Function of C-Flex

[hrc54]

Hi-

I was wondering if the C-flex function on the Respironics machine (in addition to exhale relief) serves to prevent apneas that might happen to some on the exhale?

Bob

[CollegeGirl]

All Cflex does is lower the pressure slightly on exhale. However, it is designed to make sure that lowering of the pressure does not allow you to have apneas when you go from exhale to inhale (as that's when most apneas happen). It does this, in layman's terms, by kicking the pressure back up to your prescribed pressure right at the moment before you inhale.

There's no special feature to it that helps prevent apneas on exhale - but you're still getting most of your prescribed pressure (most, not all), so that prevents a large part of your apneas. And, as I said, most people's apneas happen on inhale.

Hope that helps.

[Goofproof]

C-Flex is a comfort feature, it has more to do with helping you than treating you. The pressure is what keep the airway open. Jim

[Bogof]

I've heard it is especially good for those who have lower lung capacity or weaker lung muscles. They tend to have less powerful exhalations so reducing the PAP on exhalation prevents the user from struggling to breathe out.

But yeah, for me it's been a matter of comfort too. Much better than the old systems!

[WillSucceed]

CollegeGirl wrote:

It does this, in layman's terms, by kicking the pressure back up to your prescribed pressure right at the moment before you inhale.

Not! C-FLEX only relieves the pressure for a very BRIEF period at the start of exhalation AND it kicks the pressure back up well before you start your next inhalation. This is why some have trouble with C-FLEX as the pressure increase (when the C-FLEX effect stops) can trigger some to start an inhalation BEFORE they have fully finished their exhalation.

[rested gal]

No matter what, C-flex gives some drop at the beginning of an exhalation and lets the regular pressure come back in before the exhalation is finished. What happens after the exhalation starts and before it ends is very dependent on each person's exhalation "style" (for want of a better word.)

I think how long (as well as how much) C-Flex keeps the pressure down during an exhalation depends quite a bit on how steady the force of the exhalation is.

So, both CollegeGirl and WillSucceed are right for some scenarios, imho.

If a person normally exhales with the same amount of force until very close to the end of the exhalation, C-flex will not let the full pressure back in until just before the end of the exhale. The way CG described it.

If a person's exhalation begins losing its starting force almost immediately, C-flex will give only a momentary drop at the beginning and will let the regular pressure come back in long before the soft exhalation is finished....will let it come back in the instant the machine senses that the exhalation is starting to lose the force it had at the beginning. The way WillSucceed described it.

Either way, the regular pressure will be back in place before the end of the exhalation...therapeutic pressure will already be blowing before a person starts to inhale again.

Depending on how they normally exhale, the drop would stay down until almost to the end of the exhalation for some people. For others, the drop would be only momentary. And for others the move back up to "regular" pressure could happen anywhere else within the exhalation. For me, it's at about the halfway mark.

And it can vary for a person. Not all the exhalations being exactly the same anyway.

I could be wrong, but that's my understanding of how C-Flex works.

[Guest]

Apneas occur on EXHALES, not inhales.

[daelic]

Apneas occur on EXHALES, not inhales.

And here I was thinking that an apnea occurs when you weren't exhaling or inhaling.

[Goofproof]

Apneas occur on EXHALES, not inhales.

And here I was thinking that an apnea occurs when you weren't exhaling or inhaling.

I think you might have a point. Jim

[CollegeGirl]

Taken from the Respironics site:

How C-Flex works.
The difference that patients feel when using C-Flex comes, in large part, from Digital Auto-Trak®. This patented algorithm precisely
identifies the transition between inhalation and exhalation – even in the presence of mask leak and other variables. Digital Auto-Trak
helps therapy feel more natural by matching therapy to the patient’s natural breathing pattern. And by matching the patient’s breathing
pattern, C-Flex can reduce pressure at the moment of expiration.
With three C-Flex levels, patients have the ability to select the level of pressure relief that’s right for them. The amount of pressure
relief will vary on a breath-by-breath basis depending on the patient’s expiratory flow and the C-Flex setting. The device returns to the
prescribed pressure at the end of exhalation to ensure proper therapy.

This is what the machine's algorithm is designed to do, and it functions successfully this way for most people. I was told by a Respironics rep that if it does NOT function this way for you, either the patient is so anxious that they cannot stop focusing on their breathing and just breathe naturally, or the machine is not reading the breath pattern properly, because the breath pattern is substantially different from what the machine is programmed to recognize.

That makes a lot of sense to me.

Will, I (and others here) would like to know if there's some way we can help you with your treatment. We are concerned about you, as your answers are getting snippier and more sarcastic every time. As I'm sure you know, this can be indicative of improperly treated OSA. If there's nothing wrong with your treatment, then please keep your disagreements courteous and professional. If you disagree with something I say, that's fine. There's no reason at all to be nasty. Thank you.

Now, to address what our friend Research_Guy had to say (Guest post all you want, buddy, we know it's you. ) It is my understanding (from everything I've read about apnea) that apneas most frequently happen on inhale. The exhale completes, the airway shuts, and when the person tries to inhale, they can't. It would make no sense at all to allow any sort of exhale relief if apneas happened during exhalation. If that's the ONLY time they happened, then it would be much more necessary to have full pressure on exhale rather than on inhale. We'd have "inhale relief" instead. If you disagree, please post more information, as we all need to be educated, as I do believe the majority of us take for granted that apneas happen most often during inhale. Thanks.

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, C-FLEX, auto

[rested gal]

Taken from the Respironics site:

The device returns to the
prescribed pressure at the end of exhalation to ensure proper therapy.

(bold emphasis added by College Girl)

This is what the machine's algorithm is designed to do, and it functions successfully this way for most people. I was told by a Respironics rep that if it does NOT function this way for you, either the patient is so anxious that they cannot stop focusing on their breathing and just breathe naturally, or the machine is not reading the breath pattern properly, because the breath pattern is substantially different from what the machine is programmed to recognize.

That makes a lot of sense to me.

What makes even more sense to me ( ) is that the quote from Respironics was written by one of the marketing people. I'd change "at the end" to "before" or "near" or "by" the end of exhalation.

I'd also question the Respironics rep's notion that if C-Flex does not prevent the prescribed pressure from being in place before the absolute end of exhalation for most people, something has to be wrong.

As far as I've been able to tell when experimentally using all kinds of different exhale forces while watching the pressure on the machine, the duration of C-flex's drop during an exhalation is extremely dependent upon the steadiness of the force of the exhalation.

The slightest dwindling in force starts bringing the dropped pressure back up. I doubt if anyone's exhalation is as forceful near the end of the exhalation as it is at the beginning, but maybe I'm wrong about that. Isn't it natural for every exhalation to begin waning in force before it's completely finished?

Perhaps an RT could describe how most normal people exhale. How goes the flow, so to speak.

The only way I can imagine C-flex keeping the pressure reduced all the way to the very end of an exhalation would be if the person were exhaling in huffs. With no waning of the latter part of the exhalation at all. Just an abrupt stop at the end of the exhalation.

Maybe it's just a matter of semantics -- the power of a tiny preposition!! LOL!!

"at the end" is not the one I'd have used if I were writing the C-Flex blurb.

Wouldn't be the first time I was wrong. It also wouldn't be the first time Respironics explained C-Flex in an inadvertently misleading way. Remember the graph they used to have that made it look like a C-Flex setting of "1" dropped pressure 1 cm, "2" dropped it 2 cm's, etc.? They later changed that graphic (or the text for it) to make it clear that the setting number does not necessarily reflect the amount of drop in cm's.

[bluegrassfan]

Hmmm...got me thinking about why last three nights I've logged on my tape recorder waking up every hour from 12pm to 5pm. The last few times this morning I woke, I sensed I wasn't getting enough air, and I actually lifted the comfortgel off my nose to breathe thru my mouth. My cflex is set on 3. I think I'm going to cut off cflex again and see if it solves that problem. bob

[rested gal]

Hmmm...got me thinking about why last three nights I've logged on my tape recorder waking up every hour from 12pm to 5pm. The last few times this morning I woke, I sensed I wasn't getting enough air, and I actually lifted the comfortgel off my nose to breathe thru my mouth. My cflex is set on 3. I think I'm going to cut off cflex again and see if it solves that problem. bob

That's worth a try, but my bet would be that the CPAP pressure itself might not be quite enough.

[hrc54]

Thanks all. I much appreciated the well thought-out responses. I've always thought that there was a purpose for the exhale relief & reasons why it increases BEFORE next inhalation.
I hope that sounded right. Or phrased better why it drop pressure for ALL of the exhalation.

Bob

[WillSucceed]

CollegeGirl wrote:

Will, I (and others here) would like to know if there's some way we can help you with your treatment. We are concerned about you, as your answers are getting snippier and more sarcastic every time. As I'm sure you know, this can be indicative of improperly treated OSA. If there's nothing wrong with your treatment, then please keep your disagreements courteous and professional. If you disagree with something I say, that's fine. There's no reason at all to be nasty. Thank you.

Well now wasn't that a mouthfull! Unfortunate that you found my posting snippy and sarcastic as it was intended as neither. Further, upon re-reading it, I don't think there is any snippyness nor sarcasm to it.

I do believe that your explanation of C-FLEX, based on your quotation from the Respironics marketing department is both inaccurate and inadequate. Rested Gal, in her explanation, describes flow degredation as the factor that C-FLEX is likely responding to; I suspect that she is right. However, I still believe that C-FLEX finishes it's pressure relief WELL BEFORE the user has finished exhalation. After all, it is CPAP, not Bi-Pap. If you look at the C-FLEX waveform that Respironics has shown in their literature, you can see that the C-FLEX effect is ending well before the end of exhalation. It is most certainly NOT "kicking the pressure back up to your prescribed pressure right at the moment before you inhale" as you have stated.

Regarding your comments to me personally CollegeGirl, my treatment is going just fine. IF you were really worried about my treatment, you would have commented long before now rather than embed your pot-shot about sarcasm being an indicator of inadequate treatment. This sort of passive-aggressive crap is thinly-veiled at best and certainly does not convey any genuine concern.

Further, this "I (and others here)" comment is a really nice way of not taking full responsibility for one's own statement. Speak for yourself CollegeGirl, and let others speak for themselves. If you and others are having little side-bars about people on this forum, go for it but don't, for a moment, think that it in some way gives your commentary any more credibility than it actually has.

I think what is really going on here is that you don't like it when your comments, which you think are unassailable fact, are challenged by someone else. You don't like that your comments are challenged? Hard cheese.

Back to class CollegeGirl... you've got some more learning to do and, even more importantly, some growing up to do! You want snippy sarcasm? Keep going and you will get it.

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, C-FLEX, CPAP

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, C-FLEX, CPAP