ASV: HOW DOES IT WORK?

[ameriken]

Rather than answer the technical side of it, that DSM did a good job with, let me explain the WHY behind an ASV.

Basically, an ASV attempts to break the undershoot / overshoot cycle that creates Central Apneas (CA) and Cheyne-Stokes Respiration (CSR). In both cases, these start as depressed respiration. This less than ideal respiration (the waning side of CSR) causes a build up of CO2 in the blood. This is the undershoot side of the cycle. The body does not breathe as much as needed to blow off the CO2.

As the CO2 builds up, the body tends to over react. The respiration rate increases, the breathing deepens. This is the waxing side of CSR. During this over compensation, the body blows off too much CO2. This is the overshoot side of the cycle.

By blowing off too much CO2, the respiratory drive is depressed. And we start the cycle over again.

To interrupt this cycle, the ASV switches from a BiPAP (or even CPAP) to become a ventilator. In effect, if I don't breathe in a certain amount of time, the pressure increases, to inflate my lungs. Respiration occurs, even if my body is not involved in the process. Thus, the normal overcompensation that follows the undershoot side of the cycle does not occur. The cycle is broken.

So, by being an adaptive servo-ventilator ASV combines BiPAP and ventilator to meet my specific needs. And it works! My AHI is almost always less than 2. And it is normally 0 or 1. I sleep MUCH better with my ASV. Without it, I was starved for sleep and had uncontrollable high blood pressure.

Hope that helps explain WHY an ASV does what it does.

Great explanation, thanks. BTW, that 0-2 is envious. I'm jealous.

[dsm]

How does it work?
I understand how a regular CPAP machine works: it blows pressurized air past the obstruction and breathing resumes.
I don't understand the mechanism of the ASV. If my brain doesn't send a signal to breath how does the machine start my lungs pumping again?

I would like to add to John's cover by going back to this point "how does the machine start my lungs pumping again?"

Following John's points & CSR coverage, the ASV machine really can't 'force' you to breathe, but when it whacks you with an extra 10 CMs in 3 breaths, it does a pretty good job of convincing you to have a go

A mechanical pump or volume ventilator (mostly used in emergency wards) does 'force' people to breathe. That type of ventilator has a target 'volume' of flow dialed in & it just keeps ramping up the pressure until the volume has been achieved. They can add pressure way beyond our 'tiny' home machines but they also need expert supervision (& often a tracheotomy as well).

For the types of disorders we folks have, these ASV machines do the job pretty well.

DSM

#2
"it blows pressurized air past the obstruction and breathing resumes."
Also this is possibly a misunderstanding of OSA. A Cpap tries to keep the airway stented or inflated (like a sausage balloon). If the airway closes the cpap & Autopap don't try to prise the airway open. They sit still & wait for you to start breathing then they may slowly add more base pressure to stent your airway even better. OSA machines are 'reactive'. ASV's are dynamic. Breathing is always the final choice of the user.

D

[Mike6977]

Dsm:

1) Other than the cost, why isn't ASV appropriate for Obstructive Sleep Apnea Syndrome?

2) Is there any evidence that ASV can normalize insufficient SWS?

Mike

[archangle]

Dsm:

1) Other than the cost, why isn't ASV appropriate for Obstructive Sleep Apnea Syndrome?

It's potentially more disturbing to the patient than normal CPAP or bilevel.

[Dan guest]

Dsm:

1) Other than the cost, why isn't ASV appropriate for Obstructive Sleep Apnea Syndrome?

2) Is there any evidence that ASV can normalize insufficient SWS?

Mike

Mike,

I am not the best person to answer these questions as the best I can do is offer my opinions. They in turn are not backed by any medical or respiratory qualifications. If you can accept my lack of quails I am more than willing to offer opinions.

My understanding re ASV and OSA is that it is considered a no no in respiratory circles is to force air into mouth/nose to force breathing when the person has had a collapse of the tongue into the airway. I am not 100% sure of why other than wondering if doing so can do damage to the throat/respiratory tract. Rested Gal will hopefully come to my rescue on this issue.

In the case of a central (open airway central) the airway is already Stented open and thus adding 3cms increments for 3 breaths is considered safe for most people.

The ASV ramping up pressure so quickly catches the airway open and the sleeper breathing in and effectively is only increasing the volume of air flowing in in those 1-3 support breaths. But if you are hell bent on breathing out while the ASV is trying to push air in, even at it's max PS pressure, you will win. But again, you are normally asleep & rarely trying to fight the ASV machine. But it does happen

DSM

[DSM guest]

Mike

Re SWS and ASV. NotMuffy is your best hope on an answer. I haven't even got an opinion on Slow Wave Sleep & ASV other than to say I was thinking that improved SWS was a likely factor of going on ASV that got me so excitable when I 1st tried it. But I am out of my depth on the matter.

DSM

[justbreathe]

last Sunday night I was titrated with ASV. I am still waiting for the results.

If and when they tell me I need an ASV is there an ASV that I do not want to accept from the DME?

I am currently using an S9 Elite and was thinking I could use the humidifier on the new ASV but don't think it will fit from looking on cpap.com.

Thank You,
JB

[JohnBFisher]

... last Sunday night I was titrated with ASV. I am still waiting for the results. ...

Though I should probably say "Welcome to the club!", I'm not sure I would wish the need for an ASV on anyone! But the good news is that you now have options. Just about four or five years ago, ASV was not an option for anyone (at least in the US). It was not an approved therapy until then! So, the good news is that there is a very effective therapy that will hopefully help.

... If and when they tell me I need an ASV is there an ASV that I do not want to accept from the DME? ...

Either the Respironics or Resmed units work well. I have both. And both are the older "tank" models. But my own preference is the Resmed unit. Others prefer the Respironics unit. I find it easier to breathe with the Resmed unit. The Resmed unit is a lot more reactive to changes in your breathing. It tends to be quicker to enforce breathing. Since I have severe central sleep apnea that's great for me. But it does take some getting used to it.

... I am currently using an S9 Elite and was thinking I could use the humidifier on the new ASV but don't think it will fit from looking on cpap.com. ...

Well, if the DME provides an S9 VPAP Adapt unit, then you are in luck. It uses the same humidifier (the H5i humidifier). See the following "Welcome Guide" from Resmed:

http://www.resmed.com/us/assets/documen ... er_eng.pdf

Hope that helps.

[Bons]

You may not want the Respironics bipap autoSV advanced. Respironics has a new one on the market, the system one autoSV which will actually show you data without needing the smart card. Put the price of the old one down by a couple of thousand dollars, so the DME may try to get you on the older model in order to give themselves a higher profit.

[JohnBFisher]

You may not want the Respironics bipap autoSV advanced. Respironics has a new one on the market, the system one autoSV which will actually show you data without needing the smart card. Put the price of the old one down by a couple of thousand dollars, so the DME may try to get you on the older model in order to give themselves a higher profit.

Bons, that's a great point.

Either the S1 autoSV from Respironics or the S9 VPAP Adapt from Resmed. Any other ASV unit will be an older unit that you do NOT want to accept.

By the way, one advantage of Respironics over Resmed is that Respironics continues to make it possible for you to read the data from your ASV unit. With the Resmed unit you need to beg / borrow the Rescan software.

[JohnBFisher]

Dsm:

1) Other than the cost, why isn't ASV appropriate for Obstructive Sleep Apnea Syndrome?

2) Is there any evidence that ASV can normalize insufficient SWS?

Mike

Mike, think of it this way. When I cut my finger with a piece of paper, I simply don't need to go to a doctor for stitches to hold the cut together. xPAP devices are like that. Why start with just CPAP? Because there is a general principle of "the least complicated and most effective" therapy. A band aid works on the paper cut. Anything else is wasteful of costs, your time, your doctors time. And there can be unforeseen complications from the more complex therapy. Those stitches might introduce an infection. And the ASV might actually make your sleep worse. It is VERY tricky to properly titrate an ASV unit. Get it wrong and it might induce more central apneas than it cures!

Now this is just my opinion. But it's based on working with this stuff for too many years. Anyway, hope that helps.

[ameriken]

It is VERY tricky to properly titrate an ASV unit. Get it wrong and it might induce more central apneas than it cures!

Now this is just my opinion. But it's based on working with this stuff for too many years. Anyway, hope that helps.

You guys know far more about these machines than I do, but I can concur with what you say about tritration for an ASV.

At the VA I go to, they schedule 2 patients per night at the sleep lab. When I went in for my ASV titration, the other patient turned out to be a no show. The tech said the no show was a good thing because it allowed him to put more attention toward my titration. He said the same thing, it's quite tricky titrating someone for the ASV because he has to closely follow all the events and make the adjustments as the events occur. In tech speak I don't know what that means, but in laymans terms it simply means he's gotta babysit an ASV titration.

[justbreathe]

Either the S1 autoSV from Respironics or the S9 VPAP Adapt from Resmed. Any other ASV unit will be an older unit that you do NOT want to accept.

By the way, one advantage of Respironics over Resmed is that Respironics continues to make it possible for you to read the data from your ASV unit. With the Resmed unit you need to beg / borrow the Rescan software.

Since I have the humidifer I would like to stay with Resmed if possible.

I like the heated hose and ease of setting temperature.

My DME said the VPAP is not an ASV. Is this just more wrong information?

I am confused now.

[JohnBFisher]

... My DME said the VPAP is not an ASV. Is this just more wrong information? ...

Don't be confused. Your DME is almost right. The S9 VPAP is a BiLevel machine (BiPAP). But the "S9 VPAP Adapt" is an ASV machine.

Here's the link to the S9 VPAP versions (BiLevel Therapy):

http://www.resmed.com/us/products/s9_vp ... pap-s.html
http://www.resmed.com/us/products/s9_vp ... -auto.html
http://www.resmed.com/us/products/s9_vp ... ap-st.html

Here's the link to the S9 VPAP Adapt (ASV Therapy):

http://www.resmed.com/us/products/s9_vp ... adapt.html

The very first sentence in the description for that unit states:

The VPAP™ Adapt is an adaptive servo-ventilator specifically designed to treat central sleep apnea (CSA) in all its forms while providing quiet and comfortable therapy. The VPAP Adapt algorithm adapts to the patient’s ventilation needs on a breath-by-breath basis, and is synchronized to the patient’s own recent breathing rate and flow pattern to maximize comfort and compliance.

[The emphasis in the above quote is mine.]

It is quite likely your DME does not know the current Resmed product line. Hope that helps clarify the situation.

[avi123]

Are all these from Resmed also ASVs?

36004 S9 VPAP S
36006 S9 VPAP Auto
36008 S9 VPAP ST
26119 VPAP S
26101 VPAP Auto 25
26110 VPAP ST
24116 VPAP III ST-A USA
24117 VPAP III ST-A Canada and Latin America