Help with ASV Experience/Settings, coming from BiPAP ST

[SimbaLion]

Gotcha, thanks for all the suggestions. I guess my problem is that the BiPAP pressure used to be 4 on exhale, which is actually below anything on the ASV (in or out!). Is it dangerous to deviate so much from that 4...if I set PS to 3 or 4, won't my effective lower bound be ~9?

[SimbaLion]

Oh wait, I think I'm mixing things up. If I set PS to 3 or 4, then I'm closer to a bipap of 9/5 if it never ramps up. PS of 3 or 4 won't increase the exhalation pressure, right?

I *THINK* I'm finally getting used to the terminology.

[DeepBreathing]

EPAP = Expiration pressure - the pressure you're breathing out against
IPAP = Inspiration pressure - the pressure when you're breathing in
PS = Pressure support - the additional pressure which helps you inhale.

EPAP + PS = IPAP

The EPAP needs to be high enough to sustain your airway against obstructions, but low enough that you can easily exhale. The IPAP needs to be high enough so that you can inhale and get sufficient air into your lungs. (And if you have an apnea it needs to be high enough to get you breathing again). If EPAP is set low and PS starts at zero, then IPAP will also be low, which is probably why you're having trouble inhaling. Your previous machine had a very large pressure support, so you are used to that big kick of air when you inhale.

Changing EPAP won't make any difference to inhaling, it's the IPAP (and hence PS) which control your inhalation.

[SimbaLion]

Got it, I'll try changing PS Min to 3 and see if that makes enough of a difference in the inhalation. I'm kinda surprised my doc set me up basically a constant pressure of 5 to begin with...that is below even what I started as a min with CPAP.

[vsheline]

I'll try changing PS Min to 3 and see if that makes enough of a difference in the inhalation.

Since you are accustomed to sleeping with PS of 11, on your ASV machine I think you'll probably be most comfortable with Min PS of 4 or higher.

With ResMed ASV machines, Min PS and Max PS cannot be set to the same pressure. In fact, Max PS must be at least 5 higher than Min PS. If Min PS is 5 then the Max PS must be at least 10.

On a ResMed ASV machine, the highest Min PS can be set is 6. If Min PS were raised to 6, Max PS would have to be raised to at least 11.

ResMed redesigned their website a couple years ago to be more sales oriented and dropped a lot of information from their website. It used to say something to the effect that, for a person with normal lungs a PS as high as 10 would be sufficient to do just about all the work of breathing for us.

You are used to an unchanging PS of 11. That means the BiPAP may have been doing just about all the work of breathing for you, with no effort needed by you, except to speed things up a little when you initiated inhalations on your own faster than the backup rate for breaths per minute.

To me, using a PS of 11 constantly all night seems alarmingly high. With such a large PS all night, I think it is possible your BiPAP may have been slightly poisoning you with too much Oxygen, unless you have a lung condition which makes makes your lungs harder to inflate than for most people.

Did you ever wear a recording pulse oximeter all night, when your PS was 11?

I think a good target for SpO2 (the Saturation percentage of Oxygen in the blood, as measured percutaneously, meaning measured through the skin) is between 94 and 96 for most people with healthy lungs. However, many COPD patients are easily harmed by too much O2 in their blood and probably should target 88%–92%.

I think an average SpO2 of 98 to 99 all night may be harmful, causing too much oxidation in our system. Continuous high SpO2 can reduce the effectiveness of some medicines and can cause oxidative stress, which would gradually lead to health problems.

"administer oxygen to keep saturations between 94 and 96 percent. No patient needs oxygen saturations above 97 percent and in truth, there is little to no evidence suggesting any clinical benefit of oxygen saturations above 90 percent in any patient."
http://www.ems1.com/columnists/mike-mcev...xygen-hurt

"For most COPD patients, a target saturation range of 88%–92% will avoid the risks of hypoxia and hypercapnia."
https://psnet.ahrq.gov/webmm/case/172

http://www.emsworld.com/article/10915304...uch-oxygen

Take care,
--- Vaughn

[palerider]

With ResMed ASV machines, Min PS and Max PS cannot be the same pressure. In fact, Max PS must be at least 5 higher than Min PS. If Min PS is 5 then the Max PS must be at least 10.

On a ResMed ASV, the highest Min PS can be set is 6. If Min PS were raised to 6, Max PS would have to be raised to at least 11.

I *believe* this to be in error. though I don't have one in front of me at the moment to test with.

the manual states that maxps can be 5-20, not minps+5 to 20.

To me, using a PS of 11 constantly all night seems alarmingly high. With such a large PS all night, I think it is possible your BiPAP may have been slightly poisoning you with too much Oxygen, unless you have a lung condition which makes makes your lungs stiffer and harder to inflate than for most people.

agreed. it's like hyperventilating you all night long. that might be part of why the backup rate was so low.

[DeepBreathing]

With ResMed ASV machines, Min PS and Max PS cannot be the same pressure. In fact, Max PS must be at least 5 higher than Min PS. If Min PS is 5 then the Max PS must be at least 10.

On a ResMed ASV, the highest Min PS can be set is 6. If Min PS were raised to 6, Max PS would have to be raised to at least 11.

I *believe* this to be in error. though I don't have one in front of me at the moment to test with.

the manual states that maxps can be 5-20, not minps+5 to 20.

I believe Vaughan's right. I just checked on my S9 VPAP Adapt and it will not accept a PSMax less than 5 higher than PSMin. I assume the Aircurve is the same. So while the manual states that PSMax can be 5 - 20, it can only be 5 if PSMin is set to zero.

The manual also recommends that PSMax >= 15.

[SimbaLion]

That's very interesting info.

So the backup rate was 8 when I first started bipap st a few months ago (this was from the titration study). I noticed that my spontaneously triggered breaths was only 25%, which was disturbing to me. I asked my doctor and he set my backup rate back down to 6 (not 7 as I had originally remembered) and my triggered breaths went up to 50%.

So the concerns about the machine basically "breathing for me" mirrored my concerns as well.

I still felt "not rested" on the ST and asked for an ASV machine and the doctor was pretty accommodating.

So I guess it's good that I'm on ASV now because it seems like my in/out difference isn't as large anymore! And hopefully I get better sleep! And not getting over-oxygenated?

[vsheline]

The manual also recommends that PSMax >= 15.

Not needed by most patients, I think. And pity the new ASV patient trying to get some sleep, whose doctor or respiratory therapist blindly follows this new ResMed guideline.

ResMed engineers and doctors may be thinking PS won't go that high unless needed. Instead, I think every time we swallow the ASV algorithm would think we are having an apnea and may shoot the PS up to its limit, perhaps causing noisy leak, air swallowing, or just generally bothering the patient unnecessarily.

[SimbaLion]

So a quick update -- I am feeling a LOT better on the ASV than I was on the BiPap ST. I still get a bit sleepy sometimes, but I think that's due to just "regular" rhythms than what I was experiencing on the BiPap. So nine months into my CPAP --> BiPAP ST --> ASV journey, I'm in a good place! YAY!

Also, my AHI journey: 72 --> 25 (CPAP) --> 10 (BiPAP ST 13/4) --> 4 (BiPAP 15/4) --> .3 (!!!) to 2 on the ASV.