My first night on ASV

dsm wrote:

Snoredog wrote:
<snip>

From my understanding of how this machine works, you leave BPM=Auto until you get EPAP set correctly, get IPAP Min and Max set correctly, then you only change it if you cannot eliminate PB or Central events. Your most fail-safe mode is to keep BPM=Auto. I also believe you should follow basic guidelines established elsewhere and not exceed the 10 cm Pressure Support limit, that limit is to prevent unnecessary lung damage. You don't want to do any harm with the machine.

Two nights back I set BPM=OFF (was =AUTO) just to see what would happen. The nights data was worse than normal but of course the patient triggered breaths line was flat

So I promptly reverted to BPM=AUTO - at least I know when I see an AP scored in the data (typically 6-10 for the whole night) & there is a blip in the patient triggered breaths line, I know the machine is probably just trying to tidy up an arousal breathing pattern - esp when my SpO2 pulse data shows a blip at the same time.

DSM

That makes sense you would get a solid Patient Triggered Breaths line, there is NO place to go when BPM=Off. Setting it to off pretty much disables backup mode where you can't see yourself having a central. A central will resolve itself if you don't do anything. BPM=4 is 15 second breaths, 7.5:7.5 I:E, since Inspiration on this machine can never exceed 3.0 seconds, that is 3 seconds (max) inspiration time and 4.5 seconds for exhale. In BPM=Auto mode digital auto-track will find your timing settings and RR when landing in BPM=Auto will be avg. seen in Spontaneous mode minus -2 (follows protocol).

Setting BPM=Off is like turning your headlights off while driving at night, you won't be able to see anything. Again, BPM rate is 2 less than the average BPM rate seen on Spontaneous side. If you want to see something different than what BPM=Auto delivers, use a different fixed value other than minus -2. For example, if your avg. BPM in Spontaneous is 15 you would normally set BPM to 2 less, so BPM=13 but setting it to that value is the same as BPM=Auto (where you get PB), so if you want something different try even slower than the protocol calls for, use minus -4 or minus -6 of that S average, try 10 or 8. I don't think anyone breathes at 4 breaths per minute which is the lowest you can input in fixed backup mode. Using that low a value you are just letting the event resolve on itself, but that is still better than having it Off where you can't see what is happening at all. The idea with BPM mode is to slow your breathing down, that is what BPM=Auto does, using fixed takes it further and not only does it slow breathing down it makes it slightly uncomfortable where the body says it don't like staying there and starts breathing spontaneously again. But if I return you to spontaneous breathing at a much slower RR than when you left you will go longer before PB again.

Just look at the waveform graph for CSR and think of the up and down inspiration waveform section/slice of that breathing being handled by SV side and the solid line of a central being handled by the BPM mode. Just set the SV side so its range can fix the waxing side of inspiration by pumping IPAP up, and padding it as it goes past inspiration peak down the other side. Keep in mind PB is periods of breathing then not breathing. When BPM=Fixed you are telling it what timings to use during that non-breathing period, so it tells it how often it should cycle between IPAP and EPAP and how long each aspect should be. Rise time will say how long it should take to go from bottom of EPAP to top of IPAP and IT should say how long that Inspiration should last, the rest is left for exhale until next Rise time begins. If you are staying too long in backup mode that means your settings are too comfortable and close to the spontaneous mode settings, you don't want that, you intentionally want it a bit slower so the body doesn't like it and starts spontaneously breathing again.

snoredog wrote:BPM=4 is 15 second breaths, 7.5:7.5 I:E

Well, I think with a max IT=3.0 seconds (as you correctly mention in the next quote) that 7.5:7.5 I:E ratio is impossible on this machine. So I take it that ratio you mentioned was a 1:1 reference of equal-distribution. Okay, I follow that part.

snoredog wrote:since Inspiration on this machine can never exceed 3.0 seconds, that is 3 seconds (max) inspiration time and 4.5 seconds for exhale.

This machine has only a BPM setting coupled with an IT setting. But I'm confused where that 4.5 seconds for exhale is derived.

If BPM=4 and IT=3 (min and max values respectively) the unlikely exhalation time that would be spontaneously "allowed" by the machine would be a whopping 15 seconds minus 3 seconds (derived from BPM=4 minus IT=3). Actually a little more than those 11 seconds might be "allowed" if the patient spontaneously assumes an IT of less than 3 seconds (that IT=3 is only an upper limit in S/T mode, unlike PC mode where IT is a fixed value). So there are supposedly only three parameters/restrictions that come into numeric play with S/T mode here: 1) BPM setting, 2) IT setting, and 3) a restriction that IT cannot exceed half of breath rate.

snoredog wrote: In BPM=Auto mode digital auto-track will find your timing settings and RR

I agree that the autoSV algorithm will maintain an averaged BPM. Digital auto-track is also Respironics' leak control logic. Can you believe they dedicated an entire web domain to Digital auto-trak? http://autotrak.respironics.com/


This is the part I thought was impossible with just a backup rate (S/T):

snoredog wrote:The idea with BPM mode is to slow your breathing down, that is what BPM=Auto does, using fixed takes it further and not only does it slow breathing down it makes it slightly uncomfortable where the body says it don't like staying there and starts breathing spontaneously again.

I'm confused how a backup rate can force or directly drive slower breathing. I can see how a backup rate can speed up breathing: it simply shoots the patient an EPAP-to-IPAP pressure transition before the patient would have spontaneously initialized their own E-to-I transition. That's easy to do. But I'm still confused how a backup rate can force a slowdown in anybody's breath rate.

The machine either issues the EPAP-to-IPAP pressure transition, or it withholds that pressure transition. If the machine issues that pressure transition quicker than the patient's spontaneous transition, then patient gets a little "hey let's speed things up" reminder. But if the machine decides to withhold that EPAP-to-IPAP pressure transition for say, 10 more seconds.... the patient doesn't get anything from the machine whatsoever by the way of a reminder or pressure transition. At that point the spontaneous respiratory drive is simply left to it's own devices regarding that very next respiratory trigger. Finally an apnea can be corrected when those same 10 seconds transpire. But waiting 10 or 11 seconds to back up a missing apnea isn't sufficient to drive a slower human respiratory rate.

So I'm not certain how an S/T machine that has no purely Timed mode can slow a patient's breathing down? If the autoSV had PC mode (also called Timed or T mode), then it could do what you describe (although S mode would never be resumed by the patient). According to all the Respironics marketing brochures and setup guides the autoSV just doesn't offer any PC or purely Timed mode (T). Rather, the autoSV only offers a patient either spontaneous mode (S) or backup modem (S/T). The BiPAP Synchrony and AVAPs machines, on the other hand, do offer a PC or purely Timed mode (T).

-SWS wrote:
<snip>

I'm confused how a backup rate can force slow breathing. I can see how a backup rate can speed up breathing: it simply shoots the patient an EPAP-to-IPAP pressure transition before the patient would have spontaneously initialized their own E-to-I transition. That's easy to do. But I'm still confused how a backup rate can force a slowdown in anybody's breath rate.

The machine either issues the EPAP-to-IPAP pressure transition, or it withholds that pressure transition. If the machine issues that pressure transition quicker than the patient's spontaneous transition, then patient gets a little "hey let's speed things up" reminder. But if the machine decides to withhold that EPAP-to-IPAP pressure transition for say, 10 more seconds.... the patient doesn't get anything from the machine whatsoever by the way of a reminder or pressure transition. At that point the spontaneous respiratory drive is simply left to it's own devices regarding that very next respiratory trigger.

So I'm not certain how an S/T machine that has no purely Timed mode can slow a patient's breathing down? If the autoSV had PC mode (also called Timed or T mode), then it could do what you describe (although S mode would never be resumed by the patient). According to all the Respironics marketing brochures and setup guides the autoSV just doesn't offer any PC or purely Timed mode (T). Rather, the autoSV only offers a patient either spontaneous mode (S) or backup modem (S/T). The BiPAP Synchrony and AVAPs machines, on the other hand, do offer a PC or purely Timed mode (T).

SWS,

yup - that is a good description AFAICT

Certainly how I would describe BPM=AUTO - breathing to fast ? then try to cycle at a slower rate in the hope the sleeper will follow - breathing too slow then try to cycle at a faster rate & trust the sleeper will folow. But also the machine does seem to understand Co2 retention & Co2 blow off (typical CSR indicators) - the patent sure says a lot about it.

DSM

Certainly how I would describe BPM=AUTO - breathing to fast ? then try to cycle at a slower rate in the hope the sleeper will follow - breathing too slow then try to cycle at a faster rate & trust the sleeper will follow.

Well, maybe that's happening. If it is, I think there are some extremely important warnings missing in the clinician setup manual---warnings that BPM=auto is required to fix certain types of breathing/timing issues that require patient RR slow-down.

And if it is happening, then at those moments the machine has to literally abandon conventional backup or S/T mode (a mode where IT is just an upper 3 second limit) and literally assume a purely timed or PC mode (where IT is no longer an upper limit, but is held fixed and at times necessarily longer than 3 seconds to force slow breathing).

That sounds feasible for CSR and PB. But if the autoSV were going to suspend ordinary backup or ST to correct CSR or PB, why would BPM=auto be a requirement? Doesn't the machine literature implicitly claim being able to fix CSR and PB using conventional fixed backup rates as well? Otherwise they would require a BPM=auto setting for certain apnea patients.

I dunno... There's no mention of PC mode capability anywhere... and there are no clinician warnings/advice anywhere that talks about a key feature that can slow down patient RR being available only in BPM=auto mode. I'm still thinking this particular SV model fixes everything with traditional S/T backup rates (that can be manual or auto-averaged) and automated IPAPpeak.

Another area I wasn't quite certain about is whether manual rise time is ignored or utilized when BPM=auto. I'm thinking there's an experiment that might help clear that up:

1) Set CPAP+SV modality (avoiding BIPAP+SV modality), BPM=auto, rise time=6
2) breathe several minutes of regular breaths to set up a flow-amplitude baseline window in the autoSV algorithm
3) simulate spontaneously triggered hypopneas (while avoiding simulation of either zero-flow or near-zero-flow apneas)
4) note how gradual or sharp rise time feels when automated IPAPpeak elevates
5) repeat steps 1-4 for rise time=1 instead
6) compare/contrast sharpness of delivered pressure slopes of both rise time settings

I'm thinking if manual rise settings are ignored when BPM=auto, that the two test iterations above should feel more or less the same regarding rise time. But if the manual rise times of 1 and 6 are utilized during automated IPAPpeak correction cycles (during those spontaneous breaths), then the above two test iterations should feel radically different regarding inspiratory pressure slopes.

We know that the manual rise time settings are observed for backing up missed breaths or apneas---even when BPM=auto. But the question in my mind is whether those rise time settings of 1 and 6 are ignored or utilized when IPAPpeak does it's job during any given spontaneous breath.

If anyone with an autoSV wouldn't mind running that experiment, they sure have my undying gratitude!

-SWS wrote:

snoredog wrote:BPM=4 is 15 second breaths, 7.5:7.5 I:E

Well, I think with a max IT=3.0 seconds (as you correctly mention in the next quote) that 7.5:7.5 I:E ratio is impossible on this machine. So I take it that ratio you mentioned was a 1:1 reference of equal-distribution. Okay, I follow that part.

The above was my math in thinking out loud, I had subtracted the 3 second maximum IT time possible from the I:E and didn't add the 4.5 seconds back to remaining to the exhale time (just the way I do math). But when you start defining what BPM will be, the only part of that breath you are defining here on this machine is the IT time from .5 seconds to 3 seconds (max).

So that 7.5:7.5 ratio shown is my bad for not completing the calculation and shifting the ratio over to the correct result of: 3:12 for a BPM=4 setting. BPM=## defines the overall length or duration of the breath that you will be using in fixed backup settings. So BPM is a critical setting and that breath is then carved up by the IT time used, so IT is what carves up that total breath time ratio. The I:E ratio is not a 1:1 ratio and that should not be automatically assumed.

1. You define how long the breath will be from BPM setting (60 seconds /BPM=duration of I:E)
2. You define how long Inspiration time will be (remaining time will be allocated for exhale).
3. You define how fast Rise Time will be.

You also have to remember that the person is NOT breathing when switched or entering the backup mode. They are NOT breathing because they failed to take an Inspiration breath. So that time is tagged on to the prior time allotment for the previous exhale time. So when you define BPM=xx where xx is 4 to 30, you are telling the machine what to expect from Inspiration to Inspiration, then you are defining what the IT time should be. I then read here where someone had used BPM=4, the "minimum". When you apply this machines logic to that even though it is an allowable setting it doesn't make any sense.

-SWS wrote: If BPM=4 and IT=3 (min and max values respectively) the unlikely exhalation time that would be spontaneously "allowed" by the machine would be a whopping 15 seconds minus 3 seconds (derived from BPM=4 minus IT=3). Actually a little more than those 11 seconds might be "allowed" if the patient spontaneously assumes an IT of less than 3 seconds (that IT=3 is only an upper limit in S/T mode, unlike PC mode where IT is a fixed value). So there are supposedly only three parameters/restrictions that come into numeric play with S/T mode here: 1) BPM setting, 2) IT setting, and 3) a restriction that IT cannot exceed half of breath rate.

I have not read where there is a "restriction" that IT cannot exceed half of breath rate. The SV has a limitation that IT time cannot exceed 3.0 seconds. I am unaware of any restrictions as of this writing on the S/T.

snoredog wrote: In BPM=Auto mode digital auto-track will find your timing settings and RR

I stand behind that statement, digital auto trak is used to detect inspiration and exhalation times in SV mode. In BPM mode those spontaneous times will be carried over to BPM=Auto mode. BPM value however will be minus -2 of what was found in Spontaneous mode.

-SWS wrote: I agree that the autoSV algorithm will maintain an averaged BPM. Digital auto-track is also Respironics' leak control logic. Can you believe they dedicated an entire web domain to Digital auto-trak? http://autotrak.respironics.com/

Yes I can believe they dedicated a webpage for it, have you read it? Because this is what it says on the first page
which is all I have read in this reference (more of my selective reading I guess):

Respironics website wrote:Inside and out, the entire Flex Family of pressure relief technologies relies on two Respironics innovations: Digital Auto-Trak Sensitivity and the M Series sleep systems. Digital Auto-Trak, the brains behind all of our Flex Family pressure relief technologies, is a highly sensitive algorithm that detects the onset of inspiration
and expiration – even in the presence of mask leaks. Being able to track, react and respond to each and every breath makes it possible for C-Flex, A-Flex and Bi-Flex to deliver the right pressure relief at the right moment.
Digital Auto-Trak has the ability to recognize and compensate for unintentional and intentional leaks in the system, and to automatically adjust its variable trigger and cycle thresholds to maintain optimum performance in the presence of leaks. No manual adjustments are required.
The Digital Auto-Trak components are all active concurrently. The machine reacts to the first component that detects a change, providing maximum sensitivity.

Sorry, but I read the above to mean this machine does a very good job at finding your Inspiration and Exhale times. xFlex seems to work pretty good in finding those timings as well (not many people complain about it). So I stand behind my statement that this machine uses Digital Auto Trak to find your I:E timings in SV mode.

snoredog wrote:The idea with BPM mode is to slow your breathing down, that is what BPM=Auto does, using fixed takes it further and not only does it slow breathing down it makes it slightly uncomfortable where the body says it don't like staying there and starts breathing spontaneously again.

Snoredog stands behind the above statement too. When you enter that mode you are not breathing with a central, when you do start to breath I'm sending you back to spontaneous mode at a slower rate than you were breathing before the central occurred or the breathing that contributed to the central event.

-SWS wrote: I'm confused how a backup rate can force or directly drive slower breathing. I can see how a backup rate can speed up breathing: it simply shoots the patient an EPAP-to-IPAP pressure transition before the patient would have spontaneously initialized their own E-to-I transition. That's easy to do. But I'm still confused how a backup rate can force a slowdown in anybody's breath rate.

The machine either issues the EPAP-to-IPAP pressure transition, or it withholds that pressure transition. If the machine issues that pressure transition quicker than the patient's spontaneous transition, then patient gets a little "hey let's speed things up" reminder. But if the machine decides to withhold that EPAP-to-IPAP pressure transition for say, 10 more seconds.... the patient doesn't get anything from the machine whatsoever by the way of a reminder or pressure transition. At that point the spontaneous respiratory drive is simply left to it's own devices regarding that very next respiratory trigger.

So I'm not certain how an S/T machine that has no purely Timed mode can slow a patient's breathing down? If the autoSV had PC mode (also called Timed or T mode), then it could do what you describe (although S mode would never be resumed by the patient). According to all the Respironics marketing brochures and setup guides the autoSV just doesn't offer any PC or purely Timed mode (T). Rather, the autoSV only offers a patient either spontaneous mode (S) or backup modem (S/T). The BiPAP Synchrony and AVAPs machines, on the other hand, do offer a PC or purely Timed mode (T).

I haven't totally dissected exactly what the S/T is doing or not doing, so I cannot comment on it, so my comments are with what the Adapt SV is doing or not doing for time being.

On the SV, when the patient gets sent to backup mode from system detecting a central, they are NOT breathing. IF BPM=Fixed settings is input the amount of time elapsed for next IPAP Min puff will be as defined by the BPM=## value used just as I explained above and elsewhere. The BPM defined will be intentionally defined with a slower value than seen in Spontaneous mode. It will do the SAME when BPM=Auto. Spontaneous minus -2. Any Inspiration "duration" time will be defined by IT=value. Rise time will define how fast that Inspiration will be delivered. With those fixed settings input, the machine establishes when it will cycle from IPAP to EPAP. Person lands there, 3 seconds is exceeded, machine is going to cycle to EPAP, once the time for that has elapsed IPAP Min pressure will be delivered. From Inspiration to Inspiration will be the time alloted by BPM. By using a ridiculously low BPM=4 when they do start spontaneous breathing again, it will be like hitting a brick wall. When they go back to SV side they will be all screwed up again with breathing.

Think of how central dysregulation begins, it starts by fast hyperventilation breathing or very slow and/or deep breathing. Just as the SV side targets Peak volumes, the backup mode is the same but you define that by the IT time and BPM used.

How can I say this nicely? As you know that is hard for me at times, so all I can say is: Don't assume you have the BPM mode totally nailed down as to its functional understanding of it, because that is where we continue to have a misunderstanding. Having that understanding is critical in the way you go about setting this machine up or correcting a particular event. There is your understanding of how it works, dsm's understanding of how it works and SAG's understanding of how it works. To be honest (and again with all due respect), neither one of you guys have gotten it right so far. If you set BPM=Off the patient better not have any central dysregulation period. Sure if you set BPM=Off, the Patient Triggered Breathing will go to 100%. Now you might think that is working much better but that is only because you have completely disabled the backup mode and your ability to see what is happening. Setting BPM=Off you have NO indicator you are going into Central Dysregulation as you can no longer see it.

That also means you are positive the SV side is going to correct breathing which contributed to the central dysregulation. Now if the SV was truly a panacea for controlling Central Dysregulation flawlessly there would be no need at all for a BPM mode. They put it there for a reason. And assuming that is simply not the case. While I agree the SV side can correct that condition through control of breathing, if the patient is continually going to central dysregulation as a result of SV side settings, you have removed any fail-safe mode to correct it. And that is ALL BPM mode is, a fail-safe way to correct central dysregulation. When a patient lands in the BPM mode they should only be there for a very short time, if you can use that short period of time in BPM to put them in a more favorable state for when they do return to spontaneous breathing you are ahead of the game. If you do nothing in response to a central it will resolve itself. Even in the case of Bev, where they were seen as high as 84 seconds even those resolve themselves. But if a person is going 84 seconds with a central, and you induce Insp for 1.2 seconds of one pressure then 4.8 seconds of EPAP pressure they will eventually start following that cycle of pressure. IF the goal behind BPM was to speed up a patients breathing they wouldn't suggest you use a value of minus -2 of spontaneous. So under no circumstances is this machine's logic for BPM designed to speed-up a person's breathing. So if your understanding is the patient is going to BPM mode because they are breathing too slow, then well you have that backwards too.

As you know when you shift that I:E center line ratio left or right of center (what I meant by 7.5:7.5 above) you are controlling Hypercapnia:Hypocapnia dysfunction. So by looking at a Encore report and its indicators which does a person have?

And with all due respect, I don't mean to be argumentative here about this, but for some time now there has been a clear misconception by both you and SAG (and dsm) on how this mode works. Now I realize that you guys are never wrong and try to get funny about it when someone calls you on it, but I don't blame dsm one bit for NOT understanding it either, he is only following the suggestions made by you two and well neither one of you have gotten it right to date. Sorry to be so blunt, but that is the way I see it.

Now I'll be happy to discuss the function of the BPM mode for a better understanding of it, go through any patent you want and basically discuss it. But the rules are you cannot automatically assume this machine has a function or a technology in use just because some other machine this manufacturer happens to make has it. Bringing into this discussion on what a Resmed machine does also is not a valid explanation/excuse on how this machine functions either. A lot of people that read these boards and rely on what you say as the "gold standard" on how a machine functions. This is not about who's right or wrong this is about who's right, because there is no room for being wrong.

I'm only for getting the functions of the machine nailed down accurately and that is where I am coming from. If dsm is interested in experimenting with PB and eliminating his while at the same time getting better sleep, I'm all for helping out where I can because it is my belief you can virtually eliminate the conditions of PB and Central Dysregulation with this machine. If you are unable to control those two phenotypes then well you don't have the SV settings set to allow that. My end goals are the same as yours, knowing exactly how this machine responds and what to expect when a change is made.

This machine is finely tuned and working correctly when there are NO therapy flags present, other indicator is 100% Patient Triggered Breathing while still having an available BPM mode set up for fail-safe. While this may be near
impossible to achieve, striving for the lowest values is all you can expect.

http://james.istop.com/apnea/reports/AsvNov27.pdf

I bumped up IPAPmin last night by 3cm. Since the hypopneas didn't seem to respond could those remaining events be central hypopneas? (which I don't really understand)

I did end up sleeping an usually long time at these new settings.

I have been having discomfort in my lower throat for some time now. Yesterday went to see my local ENT. He scoped my throat and found a small sore spot (nodule?) on my Epiglottis. He felt this was a result of GERD.

Great something else to deal with. Have I mentioned lately that I hate Sleep Disordered breathing and everything that goes along with it

Snoredog, thanks for explaining all that. Just a month ago you had mentioned wanting to explore BPM and IT here:
viewtopic.php?f=1&t=35298&p=304575&#p304575
Since then, a couple times you also mentioned wanting to discuss it. So I appreciate that you are still willing to discuss with us how BPM and IT works.

Snoredog wrote:

-SWS wrote:

snoredog wrote:BPM=4 is 15 second breaths, 7.5:7.5 I:E

Well, I think with a max IT=3.0 seconds (as you correctly mention in the next quote) that 7.5:7.5 I:E ratio is impossible on this machine. So I take it that ratio you mentioned was a 1:1 reference of equal-distribution. Okay, I follow that part.

The above was my math in thinking out loud, I had subtracted the 3 second maximum IT time possible from the I:E and didn't add the 4.5 seconds back to remaining to the exhale time (just the way I do math). But when you start defining what BPM will be, the only part of that breath you are defining here on this machine is the IT time from .5 seconds to 3 seconds (max).

So that 7.5:7.5 ratio shown is my bad for not completing the calculation and shifting the ratio over to the correct result of: 3:12 for a BPM=4 setting. BPM=## defines the overall length or duration of the breath that you will be using in fixed backup settings. So BPM is a critical setting and that breath is then carved up by the IT time used, so IT is what carves up that total breath time ratio. The I:E ratio is not a 1:1 ratio and that should not be automatically assumed.

1. You define how long the breath will be from BPM setting (60 seconds /BPM=duration of I:E)
2. You define how long Inspiration time will be (remaining time will be allocated for exhale).
3. You define how fast Rise Time will be.

That's pretty similar to our first BPM, IT, and I:E ratios discussion that we had a month ago. The I:E ratio of 1:1 is the autoSV default. Now I think I understand what you were saying with the 7.5:7.5 I:E ratio above. Thanks for the clarification.

Snoredog wrote:You also have to remember that the person is NOT breathing when switched or entering the backup mode. They are NOT breathing because they failed to take an Inspiration breath. So that time is tagged on to the prior time allotment for the previous exhale time.

Well, I have agreed with that statement all along. And that is the basis of how BPM=4 will back up a missed breath in under 15 seconds. At BPM=4 the machine won't allow a very long apnea with 3-second IT plus that "allowable" 11 or 12 second expirations (meaning apneas can be included in that latter time window as you correctly point out). So setting BPM=4 will never allow any apnea to go unchallenged for longer than that less-than-15-second "allowable" EPAP window.

Snoredog wrote:

-SWS wrote: If BPM=4 and IT=3 (min and max values respectively) the unlikely exhalation time that would be spontaneously "allowed" by the machine would be a whopping 15 seconds minus 3 seconds (derived from BPM=4 minus IT=3). Actually a little more than those 11 seconds might be "allowed" if the patient spontaneously assumes an IT of less than 3 seconds (that IT=3 is only an upper limit in S/T mode, unlike PC mode where IT is a fixed value). So there are supposedly only three parameters/restrictions that come into numeric play with S/T mode here: 1) BPM setting, 2) IT setting, and 3) a restriction that IT cannot exceed half of breath rate.

I have not read where there is a "restriction" that IT cannot exceed half of breath rate. The SV has a limitation that IT time cannot exceed 3.0 seconds. I am unaware of any restrictions as of this writing on the S/T.

This is from the manual:

BiPAP autoSV Clincian Manual wrote:Note: The inspiratory time and breath rate controls are linked so the inspiratory time never exceeds the expiratory time. If the breath rate or inspiratory time are set to values that would cause the I:E ratio to exceed 1:1, the inspiratory time is automatically reduced to maintain a 1:1 I:E ratio.

But that regards setup. So I agree that at least in principle there is room for an algorithm to perform I:E ratio adjustment such that I-time exceeds E-time. However, I don't think that's happening. I could be very wrong about that. And that's the purpose of the discussions IIRC.

snoredog wrote:

-SWS wrote: I agree that the autoSV algorithm will maintain an averaged BPM. Digital auto-track is also Respironics' leak control logic. Can you believe they dedicated an entire web domain to Digital auto-trak? http://autotrak.respironics.com/

Yes I can believe they dedicated a webpage for it, have you read it? Because this is what it says on the first page
which is all I have read in this reference (more of my selective reading I guess):

Respironics website wrote:Inside and out, the entire Flex Family of pressure relief technologies relies on two Respironics innovations: Digital Auto-Trak Sensitivity and the M Series sleep systems. Digital Auto-Trak, the brains behind all of our Flex Family pressure relief technologies, is a highly sensitive algorithm that detects the onset of inspiration
and expiration – even in the presence of mask leaks. Being able to track, react and respond to each and every breath makes it possible for C-Flex, A-Flex and Bi-Flex to deliver the right pressure relief at the right moment.
Digital Auto-Trak has the ability to recognize and compensate for unintentional and intentional leaks in the system, and to automatically adjust its variable trigger and cycle thresholds to maintain optimum performance in the presence of leaks. No manual adjustments are required.
The Digital Auto-Trak components are all active concurrently. The machine reacts to the first component that detects a change, providing maximum sensitivity.

Sorry, but I read the above to mean this machine does a very good job at finding your Inspiration and Exhale times. xFlex seems to work pretty good in finding those timings as well (not many people complain about it). So I stand behind my statement that this machine uses Digital Auto Trak to find your I:E timings in SV mode.

Yes, I had read it. But when I look at the description even now I see two things attributed to Digital Autotrak: 1) leak control, and 2) pressure management for the Flex comfort feature. The autoSV algorithm logic necessarily maintains I:E ratios, which Flex comfort features are not known to do to the best of my knowledge. I know Flex is not offered on the autoSV machine at all. And I could be very wrong, but I can't think of a machine at the moment that runs the above Flex description while also providing a backup rate. Assuming that machine does both features simultaneously, that S/T functionality may very well be in the Digital Autotrak algorithm. But yes, I read the description above, but haven't assumed yet that's where the I:E maintenance is algorithmically seated. Could be!

snoredog wrote:The idea with BPM mode is to slow your breathing down, that is what BPM=Auto does, using fixed takes it further and not only does it slow breathing down it makes it slightly uncomfortable where the body says it don't like staying there and starts breathing spontaneously again.

Snoredog stands behind the above statement too. When you enter that mode you are not breathing with a central, when you do start to breath I'm sending you back to spontaneous mode at a slower rate than you were breathing before the central occurred or the breathing that contributed to the central event.

I'm just having a hard time getting a handle on the physiology side of that. That's all. So is that description of what's happening in physiology something you explicitly read somewhere, or is that a logical interpretation of the end-result? I'm not sure if I'm reading fact or if I am reading your rationale leading to the above statement as a conclusion.

snoredog wrote: By using a ridiculously low BPM=4 when they do start spontaneous breathing again, it will be like hitting a brick wall. When they go back to SV side they will be all screwed up again with breathing.

Well, the autoSV clearly allows for SV modality to be used in conjunction with a purely spontaneous mode (BPM=off). So by the above logic Respironics sends absolutely everyone into that same physiologic brick wall who takes advantage of SV modality (maintenance of peak flow amplitudes) with backup rate turned off. By that logic Respironics would have disabled the BPM=off configuration choice whenever a clinician sets up SV (i.e. IPAPmax being higher than IPAPmin). And bear in mind that by Respironics allowing for a fluctuating IPAPpeak to occur when BPM=off, they are not targeting that fluctuating IPAPpeak for OSA. Respironics claims SV or IPAPpeak is for central dysregulation... and then they allow the machine to be set up in clinician mode with both BPM=off and SV enabled. They could have easily disallowed BPM=off in all SV configuration modes where IPAPpeak is enabled.

snoredog wrote: How can I say this nicely? As you know that is hard for me at times, so all I can say is: Don't assume you have the BPM mode totally nailed down as to its functional understanding of it, because that is where we continue to have a misunderstanding. Having that understanding is critical in the way you go about setting this machine up or correcting a particular event. There is your understanding of how it works, dsm's understanding of how it works and SAG's understanding of how it works. To be honest (and again with all due respect), neither one of you guys have gotten it right so far. ... So if your understanding is the patient is going to BPM mode because they are breathing too slow, then well you have that backwards too.

Man, you sure have come a long way in mastering this stuff since that first discussion about a month ago. And thank you for being so patient with us. I suppose it's inevitable that we will continue to interpret some details differently. I'm still under the impression that a backup rate will live up to it's name and kick in when the patient's spontaneous breathing becomes slower than the backup setting. All along I had been thinking that's what a backup rate does.

And with all due respect, I don't mean to be argumentative here about this, but for some time now there has been a clear misconception by both you and SAG (and dsm) on how this mode works. Now I realize that you guys are never wrong and try to get funny about it when someone calls you on it, but I don't blame dsm one bit for NOT understanding it either, he is only following the suggestions made by you two and well neither one of you have gotten it right to date. Sorry to be so blunt, but that is the way I see it.

That's okay. No, you can probably tell that I realize how often I am wrong when I write statements like this:

-SWS wrote:

Snoredog wrote:Like Users on this board have never been wrong before...

Well, that's an important point that I honestly think we need to emphasize again and again around here. I know I'm going to be wrong VERY often... I just never know specifically which items I'm going to be wrong about.

viewtopic.php?f=1&t=34498&p=315362#p315362

The bluntness is quite honestly okay, Snoredog. So you can see above that I expect to get things wrong. But with absolutely no sense of malice, and in that same spirit of healthy bluntness, I have to say that you have also gotten very many things wrong over the years. It's not just us. And when you have gotten them wrong, you have been about as adamant about being right as you are in this thread. Honestly, there are plenty of your old posts where you just as adamantly debate both sides of conflicting opinions throughout time. String them together as if they were quotes in a single post and you have Snoredog adamantly disagreeing with Snoredog.

So please be patient with us when you think you know that we are wrong. Because not only do we have a difficult time telling when we are wrong, but your own conflicting adamant debates on the message board over the years makes it very difficult for us to know when you are being just as right as you adamantly insist. I hear you adamantly insisting above that you are right and everyone else is wrong. But we've seen that situation work out both ways on so many occasions. Again, that was in the same well-intended vein of bluntness that you also offered.

jskinner wrote:http://james.istop.com/apnea/reports/AsvNov27.pdf

I bumped up IPAPmin last night by 3cm. Since they didn't seem to respond could those remaining events be central hypopneas? (which I don't really understand)

I did end up sleeping an usually long time at these new settings.

I could be very wrong, but I was under the impression that longer sleep might occur under either of these two circumstances:
1) improved sleep architecture triggering or commencing sleep-debt payment (a longer sleep session because of sudden sleep-debt pay-down)
2) an interrupted or less efficient sleep architecture causing a longer sleep session in an attempt to compensate for less-efficient architecture

We have seen patients repeatedly describe sleeping much longer when their apnea was not treated---and yet other patients have reported the exact opposite (meaning we're not all made the same way). And we have seen patients repeatedly describe sleeping longer once they are capable of paying back sleep debt, complements of CPAP.

-SWS wrote:
The bluntness is quite honestly okay, Snoredog. So you can see above that I expect to get things wrong. But with absolutely no sense of malice, and in that same spirit of healthy bluntness, I have to say that you have also gotten very many things wrong over the years. It's not just us. And when you have gotten them wrong, you have been about as adamant about being right as you are in this thread. Honestly, there are plenty of your old posts where you just as adamantly debate both sides of conflicting opinions throughout time. String them together as if they were quotes in a single post and you have Snoredog adamantly disagreeing with Snoredog.

So please be patient with us when you think you know that we are wrong. Because not only do we have a difficult time telling when we are wrong, but your own conflicting adamant debates on the message board over the years makes it very difficult for us to know when you are being just as right as you adamantly insist. I hear you adamantly insisting above that you are right and everyone else is wrong. But we've seen that situation work out both ways on so many occasions. Again, that was in the same well-intended vein of bluntness that you also offered.

Hey I agree with mostly everything you said except BPM being for speeding your breath up, it's the opposite. I must have ridden with Geronimo in a prior life, cause when I see us riding off towards the edge of the cliff on our ponies, I want to pull back on the reins and yell whoa you SOB!! Did you know in Apache, his name really means: "The one who yawns"

That picture and your description!


As it turns out we may not have been completely disagreeing with this part:

Hey I agree with mostly everything you said except BPM being for speeding your breath up, it's the opposite.

I currently don't view the backup BPM as being for either speeding up or slowing down. At this point in our explorations of the autoSV topic I only think it's purpose is to simply "back up a rate of spontaneous breathing"---living up to it's name.

My speeding up comment described backup BPM capability rather than intended purpose. So I still think anyone can completely subvert a backup BPM rate by simply setting it too high. So I never meant to say that's the purpose of a backup BPM. Rather, meant to say: "This is what can happen in physiology when a backup rate is set higher than its intended purpose". With that said, I am also under the impression that a clinician will occasionally need to use a T mode machine to set a fixed BPM higher than a latent or inhibited respiratory drive. There, the fixed BPM holds all pressure timing values constant (BPM in what is called T mode or PC mode)---rather than occasionally kicking in when the patient spontaneous rate falls too low (via BPM in S mode).

So what you describe about slowing down breath rate is not only possible in timed mode BPM (in my view)---but it's also what supposedly happens with the Resmed/Younnes implementation of PAV. There, what you describe supposedly happens as Resmed adjusts variable F up and down. But they supposedly revert to a standard 15 BPM backup rate when/if that doesn't pan out for various reasons.

Again, thank you for having the patience to discuss these all-too-interesting topics.

jskinner wrote:
I bumped up IPAPmin last night by 3cm. Since the hypopneas didn't seem to respond could those remaining events be central hypopneas? (which I don't really understand)

I did end up sleeping an usually long time at these new settings.

The longer sleep could account for increased events, bumping IPAP Min up by 3 cm didn't change things from prior settings that I can tell. I still think your EPAP needs to be lower at 9.0 cm. I would also like to see you work your way with BIPAP+SV mode towards 6 cm pressure support if possible. Keep in mind those therapy flags are the residual events, and yes those HI's from before are central, if they were obstructive this machine will kill them. When you find the right settings on this machine your HI indice will be 1 or less, the only residual HI's seen will be central.

And yes you are correct, those HI's are central, reason they didn't go away by increasing minimum pressure support, the PB indicators show you are still breathing too fast, follow along in the titration guide on the decision tree if you wish, but you still are having central events, you are still having hypopnea or Periodic Breathing, so we are at the center decision tree, IPAP working pressure is NOT bumping into IPAP Max, so it says lower BPM rate below Spontaneous rate (by -2), so when you look at your Respiratory Rate from that same report for Breaths Per Minute Avg. it says 14.4 (average for last night), let's round down to 14 BPM in spontaneous mode. If you follow logic behind that guide, it says to lower BPM to 2 less than spontaneous, so it is 14-2=12BPM, so if you do the math on that same 14 RR you come up with a breath duration of 4.285 seconds, half of that is about 2 seconds, so set your IT timer to 2 (IT=2.0), set Rise Time to 2 or 3.

I'd still like to see you using a minimum of 4 cm Pressure support between EPAP and IPAP Min, you really need to set that before these other items. Again, you are still too high with EPAP, you should be at 9.0, if you drop that down most of those central hypopnea will probably fall off. From what I see from the last night's report, I would use:

EPAP=9.0 cm
IPAP Min=13 cm
IPAP Max=19 cm
The above is BIPAP +SV

Set backup settings to:
BPM=12
IT=2.0
Rise Time=2 or 3, think you tried 3 before and it was uncomfortable, adjust this parameter for comfort, think you can go from 1 to 6. I'd try 2.

Snoredog wrote: I still think your EPAP needs to be lower at 9.0 cm.

EPAP=9.0 cm
IPAP Min=13 cm
IPAP Max=19 cm

Seems like we are thinking along the same lines. I had already set my machine to 20/19/12 for tonight. I will go with 13 IPAPmin instead as you suggest. Will leave BPM=Auto for tonight as I don't like to change to many settings as once as it becomes hard to tell what variable change produced the results.

Question: Does the AutoVS use square wave transitions from IPAP->EPAP->IPAP or is it more rounded like their Biflex provides?

jskinner wrote:I have been having discomfort in my lower throat for some time now. Yesterday went to see my local ENT. He scoped my throat and found a small sore spot (nodule?) on my Epiglottis. He felt this was a result of GERD.

Great something else to deal with. Have I mentioned lately that I hate Sleep Disordered breathing and everything that goes along with it

He's probably right, it would show up like many mouth sores like a canker sore in your mouth.

In the states here there is a company product line called Orajel, they make various products for mouth sores. They have a new product called Orajel Antiseptic Mouth Sore Rinse comes in a blue and white 16oz. bottle for about $5 bucks. It has a minty taste like very mild Pepto-Bismol flavor. But you rinse with it and if you get some down at the back of your throat it will attack that sore.
It contains Hydrogen-Peroxide an masks the poor taste of Peroxide. You try to keep it in you mouth for 30 to 60 seconds and spit it out.

It works very good as I though I had a similar like sore on or near my vocal cords causing its dysfunction. Couple days rinsing with that stuff and the soreness felt at the back of the throat down low went away. It will also kill any bacteria and fungus too.