Can cpap detect diff between central/obstruction? - one can!

[dsm]

(When I started writing this I had not come across the SOMNOvent CR only the SOMNOsmart 2 - the SOMNOvent CR appears to be a radical advance
over other ASv machines & does some very interesting things. So when reading what follows bear in mind I was discovering a lot along the way - DSM).

*******************************************************************************************************************************************************************

This topic comes up regularly & trying to provide any meaningful & accurate answer is a bit tricky.
Reason for this is that most cpap brands can't but there is at least one possibly 2 that claim they can - to a degree.

Believing these claims becomes a matter of opinion & faith. Technically at least one brand has been claiming their
machine can accurately pick the difference. This particular machine has been around for a few years now & they
still claim their machine can 'precisely' determine the type of event.

QUOTE RE THE SOMNOsmart 2 Apap machine ...
>>Precise
Precise event recognition is based on the unique combination of the OPS (FOT), flow and snore signals. That guarantees greater accuracy in the recognition of snoring, flow limitations, apnea and hypopnea. The difference between central and obstructive events is ensured. Artefacts, leakage and mouth expiration are also unambiguously recognized.
<<

FOT is 'Forced Oscillation Technique' it is a technique sends a burst of modulated air (typically between 2000 & 5000 cycles/sec) to the sleeper down the airhose & monitors the response. It is claimed FOT can accurately distinguish between CSA & OSA (centrals & obstructions).

The wording quoted above is very careful as to what they claim, but in broader discussions FOT is claimed to provide a high degree of accuracy in picking the difference between OSA & CSA. Perhaps the caution in accepting the claim may relate to the vast differences in people's neck throat structures & while 100% accuracy might be possible with some 'types' of people, that accuracy may not apply to all types.

The machine that is supposed to be able to accurately tell the difference between CSA & OSA, still doesn't try to clear a central. Being an Auto means it is not really set up to even try. On the other hand ASV machines are designed to deal with Centrals but the brands we are familiar with *rely* on the obstructive events being dealt with by an adequately high epap pressure. I don't know of an ASV machine that probes (such as with FOT) to make a clear cut decision as to if an event is CSA or OSA. I call ASV machine TRI-Level machines (easy to remember & pretty accurately describes them - epap, ipap & ipap+ - I see Weinmann in their product sheet on the SOMNOvent CR machine, say it adjusts 3 pressure levels, so TRI-Level seems to me a good easy nickname ).

The machine in question is the SOMNOsmart 2 manufactured by Weinmann in Germany.
http://www.weinmann.de/en/home_homecare/sleep_therapy/ Weinmann
http://www.medicarehk.com/Weinmann%20SomnosmartII_1.htm SOMNOsmart 2

What I didn't know before today, is that not only do Resmed & Respironics make an ASV machine, but so does Weinmann and my next question is, does Weinmann use FOT in their ASV machine ?

Weinmann SOMNOvent CR (ASV) machine ...
http://www.weinmann.de/en/home_homecare ... ovent_cr0/

Weinmann appear to use FOT in this machine too - 1) if they commonly use it in the SOMNOsmart 2 Apap, why wouldn't they use it in the SOMNOvent CR machine ?. 2) They state in the product brief "with differentiation between obstructive & central events"

So, what they do say in this product sheet does raise a wealth of questions ...
http://www.weinmann.de/fileadmin/weinma ... N_0908.pdf

For example they say their SOMNOvent CR,

>>
CR mode: combined therapy for
Cheyne-Stokes Respiration and Sleep Apnea.

intelligent and powerful algorithm for
automatic adjustment of three pressure levels
(IPAP, EPAP and EEPAP) to the current needs of the
patient with differentiation between obstructive and
central events:

IPAP and EPAP regulation for adequate pressure reaction
to periodic breathing or CS Respiration
Auto-CPAP functionality for adjustment of EEPAP upon
recognition of obstructive events (= autoEEPAP)
maximized ventilated breath with sinking of EPAP
automatic or pre-set background frequency
<<

NOTE the word 'Automatic' applying to all 3 pressures !!! The Resmed and Respironics SV type machines have the therapist manually set the epap & ipap & the machine then auto adjusts the ipap pressure in response to meeting volume or flow targets. Weinmann seem to be saying they adjust all 3 as needed. That implies a far more advanced approach, plus, they add the words regarding differentiation between CSA & OSA.

Am interested as to if our other investigative members (SWS where are you ) have any thoughts re the Weinmann claims.

DSM

[dsm]

Having looked more closely at the SOMNOvent CR, it works very differently from the Resmed Vpap Adapt SV & Respironics Bipap Auto SV.

The difference is in the manipulation of epap pressure (they call it EEPAP). My guess is they use FOT to decide if they need to adjust EEPAP based on detecting obstructions with FOT bursts & that is how they can claim to differentiate between CSA & OSA and deal with both in the right way.

Based on what I see in their product brief, this machine seems to be the most advanced CPAP on the market in terms of algorithmic manipulation of the three pressures. The Resmed Vpap Adapt SV may still have the most sophisticated blower though.

DSM

#2

On further close examination, it seems EPAP may be the one constant, IPAP & EEPAP get varied. EEPAP in response to obstructions & IPAP in regulating centrals & smoothing out volume fluctuations. I will look closer for evidence EPAP gets dynamically adjusted too.

#3 ABSOLUTELY, it adjusts ALL three pressures. EPAP isn't left static. When regulating breathing fluctuations it increases the ipap/epap gap & does so by dropping epap & raising ipap at the same time.

D

[dsm]

Summary of what was started above.

The original post was to discuss how the SOMNOsmart 2 uses 'FOT' to determine if an event is an obstruction or a central. But in following
that line a lot more info came out in regard to an even more advanced machine called the SOMNOvent CR. It appears to use FOT and SV.

So the SOMNOvent CR appears to be a radical advance over the ASV (Adaptive Servo Ventilation) machines put out by Resmed & Respironics.
Resmed sell the Vpap Adapt SV & Respironics sell the Bipap Auto SV. Both excellent machines. These are not primarily for OSA sufferers
(those people who *only* have OSA & no persistent hypopneas and flow-limitations (UARS)). But, It may turn out that not many people are
'pure OSA' sufferers anyway.

ASV machines are basically a bilevel that adds the ability to adjust IPAP upward very rapidly (within one breath) if the sleeper looks like they
won't reach the target volume or flow that the machine has been tracking.

If we put aside the Cheynes-Stokes respiration issue, SV machines have increasingly been recommended for complex and mixed apnea. These
two variants both include central apneas. Complex Apnea is when centrals appear when the user goes on cpap & mixed apnea is when the user
has centrals and also obstructive apnea (the centrals not being triggered by the cpap therapy).

Up until the SOMNOvent CR machine, the titration for an SV machine typically involved setting the EPAP pressure to a setting that clears ALL
obstructive events, then setting a minimum IPAP typically 3-4 above the EPAP - the prior SV machines then tracked volume or peak flow and
if the sleeper doesn't look like meeting the target, pressure is instantly increased.

The SOMNOvent CR appears to have EPAP set to a pressure that clears most obstructions, then IPAP is set using a PS value (say 3-4 CMs above
EPAP). Then, the SOMNOvent CR uses Auto algorithms to monitor for obstructions (my guess is from the SOMNOsmart 2). If an obstruction is
detected it doesn't actually raise EPAP but does raise the value called EEPAP (EPAP is at the start of exhalation & the machine raises pressure to EEPAP at the end of exhalation - restated exhale phase has two pressures, epap at the start & eepap at the end) to clear the obstruction in the same way Autos do. If a central is detected it adjusts BPM (breathing rate) to cycle between IPAP & EPAP at a rate needed to clear the central. If the tidal volume was declining before the central, the machine will also have increased the ipap/epap gap as well.

When volume starts to increase beyond the current tracked target, the SOMNOvent CR drops the gap between EPAP & IPAP to a 0 CMs gap. That is
an unusual approach.

This is the 1st machine I have actually seen in production that does all these things. We have talked about doing all this here in the past year.
In 2008 I came across a patent that described auto adjustment of EPAP, but the SOMNOvent CR actually does it.

I am rating this machine as by far the most advanced ASV machine on the market & because Weinmann appear to have integrated proven
technology from the SOMNOsmart 2 Auto, it seems they are onto something that their competitors may have trouble matching for quite a
while.


DSM

#2 corrected a few points

[kebsa]

it is interesting, and when i was doing the searches i did not find this company at all! i have complex sleep disorderd breathing and a big issue with centrals- i have tried both the resmed and the respironics machines you mention. I tried the respironics first and no matter what changes they tried i had an AHI that ranged from 94 to 104 even though i did feel a bit better than without a machine. I was beginning to think that that was the best we would be able to do and then i was switched to the Resmed and my AHI is 0.2 and AI is 0! Despite both machines being aimed at dealing with the same problems and sounding like they deal with it in a similar way i can say that they feel very different indeed from my point of view- when i was talking to the DME about it she said that they found some people did better with one and some the other, very few get similar results with both machines which i find very interesting. I am an IT student and i would love to get a closer look at the 2 different alogorithms as i don't think i have come across a situation with such a huge difference in treatment outcomes for the same problem. I was led to believe that the Resmed did not focuse on ipap and epap like the respironics but on eep -i am happy with the resmed but purely from academic point of view it would be interesting to have tried the machine you mention too as a comparison

[dsm]

it is interesting, and when i was doing the searches i did not find this company at all! i have complex sleep disorderd breathing and a big issue with centrals- i have tried both the resmed and the respironics machines you mention. I tried the respironics first and no matter what changes they tried i had an AHI that ranged from 94 to 104 even though i did feel a bit better than without a machine. I was beginning to think that that was the best we would be able to do and then i was switched to the Resmed and my AHI is 0.2 and AI is 0! Despite both machines being aimed at dealing with the same problems and sounding like they deal with it in a similar way i can say that they feel very different indeed from my point of view- when i was talking to the DME about it she said that they found some people did better with one and some the other, very few get similar results with both machines which i find very interesting. I am an IT student and i would love to get a closer look at the 2 different alogorithms as i don't think i have come across a situation with such a huge difference in treatment outcomes for the same problem. I was led to believe that the Resmed did not focuse on ipap and epap like the respironics but on eep -i am happy with the resmed but purely from academic point of view it would be interesting to have tried the machine you mention too as a comparison

Kebsa,

I suspect it won't get FDA approval for a long while (I can't find any application for it to be approved). But I sure would like to try it just to 'feel' what they have done in their algorithms. It looks very innovate & assuming they have perfected FOT sampling for a broad spectrum of users, they may well have the most advanced machine available for us plebs (outside of hospitals & I C wards).

I am more than intrigued as what they are doing was what I put into a wish list in the middle of last year. Using an Auto algorithm at the low end plus a probing technique to differentiate OSA from CSA - adjusting Epap (EEPAP) to deal with any detected OSA & then adjusting the IPAP (& EPAP) & BPM to deal with centrals & irregular breathing. This can only work well if the machine is very good and accurate at that OSA CSA differentiation. They seem to have it.

DSM

PS I have known of the Weinmann machines for the past couple of years but we never hear of their achievements. A couple of years ago we talked a lot about FOT & how useful it might be. I know that even recently SWS wondered if some pressure bursts I was detecting in the Bipap Auto SV, might have been FOT, but there is nothing in the Respironics patent of the SV to confirm it.



PPS I am satisfied I can explain a lot of the differences between the Resmed & Bipap Auto SVs (used em both for quite a while now).

[Raj]

Extremely interesting, DSM. It wasn't that long ago that cpap machines were essentially vacuum-cleaner motors with crude masks, and while much progress has been made since then, the technology is still in its infancy. I suspect we'll be seeing considerably more sophistication within the next decade and suspect that an accurate means of distinguishing obstructive from central apneas will be an essential part of xpap evolution, built into every worthwhile machine. The distinction is particularly crucial for making a truly safe and effective full-range APAP machine. This will prevent the escalating feedback loop resulting from a machine interpreting CA events as OSA events, increasing pressure inappropriately and thus generating more centrals and so on.

[dsm]

Kebsa,

This link is to a study done in 2001 that looked at using the Resmed Vpap Adapt SV (then referred to as the Autoset CS 2) for use in CSR therapy. Whilst the ASV machines were originally targeted at CSR, they are now offered for complex and mixed apnea as well so the study is useful in gleaning out some aspects of how the Resmed Vpap Adapt SV ASV machine works. It may be heavy reading in parts but it is the snippets that are understood that make it worth reading.

http://ajrccm.atsjournals.org/cgi/conte ... /164/4/614

Also

There is an active study underway involving the effectiveness of the SOMNOvent CR ASV machine. This is of interest only as it doen't include any reults yet.
http://clinicaltrials.gov/ct2/show/NCT00811668

DSM

[dsm]

This is a summary of the SOMNOvent CR behavior as explained in their product sheet.
1st I'll list their description then I'll add my interpretation (W: = Weinmann. D: = DSM) ...

W: The SOMNOvent CR applies 3 adjustable pressures, IPAP (brethe in), EPAP (breathe out) and
EEPAP (End exhalation phase). IPAP => EPAP & EPAP <= EEPAP.

D: (Ipap is usually highest, Epap is usually lowest & Eepap is usually higher than Epap. Eepap
appears to start off halfway between Ipap & Epap.

Normal Breathing
================
W: When breathing is normal a pressure relief is activated (called SoftPap). This occurs
just prior to the transition to breathing out, the therapy pressure is lowered in order
to ease the breathing out effort and increase comfort. Well before the breathing out pahse
ends, the pressure is raised to the EEPAP level.

D: This is pretty well normal Bilevel except the SOMNOvent CR starts to raise EPAP some
time before exhalation ends.


Obstructions
============
W: When obstructions are detected (epochs with apnea, hypopnea, flow limitations, or snoring)
the EEPAP pressure is raised to hold the airway open.

D: This is interesting as they are saying that they detect the mix of events (& I am assuming
they also probe with FOT) that indicate an obstruction, but, rather than raising EPAP, they go
into the current EPAP pressure (allow breathing out to start) but then during breathing out
they raise the pressure such that EEPAP is higher than it was before the events were detected.
Also, the implication is they do this within a single breath (the diagram shows it happeing in
one breathing cycle)!. I am assuming that the machine works on the basis that EEPAP is
applying a higher pressure now that inhalation is about to begin & that this higher pressure
will splint the airway better than it was when the block or pending block, was sensed.


Decreasing Tidal Volume
=======================
W: The machine tracks the tidal volume (what is breathed in and out in one breath), If the tidal
volume starts to drop below the tracked target (as in an hypopnea or flow-limitation), the
machine then pushes epap and ipap apart.

D: Decreasing Tidal Volume is akin to hypoventilation (reduced breathing - a typical CSR phase).
Apparently the machine pushes Epap & Ipap apart equally, and, again appears to do so within the
one breath. Note the EEPAP pressure appears to be left as it was. This means EPAP drops lower
than it was before but EEPAP stays the same. Unusual approach. Perhaps very insightful ?.


Apneas
======
W: ALSO, when Apneas occur the machine responds with a patient-specific frequency (like ST).

D: What this appears to mean is that if an apnea is detected (central rather than an obstruction,
remember this machine claims to be able to clearly distinguish between them), the machine reverts
to a tracked Breaths-per-Minute (BPM) it has previously calculated based on some tracking.


Increasing Tidal Volume
=======================
W: When Tidal Volume increases. The Epap / Ipap gap is reduced to zero.

D: This is very novel !. Increasing tidal volume is akin to hyperventilation (again a typical
CSR (Cheynes-Stokes Respiration) pattern). The machine removes the gap between Ipap & Epap
but also this time brings Epap & Ipap & EEPAP all to the same pressure. The machine at that
instant is acting like a conventional single pressure cpap machine. The diag again implies
this can happen in a single breathing cycle.


OTHER COMMENTS
==============
D: The machine appears to be very quiet - rated at 31 db. When 1 meter away at 26db (10 hPa).
Also the clinician can set a fixed rate BPM or set it to AUTO. Operating pressure is limited
to 4-20 CMs.

This approach of floating the epap & ipap apart & together to adjust tidal volume seems quite
different to what all the other ASV machine do.

Having EEPAP more or less as a mid point between Ipap & Epap but adjusting it if an obstruction
is detected & doing that in a single breath (am assuming the diags apply to one breathing cycle as
shown in their prod sheet) seems very ambitious & way more than any other vendor attempts.

It would be good to hear from someone who has used one. The other interesting thing my searching
showed up is that the SOMNOvent CR has been around since 2007 !.

DSM

[dsm]

This is the set of diags used ...

[kebsa]

Thank you very much for the links, I have always been a very strong believer that to be able to properly manage a chronic health problem, it is advisable to make a real effort to understand firstly the basis of the condition and secondly to have a good understand of how the treatment works rather than leaving it to the hands of the Doctors- the old say of doctor knows best just never cut it with me! I have taken a very active part in the management of my Multiple sclerosis, diabetes and RSD. When i was told that i had complex sleep disordered breathing i found that unlike the other conditions, it has been a bit tough to find some decent information about the condition and how it changes the normal sleep architecture- and DME's seem to take an active role of trying to prevent the patient getting involved and accessing information- it is not something i have come up against in the past- here in australia prescriptions are not a legal requirement for getting cpap equipment but most of the DME's insist on one anyway, then they will not sell the software so that i can just down load the data and then forward it directly to the physician myself- i have to lug the machine back to them so that they can do it! and if i want the software i have to get a letter from my doctor to say he is happy for me to have it!!! i think this is disgusting! IF they did the same thing with diabetes it would be impossibe to get good control of the disease- i can't understand what they are afraid of. I was relieved to find information on how to access the data on the machine on a daily basis but it makes it seem as though i am doing something underhanded by wanted access to my results on my machine!


sorry i have gone off topic but i am begining to find this a bit frustrating- the sleep physician is so busy he was booked out to july when i saw him last in December so i feel i am at the mercy of the DME who basically said that they were really only sales people not therapists and yet it seems like i am meant to trust them to manage this condition! thats not going to work for this little black duck! Thankfully i have access to the library and databases at university so i have been able to access some information and this site has so much valuable information too and links like you have supplied. I do not actually have a copy of mysleep study results so next time i see my doctor i will ask for a copy and that will help me understand all this a lot better. At least i am getting good results now!

I know this is off topic so i apologise, but i would be interested in you input. The machine i am using is great- i feel comfortable with it and compliance with treatment is no problem as it just feels right. It is a lot more expensve than a lot of the machines ($4000 AU) and it is rather bulky- i don't actually travel as such but i have spent a lot of time in hospital (22 admissions last year alone!) and when the MS flares up i get real sick real quick! I can't imagine being able to pack this set up quickly in the midst of a relapse! Quite often i get carted off by ambulance and my wonderful neighbour brings my gear and my wheelchair for me- i have a bag permanently packed for just this reason and it would be great to have a back up machine that was already packed so my neighbour could just grab the whole lot for me! I have wondered about one of the Resmed machines such as the S8 elite or elite2, with EPR- i wondered if the EPR set to 3 would sort of match what the Vpap adapt SV does- i can see that the max pressure is set to 15, the min to 3 and EEP to 10, my average pressure is 11.6 consistently. I wondered if one of the more standard machines set to 14 and EPR to 3 (maybe some trial and error to get it right)- is this a crazy idea?? i realize the results would not be as good as i am getting with the ASV but it would certainly beat nothing, wouldn't it??

[dsm]

Kebsa,

The machine you have ( Synchrony with AVAPS ) is a special class of machine that works differently from others. If in AVAPS mode it is delivering an assured volume & the pressure support is used to make that happen. The sleep doc dials in a tidal volume that is needed & the machine then ventilates to meet that volume for each breath.

ASV machines were designed originally just for Cheynes-Stokes respiration but as the technology & experience advanced, it became clear they were the ideal machine for mixed apnea and for the emerging condition called complex apnea. SV machines adjust pressure to smooth out respiration but they don't take the AVAPS approach of trying to deliver a specific tidal flow amount for each breath.

1) Restating that difference, AVAPS will spend the night trying to ensure each breath matches the entered Vt.

2) The SV tracks the sleepers volume (or peak flow) and seeks to stay within 90% of the target as calculated from the previous 3 or 4 mins monitoring. The Resmed SV tracks volume & rate, the Respironics SV tracks peak flow & rate. I am not 100% sure what the Weinmann SOMNOvent CR tracks but I interpret it to be volume (based on the diags above where the machine detects hyperventilation & hypoventilation & adjusts the ipap/epap gap accordingly).

So looking for another machine to emulate the AVAPS is not really viable. Using EPR is like using a bilevel & is ok for temporary use in place of an SV but even then it isn't ideal (but it works ok for me for a few nights). It really caught my eye to see that the Weinmann machine drops the bilevel gap completely if the sleeper starts to hyperventilate. The S8 with EPR will deactivate the EPR & resume ipap pressure but only if SA events are being detected. The S8 doesn't actually use breathing rate as a reason to deactivate EPR, just SA detection.

So, just to restate. The AVAPS is unique. It is more like a hospital ventilator that is designed to deliver a patient a fixed volume of air per breath. This is called Volume ventilation whereas the SV machines aren't specific as they track to a target that is 90% of the current volume/peak flow. This type of ventilation is called pressure ventilation.

- AVAPS will always try to deliver the dialled in volume.
- SVs adjust according to patients needs as they go through different phases of sleep.
- AVAPS doesn't try to vary its delivery even when the patient enters REM etc: phases of sleep
- SVs will vary as the patient changes phases.

The Weinmann machine kind of does it all. It tracks obstructions & adjusts EEPAP (which is what Cpap Autos do), The SOMNOvent CR tracks volume & rate & adjusts the ipap/epap gap based on what it detects. It also tracks central apneas and will adjust rate (while at the same time it can be adjusting the ipap/epap gap). The SOMNOvent CR doesn't work like the AVAPS.

Auto Bilevels are basically only tracking SA events but still aren't fully able to tell the difference between a central or an obstruction.
The Respironics Bipap Auto with Biflex floats both Epap & Ipap - it starts with a gap of 2 CMs & adjusts epap & ipap independantly - it doesn't track volume & rate - but, does look for obstructions & uses that to change the pressures.
The Resmed Vpap Auto does the same but always maintains a fixed gap between ipap & epap.

DSM

[dsm]

This post is to further expalin one aspect of how the SOMNOvent CR works, that is not completely clear in the prior details.
(Refs to CSR = Cheynes-Stokes Respiration)

This is how the machine deals with Centrals. (I intend at some time to do a seperate write-up on how each type of machine reacts when it experiences a central).


In the case of the SOMNOvent CR when in CR mode, it does 2 things to 'deal' with centrals.

When a central is about to occur, it is inevitable preceded by a reduction or slowing in tidal volume (the air breathed in & out in 1 breath). This is very similar to a flow-limitation or hypopnea except they don't cause an accepted 'no-flow' situation (however, there is a minimum air flow that is classified as a Central vs those two conditions but lets not split hairs at this point).

The SOMNOvent CR when it detects a reducing volume (within 1 breath) will start to raise IPAP and reduce EPAP (apparently in equal proportions), thus increasing the IPAP/EPAP gap. The slowing in breathing is called hypoventilation (also associated with too much carbon dioxide in the blood). If the airflow then ceases enough to be classified as a central, & allowing that this machine can tell the difference between an obstruction & a central, the machine will start to cycle between these expanded Ipap & Epap pressures at the tracked BPM (breaths-per-minute) rate the machine has stored inside. This BPM can be set to a fixed # by the clinician or it can be set to AUTO & thus be calculated by the machine based on tracking the prior respiration rate.

Because a central will normally only occur in a waning of respiration, the SOMNOvent CR can safely do its other trick of removing the ipap / epap gap when the sleeper's volume starts increasing beyond the tracked target. If a person hyperventilates (also associated with too little carbon dioxide in the blood), tidal volume will start to increase & the treatment is to raise epap & lower ipap until they meet thus at that instant the machine is more like a cpap delivering one single pressure. It remains at that pressure until the hyperventilation stops and tidal volume comes back to the previously tracked target.

Sleepers with congestive (or chronic) heart failure can enter into a pattern of waxing & waning respiration (CSR) & the above is how the machine smooths it out. Sleepers with copmplex or mixed apnea are dealt with by the same mechanism except they are unlikely to be in the waxing & waning pattern that characterizes CSR. Sleepers with Periodic Breathing (PB) are basically experiencing bits of what makes up CSR but not in a patter like CSR is. All these conditions can be addressed. Plus, as mentioned before, the SOMNOvent CR can also apply an AUTO algorithm that adjusts the end expiratory pressure (EEPAP), to keep the airway open & clear obstructions as well.

Some people may have difficulty grasping the EEPAP vs EPAP pressures. Try to recall that EPAP is the pressure at the start of exhale & EEPAP is what it is lifted to as the exhale phase ends. EEPAP is normally higher than EPAP. In normal breathing & hypoventilation (waning volume) EEPAP will be about halfway between IPAP & EPAP. In hyperventilation IPAP & EPAP are brought together to meet EEPAP & all become the same pressure (CPAP like).

The only time EEPAP may not be halfway is if the machine had been detecting OSA events & had previously raised EEPAP to a higher setting than normal to counter the obstructive events (Snoring + flowlime/hypopneas & OSA).

Very very dynamic

DSM

[kebsa]

You are a mine of information!! it is very obvious that you have spent a lot of time making sure that you understand the technology behind these machines!! I am still coming to grips with the idea of some people having to cope with cheynes stokes resps, i have mentioned before that my background is nursing and i consider myself to be pretty good at keeping my knowledge base up to date even though i am no longer involved directly in patient care. Until having to learn about sleep apnea from a patients point of view, i had always only heard of cheynes stokes respirations in terms of patients who were also most at a point of death- convetional wisdom taught that the waxing and waning pattern of cheynes stokes was an indication that the person was basically moribund and only a few hours away from the pearly gates- we were always taught that it was a sign that the brain was basically shutting down and beginning to lose control of automantic functions such as respiration- so it has been a real eye opener to see that this pattern of breathing is also a form of sleep apnea that people live productive lifes with (this is not intended to sound unkind just an example of how little the average medical practioneer or practicising nurse actually know about sleep disordered breathing!

Thanks for explaining the unique nature of the ASV machines, i did know that they are classed as a form of non invasive ventilation rather than straight cpap or bipap. your explanation makes the other machine sound really intriguing so i will be watching your posts for more information as you find it!! i realised that use of the conventional resmed S8 elite or similar would not mimic the function of the ASV machines but i was hoping that it may be suitable as a short term option either as backup or for short hospital stays. as i mentioned, the bulk of the asv machine is one of the reasons but also the cost. I have worked in hospital environments long enough to know that they need to be considered the equivalent to the average shopping mall- they are far fromm secure environments when it comes to patients belongings- there are actually criminals that trawl the wards looking for things like mobile phones and unsecured property and valuables - anything that they can sell for a few bucks and since health insurance will only pay a meagre $500 bucks whether i need the simplest cpap or the most expensive category, i would hate to have my asv "walk!"- when i had my cpap trial at the sleep lab, they used a bipap rather than an ASV and they managed to get the AI down to 20 , desaturations to the low 80's rather the low 50's au naturale- they managed to deal with the obstructive events and the hyponeas and it left the centrals. I guess i need to decide whether that kind of control is a reasonable compromise for a few days- It would be so much easier to have a back up machine packed with my hospital bag already to go when i am struck by an MS relapse. I guess i can also keep my eyes open for a used ASV but i won't be holding my breathe!

thanks again for the information!!

[dsm]

Keb SA
Having once lived & worked in SA I am with you.
My middle daughter recent y moved with her 4 kids from Wanganui NZ to Adelaide (Mt Barker)
She was born in Penrith NSW. She sounds like a Kiwi but is in reality an Aussie

I am very fond of Adelaide having lived there 1967-1970 (back in the days of Don Dunstan )

Am happy to provide what expertise I can

Cheers

DSM (Sydney)

[ozij]

Kebsa,

The machine you have ( Synchrony with AVAPS ) is a special class of machine that works differently from others. If in AVAPS mode it is delivering an assured volume & the pressure support is used to make that happen. The sleep doc dials in a tidal volume that is needed & the machine then ventilates to meet that volume for each breath.

Doug, Kebsa, I haven't had a chance to study that Wienmann info, but the above paragraph has me confused.

The Synchrony with AVAPS is a Respironics machine, as is the BIPAP AVAPS you have in your profile, Kebsa.
But in the text, Kebsa refers to a Resmed ASV. If either of you could explain the conundrum it would help me very much.

Thanks
O.