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#1
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I am not a pilot, and as much as my email address sounds like I am a
doctor, I'm not... That said, I thought someone here might be able to help me out - they news reports talk about passing out within seconds at high altitudes. I understand the air is thinner / less O2. But if I go underwater, there's certainly no air there. And I can stay down for a while, holding my breath. How is high altitudes different? I would think you would rasp / fight to breath in but keep functioning as your body uses up the 02 in the blood from your last breath? Not like a sleeping gas in the movies where you just keel over as soon as it hits you? THANKS! |
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#3
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My understanding is that the O2 in the cells and in the blood will actually
go back into the lungs at very low ambient pressures. It doesn't matter whether you breath or hold your breath, the O2 will leave your body. It is something like the bends where gases that will disolve in the body under higher pressures will come out of solution at lower pressures. Mike MU-2 wrote in message oups.com... I am not a pilot, and as much as my email address sounds like I am a doctor, I'm not... That said, I thought someone here might be able to help me out - they news reports talk about passing out within seconds at high altitudes. I understand the air is thinner / less O2. But if I go underwater, there's certainly no air there. And I can stay down for a while, holding my breath. How is high altitudes different? I would think you would rasp / fight to breath in but keep functioning as your body uses up the 02 in the blood from your last breath? Not like a sleeping gas in the movies where you just keel over as soon as it hits you? THANKS! |
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#6
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On 8/15/2005 10:29, Mike Rapoport wrote:
It isn't totally clear from your post but I think you have it wrong. The concentration of O2 is the same at all altitudes. At 18000' for instance the air pressure is half, the concentration of O2 is the same as at sea level so the total amount of O2 is half. Yes, you're right (on both counts) - I had forgotten about this. Mike MU-2 "Mark Hansen" wrote in message ... On 8/15/2005 09:54, wrote: I am not a pilot, and as much as my email address sounds like I am a doctor, I'm not... That said, I thought someone here might be able to help me out - they news reports talk about passing out within seconds at high altitudes. I understand the air is thinner / less O2. But if I go underwater, there's certainly no air there. And I can stay down for a while, holding my breath. How is high altitudes different? I would think you would rasp / fight to breath in but keep functioning as your body uses up the 02 in the blood from your last breath? Not like a sleeping gas in the movies where you just keel over as soon as it hits you? THANKS! There is a big difference between Air and Oxygen. With no Air, you are unable to move your lungs (there is nothing to pull in). With low oxygen, you can still move air, it just don't provide the oxygen necessary to support your life. This is called Hypoxia, and one of the side effects of this is euphoria. What that means, is it causes you to feel like everything is really great, when in fact, you're asphyxiating yourself. Here is a link to an explanation of Hypoxia: http://www.batnet.com/mfwright/hypoxia.html This is the simple answer. Let me know if you would like more details. -- Mark Hansen, PP-ASEL, Instrument Student Sacramento, CA -- Mark Hansen, PP-ASEL, Instrument Student Sacramento, CA |
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#8
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Not quite. Mole fraction of oxygen in the air is the same at all
altitudes, about 21%. Concentration, in the senses of partial pressure and number of molecules in a given volume (such as one breath), goes down with increasing altitude. The partial pressure translates to the fraction of available molecules that are biologically usable; the density of molecules translates to how many there are in the breath. You lose twice with increasing altitude. David Mike Rapoport wrote: It isn't totally clear from your post but I think you have it wrong. The concentration of O2 is the same at all altitudes. At 18000' for instance the air pressure is half, the concentration of O2 is the same as at sea level so the total amount of O2 is half. Mike MU-2 |
#9
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Based on my experience in a USAF altitude chamber, after the chamber has
been pumped up (actually down...it is a vacuum) to 25000 feet and the pressure suddenly dumped as would be the case in a decompression, whatever air you have in your lungs comes out forcefully...no way do you have any control over it. Gotta get that mask on and get it on in a hurry, because time is fleetingly short. In US regulations, the magic altitude is flight level 350 (more or less 35000 feet, depending on ambient atmospheric pressure). The Cypriot plane was reportedly at FL 340, if we can believe the media. Under US rules, above FL 350 both pilots must be at the controls and each must have a quick-donning mask at hand. If one pilot has to leave the cockpit for any reason, the other has to put on and use oxygen until he returns. Lots of unknowns. Bob Gardner Bob Gardner wrote in message oups.com... I am not a pilot, and as much as my email address sounds like I am a doctor, I'm not... That said, I thought someone here might be able to help me out - they news reports talk about passing out within seconds at high altitudes. I understand the air is thinner / less O2. But if I go underwater, there's certainly no air there. And I can stay down for a while, holding my breath. How is high altitudes different? I would think you would rasp / fight to breath in but keep functioning as your body uses up the 02 in the blood from your last breath? Not like a sleeping gas in the movies where you just keel over as soon as it hits you? THANKS! |
#10
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![]() Bob Gardner wrote: Based on my experience in a USAF altitude chamber, after the chamber has been pumped up (actually down...it is a vacuum) to 25000 feet and the pressure suddenly dumped as would be the case in a decompression, whatever air you have in your lungs comes out forcefully...no way do you have any control over it. Gotta get that mask on and get it on in a hurry, because time is fleetingly short. In US regulations, the magic altitude is flight level 350 (more or less 35000 feet, depending on ambient atmospheric pressure). The Cypriot plane was reportedly at FL 340, if we can believe the media. Under US rules, above FL 350 both pilots must be at the controls and each must have a quick-donning mask at hand. If one pilot has to leave the cockpit for any reason, the other has to put on and use oxygen until he returns. It's FL 250 (121.333 I believe). Above 250 one crewmember must be on O2 when the other leaves the flight deck. As to decompression of an aircraft the size of the 737, there is rapid decompression and explosive decompression. It the packs both trip off or a window blows out it results in rapid decompression, which is quite different than an altitude chamber experience. The cabin ascends at perhaps 10,000 feet per minute. But, if there is some type of structural failure resulting in a whole larger than a window, then the cabin can explosively decompress, similar to your experience in the altitude chamber. |
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