Altitude question

Fenway · Post by **Fenway** » Tue May 24, 2005 6:06 pm

Just wondering how effective the auto altitude adjustment works, I will be travelling to Colorado in a few weeks, staying at my brothers house for a week at just below 10,000 feet. The first few days there it can be difficult to breathe as it is, I can imagine it may be more difficult with a CPAP strapped on at night. I do use a REMstar pro2 c-flex machine with a ramp feature, but my main concern is if the auto-altitude adjustment can compensate for that kind of altitude. Anyone have experience with this?

Keep on Sleepin' On!
Fenway Steve

glassgal · Post by **glassgal** » Tue May 24, 2005 8:42 pm

Hi Fenway,

Our family has a summer cabin in the Sierra's of California -- at almost 9,000 feet. I asked about it on the straight CPAP that I had first (a ResMed S7 Lightweight) and was told that it could be set up to 7,500 feet. The RT didn't seem to know what to do for higher altitudes.

I now have a PB420E, which says that it works from 0-7,800 feet. The information for my unit was in the technical information in the patient manual. I am not familiar with the machine that you have, but you may find the info in the manual. The other place that you could check is on CPAP.COM's website -- they usually talk about the altitude compensation for each of the machines that they sell -- just look yours up.

I also intend to discuss this with my sleep doc in June when I see him -- you might want to check with your doc too. I don't think that we will get into our cabin until after July 4th because of the heavy snowfall in the Sierra this year. Mammoth Mountain is open until July 4th for skiing! They have 12-14' base now -- our poor cabin is still buried I guess.

I hope that this helps!

Janelle · Post by **Janelle** » Thu May 26, 2005 7:06 pm

Most self-adjusting CPAPs will not adjust to pressure over 8000 feet. Plain and simple. I don't know if this means that what they adjust to over that is no adjustment at all or what it would be if you were at 8000. I spent 4 days in Colorado at 7800 and my machine adjusted fine, although I noticed the numbers overall were a bit higher than usual.

twistedcherokee · Post by **twistedcherokee** » Thu May 26, 2005 10:44 pm

I live in Colorado Springs area and my unit doesn't have the auto altitude. Instead of 7 cfm it is set at 8 to do the 7. So you will probably only be off 2 cfm. My literature that came with my machine has a conversion chart. It goes to 16000 feet. So if you give me your altitude now I can tell you what it should be at at 10000 ft. Then you can compare and see if you need to adjust it.

Toby

BuffaloAl · Post by **BuffaloAl** » Fri May 27, 2005 7:17 pm

Twisted,

Can you list the conversion chart here? I am also traveling "uphill" this summer to Denver.

I believe that the pressure gradient is approximately 20% for each 5000 feet. But I have not been able to find a conversion chart, to see if that is accurate.

twistedcherokee · Post by **twistedcherokee** » Fri May 27, 2005 8:12 pm

I will try to post it in a few hours.

Toby

twistedcherokee · Post by **twistedcherokee** » Fri May 27, 2005 11:54 pm

I have tried to get this conversion on to this reply but unable. Any help would be appreciated. I have tried to scan it to Word, Acrobat Reader, Notepad, Paintshop Pro,Dell Image.

Toby[/quote]

BuffaloAl · Post by **BuffaloAl** » Sat May 28, 2005 7:58 am

I don't know how to post it either. The one you scanned to MS Word, would you email it to me at brooksonehundred@yahoo.com?
Thanks

ozij · Post by **ozij** » Sat May 28, 2005 9:27 am

BuffaloAl,
I'm not a technical person - so this might be complete nonsense.
Please find out if the conversion chart you're getting isn't specific for that machine. I do know that different machines create and measure the pressure with different technologies, and I wouldn't be surprised if the correction for different outside air pressure would depend on that technology.

Try to contact tech support for the machine you have, and see if they can help you too.

O.

BuffaloAl · Post by **BuffaloAl** » Sat May 28, 2005 12:52 pm

Hi Ozij,

Where in Israel do yo live? That's one place I have never been that I would LOVE to go to.

Two different types of pressure we're working with here. One is the pressure produced by the machine to keep your airway open. The other is the extant or environmental air pressure. At sea level, atmospheric air pressure is 14.7 pounds per square inch. Although you can go slighhtly below sea level. the Dead Sea is, what, maybe 300 feet below sea level? There are many places where you can live that are 5-10 thousand feet above sea level. Up there the air is " thinner".

Ordinary things like cooking are changed. Water which boils at 212F at sea level, boils at 203F at 5280ft. Although the water is boiling it's not hot enough to cook 8 minute pasta in 8 minutes. A 400 F oven in New York, at sea level, is not the same thing as a 400F oven in a high altitude city like Denver because there is less air in the oven to transfer the heat to your pizza.

The chemistry behind this change is available here
http://www.clt.astate.edu/wburns/

My cpap is too old to have an auto altitude adjust.

People who live at high altitude are familiar with this

BuffaloAl · Post by **BuffaloAl** » Sat May 28, 2005 2:22 pm

Fenway,

Are you at the game? 14-0, I am lovin' it!

ozij · Post by **ozij** » Sat May 28, 2005 3:10 pm

People who live at high altitude are familiar with this

...actually, so am I.

What I am not familiar with is the way CPAPs compensate for thinner air. You imply that the pressure number is standard, and therefore, a compensated 13 on one pressure producing will be the equivalent of a compensated 13 on another kind of pressure producing mechanism.

O.

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): Altitude

BuffaloAl · Post by **BuffaloAl** » Sat May 28, 2005 4:42 pm

Yes it should be compensated for exactly the same on any machine. If your pressure at your current altitude is 13, and then you stayed in a place with an altitude 5000 ft higher, any machine should be adjusted for the "thinner" air. I think the way to compensate for the altitude would be to increase the pressure on the machine, because less air flows through at a pressure of 13 at the higher altitude. The pressure gradient should be about 15% for each 5000 ft. But the machines do not, as far as I know, set for non-integers. Meaning if you have a pressure setting of 10, I don't think you can set it for 11.5. Which is why I said the gradient setting should be 20% or 12. A little higher is better, safer, than a little lower.

BigHeart · Post by **BigHeart** » Sat May 28, 2005 9:26 pm

I find this all very interesting, but I'm still quite confused. i think the manual for my Bi-PAP said it would automatically adjust up to 6000 feet, but the hospital where i was titrated was at 7500 feet and I live at 6500 feet. I'm currently on vacation at about 1000 feet and eventually plan to move to around 1000 feet. So will my Bi-PAP automatically adjust by lowering my pressure when I move off the hill? I was titrated at 16/12, so when I'm at a lower altitude will my Bi-PAP still show 16/12 but actually deliver a lower pressure than it says? Or is it delivering a higher pressure than 16/12 when I'm at home at 6500 feet? When I move, I hope to find a doctor who will prescribe an auto-PAP for me as I can't stand the thought of doing another sleep test, and it seems like with an auto-PAP altitude adjustments would be unnecessary.

ozij · Post by **ozij** » Sat May 28, 2005 9:51 pm

Will - thanks for making that clear.
By the way, the PB420e, which I too use, can be set on integer differences - I actually have it on 4.5 - 7.5 right now.

Bigheart - that's a great way of putting the question. I'm very curious what the answer is.
O.

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