ResMed S9 & 14000 ft. altitude

[zonk]

Posted earlier this thread which did mention that:

Altitude can make the loss of oxygen that occurs with sleep apnea worse
http://www.apneaboard.com/forums/Thread-...a-patients

[Netskier]

I didn't provide a link because I wasn't sure if the site was commercial or not. I looked at the site better today and it is the forum from the American Sleep Apnea Association. A simple Google search on "CPAP at high altitude" gave me the link. I don't post information that is incorrect or if I am uncomfortable with their statements.

(I had the link to the thread here but this forum software changed it to be ***. Do a Google search and it should be fairly high up the result list)

I posted a question several months ago about using a CPAP at high altitudes, and I finally have some information to share. A little background: I use a CPAP and live in Denver, CO (the mile high city) and the manual for my CPAP says that on the highest altitude setting the machine is good for 7500 feet. I'm traveling to Peru and Bolivia in April and will be at altitudes ranging from 8500 feet to 13000 feet.

I called the Lung Line at National Jewish Hospital (http://www.nationaljewish.org). National Jewish is the #1 respiratory hospital in the US, and I'm fortunate that it's located here in Denver. Lung Line is at 800-222-LUNG, a free service where registered nurses can answer questions about respiratory issues from 8 am to 4:30 pm Mountain Time (2 hours earlier than Eastern time). I was referred to another number and after a couple of weeks, someone returned my call.

An adjustment in pressure is called for when using a CPAP high altitudes, and I'll be going in to see someone to learn about how to make those adjustments in the near future. Specifically, an increase in pressure is required. The woman I spoke with was able to calculate what my pressure would need to be at three specific altitudes where I'll be spending nights. The adjustments needed aren't huge. My normal pressure is 6 (cm h2o), and the highest the pressure will need to be - for 13,000 feet - is 7.5.

I hope this information is helpful...

Further down the posts are some links that should be valid enough.

http://chestjournal.chestpubs.org/conten...7.abstract - the short version
http://chestjournal.chestpubs.org/conten...7.full.pdf - the full version

Of particular interest to those of us who do not understand journal articles is page 5 with the Discussion and Conclusion.

Paula,

The article you cited does not say that one must increase the pressure if your machine autoadjusts for altitude. The article says that you must increase for altitude unless your machine does so automatically.

And, acc stated that the machine being used for the trip is a Resmed S9 Autoset which does autoadjust for altitude.

You cited http://chestjournal.chestpubs.org/conten...7.abstract , the conclusion of which states:

"Conclusions: Altitude significantly alters delivered pressure according to predictions made by the fan laws, unless a unit has pressure-compensating features. Clinicians should consider this factor when CPAP is prescribed for patients who live or travel to places located at significantly higher or lower elevations than the titration site."

I boldfaced parts for emphasis.

You cited the full paper http://chestjournal.chestpubs.org/conten...7.full.pdf
which states: "Conclusions.
The delivered CPAP of noncompensating devices is significantly affected by changes in altitude. Pressure sensor-equiped devices maintained delivered pressure throughout the altitudes simulated in the present study."

I hope this helps.

P.S. I heard someone on Sunday report that the Rand Corporation did a study that found that Physicians diagnoses are correct 55% of the time, and wrong 45% of the time. Thus, they are only slightly better than chance. Given this, I conclude that we should be very skeptical of their opinions, and should take personal responsibility for our own health whenever we can.

I think the nurse on the phone was wrong.

P.S. 2. The study was published 19 yrs ago, so the work was done at least 20 yrs ago, so it is not current.

P.S. 3. I am sticking with my original analysis. I think that altitude may lessen obstructive apnea provided that the machine really delivers the selected pressures. This is because the proportion of total air pressure being delivered to the airway from the PAP device increases as altitude increases, since the external ambient air pressure is decreasing, and will go to zero if you go into space. So as you go up, it is as if your neck is being sucked on from the outside, so less compression from the outside, and finally expansion to the outside. Plus, on the inside the relative pressure is increasing, relative to the outside, so more expansion from the inside of your airway.

I think I read that astronauts will explode from their internal body pressures if their pressurized space suits lose their pressures. Therefore airways should expand as we move toward space without wearing pressurized space suits (and hold our breath as we do this).

[zonk]

So what would happen if you bump S9 AutoSet maximum pressure by 2 or 3 cm/H2o?
Does it go there willy-nilly or adjust the pressure as required
and if it adjust as required than the maximum pressure adjustment is neither here nor there.

[greatunclebill]

So what would happen if you bump S9 AutoSet maximum pressure by 2 or 3 cm/H2o?
Does it go there willy-nilly or adjust the pressure as required
and if it adjust as required than the maximum pressure adjustment is neither here nor there.

that's what i'm thinking. possibly much ado about nothing when using an automatic machine.

[JumpStart]

In what seemed to me as a challenge to prior posters,

I recommend that you take personal responsibility for your own health, and not depend too heavily on secondhand opinions.

And later

P.S. I heard someone on Sunday report that the Rand Corporation [someone else] did a study that found that Physicians diagnoses are correct 55% of the time, and wrong 45% of the time. Thus, they are only slightly better than chance. Given this, I conclude that we should be very skeptical of their opinions....

Then, on this hearsay, it seems he concludes that since doctors are only slightly better than chance in their diagnosis, we must largely rely on ourselves. Wow. Makes you wonder why doctors waste time in medical school, internships, residencies, etc. if the best they can do is about 50-50, doesn't it? Makes anyone seeking their opinion, or relying on it, seem rather dumb, right?

I don't point out these statements to attack Netskier, who has clearly expressed a well-thought-out opinion, but to let some air :grin: into this discussion, and suggest that many of us with strongly felt opinions sometimes fall prey to the same generalizations that we, in seeking to make our own points paramount, sometimes attribute to others.

On a related (to the subject) issue: Most of us recognize that OSA generally results in lowered O2, and increased CO2. And that the lowered O2 (desaturization) creates significant damage to affected organs. O2 is unquestionably reduced proportionally to altitude. Were it not so, pilots would have no need for supplement oxygen when flying at higher altitudes to maintain their health and mental alertness. An air flow created by your CPAP at sea level, with no increase in pressure, will absolutely NOT have the same O2 content of an equal flow at high altitude. In fact, it will decrease as altitude increases. Thus ONE answer may be that supplemental oxygen is the best countermeasure to the reduced ambient pressure. And that is without getting into the issue of partial pressures or laws relating thereto, which is another realm altogether.

[PaulaO2]

I give up.

What started as a helpful request to a problem has bloomed into what feels like an attack on me personally vs helping the person with the problem.

Carry on with your high tech, high brow discussion that is over my head but hopefully not over the head of the original poster who may or may not ever figure out what to do with the answers here.

I stand by what I originally said. A slight raise in pressure on his autoset would probably be a good idea. If his body does not need it, it won't change. If his body needs it, then he will be getting a good rest while on a vacation in a wonderful place.

[zonk]

Bon voyage and happy CPAPing in Tibet
Look out for Richard Gere and bring us some spiritual blessing from his Holiness Dalai Lama

[acc]

Thanks for all the input. The doctor's office called today with the solution of taking a second CPAP machine to use the four days we are in Tibet as the didn't want me adjusting the pressure on my machine. However, I have the information on how to adjust the pressure and could do so myself. I can't believe how overly protective they are about the "pressure information". But that's another issue. I'll let you know what happens after our return later this summer.

[pssnn]

This was a fascinating discussion. I worked at a medical device company in the past where we had to do packaging studies related to packaging performance during air shipping. This involved testing for outer packing leaks by placing the packaged devices in various levels of vacuum to simulate various altitudes since the cargo compartments may not be pressurized. One thing to note is that the outer sealed packaging did swell up like a balloon. I think it would be a simple study for CPAP manufacturers to extend the auto altitude adjustment testing past 8500 ft altitude however if they make any kind claim they would have to fully validate that claim which would be expensive. I wonder why they stopped the original study at 8500 feet?

[Netskier]

So what would happen if you bump S9 AutoSet maximum pressure by 2 or 3 cm/H2o?

Does it go there willy-nilly or adjust the pressure as required
and if it adjust as required than the maximum pressure adjustment is neither here nor there.

It goes there as required, just as down here, and it leaks more at all high altitudes. But no one has presented evidence that the max pressure should be increased, and I have argued that even lower max pressures might suffice. I would just leave it as is, and let the autoset algorithm do its work.