Help with ASV settings

[moresleep]

What happened with EPAP Min? Did that get raised to 6 or 7cm? That's the one setting that definitely needed changed...

I set EPAP min and max to 10 this is the same as EEP 10.
PS 3 min and 15 max just like the doctor ordered.

Ok, that makes sense. But, be aware that setting EPAP min and max the same disables the auto EPAP function, which is a feature on the Respironics ASV that is not present on the Resmed ASV. You still have auto IPAP+asv. You are going to have starting Bipap values of 10/13, with the 10 held constant. Probably a good place to start. But, if you later find centrals a problem, you might lower EPAP min to 7 or 8, to take advantage of slightly lower pressures when the machine thinks that appropriate.

[jamiswolf]

Justbreathe,
No I haven't been titrated for the asv. I might have to drive to Albuquerque to have that done.

I do know what pressures manage my OSA...but the central and CS aspect is still rather an unknown.

What were your issues that required an ASV?

I have a history of serious head injury and to complicate things, I live in the mountains at 6,000' asl.

I'm looking forward to reports on how you do using asv.
Take care,
Jamis

[justbreathe]

Jamis,

I would set Epap same as bi level. Pressure support 3 min and 15 max. what did your doctor recommend?

[jamiswolf]

Hi Justbreathe,
My sleep Doc, I feel, has some basic misunderstandings about how the machine works. And he was more then willing to follow the lead of the RT...but I got my machine yesterday and wanted to try it so I just winged it.

EPAPmin 5 (I'm positional and only need low pressures on my side)

EPAPmax 10
PSmin 5
PSmax 10 I wanted to keep Max pressure capped at a pressure I know I can handle.

T started out the night at 1.8 but bumped it up to 2.3 I felt like it was cutting my inhales short.

Max pressure 20

I kept flex off

I awoke multiple times when the machine took over breathing during a central. Not from pressure but because I forgot to shut off the alarm and so the beeping aroused me. Right in a middle of dreams mostly which makes sense because my centrals have been most heavy in rem sleep.

I just woke up at 6:30 and feel pretty good. Sore dry nose but no biggie. Kept mask on all night and I feel pretty rested. I'm pleased and the rest is just tweaking.
Jamis

[JohnBFisher]

... Yes, I understand that this is a Respironics unit, but justbreathe was translating Resmed settings which is what I'm not familiar with. ...

My bad. I thought you had not realized it was a Respironics Unit. Sometimes the doctors use a prescribed settings that simply don't work for any specific machine, since a backup rate is something the Resmed machines do not do. (At least that I remember).

... I'm transitioning to a PR S1 BiPaP auto SV advanced soon...should arrive today. Too many central apneas and periodic breathing. So my interest is more then mere curiosity. ...

I thought I remembered that. Sorry to hear you need it. But I'm happy to say that most of us find our ASV machines to be very effective - once we get used to them. And the adjustment period can take a while. It seems to depend on how badly the central apneas were impacting you.

... So when functioning on the auto BiPap mode, it really only adjusts the EPAP upward to deal with OA? (always maintaining PSmin) Or is there an auto component to the IPAP as well? ...

Bingo! An auto-BiLevel machine only adjusts the EPAP to address the obstructive apneas. It does not adjust the Pressure Support that creates the IPAP value. So, if the EPAP has a minimum value of 8 and a maximum value of 12, and the Pressure Support is 4, then the current IPAP will be the value of the current EPAP plus 4.

But an ASV unit, adjusts the Pressure Support value to address central apneas. So, in addition to changing the EPAP value as needed, the machines keep an eye on the last 3 to 5 minutes of your breathing. I think the Resmed uses the last three minutes and the Respironics uses the last 5 minutes. At any rate, if the machine determines your breathing will not meet the moving average breath volume, then it will intervene and increase the pressure to increase the volume. Effectively, the machine adapts to the situation and becomes a ventilator. So, not only will the machine respond to a central apnea, it will also adapt as your breathing becomes too shallow (which often proceeds a central apnea). Due to this action, it is known as an Adaptive Servo-Ventilator (ASV) unit.

The basic theory is that central apneas tend to arise from several different factors.

The most common is due to cardiac problems. These problems seem to interfere (and/or damage) the normal chemo receptors that measure the CO2 buildup (indirectly) in the blood. The CO2 buildup normally triggers respiration. If the receptors are damaged, the buildup can increase to the point that breathing becomes shallower and shallower until a central apnea occurs. This is the undershoot side of the central apnea undershoot/overshoot cycle. After a while, the body rallies, resumes breathing and tends to trigger a bit of hyperventilation. This blows off the CO2. But unfortunately, it tends to overdo the situation. The hyperventilation tends to blow off too much CO2. This is of course the overshoot side of the undershoot/overshoot cycle. And since too much CO2 is expelled, the undershoot side of the cycles starts all over again. As you can imagine, this tends to cause the waxing and waning of the Cheyne-Stokes Respiration (CSR).

The second most common cause of central apneas is due to altitude. Essentially, as the air thins the O2 is not sufficient for some people to maintain proper respiration during sleep. Though this can be addressed by moving to a lower altitude, it can often be addressed via medication. And of course and ASV unit and/or supplemental oxygen are options.

The next most common cause of central apneas is an adverse response to the pressure of an xPAP device. Some people, in the presence of pressure some people seem to have impaired chemo receptors for the CO2 buildup. Of course, this is known as Complex Sleep Apnea Syndrome (ComplexSAS). To my knowledge, this process is not well understood at this time. However, it occurs in a significant percentage of patients who use xPAP therapy. In this instance, though older therapies included BiPAP S/T devices and/or supplemental oxygen, an ASV unit has been shown to be more effective.

A far more unlikely cause of central apneas is the use of opiates. Though this can occur within an addict of various opiates, it is more likely the optate is used to manage pain. Most doctors are VERY reluctant to take this route, due to the life threatening adverse reaction of suppression of the respiratory system. Essentially, the opiates interfere with the functioning of the brain stem, which helps regulate respiration.

The most uncommon cause of central apneas is due to a fault within the central nervous system. Typically this occurs due to some damage to the brain stem. This can either be caused by a neurological condition (these are often degenerative disorders that get worse over time) or due to trauma that resulted in damage to the brain stem, such as due to an automobile accident and/or an explosive device.

In most of these causes the Cheyne-Stokes Respiration pattern is generally not present. It tends to show up when cardiac problems (such as congestive heart failure) is present. But not always. Sometimes people just develop it without and cardiac problems.

Against all of these causes, the ASV units have proven to be an effective therapy. They tend to be most effective against standard central apneas and/or heart related issues. They tend to be least effective (and a bit trickier to tweak) against folks suffering from Complex Sleep Apnea Syndrome. The reason appears to be that the upper pressure must often be held in check to avoid adding to the problem. Thus, the respiration support of the ventilator mode is not as effective as it might be in other cases.

However, even folks with ComplexSAS find they can attain effective sleep therapy using an ASV unit. It just takes a little longer to get things tweaked.

... I'm certain I'll have more questions and it's reassuring to know friendly help is available. My Doc knows nothing about the machine and RT neither. Never set one up...small town. ...

No problem with a small town environment ... as long as they pull in the specialists when needed. I interviewed my sleep lab / DME when I went through my ASV titration. They laughed and told me that I could probably do the titration on myself, if I could be awake and asleep at the same time! Due to my neurological problems, I've had to learn a lot to try to get the most effective therapy possible.

... Justbreathe, best of luck with your new machine and thanks for undulgeing my little hijack on your thread. ...

I definitely agree with Jamis on this. Hope things go well. It was good to hear with the fixed EPAP you did better. It might take a few days/weeks for your AHI value to settle down. Essentially, I found that my body had to stop fighting the machine and work with it. But once that happens you may find a consistently lower AHI score (especially the apnea index).

Hope that long explanation helps.

[jamiswolf]

John wrote: Hope that long explanation helps

Very much so John.

I had a bad head injury 16 years ago and I also live at 6,000' asl. My CPAP treatment has been ineffective with AHIs in 20-30 range no matter what I do...plus loads of periodic breathing.

I've observed CS respirations in myself at sleep induction for years. I (and my Doc) knew I'd need a different machine but he's always slow to act.

There's a highly respected sleep clinic up in Albuquerque. I'm currently debating whether to arrange a titration session up there, It's a lovely (but long and winding) drive through the Gila national Forest. I better do it before winter comes on...
Cheers guys,
Jamis

[justbreathe]

Last night in the middle of the night I shut off the Biflex and set the rise time to 3. I don't see the point in using biflex when it is a bilevel cpap. I am thinking that setting the rise time to 3 it will give me a chance to breath on my own before the ipap kicks in.

From the manual:
• Bi-Flex - The Bi-Flex comfort feature allows you to adjust the level of air pressure relief that you feel when you
exhale during therapy. Your home care provider can enable, lock or disable this feature. When your provider
enables Bi-Flex, a level will already be set for you on the device. If this is not comfortable, you can increase or
decrease the setting. The setting of 1 provides a small amount of pressure relief, with higher numbers providing
additional relief. If the provider has disabled this feature, this setting will not display.
note: This same setting is also available under the “Setup” screen.
• Rise time - The Rise time comfort feature is the time it takes for the device to change from EPAP to IPAP. If
Rise time is prescribed for you, you can adjust the Rise time from 0 to 3 to find the setting that provides you with
the most comfort. A setting of 0 is the fastest Rise time, while 3 is the slowest. This setting will not display if your
provider has not enabled Rise time on your device.
note: This same setting is also available under the “Setup” screen.

[jamiswolf]

Justbreathe wrote: Last night in the middle of the night I shut off the Biflex and set the rise time to 3. I don't see the point in using biflex when it is a bilevel cpap. I am thinking that setting the rise time to 3 it will give me a chance to breath on my own before the ipap kicks in.

Hi JB,
I'll give you my thoughts on this for what they're worth... .

I've tried both flex on and off. With it off, the transition from IPAP to EPAP is a little more abrupt. If that abruptness starts to bother you, maybe try flex 1.

Don't know as much about rise settings except it also smooths transition as IPAP comes on.

If the machine seems to be cutting your inhalations short, my guess would be your T setting is too low. 1.8 seemed a little low for me so I bumped it up to over 2 seconds (2.3 right now). That seems to be working so far.
Jamis

edit: I may be wrong on the T setting issue...please get other viewpoints.

[JohnBFisher]

... I don't see the point in using biflex when it is a bilevel cpap. I am thinking that setting the rise time to 3 it will give me a chance to breath on my own before the ipap kicks in. ...

From the manual:

• Bi-Flex - The Bi-Flex comfort feature allows you to adjust the level of air pressure relief that you feel when you exhale during therapy. Your home care provider can enable, lock or disable this feature. When your provider enables Bi-Flex, a level will already be set for you on the device. If this is not comfortable, you can increase or decrease the setting. The setting of 1 provides a small amount of pressure relief, with higher numbers providing additional relief. If the provider has disabled this feature, this setting will not display.
• Rise time - The Rise time comfort feature is the time it takes for the device to change from EPAP to IPAP. If Rise time is prescribed for you, you can adjust the Rise time from 0 to 3 to find the setting that provides you with the most comfort. A setting of 0 is the fastest Rise time, while 3 is the slowest. This setting will not display if your provider has not enabled Rise time on your device.

Just as a note on BiFlex and Rise Time ... If there was no method to moderate the pressure, then we would experience a very squared off wave during respiration. The machine would suddenly jump from inspiration to expiration and back to inspiration as we breathe in, out, and back in ... It would be a sudden 'snap' to the pressure. It would no doubt cause some serious leaks and awakenings.

BiFlex is the method Respironics uses to try to smooth out the change in pressure. Rise Time is the method used for ventilators. And the Resmed ASV units use their EasyBreathe technology to do the same thing.

[jamiswolf]

Justbreathe wrote: Last night in the middle of the night I shut off the Biflex and set the rise time to 3. I don't see the point in using biflex when it is a bilevel cpap. I am thinking that setting the rise time to 3 it will give me a chance to breath on my own before the ipap kicks in.

Just in case you still have questions about this issue. Rise time plays no role in breath timing.

I'm going through the same thing you are...that is getting use to a very complicated machine that seems to have a mind of it's own.

The machine won't pre-empt your breathing unless your breath rate falls below the BPM rate you have your machine set at.

What your experiencing is no doubt the same as I am. You're in the middle of an inhale and the machine switches to epap. (or vice versa)

As I suggested in a post earlier...but was a little unsure of myself. I believe that changing your T (inspiration time) setting will help. It goes from 1 to 3 seconds in tenths. Mine is currently on 2.4 because I tend to breath slower and longer while sleeping.

The other issue is to try and breath smoothly. These machines trigger (from ipap to epap and back) quite easily.

If the machine senses a CA, it will breathe for you...though it does so in three increasing puffs (ending at your max pressure if you haven't resumed breathing). So I think you should be able to tell the difference between a central correction and a premature switch to ipap.

Try increasing your T setting and truthfully, I'd think about dropping the BPM rate to 10 to minimize the chance of the machine taking over breathing when you are merely breathing slow.

Jamis

[justbreathe]

After rethinking things I set back to bi-flex 3. My Ti is still 1.2 the default setting. On the bi-level I tried for a month I set the Ti to 3 and felt comfortable.

last night my AHI was high.

[jamiswolf]

JB,
One thing rise time does is to steal from tidal volume each breath. Flex doesn't do that.

Some people like those short T settings. I've been meaning to ask Mr Bill if he experiences abruptly shortened breaths...he has listed a 1 second T setting. I find the longer settings more comfortable...but since I haven't had a titration, I'm just winging it. Good luck
J

[justbreathe]

The titration will not tell you how to set the Ti. All it does is set your EPAP and IPAP with recommended BPM setting. The rest is trial and error with lots of errors.

I have never met with my sleep doctor. I have my first appointment in November. I have had three sleep studies. One was a titration for ASV.

[jamiswolf]

JB,
That surprises me...I figured you'd walk away from a titration with everything optimised. On the other hand, I had a home sleep study and was titrated via my apap machine . Nothing at all done to address centrals and periodic breathing. So I've become a skeptic.

Back to the machine...so if it is cutting your breaths short, try lengthening the Ti time. You can always turn it back. I'm using flex 3 too. Tried messing with the rise time, but found flex gave more natural breathing.
J

[justbreathe]

I am convinced that the titration is only as good as the technicians. Some are better than others and some care and some just don't care..... They are like auto mechanics. Some can diagnose and repair any problem and others are just hit and miss part changers.

The resmed ASV only has three settings. EPAP, min and mas pressure support.