Could AutoASV machines be used for everyone?

archangle wrote:... It appears that the hardware for the ASV is the same as the fully data capable manual CPAP machines. It's just a software difference in how you vary the fan speed in response to airflow and pressure changes. ...

Based on what data do you make that assessment??

Seriously! It's easy to toss out such a statement. But unless you see the bill of materials for the construction of an average Auto BiPAP and an ASV unit, you can not say this. It only tends to confuse everyone!

I *know* (from conversations with a Resmed engineer) that the motor and fan within the old S7 based ASV was quite different from other S7 based units. I know of no reason for that to not still be the case, since the ASV units MUST withstand much higher pressures for much longer during their run time.

It is also my understand that the blower motor for the ASV models especially the ResMed S7 very different from the standard CPAP and Auto units The S7 AVS has two motors shafts, a inter shaft and an outer shaft for quick large pressure swings. I am not sure about the blower design for the current ASV machines.

JohnBFisher wrote: I *know* (from conversations with a Resmed engineer) that the motor and fan within the old S7 based ASV was quite different from other S7 based units. I know of no reason for that to not still be the case, since the ASV units MUST withstand much higher pressures for much longer during their run time.

I distinctly recall the S7 ASV being the very first Resmed machine to have the current-generation motor and fan. That degree of fine control was necessary to accurately achieve multiple set points in the VPAP Adapt SV's pressure-delivery curve2---even back then. That motor design also made the comfortable shark-tooth pressure-delivery curve available in the non-ASV models. Thus the S8-II non-ASV machines were the next machines receiving that motor. Resmed made a BIG deal in their marketing literature back then, that the S8-II VPAP and AutoSet motors were originally developed for their VPAP Adapt SV. All S9 generation machines now use their easy-breath motor---that offers the comfortable shark-tooth pattern with low pressure-curve covariance throughout inspiration.

I can't think of why or how it would behoove Resmed to manufacture several motors when the non-ASV S9 models take advantage of the motor characteristics that were once unique to S7 ASV.

STL Mark wrote:Could AutoASV machines be used for everyone?

So help me understand what are the negatives to using this type of machine other than cost?

OSA-targeted machines are all about stenting upper-airway with static pressure. Some deliver comfort-based expiratory pressure drops (OSA-targeted BiLevel). Others deliver varying static pressure (OSA-targeted APAP). Ventilatory pressure-support (PS rather than CPAP & EPAP) is an incidental and unintended dimension of therapy for purely obstructive patients.

BiLevel machines and ASV machines that target central problems, focus primarily on delivering non-invasive ventilatory type assistance with PS and backup rates. So those are two different categories of treatment: 1) OSA-targeted machines that aim to clear upper airway obstruction with static pressure, versus 2) Central-targeted machines that aim to correct breath volume insufficiencies with PS and backup rate.

Those two categories of xPAP treatment: 1) target different patient populations, 2) look for different SDB signals & treatment benchmarks, and 3) achieve different pressure-delivery characteristics based on the SDB problem(s) requiring correction (static pressure for obstruction -vs- non-invasive ventilatory pressure for central problems). Rhetorically: if an OSA patient has upper-airway obstruction problems, but no central issues, how might ASV benefit them? I would think, theoretically, that ASV offers OSA patients no additional benefits if there are no central flow/volume problems requiring correction. Conversely, if an obstructive patient ALSO has a central issue, then ASV makes good sense IMO.

-SWS wrote:... I can't think of why or how it would behoove Resmed to manufacture several motors when the non-ASV S9 models take advantage of the motor characteristics that were once unique to S7 ASV. ...

Let me use one possible analogy of why one unit would use one type of motor and another unit would use a different motor. Remember, as you note the machines that target central apneas need to provide a more aggressive non-invasive ventilation support. There is more demand against that motor.

Now let's move to the analogy of two different cars. One is designed to be fuel efficient and eek the greatest possible "umph" out of the gas. Another is designed to drive a sports car that can and will far exceed (for quite a while) the power demands the economy car would ever need. They are both engines. They both use fuel. But they have different requirements because of the demand they will face. While you could probably make the sports car engine behave economically in the economy car, the "over engineering" of such an engine in that type of car is WAY too expensive for the demand it will face.

Another analogy is computer systems. One is a basic desktop computer. It has a power supply. But it will never face the demand that a super computer for weather forcasting would see. The power supply for that computer would be HUGE in comparison. Why? It must drive more sustained work for a longer time. It must be engineered to provide the power needs for the super computing work. That same power supply could conceivably drive that desktop computer. But it would be WAY too expensive for the desktop computer, which has nowhere near the same power needs.

So it is POSSIBLE with xPAP devices. It's POSSIBLE, and quite PLAUSIBLE, but not definite, that the various jobs require different specs for the motors. I do not know this to be certain. But not only is it possible and plausible, but as an engineer that's worked on a lot of computer, network and storage equipment, I would even say it is likely the motor specs are quite different. And the driving reason to not use the same motor would be to manufacture the least needed to get the job done. That's the most economical approach. That's the most likely approach that both Respironics and Resmed have taken. I do not KNOW this is the case. It is just likely the case.

Someone posted that inside all the machines of the same brand were the same except for the firmware. I don't remember who posted that or why but that is how rumors get started. It isn't like anyone would be willing to open up their machine to look.

What you said does make perfect sense.

Stormynights wrote:
Someone posted that inside all the machines of the same brand were the same except for the firmware. I don't remember who posted that or why but that is how rumors get started.

To help quell the rumors, if it is my post you remember, I was limiting my description to a range of PRS1 machines, 450-550-650-750. The one set of schematics covered all those machines. I don't think I'd seen a parts list though, and I suspect the motors could be different in Bi-PAP (since they go to a higher pressure range). There was a single schematic for 150-250, missing a sensor found on 450-and-higher models. I didn't see anything on the 950, so I'm assuming it is its own animal, even if it squeezes into the same case.

--SleepyCPAP

JohnBFisher wrote:

-SWS wrote:... I can't think of why or how it would behoove Resmed to manufacture several motors when the non-ASV S9 models take advantage of the motor characteristics that were once unique to S7 ASV. ...

Let me use one possible analogy of why one unit would use one type of motor and another unit would use a different motor. Remember, as you note the machines that target central apneas need to provide a more aggressive non-invasive ventilation support. There is more demand against that motor.

Now let's move to the analogy of two different cars. One is designed to be fuel efficient and eek the greatest possible "umph" out of the gas. Another is designed to drive a sports car that can and will far exceed (for quite a while) the power demands the economy car would ever need. They are both engines. They both use fuel. But they have different requirements because of the demand they will face. While you could probably make the sports car engine behave economically in the economy car, the "over engineering" of such an engine in that type of car is WAY too expensive for the demand it will face.

Another analogy is computer systems. One is a basic desktop computer. It has a power supply. But it will never face the demand that a super computer for weather forcasting would see. The power supply for that computer would be HUGE in comparison. Why? It must drive more sustained work for a longer time. It must be engineered to provide the power needs for the super computing work. That same power supply could conceivably drive that desktop computer. But it would be WAY too expensive for the desktop computer, which has nowhere near the same power needs.

So it is POSSIBLE with xPAP devices. It's POSSIBLE, and quite PLAUSIBLE, but not definite, that the various jobs require different specs for the motors. I do not know this to be certain. But not only is it possible and plausible, but as an engineer that's worked on a lot of computer, network and storage equipment, I would even say it is likely the motor specs are quite different. And the driving reason to not use the same motor would be to manufacture the least needed to get the job done. That's the most economical approach. That's the most likely approach that both Respironics and Resmed have taken. I do not KNOW this is the case. It is just likely the case.

I hear you, John. Engineer here as well. I understand and agree that some things are designed heavier-duty, simply because their duty cycle or workload is more demanding. But I don't think the stress of delivering PS 10cm or 12cm warrants a different, heavier motor compared to a VPAP or AutoSet that typically delivers a PS in the range of 3cm-to-6cm. A sneezing patient wearing a full-face mask typically creates around 50cm or 60cm water column back-pressure against an ASV or non-ASV motor. Patients impose similar peak-stress on both machine types based on inevitable coughing and sneezing. I also suspect economies-of-scale in production have resulted in the same S9 motor for ASV and non-ASV.

Rather than achieving heavier-duty cycle, I think the S7 ASV blower design was different in that it achieved these characteristics: a) decreased turbulent flow, b) maximized laminar flow, while c) offering the necessary stepped precision for Resmed ASV's multiple set-points. That last objective is key to Resmed's ASV design. An intended by-product of those design objectives happened to be a much quieter and lower-resistance blower. Brilliant design that deserved the awards it received IMO. Anyway, those same motor/blower characteristics are now utilized for all the S9 machines, since they deliver this pressure curve requiring comparatively high precision: http://www.resmed.com/us/assets/images/ ... reathe.jpg

That high-covariance S9 pressure curve (with respect to highly variable patient inspiratory curves) requires the precision born from that original S7 ASV motor...

john5757 wrote:It is also my understand that the blower motor for the ASV models especially the ResMed S7 very different from the standard CPAP and Auto units The S7 AVS has two motors shafts, a inter shaft and an outer shaft for quick large pressure swings. I am not sure about the blower design for the current ASV machines.

That two-shaft motor is no longer an ASV-exclusive build component. The entire S9 lineup---both ASV and non-ASV--- now utilizes that two-shaft design to facilitate Resmed's Easy Breathe feature:

http://www.s9morecomfort.com/s9morecomf ... etness.jpg

http://youtu.be/jSamQItyUyo

The blower motor originally designed for the S7 ASV is a classic case of new capability finding additional applications: the Easy Breathe feature in non-ASV machines.

I don't have anything constructive to post... just wanted to say I really appreciate you technical gentlemen taking the time to hash this stuff out (without bitterness or rancor, I might add). You guys make it easy for beginners like me to understand some xPAP basics. I LOVE these hard core topics! Oops, almost forgot: Kudos to Pugsy and the gals too.

JohnBFisher wrote:Completely aside from cost is that the machine is a bear to adjust to for a lot of people. Some give up completely. It is much, much easier to adjust to either a single CPAP pressure or a dual BiPAP pressure - even if the EPAP varies a bit to address obstructive apneas.

And unfortunately, cost is a big issue for lots of folks.

Hi John

Is it possible to set an ASV machine so it is only a little different from a bi-level machine and then gradually adjust the parameters to fully treat the centrals? Could this strategy ease the transition to more effective pressure swings? My mask gives me real problems at pressures above 23 or so and suddenly switching to 25 from 19 might be a serious problem.

JDS74 wrote:

JohnBFisher wrote:Completely aside from cost is that the machine is a bear to adjust to for a lot of people. Some give up completely. It is much, much easier to adjust to either a single CPAP pressure or a dual BiPAP pressure - even if the EPAP varies a bit to address obstructive apneas.

And unfortunately, cost is a big issue for lots of folks.

Hi John

Is it possible to set an ASV machine so it is only a little different from a bi-level machine and then gradually adjust the parameters to fully treat the centrals? Could this strategy ease the transition to more effective pressure swings? My mask gives me real problems at pressures above 23 or so and suddenly switching to 25 from 19 might be a serious problem.

Here's a link that may prove interesting, tho it won't answer the last part of your question. Just read down to John Fisher's replies: viewtopic.php?f=1&t=86930&p=792886&hili ... el#p792886

I knew I had read that before I bought my ASV but I couldn't find that for anything after. I finally decided that I had just imagined it. I am glad to see that link now. Should I change my setting to bipap or leave it as it is? I am really resting well and I would hate to have to change it but I don't need any more health issues. For the first time in years I am sleeping like a rock instead of feeling like I just dozed all night. I had even forgotten what it felt like until I felt it again. Please advise.

JDS74 wrote:

JohnBFisher wrote:Completely aside from cost is that the machine is a bear to adjust to for a lot of people. Some give up completely. It is much, much easier to adjust to either a single CPAP pressure or a dual BiPAP pressure - even if the EPAP varies a bit to address obstructive apneas.

And unfortunately, cost is a big issue for lots of folks.

Hi John

Is it possible to set an ASV machine so it is only a little different from a bi-level machine and then gradually adjust the parameters to fully treat the centrals? Could this strategy ease the transition to more effective pressure swings? My mask gives me real problems at pressures above 23 or so and suddenly switching to 25 from 19 might be a serious problem.

Try setting the Max Pressure to 23 .. If that works and helps you sleep, then gradually increase Max Pressure until you are comfortable with the higher pressure. Remember, the point is to get a good night sleep .. not to see if you can live with a very high pressure. If you sleep well at 23 or 24 and don't have too many wakeups due to the mask leaking and feel well in the morning .. That's the objective.

Stormynights wrote:I knew I had read that before I bought my ASV but I couldn't find that for anything after. I finally decided that I had just imagined it. I am glad to see that link now. Should I change my setting to bipap or leave it as it is? I am really resting well and I would hate to have to change it but I don't need any more health issues. For the first time in years I am sleeping like a rock instead of feeling like I just dozed all night. I had even forgotten what it felt like until I felt it again. Please advise.

Being brand new to ASV, I don't think I'd be the right person to address your questions. Leaks and high pressure discomfort can be a part of either the BiLevel or ASV experience. Both therapies can potentially generate high pressure up to 25cmH20. IMO Mask fit and adaptive strategies are very important for coping with high pressure therapy. Case in point: I have to put a flannel over my eyes to keep even tiny leaks from getting into them, and yes, I do use a Pad-a-Cheek liner.

Another angle is to consider the quantity and nature of your centrals. One more: Do you get bouts of periodic breathing? I think you can see there are lots of factors involved in such a decision. I supposed the responsible thing at this point is to ask: Are you being monitored by a sleep doctor? Have you had sleep studies? These last two thing would probably be the best course of action, of course that depends on one's insurance, medical costs etc.