Varying AHI Readings on BiPap Auto SV Advanced

JIMCHI wrote:I made the adjustments Banned suggested for last night:
Pres Max 22
EPAP Min 8
EPAP Max 12
PS Min 5
PS Max 10 (Note: raising PS Max from 7 to 10)
BPM Auto
Flex (Off)

The AHI this morning registered a 7. One of the better numbers I have had. The chart of the Patient Triggered Breaths was also the smoothest of the 5 weeks I have been charting it. The average was 98.2% with little variation, while most of the previous nights had periods when it dropped to 70-75%.

Any additional tweek you want me to try tonight?

Way to go, JIMCHI...

Can I suggest posting last night's graph so we can see how high/low your pressure rode both during and in between events?

OK- here it is. Hope I posted it the right way this time.

Average PS was formerly 5. You THEN changed PS min to 5 and better addressed those hypopneas. Last night's average PS was 6. What does that suggest about a possible experimental change to make next?

P.S. Your new, improved patient trigger rate suggests improved ventilation IMO...

Increase PS MIN to 6 ??

JIMCHI wrote:Increase PS MIN to 6 ??

That's one possible experiment---especially if you suspect those residual hypopneas are primary obstructive or primary central hypopneas. However, if you suspect those might be EPAP-based iatrogenic hypopneas, then experimentally lowering EPAP min would be an alternate experiment.

As a side note, the lower you allow PS min, the more control you give the algorithm to treat your hypopneas. The higher you set PS min, the less control you grant the algorithm. That latter strategy of granting the algorithm less control matches what many people on this message board have to do with their ordinary APAP machines. It would be wonderful if PAP algorithms always did what they endeavor... But they clearly don't.

I have had poor results when I have lowered the EPAP Min. I did that just the other day at someone's suggestion (set min at 6 and max at 12) and had an AHI of 18, one of my highest and also felt tired. I also tried an EPAP min of 6 a few weeks ago and felt terrible the next day. So, eliminating that, my next best adjustment would be to increase the PS Min to 6 and that's all ? Or would it be better just to leave everything the way it was last night and let's see if I can get two consistent results, without the AHI going to some large number tonight? The big problem has been the variances. So the fact that I had an AHI of 7 last night could well mean nothing and I could have 17 tonight, all things remaining the same.

-SWS wrote:

JIMCHI wrote:Increase PS MIN to 6 ??

That's one possible experiment---especially if you suspect those residual hypopneas are primary obstructive or primary central hypopneas. However, if you suspect those might be EPAP-based iatrogenic hypopneas, then experimentally lowering EPAP min would be an alternate experiment.

Assuming "..residual hypopneas are primary obstructive or primary central hypopneas", tonights settings should be:

Pres Max 25 (Note: Even though your graph does not necessarily warrant this change, P Max should be 25. Never exceed P Max 25 with this device)
EPAP Min 8
EPAP Max 12
PS Min 6
PS Max 13 (Note: Raising PS Max from 10 to 13)
BPM Auto
Flex (Off)

-SWS wrote:As a side note, the lower you allow PS min, the more control you give the algorithm to treat your hypopneas. The higher you set PS min, the less control you grant the algorithm. That latter strategy of granting the algorithm less control matches what many people on this message board have to do with their ordinary APAP machines. It would be wonderful if PAP algorithms always did what they endeavor... But they clearly don't.

I thought the general consensus of the sleep medicine community is that the optimal spread from EPAP to IPAP is 4cmH20 and above?

Banned,
Interesting discussion. Is "pressure support" on this blower sort of the same thing as IPAP on the Encore Viewer output?

Mr Bill wrote:Banned,
Interesting discussion. Is "pressure support" on this blower sort of the same thing as IPAP on the Encore Viewer output?

Pressure Support on this device is the difference between EPAP and IPAP, as I believe SWS or J.Fisher said earlier.
So yes, you are partially correct, that it is sort of the same thing as IPAP on the Encore Viewer output.. sort of.

JIMCHI wrote:I have had poor results when I have lowered the EPAP Min. I did that just the other day at someone's suggestion (set min at 6 and max at 12) and had an AHI of 18, one of my highest and also felt tired. I also tried an EPAP min of 6 a few weeks ago and felt terrible the next day. So, eliminating that, my next best adjustment would be to increase the PS Min to 6 and that's all ? Or would it be better just to leave everything the way it was last night and let's see if I can get two consistent results, without the AHI going to some large number tonight? The big problem has been the variances. So the fact that I had an AHI of 7 last night could well mean nothing and I could have 17 tonight, all things remaining the same.

Leaving the settings the way they are sounds smart to me, JIMCHI. That way you can tell your doctor tomorrow exactly what your are up to... You can also test these settings another night toward discerning either consistent or variable results as you mentioned.

After that, setting PS min@ 6 would probably be my next experiment if it were me----pending doctor approval, of course. However, I wouldn't rule out eventually experimenting by also lower EPAP min----for comparison---after you find your best PS min. It's entirely possible that you have experienced some mix of both "primary" residual hypopneas and machine-induced or "iatrogenic" central hypopneas. That, in turn, implies that there may be an optimal trade-off/combination of EPAP min and PS min to thoroughly explore. So once you have PS behaving optimally, EPAP min MIGHT turn out to sit at some new optimal value that is lower. IMHO combinatorial experimentation with those two parameters beats basic deductive reasoning.

So in summary, I think PS adjustments are probably your key to treating those excessive residual hyponeas; but optimal EPAP min MIGHT change along the way as a matter of combinatorial effect on respiratory-drive.

Banned wrote:I thought the general consensus of the sleep medicine community is that the optimal spread from EPAP to IPAP is 4cmH20 and above?

Yes. Consensus suggests that standard BiLevel titrations manually fix PS somewhere between 4cm and 10cm: http://www.aasmnet.org/Resources/Clinic ... 040210.pdf

But bear in mind we're not manually setting a constant PS here. And what AASM recommends for a standard BiLevel machine is actually different than what Respironics suggests PS min toward setting base modality on BiPAP autoSV. Respironics recommends PS min initially set at at 0 (CPAP modality)---with BiLevel kicking in on an as-needed basis. Throughout the night, that recommended autoSV setting alternates between delivering CPAP, then BiLevel, then CPAP, and so forth. Anyway, some CompSAS patients probably fare better with CPAP as ASV's base modality (setting PS min =0) and others probably fare better with BiLevel as ASV's base modality (setting PS min > 0).

JIMCHI, so far you have tried the first three of these four treatment modalities: 1) CPAP, 2) BiLevel, 3) ASV w/ BiLevel as base modality, and 4) ASV w/ CPAP as base modality. I would encourage you to consider eventually comparing those last two modalities----rather than assuming past trials with modalities one and two (CPAP and BiLevel respectively) can yield definitive conclusions about WHICH of those last two ASV modalities is your best bet. As it stands I'd bet modality three is your best choice. But if it were me, I'd eventually get around to running at least a one-night trial of modality four---ASV w/ CPAP as base---for the sake of comparison. There's a reason Respironics defaults that as their first choice during titration for either generation of their BiPAP autoSV machines. My understanding is that CPAP as ASV's base modality is inherently less destabilizing for some CompSAS patients---otherwise it wouldn't be Respironics' first-choice during their ASV model-specific titrations. (note: in reality the EPAP-min through EPAP-max range on the Advanced model implies APAP as base modality; setting EPAP-min to equal EPAP-max gets the Advanced model back down to true CPAP as base modality)

Above all else, I'd be sure to get my medical team in the loop and listen very carefully to what they suggest. Again, good luck.

Banned wrote:

JIMCHI wrote: One of my sleep studies indicated I did well at an EEP of 6. I did try an EPAP of 6 (min & max) on this new machine one night and I felt awful the next day, even though my AHI was 13. What do you think of my trying setting the EPAP min at 6..

CPAP and EPAP 6 and below, are non-settings.
Anybody with a CPAP or EPAP of 6 and below doesn't need CPAP therapy

With respect, that's just not true.

My ASV is set for an EPAP of 6, a MinIPAP of 10 and a MaxIPAP of 14. It was initially set for an EPAP of 10, and I could not, could NOT breathe out against it -- and it triggered apneas, as well as sending my leak rate through the roof. Once my EPAP was lowered to where I could breathe out, I was fine, and almost never have an AHI over 2, mostly 1.

OK- will leave settings from last night. I need to see if some stability in these AHI numbers can be achieved.

I just know the doctor is going to want yet another (will be my 4th in 7 years) sleep study. Would I be out of line in resisting this ? I just feel that another sleep study is once again only going to capture a tiny bit of widely varying data. If it worked so well, I would have had the proper settings from the start. As far as I can recall, the sleep labs have to use a special machine (not just mine) to do studies and titrations. What good is it going to do if they use some other brand or model of machine. My insurance company has already invested many thousands of dollars into sleep studies, doctor fees for interpretations, and CPAP/VPAP machines and supplies, plus my co-pays. I just think there must be a smarter way of titrating me and I'm thinking at home with my machine over many nights makes the most sense - if that's possible and a doctor will work with me.

The doctor I see tomorrow is my pulmonary (moderate asthma) guy. He's not the sleep specialist in that pulmonary/critical care office. Whether he will make recommendations or just refer me again to the sleep specialist I don't know. Looking at my recent performance, I don't think the sleep specialist ever fully addressed all my issues. He is board certified in sleep medicine, but given my Complex Apnea I'm wondering if I might be better off seeing a sleep specialist who is also a neurologist.

Any thoughts as to whether I should make a stand about another sleep study interpreted by the same sleep specialist?

I would want to get at least three nights' data, preferably more, before deciding on what change to make next. -SWS and Banned have both given helpful advice here.

One thing I am wondering about is the basic difference between the BiPAP ASV and the VPAP adapt SV. The BiPAP machines try to keep ventilation constant based on a sliding four minute window. The VPAP machine's goal is to maintain a constant minute ventilation, that is pretty much a fixed value. This might be more appropriate for a person with troublesome hypopnas, and may explain why your therapy results between the two machines differ so much.

timbalionguy wrote:I would want to get at least three nights' data, preferably more, before deciding on what change to make next.

That's EXCELLENT advice IMO in light of JIMCHI's issue of high hypopnea-index variability.

That comment about variability reminds me... JIMCHI, I'd suggest trying to keep as eye on sleep position if at all possible. Supine sleeping can exacerbate your obstructive component while side sleeping can exacerbate your central component. As it turns out, one or the other might be more destabilizing for you.

timbalionguy wrote: One thing I am wondering about is the basic difference between the BiPAP ASV and the VPAP adapt SV. The BiPAP machines try to keep ventilation constant based on a sliding four minute window. The VPAP machine's goal is to maintain a constant minute ventilation, that is pretty much a fixed value.

Someone please correct me if I'm wrong. But I believe the Respironics BiPAP autoSV uses a sliding four-minute window to average and then target peak flow---whereas the Resmed VPAP adaptSV uses a sliding three-minute window to average and then target minute volume instead. Similar but different, with neither maintaining a constant flow target per se. But TLG's point is well taken in that these two models can sometimes yield different treatment results depending on which subtly different approach works---or doesn't work---for any given patient.

I can't really control sleep positions. Amazingly, I sleep quite well so I'm not aware of what goes on during the night. The few times I've been aware, I've been on my back or on right side.

Any thoughts on what I should do if he wants another sleep study?