Hyperventilation

[justMongo]

The statement was made in this thread:
http://www.apneaboard.com/forums/Thread-...ral-apneas

That Central Apnea (CA) occurred more frequently in BiPAP vs CPAP due to hyperventilation (HV). Now, I assume HV blows off more CO2 from the blood and reduces the brain's central respiratory drive.

I ask myself, why CPAP would have less tendency to create HV and ergo CA --- I conclude that exhalation at CPAP pressure, where IPAP=EPAP reduces the amount of expelled breath, lessening CO2 loss from the blood (as compared to BiPAP where IPAP>EPAP); ergo, lessening HV and therefore CA.

Do I understand correctly?

[igdoc]

Hi Mongo,
You are spot on with your assessment. I am one of the small percentage who have complex sleep apnea or CPAP induced central apnea with an AHI of around 30 when using APAP with exhalation relief. If I turn off the exhalation relief and thereby reduce the exhalation and hyperventilation, my AHI drops to around 7 and is often below 5. This has avoided me needing an ASV machine which in England I would probably have to pay for myself.

This may be a bit controversial but my belief is that CFLEX/AFLEX/EPR whilst definitely increasing the number who can tolerate CPAP has also slightly increased the incidence of hyperventilation induced central events. There is now a small collection of people (from various forums) who have definitely benefited by reducing the exhalation relief when they have abnormally high numbers of central events.

Best wishes, Ian

[Lukie]

This is very interesting. While my AHI is generally<0.5 I do notice that the few apneas I do have are centrals or hyponeas.
I keep my EPR at 2.
Before CPAP I was really desaturating quite a bit even though my apnea was considered mild. I'm wondering if I should lower my EPR to 1 or even 0. Hyperventilation has been a plus for me I guess even with the few centrals because I don't desaturate as much.

[justMongo]

This is very interesting. While my AHI is generally<0.5 I do notice that the few apneas I do have are centrals or hyponeas.
I keep my EPR at 2.
Before CPAP I was really desaturating quite a bit even though my apnea was considered mild. I'm wondering if I should lower my EPR to 1 or even 0. Hyperventilation has been a plus for me I guess even with the few centrals because I don't desaturate as much.

Lukie: Forgive the question. Are you centrally obese? i.e. -- do you carry excess weight in the abdomen? Those, like me, who carry weight in the abdomen often hypo-ventilate; especially while sitting or sleeping on the back. This is because the diaphragm must drop for inspiration. This causes desaturation. xPAP overcomes this extra effort to breath.

There was a non-medical term for people like that:
Pickwickian Syndrome -- named for a Dickens' character in Oliver Twist. That term has is fallen out of common use.

http://en.wikipedia.org/wiki/Pickwickian_syndrome

[igdoc]

Hi Lukie,
It is normal to have a few sleeping central events and up to 5 an hour is regarded as OK. The commonest central events happen in the transition between being awake and asleep when the body slightly resets the CO2 level and these are normal. When awake there are also events registered by sighing or even when we turn over in bed.

Anyway there is probably no need to be concerned unless the central events are keeping your AHI above 5. Your very low AHI is great and, if you are comfortable, I would not change a thing.

Ian

[Lukie]

No, I don't plan to change a thing except maybe experiment with a few more masks. I collect masks like some women collect shoes.
To answer Mongo's question, I am a bit obese. I lost about 40 lbs last summer but have put most of it back this cruel
winter. As soon as my supply of whey protein comes in I plan to start my spring/ summer routine to get back down again.
But yes, anything I gain goes on to the central part of me. I don't desaturate in the day time but I do at night and the CPAP has helped that tremendously. I had a second sleep study and I have stopped desaturating with CPAP therapy. That being said my O2 sats are 90-98 for the night so I am not a candidate for supplemental O2. I exercise aerobically for an hour every day at a gym and that helps a lot too.

[Lukie]

[attachment=699] Just seeing if I could post a screenshot of a month's summary. My daily AHI seems to be okay.

[justMongo]

Just seeing if I could post a screenshot of a month's summary. My daily AHI seems to be okay.

Most of us strive for an AHI report that good.

Do you have a recording oximeter? I recently got one from one of the suppliers on the list. I can see my desats on its reports. A useful tool. Too bad it's not an integral part of every xPAP machine.

Keep up what you're doing, sounds like you are doing well.

[SnuffySleeper]

Just seeing if I could post a screenshot of a month's summary. My daily AHI seems to be okay.

Man, those are great AHI numbers. Isn't technically anything under 5 not Sleep Apnea. So with those numbers with Cpap you actually don't have Sleep Apnea anymore!

[Lukie]

Well I do feel much better. I don't get those middle of the night racing heart and short of breath episodes. I still wake up a lot but at least I don't desaturate as much.