Hypoxia at 15,500'?

[LittleOne 0]

On my third jump yesterday, we exited at 15,500 AGL, 16,300 MSL. The first pass was at 10,000 to let two tandem groups out. On the second pass, the pilot kept climbing above 13,500, I became concerned about whether we should be doing this. Doesn't the pilot need supplemental oxygen at 14 and passengers need it at 15? Why are we going so high? When is he going to stop climbing? The 2 other jumpers were just high fiving each other, grinning and pointing at their altimeters. I do not know exactly how long we were at altitude.

At 15.5, the 2 way exited before me and I was last. I pulled high at 4,500 (my usual pull altitude) with a few line twists that I worked out, after a loong, uneventful freefall. As I approached the landing area, I saw at about 2,500 that the winds had changed direction. Even though I had plenty of altitude, I could not draw a simple landing pattern and ending up landing slightly crosswind. Luckily, the winds were mild. Furthermore, I flared high, realized it almost as it was happening, and heard a little voice saying "PLF" but failed to assume the position in time. I took a pretty hard hit on my ankle and knee and am sore today but otherwise undamaged.

With plenty of altitude, I was not able to select a simple landing pattern at my home dropzone. I am the first to admit that my canopy skills, even with this many jumps, are not very good. The landing area is tiny and surrounded by trees, a pond and power lines but I am familiar with it. Could this be an effect of hypoxia or is it just another bonehead blunder on my behalf?

[AggieDave 6]

If you were concerned, did you bring it up to your S&TA, the head instructor or the DZO?

If you haven't done that yet, then you skipped step 1 and should do that.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[diverdriver 5]

Do you smoke? Have any other breathing problems? Asthma?

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[PhreeZone 15]

Sounds like the Ranch... its not that small of a landing area, but it can be challenging.

You might want to talk to your S&TA (he posts on here) about your concerns and talk to him about exactly what hypoxia is like and some of its effects on your body. Opening at 4500 should have left you in a high enough O2 environment to clear the cobwebs unless you were having bad effects.

Something thats been recommened to me is to try and schedule a trip to an altitude chamber to see the effects of hypoxia directly on my body. Normally there is a 9-12 month waiting peroid so its not something you can just go and do tommorrow... but everyone I've talked to said its sobering to see how stupid you can be and still think you are fine.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[MarkM 0]

Do you have the link for those? I've been meaning to try out one of them myself before I start to get into high altitude jumps.

[LouDiamond 1]

If you have no major health issues the altitude you exited from poses no threat to you as long as your not at that high of an altitude past your working time. In your case and the siutation you describe it is highly unlikely your resulting performance down low had anything to do with the altitude you exited at. You deployed at 4.5k which would of given you plenty of time under canopy to adjust. Altitude does effect people in different ways but you would of had to of been at or above 12.5 for 15 mins or more to even begin entering the neighborhood of needing O2 and or feeling the effects of hypoxia. I wouldn't rule it out entirely that maybe you became a bit hypoxic but I do doubt that it was enough to cause your subsequent landing problems. It has also been my experience that for some,just going above the altitude they are accustomed to for the first time can be a stressor in of itself and thus cause ones circle of awareness to tighten.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[councilman24 36]

You may very well be hypoxic on a flight you described. But, only one or two breaths at lower altitude will bring you back to normal. The effect is not long lasting because nothing else has bound up the hemoglobin. The effects of hypoxia would have been gone before you opened, let alone before you landed.

An example. I took the flight safety chamber ride to 25,000. There is a work sheet they have you do when your off mask and getting hypoxic. It includes some simple math, I think spelling, and a small, simple line maze at the end. I thought I was doing pretty good but couldn't find a way through the maze for nothing. They had us hang the clip board behind us on the wall. Then we told us to put on our masks and restart the oxygen as we had been trained. One guy couldn't even put his mask on. He sat there grinning until the instructors put his mask on for him. I put my mask on but didn't turn on the oxygen flow. The instructors were telling me to and I was thinking "Okay, I'm going to turn my oxygen on right now" while I was looking at the switch. But my arm never moved. The insturctors had to turn it on. Within one or two breaths I was back to normal. I turned around to look at the maze because I was pissed I couldn't get it. It was immediately obvious there was no way through it. They wanted you to fail so you weren't too self confident.

The chamber ride is informative, but a long day because there substantial classroom instruction. And being in an enclosed tank with 14 other people (all men in my case) with all the gas in their bodies expanding makes for a pretty smelly ride. Luckily your on oxygen most of the time, and hypoxic pretty fast when you take your mask off.

So yes, it was probably just another "bonehead blunder " on your part. You may have had some extra adrenaline going and you may have been worried about being hypoxic. But I doubt that you were.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[crotalus01 0]

heres a hopefully helpful reply from another post...



"§ 91.211 Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry --

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and

(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.

Jumpers don't have to use the O2, it simply must be available. Here is CO, jumps are made all the time from 17,500 MSL and no one uses O2.

As for me and my house, we will serve the LORD...

[tombuch 0]

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Altitude does effect people in different ways but you would of had to of been at or above 12.5 for 15 mins or more to even begin entering the neighborhood of needing O2 and or feeling the effects of hypoxia.

Not true. Hypoxia can occur very quickly, and in fact, mild hypoxia is common at our normal jump altitude of 13,500. I’ve felt it many times, especially while talking to my students when doing tandems at the end of a long weekend.

The concentration of oxygen at 15,000 feet is only about 60 percent of that at sea level, and at 18,000 feet the pressure/concentration of oxygen is reduced to 50 percent of sea level.

There are many elements that will aggravate hypoxia, including simple things like smoking or undiagnosed lung disease. Other common factors that reduce the ability of the blood to carry oxygen include poor nutrition, fatigue, dehydration, or exposure to carbon monoxide. Oxygen demand is increased when we are active, or talking. Reductions in respiration or respiratory effectiveness (generated by stress and unusual breathing patterns) can also cause hypoxia. The longer the exposure to low pressure altitudes, the greater the effect of hypoxia, so jumpers in slow climbing airplanes are more susceptible than those in turbine airplanes.

Mild hypoxia will often manifest as a lightheaded feeling, dizziness, disorientation, tunnel vision, or disassociation from the moment/event. The specific effects vary by individual, but age tends to accelerate the process. I find that I become hyper-aware of the problem and very paranoid about the hypoxia when in a skydiving situation, but when in a chamber I enjoy the experience.

The FAA recommends oxygen for pilots flying above about 8,000 feet at night (the color receptors in our eyes are one of the first organs impacted by hypoxia). Oxygen is required for a pilot flying above 12,500 MSL feet for more than 30 minutes, for all pilots flying at a cabin pressure altitude of 14,000 MSL and greater for all exposure time, and oxygen must be provided to passengers (skydivers too) at all times above 15,000 feet.

If you are in the airplane and begin to feel hypoxic, try to relax. Stop being active…that means stop moving around the cabin and STOP TALKING. Take a couple of deep breaths and hold them for a second or two, then resume normal respiration. If you feel like you are not in control, let other jumpers know and consider remaining in the airplane. Experienced skydivers can often tolerate hypoxia through the first few seconds of freefall, but it can be a real problem for students who are confused by the experience and frightened by the new feeling.

We can reduce hypoxia by staying in good physical shape, remaining well nourished and hydrated through the weekend, getting plenty of sleep, and staying calm while in the airplane. If we are at higher altitudes than normal jump operation we should use oxygen in the airplane.

It’s also important to know that even mild hypoxia can be an especially serious problem for jumpers with heart disease. The BPA reports experienced jumpers often manifest tachycardia (rapid heart rates) of 120-160 bpm, and students can experience tachycardia of greater than 200 bpm. The lack of available oxygen coupled with greater cardiac activity can cause serious problems for jumpers with undiagnosed cardiac conditions.

Mild hypoxia is generally short lived, and will clear up soon after exit. In most cases it just takes a couple of breaths at lower altitudes. It’s very unlikely problems in the landing pattern are caused by hypoxia.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[pilotdave 0]

You didn't mention one of the scarier symptoms of hypoxia... euphoria. That's the one pilots are warned of. If you get dizzy or feel weird, you know you are in trouble and can do something about it. But some people will experience a feeling of well being. When you're flying along up high and the world just seems to be a wonderful place and everything is just so perfect, you might me hypoxic.

Dave

[LouDiamond 1]

Your point is well taken but you failed to acknowledge my first sentence which addresses the health/physiological portion. In his description of the event his rate of ascent and exposure time at that altitude was minimal and he shouldn't of been any where near hypoxic. However, I also realize and stated : "Altitude does effect people in different ways" and so he very well could of been seeing the onset of hypoxia before he left the A/C. Possible but not probable IMO and experience in jumping above 15K more than most people will ever do.

Getting back to the original question, I still don't think his landing difficulties can be attributed to even the mild effects of Hypoxia as he would of had time during the decent and canopy ride to adjust.


As for taking a chamber ride, unless you plan on flying an A/C or doing a lot of high altitude jumping(or your have the cash/time to burn) it really isn't going to benefit the average weekend jumper who doesn't go above 12.5-1300 on a regular basis. Having taken several job related chamber rides to stay HALO certified I can say that you do learn what types of symptoms you as an individual tend to display when hypoxic so it can be informative in that respect for an average joe.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[tombuch 0]

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You didn't mention one of the scarier symptoms of hypoxia... euphoria. That's the one pilots are warned of.

Oh so true.

When I did my first segment of chamber training I was a civilian, but in a class of active Air Force flight crew. There is a point in the chamber when the pressure is reduced and everybody is asked to drop their masks and feel the effects of hypoxia. The trainer (an Air Force captain) quizzes everybody over a headset by asking simple questions. When he got to me he asked how I was feeling, and my answer was “…well, you know what you feel like when you have been doing coke all day and smoke a little hit of grass to take the edge off…” The captain said “Sir, I wouldn’t know, are you alright?” I suppose that was my queue to get back on oxygen. I felt great. All my inhibitions were gone and I was loving life, but I needed that bit of prompting to save myself. After a quick self-applied dose of high pressure oxygen I was fine, knew what I had said, but figured there wasn’t any way to take it back. The captain never mentioned my verbal slip after that. I guess what happens in the chamber, stays in the chamber.

Euphoria is definitely a symptom of hypoxia. For me it is a clear symptom in the chamber, but as I mentioned in my first post, in a skydiving environment happiness is replaced by paranoia. That’s unusual. The trainers I’ve worked with say the symptoms should be the same in the chamber and an actual flight environment, but I can assure them there can be a difference.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[Zenister 0]

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An example. I took the flight safety chamber ride to 25,000. There is a work sheet they have you do when your off mask and getting hypoxic.

i remember that sheet, i still have mine somewhere.. we were supposed to write our name over and over.... pretty easy right, after all its something you've probably done MILLIONS of time...when i looked at mine back on the O2 i realized the last 10 or 15 signatures were nothing but squiggly lines...

15.5?? if your in any kind of reasonable shape the extra altitude is simply something to cheer about... are you still nervous in the plane? do you remember to take full deep breathes to help you relax before and during the dive??

____________________________________
Those who fail to learn from the past are simply Doomed.

[billvon 2,417]

>15.5?? if your in any kind of reasonable shape the extra altitude is
>simply something to cheer about...

At Lost Prairie we were regularly going to 16-17K MSL and I was getting hypoxic at least once a day. It would hit me about 5 seconds out the door and would clear within about 20 seconds (as I descended.) A lot depends on what you're used to - I was used to a 200 foot elevation in San Diego. People from Colorado had no problems at all.

[diverdriver 5]

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I guess what happens in the chamber, stays in the chamber.

LOL... so true. I was filling out the sheet in the chamber and it said to sign my name. So I did. Then, halfway down the sheet it asked how many 3 cent stamps are in a dozen. I answered. Then it said to sign my name. I did. Then it asked what my spouses name was. I left it blank.

When I got out I looked at the sheet. For the question about the stamps I answered 4. Oooops. For my signature I left it blank. And where it asked about my spouses name I signed my own name. oooooops. And the whole time I felt in control. Yep. You don't know how messed up you are until you get out.

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[obelixtim 100]

If you are nervous, there is a tendency to hyperventilate as well.....this can produce similar symptoms of lightheadedness, drowsiness etc etc....mix this up with a lower level of oxygen pressure in the atmosphere....and you could very well be affected quite badly.....

Its a misconception to say there is less oxygen at higher levels...... the lower atmospheric pressure just means that the oxygen is not available to you...which is why supplementary oxygen is carried if you stay above a certain level for a certain time....not usually a problem in a turbine a/c, as long as you don't get caught out by a hold for other air traffic....

Interestingly....in the chamber, the heaviest smokers lasted the longest...possibly their bodies had developed a tolerance for operating with lower oxygen levels.....same as distance runners who do training at altitude...or people who live at high altitudes develop a greater tolerance for living without higher oxygen levels....at lower levels their bodies are "supercharged"......

100% oxygen will also cause you to stop breathing for a while as well...but I'll let some other expert tell you exactly why......

If you ever get a chance to do a chamber trip....take it....you learn lots....and its an interesting way to spend a day.....often not available to civilians these days though....

My computer beat me at chess, It was no match for me at kickboxing....

[The111 0]

Everybody keeps saying you don't know how messed up you are when you get hypoxic.

I could be speaking out of my ass, since I've never done one of the chambers, but on my first jump from 22k, for the first 30 seconds I felt like my motor control SUCKED... I was doing RW and could barely even change heading. I just felt frozen and rubbery at the same time. So if that was hypoxia I was definitely aware of it...

www.WingsuitPhotos.com

[tombuch 0]

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Its a misconception to say there is less oxygen at higher levels...... the lower atmospheric pressure just means that the oxygen is not available to you...which is why supplementary oxygen is carried if you stay above a certain level for a certain time....

Umm, sort of but not really. Let me try explaining.

The atmosphere is 21 percent oxygen. That's true at sea level, and at jump altitudes. The difference is that at higher altitudes the air expands, thus there are fewer oxygen molecules in the same volume of air. Think about it this way: If a given container of air holds 100 oxygen molecules at sea level, and the air expands to fill a container twice as big, the larger container will still hold just 100 oxygen molecules. One half of the container (the same size we started with) will now hold just 50 oxygen molecules. When we jump from 14,000 feet the pressure is reduced by about 40 percent, so the ambient air expands, and the same lung full of "expanded air" holds fewer oxygen molecules than it did at sea level. Those fewer molecules are all available to us, but there are not as many of them. That's sometimes confusing, but it's an important concept to understand.

I’ll try explaining it another way for the conceptually challenged: Imagine you have a small meeting room at a local hotel filled with 200 people, and 21 percent are relative workers, 79 percent are freeflyers. The math tells us that 42 of the jumpers are relative workers, and 158 are freeflyers. Imagine all those jumpers like each other and mingle freely, refusing to congregate in segregated groups. Now let's imagine the hotel manager walks in and decides the room is too crowded, so he pulls back the removable wall doubling the size of the room. The crowd spreads out to fill the larger space, but it is still comprised of the same 200 people, with 21 percent relative workers and 79 percent freeflyers. Now imagine the mean junior manager walks into the room and pulls the removable wall back in place, cutting the crowd in half. Each room still holds 21 percent relative workers and 79 percent freeflyers, but now the total number of relative workers in the original room is just 21, half as many as were in the room before...see, the concentration remains the same, but the actual number available is reduced.

Now I'll take it a step further.. Oxygen and carbon dioxide move across the membranes of the alveoli in the lungs based on pressure differentials. If you go much higher than 18,000 to 24,000 feet there is not enough difference in pressure between the ambient air and blood gas to drive the exchange. That's the point where even 100 percent oxygen begins to loose effectiveness, and the oxygen that is in the air is actually not available to you. In that case the oxygen needs to be delivered under pressure so the gas exchange can occur at the level of the alveoli. In this sort of case, instead of using a nasal cannula, a jumper needs a mask with oxygen delivered at high flow and under pressure. That loss of pressure delivery isn't a critical issue at normal jump altitudes.

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100% oxygen will also cause you to stop breathing for a while as well...but I'll let some other expert tell you exactly why......

Only in rare cases, generally having to do with a long term elevated carbon dioxide level and chronic lung disease.

In normal cases our brain figures out when to breathe based on excess carbon dioxide in the arterial blood. A build up of carbon dioxide triggers respiration. In some people who have elevated carbon dioxide levels over a long period of time (chronic lung disease) the brain switches to a normal back up system called the "hypoxic drive." In these people the brain drives respiration based on low levels of oxygen. For these few people who breathe primarily based on the hypoxic drive, 100 percent oxygen may prevent the level of oxygen in the arterial blood from dropping to the critical threshold, and may depress respiration. It's not a common problem, and should not be a worry for skydivers. Most of us can easily tolerate 100 percent oxygen.

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If you ever get a chance to do a chamber trip....take it....you learn lots....and its an interesting way to spend a day.....often not available to civilians these days though....

Very true.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[Beerlight 0]

Here you go:

http://www.cami.jccbi.gov/aam-400/enroll_okc.htm

Ya know, I teach this stuff about everyday, and all of ya'll have put out some great info/advice.

As for training, when/if anyone calls the ph.# listed in the CAMI link, ask for D.J. Demuth. He's the scheduler and tell him Buck sent ya!! Also, don't get scared, you don't have to travel to Oklahoma for training, the FAA has an agreement with numerous military chamber units scattered around the U.S. Just have at least an FAA Class 3, not be too overweight, no beards, etc....and your set..

Buck Buchanan
Aerospace Physiologist
NASA, Johnson Space Center
Houston, TX

[obelixtim 100]

Yeah....thats what I said....I was just too lazy to explain it in detail....

I knew someone would......

My computer beat me at chess, It was no match for me at kickboxing....

[obelixtim 100]

Yeah, well the reason you won't be aware of hypoxia developing is because it sneaks up on you.....you can be at 18 grand for 10 minutes and not feel much different at all....but go to 26 grand for 2 minutes and the effects get you quickly.....

By the time you are being affected, you are already within the trap, so to speak, and this is where you can get caught out.....because you feel OK.....

An increase in altitude will also lead to a decrease in temperature....and without adequate insulation you can start to get the effects of low temperature....some of the symptoms being similar to the symptoms of hypoxia/hyperventilation...so in effect you can have 2 or 3 different things contributing to your condition......exposure also sneaks up on you with little warning...

The key to this is to be aware of the symptoms and to anticipate them when events conspire to put you within the risk bracket......so watch out for them in others as well.....

Availability of accessible oxygen is the solution....whether on board the aircraft or at lower altitudes.....

My computer beat me at chess, It was no match for me at kickboxing....

[mjosparky 3]

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Here you go:

http://www.cami.jccbi.gov/aam-400/enroll_okc.htm

Ya know, I teach this stuff about everyday, and all of ya'll have put out some great info/advice.

As for training, when/if anyone calls the ph.# listed in the CAMI link, ask for D.J. Demuth. He's the scheduler and tell him Buck sent ya!! Also, don't get scared, you don't have to travel to Oklahoma for training, the FAA has an agreement with numerous military chamber units scattered around the U.S. Just have at least an FAA Class 3, not be too overweight, no beards, etc....and your set..

Buck Buchanan
Aerospace Physiologist
NASA, Johnson Space Center
Houston, TX

You can believe that what Buck doesn't know about going high and what it can do to you can be written on the head of a pin.
I learned more shit then I can understand from a friend of his at Edwards who was working the chamber there.
Thanks Buck,

Sparky

My idea of a fair fight is clubbing baby seals

[dnewcomer 0]

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Its a misconception to say there is less oxygen at higher levels...... the lower atmospheric pressure just means that the oxygen is not available to you...

You are right about the fraction of oxygen in the ambient air (atmosphere) at different altitudes up to 56 miles --- it is about the same: 21%. (Above ~56 miles, the fraction of gases in the atmosphere changes. The relative portions of light gases such as oxygen, helium, and hydrogen increase because of their densities compared to nitrogen.) The oxygen is just as available at higher altitudes, but the hemoglobin molecules in your blood have a tougher time attracting them because there are fewer per unit volume of air.* Presumably this is because our bodies didn't evolve in an environment at 1/2 atmospheres of pressure. Consider how this might compare to creatures that live 25,000' under the ocean at crushing pressures --- equal to hundreds of atmospheres? What would the partial pressure of oxygen be at those depths?

*Even though the fraction of oxygen making up the air you breathe does not change at tropospheric altitudes (below 55,000'), air pressure diminishes as altitude above the surface of the Earth increases, so there are fewer oxygen molecules available per unit of space, including the air in the alveoli of your lungs. To complicate matters, your hemoglobin can change its affinity for oxygen depending upon conditons in the blood such as pH and amount of dissolved CO2. (No kidding.) If you ever had general anesthesia, your anesthesiologist had to deal with this every minute you were asleep. Your body's oxygen carrying system is built to help out automatically in emergency situations to carry adequate amounts of oxygen to the tissues.....such as after serious trauma or even while taking a ride to altitude.

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100% oxygen will also cause you to stop breathing for a while as well...but I'll let some other expert tell you exactly why......
-------------------
Only in rare cases, generally having to do with a long term elevated carbon dioxide level and chronic lung disease.

In normal cases our brain figures out when to breathe based on excess carbon dioxide in the arterial blood. A build up of carbon dioxide triggers respiration. In some people who have elevated carbon dioxide levels over a long period of time (chronic lung disease) the brain switches to a normal back up system called the "hypoxic drive." In these people the brain drives respiration based on low levels of oxygen. For these few people who breathe primarily based on the hypoxic drive, 100 percent oxygen may prevent the level of oxygen in the arterial blood from dropping to the critical threshold, and may depress respiration. It's not a common problem, and should not be a worry for skydivers. Most of us can easily tolerate 100 percent oxygen.

A very good explanation. In normal people, excess CO2 drives their respiration. In individuals with lung disease who are chronic CO2 retainers, low O2 is the driver. Give them excess O2 by mask or nasal cannula and their spontaneous breathing may slow or stop entirely --- nearly ALL of these people are or were smokers, but some medical conditions such as longstanding asthma can cause this problem too.

If you aren't getting enough oxygen for a significant amount of time (several minutes), your brain's intuitive function will suffer. You can't think clearly. You probably won't notice this change early because it is so subtle, and when it becomes more severe, you will eventually lose consciousness. A very dangerous situation.

Bottom line: If you are making a skydive above 14,000' MSL, be aware of these problems. If you have lung disease or are a smoker, you should be very cautious. You can help by not smoking within several hours of going up. Carbon monoxide in tobacco smoke has a high affinity for hemoglobin and blocks the blood's ability to take up oxygen. It would be best to not "smoke and jump" at all. However this should not be a problem when jumping from altitudes up to 14,000' MSL.

All that having been said, consider this. When people first started climbing Mt. Everest (>29,000' MSL), they didn't think it would be possible to reach the summit without supplemental oxygen. Now we know it is possible --- and in fact has been done**. How can that be? It turns out your body adapts to lower atmospheric pressures and low partial pressures of oxygen in the ambient air. But much of that adaptation takes place over an extended period of time.....weeks to months. These changes can be observed in the bodies of people who live in cities at higher elevations such as Denver. Unfortunately your body can't adapt that much on a ride to altitude. But it's still amazing to consider that a human can exert extreme effort (mountain climbing) for extended periods of time at altitudes in excess of 29,000' without supplemental oxygen.

On the other hand, if you went to 29,000' in an unpressurized airplane in 30 minutes or less without supplemental oxygen, you probably wouldn't survive.

Dave
WEB SITE: www.newconthenet.com

**In May, 1978, Reinhold Messner and Peter Habeler were the first individuals ever to reach the summit of Mt. Everest without the use of supplemental oxygen. Messner repeated this feat alone in 1980.

• Quote

[kelpdiver 2]

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Consider how this might compare to creatures that live 25,000' under the ocean at crushing pressures --- equal to hundreds of atmospheres? What would the partial pressure of oxygen be at those depths?

750x.21 = 157.5 atms PPO2. (Rounding to 3 atms/100ft)

We'd certainly need an adaptation with the exposure table for 1.6atm at only 45 minutes.

So how badly can dehydration or limited sleep amplify the problem, and how big a difference is 12.5 versus 15 versus 18?

[kallend 1,635]

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Consider how this might compare to creatures that live 25,000' under the ocean at crushing pressures --- equal to hundreds of atmospheres? What would the partial pressure of oxygen be at those depths?

750x.21 = 157.5 atms PPO2. (Rounding to 3 atms/100ft)

We'd certainly need an adaptation with the exposure table for 1.6atm at only 45 minutes.

So how badly can dehydration or limited sleep amplify the problem, and how big a difference is 12.5 versus 15 versus 18?

Are you suggesting that the actual oxygen content of the ocean depends on depth? (as opposed to the theoretical solubility at that depth)

...

The only sure way to survive a canopy collision is not to have one.