Treating low grade CA with ASV

[jcp519]

While I think a higher MinPS is probably helpful, the mandatory increase to MaxPS causes my pressures to sit in the 11cm range which is simply too high for me given my OSA is resolved with <7cm.

I think you are misunderstanding how PS works. The high IPAP has nothing to do with your OSA and everything to do with combating a central apnea or hypopnea. The high PS is used in order to make you breath during a CA. EPAP is used to control your OSA so if 7 resolves those you would set your EPAP min to 7. But when you are having a central event you may need a IPAP much greater than you usual pressure in order to force you to take a breath. 

My CPAP pressure used to be somewhere around 7-8 and it would resolve all of my obstructive events. So on ASV I set my EPAP range at 7-10 to control my OSA and my PS range is 3-8 for my CAs. So if I'm not experiencing a CA and my EPAP is at 7 my IPAP would be at 10 due to the PS remaining at the minimum. As soon as I experience a CA, the PS will jump up as high as the algorithm needs in order to make me inhale. So my EPAP would remain at 7 but my IPAP could increase to 15 because my PS jumped up to 8 to combat the CA.

My point is that I need that high pressure of 15 on inhale in order for the machine to make me take a breath during a CA. This is regardless of my OSA. Its the differential of EPAP (exhale pressure) and IPAP (inhale pressure) that combats CA.

Have you tried a higher PS range of something like 3-8? I feel like having the PS min and PS max that low is just not giving the ASV enough room to help smooth out your breathing.

[tossinandturnin]

Thanks, that is actually my understanding of how it works and the way I approached it initially. The issue I have is that it doesn't behave the way I expected. I only have ~5 or so events during the night, but it seems to spend most of the time in the high pressure ranges trying to combat it. My ideal is a PS range of 0-5 and it spends most of the night at 0 - but it spent most of the night at 5.

My theory is the higher/changing pressure in turn causes treatment emergent CA, which in turn raises the pressure, etc. And this high pressure causes me difficulties sleeping and high pulse rate. I mention the OSA being resolved at 7cm because that is technically all I "need" when ignoring the induced CAs. I was trying to get the best of both worlds - a subtle nudge by the backup rate only when needed for the few CA events, but low enough pressure/changes that it doesn't induce them in the first place and then spend its time trying to treat what it caused.

I tried increasing the PS to 0.8-3.4 (attached) and sure enough the hypopnea events increased, which I assume are actually induced CA events. It seems I have a choice of increasing it even more which will induce even more CA events, but the pressure will eventually be high enough that they are forcibly fixed. Or, reducing PS to reduce induced CA events, but not have them "forcibly fixed" by the backup rate - i.e effectively simple CPAP. 

I guess that is why they only recommend ASV for CA index > 5. It's kind of like curing a sore arm by cutting it off.

I've tried the higher ranges but so far each time it has resulted in difficulty sleeping and me waking up being force fed breaths, high heart rate, etc as it climbs to pressures that are way too high for me. I do wonder if low pressure CPAP with a few CAs is the better option. I will go through my charts and periodic breathing with my Dr, but I suspect he is only interested in AHI.

[Sleeprider]

I have to wonder if you're actually getting the ASV algorithm intended by Resmed with an Airbreak CPAP.

[tossinandturnin]

I tried a PS range of 3-8 and I again had breathing issues at 2am and had to stop/start and re-ramp.

But the breathing itself is ok and supported when I am relaxed or asleep - the problem is when I am awake and start thinking about the breaths - it leads to deeper breathing which in turn makes me think it is targeting deeper breathing (even though the charts don't really suggest this), and it feels like I am spiralling into deeper and faster breaths with each one. 

Perhaps if I use a range of 3-5, 3-6, 3-7 over a period of weeks I will get more relaxed and accustomed to it like I did with regular CPAP/APAP.

It's not the airbreak firmware, it is the ASV firmware, should be 100% identical in both hardware and software (other than the PS range limit modification I made only recently).

[SarcasticDave94]

I see the point Sleeprider is trying to make. Your AutoSet that's reprogrammed to simulate the ASV is not guaranteed to act identical to the ASV from the factory. You just said you set a different PS differential than factory allows, so in this alone, this is a bit of proof it's not acting like a factory ASV.

No matter how you look at it, AirBreak was a system hack to give evidence of ability to open up the other machine types. I feel it was an experiment only. I'm not at all certain, but I don't recall AirBreak including uploading each machine type algorithm, which I'm sure ResMed isn't giving out. So if that's missing, your pseudo ASV isn't true ASV without that specific algorithm.

[tossinandturnin]

Potentially true of the airbreak modification to the autoset firmware. But if you were to take a "broken, for parts only" asv machine and take the firmware from that, verify the checksum with others, load it onto any resmed device it will be the same, except for the serial numbers baked into rom. The device is behaving as per the specification, it'd be pretty big coincidence if it worked like this with the wrong software. (The range check bypass was added by myself afterwards - it only affects the GUI validation logic).
I could switch all the hardware except PCB over to the asv instead, but that is more work and the PCB may be fried.

I'd prefer not to derail the thread with this controversial discussion which is why I blanked out the model originally.

[SarcasticDave94]

Copy that. It's your thread.

[jcp519]

I tried a PS range of 3-8 and I again had breathing issues at 2am and had to stop/start and re-ramp.

But the breathing itself is ok and supported when I am relaxed or asleep - the problem is when I am awake and start thinking about the breaths - it leads to deeper breathing which in turn makes me think it is targeting deeper breathing (even though the charts don't really suggest this), and it feels like I am spiralling into deeper and faster breaths with each one. 

Perhaps if I use a range of 3-5, 3-6, 3-7 over a period of weeks I will get more relaxed and accustomed to it like I did with regular CPAP/APAP.

This is a pretty common problem when first starting ASV. I had similar problems when I first started using ASV. I kind of just got used to it with time and now I don't event think about my breathing when I use it. I also learned to not try and resist the algorithm as it gives me breaths. I just let it do its think and help me breath. It took some time for me to be fully comfortable with it.

You could try just wearing the machine during the day and watching some TV or something with it on. The more mask time you get, the more comfortable it becomes.

I work at Philips and I know the only difference between the CPAPs and the BiPAPs is software. The same should be true of the Resmed machines as well.

[tossinandturnin]

I've been gradually narrowing in on a suitable range (ignore 7th-9th April).
Increasing the EPAP levels seems to improve my ability to tolerate the higher PS, and in turn drives up the overall pressure and improve results. My heart rate seems to have regulated itself a bit as well. Either that or I am just becoming more used to the ASV.


I originally kept my EPAP low as the literature suggested a lower EPAP was typical when on ASV, and indeed I didn't see any OSA events even with low EPAP. But it seems the range I would normally use for CPAP/APAP seems to work better. It's unclear if the higher EPAP is improving things, or the side-effect of having higher IPAP, more testing and data is required.

Would still like to explore settings that get the overall pressure lower, 14cm is double what I normally need on CPAP so seems a bit excessive. It's also causing a few leaks and noise. The 'grassy-ness' of the flow rate and minute vent also isn't as smooth as I've seen.. not sure how normal/healthy that is.

But if I can stay on this setting and result for a week or so I at least have a baseline to work against.

[SingleH]

I think you are misunderstanding how PS works. The high IPAP has nothing to do with your OSA and everything to do with combating a central apnea or hypopnea. The high PS is used in order to make you breath during a CA.

Have you tried a higher PS range of something like 3-8? I feel like having the PS min and PS max that low is just not giving the ASV enough room to help smooth out your breathing.

Hi jcp519,

Forgive my ignorance as I know very little about ASV, but trying to learn, you stated that the high PS is used in order to make you breathe during a CA. I thought that higher PS was generally a cause of CA's in people rather than a means of treating CA's, or is that just in the case of treatment emergent CA's related to starting treatment on other types of machines?

I recall seeing an article about ASV relating to a study and it also seemed to suggest better performance in addressing flow limits in patients on ASV was seen with a min PS of 4 upwards.

Also does Oscar report flow limits in the event graph on ASV machines?