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Anonymous wrote: Muck-
-that is how cflex is supposed to work. If you want a machine that will maintain a reduced pressure throughout your expiratory cycle you need to get a bipap.

I'm aware of how c-flex works... you must be misinterpreting my description. I am refering to a pecepted change in pressure that is not perceptable in a non-leak condition... and YES it does occur just before the begging of my inspiratory cycle without regard to the actual stated transition of the c-flex feature.

wading thru the muck! wrote: <snip>
Hey Doug,

How many women on the forum are you trying to woo with all your flattering remarks! (all in one thread!)

LOL!

If only your "down under" dialect would translate via the computer, you'd have them all swooning.

Jeeze Wader,
if I were to speak me normal a'strine accint they mite run a mile mate!

The ozzie way ov talkin s'not az kultured az ya mite think

But I dunno. maybe it is a turn on, I gess it seemed to werk for ole crockadile dundee

D

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CPAPopedia Keywords Contained In This Post (Click For Definition): wader

wading thru the muck wrote:I am refering to a pecepted change in pressure that is not perceptable in a non-leak condition... and YES it does occur just before the begging of my inspiratory cycle without regard to the actual stated transition of the c-flex feature.

Muck-
-With cflex enabled -leak or no leak- the pressure is supposed to be reduced at the point of exhalation and supposed to be increased before the beginning of your inspiratory cycle. Still not following why you would think being able to perceive this change could be considered a problem.

-In a leak condition the machine detects the leak via the airflow signal and is supposed to immediately ramp up the pressure to compensate. It is doing its job. If you are awake when this happens you are bound to perceive this boost in pressure. Again not following why you would think being able to perceive this boost in pressure could be considered a problem. I'd be inclined to think just the opposite: if it didn't boost the pressure to compensate for the leak, then that would indicate a problem.

Wading,

I hear what you're saying. I cannot tolerate cflex, either. When I first got my machine, I was really thrilled at the prospect of it - until I used it. I am not one who scares easily, but to say I woke up panicked, thinking I was having some type of respiratory or cardiac event from not being able to catch my breath, believe me.

Just recently, I revisited using it, almost one year into treatment, and still had a very negative reaction to it once again. Couldn't breathe and found it was literally keeping me awake due to just noticing every breath I took. There is just something about it, which my unscientific mind cannot explain, that is incompatible with my way of breathing. I don't think it's necessary to go into all this engineering/scientific explanation or to suggest someone can't be feeling what they're feeling because it's akin to when a physician gives you a pill that "has little to no side effects," yet the patient breaks out in hives or gets such a stomach upset that they have to discontinue its use. There are no explanations sometimes as to why people react to certain stimuli, whether it be medications or other things. I think we all react differently to different situations, regardless of what the books and experts may believe can or cannot happen.

So I guess, like you, I will remain someone who doesn't use her cflex again.

Anonymous wrote:
Muck-
-With cflex enabled -leak or no leak- the pressure is supposed to be reduced at the point of exhalation and supposed to be increased before the beginning of your inspiratory cycle. Still not following why you would think being able to perceive this change could be considered a problem.

I know what it is "supposed" to do. I'm saying that what it is doing is something other than that and ONLY when there is a leak. As I said, I can make it immediately perform correctly by closing the leak. This has not been a "problem" for me, but others have complained of what they referred to ask "stacked breathing" in which this tendency for the c-flex to speed up the respiratory cycle by perceptibly boosting pressure just premature of the normal transition from expiration to inspiration.

...Just passing along my experience 'cause it sounded similar to what has been described by dsm/Bella.

...Not try'in to reinvent the explanation of how c-flex works.

wading thru the muck! wrote:I know what it is "supposed" to do. I'm saying that what it is doing is something other than that and ONLY when there is a leak. As I said, I can make it immediately perform correctly by closing the leak.

Yes, the machine is performing correctly when pressure is increased to compensate for a leak and, yes, the machine is performing correctly when the pressure drops back down when you've closed the leak.

wading thru the muck! wrote:This has not been a "problem" for me, but others have complained of what they referred to ask "stacked breathing" in which this tendency for the c-flex to speed up the respiratory cycle by perceptibly boosting pressure just premature of the normal transition from expiration to inspiration.

Yes, I've read of this complaint. Cflex provides only a momentary pressure drop at the point of expiration. The pressure does not remain decreased through to the normal transition from expiration to inspiration. That's what a bipap is designed to do. By design, cflex returns to the inspiratory pressure before that point to achieve Positive End Expiratory Pressure (PEEP). I understand some people are bothered by this perceptible boost in pressure. Glad to hear it has not been problem for you.

Sleepless on LI wrote:I don't think it's necessary to go into all this engineering/scientific explanation or to suggest someone can't be feeling what they're feeling

Please don't feel we are pressuring you to understand the technology involved. You shouldn't be concerned that you can't comprehend the engineering/scientific explanation supporting the technology. As you've stated, what's important to you is that you know whether or not you like or dislike the feel of cflex. I was addressing Muck regarding the engineering/scientific explanation because he presented it for discussion. No one is suggesting you're not feeling what you're feeling. Muck and I were discussing the science behind the feeling.

Anonymous wrote:

Sleepless on LI wrote:I don't think it's necessary to go into all this engineering/scientific explanation or to suggest someone can't be feeling what they're feeling

Please don't feel we are pressuring you to understand the technology involved. You shouldn't be concerned that you can't comprehend the engineering/scientific explanation supporting the technology. As you've stated, what's important to you is that you know whether or not you like or dislike the feel of cflex. I was addressing Muck regarding the engineering/scientific explanation because he presented it for discussion. No one is suggesting you're not feeling what you're feeling. Muck and I were discussing the science behind the feeling.

Thanks for the kind explanation. I don't feel pressured, honestly. I am not a technical-minded individual and have given up trying to be, so I just go by what works or doesn't work for me. But I appreciate the reply, thank you.

Anonymous wrote:
Yes, the machine is performing correctly when pressure is increased to compensate for a leak and, yes, the machine is performing correctly when the pressure drops back down when you've closed the leak.

I am NOT referring to a pressure increase relative to the leak. I am referring to a perceptible pressure "bump" that reoccurs just prior to the beginning of each inspiratory cycle. It is NOT the general increase in pressure related to the machine trying to compensate for the leak.

I am also NOT saying that the pressure decreases when the leak is closed, but the perceptible "bump" is no longer perceptible.

Anonymous wrote:
By design, cflex returns to the inspiratory pressure before that point to achieve Positive End Expiratory Pressure (PEEP). I understand some people are bothered by this perceptible boost in pressure. Glad to hear it has not been problem for you.

As I said, this is only perceptible (for me) while in a leak condition. Otherwise , the transition is completely imperceptible.

Muck-
-I believe I now understand what you are saying. With the cflex feature enabled, the momentary decrease in pressure upon exhalation is followed by the increase in pressure. This transition is imperceptible to you under normal conditions, but when your mask is leaking you are able to sense this increase in pressure and describe this sensation as a "boost" or "bump".

I appreciate the clarification as well as the discussion.

Wader,

Re the effects of c-flex. I have commented several times over the past year of how I was using c-flex then after experiencing what I call 'mouth-pops' and significant aerophagia, I began to wonder if it was the c-flex somehow triggering the effect.

It is important to note that those of us at 15 cms, tend to be in a higher than average CMS band of xPap users so we may notice things differently to people on say 10-12 cms.

Also of note, I believe 15/16 cms is the threshold over which mask leaks become difficult to manage for most of us & one either has to strap the mask on uncomfortably tightly (if a f/f mask) else put up with 'face squeaks' all night.

What I became aware of is what I call the 'cflex fade - air rush'. On a cflex setting of 3, I was very aware of what seemed like an acceleration of air after cflex had done its bit of lowering CMS after which pressure 'accelerates' back up to normal pressure & perhaps a bit beyond.

If I was breathing heavily (compared to softly once relaxed), this 'cflex fade - air rush' didn't seem to matter as much but if my breathing was softer (as is natural when we drift off) then the 'cflex air rush' seemed more noticable and to my mind was contributing to aerophagia. I then tried the machine without it and noticed a big drop in the incidence of 'mouth pops' and aerophagia.

Later I resumed using cflex but kept it to a setting of mostly 1.

Allowing that cflex machines have pressure sensors & that these are 6' away from your face, my rationalizing was that the air flow may actually increase momentarily past the normal pressure until the backwave is picked up by the pressure sensor & it drops the cms back to the correct setting. That I believe could cause 'bumps'.

I notice that Puritan Bennett have designed their machines such that the pressure sensing is done at the mask & not at the machine. Clearly they had a reason for doing so.

I am also wondering that re my Bipap S/T, that if I can find a way (like the Puritan Bennett machines) to run a pressure sensor line up to my mask and have the Bipap S/T sensing pressure at my face, that it may have some effect on the flipping problem. - I will see if this is possible (am sure I can find a way). If so then I will report back on the results.


Summarizing:
==========


cflex
1) at high CMS, I believe a high c-flex setting can cause an accelerating air pressure increase after the cflex has done its bit.

2) It seems possible that the pressure may accelerate a couple of cms past the current upper cms setting until the backwave reaches the pressure sensor wich then adjusts the pressure down again.

3) this condition could be tunable, by this I mean it may have peak effect at particular pressure settings combined with the length of the airhose.

4) This situation could be made worse if there is a concurrent leak. It is also possible that the 'air rush' of a high cflex, may be enough to open a leak & thus add even more pressure until the machine attempts a correction.

5) that this condition may be exacerbated because most machines sense the pressure at the machine air-outlet rather than the mask.


This discussion has opened up the opportunity to try some additional experiments re extending the pressure sensing line up the airhose on my Bipap machines. It may not be the way to solve all these issues but at least it may help better understand what might be occurring.

DSM

Further to the last post.

It just occured to me that my masks are 7' from the machine as I have the 1' extension that came with the Resmed mask.

I does seem quite possible that shortening the hose may change the dynamics enough to solve part of the problems we are speaking of, or at least change them such that we can beging to predict how a particular set up will behave.

DSM

DSM-Guest wrote:Summarizing:
==========


cflex
1) at high CMS, I believe a high c-flex setting can cause an accelerating air pressure increase after the cflex has done its bit.

dsm, since C-Flex (by deliberate design) will always bring the pressure back up before the exhalation is finished, there will always be an air pressure increase up to what the current pressure was "after the C-Flex has done its bit" - no matter what the current pressure was...even if it was delivering only 5 or 6 cms.

Of course if a person is currently at a higher pressure that feels like a lot to them anyway, that pressure coming back in before the exhalation is finished can feel like quite an acceleration, as you say. Many people do find that pressures of 15 and above are difficult to breathe out against. At 15 and above, C-Flex does not make enough of a dent (or last long enough during the exhalation) to give me any kind of comfort at all. Personally, if I had to have that kind of pressure (or, for that matter, 13 or 14) all night, I'd definitely want to use a bi-level machine. Preferably the combo BiPAP Auto by Respironics.

Quick disclaimer!!! No, I have no agenda to push Respironics machines...that just happens to be the only machine in the world to date that can deliver both kinds of treatment (bi-level exhalation relief AND auto-titrating capability) simultaneously.

DSM-Guest wrote:2) It seems possible that the pressure may accelerate a couple of cms past the current upper cms setting until the backwave reaches the pressure sensor wich then adjusts the pressure down again.

Well, I suppose almost anything is possible, but I seriously doubt that any cpap machine designers would allow the machine to use a greater pressure than the prescribed setting. And certainly not "a couple of cms past the current upper cms setting."

DSM-Guest wrote:3) this condition could be tunable, by this I mean it may have peak effect at particular pressure settings combined with the length of the airhose.

If by "condition" you mean you think it takes enough time for air flow characteristics to travel through a 6 foot air hose and reach the pressure sensor inside a C-Flex using machine for that machine to allow the switch back to the current pressure to run up above the current upper cm being used, I don't think that (an acceleration to ABOVE the current pressure) is happening at all. And if that's not happening, there's no tuning to be done.

DSM-Guest wrote:4) This situation could be made worse if there is a concurrent leak. It is also possible that the 'air rush' of a high cflex, may be enough to open a leak & thus add even more pressure until the machine attempts a correction.

Leaks, especially big ones, can certainly cause difficulties.

I don't think "this situation" (if you are again talking about some kind of rather drastic delay in the way the machines which need to sense air waveform characteristics go about their job) is something that is happening or would happen, unless a machine were malfunctioning. A delay in sensing that could result in a "couple of cms" being delivered over the current cm that is supposed to be delivered....well, I just don't think any xpap machine designers would allow such a thing in the design of the algorithms.

DSM-Guest wrote:5) that this condition may be exacerbated because most machines sense the pressure at the machine air-outlet rather than the mask.

My understanding of this (limited, at best!! LOL!!) is that where the sensing takes place really make any difference. What matters is how the algorithms of the respective machines handle what they sense.

Puritan Bennett's designers chose to design their algorithms to use a sensor line running up to (or close to) the mask. Other manufacturers chose to design their algorithms to sense the air flow delivered through the main air hose itself.

Either way, as I understand it, can sense waveform characteristics equally well. Doesn't really matter which sensing method is used as long as the algorithms are well designed to read the air flow and take the proper action.

DSM-Guest wrote:Summarizing:
==========


cflex
1) at high CMS, I believe a high c-flex setting can cause an accelerating air pressure increase after the cflex has done its bit.

dsm, since C-Flex (by deliberate design) will always bring the pressure back up before the exhalation is finished, there will always be an air pressure increase up to what the current pressure was "after the C-Flex has done its bit" - no matter what the current pressure was...even if it was delivering only 5 or 6 cms.

Of course if a person is currently at a higher pressure that feels like a lot to them anyway, that pressure coming back in before the exhalation is finished can feel like quite an acceleration, as you say. Many people do find that pressures of 15 and above are difficult to breathe out against. At 15 and above, C-Flex does not make enough of a dent (or last long enough during the exhalation) to give me any kind of comfort at all. Personally, if I had to have that kind of pressure (or, for that matter, 13 or 14) all night, I'd definitely want to use a bi-level machine. Preferably the combo BiPAP Auto by Respironics.

Quick disclaimer!!! No, I have no agenda to push Respironics machines...that just happens to be the only machine in the world to date that can deliver both kinds of treatment (bi-level exhalation relief AND auto-titrating capability) simultaneously.

DSM-Guest wrote:2) It seems possible that the pressure may accelerate a couple of cms past the current upper cms setting until the backwave reaches the pressure sensor wich then adjusts the pressure down again.

Well, I suppose almost anything is possible, but I seriously doubt that any cpap machine designers would allow the machine to use a greater pressure than the prescribed setting. And certainly not "a couple of cms past the current upper cms setting." "Until the backwave reaches the pressure sensor" makes it sound like there is quite a delay, but I think the sensing is almost instantaneous. Just think about how quickly all bi-level machines sense that an inspiration or expiration has begun.

DSM-Guest wrote:3) this condition could be tunable, by this I mean it may have peak effect at particular pressure settings combined with the length of the airhose.

If by "condition" you mean you think it takes enough time for air flow characteristics to travel through a 6 foot air hose and reach the pressure sensor inside a machine using C-Flex for that machine to allow the switch back to the current pressure to run up above the current upper cm being used, I don't think that (an acceleration to ABOVE the current pressure) is happening at all, although it could certainly feel that way. And if that's not happening, there's no tuning to be done.

DSM-Guest wrote:4) This situation could be made worse if there is a concurrent leak. It is also possible that the 'air rush' of a high cflex, may be enough to open a leak & thus add even more pressure until the machine attempts a correction.

Leaks, especially big ones, can certainly cause difficulties.

However, I don't think "this situation" (if you are again talking about some kind of rather drastic delay in the way the machines which need to sense air waveform characteristics go about their job) is something that is happening or would happen, unless a machine were malfunctioning. A delay in sensing that could result in a "couple of cms" being delivered over the current cm that is supposed to be delivered....well, I just don't think any xpap machine designers would allow such a thing in the design of the algorithms.

DSM-Guest wrote:5) that this condition may be exacerbated because most machines sense the pressure at the machine air-outlet rather than the mask.

My understanding of this (limited, at best!! LOL!!) is that where the sensing takes place doesn't make any difference at all. What matters is how the algorithms of the respective machines handle what they sense.

Puritan Bennett's designers chose to design their algorithms to use a sensor line running up to (or close to) the mask. Other manufacturers chose to design their algorithms to sense the air flow delivered through the main air hose itself.

Either way, as I understand it, can sense waveform characteristics equally well. Doesn't really matter which sensing method is used as long as the algorithms are well designed to read the air flow and take the proper action.

RG,

Many good comments - lets go through them ...

RG>>
dsm, since C-Flex (by deliberate design) will always bring the pressure back up before the exhalation is finished, there will always be an air pressure increase up to what the current pressure was "after the C-Flex has done its bit" - no matter what the current pressure was...even if it was delivering only 5 or 6 cms.
<<

DSM: I thought we all understood this ?. I was highlighting the speed of the recovery back to the upper cms.


RG>>
Of course if a person is currently at a higher pressure that feels like a lot to them anyway, that pressure coming back in before the exhalation is finished can feel like quite an acceleration, as you say. Many people do find that pressures of 15 and above are difficult to breathe out against. At 15 and above, C-Flex does not make enough of a dent (or last long enough during the exhalation) to give me any kind of comfort at all. Personally, if I had to have that kind of pressure (or, for that matter, 13 or 14) all night, I'd definitely want to use a bi-level machine. Preferably the combo BiPAP Auto by Respironics.
<<

DSM: Makes sense to me, only point here for me is I can't get my Respironics Bipap S/T to work well with my Resmed F/F mask & I rely on that mask. So just at the moment I would lean towards another brand (PB, Resmed). I still haven't given up on the Bipap S/T. I will try shortening the air hose & will experiment by running a pressure line up to the mask. I looked at how to do it and can see a way to put it in without making any permanent mods to the machine. I'll let you know what happens.


RG>>
Well, I suppose almost anything is possible, but I seriously doubt that any cpap machine designers would allow the machine to use a greater pressure than the prescribed setting. Shocked And certainly not "a couple of cms past the current upper cms setting." "Until the backwave reaches the pressure sensor" makes it sound like there is quite a delay, but I think the sensing is almost instantaneous. Just think about how quickly all bi-level machines sense that an inspiration or expiration has begun.
<<

DSM: Yes, on reflection an overshoot of 2 cms could seem high but you are overly optimistic that the designers can control the pressure to the extent that a machine won't fluctuate a bit in pressure depending on what is happening. So much about xPAP is still feeling the way forward. This is *not* yet an exacting science.

As for sensing air pressure being instantaneous at 2 ends of a 7 foot tube, RG, that is a surprisingly naive statement. Air unlike water does compress - substantially.

If we were measuring water pressure in a tube (like a cpap tube) 6 to 7 feet away from where the pressure is being applied then yes, any pressure & vibration is almost instantaneously transmitted because water doesn't compress. The tube holding the water may flex but that would have a tiny effect given the dimensions. Not only does air compress but there are pressure waves and these could be noticable over a 7 foot tube. I snort at one end - it *won't* be picked up instantaneously at the other end, certainly not the way it would if hydraulics were involved.



RG>>
If by "condition" you mean you think it takes enough time for air flow characteristics to travel through a 6 foot air hose and reach the pressure sensor inside a machine using C-Flex for that machine to allow the switch back to the current pressure to run up above the current upper cm being used, I don't think that (an acceleration to ABOVE the current pressure) is happening at all, although it could certainly feel that way. And if that's not happening, there's no tuning to be done.
<<

DSM: I don't believe I said 'airflow' characteristics - I was writing about pressure being transmitted from the mask to the sensor over a 6/7 foot tube.

I will do some more thinking about the cflex 'bounce' observation, but there is sense to your point that as the pump and sensor are at the machine end, the sensor will detect the max pressure before the person at the other end of the hose (unless you want to persist with the notion that air pressure will be instantaneous at both ends of the 6/7 ft tube ).


RG>>
Leaks, especially big ones, can certainly cause difficulties.

However, I don't think "this situation" (if you are again talking about some kind of rather drastic delay in the way the machines which need to sense air waveform characteristics go about their job) is something that is happening or would happen, unless a machine were malfunctioning. A delay in sensing that could result in a "couple of cms" being delivered over the current cm that is supposed to be delivered....well, I just don't think any xpap machine designers would allow such a thing in the design of the algorithms.
<<

DSM: That was naughty introducing the word 'drastic delay' what justified that ? - what I have been talking about are subtle effects. I don't think anything I said implied drastic or anything like it.

Again, yes a couple of cms over could seem high, you may be quite right, I was exploring an idea - maybe that aspect needs further thinking about

But bear in mind that the user is breathing out and they are exerting an air pressure in direct opposition to and overcoming, the machine pump, this seems like a spoiler in your argument. The air pressure is not all controlled by the machine pump and sensor, the user also is exerting some control. Also, because of the air circuit, one end has an affect on how the other behaves (unpredictable human vs predictable machine).


RG>>
My understanding of this (limited, at best!! LOL!!) is that where the sensing takes place doesn't make any difference at all. What matters is how the algorithms of the respective machines handle what they sense.

Puritan Bennett's designers chose to design their algorithms to use a sensor line running up to (or close to) the mask. Other manufacturers chose to design their algorithms to sense the air flow delivered through the main air hose itself.

Either way, as I understand it, can sense waveform characteristics equally well. Doesn't really matter which sensing method is used as long as the algorithms are well designed to read the air flow and take the proper action.
<<

DSM: I am not a pneumatics engineer but I know enough about air to say that where the sensing is done does matter providing you know what sensing you are talking about. You seem to keep confusing 'airflow' and 'pressure'. Re-read your last para, you begin talking about pressure sensing then switch to completing your point while talking about 'airflow' sensing - two very different things, which indicates you may not have a clear picture of what is going on in the mask - tube & the machine.

Yes the 'airflow' is sensed at the machine end & that is as good a place as any to sense it. In fact it would be ridiculous to try to sense the 'airflow' at the mask end (think about it) but pressure sensing is very different and the absolute best place to sense that is at the mask end - just as PB do. That is not a trivial flip of a coin design decision (ask yourself which end of the tube has the OSA, the user or the machine).

Your comments on this aspect reflect a non-technical mind and that is fine. You aren't expected to have such mechanical insights. Leave that to the engineers.

But RG as always, you really make us earn our points & I believe we all benefit from it.

Luv DSM

(wouldn't it be great if married couples could discuss things as politely and nicely as this )

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[quote="dsm"]Bella,

....I have now got a copy of the provider manual are you refering to section 3.5 Digital Auto-Trak sensitivity.

DSM