ASV: HOW DOES IT WORK?

[JohnBFisher]

... The "Pressure hump" that you mention is correlated with an hypopnea (shown by the Flow in the lower panel) and I wonder why the pressure was boosted? ...

Remember, the ASV keeps track of the volume of air we breathe. If the unit anticipates that we will fall short of the moving 3 minute average, then it will boost the pressure to increase the respiration. It's not unusual to have a hypopnea after a central apnea. The machine detects that we will fall short and kicks the pressure up again to maintain respiration.

As LittleRedTruck noted (thanks for the great graph), though it would seem these pressure swings are disruptive, in comparison to not breathing it is not at all disruptive. In fact, you learn to trust the unit will be there. It's not a respirator. It does not have to be. It does not have to act as an AVAPS unit that pushes past chronic obstructive pulmonary disease (COPD). Nor does it have to maintain respiration for a long time. MOST of the time the unit acts as a BiLevel unit for us. But every now and again, it notes we need a bit more and adapts to help support respiration.

Hope that helps.

[LittleRedTruck]

I sleep very peacefully knowing the Adapt SV is there doing its job. I think its wonderful the machine responds to a Hypopnea, if indeed it was. I only had 2 hyponea the whole nite. So I think the machine is knocking them down. They were the only events I had all nite long. I only showed 2 traces so I could clearly show the interaction of flow reduction and pressure bumps to maintain my overall flow rate . How the ASV functions. Ive showed 4 graphs in the past to make a point, but invariably some member like Avi123 will choose to complicate the information making the point totally lost in the confusion. So 2 is all you get ! Dan

[JohnBFisher]

... I sleep very peacefully knowing the Adapt SV is there doing its job. ...

Amen!

... I think its wonderful the machine responds to a Hypopnea, if indeed it was. ...

Not really. It was just responding to the fact that your respiration (the volume of air) would fall below that 3 minute moving average. Of course, that's what a hypopnea is by definition. Not enough air. So, since you were going to fall short, it responded.

... I only had 2 hyponea the whole nite. So I think the machine is knocking them down. They were the only events I had all nite long. ...

Yup. That's pretty much my experience most nights. Due to my neurological symptoms, some nights are really bad, but most are like yours. This therapy is literally a lifesaver for me.

... How the ASV functions. Ive showed 4 graphs in the past to make a point, but invariably some member like Avi123 will choose to complicate the information making the point totally lost in the confusion. So 2 is all you get ! Dan

I prefer to think that avi123 is just trying to understand how and why an ASV unit works and why it is there instead of a respirator. Clearly a respirator is an option for someone with central sleep apnea. In fact, it would have been one of the few options for someone with severe central sleep apnea, if oxygen and/or an S/T unit did not do the trick.

Thanks for sharing those graphs. I had wondered what information the S9 ASV would reveal. My interest is more than academic, since my older Resmed ASV unit is trying to die on me.

[avi123]

Thanks John Fisher for the explanation and also for your posts about the ResScan graphs from your ASV machine here:

viewtopic.php?f=1&t=48778&st=0&sk=t&sd= ... can+graphs

[dsm]

Avi,

Were you ever in a Yeshiva ? - if yes I'll bet you liked the chavrutas aspect & also that you could & would have no trouble debating "how many angels dance on the head of a pin"

Your interest in sdb is obvious. If you ask a question of anyone, try to spell out exactly what it is you are asking. Be prepared to make mistakes, *and* acknowledge them. Then if you alter your original post, have the courtesy to list at the bottom what you changed. Not doing that makes people nervous about responding as we need to be confident what we are responding to. If you learn something, say so at that time. There are many members who are willing to answer questions and each may provide a different perspective, you can take away the ones you value.

Most of us respect & value genuine learning & those willing to do so and those willing to pass on expertise & understanding & real life experience. Each has its value & can come from a wide variety of cpap users here. This applies equally be it our own learning (believe me that is ongoing in SDB) or others learning.

DSM

[avi123]

thanks, dsm

[Roger2]

Timed breaths. The machine calculates your average breathing rate over a period of time (4 minutes, I believe for the PRS1 ASV). If you fail to breathe according to that rate, the machine will initiate a breath for you.

-A

Do all machines have this or just the more deluxe ones? I have a ResMed S9 Elite, does that have this capability?

I had not heard of this term before but then I have only been on cpap therapy for about 2 months so I am sure there is a LOT more that I am unfamiliar with.

Roger

[JohnBFisher]

Timed breaths. The machine calculates your average breathing rate over a period of time (4 minutes, I believe for the PRS1 ASV). If you fail to breathe according to that rate, the machine will initiate a breath for you.

-A

Do all machines have this or just the more deluxe ones? I have a ResMed S9 Elite, does that have this capability?

I had not heard of this term before but then I have only been on cpap therapy for about 2 months so I am sure there is a LOT more that I am unfamiliar with.

Roger

Greetings Roger2! Welcome to the Hose Head World!

The machine you have does not do this. There are several different Positive Airway Pressure therapies:

• CPAP Therapy - The continuous PAP. What you use.
• BiPAP (or Bi-Level) Therapy - The inhalation pressure is greater than exhalation pressure. This makes it easier to exhale against the Positive Airway Pressure.
• BiPAP S/T Therapy - Your breathing is timed. If you fail to breathe often enough the machine kicks switches to inhalation pressure in an attempt to "remind" you to breathe.
• ASV Therapy - This is usually a Bi-Level machine with ventilation support. adipasqu was off a little bit in the definition. Rather than just tracking the frequency of your breathing, an ASV machine tracks the volume of air that you breathe. If you next breath falls below the moving 3 (or 4 ... depending on the manufacturer) minute average, then the machine will increase the pressure to assist respiration. That's why it is known as Adaptive Servo-Ventilation (ASV) therapy.

There are other therapies. For example there is AVAPS, which helps people with Chronic Obstructive Pulmonary Disease (COPD). And no doubt more will be developed.

The ASV therapy is used to treat central sleep apnea in its various forms. There are two primary reasons why central sleep apnea occurs.

First, you might have a physiological problem that interferes with regulation of CO2 in the blood. This often happens with heart failure, which can lead to Cheyne-Stokes Respiration (CSR) and central sleep apnea. The brain is doing its job, but the mechanism to regulate CO2 is "broken". By acting as a respirator, the ASV helps break the undershoot / overshoot cycle of CO2 buildup and depletion. The ASV helps maintain the proper CO2 levels in the blood. (It is actually CO2 that drives respiration, not O2).

The other reason central sleep apnea occurs is due to poor central nervous system function. Though the body might have no cardiovascular problems, the central nervous system fails to properly signal the muscles during respiration. This often occurs due to some problem with the brain stem. It may also occur due to the use of opiates (often for pain management). In this case, the ASV also acts as a respirator during the time of poor respiration. This again helps maintain the proper CO2 levels. As a result the cycle of undershoot / overshoot is also broken.

I know that's probably a LOT more information than you wanted, but I figured your honest question deserved a good answer. Hope that helps.

[Roger2]

I know that's probably a LOT more information than you wanted, but I figured your honest question deserved a good answer. Hope that helps.

That certainly answered the question and I did appreciate the answer, thank you. It did help.

[rested gal]

Do all machines have this or just the more deluxe ones? I have a ResMed S9 Elite, does that have this capability?

JohnBFisher gave an excellent answer.

I'd like to mention this, Roger... the bilevel S/T, ASV, and AVAPS machines John described might be better thought of as being more complicated in design, not as "more deluxe" machines. As John said, they are designed for specific treatment purposes...for sleep disordered breathing problems that are more complicated than simple Obstructive Sleep Apnea (OSA.)

A golf club driver is more complicated to design and manufacture than a sand wedge club. They each have a specific purpose they're especially good at. Neither would be quite as good as the other for doing what they were designed to do. CPAP is especially good at keeping the airway open for a person with simple OSA.

Your ResMed S9 Elite is a great "CPAP" machine. It does have something quite "deluxe" about it when compared to another ResMed S9 CPAP machine (the S9 "Escape" -- which is what most DMEs would give to a new user.) Your Elite can record AHI and leak info and show that to you the next morning. The Escape cannot -- it shows only "hours of use."

Both the Escape and the Elite would treat you exactly the same. But the Elite has "deluxe" data reporting capability compared to the Escape. You're very fortunate to have been given an Elite rather than an Escape.

[justbreathe]

I am pushing a deadline to make sure my insurance pays 100%. I have meet my deductible this year. I must meet their requirements:

"Equipment will be rented with rental fees applied to purchase price for trial period of three
months to document patient compliance, patient tolerance, and clinical benefits prior to purchase.
After 90 days of coverage a decision regarding the medical necessity of purchase will be made"

If I take what they have I can meet the 90 Days before DEC 1, 2011 when my $4,500.00 deductible starts over. If I wait for them to order the newer S9 model which they will I am sure they will mess things up and cause me to miss the date by a few days.....