How does C-flex actually work?

Snoozing Gonzo · Post by **Snoozing Gonzo** » Fri Mar 31, 2006 10:11 am

I understand that C-flex supposed to be easier to exhale and I'm curious as to what is actually happening. Does it decrease exhale pressure like a quasi-Bipap? I've played with the settings a bit and it seems that the change is a timing thing where the pressure change (if that's what it is) is on a sequence that is partially effected by actual exhale timing.

I am at an 8cm straight CPAP and having the C-flex option disabled is not a difficulty but there is a definite difference with C-flex. Just curious.

Brent Hutto · Post by **Brent Hutto** » Fri Mar 31, 2006 10:32 am

At the moment you transition from inhalation to exhalation, C-flex lets the pressure drop slightly and momentarily. The duration of that drop varies slightly but is just a fraction of your total exhalation period (maybe 1/4 to 1/3). The amount of the drop is proportional to the setting (C-flex 1, 2, 3) and to the forcefulness of your exhalation. Probably a couple cm or so in most cases. Not nearly the same as BiPAP but still more comfortable to a lot of folks apparently.

Guest · Post by **Guest** » Fri Mar 31, 2006 10:47 am

The short answer (per Respironics) is:
"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."

In other words, it is an undefined drop in pressure because the harder you exhale, the greater the pressure relief you will experience. There are 3 settings. Setting 1 will give you the least exhalation relief.

With a bi-level machine, such as Respironics' Bi-Pap, the pressure relief you experience upon exhalation is a set pressure drop (you can set it yourself to what's most comfortable and gives you the best results based upon the software data) and is not dependent upon the force of exhalation.

The best way to understand how it works is to read the manufacturer's literature on it.
Here are some links you can click on that include animated explanations, brochures you can download, and several studies:

C-Flex Technology
C-Flex Literature
Proof Sources

Snoozing Gonzo · Post by **Snoozing Gonzo** » Fri Mar 31, 2006 12:02 pm

Thank you for the explanations and links. It seems like the higher the setting the more relief there is but it returns faster making me breath faster. A long exhale seems to change that for a few seconds. Other than curiosity, I find myself occasionally taking very long, deep breaths or sighs during the night like I was trying to catch up with an air need. I don't know if they show up on the data output as I don't have a reader and software yet and dependant on downloads at the DME. It’s not uncomfortable or disturbing, I'm just trying to get everything figured out. (It’s nice to have curiosity again - I didn't know it was missing until a few weeks into CPAP - another benefit!)

Guest · Post by **Guest** » Fri Mar 31, 2006 12:23 pm

There are some people don't like C-Flex. This is from a post by WillSucceed:

WillSucceed wrote: <snip>

Some users don't do well with C-FLEX as it can trigger breath-stacking. The exhalation relief from C-FLEX is NOT for the entire length of time that the user exhales -relief is only provided at the beginning of exhalation. For some users, their normal exhalation is cut short by the increase in pressure when the brief C-FLEX relief ends. These users begin an inhalation before they were finished exhaling. The breaths become shorter and more rapid. The user wakes up gasping / panting for air.

This does not happen to everyone and, for many users, C-FLEX is a good thing. However, if you are one of the users who does not like C-FLEX, you have the option of turning it off.

Here's a link to the entire thread: C-Flex Setting

Snoozing Gonzo · Post by **Snoozing Gonzo** » Fri Mar 31, 2006 2:08 pm

Sounds a bit familiar. I was going the wrong way. I'll back the C-flex off and see what happens. Then I may have it turned off for a few days just to experiment. When I have the software, I'll re-run the experiment and see what it shows, if anything.

Thanks for taking the time to provide the info.

Guest · Post by **Guest** » Fri Mar 31, 2006 3:16 pm

You're welcome!

Guest · Post by **Guest** » Sat Apr 01, 2006 1:46 pm

C-Flex works great but your pressure of 8cm is probably too low to really take advantage of it. Setting the C-Flex setting too high can make you feel like your hyperventalating. Try setting 1 or 2 or turn it off.

Choosing "CPAP" vs CFLE in the setup menu disables it.

Swordz · Post by **Swordz** » Sat Apr 01, 2006 11:56 pm

Great thread, definitely provokes my thoughts again about BiPap effectiveness in my situation. My doc is persuading me against Auto BiPap, which has Biflex. I explained Cflex is temp exhalation relief, while Bipap is exhalation relief during the whole exhalation process. I'm thinking its another one of those things they say, but he doesn't have OSA or ever personally used either.

Another good thing about the new Respironics Auto Bipap is the algorithim, though not necessarily new, is suppose to make the whole breathing process more natural. Cflex helped me, but it didn't seem natural, but not sure why.

Darth Vader Look · Post by **Darth Vader Look** » Sun Apr 02, 2006 1:31 am

C-Flex works great but your pressure of 8cm is probably too low to really take advantage of it.

My Auto is set to 7cm with a C-flex setting of 1 and only due to the activa mask I wear. Just before that I had the flexi-fit 431, lower setting of 6cm and c-flex set to 3 and it worked like a charm.