A Potential Downside of ASV? Down the ASV Rabbit Hole.

[Geer1]

I didn't want to derail Katie's thread with this so figured I would create a new thread.

ASV has some very clear advantages even for people that don't suffer from central apneas. The biggest thing that impressed me about ASV was actually how it deals with flow limitations by correcting and offsetting them on the next breaths. For those that don't know ASV works to maintain minute volume so if your breathing is reduced for a few breaths it will work to help you take breaths to offset those bad breaths.

The one potential downside that I was wondering about was how ASV works as a ventilator and whether or not the body could become reliant on it. This came to mind because my sleep therapist refused to sell me a bilevel, his reasoning was because all bilevels have backup rates and I don't have any diseases or complex sleep apnea etc that requires a machine with backup rate. For the record this is false information and many bilevels including the VAuto that I am interested in do not have backup rates, it is kind of scary that a "professional" in the industry didn't seem to be aware of this...

When I did a quick bit of research on this I found research aimed more on mechanical ventilation and found that prolonged use can create reliance and weak lungs. I don't think ASV would be as bad as more dedicated ventilators but it still does a lot of work to keep you breathing (enough to offset periods where your brain doesn't think it needs to breath and would otherwise have caused a central apnea) and it made me wonder if this is still something your body could possibly become reliant on.

A bit of googling found this poor example indicating that ASV does indeed create less long term issues then mechanical ventilation (in pigs at least lol).

https://www.ncbi.nlm.nih.gov/pmc/articl ... c1-13title

Jung et al.[30] conducted a study with healthy pigs and compared the effects of ASV versus controlled ventilation in vivo and in vitro in terms of the effects these modes could have on diaphragm muscle. They concluded that ASV protects the diaphragm against the deleterious effects of prolonged mechanical ventilation and also helps maintain an adequate contraction of the diaphragm as demonstrated by measurements of transdiaphragmatic pressure and phrenic nerve conduction.

I then found this article that discusses using ASV to help wean people off of mechanical ventilator dependence.

https://www.hamilton-medical.com/en_AE/ ... 3747~.html

Then I found the following article which gets into the nitty gritty on how ASV works, pretty neat with lots of good information although fairly technical. In it they also made reference to using ASV to wean people off of mechanical ventilators.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3701392/

So in the end I still haven't found a definitive answer as to whether or not ASV can create some reliance which is the only downside I can really think of. It clearly does not have reliance issues like mechanical ventilation does though and considering it is used for weaning people off that equipment it seems that if there is reliance it is minimal enough that people can overcome it on their own.

If anyone has some experience/thoughts about this or knows of other studies on this I would be interested to see them. Learning more about ASV technology has made me realize just how neat and capable this equipment is, the question is whether it is something everyone with SDB would benefit from it or whether there are enough potential downsides that it should only really be used by people that need its true benefits (being able to treat central apneas etc).

[Pugsy]

Maybe....big maybe....if someone used ASV 24/7 for months and months and months the body might become physically reliant on it to help breathe. Awful big maybe in my book. I can't see it happening to anyone unless they already had some very serious neuro muscular type of problems.

Remember ASV only kicks in that back up rate big breath if there is a physical need for it (like a no breathing central apnea)....it won't do anything in terms of the back up rate if no centrals happen...it essentially functions like any auto adjusting cpap/bilevel/apap machine depending on the setting parameters. Those type of machines don't seem to cause a physical dependency.

And it only does its job while we are asleep and the rest of the day we are totally on our own in terms of those muscles used for breathing.
At least 2/3 of the time we aren't using the machine and the body's muscles are doing their normal work load and I just don't see much chance of any weakening happening unless something really unusual is going on physically.

Price and the hurdles to jump over to get ASV are the biggest downside IMHO.
Even that old questionable study done that scared the hell out of heart failure patients using ASV is now being looked at in a different light so I don't even count it.

I have been on some form of cpap for ever 10 years now. I breathe just fine on my own during the day.
Even when I was using ASV (and I think it was for about 3 years) I had no problems breathing on my own during the day.

[Geer1]

Remember ASV only kicks in that back up rate big breath if there is a physical need for it (like a no breathing central apnea)....it won't do anything in terms of the back up rate if no centrals happen...it essentially functions like any auto adjusting cpap/bilevel/apap machine depending on the setting parameters. Those type of machines don't seem to cause a physical dependency.

One very different function compared to CPAP/Bilevel/APAP is how it works to maintain minute volume. CPAP/Bilevel/APAP machines don't care if you are only struggling somewhat to breath, in fact the auto machines require it in order to react and do their job. ASV on the other hand works to make sure you are breathing as well as it believes you should be based on the data you enter into it. If you have a single flow limited breath it is going to work a bit harder to pump some extra air into you on following breaths. Multiple bad breaths, it works even harder. Still reactive but rather than just reacting and adjusting to try and minimize future events it is also trying to compensate for those past bad breaths as well. To me that seems like a fairly substantial difference.

I don't see even the slightest chance of ventilator dependency as in not able to breath on your own (during the day etc). I am just curious about the smaller details on the sleep side of things. I have even wondered the same thing about APAP/Bilevel use, does using these machines make your body more dependent on them? Without treatment our body tries to compensate for SDB on its own, it teaches us to mouth breath, avoid certain positions, alert us and create leg twitches to try and manipulate us out of bad positions etc. Learning and compensating that I am guessing your body loses after it is on even a basic CPAP machine that is negating the SDB, or is it like riding a bike and your body remembers how to try and best deal with SDB fairly quickly when it returns? ASV seems the same to me but I wonder if it can also have extra effects due to the compensation it provides.

[Pugsy]

I think you are overthinking just how the ASV actually works.
You are doing a pretty good job of making mountains out of molehills yourself.

You can't really change minute vent with ASV settings. Now there are some bilevels with backup rates where target volume and ventilation specific settings can be forced on someone but not with ASV.

[palerider]

ASV on the other hand works to make sure you are breathing as well as it believes you should be based on the data you enter into it.

No, no it doesn't.

And let's not even TALK about *VAPS machines.

If you have a single flow limited breath it is going to work a bit harder to pump some extra air into you on following breaths.

Go back and do some reading on what ASV machines do, what they look for, what they respond to, how they operate, because you're way off base.

[palerider]

I think you are overthinking just how the ASV actually works.
You are doing a pretty good job of making mountains out of molehills yourself.

But, but, but, he's an enjunear!

[TropicalDiver]

I have even wondered the same thing about APAP/Bilevel use, does using these machines make your body more dependent on them? Without treatment our body tries to compensate for SDB on its own, it teaches us to mouth breath, avoid certain positions, alert us and create leg twitches to try and manipulate us out of bad positions etc. Learning and compensating that I am guessing your body loses after it is on even a basic CPAP machine that is negating the SDB, or is it like riding a bike and your body remembers how to try and best deal with SDB fairly quickly when it returns? ASV seems the same to me but I wonder if it can also have extra effects due to the compensation it provides.

While I appreciate the abstract intellectual nature of your argument, the answer is irrelevant. Yes, the body does employ various methods to try and mitigate the impacts of serious health issues. The body begins to excrete high amounts of glucose directly in urine with uncontrolled diabetes. Those with pulmonary insufficiency will often begin to hunch their shoulders when breathing. In certain circumstances the body will reduce blood flow to the extremities. I have had a conversations with someone whose 02 sats were in the low 60s and another who had an insanely low hcrit. In all of those instances, medical interventions are needed -- and until they happen the body is incurring significant (and potentially fatal) damage. So it is with SDB; while the body does what it can damage is still occurring.

Part of the reactions to SDB are likely autonomic (not a medical pro -- so speculation on my part). But this what bother me: this same argument is essentially what is used by some to avoid supplemental O2 -- I will become dependent on it. Hypoxia is bad for you and needs treatment!

If someone benefits from PAP therapy, why would it matter even if there was some almost insignificant reduction in the ability of their body to cope with untreated apnea? You could, umm, just continue treating the apnea!

A silly analogy: Without glasses, I have 20 400 vision. I have developed a number of strategies (including a certain squint) that allow me to get by (lets say 20 350). I get a pair of glasses -- and can see 20 20. Should I be worried about being dependent on the glasses? Perhaps I should ditch the glasses and return to the much worse vision because if I use glasses for some period of time -- and then stop -- some of my old strategies might not work as well>? (Or I could just use my glasses during the day and enjoy 20 20 vision all of the time!) And I could make the exact same argument with a prosthesis or...

[palerider]

But this what bother me: this same argument is essentially what is used by some to avoid supplemental O2 -- I will become dependent on it. Hypoxia is bad for you and needs treatment!

The same type of idiots don't want to use cpap because "they'll become 'dependent' on it".

If someone benefits from PAP therapy, why would it matter even if there was some almost insignificant reduction in the ability of their body to cope with untreated apnea? You could, umm, just continue treating the apnea!

A silly analogy: Without glasses, I have 20 400 vision. I have developed a number of strategies (including a certain squint) that allow me to get by (lets say 20 350). I get a pair of glasses -- and can see 20 20. Should I be worried about being dependent on the glasses? Perhaps I should ditch the glasses and return to the much worse vision because if I use glasses for some period of time -- and then stop -- some of my old strategies might not work as well>? (Or I could just use my glasses during the day and enjoy 20 20 vision all of the time!) And I could make the exact same argument with a prosthesis or...

HAH, I was about to make a comment comparing pap use to glasses, then i read the next paragraph.

[Geer1]

I think you are overthinking just how the ASV actually works.
You are doing a pretty good job of making mountains out of molehills yourself.

You can't really change minute vent with ASV settings. Now there are some bilevels with backup rates where target volume and ventilation specific settings can be forced on someone but not with ASV.

All ASV's target maintaining minute vent, that is literally how they work. If minute vent goes up, PS decreases, if minute vent goes down PS increases. Here is literature from Resmed confirming that is in fact how the Aircurve 10 ASV works.

https://www.resmed.com/us/dam/documents ... er_eng.pdf

To successfully treat central apneas and periodic breathing, the AirCurve 10 ASV constantly monitors the patient’s breathing pattern and minute ventilation, and automatically adjusts pressure support to break the cycle of hyperventilation and central events that occur.

A decrease in minute ventilation is rapidly treated by increasing Pressure Support

Pressure Support decreases as minute ventilation returns to target

It took me a while but I finally found how the Aircurve 10 ASV determines a target minute vent, gotta say it is pretty smart for the application and it takes out some of the ventilator worries as it clearly isn't a ventilator unlike the ASV technology being discussed in the articles I posted earlier. Same basis but a neat spin on the technology to make it better for this specific application.

https://onlinestore.resmed.com/images/p ... 017278.pdf

ResMed’s unique ASV algorithm uses minute ventilation as the target since this is the most direct measure of patient breathing, enabling the most timely interventions to normalize breathing quickly. The algorithm continually monitors and learns the patient’s recent minute ventilation (tidal volume x respiratory rate) and then sets a target at 90% of this value. The algorithm then automatically adjusts the pressure support to meet that target. Patients receive the minimum pressure support (a setting prescribed by the physician) whenever they’re breathing at or above this target – such as would occur in normal breathing or hyperpnea (over-breathing). If the patient’s instantaneous ventilation decreases away from the target, then pressure support is rapidly increased to bring ventilation back to the target. During this time, pressure support may be automatically increased up to the maximum pressure support value (as prescribed by the physician). In the absence of spontaneous effort, such as in a CSA event, the device inserts breaths at the patient’s recent respiratory rate. This rate may gradually move toward a fixed backup rate of 15 bpm if the algorithm is unable to get ventilation up to the target using the maximum pressure support and the patient’s recent rate.

The auto-adjusting pressure support (the difference between inspiratory pressure) is provided on top of a manually adjusted EPAP in ResMed’s original ASV therapy mode. The EPAP setting is titrated in a sleep lab to a value that keeps the patient’s upper airway open (just like with a CPAP device). In ResMed’s ASVAuto mode, EPAP is automatically adjusted by the device algorithm in response to flow limitation, snore and obstructive apneas in proportion to the severity of the event (like with ResMed’s AutoSet therapy). This algorithm predicts the onset of airway collapse by detecting and assessing the flow shape of each breath, increasing EPAP in response to flow limitation, and detecting and responding to snoring. During obstructive events, instantaneous ventilation decreases away from the target and pressure support is increased in response. The algorithm monitors how minute ventilation responds to the increased pressure support, and if there is little or no flow during this period, it deduces that the airway is obstructed. Once breathing resumes, EPAP is increased to prevent the occurrence of further obstructive apneas. The EPAP range used by the algorithm can be restricted with the Min and Max EPAP settings. Once breathing is stabilized, EPAP gradually decreases towards the minimum EPAP setting, for comfort, over a 20- to 40- minute period depending on the type of event that occurred.

[palerider]

I think you are overthinking just how the ASV actually works.
You are doing a pretty good job of making mountains out of molehills yourself.

You can't really change minute vent with ASV settings. Now there are some bilevels with backup rates where target volume and ventilation specific settings can be forced on someone but not with ASV.

All ASV's target maintaining minute vent, that is literally how they work.
blah blah blah blah

Pugsy is *RIGHT*, and you completely missed it.

You can't really change minute vent with ASV settings.

Properly stated: "You can't change minute vent with ASV settings."

[raisedfist]

Mechanical Ventilation is designed to completely take over the work of breathing, which is why it can lead to muscular atrophy should prolonged use occur.

ASV is based off your spontaneous breathing so it should not lead to atrophy even if used 24/7. Your breathing muscles are active the entire time while on ASV. Devices that augment or maintain your ventilation all still involve the patient spontaneously breathing therefore no dependence or real weakness should occur.

[Pugsy]

There's a big difference between maintaining normal breathing and changing normal breathing (ventilation) via settings forcing a change from normal breathing to some specific ventilation settings artificially.

I thought you were talking about changing via setting alterations. ASV can't do that.
Now figuring out your own particular breathing which is normal for you and helping maintain that....yeah...ASV does do that.
That's the beauty of it.
If someone doesn't or can't maintain adequate ventilation or breathing then they have issues going on that ASV isn't designed to deal with and instead there are other choices in bilevel models that can and will do that.

Babydino was right....engineers over think everything way too much.
I am done here. You asked for opinions and you got mine. Then you argued with me.
When you have been on cpap over 10 years and actually used ASV for over 3 years....then maybe I might be more in the mood to argue a bit.

[palerider]

Babydino was right....engineers over think everything way too much.
I am done here. You asked for opinions and you got mine. Then you argued with me.
When you have been on cpap over 10 years and actually used ASV for over 3 years....then maybe I might be more in the mood to argue a bit.

Has anybody figured out what kind of 'enjunear' that one is? does it involve overalls, a cap and a remote control for the toy train set?

[squid13]

There's a song About A Helluva Engineer.

[Geer1]

Babydino was right....engineers over think everything way too much.
I am done here. You asked for opinions and you got mine. Then you argued with me.

Be glad your brain doesn't work like mine. This stuff drives me more nuts then it does you guys trying to understand where I am coming from... Unfortunately my brain doesn't just let me accept that something works, it needs to know why and how. I can see the smallest details that don't make sense and until I find the information that sets the light switch off it is painful, I literally couldn't sleep last night until I found those details...

In this case I wasn't sure that I agreed with your statement that almost everyone should be on ASV, that is why I started this thread and as mentioned in the beginning a big part of that was because I had a medical professional tell me I shouldn't even be using a more basic machine that doesn't even do a fraction of what these ASV units do... I still don't know that I would go as far to say everyone should use ASV but I do not think they have as significant a downside as I thought might be possible.

I wasn't trying to argue. I was trying to understand what actually makes these machines safe for anybody to use. In this case I got stuck on a wrong path and was googling ASV ventilation and was thinking that is what these machines provide. In the beginning I didn't know how the target minute vent was calculated, I just knew the machine worked to maintain minute vent and there are potential downsides of that. I couldn't find a clinical manual and I wondered if height was an input that was being used to calculate minute vent (I saw it is an input for IVAPS). Once I realized how the minute vent target was determined it was clear that they are handicapping the machine in a clever way, I now believe that any issue with using these machines due to their backup rate and minute vent compensation would be minor. One of the coolest things is actually the ASVauto mode as the increasing EPAP determined by breath flow form (apnea, flow limitation and snore) is what makes these machines actually try and target an ideal minute ventilation rather than just allowing your minute vent to slowly decrease as flow limitations get worse and worse. Pretty smart programming and I am glad to finally understand how it works.