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How does ASV prevent CA's re low Co
#1
How does ASV prevent CA's re low Co
Curiosity has me going around my head wondering how does ASV treat CA's which, tell is due Low Co2, but then how does ASV then adjust pressure so as to stop from having Low Co2? it's not like machine can add extra Co2, only option then is reducing O2 but How?  then doing will that then cause not getting enough O2?  

Then also say not treated at all not using machine" and get CA's  why or how then what cause the untreated person get the CA's, is there triggers / Causes  to the Low Co2 ?  Hm do they breathe to much O2?
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#2
RE: How does ASV prevent CA's re low Co
It has nothing to do with CO which is carbon monoxide, it has to do with CO2 Carbon Dioxide,  

CO2 is the main driver for our breathing cycle.
Using a CPAP causes an improvement in breathing, which is accompanied by an 'improvement" in the flushing of CO2 from our system. Some settings, Increased EPR, Flex, PS and even pressure can increase this even more.  When the CO2 is flushed to below your apneic threshold the body no longer sends the signal to breathe until the value is higher resulting in a central apnea.

This is a simplified explanation, other factors do contribute but CO2 levels is the big one.  Read up on respiratory drive (google it).

Untreated persons have other causes, TBI (traumatic brain injury), stroke, seizures, meds (especially pain killers), or disease, CHF, pulmonary diseases, CNS issues, etc,
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#3
RE: How does ASV prevent CA's re low Co
Some Apnea patients like myself have Central Apnea that appear during the diagnostic sleep study before CPAP is introduced. My CA was at 124 to the Obstructive of 24. What causes my CA? Not sure and it's never come up to attempt to discover a cause. My ResMed AirCurve 10 ASV was treating all apnea perfectly fine, including all CA, until my COPD and lung health got a bit worse. In 2019 I had a bout of pneumonia and a month after that, I had bronchitis. A recent chest CT Scan reveals some lung scarring. With the extras that COPD and the illnesses have caused a very complex combo. The ASV isn't for this mixture of a complex issue. ASV is not for everyone. My unique combo requires timing control of the breath, and the ResMed ASV doesn't include manual control of these.

ASV works to combat CA by blowing harder than any CPAP via a special algorithm that ramps up PS to give a high IPAP near instantly upon a CA event. It blows and I breathe, hence the CA that was going to happen didn't. No addition of CO2 is necessary.
Dave

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#4
RE: How does ASV prevent CA's re low Co
(07-28-2021, 01:26 PM)ICEMAN Wrote: Curiosity has me going around my head wondering how does ASV treat CA's which, tell is due Low Co2, but then how does ASV then adjust pressure so as to stop from having Low Co2? it's not like machine can add extra Co2, only option then is reducing O2 but How?  then doing will that then cause not getting enough O2?  

I am not sure where you heard that CA is caused by "low CO2"", but that is certainly not true.
We inhale air which contains a lot of nitrogen and some O2 (Oxygen) and convert this into CO2, which we exhale.
Central apnea could have different underlying causes and since the disorder involves patients not breathing at all for more than 10 seconds at each episode (in my case it could take 30 seconds or more without a breath and with no ASV machine) then the resultant lower intake of oxygen, brings down the percentage of oxygen in our blood (generally you need to have a blood "Oxygen Saturation" of 95% or better (most people with no respitory or sleep apnea issue have this average).

An ASV (Auto or Adaptive Servo Ventilation)PAP machine works by monitoring your breathing pattern by analyzing "each" breath and whe your respiration stops, it starts sending your breaths in the same pattern of your natural breathing, until i detects that you are breathing by yourself again.

"CO2" has nothing to do with how ASV machines work.
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#5
RE: How does ASV prevent CA's re low Co
You are right in that ASV has nothing to do with CO2.

The primary cause of most of the CA events we see here is low CO2 concentration. Low O2 sat is definitely bad and it does cause you to breathe faster, but low O2 in and of itself will not cause you to start or stop breathing. Low CO2 below will cause you to stop. Breathing.

There are many other causes, including idiopathic or unknown cause. Still most, not all,of what we see here is from low CO2
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#6
RE: How does ASV prevent CA's re low Co
(07-28-2021, 04:14 PM)S. Manz Wrote: I am not sure where you heard that CA is caused by "low CO2"", but that is certainly not true.

Ok thanks for the answer for then Hm, Now I do really feel like really even more "dumb nut" teach me for asking Silly question then " so to sure to be sure " I won't forget the teaching "CA is Not caused by "low CO2" ok Got It
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#7
RE: How does ASV prevent CA's re low Co
Thank Gideon good point out,e "CO which is carbon monoxide, and CO2 Carbon Dioxide" yes I do get them mixed up a bit, CO or the CO2, times take lazy guess, will look to now try remember the (2) so O2 in CO2 out
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#8
RE: How does ASV prevent CA's re low Co2
Dave & Gideon,  and thanks for that KISS, explanation as more easy, simpler for helps me to absorb, I did think for while or my interpreting, CA's was from just from to much pressure etc such as CAPA etc to much O2 oxygen etc, and  alone lower pressure would fix,t but do now starting see, more understandings and more complex than that, and other issues that also may contribute to the low Co2" and may also be limits in the ability to control.
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#9
RE: How does ASV prevent CA's re low Co
Ok here are the basics.
Neither CPAP, APAP, nor BiLevel wo backup (VAuto or "S" models) are capable of treating CA, they are not designed to do so.  Yet these are the machines that are prescribed to nearly all Apnea patients.  Instead what we do is manage settings to AVOID CA events.   These machines are designed to treat obstructive events.  

The most common, not the only, central Apnea we see is CO2 induced Central Apnea, Frequently this is Treatment Emergent Central Apnea.  

This occurs because our machines flush out more CO2 than before CPAP.  When CO2 goes below  the apneic threshold a central Apnea event occurs.  

To "treat" with these devices we reduce the amount of flushing that occurs.  Usually the first thing we try is to reduce this flushing by reducing the pressure difference caused by EPR, Flex, PS depending on the machine.

This treatment is frequently a balancing act between  Central and Obstructive events.  The cations that reduce obstructive events tend to increase Central events and vice versa.

Usually we can get pretty good results and we will tell you what and why, if we don't just ask.
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#10
RE: How does ASV prevent CA's re low Co
Thanks again Gideon, and have been Slowly lowering my Pressure, while I know take on to consider a try at Fixed 7 but did not to Fixing the pressure, as had intended to dropping in slow .02 increments, then stop at 7 ! then increase the min up in .02 increments, to meet, but instead continued dropping the max  to presently now 6.6  & min 5.6 LOL! But have been on look for O & H's to increase but they haven't really changed, but then also the CA's haven't really changed ?  So then haven't yet had that inconsistently random High AHI of CA's but as now posted these readings, I is presume  (CA's inconsistently) is just waiting to catch me out?   

But dose at this stage given 1 example the APAP lower pressure, in my instance of CA's not treat (prevent/reduce)? and also then not lowering the CO2 ? well at least in my CA's, or what ever is contributing to the CA's? 

But  either way to me is still presently pretty good Numbers, and also that (PB average) is under 2 presume that then is not a real concern to worry about. 

"Resmed" Shows time in Cheyne Stokes Respiration  BUT is as you have previously explained, that what you had looked at then was just Periodic Breathing?
                     P.B                   CA 
Most recent    0.00% &   CA = 1.59%
Last week      1.15% &   CA = 3.64%
Last Month    0.38% &    CA = 3.01%
6 Month        1.38% &    CA = 3.48%
last Yr           1.20% &    CA = 3.51%
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