ASV Need prescription terms definitions

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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photonic
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ASV Need prescription terms definitions

Post by photonic » Wed Jul 30, 2014 9:57 pm

Greetings,

I have finally received my backordered Resp ASV machine and a copy of my Rx. It has been a long wait due to a backorder at the factory.

I have some questions about the terms on my Rx.

Here is what I understand: Max Pressure 25, Min EPAP 4, Max EPAP 15, BPM 11, BiFlex 3

Here is what I do NOT understand: Min PS (pressure support) 0, Max PS 20, Timed Insp 1.5

Can you help me understand these last three terms and settings?

Thanks!
Last edited by photonic on Wed Jul 30, 2014 10:14 pm, edited 1 time in total.
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palerider
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Re: ASV Need prescription terms definitions

Post by palerider » Wed Jul 30, 2014 10:14 pm

photonic wrote: Here is what I understand: Max Pressure 15, Min EPAP 4, Max EPAP 15, BPM 11, BiFlex 3

Here is what I do NOT understand: Min PS (pressure support) 0, Max PS 20, Timed Insp 1.5
disclaimer, I understand the resmed vpap adapt asv, which isn't exactly the same as the pr60 autosv.

however, the min/max pressure support is the amount that the machine can boost the ipap above the epap, (pressure support is just the diff between epap and ipap). it does it on a breath by breath basis, as needed, if you're breathing ok on your own, it may not boost pressure any (ps 0) on inhale. if you stop breathing on your own, it'll start boosting ipap, breath by breath, at the rate you'd been breathing to ventilate you until you start breathing on your own again. I'm guessing it'll do that in 1.5 second bursts (the timed insp)

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Re: ASV Need prescription terms definitions

Post by aytikvjo » Wed Jul 30, 2014 10:16 pm

Timed Insp 1.5: This means that when the machine delivers a mandatory breath, the inspiratory time will be 1.5s. Patient triggered spontaneous breaths will be until your breathing triggers the exhale cycle.

PS stands for 'pressure support'. It's how much pressure above EPAP the machine delivers. Since it's an ASV, PS will vary on an intrabreath basis to assure a relatively constant tidal volume.
Min PS 0: This means that the minimum pressure difference between inspiratory / expiratory breaths (IPAP-EPAP) is zero. Effectively the machine would be acting as CPAP.
Max PS 20: This means that the max pressure difference between the inspiratory / expiratory breaths (IPAP - EPAP) is 20 cmH2O. It probably will never go this high, usually a PS of 8-12 is required to deliver a breath to a patient with no respiratory drive. Could be higher if airway resistance is abnormal.

BiFlex of 3 might be annoying for you. You'll have to experiment with what value you find comfortable. Personally I find that it modifies my breathing pattern too much, causing me to breath faster than normal, so I just keep it off. It doesn't affect therapy in any major way and is supposed to be a (dis)comfort feature.

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photonic
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Re: ASV Need prescription terms definitions

Post by photonic » Wed Jul 30, 2014 10:19 pm

Thanks. So does this mean that when I have a central, the machine will start pulsing air at me with increasing pressure until it "wakes up" my brain stem to start breathing again? (and hopefully does not wake "me" up!)
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Re: ASV Need prescription terms definitions

Post by aytikvjo » Wed Jul 30, 2014 10:24 pm

photonic wrote:Thanks. So does this mean that when I have a central, the machine will start pulsing air at me with increasing pressure until it "wakes up" my brain stem to start breathing again? (and hopefully does not wake "me" up!)
My understanding is that it will increase pressure like a volume ventilator until a set tidal volume is delivered. The algorithm determines this tidal volume based on past breathing patterns. My machine adjusts volume on an interbreath basis, but the ASV does it intrabreath. This is essentially the difference between AVAPS and ASV.

It shouldn't wake you up as long as you have a good seal. The main concern is that the increased pressure can form a leak that was otherwise absent at lower pressures. You'll have to find the appropriate tension for your headgear to prevent this.

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photonic
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Re: ASV Need prescription terms definitions

Post by photonic » Wed Jul 30, 2014 10:25 pm

Thanks aytikvjo , I was posting before I had read your post. Your explanations help on this very complicated topic. The Timed inspiration still evades me. Does this mean that the machine pulses me for a length of 1.5 seconds? What happens next if I still don't initiate a breath?
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Re: ASV Need prescription terms definitions

Post by palerider » Wed Jul 30, 2014 10:26 pm

photonic wrote:Thanks. So does this mean that when I have a central, the machine will start pulsing air at me with increasing pressure until it "wakes up" my brain stem to start breathing again? (and hopefully does not wake "me" up!)
it will push air into you until you start breathing on your own again... there's no assumed connection between the machine's actions and your brain stem.

you'd normally start breathing again after a central, it just keeps air going in and out of you during the centrals.

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Re: ASV Need prescription terms definitions

Post by palerider » Wed Jul 30, 2014 10:32 pm

photonic wrote:Thanks aytikvjo , I was posting before I had read your post. Your explanations help on this very complicated topic. The Timed inspiration still evades me. Does this mean that the machine pulses me for a length of 1.5 seconds? What happens next if I still don't initiate a breath?
it will keep doing it 1.5 seconds inhale, at an 11 breath per minute rate (based on the other numbers you said)

this may help:
http://action.lung.org/site/DocServer/D ... ocID=12186

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Re: ASV Need prescription terms definitions

Post by photonic » Wed Jul 30, 2014 10:34 pm

Thanks Palerider. I will look at that. We perhaps need to keep posting tonight to push you over 1,000 posts. You are on the verge my friend!
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Re: ASV Need prescription terms definitions

Post by aytikvjo » Wed Jul 30, 2014 10:45 pm

photonic wrote:Thanks aytikvjo , I was posting before I had read your post. Your explanations help on this very complicated topic. The Timed inspiration still evades me. Does this mean that the machine pulses me for a length of 1.5 seconds? What happens next if I still don't initiate a breath?
The timed inspiration is part of the backup-rate subsystem. This is your main defense against central apneas. The servo volume ventilation subsystem works in addition to it to safeguard against hypopneas by delivering constant tidal volumes.

Your normal resting RR might be between 10 and 16 BPM depending on many factors. When your respiratory rate falls below 11 BPM, the backup rate kicks in and delivers a mandatory breath. While an apnea is generally speaking considered cessation of respiration for ~10 seconds ,we don't actually want to let it go that long as to maintain adequate, more natural, ventilation. Since at this point you aren't spontaneously breathing, the machine needs to know how long it should deliver a breath for because your breathing pattern isn't really telling it much. During this 1.5 seconds, the machine will generate whatever pressure is needed such that the calculated tidal volume is delivered in this window. Since lungs behave elastically, delivered tidal volume generally varies linearly with airway pressure. If we change the inspiratory time to a larger number, say 2.5 seconds, the pressure will ramp more slowly but you will be left with less time to exhale. If it were less time, such as 1 seecond, then the change in pressure could be too abrupt and wake you up. Normally the ratio between your inhalation to exhalation time is around 1:2. Extreme values of this ratio such as 1:1 or 1:3 can be uncomfortable or even prevent you from fully exhaling before the next breath is delivered.

Hope that helps

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Re: ASV Need prescription terms definitions

Post by photonic » Wed Jul 30, 2014 10:54 pm

Extremely helpful and interesting.
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Re: ASV Need prescription terms definitions

Post by palerider » Thu Jul 31, 2014 8:38 am

photonic wrote:Thanks Palerider. I will look at that. We perhaps need to keep posting tonight to push you over 1,000 posts. You are on the verge my friend!
sorry, I went to sleep right after that post

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Re: ASV Need prescription terms definitions

Post by bwexler » Thu Jul 31, 2014 10:47 am

This has been a helpful discussion, but what exactly does Biflex=3 do?
My ASV is set that way.

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Re: ASV Need prescription terms definitions

Post by palerider » Thu Jul 31, 2014 11:02 am

bwexler wrote:This has been a helpful discussion, but what exactly does Biflex=3 do?
My ASV is set that way.
oy, it's complicated, well... here's a picture:

Image

to plagarize:
Bi-Flex Pressure Relief Technology

Bi-Flex pressure relief technology offers pressure relief at inhalation and exhalation to make BiPAP therapy more like natural breathing. By tracking each breath, Bi-Flex pressure relief technology delivers pressure relief at three critical points in the breathing cycle:
  1. the transition from exhalation to inhalation
  2. the transition from inhalation to exhalation
  3. during exhalation.
so, it sort of rounds off the pressure transitions, and drops the pressure more on exhale, *and* does this to a greater extent for larger breaths than for smaller breaths. (as evidenced by the three examples above)

make sense?

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Last edited by palerider on Thu Jul 31, 2014 12:48 pm, edited 1 time in total.
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photonic
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Re: ASV Need prescription terms definitions

Post by photonic » Thu Jul 31, 2014 12:38 pm

palerider wrote:
bwexler wrote:This has been a helpful discussion, but what exactly does Biflex=3 do?
My ASV is set that way.
oy, well... here's a picture:

Image

to plagarize:
Bi-Flex Pressure Relief Technology

Bi-Flex pressure relief technology offers pressure relief at inhalation and exhalation to make BiPAP therapy more like natural breathing. By tracking each breath, Bi-Flex pressure relief technology delivers pressure relief at three critical points in the breathing cycle:
  1. the transition from exhalation to inhalation
  2. the transition from inhalation to exhalation
  3. during exhalation.
so, it sort of rounds off the pressure transitions, and drops the pressure more on exhale, *and* does this to a greater extent for larger breaths than for smaller breaths. (as evidenced by the three examples above)

make sense?
Very helpful again (you rock). So why then do some people post that this makes breathing more uncomfortable. Seems odd to me...
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F&P Evora Full with S-M size
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