Resmed VPAP Adapt SV - for Central Sleep Apnea

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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dsm
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Post by dsm » Sat Jul 22, 2006 11:44 pm

SWS,

For clarification of my question - this is the wording from the design awards link ...

'A more robust, easier to assemble, patient circuit with a single pressure sensing line that connects proximal to the mask. This improves sensitivity, minimises errors due to leaks, and allows the patient to easily detach their air circuit without disrupting the fit of their mask.'

When they mention 'A single pressure sensing line' I take that to be different from 'patient circuit' (which means the main air hose).

Proximal to mask I take to mean 'nearest to' the mask, then they state benefits of sampling 'proximal to mask' as being better sensitivity & leak detection. If I know what the pressure is at the mask & also at the air outlet orifice, Surely I have a far better ability to monitor air leakage than just attempting to do so from one source at the air outlet orifice.

That small outlet at the side really seems far too small to be a CO2 vent - IMHO if it were it would whistle

But the diags of the device do only describe the inlet vent as just that. An inlet vent. The exhaust must go somewhere.

Also the diags of the internals of the blower imply it has only one motor. Can't be certain but the two impellers appear to be on the same shaft.

DSM

xPAP and Quattro std mask (plus a pad-a-cheek anti-leak strap)

-SWS
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Post by -SWS » Sat Jul 22, 2006 11:56 pm

I most definitely agree, DSM. Based on that text description the AutoSet CS is definitely pressure-sensing at the mask. And for very good reason, too: CSR is almost always the result of congestive heart failure. If the AutoSet CS must pick off cardiac-oscillation pulse pressure waves for any reason whatsoever, then a small diameter tube leading to the mask is really the best way to go. Generally speaking, detection of cardiac oscillations through the human airway can be used to differentiate central from obstructive apneas as well. And central apnea differentiation would be extremely important to any machine tasked primarily with treating central apneas. So the small diameter tube at the mask makes a great deal of design sense here. Much more so than with xPAP machines that do not pick off cardiac oscillation pressure waves.

Re: the whistling. Wherever that adaptive exhaust port is on this machine, Resmed may or may not have felt compelled to employ edge beveling, diffusing, and/or baffling to take care of any harmonic surface-edge problems. Would just love to see one of these machines in person. Maybe even donate it to that world famous museum in Australia. .


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Post by -SWS » Sun Jul 23, 2006 12:36 am

DSM wrote:Also the diags of the internals of the blower imply it has only one motor. Can't be certain but the two impellers appear to be on the same shaft.


I'm just looking at that diagram for the first time, DSM. And I agree with your comment about appearances. I'm thinking those have to be two separate shafts (high and low) on the same geometric axis, but that they have to be mechanically decoupled to provide independent impeller rotation. Not a lot of adaptive servo advantages I can think of to rotating two impeller blades identically at far ends of the same shaft.

I don't readily see any adaptive exhaust port ventilation circuit inside the machine, either. Looking at the diagram you provided, I can see that small vent on the side is definitely where the pressure sensor line goes exactly as you had first suspected. Wonder if we can find a patent description to see what Resmed is doing with their sole proprietary version of adaptive servo ventilation---specifically by the way of exhaust venting. I'm not so sure now that these impellers are even directionally opposed. I went back to my previous post and highlighted that as being potentially wrong, pending further research/clarification.

Regardless the impeller blades have to be functionally independent and decoupled to yield any kind of ventilation benefits described by adaptive servo ventilation. This machine one day needs a DSM autopsy and that world-class description we've all come to know and love. They are absolutely great! .


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dsm
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Post by dsm » Sun Jul 23, 2006 2:33 am

SWS

I agree they *have* to be on separate shafts to make sense but if they were, as shown, there would be some interesting motor balance challenges.

All the 'brushless' motors I have looked at thus far have a counter balance weight opposing the impellers.

I could accept them being on one shaft if there was some other device that could redirect air beteen the upper & lower impeller but that adds a complication that I don't think exists. The air valve in a Respironics BiPap could do that but I am happy to accept that they have not added such complexity.

Perhaps that motor housing does contain 2 counterweights, one on each shaft. They don't have to be very thick allowing for what they tell us about the mass of the impellers.

If they have done this then all kudos to the designers. Sheer Aussie brilliance

(asuming the designer was an Aussie)

Cheers

DSM

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Post by -SWS » Sun Jul 23, 2006 8:16 am

DSM, I agree about the brilliance of this design. No matter how you slice it, these designers have come up with a "wow" design. Controlling CSR central apneas, CSDB central apneas, and mixed central apneas is, in large part, a matter of controlling CO2 kinetics. In the exceptionally lengthy Apnea -v- Hypopnea thread we can see where the Harvard researchers are accomplishing that CO2 kinetic control passively via dead space titrations.

By contrast the Resmed AutoSet CS is actively controlling CO2 kinetics via adaptive servo ventilation. However, what's very interesting about the Resmed approach, is the fact that adaptive servo ventilation techniques potentially have the inherent advantage of being able to achieve much better control over CO2 kinetic transients than stand-alone passive dead space techniques can ever achieve. And CO2 kinetic transients seem to be absolutely key with hypocapnic based central apneas. Additionally, adaptive servo ventilation techniques very likely stand to prevent at least some homeostatic CO2-target maladjustments by keeping breath and inspiratory threshold-triggers better synchronized in the first place (by achieving extraordinarily well-synchronized transient target ventilation goals). This AutoSet CS has taken quantum design leaps in the last several/couple years and I am utterly amazed at what the designers have done here. Right about now, in their own professional and social circles, I imagine they feel like genuine heroes. Much like heroes who have just come home after making an historical first landing on Mars. .


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dsm
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Post by dsm » Sun Jul 23, 2006 4:06 pm

SWS, Wow - that is quite some endorsement of what they have achieved.

On an amusing side note. About 2 months back I had the opportunity to purchase the older clunky Resmed CS model machine but by contrast to this new one, it requires a PC to interface to it to tune & set it up & that was way beyond any experimenting I wanted to do so I let it pass. The price was too high for me to purchase it just for my 'museum'

It is interesting to me to look at how both the Puritan Bennett & Resmed designs have pushed the boundaries of low cost manufacturing & simplified designs.

To this day, the blower in a PB42x range of cpaps, is an amazing reduction in the bulk of a cpap blower & I am amazed that they can deliver the air volume & reliability they seem to achieve (barring a batch produced in Mexico that caused some quality issues).

The S8 xPAPs have shown where Resmed is heading. One day I may get my hands on a Respironics M series that I can examine. From past analysis, Respironics seem content to produce rock-solid reliable conventional designs but innovate deployments (i.e. Bipap AUTO).

DSM

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Bella
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Post by Bella » Mon Jul 24, 2006 5:17 am

This machine looks and sounds interesting, but it doesn't seem to have a timed function which I need for my severe CSA.

Would that little outlet on the side be for oxygen? I read how they redesigned the interior to make it safer for oxygen use. And did you notice the care that they have taken to make sure that water from the humidifier does not get into the machine? Haven't some of the other posters had machines "die" because of this, especially when travelling?

I'd be interested in the price if anyone ever finds it. It would have to be out of pocket for me, but right now with my Synchrony S/T (which is provided free to me), I can't get much data. I think they said this one holds a years worth.


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Post by -SWS » Mon Jul 24, 2006 6:11 am

Resmed Marketing Sheet wrote:VPAP Adapt SV is an adaptive-servo ventilator designed specifically to treat central sleep apnea (CSA) in all its forms..."


Bella, based on the above Resmed statement ("...all its forms"), I wouldn't rule out a timed mode feature just yet. I know this machine has a back up rate, and it would thus seem logical to me that this machine might support a fully timed mode as well (although I could be wrong). I don't recall the fact sheet as having mentioned the details of each treatment modality. However, Resmed makes an AutoSet CS2 simulation piece of software available for clinician and DME training purposes, and that simulation software supposedly describes each machine treatment modality and its various settings.

That little port on the side is almost certainly where the small-diameter pressure sensor tube interfaces as DSM described earlier. I really don't think this machine has any sort of built in oxygen concentration feature. The standard hose/mask O2 bleed or configuration would apply with this machine if supplemental O2 were necessary.

Don't know about prices on this, but if I were going to buy one out of pocket, I'd definitely consider asking cpap.com for a price before Resmed increases Internet prices across the board very soon. I think that across-the-board Resmed Internet price increase is supposed to occur in August or September. Since this model is so new in the U.S. it may not even be available within the old and extremely attractive Internet Resmed pricing structures.

(on edit: unfortunately Resmed won't allow U.S. based vendors to ship to Canada)


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Post by Bella » Mon Jul 24, 2006 9:11 am

Right you are! The first picture I looked at was small, but then I found the product brochure and it clearly shows the small hose running between the small outlet and the maskhttp://resmed.com/Shared/StaticFiles/vp ... ochure.pdf (I don't think that I did that link correctly )

I read about the back up rate just now and it sounds like it's set at 15 breaths per minute. It does sound interesting that it deals with all kinds of CSA, because I don't know what kind I have.

Sad isn't it that with all of our concerns about ResMed's pricing "actions", some of us can still lust after their new equipment. [/u]


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Post by -SWS » Mon Jul 24, 2006 8:32 pm

DSM, thanks so very much for pointing out the impeller diagrams and making your comments. The impeller blades sit on opposite ends of the shaft toward a sole adaptive-servo objective of achieving tuned inertia. There is thus no directionally opposed impeller for the purpose of actively facilitating CO2 exhaust. That implicitly means that the AutoSet CS2 relies more on matching incrementally precise ventilatory pressures (exceptionally synchronized with respiration) to prevent CO2-based homeostatic maladjustment in the first place, than does it rely on having to compensate CO2 kinetics after inspiratory-trigger homeostatic-maladjustment has already occurred.

Or to simply summarize by comparing how the dead space and ASV techniques differ in addressing hypocapnic central apneas:

1) Additional Dead Space: does nothing to prevent CO2-based inspiratory-threshold maladjustment, but elevates CO2 kinetic retention to compensate for an already maladjusted CO2 inspiratory-trigger threshold.

2) Adaptive-Servo Ventilation: prevents CO2-based inspiratory-threshold maladjustment by avoiding typical xPAP ventilatory "overshoot", thereby often obviating the need for post-maladjustment compensation of CO2 kinetics.

Some researchers have successfully combined the dead space and ASV techniques to achieve yet additional hypocapnic based central apnea efficacy. These two techniques are not at all mutually exclusive as their respective mediatory effects occur during different stages of the maladjusted hypocapnic respiratory process.

There are very big underlying implications regarding the inherent contrasts in these two alternate yet complementary treatment methods. I will be using the above conclusions in the Apnea -v- Hypopnea thread to support a theory of CSDB as a two-stage SDB condition occurring as the result of a maladaptive homeostatic c-fiber afferent inferential relationship. This is all rather neatly piecing together in my own mind. I can't thank you enough for the diagrams and your comments, DSM.

Here is a diagram that shows adaptive-servo ventilation's very precisely synchronized delivery of minute support pressures that nicely avoid xPAP transient pressure "overshoot" to avoid CO2 homeostatic maladjustment in the first place:

Image

The above image is taken from the following medical study:
Am. J. Respir. Crit. Care Med., Volume 164, Number 4, August 2001, 614-619
Adaptive Pressure Support Servo-Ventilation:
A Novel Treatment for Cheyne-Stokes Respiration in Heart Failure

HELMUT TESCHLER, JENS DÖHRING, YOU-MING WANG, and MICHAEL BERTHON-JONES
http://ajrccm.atsjournals.org/cgi/conte ... /164/4/614


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dsm
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Post by dsm » Mon Jul 24, 2006 9:31 pm

SWS

On further looking through Resmed materials, I am wondering if they now have a new modern version of their ResScan Software.

It supprts this new machine (so its probable they have done some modernizing of it).

Perhaps at long last we can be rid of the 'clacking' floppy drive heads for those whose PCs still have one.

I can't see if they support the new S8 style data card but they do of course support the Reslink module.

DSM

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Post by Snoredog » Mon Jul 24, 2006 10:27 pm

SWS wrote:
Cheyne Stokes is probably one of the easiest central-apnea breathing patterns to algorithmically recognize.
How is that? I thought that central apnea and central Hypopnea were difficult to spot on a PSG from the other thread?

If you have a central apnea and a obstructive one they are both in absence of flow, so for a machine they look the same. Some look for irregular breathing after the event.


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Post by -SWS » Mon Jul 24, 2006 11:00 pm

Snoredog wrote:SWS wrote:
Cheyne Stokes is probably one of the easiest central-apnea breathing patterns to algorithmically recognize.


How is that? I thought that central apnea and central Hypopnea were difficult to spot on a PSG from the other thread?


1) Central apneas are very easy to spot on any PSG because of data channels corresponding to respiratory effort belts. Zero airflow plus significant inspiratory effort (reflected on the respiratory-effort channels corresponding to those belts) make for a very easy obstructive apnea score. By contrast, zero airflow plus no significant inspiratory effort makes for an equally easy central apnea score. Apneas have never presented a PSG scoring challenge unlike the following two very difficult central event types:

2) Central hypopneas versus obstructive hypopneas are virtually impossible to differentiate using standard PSG channels. That is because some respiratory effort and some diminished airflow will necessarily occur in both cases. Thus how do you easily distinguish a central hypopnea from an obstructive hypopnea on the PSG? They don't typically even attempt to make the distinction.

3) Central flow limitations versus obstructive flow limitations pose the same PSG differentiation and scoring challenges as hypopneas, for the same reasons. Once again some respiratory effort and some diminished airflow will necessarily occur in both obstructive and central etiologies. To add to the challenge, some PSG sleep labs don't routinely score flow limitations of any type.

Thus mild-to-moderate CSDB occurences have always been hiding behind the details of PSG measurement. But that just clarifies my earlier statement several posts back about PSG differentiation of less-than-frank central event types making it difficult for clinicians to have a subjective historical feel for how many mild-to-moderate CSDB cases might have crossed their paths in the past. No one will ever know until adequate clinical measurements are devised for standard PSG sleep studies.

And the above has little to do with why Cheyne Stokes Respiration (CSR) is an easy-to-recognize breathing pattern for the AutoSet CS. The primary pattern-recognition give-away for CSR is periodic breathing, which in and of itself is driven by circulatory periodicity based in chronic heart failure. Add to this highly-recognizable periodic breathing, yet another pattern-recognition clue (namely cardiac oscillations from frank central apneas occurring during zero airflow), and you have a very recognizable hypocapnic breathing pattern, indeed.

Last edited by -SWS on Mon Jul 24, 2006 11:21 pm, edited 1 time in total.

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Post by Guest » Mon Jul 24, 2006 11:19 pm

-SWS wrote:
Snoredog wrote:SWS wrote:
Cheyne Stokes is probably one of the easiest central-apnea breathing patterns to algorithmically recognize.


How is that? I thought that central apnea and central Hypopnea were difficult to spot on a PSG from the other thread?


1) Central apneas are very easy to spot on any PSG because of data channels corresponding to respiratory effort belts. Zero airflow plus significant inspiratory effort (reflected on the respiratory-effort channels corresponding to those belts) make for a very easy obstructive apnea score. By contrast, zero airflow plus no significant inspiratory effort makes for an equally easy central apnea score. Apneas have never presented a PSG scoring challenge unlike the following two very difficult central event types:

2) Central hypopneas versus obstructive hypopneas are virtually impossible to differentiate using standard PSG channels. That is because some respiratory effort and some diminished airflow will necessarily occur in both cases. Thus how do you easily distinguish a central hypopnea from an obstructive hypopnea on the PSG? They don't typically even attempt to make the distinction.

3) Central flow limitations versus obstructive flow limitations pose the same PSG differentiation and scoring challenges as hypopneas, for the same reasons. Once again some respiratory effort and some diminished airflow will necessarily occur in both obstructive and central etiologies. To add to the challenge, some PSG sleep labs don't routinely score flow limitations of any type.

Thus mild-to-moderate CSDB occurences have always been hiding behind the details of PSG measurement. But that just clarifies my earlier statement several posts back about PSG differentiation of less-than-frank central event types making it difficult for clinicians to have a subjective historical feel for how many mild-to-moderate CSDB cases might have crossed their paths in the past. No one will ever know until adequate clinical measurements are devised for standard PSG sleep studies.

And the above has little to do with why Cheyne Stokes Respiration (CSR) is an easy-to-recognize breathing pattern for the AutoSet CS. The primary pattern-recognition give-away for CSR is periodic breathing, which in and of itself is driven by circulatory periodicity based in chronic heart failure. Add to this highly-recognizable periodic breathing, yet another pattern-recognition clue (namely cardiac oscillations from frank central apneas occurring during zero airflow), and you have a very recognizable hypocapnic breathing pattern, indeed.


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Post by -SWS » Mon Jul 24, 2006 11:22 pm

Me getting guested in the middle of an edit above.

The AutoSet CS and AutoSet CS2 context-of-use is what makes the algorithm designer's job even easier. In the AutoSet CS case, the machine was only given to CSR patients. In the AutoSet CS2 case, the CSR treatment modality is selected from the LCD panel. Once a CSR patient gets an AutoSet CS or CS2, the algorithm knows precisely what type of breathing pattern to recognize and therapeutically treat based on that context-of-use. Then the clear pattern of periodic breathing and central apneas commence as being much less algorithmically challenging than certain non-CSR SDB conditions that can be highly variable and/or highly random regarding patterns. The periodicity of CSR make for very predictable patterns of necessary ventilation. The algorithm thus proatively anticipates the next "well-timed" CSR event, versus largely having to resort to being spontaneously interpretive and thus highly reactive.