycles of IPAP and EPAP at constant respective pressures, then you have a pressure-based feedback loop orchestrating the system's output for those moments.

BiPAP mode here is comprised of two fixed pressures. Right? Is fixed pressure delivery ever maintained in any system without primary reliance on a pressure-based feedback loop? When this algorithm decides to deliver fixed "BiPAP" without the "PS" component, the machine uses a pressure-based feedback loop to immediately target and deliver pressure.

However, this system has temporal characteristics that define which feedback-based loop is used (pressure or flow) for immediate/short-term system response regarding pressure output. So all of a sudden the patient's measured flow begins to fall out of bounds. The temporal characteristics of this system's output now change to what Respironics calls "BiPAP+PS". System modality (regarding output response) changes because patient flow is out of bounds! Fixed-pressure IPAP and fixed pressure EPAP are no longer delivered by this system. Rather the algorithm automatically transitions the system from "BiLevel" modality to "BiPAP+PS" modality.

That modality transition means this algorithm must now transition the system's output from fixed BiPAPl (Respironics simply calls this "BiPAP") to variable BiLevel (Respironics calls this "BiPAP+PS"). Now the system adaptively modifies or varies the pressure for each delivered IPAP and EPAP cycle (as long as the "BiPAP+PS" modality is in operation) . During this BiPAP+PS mode of operation, the system's output now necessarily employs its own flow based feedback loop to determine these system-varied IPAP and EPAP pressure levels, on a per-breath basis.

What Respironics calls "BiPAP" operation is this system sequentially targeting fixed output pressures. Thus the system's pressure-based feedback loop is exclusively employed on the system's output side, at least for the moment.

What Respironics calls auto "BiPAP+PS" operation is this system delivering moving IPAP and EPAP pressures. During these system modality moments, the system necessarily relies on its flow-based feedback loop to vary IPAP and EPAP delivered pressures.

The algorithm can clearly and automatically transition the system back and forth. It does so based on the following type of pseudo decision-making process: Is patient flow in bounds? Then the system delivers fixed pressures (via pressure-based feedback loop). Is patient flow now out-of-bounds? if so then the system modality transitions to delivering variable pressures (flow-based feedback now primarily employed). In that first case there is no central dysregulation and thus patient-flow is algorithmically deemed to be within bounds. Also, in this first-case modality the patient adequately maintains flow on nothing more than fixed BiPAP, without ASV (or what Respironcs calls "PS") having to step in and adaptively modify each breath.

SAG wrote: Fundamentally, ASV is still ASV. Even though you are monitoring Peak Flow:

<image snipped>

I agree that these are both ASV machines. They both monitor/target flow and they can both adaptively vary delivered PS on a per-breath basis. Those two salient characteristics very clearly make them ASV in my mind.

SAG wrote:The actual response has to be Pressure Support:

<image snipped>

Absolutely. Pressure and flow travel together in physics. But in this Respironics system a flow-based feedback loop very clearly varies BiLevel pressure on the output side. Yet, when what Respironics calls "PS" has not yet kicked in (on the system output side while in "auto" PS mode), then a pressure-based feedback loop very clearly "pins down" delivered pressure on that output side---at least for the moment.

SAG wrote: I still think the biggest obstacle in ASV is addressing the patients with poor Sleep Efficiencies and a lot of Wake/1 transition, which messes up baseline calculations.

I agree that excessive Wake/1 transitions have to be hard to algoritmically baseline. I am still wondering just how many underlying pathologies might account for excessive Wake/1 transitions. Rhetorically: how many problems in physiology seem to be associated with disruptive cyclic alternating pattern (CAP)? I'm also hopeful but not at all certain that delivered pressure-patterns of ventilatory assistance can fix the majority of what may be going wrong in physiology with those excessive Wake/1 transitions.

SAG wrote: If AutoSV can overcome that, with either a low PSmin, low "Back-Up Rate", longer Monitoring Window (will 4 minutes vs 3 do it?) or simply less aggressive attack by using Peak Flow instead of Minute Ventilation, then that might open this up as a viable option for some folks.

I truly hope, in a very BIG way, that this turns out to be the case.

SAG wrote:Speaking of "Back-Up Rate" in re: AdaptSV, I don't really think it works that way. That implies that a patient can never drop below 15. Yet this guy was f <15 for most of the night:

<image snipped>

It's Target Ventilation that's the trigger, not rate.

Target ventilation and respiratory rate tend to travel in pairs as well. Resmed also claims to be looking at the duration of pause between exhalation and inhalation. That analytic parameter is a function of time. I think Adapt SV may actually use a multifactorial trigger for back up rate, despite the boiled-down explanation Frequen very kindly managed to garner for us. However, it also appears that the ASV back-up trigger or criteria somehow does not suit Frequen. I was personally very disappointed to read this. Darn it...

Lubman wrote:...by looking at measured results, that SAG offers is our only real way of gaining insight into how the machine(s) can help CSDB or other variants of SA.

Key pieces to the big puzzle for sure. But IMHO it helps to put as many pieces together as possible. And even these graphs cannot stand alone in describing either algorithmic system behavior or epidemiological response. They can't even stand alone in describing patient-specific pathologies. Not to down play those graphs by any stretch. They are extremely important pieces to the puzzle in my own opinion. I am incredibly grateful to SAG for providing them. .

These posts of mine pertain ONLY to figuring out the operation of this Respironics Auto SV. My posts DO NOT pertain to any kind of statement about what works for patients and what doesn't work.

But... here is PS min equal to zero on this Respironics Auto SV machine:


When this machine is set up with CPAP as a base therapy and auto PS mode, then CPAP mode on the right may actually deliver for much, most, or even all of the night! That's PS=0! If this system needs to stabilize central breathing, then it will automatically superimpose a PS, as you see in the left rectangle. In the left rectangle a flow-based feedback loop is used to achieve system output (the varying part of the pressure waveform). In the right rectangle a pressure-based feedback loop is used to achieve system output (fixed pressure now). The algorithm can automatically trade back and forth this way, imposing PS on an as-needed basis.

When this machine is set up as a fixed CPAP, then it will deliver CPAP for the entire night. When that happens this system's pressure-based feedback loop is exclusively used the entire night on that system's output.

Only two of four operating modes have been graphed above. The BiLevel+PS graph will be presented very soon.

SAG, the machine cannot be set up to automatically transfer between both CPAP and BiPAP modalities---at least in the same configuration or "nightly mix". It can be set up in one of these four ways for any given sleep session:

1) Fixed CPAP
2) Fixed BiPAP
3) CPAP and automatic PS interspersion throughout the night
4) BiPAP and automatic PS interspersion throughout the night

In those last two possible set ups or configurations flow-targeted and thus fluctuating PS may or may not be automatically interspersed. But it probably will be interspersed if the patient was correctly DX'ed and RX'ed. Regardless, that auto PS modality (we have been refering to as ASV) temporarily replaces either traditional CPAP or BiPAP throughout the night, on an as-needed basis.

I guess the issue I raised re min PS setting is that in the Bipap Auto that setting isn't settable by the user. It is fixed in the machine at 2 CMS & my tests with pressure gages on most machines other than the PB330 & PB420 ranges, show that there is a loss of around 1 cms that is *not* being shown in the data coming from the same machines tested (Vpap IIIs and Bipaps).

I can see that with the SV machines that monitor and respond to minute ventilation or peak flow, and or a basline of the user, that it doesn't matter what the CMS settings are as long as the tidal volume meets the therapy & comfort needs of the user.

The Bipap Auto was starting to look like it was a test bed for the BiapapSV. I was satisfied from my own inspections that in fact the Biap Auto was the Bipap Pro 2 with an enhanced algorithm (but lacking a PSmin setting for the user) & one point for me is if the BipapSV turned out to be the Bipap Auto with yet a further tweak of algorithm, then I have doubts about it as any major advance in the technology. It starts to look more like a PR gesture.

But as I have said, we don't have enough data on the machine's and their functions & despite any reservations I have, the user & user's results are the real judges.

Probably worth qualifying all this with ... 'old technology that produces better results, will always trump new technology that doesn't'. Another view is that 'it is usual for newer technology to provide tangible benefits over older technology although sometimes the bulk of the benefits are to the manufacturer & not the user'.

But again, it is great to have units put forward as competitors so as to give users the opportunity to try different approaches.

DSM

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

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

Doug, on that same concept of old technology versus new technology. Two general comments that I'd like to throw in the mix. One comment is that I think this newer ASV technology (both Resmed's and Respironics) probably still has some very major developments yet to come.

My other comment relates to why I think new medical technology tends to comes along: new technology at least endeavors to address shortcomings in old technology. For some patients Resmed ASV has already proven to be an improvement over old technologies. For yet other patients the Resmed ASV seemingly needs more development.

By the way, that CPAP+PS mode should theoretically have drastically different system output characteristics compared to the Resmed ASV for any patient meeting this profile: infrequent central dysregulation throughout the night. That type of patient would theoretically sit in CPAP mode almost the entire night in this Respironics modality. That same patient would receive ventilatory assistance the entire night on the Resmed ASV machine. Reminder: that's operational theory only, and not real-world efficacy.

Everybody has been very wisely commenting that real-world efficacy and theory of operation are two different things. That's definitely worth emphasizing in this thread. That and the fact that we've done a lot of bumbling, trying to figure out just how these machines work.

Lubman wrote:SAG, walk all of us through the graphs in the last post.

Well, we can do a couple.

Let me preface this by saying that I don't think AutoScan (or in this case it's actually ResScan) is going to provide a great amount of really good detail in these cases. A lot of this simply boils down to "It's Working" ("That's Amazing!") or "It's Not Working" ("That's Not So Amazing!").



I originally called the areas indicated by the red arrows at 1 and 3 runaways, with the net result being the machine gets a little "pushy". The AdaptSV was set to default (EEP 5.0 cmH2O, MinPS 3.0 cmH2O, so if things were stable, it should simply be sending out a bunch of 8/5 waveforms. But as you can see, the "IPAP" is well over it's baseline of 8 cmH2O for extended periods. And it maxes out at 15 cmH2O frequently. And it's not attacking events.

In the case of the Tidal Volume, it's just putting in points for what the tidal volume is at the moment (600 ml, 1000 ml, 0 ml, etc.). Looking at the actual breaths in that first area from the PSG shows us the following pattern:



The actual breaths are reflected in ASV Pressure. As you can see, for every 2 pressure waveforms (at least) sent in, there's only one real flow waveform, but within that is a blip. The blip represents a second breath sent in prematurely, or stacking breaths, or whatever you want to call it, but there is a patient-machine asynchrony. Normal tidal volume should be about 500 ml, so what that tidal volume graph represents is a collection of stacked breaths (the 1000's) and blips picked up as breaths (the 0's).

Lubman wrote:The Tidal Volume shows considerable fluxuation, and then it begins to vary a small amount. Is this an apnea or hypopnea? In other works the breathing is shallow? and an event occurs.

The VT than changes dramatically.

So in answer to your question, that center area is stable breathing with a tidal volume of 500 ml. The ends are asynchrony associated with Wake/Stage 1 transition.

During the point where the VT is not varying, the backup rate of the machine, since it has no significant patient breathing to use as input, reverts to whatever the algorithm's default rate might be. And in this case it happens to fall below 15. And the $5000 question is why, if the literature claims the backup rate is 15 when no other inputs are available.

It's not a "Back-Up Rate" in the S/T sense of the word, i.e., the machine will never allow you go below 15. If your breathing is stable and you can easily see <15, which is what it's doing in this case. And as christine explained earlier, rate is only one component of what matters, minute (alveolar) ventilation.

What's really important is how long you want to wait to respond when you do have a central apnea. At f=15, you have a 4-second apnea. You want to go to f=10? That's a 6-second apnea. Meanwhile, the pCO2 is increasing, and the whole goal of this is control pCO2. Wait too long and the pCO2 will increase such that the resultant hyperpnea on the rebound will cause the cycle to perpetuate. If you want to fix CHF/CSR, get an AdaptSV. If you want to dial in rates, get an S/T.

Looking at the Minute Ventilation in the graphs seems to be helpful. Refer back to Page 21 to see the examples of Normal (or Controlled) and untreated "neat" CSDB, "messy" CSDB and CHF/CSR. And to those we can now add this one, asynchrony. The fluctuations are a little bit coarser.

If you have the ability to do trend downloads, then looking at Minute Ventilation can also give some insights to "good" and "bad" nights.
SAG

Since we are looking at graphs, here is data from my study thanks to my doctor sending it along with explanations, which I am also including (I have asked for some clarifications but have not heard back yet):


1. Adapt with you in stable slow wave sleep--everything looks good in slow wave sleep! Nice steady nasal pressure tracing (that is the channel to watch)


2)Adapt in light sleep--notice the sharp spikes in the nasal pressure tracing--that is that back-up rate issue. The EEG gets thick and dark--that is the resultant arousal. There-in lies the problem


3)BIPAP--narrow I:E difference--first just look at the difference in respiratory rate--so much slower than 16!


4)BIPAP at reasonable pressures to control nasal pressure (airflow) in REM and Non-REM sleep--this is with EERS and end-tidal CO2 stabilized.

SAG wrote:Speaking of "Back-Up Rate" in re: AdaptSV, I don't really think it works that way. That implies that a patient can never drop below 15. Yet this guy was f <15 for most of the night:

I agree...why would Lubman & I consistently have 5th &95th percentiles below 15 if it held steady to its BR of 15? I did learn something interesting combing through the clinical manual- the lowest RR rate it will report is 8, yet it can report 0 for MV & TV. So I guess you always have to breath at least 8 times a minute, but not inhale

-SWS wrote: Agreed. Here's where PS min of zero fits everybody's definition: automatically going from CPAP to ASV and back to CPAP. That functional scenario entails going from PS of zero to some positive value of PS and once again back down to PS of zero.

But when you see Respironics list BiLevel as one modality and BiLevel+PS as another modality, then PS here takes on a distinctly different functional definition than ordinary BiLevel. When this machine automatically transitions from delivering ordinary BiLevel to delivering BiLevel+PS, then as you correctly point out BiLevel delivery occurs during both modi.

But couldn't, using Respironics terminology, we say the Adapt is BiLevel+PS? It maintains at the minimum PS (in my case 12/9) as long as everything is fine. And when it needs to, it adds the additional PS to trigger stable breathing.

Personally, I don't think I would want a PS of less the 3, but that's because I've always been on BiPAP and was use to a spread of 5 points. In my opinion, changing from extremely low or no PS gap to suddenly having one could potentially disrupt sleep...if not be downright annoying. And isn't there some evidence that the changing of pressures helps with stabilizing some types of central events? The lower gap and initially having me at a much lower EEP felt like I didn't have BiPAP support during my Adapt titration; it helped once they moved EEP up to my old EPAP, but it still took some getting use to. Just for fun, I guess I should pull out one of BiPAP ST and see how it feels now for a nap someday in comparison.

SWS wrote:

SAG wrote: I still think the biggest obstacle in ASV is addressing the patients with poor Sleep Efficiencies and a lot of Wake/1 transition, which messes up baseline calculations.

I agree that excessive Wake/1 transitions have to be hard to algoritmically baseline. I am still wondering just how many underlying pathologies might account for excessive Wake/1 transitions. Rhetorically: how many problems in physiology seem to be associated with disruptive cyclic alternating pattern (CAP)? I'm also hopeful but not at all certain that delivered pressure-patterns of ventilatory assistance can fix the majority of what may be going wrong in physiology with those excessive Wake/1 transitions.

I know I've been pleasantly surprised by how well the Adapt has dealt with my on-set/state 1 centrals. Its a major improvement from BiPAP ST; and miraculous compared to the non-treatment portion of the split-night PSG just prior to the Adapt titration (ie: 'difficult to score sleep', 'microsleeps interrupted by central hypopneas' for over an hour)

On the CAP...isn't Wake/State 1 sleep transitions inherently unstable sleep, so I'm not sure excessive CAP would be considered an issue there. Some amount of CAP is normal, its when it start showing up in excessive amounts during SWS that its a problem with sleep quality. Personally, I've been thinking a lot about the CAP issue and how my sleep quality has changed since the Adapt. I know with the severe AI originally, my doctor expected it to get somewhat better with BiPAP ST; it didn't and actually became more severe (2005 PSG). Could some of the improvement I had in CAP & AI with the Adapt be a result of it getting breathing stabilized, leaving the brain to do what its suppose to be doing?

Another issue to throw out is all xPAPs disrupt sleep somewhat, but they disrupt it much less then untreated apnea would (hopefully). One concern my doctor expressed early on, when the BiPAP ST titration showed only a 50% reduction in AHI, was he didn't want me to use it if it caused more problems then it helped (which we found certain BiPAP ST did). For most people with CSA, the IPAP/EPAP gap has to be wide enough to hopefully trigger breathing in Timed mode, but that same wide gap can be disruptive at times, no matter the rise time and other 'comfort' settings. Add in a the Timed rate kicking in sometimes when you just take a little longer then normal breath and there's another disruption...and we haven't even got to an apnea disrupting sleep yet. The Adapt glides much more between the two pressures, keeping the pressures and the pressure gap as low as possible unless it senses a problem, so some of the improvement in sleep brain activity has to come from that. What part, I don't know...

Then there is the whole downward spiral of SBD, AI, & CAP causing sleep disruption, which makes you more tired all the time & feel like you want to sleep, but then you can't sleep because the SDB, AI & CAP are even worse now because you are so overtired and what little sleep you get is severely disrupted by SDB, AI & CAP. Repeat for several years and you're no longer just on a downward spiral, but circling the drain.

SWS wrote:

SAG wrote: It's Target Ventilation that's the trigger, not rate.

Target ventilation and respiratory rate tend to travel in pairs as well.

It has to...Target Ventilation is the Minute Ventilation its wants you at, and Minute Vent= BPM x Tidal Volume...so you were both right

SWS wrote: Resmed also claims to be looking at the duration of pause between exhalation and inhalation. That analytic parameter is a function of time. I think Adapt SV may actually use a multifactorial trigger for back up rate, despite the boiled-down explanation Frequen very kindly managed to garner for us.

I agree that the backup rate is a floating backup unless it doesn't have the data to determine one, then it relies on the 'failsafe backup rate' of 15. What I remember from my Adapt setup, which was also my DME's hands on training, the ResMed rep (former head PSG tech at a large sleep lab, multi-state region rep & a CPAP user himself) said the only reason the backup rate of 15 is listed is for billing purposes. No backup rate, no billing as a BiPAP ST...and as much as we would like it, DME's don't want to accept the much lower regular BiPAP rate of $240/month rental/$1800 purchase when BiPAP ST monthly rental rate is over $600/$6000 purchase price. (and as a side note, when autoCPAPs first came out, the manufactures tried getting them billed as a regular BiPAP because they 'change pressures', but it didn't fly and they got the same code as regular CPAPs).

I don't know the technicalities of what data points its collecting, but having the flexibility to breath at my own pace is such an improvement. BiPAP ST have come a long way in trying to make Timed mode more comfortable then the old dial for what percentage of the breath cycle you wanted for IPAP the original BiPAP ST had. But when you have a fixed backup rate, its always going to get in the way at some point. Not every single breath you take is exactly the same length as the one before it- they average out to however many breaths per minute. But the BiPAP ST doesn't think that way, its like a metronome keeping beat, expecting you take a breath every so many seconds. It would be interesting to see how much centrals a machine like the Adapt could treat using only the variable backup rate and set IPAP/EPAP; unfortunately it can't be set that way.

The Resmed Adapt SV backup rate is multifactorial after all. Here are multiple factors that are decision-weighted toward deriving back up delivery via fuzzy logic:

Resmed Patent Text wrote: Rule 5 permits an expiratory pause, whose length may be long if the subject has recently been breathing adequately, and short or zero if the subject is not breathing. This is particularly appropriate for subjects with Cheyne-Stokes breathing, because an expiratory pause should not be permitted if the subject is apneic. Rules 6-7 provide for quick resynchronization in the event that the subject breathes irregularly. Rule 8 provides the equivalent of a timed backup, in which, to the extent that the subject has stopped breathing or is not adequately breathing, the ventilator will cycle at a suitable fixed rate. Rule 9 provides that to the extent that the subject is breathing adequately, the ventilator will tend to track the subject's recent average respiratory rate. This is particularly appropriate in subjects with cardiac failure and Cheyne-Stokes breathing, whose respiratory rate tends to be extremely steady despite rhythmic changes in amplitude.

My interpretation: that response-based criteria was mathematically modeled during the design phase based on common CSA and CSR variants. Unfortunately, that resulting back up delivery criteria is not well-suited for Frequen but seems dandy for Christinequilts.

Christinequilts wrote:But couldn't, using Respironics terminology, we say the Adapt is BiLevel+PS? It maintains at the minimum PS (in my case 12/9) as long as everything is fine. And when it needs to, it adds the additional PS to trigger stable breathing.

At first glance those respective modalities sound similar to me as well, Christine. But we really don't know how the two systems compare temporally, regarding variable PS kicking in and variable PS kicking out. Since they both aim to stabilize central dysregulation, we would hope they both efficiently and effectively kick in at about the same time, relative to identical respiratory variables. But... I am guessing there will be a variety of real-world efficacy differences between these two machines, based on different algorithmic approaches alone.

Christinequilts wrote:Personally, I don't think I would want a PS of less the 3, but that's because I've always been on BiPAP and was use to a spread of 5 points. In my opinion, changing from extremely low or no PS gap to suddenly having one could potentially disrupt sleep...if not be downright annoying. And isn't there some evidence that the changing of pressures helps with stabilizing some types of central events? The lower gap and initially having me at a much lower EEP felt like I didn't have BiPAP support during my Adapt titration; it helped once they moved EEP up to my old EPAP, but it still took some getting use to. Just for fun, I guess I should pull out one of BiPAP ST and see how it feels now for a nap someday in comparison.

I have absolutely no clue if that PS min of zero (CPAP+PS modality) is truly desirable for anybody. DSM flags it as a potential weakness, you and SAG also seem to question its usefulness. I simply acknowledge that it operates that way, and that the system output characteristics comparing the two ASV machines can be different because of it. Different but good? Different but bad? I would think that it might serve somebody's etiological nuances. At least it is optional. Maybe Respironics put it in there during an unusually boring lunch hour one day. .

Christine,

In your post you said ...
"Personally, I don't think I would want a PS of less the 3, but that's because I've always been on BiPAP and was use to a spread of 5 points. In my opinion, changing from extremely low or no PS gap to suddenly having one could potentially disrupt sleep...if not be downright annoying. And isn't there some evidence that the changing of pressures helps with stabilizing some types of central events? The lower gap and initially having me at a much lower EEP felt like I didn't have BiPAP support during my Adapt titration; it helped once they moved EEP up to my old EPAP, but it still took some getting use to. Just for fun, I guess I should pull out one of BiPAP ST and see how it feels now for a nap someday in comparison. "

The issue re min gap is precisely my thinking.

I don't see much use for Bilevel below a 3 point ipap/epap gap other than for people with lung problems or related medical issues. I have tried gaps from 1 to 6 & consistently came back to 4 as my ideal but 3 as my minimum acceptable. 2 seems a frustrating difference in that it is just never quite enough & thus irritating.

I was going to pose a similar issue to one you made re changing gaps in-flight - "does going from no gap to a gap of say 3 or more - in flight - cause more problems (discomfort) that it solves".

You are someone qualified to answer based on your realworld use of Bilevels. I know what I have learned from using them. Maybe people could handle varying gaps, but based on what I know and my own experience, I would need a lot of convincing that it was helpful therapy.

DSM

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

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