Higher AHI with CFLEX+ - maybe

[kcellwood]

About two weeks into CPAP using a pressure of 8. When the machine was set up the FLEX was not turned on and my AHI was 2-3 for the first three days. I started playing with the FLEX and went to CFLEX+ and AFLEX with a constant pressure of 8. Various relief numbers. I did this for about a week and my AHI jumped to 9-12 range for the entire time. Two nights ago I went back to just CFLEX with a relief of x1 and my numbers are back down to 2-3 for the two days. I plan to stay this way for a week to see how it goes. I may go back and play with all the Flex settings just to see how the numbers trend.
During this high AHI, my number was made up of mostly CA's and hypopneas.

I am very comfortabele where the setting is now using just the CFLEX x1. I could sense the slight difference when using the CFLEX+ and AFLEX. Just prior to the end of my inhalation the pressure would drop. Even with such a small drop it still felt to me like I was not completing my inhalation. I am sure it is just how I perceived it.

[igdoc]

Good to see that your findings are the same as mine. It looks like you have mild CPAP induced central apneas/hypopneas or complex sleep apnea. As many as 80% of people with this will improve spontaneously within 4 to 8 weeks of CPAP treatment as the body adjusts the CO2 apnea threshold. The other 20% will need to change to expensive ASV machines (or sometimes bilevel with backup rate) to control the central apneas. It looks like you will be able to get satisfactory control of the main cause, which I believe is hyperventilation, by keeping the expiratory relief at a low setting and hopefully avoid needing a more expensive machine.

[DoriC]

Flex is just a comfort feature and some people even do better with it turned off.

[LTen]

Is 'flex' the same as increasing/decreasing EPR on a ResMed machine? Most of my events are clear airway and I'm always looking for ways to get that number down. Thanks.

[kcellwood]

Not an expert on the Resmed but based on decription of EPR I would say yes it is the same thing. It is a pressure relief during exhalation. Night three of the change and I have stayed at 3 or below.

[Pugsy]

Is 'flex' the same as increasing/decreasing EPR on a ResMed machine? Most of my events are clear airway and I'm always looking for ways to get that number down. Thanks.

While there is a bit of a reduction variability with the setting choices with the Flex options it isn't nearly as dramatic of a reduction as with EPR on the ResMed machine.
The actual amount of reduction is based on the patient's own forceful breathing...a shallow breathing person wouldn't see much of a reduction even at the highest setting.
http://aflex.respironics.com/

While a small handful of people seem to notice a bit of a correlation with the use of any of the Flex options and their central event count....most people don't.
If someone does for sure have complex sleep apnea where the centrals are directly related to the pressures used...adding one of the FLex options is NOT going to make enough of a reduction in pressure to likely impact centrals that are caused directly by pressures used.

So a setting of 3 EPR which is 3 cm reduction...is totally different from Flex at 3 (where the reduction might be 0.5 to 1.0)

[igdoc]

Hi Pugsy
All respect to you as your knowledge is second to none. However I believe the effect on centrals from reducing the EPR is not due to any pressure change (which is indirectly related to central events) but due to reducing the hyperventilation which I believe is the primary cause of many of the central events by pushing the CO2 below the apnea threshold (high loop gain is also needed). I am in the process of trying to prove this scientifically as at present I only have evidence with a few (rare) complex apnea cases (including myself). However reducing the EPR has successfully reduced the centrals in all of these and has meant that ASV machines have not been required. At present I do not know how useful (if at all) this might be. I would be interested to know your thoughts.

[LTen]

I'm going to join your guinea pig group. Interesting.

[igdoc]

Thanks LTen. We need as much feedback as possible as 'CPAP induced central apnea or Complex Sleep apnea' people who are not already on ASV machines are hard to find. If you are interested in my experiences with this I have posted on FreeCPAPAdvice.com/forum/Sleep apnea help/persistent high AHI - sorted. (I hope it is OK to mention another forum!)