Oxygen pressure
 

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The only way to simulate that would be a vacuum chamber.

The lowest cabin pressure you will see in normal conditions in a commercial aircraft is an equivalent effective cabin altitude of about 8000 ft when the aircraft is at 40,000 ft cruise... This is not common.

You will normally see a cabin altitude of between 5000 and 6900 ft depending on cruising altitude and what equipment you are flying in.

Most people can easily tolerate an equivalent effective cabin altitude of 8000 ft. In general, only people with compromised lung or heart function should worry about going above 5000 ft.

I have found your numbers to be exactly correct. I have an ear condition that is possibly affected by cabin pressure. I bought a pressure gauge to measure pressure in flight. Most of the time, the pressure is taken to about 24-25 in-Hg, or about 7000 ft compared to atmospheric pressure at sea level.

As for simulating the cabin pressure, Denver at 5000 ft. is close as is Salt Lake City. Leave either one and go about 3000 ft up in the mountains and you have it. Park City, Utah, is 7000 ft and a beautiful place to visit. Mexico city is closer to 8000 ft and Toluca (about an hour away) is near 9000 ft.

I hadn't thought about driving to the mountains. :eek:

I have to drive for hours to see anything above 3000 ft... but I know of three vacuum chambers big enough for a human within an hour of me.

I would think you could do it with scuba equipment if you had a tank of air charged with a gas mix with a lower oxygen concentration. Preparing such a mix is definitely something only for the pros, though--our suffocation sensing mechanism is sensitive to excess CO2, not inadequate O2. You get no hint you're breathing unsuitable air.

Not sure what you mean by safe, but plenty of sea level dwellers travel to much higher altitudes and do more than just sit. Many ski areas are above 10,000 feet. Hundreds (maybe thousands) of people a day drive or take the train to the top of Pikes Peak (14,110 feet) and wander around the gift shop like tourists anywhere. Just make sure to drink plenty of water.

And from either of those places, you can easily sample altitudes much higher than 8,000 feet if you want.

It doesn't matter what altitude you exercise at, what matters is what altitude your body is acclimated to. If you live in Denver, you will be far less hypoxic in an aircraft than someone who lives in the midwest.

Also, your lungs don't necessarily get a more strenuous work out at lower pressure levels at higher altitudes. It is simply more difficult for your lungs to diffuse the oxygen to your hemoglobin when the differential pressure between your lungs and the ambient air is low. If your body was acclimated to the lower differential pressure at higher altitudes, you would feel a lot better.

The FAA mandates that passengers have oxygen when the pressure altitude reaches 15,000 ft. (or a pressurized cabin to below said altitude). Pilots and required flight crew however are required to use oxygen at 12,500 ft., or be in a pressurized cabin below this altitude.

Go to the Air Force barometric chambers you referred to. But check with your doctor first. These chambers are also open for public use (primarily General Aviation pilots), but you must call ahead and schedule.

There are really multiple variable here. First one must not make the mistake on confusing barometric pressure with the partial pressure at which O2 (PPO2) is being delivered. For O2 gas exchange in the lungs there must be adequate PPO2 which IIRC is about .05 atm anything lower and the O2 will not diffuse into the blood stream.

For example, breathing 100% O2 at sea level (1 atm) is the same as breathing air (~20% O2) at 40 meters under the water (~5 atm). In both case the PPO2 is 1 atm (100% x 1 atm == 0.20 * 5 atm).

One can go the other way and breath 100% O2 at 8000 meters (~1/3 atm) which would be the same as breathing 30% O2 at sea level.

So if you want to simulate cabin pressure (~2500 m) which about .75 atm. Get a cylinder of gas composed of about 15% O2 and 85% nitrogen and breath that using a full face mask.

Of course remember the mask is not going to be a perfect seal so as said above the only way to get it "exact" would be in a pressure vessel.

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Good info. One question. Is the atmosphere in an aircraft at altitude and .75 atm the same O2 ratio as "normal" air or do they add O2?

It is plain ole air served at a different pressure. The vast majority do not feel the difference - that is because they are sitting down and when they do walk it is at very slow pace. So the reduced PPO2 is not an issue. However, those who have a compromised system (pneumonia, emphysema, etc) though sitting could well have issues and for them on-board O2 at a low flow rate will be needed.

Around here in Oootah this time a year we have what is called the Texas heart attack. A skier comes from sea level, hits the ski slopes at 7k-10k feet, does a few runs, feels weak, shortness of breath, etc. Thinks they are having a heart attack - nope just did not acclimate very well. They get sent down to the valley.

Similarly many sports teams like basketball teams will come to Oootah and stay up in Park City the night before a game to acclimate - even 12 hours is helpful for the body to respond to a change altitude.

That used to happen to me when I still smoked. The worst was Mexico City, Altitude+Smog+my smoking+limited medical facilities. The panic nearly finished me off until it was explained to me that we were at 8000 feet.

The same. They're not going to haul around tanks of O2 without a good reason to--it's quite a fire danger. (Yeah, oxygen doesn't burn. Things burn *VERY* vigorously in pure oxygen, though!)

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