Does more C-Flex increase the base pressure?

Malibu · Post by **Malibu** » Sat Oct 07, 2006 5:12 am

Question for all that use C-Flex....

I am using C-Flex on 2 and have found the AHI to have risen a slight amount compared to 1 and a moderate amount compared to no C-Flex.

Do you raise the pressure a tad to compensate for the C-Flex to help lower the AHI?

I feel much better rested using C-Flex at 2 even though my pressures are 6 to 7 auto.

Thanks,

Marc

JeffroDoe · Post by **JeffroDoe** » Sat Oct 07, 2006 6:17 am

All the cflex does is offer an exhalation relief. It should have very little impact on your AHI. Most OSA occurs at the bottom of the cycle as you go from exhalation to inhalation. Therefore, the use of flex at 2, rather than one, may be encouraging you to remain in the exhalation stage longer than you would have at 1.

You must not micro-manage this. Each change you make to your set up takes time to adjust to. If it's only been a couple nights, try again for a few nights without pouring over the numbers daily. Micromanaging like that can have a negative effect on your therapy, due to increased anxieties and worrying. It's ok to be involved in your own therapy, and it's ok to have a say in how you are treated. However, there is a point where you need to back off a bit and relax, and don't freak out over every change or variation you encounter. I'm not suggesting you are freaking out, I'm just offering a general recommendation on numbers monitoring.

_________________

rested gal · Post by **rested gal** » Sat Oct 07, 2006 6:34 am

Hi Marc,

I'm not a doctor or anything in the health care field. With that out of the way ... this has been my experience when I used the Respironics REMstar Auto with C-flex for about a year.

I did not raise the pressure settings while using C-Flex at any of its 3 comfort settings. I never really paid any attention to whether the AHI I got (almost always below 3.0, often down in the 1.x range) changed depending on which degree of C-Flex I had set.

The first six months or so, I had C-Flex set at 3 for the most exhalation relief. The remainder of the year I put it at 2, which made the transition seem smoother when the "regular" pressure comes back in (as it's supposed to do) before the exhalation is entirely finished.

I do know my AHI varies from night to night on any machine, with or without C-Flex. After I got past scrutinizing every decimal point (not that that's what you're doing, but I sure did for a long time ) I found that a good bit of AHI variation is to be expected, and that wayyyy too many factors will be at play to be able to pinpoint one single reason for the variations very well.

I suppose when we describe things as having risen a "slight amount" or "moderate amount", what one person would consider slight, another might consider so negligible as to not matter at all. For me, any AHI variations that stay below 3.0 don't really matter at all. I used to wonder, "Hmmm, wonder why it was 1.3 AHI two nights ago, but was 2.4 last night?" Over time, I saw the 1.0 range and below so often that it would take a 3.x to make me look to see, "Why?" And most often that would be because tape had worked loose and I'd been getting higher leaks (mouth leaks) than usual.

Sidenote: Under 5.0 is "normal", but on my own data I want to see it be well below 3.0 since I know AHI down in the 1.x range is what I normally get using cpap if there are hardly any leaks.

I know what you mean, though, Marc. If a person absolutely consistently sees a higher or lower AHI depending on what C-flex setting used, it's interesting to know "why?" "Why" is one of my favorite words. I like "What if...?" pretty well, too.

Malibu wrote: Do you raise the pressure a tad to compensate for the C-Flex to help lower the AHI?

No, I don't. I've messed around with pressures quite a bit, but was not thinking of C-Flex needing any compensation. I suppose that could be the case for some people. I'd think Respironics (and competitors) studied C-Flex quite thoroughly, and I believe if a significant number of people needed the pressure raised a bit more when using C-Flex, that would have already been "out there".

That's not to say that you might not need a tad more pressure when using C-Flex. Given how many ways OSA can happen and how different all of us are, even a very minor aspect of your particular sleep disordered breathing or your particular airway anatomy could make that be true for you.

Malibu wrote:I feel much better rested using C-Flex at 2 even though my pressures are 6 to 7 auto.

That's what really matters, imho -- how you feel. Sounds like you've got your treatment dialed in well.

dsm · Post by **dsm** » Sat Oct 07, 2006 6:18 pm

Marc,

Just to add to the already posted good advice.

The Remstar machines all sense the pressure being delivered and do a very good job of holding the machine to that setting. They do this with a pressure sensor that samples the air pressure just to the point the air exits from the machine.

I have done tests that show that at this air exit point, with a cms dial gauge inserted in the circuit (air tube) - that the pressure remains very constant with very little fluctuation no matter what cflex setting you set the machine to.

If the cms starts to rise above the current cms setting the machine is applying, then the blower motor is adjusted in speed so the the cms remains constant.

If I deliberately blow hard during an exhale, the gauge does move a little but the machine (Remstar Auto w cflex) generally holds the cms to the setting it is working with. By 'the setting' I am meaning the CMS that the machines is currently working to allowing that Autos will vary this setting as they adapt to changing conditions detected from the user.

If your AHI is going up because of changing the cflex settings, it may have more to do with the speed of the recovery from the 'cflex delay dip'. By this I am referring to the fact that at a cflex setting of 3, there is a much bigger delay dip in resuming full cms than there is with a setting of 1. Once the machine decides to end the 'dip/delay' the pressure increases rapidly (this speed is greatest at cflex 3 & least at cflex 1).

I believe it is this speed of recovery from the cflex dip/delay that may be impacting your AHI. In Bilevels the transition from exhale pressure (epap) to inhale pressure (ipap) is called 'rise time'. So put another way, cflex rise time is a factor that can conceivably cause people problems. On bilevels it can be adjusted. On cflex I don't believe the actual rise time can be altered, only the level of cflex.

When I was using cflex, I could not cope with a setting of 3. I tended to use mostly 1 sometimes 2. My symptoms were mouth pops & increased aerophagia. I didn't actually do any tests to compare AHI variations using different cflex settings. However, if some one wanted to do such a test I am sure we could devise one (say 2 days each at 1, 2 and 3 cflex) and study a few results. If cflex was the cause I am sure it would show in any such test.

DSM