Somewhat confused...AirCurve Auto, versus S, versus ST

So following up on my previous thread posted as metal36,
(viewtopic.php?f=1&t=156889&st=0&sk=t&sd=a&start=30)
I have concluded regular CPAP sucks for me and probably increases my AHI. I want a bilevel machine. I need help understanding the difference between these three ResMed units so I know what to ask for when I go see my doctor. I have 8 questions:

1) What exactly does Auto mean? Am I right that my inputs are a min EPAP, a max IPAP, and a PS? Then the objective of the algorithm is to use the lowest EPAP pressure possible which will keep the airway open on the exhale? And then the PS (Pressure Support) setting will give me an IPAP pressure of EPAP+PS=IPAP, so long as this sum is lower than the set IPAP maximum? Is that right? Nowhere is this clearly answered. This is my best guess.

2) The S unit says the required settings are two pressure levels and a “spontaneous rate”. What is “spontaneous rate”? I thought S just means it detects my inhales and outbreaths automatically?

3) What is S/T? I understand S is for spontaneous (detects my breaths). And I understand T is for time. This T is also called “backup rate”. Is that correct? The backup rate is the minimum number of breaths per minute the machine will force me to have. Right? And how does it enforce this? Like if I am not on pace to make it, will it start changing from EPAP to IPAP (and vice versa) in advance of what would happen had it waited for a spontaneous breath? I can see how that would help central apneas (which I understand to mean taking an exhale, and then just failing to take the next inhale for no obvious reason). Is this right?

4) All of these units seem to allow an EPAP as low as 3cm, which I strongly want, as discussed in the other thread. It seems the VAuto units however, when in auto mode, only allows 4cm minimum. But I don’t trust the documentation, as it seems to have discrepancies. Can anyone who owns one of these ResMed units confirm the lowest allowable EPAP setting? This is an important consideration to me.

5) Documentation I found for the S/T unit says,

The AirCurve 10 S/T has a total of five operational modes - spontaneous (S), spontaneous/timed (S/T), timed (T), VAuto and conventional CPAP mode.

Wait...what??? This has an “VAuto” mode? What is that? How is this different than the AirCurve VAuto? Seriously frustrating. Is this a typo on their part maybe?

6) The S/T unit has iVAPS algorithm, which (if I understand correctly) ensures a minimum volume of air is inhaled into the lungs with each breath. Is this right? If so, how does it do this? Perhaps it detects when my inhale is slowing down, and then forecasts that I am not going to reach the target volume, and then increases the IPAP?

And does iVAPS potentially fulfill the purpose of APAP? APAP ought to ensure that at least some air is being breathed in with each and every breath, right? It seems iVAPS would do that as well, plus furthermore guarantee the air would meet a minimum volume? Seems like there is similarity here? This would make the S/T a very versatile unit that could account for things like different pressure needs according to sleep position? Here is an example of a study with a ResMed unit that uses iVAPS:
http://onlinelibrary.wiley.com/doi/10.1 ... A4F.f04t01

7) What does “TiControl” do? This appears to be a feature on all three units. This means that the S/T unit seems to have both T (backup rate) and Ti settings simultaneously. The documentation contradicts itself. Here are some conflicting quotes from a VAuto unit sales page:

The TiControl feature on the AirCurve VAuto machine monitors the pattern of inhalation and exhalation, comparing it against the TiMax and TiMin settings on the machine. Those with respiratory disorders such as COPD or obstructive lung disease may experience early or delayed changes from inspiration to expiration, referred to as cycling. The 10 VAuto BiLevel TiControl feature is designed to prevent cycling by setting a minimum and maximum time limit on inspiration. When the machine detects the user breathing which falls outside the machine settings, it will intervene to alter the timing of the delivered IPAP (inhalation) or EPAP (exhalation) pressure.

AND

The machine is designed to monitor for instances of the inhalation time being too short or too long and compare it against the TiControl settings of the machine. The TiControl feature CANNOT be turned off when the machine is set in VAuto or S mode. TiControl can be turned off when the machine is in CPAP mode.
When the machine detects a breathing pattern which is outside of the setting parameters it responses in one of two ways:
1. If the user attempts to inhale for longer or shorter than the settings the machine will intervene by beginning the set EPAP (expiration) pressure.
2. If the user attempts to exhale for a longer or shorter time than the settings of the machine, it will intervene and begin, or deny, the IPAP (inspiration) pressure until it is called for by the settings.

Wait...what? Did you catch that? The first quote is saying these Ti parameters are checked against only the inhalation duration. But the second quote suggests the Ti parameters are checked against BOTH inhalation AND exhalation durations. Also, the second quote suggests that if your inhalation is too short, it will begin the EPAP pressure. But that wouldn’t help lengthen a short breath! So confusing.

8 ) The S unit has a Rise Time feature. I read that Rise Time is the time it takes to ramp up to the full IPAP pressure, once you start an inhale. So Rise Time should always be set to be less than TiMax. And Rise Time can only be used if Easy-Breathe is off. Easy-Breathe affects the waveform at both the start of exhalation and inhalation. Rise Time apparently only affects the waveform at the start of inhalation. I guess Rise Time screws your comfort at the start of the exhale then, since Easy-Breathe is disabled? Anyone know?

Apparently the S/T unit doesn’t have a Rise Time setting? Not that I could find anyway. I guess it would conflict with the T algorithm?

Lots of detailed questions requiring detailed answers some of which I don't know the answer so let me tackle just a few at this time.

metallikat36 wrote:Apparently the S/T unit doesn’t have a Rise Time setting? Not that I could find anyway. I guess it would conflict with the T algorithm?

I own and have used the AirCurve 10 ST. Rise time availability depends on the mode that is chosen. Some modes have it and some don't.
It is available in S mode...that I am 100% sure of because I used it and adjusted it to make the inhale/exhale timing line up more in line with my own respiration.

I don't remember what it did in Timed mode...I only briefly tested it in that mode just to see what it felt like when the machine tries to force a breath if you don't breathe...and it acts like a ventilator...it blows the air no matter if you are inhaling or not if you aren't breathing at a rate equal to whatever the backup rate settings are. So I think that answers the "how does it enforce the backup rate when in timed mode" question.

metallikat36 wrote: Documentation I found for the S/T unit says,

The AirCurve 10 S/T has a total of five operational modes - spontaneous (S), spontaneous/timed (S/T), timed (T), VAuto and conventional CPAP mode.

Wait...what??? This has an “VAuto” mode? What is that? How is this different than the AirCurve VAuto? Seriously frustrating. Is this a typo on their part maybe?

I don't know where you found that documentation but there is no auto anything on the ST machine. I know...I owned one and used one from Feb to about a month or so ago when I gave it to someone with central apnea that needed it worse than I do. There is no auto adjusting pressure mode anywhere on the AirCurve 10 ST.
It has 4 modes....cpap, S , ST and T. All are fixed pressures of some sorts with varying little differences in either timing or target volume.
No auto adjusting pressures beyond it forcing a breath if you don't breathe. Certainly not VAuto mode.

Let's back up just a bit and explain the AirCurve 10 models and what they do in general.
The main 2 Aircurve models are the S and the VAuto. Think of these as your cpap/apap machine on steroids. The main difference between them and the cpap/apap machines is that a person isn't limited to the 3 Pressure support that the typical ResMed cpap/apap offers and the bilevel pressure can go to 25 on IPAP instead of 20 on the cpap/apap models.
There's also a little more customization available in terms of how that PS kicks in by using easy breathe automatic timing or using the rise time to adjust the inhale/exhale timing.
I think that one of these machines is probably what you are looking for.
The S has 2 modes of operation... cpap and fixed bilevel. The VAuto has 3 modes available...cpap, fixed and Auto.
and your number one question...yes, you are essentially correct about auto mode....it adjusts the EPAP/IPAP in tandem as it thinks you need the pressures adjusted but PS is always the same during the adjustment.

metallikat36 wrote:2) The S unit says the required settings are two pressure levels and a “spontaneous rate”. What is “spontaneous rate”? I thought S just means it detects my inhales and outbreaths automatically?

Pretty much that is what it is...spontaneous means your own breathing vs a forced breath from the machine.
I don't know what you are talking about spontaneous rate setting in S mode. That's the mode I was using on the ST and I don't remember a special setting for "spontaneous". Easy breathe wasn't available either...only rise time so maybe that is what they are referring to.
You can set the timing of the inhale/exhale to be more in line with your own spontaneous breathing rate.

metallikat36 wrote: 4) All of these units seem to allow an EPAP as low as 3cm, which I strongly want, as discussed in the other thread. It seems the VAuto units however, when in auto mode, only allows 4cm minimum. But I don’t trust the documentation, as it seems to have discrepancies. Can anyone who owns one of these ResMed units confirm the lowest allowable EPAP setting? This is an important consideration to me.

My ST machine didn't have VAuto mode...can't say as to what the minimum EPAP available would be on the Auto mode.
You will have to wait for someone who actually owns the VAuto model to comment.

The other 2 models you mention the ST and the T are high end specialty machines designed for specific needs beyond regular OSA or pressure relief needs. Usually for central apnea or maybe used as some sort of ventilatory device to help with target volume like if someone has bad COPD or other restrictive lung disease.

Your main issues are needing exhale relief...not forced ventilation. I don't see you needing the high end specialty machines unless you have some serious lung issues going on. That would be your doctors call.
Just not being able to exhale against the perceived pressure doesn't necessarily mean that there is some sort of lung disease issue going on.

With bilevel it's the difference between inhale and exhale that offers the comfort...more difference usually makes it easier and thus more comfortable to inhale and exhale.
Your cpap/apap machine was limited to 3 EPR which is essential 3 PS.
Bilevels can offer more than 3 PS....4 is easier than 3...5 is easier than 4 and so on but there comes a point when someone can have too much PS and it can cause other breathing issues so we don't advise going wildly high with PS unless under a doctors supervision.
You might not need EPAP of 3 if you were using a machine able to give you PS of 4 or 5.

My suggestion would be target the VAuto...you may or may not need that Auto mode but it would be nice to have just in case it was needed.

Again those higher end machines I don't see you needing them unless you have some sort of lung disease complicating things and that is something your doctor should be able to help with. Having a machine force you to breath when you don't want to feels really weird. I tried it and it's plain weird and very disturbing. You don't get a choice in the matter. If you don't breathe per the backup rate setting it will make you breathe. That's what it is designed for...people with central apnea who don't breathe on their own.

Quote :
But I don’t trust the documentation, as it seems to have discrepancies. Can anyone who owns one of these ResMed units confirm the lowest allowable EPAP setting? This is an important consideration to me.


I own and use a A10 vauto ... the lowest EPAP setting is 4 cm.
It is have for me to imagine anyone with OSA to want a lower pressure than 4
I have mine set at epap 10 , ipap 16 with PS 4
I arrived at these setting with the help of several people here, No doctor involved (they told me I did not need to treat my apnea )

Not to confuse you more, but, you might read through the information on the ASV unit
I will do most of what the others will do, except will not do backup rate.
And will give more flexibility.
It would depend on your DR. and weather the insurance will pay for one.


I also have several new vauto's for sale and a couple of ST 's ... if you have to purchase one without insurance.
PM if interested

Not to rain on your parade but 2 weeks on Cpapdoes not a failure make, and in order for insurance to cover a step up to BiPAP or ASV you will need to demonstrate failure to improve on Cpap. It may be difficult to convince your doctor so soon that Cpap isn't what's needed.

RicaLynn wrote: It may be difficult to convince your doctor so soon that Cpap isn't what's needed.

It depends on the doctor. Her difficulties exhaling might get him on board sooner. I have seen people go directly to bilevel after just a handful of nights. There may be other physical issues involved here that we don't know about and the doctor will or should know about and he might be more agreeable to do it sooner than later.
It's really up to the doctor to fight the insurance company and most often if the doc words things right there isn't much opposition.
Insurance companies don't evaluate the therapy...the rely on the doc for doing that.

Good point, Pugsy. Hadn't thought about it that way.

metallikat36 wrote:1) What exactly does Auto mean?

Depends on the machine, on a resmed bilevel, it means the exact same as an autoset, except with larger difference possible between the inhale and exhale pressures. The pressure adjusts up and down in response to breathing anomalies.

metallikat36 wrote:2) The S unit says the required settings are two pressure levels and a “spontaneous rate”. What is “spontaneous rate”? I thought S just means it detects my inhales and outbreaths automatically?

No idea where you're getting a "setting" for "spontaneous rate", there is none.

metallikat36 wrote:3) What is S/T? I understand S is for spontaneous (detects my breaths). And I understand T is for time. This T is also called “backup rate”. Is that correct? The backup rate is the minimum number of breaths per minute the machine will force me to have.

The T mode switches to IPAP if you haven't initiated a breath within the timeframe referenced by the breaths per minute setting. switching to epap is controlled by your breathing, TiMin/TiMax/cycle settings.

metallikat36 wrote:4) All of these units seem to allow an EPAP as low as 3cm, which I strongly want, as discussed in the other thread. It seems the VAuto units however, when in auto mode, only allows 4cm minimum.

An epap of 4 is too low to be of use for the vast majority of people, a lower one, even less so.

metallikat36 wrote:5) Documentation I found for the S/T unit says,

The AirCurve 10 S/T has a total of five operational modes - spontaneous (S), spontaneous/timed (S/T), timed (T), VAuto and conventional CPAP mode.

That documentation is wrong, or you're mis-reading it. Also, there is no "S/T" unit from resmed, it's the Aircurve 10 ST. Respironics uses the S/T style name.

metallikat36 wrote:6) The S/T unit has iVAPS algorithm, which (if I understand correctly) ensures a minimum volume of air is inhaled into the lungs with each breath. Is this right? If so, how does it do this? Perhaps it detects when my inhale is slowing down, and then forecasts that I am not going to reach the target volume, and then increases the IPAP?

No, the AC10 ST does *not* have iVAPS. the AC10 ST-A has iVAPS. Both ASV and iVAPS use highly variable IPAP, up to 25cm/h2o for ASV and up to 30cm/h2o for iVAPS.

metallikat36 wrote:And does iVAPS potentially fulfill the purpose of APAP?

If you consider that an 18 wheeler potentially fulfills the purpose of a bicycle, then yes.

metallikat36 wrote:7) What does “TiControl” do? This appears to be a feature on all three units. This means that the S/T unit seems to have both T (backup rate) and Ti settings simultaneously. The documentation contradicts itself. Here are some conflicting quotes from a VAuto unit sales page:

You should just get the clinical manuals for the machines from apneaboard and stop reading sales pages.

I see no contradiction in what you posted.

Ticontrol is very simple: Time of Inspiration.
When a breath is triggered, the machine will stay at ipap for *at least* TiMin time, and cycle to epap at no more than TiMax time.

Thanks for the replies all:

1. My diagnosis is mild OSA. I had less than 3 AHI in my sleep studies both with and without CPAP. (Though at home, 4 nights of CPAP gave an AHI of around 9 or 10.) But I looked up my insurance authorization code, and the only criteria I meet to get coverage for OSA is that my RDI is greater than 5. I am reposting my sleep study results below:

Sleep study 1 (normal sleep):
Arousals: 7.5/hr
Respiratory-related arousals: 7.5/hr
Total apneas: 8, of which 7 were obstructive and one was central.
AI = 1.5 apneas/hr
Hypoapnea index = 0.9/hr.
AHI =2.4/hr
RERA (respiratory effect-related arousals) index = 2.1/hr
RDI (respiratory disturbance index) = 8.3/hr
mean SpO2 = 95.3%
min SpO2 = 91%
periodic limb movements: 39/hr

Sleep study 2: (titration study):
[It should be noted that in the first study, I was in a very hot room with a broken thermostat. In my general ill health, a hot room is the worst thing for my sleep quality. In this second study, I got the room with the working thermostat, and cranked it WAY down. I think that is a major reason for the improvements seen].

Arousals: 0.9/hr
Respiratory-related arousals: 0.9/hr
Total apneas: 6, of which 1 was obstructive and 5 were central.
AI = 1.1 apneas/hr
Hypoapnea index = 0.5/hr.
AHI =1.6/hr
RERA (respiratory effect-related arousals) index = 0/hr
RDI (respiratory disturbance index) = 2.6/hr
mean SpO2 = 96.1%
min SpO2 = 84%
periodic limb movements: 1.8/hr

2. My sinuses are restricted or at times obstructed. I also have very weak and shallow breathing. These I think are bigger problems than my tongue. The weak and shallow breathing is a contributor to wanting as low an EPAP as possible. But as people say, I may not need it. But I at least want that 3cm as an option to experiment with. I also feel that the bottom of my lungs are the most "efficient" in terms of giving me satisfying breaths. In other words, I don't intuitively feel that experiencing a pressure support higher up in my lungs is as good for me as experiencing the same pressure support more towards the bottom of my lungs. FYI, I have chronic infectious disease, which I believe includes the lungs.

2. My insurance authorization code says "Dream Station Auto CPAP ...[other stuff]". I think this code already approves both CPAP and APAP devices.

3.

grayghost4 wrote:I own and use a A10 vauto ... the lowest EPAP setting is 4 cm.

Could you possibly take the trouble to confirm that when in S mode the EPAP can go down to 3cm?

4.

xxyzx wrote:Why does cpap increase your AHI? Why would a bipap be different? What part of the AHI is an issue? OA, hypops, or centrals ?

One note is that the EPAP may be causing central apneas, as I think my two sleep studies suggest. Another thought is that maybe the apnea events are spurious? The sleep technician probably censors spurious events. Or maybe the CPAP is more sensitive in detecting apneas than the methods used in the sleep lab? Maybe both simultaneously? One other possibility is that when I sleep prone, the pillow presses on the nasal pillow, and impacts my sinuses. But I spent some time prone during the titration study as well.

My sleep stages didn't change much with and without CPAP in my sleep studies. For example, I spent 62.3% in stage N2 without CPAP and 69% in stage N2 with CPAP. As I mentioned, the HOT room seriously confounded my sleep studies. I was hot without the CPAP. And with the benefit of both the CPAP and the cold room, sleep stages still didn't change much. What I think happened is that the cold room made me sleep more deeply, but the CPAP made me sleep less deeply, and the two effects cancelled out. Actually, this could explain why I didn't have an increased AHI in the titration study as well. When I am hot, my nasal restriction is definitely worse. Perhaps it's the darn cold room that did it, masking the harm of the CPAP. God, you would think a sleep specialist of all people would have a working thermostat.

Why would bipap be different? I think the EPAP causes me to not sleep deeply. I think there are quality of sleep issues that are not directly apnea related. Longer, smoother, deeper, less restricted breaths I think could make a difference for me. I do notice that quality of breathing has a lot to do with mental activity and being able to get past the feeling of being "wired" and unable to sleep (which my infectious disease does to me). The greater pressure support would also potentially allow me to tolerate a higher IPAP setting (either through auto or through S mode) which would allow me to better overcome the issues of sleeping prone and pressing on the pillow.

After reading everyone'e replies I am inclined to ask my doc for the AirCurve VAuto. It can do everything my current CPAP does, so I have nothing to lose, and likely something to gain.

grayghost4 wrote:
I own and use a A10 vauto ... the lowest EPAP setting is 4 cm.


Could you possibly take the trouble to confirm that when in S mode the EPAP can go down to 3cm?


Yes in S mode it does go down to 3

Pugsy wrote:

RicaLynn wrote: It may be difficult to convince your doctor so soon that Cpap isn't what's needed.

It depends on the doctor. Her difficulties exhaling might get him on board sooner. I have seen people go directly to bilevel after just a handful of nights. There may be other physical issues involved here that we don't know about and the doctor will or should know about and he might be more agreeable to do it sooner than later.
It's really up to the doctor to fight the insurance company and most often if the doc words things right there isn't much opposition.
Insurance companies don't evaluate the therapy...the rely on the doc for doing that.

It was my Sleep Doctor who recommended another Sleep Study with the idea that I might do better on BiPap than on my AutoSet.

Did Sleep Study & it indeed did show that (to my surprise).

Sleep Doctor Rx'd a ResMed AirCurve 10 VAUTO ("I" specified the ResMed & Auto).
Took Rx to DME who filled it.
Medicare & my secondary BC/BS approved it without any resistance whatsoever - i.e. no fight whatsoever.

My S9 AutoSet will be 5 years old in Feb, 2018.