Resmed VPAP Adapt SV - for Central Sleep Apnea

[Liam1965]

P.S. You look pretty ert to me, Liam.

You're WAY too subtle for me. I had to go back and read my previous messages before I got this one.



Liam, who was incognito until the airlines finally rebooked his canceled flight home.

[-SWS]

Also, I've been speaking a lot about what SAG'd do for you, without even asking him. LOL!!! He might just say, "Yeah, yeah... here, dude, take a number, sit down, and wait. RG who?"

Absurd! SAG would never ask anyone to take a number. Last time I was at his sleep lab he told me to draw a straw to see whether I got a bed. SAG does not believe in using numbers!

Liam, you would absolutely love SAG's sense of humor and I'm positive he would enjoy yours as well.

disclaimer: I have never actually been to SAG's sleep lab. He made me draw straws via the U.S. postal system. To his credit he never even suggested that I should take a number. I still keep my unlucky souvenir straw on my nightstand as a reminder of what might have been. I can clearly remember calling in my losing straw-length measurement to this day. Darn how I hate to lose straw lotteries... even improvised ones!







.

[-SWS]

then we have to ask, "OK, AdaptSV has all this great information from proximal pressure, what did it actually do with it?"

In order to match up on a "breath-by-breath basis", the pressure signal has to pass through the proximal pressure line (takes some time), be analyzed by the microprocessor (OK, electricity travels pretty fast), the flow generator must respond, and then the resultant flow/pressure has to get out to the patient. Now I know time is relative, but a lot of stuff has to happen here.

So let's superimpose the 2 signals:



and now ask, "Did AdaptSV really do anything different with proximal airway pressure data?"

I would like to offer the following rationale taken from another post on the same sub-topic of ASV proximal sensor line:

Okay. Let's take a quick peek at why that added sensitivity offered by the proximal sensor line is important to the ASV algorithm. First let's review text from the ASV Fact Sheet (with an emphasis on the underlined parts):

To determine the degree of pressure support needed, the ASV
algorithm continuously calculates a target ventilation. Based on
respiratory rate and tidal volume, the target is 90% of the
patient’s recent average ventilation—that means that ventilation
can vary gradually and naturally over the course of the night.

The algorithm uses three factors to achieve synchronization
between pressure support and the patient’s breathing.
1. The patient’s own recent average respiratory rate—including
the ratio of inspiration to expiration and the length of any
expiratory pause.
2. The instantaneous direction, magnitude, and rate of change of
the patient’s airflow, which are measured at a series of set
points during each breath.
3. A backup respiratory rate of 15 breaths per minute.

To ensure ventilatory support is synchronized to the patient’s effort,
the VPAP Adapt SV relies on factors one and two. When a central
apnea/hypopnea occurs, support initially continues to reflect the
patient’s recent breathing pattern. However, as the apnea/hypopnea
persists, the device increasingly uses the backup respiratory rate.

From the above disclosure we know that the ASV algorithm relies heavily on measuring and comparing set points with respect to instantaneous direction, magnitude, and rate of change. Now that's what the ASV algorithm does by design. So please don't confuse that disclosure with the issue of whether SAG approves or disapproves of those algorithmic steps, or which Resmed employee SAG thinks released that information to the public.

The ASV algorithm is comparing a series of reference points that look something like this:


Now here's a nice chart recently posted by SAG that shows significant degradation of a flow signal measured at the machine (flow2) compared with that same patient flow signal more accurately measured at the mask (flow1):


So the left two signal humps look similar because they are comprised largely of machine effort rather than human effort. But look at those right two humps. They differ quite a bit. The top hump in particular, flow1, is comprised from significant human inspiratory effort. That top hump much better reflects human inspiratory instantaneous direction, magnitude, and rate of change that the ASV algorithm relies on for its comparative calculations.

It's human inspiratory effort that the ASV tries to accurately baseline, compare, and correct on an as-needed basis. And if you're working with a series of flow-curve reference point comparisons (minute volume) and your algorithm is design-bound to compare those points, then the top signal via a proximal sensor line is really what you want---because signal processing itself manages to retain many more of those crucial comparison reference points. Now if your algorithm endeavors to slide respiration rate (also known as patient-variable "F") back and forth, preservation of those signal processing sample points becomes even more mathematically crucial.

So let's take yet another look at that bottom-right signal hump labeled flow2. It's flat. How is the ASV algorithm going to determine its top-most three crucial reference points with that signal source? Now sample at the mask with a proximal sensor line and you get that more-suitable top-right signal hump labeled flow1. With that signal source the ASV algorithm can now more readily ascertain samples for its three top-most reference points (in order of appearance): 1) early mid-inspiration, 2)peak flow (top- and center-most reference point), as well as 3) late mid-inspiration. Some of the other reference points now sample and signal-process more accurately as well. You can see how this reference-point-driven ASV algorithm really needs that extra transient-signal sensitivity achieved via a proximal sensor line at the mask.

By contrast Respironics compares only peak flow (the top of each signal hump). And unlike Resmed, Respironics does not attempt to adjust patient-variable "F" (Respironics only endeavors to back up respiration).That means no need to compare instantaneous direction or rate of change of the flow curve itself. That also means no need for a proximal sensor line in the Respironics case. As a side note, fixed or constant impedance can be algorithmically baselined without a proximal sensor line--very satisfactorily. Narrow-diameter proximal sensor lines are always about increasing sensitivity to dynamics or transients embedded in a signal stream.

Thanks to SAG who originally provided us with the above Resmed text and two graphs.

The above post was offered in this thread:
viewtopic.php?t=29016

The patent description additionally delineates the concept of the above discrete reference point comparisons. Each of those discrete reference points are compared against an equivalent discrete reference target (each target reference point is recent-average derived). Each discrete reference point comparison in turn influences instantaneous impeller rotation toward pressure support that is intended to: 1) either influence or alternately maintain instantaneous or discrete volume, and 2) influence or maintain patient-variable "F".

It is the succession of these instantaneous or discrete measurements and impeller actions which collectively account for both minute volume measurements and continuous volume targets. In other words, many discrete reference and target points are strung together to comprise a continuous target volume and even respiration rate (patient-variable "F").

However, the proximal sensor line at the mask makes it possible for the Resmed algorithm to sample and signal-process all the necessary reference points (not endeavored by Respironics).

[jammin]

Hi Folks,

I haven't posted anything in quite awhile but something came up with my sleep doctor this week and I just wanted to know if I'm the only one having this experience.

I've been diagnosed with complex apnea, and my untreated oxygen saturation falls to around 66% during the night. I've been on the Adapt SV for a year now. I get good very good results when the doctor checks the data on the smart card. Overall, I've adjusted fairly well to dealing with the machine, except for one thing. Aside from the apnea I'm a fit and trim fairly active guy, but for some reason I have an extraordinarily slow respiration rate - about six breaths per minute when I'm relaxing. The Adapt SV forces me to breathe at a minimum rate of 12, and if I start having a central event I think it goes up to 15 - the default rate. Anytime I'm awake I feel like it's pushing me - it starts a new breath well before I naturally would. It's somewhat disconcerting, you could even call it a bit discomforting.

When I saw the doc last week I told her and she said she'd have the sleep lab manager try to adjust the backup rate. I brought in my machine and the manager called his Resmed rep and asked what to do. When he told her what I was asking for, and what my resting respiration rate was, she asked if I was extremely ill or what? He confirmed that, no, I appeared in very good health but was an unusually slow breather. She said that the machine has no adjustments that would accommodate me. The call ended with no solution and the lab manager said I might be better off trying the Respironics Auto SV, which he thought would adjust to my rate.

It's bad enough to be diagnosed with complex apnea (5 polysomnograms have all agreed) but now I just feel flat out weird. I never had overt symptoms of sleep apnea but I was experiencing some heart rhythm issues, and my caregivers all concluded that the root cause was the apnea, which is why I got a polysomnogram in the first place. Now it seems that on top of that, I breathe half as often as the average dude, and the ASV just isn't into that.

Any thoughts?

[Banned]

Your'e a mile high on 6 breathes a minute? Could that be a reason for the low O2? I'm sure you've done this little experiment a allot: Deliberately breathe normally (at your 6 breathes a minute) and try to force the machine to slow-down to your breathing rate. The machine will do allot of Epap/ipap switching, (kind of like bronc-riding in the mask). Or, some people do breathing exercises, but I'm not sure if that is to speed-up or slow-down their breathing. If that drives you crazy get the Respironics BiPAP Auto SV. And snap an O2 line into your mask when you get a chance?

Banned

[jammin]

Hi Banned.

Yes, I've often tried to get the machine to slow down for me, and you're right - it does a lot of switching, and if anything ends up speeding up. The doc originally prescribed an added O2 line with a Respironic BiPAP, but I talked her into letting me try the Adapt SV, and the data indicated that I didn't need O2 as long as I was on this machine. When I'm awake my O2 readings stay around 93%. I think that what happens is that when I'm asleep I occasionally just stop making an effort for an extended time, and that's when it falls so badly. The doc said she had seen tons more cases of central and complex apnea at this altitude, compared to the clinic she was previously at in Chicago. We're exploring the possibility of getting a test for me at sea level. I think my DME is going to let me try the Respironics BiPAP Auto SV soon. That should be a telling experience.

[dsm]

[quote="jammin"]Hi Folks,

I haven't posted anything in quite awhile but something came up with my sleep doctor this week and I just wanted to know if I'm the only one having this experience.

I've been diagnosed with complex apnea, and my untreated oxygen saturation falls to around 66% during the night. I've been on the Adapt SV for a year now. I get good very good results when the doctor checks the data on the smart card. Overall, I've adjusted fairly well to dealing with the machine, except for one thing. Aside from the apnea I'm a fit and trim fairly active guy, but for some reason I have an extraordinarily slow respiration rate - about six breaths per minute when I'm relaxing. The Adapt SV forces me to breathe at a minimum rate of 12, and if I start having a central event I think it goes up to 15 - the default rate. Anytime I'm awake I feel like it's pushing me - it starts a new breath well before I naturally would. It's somewhat disconcerting, you could even call it a bit discomforting.

When I saw the doc last week I told her and she said she'd have the sleep lab manager try to adjust the backup rate. I brought in my machine and the manager called his Resmed rep and asked what to do. When he told her what I was asking for, and what my resting respiration rate was, she asked if I was extremely ill or what? He confirmed that, no, I appeared in very good health but was an unusually slow breather. She said that the machine has no adjustments that would accommodate me. The call ended with no solution and the lab manager said I might be better off trying the Respironics Auto SV, which he thought would adjust to my rate.

It's bad enough to be diagnosed with complex apnea (5 polysomnograms have all agreed) but now I just feel flat out weird. I never had overt symptoms of sleep apnea but I was experiencing some heart rhythm issues, and my caregivers all concluded that the root cause was the apnea, which is why I got a polysomnogram in the first place. Now it seems that on top of that, I breathe half as often as the average dude, and the ASV just isn't into that.

Any thoughts?

[rested gal]

jammin, that was very interesting what your doctor said about seeing many more cases of complex sleep apnea at high altitude Denver than when she was practicing in Chicago.

Hope you get some smoother treatment going soon. Good luck!!

[ozij]

http://www.mayoclinic.org/central-sleep ... types.html

High-altitude periodic breathing
Caused by sleeping at altitudes higher than 15,000 feet, and may possibly occur in some individuals at lower elevations. Breathing pattern resembles increases and decreases of Cheyne-Stokes pattern but with a shorter cycle time. Doesn't usually require treatment and breathing returns to normal upon return to lower altitude.

O.

[jammin]

Thanks to all of you for the advice and insights. Today the DME gave me a Respironics Auto SV to try out for a week. I tried it for a bit after work and at first glance it seems to be more natural feeling to me. I'll report back after I have tried it a few times. It's doubtful my insurance will go for it after they finally purchased the Adapt SV, but at least I'll have some new knowledge.

[mluciano]

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[MrSandman]

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