AHI elevated at altitude?

JPZeller · Post by **JPZeller** » Sun Jun 17, 2007 11:12 pm

I've been on CPAP therapy for two years now (10 cm H2O, with a Respironics Pro, now M Series) and have enjoyed relatively low AHI numbers (average less than 4).

Just got back from a four-night vacation to Lake Tahoe (6300 ft. elevation) and am SHOCKED at my AHI numbers for those four nights: 24.1 (OA 20.2), 10.9 (6.3), 18.5 (11.9), and 29.9 (26.1).

It is my understanding that the machine automatically compensates for atmospheric pressure changes, so this is very surprising to me.

Prior to CPAP, I recall having what I thought of as altitude sickness during a vacation to Santa Fe, NM (I live in Chicago).

Can anyone offer an explanation? Have others had this experience?

And, oh yeah - I felt lousy the entire trip.

Any insight will be appreciated.

Thanks.

Jim

blarg · Post by **blarg** » Mon Jun 18, 2007 4:19 am

Could be that altitude caused it, but to me it's more likely that there were other factors at play. Excessive congestion? Drier air, therefore mouth breathing? There are lots of variables here. Were you leakier than normal?

Refugee · Post by **Refugee** » Mon Jun 18, 2007 7:28 am

I live in Denver but travel constantly for work. I use a M series auto at home, but the one I take with me on the road is the stand M series CPAP that the DME gave me. My auto has the auto altitude adjust, but the regular cpap has to be manually set.

I don't get data from the nights I travel but I don't notice a difference in how I feel between at home at high altitude or on the road a sea level. The main difference is that at home I use the HH at 4 were as on the road I only use it at 1.

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): CPAP, DME, Altitude, auto, Travel

BrianRT · Post by **BrianRT** » Mon Jun 18, 2007 11:16 am

If I'm thinking right (and sometimes that's a big IF) the Pro has to be manually set for altitude. On the M, it's the screen with the little mountain peaks. I believe level 1 is for 0-2000 ft, level 2 is 4000-6000 and 3 is above 6000. You can change this right from the screen without getting into the clinical menu.

Each bump increases your output pressure by 1 cmH20.

JPZeller · Post by **JPZeller** » Mon Jun 18, 2007 11:30 am

Thanks for the replies so far - will check my numbers for the first couple of days this week.

No congestion, no mouth breathing of which I am aware.

As for auto altitude adjustment, CPAP.com says my machine has it:

https://www.cpap.com/productpage-advanced.php?PNum=2170

Goofproof · Post by **Goofproof** » Mon Jun 18, 2007 12:55 pm

BrianRT wrote:If I'm thinking right (and sometimes that's a big IF) the Pro has to be manually set for altitude. On the M, it's the screen with the little mountain peaks. I believe level 1 is for 0-2000 ft, level 2 is 4000-6000 and 3 is above 6000. You can change this right from the screen without getting into the clinical menu.

Each bump increases your output pressure by 1 cmH20.

The "M"agic Pro, is auto adjust, the Plus model and lower are manuel. Jim

Odd's are the numbers got higher because you changed what you normally do. Stress, overdoing, eating different, maybe a few drink-E- poos, or you didn't set up your equiptment in the same way.

blarg · Post by **blarg** » Mon Jun 18, 2007 2:42 pm

If you feel inclined to post your reports from those nights then perhaps the gurus here will come up with something that can help you to avoid having that happen in the future. Traveling is hard enough on a body without having AHIs of 20 at night.

JPZeller · Post by **JPZeller** » Sun Jun 24, 2007 10:29 am

Thanks for the replies so far.

By the way, there was nothing really different going on during the trip, other than the altitude (sadly, not even extra drink-e-poos, as I didn't feel well enough to indulge).

Just checked the numbers for the last week back here at home, and sure enough, the numbers are way better (average AHI 4.2 (range 1.2 to 9.3), OA 2.9).

The leak numbers for the two time periods were about the same - 45 at altitude, 48 at home. No "large leak" in either time period.

Sure seems to me like the altitude was the culprit.

rhowald · Post by **rhowald** » Sun Jun 24, 2007 9:14 pm

I am no doctor or scientist, but I think it makes sense...

The higher altitude the air pressure is lower and therefore the machine would need to work harder to press the smae pressure into your airway to keep it open.

If you have a machine that needs to be manually adjusted and you failed to do this their wouldn't be enough air pressure pushing into your airway to splint it open, hence the higher than usual AHI.

Or I could be talking out my backside... Anyone? Anyone? hehehehe

Rob

split_city · Post by **split_city** » Mon Jun 25, 2007 5:51 am

There are studies which have shown that OSA severity can increase in some people when they travel to higher altitudes. Generally speaking, this is the result of changes in oxygen levels, resulting in ventilatory instability. Ventilatory instability is another potential cause of OSA. It revolves around an engineering term known as 'loop gain.' Basically it relates to what your body does i.e. compensatory output, for a given disturbance i.e. low oxygen. Patients with an unstable ventilatory control system tend to overcompensate for a given disturbance. These patients have a high loop gain. Patients who don't tend to respond to a disturbance have a low loop gain. There have been a number of studies testing loop gain in OSA patients to see if it's different compared to non-OSA patients.

JPZeller · Post by **JPZeller** » Mon Jun 25, 2007 6:49 am

<<If you have a machine that needs to be manually adjusted and you failed to do this their wouldn't be enough air pressure pushing into your airway to splint it open, hence the higher than usual AHI.>>

Thanks. My machine supposedly automatically compensates for altitude, though.

Something tells me this feature isn't activated, or something.

Wulfman... · Post by **Wulfman...** » Mon Jun 25, 2007 1:41 pm

JP,

Good thing you got out of there when you did. There's a forest fire out there now that's consumed more than 200 buildings so far.

If you were still there, you'd be suckin' in smoke.

Den

JPZeller · Post by **JPZeller** » Mon Jun 25, 2007 1:43 pm

Thanks, Wulfman, but we were at the north end of the lake (although the air is thin enough I wouldn't be surprised if the smoke makes it up north).

coldnose · Post by **coldnose** » Mon Jun 25, 2007 8:30 pm

I'm of the opinion that the RemStar M Series does not always change correctly for altitude.

Several weeks ago I travelled from Texas to Tennessee and all went well, my M Series worked as advertised. Upon my return home the first night when I turned on my machine I thought I was caught in a tornado. I had to turn on the ramp function, which I haven't used in months. This repeated the second and third nights. I took my machine to my DME and they checked it's pressure. Everything checked good (I watched as they checked it).

My RT guessed that the airplane ride may have had something to do with it. In any case the machine has worked perfectly since, just as it had before the trip.

This is quite strange, I've travelled with this machine several times and never had any problems. If it happens again on my next trip, I'll have my DME replace it.

Sleep Well,

---gary