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Hypoxia And The Pilot  
User currently offlineAirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1
Posted (10 years 7 months 4 days 13 hours ago) and read 4948 times:

What altitudes can you expect the effects of hypoxia. It's kind of weird because I know that when you fly a jet at altitudes above 35k feet the cabin altitude is above 7K feet and it's fine but when I fly a 172 I'm always nervous flying above 7K feet because I get this mental feeling like I'm going to start to feel the effects of altitude sickness, sometimes I do have effects but I'm wondering if they are just a mental induced thing rather than a physiological thing. It just feels like my body could go on to 10k feet but my mind is not letting me. For those of you who have been inside of those altitude chambers or have been through a hypoxic state can you give me some tips?

6 replies: All unread, jump to last
User currently offlineAirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1
Reply 1, posted (10 years 7 months 4 days 13 hours ago) and read 4945 times:

I mean tips for functioning well at high altitudes with no oxygen?

User currently offlineJspitfire From Canada, joined Feb 2005, 309 posts, RR: 1
Reply 2, posted (10 years 7 months 4 days 13 hours ago) and read 4934 times:

In Canada, the regulation is that you can fly between 10 and 13 thousand feet for less than 30 mins without oxygen. Any longer, and you are required to have it, but only for the crew and 10 percent of your passengers. I don't know what happens if more of your passengers start to suffer from hypoxia....
Above 13,000 ft, you need oxygen for everyone on board, regardless of how long you are up there.


User currently offlineBri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 3
Reply 3, posted (10 years 7 months 4 days 12 hours ago) and read 4931 times:

7,000 MSL is not a high altitude. The pattern altitude at my home airport is 6,800 feet! The terrain rises from there to the practice area, and I have to begin maneuvers so they end 1,500 ft AGL. Most days, the density altitude is above 7,500 on the ground. The cabin pressure on an airliner in cruise is usually equivalent to 8,000 ft MSL. It changes slower than if you rapidly descend from 7,000 to sea level so you barely notice it. I drive to over 10,000 feet all the time. You could do it too, and you'd never even notice. Unless you're flying fighters, there's very little physical exertion required to fly an airplane, so the relative decrease in oxygen with the altitudes you're going to fly out of SoCal is negligible.

That being said, any pilot should be aware of the effects of both hypoxia and carbon monoxide poisoning. From the AIM, 8-1-2.a.2.: "Although a deterioration in night vision occurs at a cabin pressure altitude as low as 5,000 feet, other significant effects of altitude hypoxia usually do not occur in the normal healthy pilot below 12,000 feet." So you can quit worrying about flying at 7,000 feet, unless...

From the AIM, section 8-1-2.a.4.: "The altitude at which significant effects of hypoxia occur can be lowered by a number of factors. Carbon monoxide inhaled in smoking or from exhaust fumes, lowered hemoglobin (anemia), and certain medications can reduce the oxygen-carrying capacity of the blood to the degree that the amount of oxygen provided to body tissues will already be equivalent to the oxygen provided to the tissues when exposed to a cabin pressure altitude of several thousand feet. Small amounts of alcohol and low doses of certain drugs, such as antihistamines, tranquilizers, sedatives and analgesics can, through their depressant action, render the brain much more susceptible to hypoxia." So, don't smoke, don't drink (or be hung over), and don't take any medications before flying (until you know exactly how the medications affect you). The AIM isn't the easiest place to read this stuff; there are lots of other resources available in books and online regarding hypoxia and carbon monoxide poisoning, ear blockage, decompression sickness after scuba diving, and lots of other good things pilots should know.

When I was in the Air Force ROTC years ago, we all got checked out in the high-altitude chamber so if an "incentive ride" in a fighter ever came around, we'd be eligible. Of course, none did, they always went to cadets in the Academy. It was still fun, though. The main thing I remember was the tunnel vision and loss of ability to see colors. They'd crank it up to 14,000 feet and give you a color wheel, and you could pick out maybe 3 or 4 basic colors. As the altitude started coming back down, you'd realize there were maybe 14 other colors on the wheel you couldn't see at altitude! We weren't in there for very long, so the loss of coordination, blue discoloration of lips and fingernails, memory and alertness, and other affects of true high altitude didn't really kick in.

Position and hold
User currently offlineWrenchBender From Canada, joined Feb 2004, 1779 posts, RR: 7
Reply 4, posted (10 years 7 months 4 days 11 hours ago) and read 4903 times:

There is a new theory out there that prolonged exposure to altitudes above 8000 feet without supplemental oxygen may cause mild hypoxia.
The rules have changed for the Canadian military, non pressurized aircraft operating above 8K for longer than 6 hours (I think) must have supplemental Oxygen for the crew. This was due to an incident several years ago. An entire crew was found to be hypoxic on a herc long haul flight.


Silly Pilot, Tricks are for kids.......
User currently offlineBri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 3
Reply 5, posted (10 years 7 months 4 days 11 hours ago) and read 4899 times:

Interesting theory. Of course, 14,000 is above 8,000. What altitude was the particular incident flying? Is there any other information about it available? Having lived in Colorado my whole life, I feel I'm somewhat accustomed to high altitudes, but I've never seen any compelling evidence suggesting that, or suggesting that anyone else isn't.

Position and hold
User currently offlineCaboclo From United States of America, joined Nov 2004, 203 posts, RR: 0
Reply 6, posted (10 years 7 months 4 days 7 hours ago) and read 4884 times:

AirWillie, there are hypoxia seminars complete with altitude chamber available to civilians. I haven't the faintest idea where to find out about such things, but someone here might. My college took the whole flight class to the Little Rock Air Force base for a day long session. It's useful to find your particular symptoms, not everyone is the same. In my case, I found it difficult to do simple math. One of the other guys got very angry, another one got very happy.

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