High altitude effect on your physiology

[nddons]

For those non-pressurized singles and twins that fly in the high teens and lower flight levels, what is the physiological effect on the body (assume adequate oxygen use)?

I feel it in my ears when airliners adjust their pressurization, but the highest I've flown myself in a 182 was 9,500 ft. I've always been curious as to whether there is any discomfort in flying those turbocharged but non-pressurized aircraft.

 

[dennyleeb]

I rarely fly below 13k. No effects at all.

 

[Henning]

Bone and brain necrosis...

 

[Everskyward]

I used to fly in the lower flight levels in turbocharged but unpressurized aircraft quite often. I can't say that I noticed much of anything related to the altitude although I wasn't really fond of sucking O2 all day and wondering if the heater was going to kick off. I'm glad I don't do that any more.

 

[brcase]

I assume you are trying to ask how would you recognize the effects of hypoxia.

Everyone reacts a bit different, Many report a headache. I notice my vision tends to narrow. The same effect I get when I drink to much. I also just don't feel very well.

However you probably will think you are just fine. If you get a chance take an altitude chamber ride.

From the training they did in the chamber, and also my personal experience in the chamber I find that your mind will tend to stop and just begin repeating the same mental processing. You won't even know you are doing this.

The example they showed in the chamber was they had a person draw a card from a deck, read the card, turn the card around and show it to the group and tell the group what the card is. After a few cards, it didn't matter what the card was he would tell the group it was the 2 of clubs. Which was about the 5th card he had showed the group.

Be careful up there

Brian
CFIIG/ASEL

 

[Everskyward]

I assume you are trying to ask how would you recognize the effects of hypoxia.

I thought the OP was asking about other effects of flying at high altitude since he wrote, "assuming adequate oxygen use".

Maybe you wouldn't want to eat a meal of refried beans before the flight...

 

[flyingcheesehead]

For those non-pressurized singles and twins that fly in the high teens and lower flight levels, what is the physiological effect on the body (assume adequate oxygen use)?

I feel it in my ears when airliners adjust their pressurization, but the highest I've flown myself in a 182 was 9,500 ft. I've always been curious as to whether there is any discomfort in flying those turbocharged but non-pressurized aircraft.

I've had the 182 up to 17,500 while I was on O2. Didn't notice anything unusual at all.

I would imagine that if you have a cold, you could get an ear block bad enough to pop an eardrum, and if you were a bit gassy that day (see the comment about beans) it could get bad, though.

 

[bbchien]

This was the topic of my "teach me a ten minute topic" on my CFI oral. The examiner had Zero clue I was an AME

"(1) You dehydrate like crazy at altitude. The air has Zero moisture at 17,000. It's about 300 ml per hour.
(2) As a result cardiac output goes down so the blood delivery train discharges at lower residual partial pressures as you have to unload the remaining blood more thorougly to get enough.
(3) The brain shuts down frontal flow (judegment areas) to maintian function, so HYDRATE LIKE CRAZY. When I did PSP-->DPA isn the 1993 AC Spruce, after 7:50 I got out, had two whole Diet Cokes and still didn't pee. I was totally dry, and had almost made some stupid mistakes (like descending into a barrel after I had a Vac failure).

(4) Gas effects- there is always some wisenheimer who eats beans the night before the chamber ride. BTDT twice and it's not pretty. It uncovers bad dental abscesses you weren't aware you had. Sinus block if bad enough can lead to a brain blood clot (Cavernous Sinus Thrombosis) or compromise of an eye (the bone punches into the nerve or muscle).

(5) If you push it (I once did) above 18,000 you will be hypoxic on cannulas. You need an occlusive mask. Don't thy this without a built in mic; when you move the mask to talk, you get hypoxic before the end of the sentence. BTW, you won't have enough molecules to say more than twelve words in a row. The air it THIN up there. Get the one with the Mic INSIDE the mask.
(6) At 24,000 you need an occlusive face sealing affair as there just aren't enough molecules even if EVERY ONE is an oxygen molecule.
(7) At 27,000 you need a slight pressure mask; see 6 for reason.
(8) Airline pull downs at 10,000 isn't to keep you sane. When they lose pressure at 37,000, it's to keep you dumb stupid but alive until they can get to 10,000.
(9) Bends. If you have a screamer Turbo Single or T37 you can get to altitude fast enough to get bent even if you haven't been diving. It's happened.

Oh, and BTW, inspector: When you are planning to fly a GA light single to 18,000 it's probably because your mission is to >75% of the capability of your aircraft. So now you have all the weather, ice, and fuel considerations and might be very dumb. Brief The PLAN AND FLY the plan, or abort. No other choices."

"Um....oh I see. We'll let's move along to another topic......"

 

[nddons]

Wow! That's a lot more than "your ears might hurt", but thanks Dr. Bruce!

 

[ajstoner21]

This was the topic of my "teach me a ten minute topic" on my CFI oral. The examiner had Zero clue I was an AME

"(1) You dehydrate like crazy at altitude. The air has Zero moisture at 17,000. It's about 300 ml per hour.
(2) As a result cardiac output goes down so the blood delivery train discharges at lower residual partial pressures as you have to unload the remaining blood more thorougly to get enough.
(3) The brain shuts down frontal flow (judegment areas) to maintian function, so HYDRATE LIKE CRAZY. When I did PSP-->DPA isn the 1993 AC Spruce, after 7:50 I got out, had two whole Diet Cokes and still didn't pee. I was totally dry, and had almost made some stupid mistakes (like descending into a barrel after I had a Vac failure).

(4) Gas effects- there is always some wisenheimer who eats beans the night before the chamber ride. BTDT twice and it's not pretty. It uncovers bad dental abscesses you weren't aware you had. Sinus block if bad enough can lead to a brain blood clot (Cavernous Sinus Thrombosis) or compromise of an eye (the bone punches into the nerve or muscle).

(5) If you push it (I once did) above 18,000 you will be hypoxic on cannulas. You need an occlusive mask. Don't thy this without a built in mic; when you move the mask to talk, you get hypoxic before the end of the sentence. BTW, you won't have enough molecules to say more than twelve words in a row. The air it THIN up there. Get the one with the Mic INSIDE the mask.
(6) At 24,000 you need an occlusive face sealing affair as there just aren't enough molecules even if EVERY ONE is an oxygen molecule.
(7) At 27,000 you need a slight pressure mask; see 6 for reason.
(8) Airline pull downs at 10,000 isn't to keep you sane. When they lose pressure at 37,000, it's to keep you dumb stupid but alive until they can get to 10,000.
(9) Bends. If you have a screamer Turbo Single or T37 you can get to altitude fast enough to get bent even if you haven't been diving. It's happened.

Oh, and BTW, inspector: When you are planning to fly a GA light single to 18,000 it's probably because your mission is to >75% of the capability of your aircraft. So now you have all the weather, ice, and fuel considerations and might be very dumb. Brief The PLAN AND FLY the plan, or abort. No other choices."

"Um....oh I see. We'll let's move along to another topic......"

Did he have that same glazed over look with the smiles and head nods my grandma has, when I say anything technical to her?

 

[Ted]

As expected, an excellent synopsis by Bruce.

I took the Navajo up to 17,500 once out west coming back empty from a trip. That was enough. It was a 3 hour flight, I drank 3 glasses of water with lunch, and not much came out before I hopped back in for the (much lower altitude) next leg. The dehydration was the most noticeable effect, as I was on good oxygen and my pulse oximeter confirmed (didn't help that I'd also been flying pretty much non-stop the previous two days). 15,000 is about as high as I want to go without pressurization unless there's a good reason for me to do otherwise. I've done 15,000 a number of times and my body is happy with that. Your body may act differently.

 

[BillTIZ]

I've flown gliders cross country, spending 5 hours bouncing between 12,000 to 17,500MSL and spending a lot of that time between 15,000 to 17,000.

Using a canuala, watching the O2 levels, covering up the arms from UV exposure, and drinking, drinking, drinking. My bladder is trained from 10-15hr B-52 and B-1 missions, but normally the first thing a glider pilot wants when he lands is to visit the nearest bush. Then the cold beer, and yes, that is a bad choice for rehydration.

 

[CJones]

This was the topic of my "teach me a ten minute topic" on my CFI oral. The examiner had Zero clue I was an AME

"(1) You dehydrate like crazy at altitude. The air has Zero moisture at 17,000. It's about 300 ml per hour.
(2) As a result cardiac output goes down so the blood delivery train discharges at lower residual partial pressures as you have to unload the remaining blood more thorougly to get enough.
(3) The brain shuts down frontal flow (judegment areas) to maintian function, so HYDRATE LIKE CRAZY. When I did PSP-->DPA isn the 1993 AC Spruce, after 7:50 I got out, had two whole Diet Cokes and still didn't pee. I was totally dry, and had almost made some stupid mistakes (like descending into a barrel after I had a Vac failure).

(4) Gas effects- there is always some wisenheimer who eats beans the night before the chamber ride. BTDT twice and it's not pretty. It uncovers bad dental abscesses you weren't aware you had. Sinus block if bad enough can lead to a brain blood clot (Cavernous Sinus Thrombosis) or compromise of an eye (the bone punches into the nerve or muscle).

(5) If you push it (I once did) above 18,000 you will be hypoxic on cannulas. You need an occlusive mask. Don't thy this without a built in mic; when you move the mask to talk, you get hypoxic before the end of the sentence. BTW, you won't have enough molecules to say more than twelve words in a row. The air it THIN up there. Get the one with the Mic INSIDE the mask.
(6) At 24,000 you need an occlusive face sealing affair as there just aren't enough molecules even if EVERY ONE is an oxygen molecule.
(7) At 27,000 you need a slight pressure mask; see 6 for reason.
(8) Airline pull downs at 10,000 isn't to keep you sane. When they lose pressure at 37,000, it's to keep you dumb stupid but alive until they can get to 10,000.
(9) Bends. If you have a screamer Turbo Single or T37 you can get to altitude fast enough to get bent even if you haven't been diving. It's happened.

Oh, and BTW, inspector: When you are planning to fly a GA light single to 18,000 it's probably because your mission is to >75% of the capability of your aircraft. So now you have all the weather, ice, and fuel considerations and might be very dumb. Brief The PLAN AND FLY the plan, or abort. No other choices."

"Um....oh I see. We'll let's move along to another topic......"

Great info as usual, Doc.

Question to piggy-back on this info: Does good physical/cardio fitness play a factor in how well one's body would handle unpressurized high-altitude flight as opposed to a slug like myself?

 

[bbchien]

Great info as usual, Doc.

Question to piggy-back on this info: Does good physical/cardio fitness play a factor in how well one's body would handle unpressurized high-altitude flight as opposed to a slug like myself?

Altitude acclimated piltos do better between 10,000 and about 15,000. But with the shift in the unloading curve, when they run out of O2 the "Crashout" is more severe than a flatlanders'.

Cardiac aerobic fitness does help some as there is more "rate reserve" when the pump is struggling to provde enough....but it is usually trumped by dehydration.

Stay wet. Little salt, please (you'll have to pee and you'll dehydrate), unless the cabin is hot, which at alitutde it IS NOT.

 

[maddog52]

Excellent post by Dr.Bruce. I used to fly the T-37 up to FL 250 all the time. Not a whole lot of effects other than those already mentioned. A well fitting mask is a must for extended time on the hose. Nothing worse than having the bridge of your nose pressed on for a few hours.

One effect of breathing pure oxygen from a sealed mask for extended time is delayed ear blocks hours after you land. Apparently the tissues of the inner ear absorb pure oxygen better than normal air creating a vacum behind the ear drum. Maybe Dr. Bruce can confirm this. I've woken up at night hours later with an ear ache after a long flight sucking the hose for a few hours. Multiple valsalvas after landing should help prevent this.

 

[bbchien]

Yup. The reason we had to strap on the Scott 2000 before engine start was NOT hypoxia. It was to washout nitrogen, so we couldn't get bent. Max climb near 5,000 fpm CAN do that to you if you have Nitrogen in your system.

In my class there was a guy who didn't do this (had a sloppy fit) and didn't get denitrogenated. When he started hearing the lawnmower at 25,000 feet, FIVE MINUTES later, his trainer captain got him down fast, into the Baro Chamber. i've never seen them ove that quickly. He got "re-educated" as an instructor......

After you get down, you are still washed clean. You start readsorbing Nitrogen from the atmosphere again, on the ground. All That N2 diffuses back into the sinues and physcially displaces the 100% O2....venting it out the eustacean tube = delayed air block.

I'd forgotten about that. Thanks.

 

[bbchien]

I have been corrected by a poster. The air up high is not totally devoid of mosture. It just contains wayyy less than the 18 gms per Deciliter of gas that is what saturates the alveolus. IIRC it's about 2 gm of moisture....but I'd have to get out the books. The exception, of course, is visible cloud: particulate water. But the GAS itself is pretty dry.

But in any case, the lungs provide the moisture for all that minute aleolar ventilation and it comes from your blood fluid volume.

 

[COFlyBoy]

Hey Doc, on Thursday I flew from KAPA to KAEJ west of Denver. We went over at 10.5 and I was using a little 30$ PulseOx dohicky. I noticed that my pulse rate was higher than normal. I normally run 50-60 bpm (I'm 34 years old, with low blood pressure). And on this flight I was around 80 bpm with ~92% O2 saturation. Resting saturation at 5500 is 97%.

So my question is, does the higher pulse rate come with the lowered O2 saturation or is it an altitude effect that would hit folks using supplemental oxygen.

 

[murphey]

What about an altitude chamber ride? Are the symptoms and possible problems just as prevalent or likely, or are these for long duration trips?

 

[Jay Honeck]

When we drink bottled water at altitude (we go as high at 10,500 routinely), it's always educational to watch the bottle collapse during the descent.

This makes me especially grateful that our bodies are not airtight vessels...

 

[bbchien]

The higher than normal rate is your body pushing more hemoglobin containing cropuscles through the unloading depot because each car contains less off-loadable hemoglobin.

That's even without dehydration.

Add dehydration and it's harder for the circulation to do the "more rail cars, smaller loads" thing. The oxygen consuming brain at the end of the train line just gets less. at about 18mg O2/100g brain per minute, parts of the brain are shut down to preserve consciousness.

Supplemental oxygen reverses most of this but not all. Why? Carbon Dioxide is pumped out on the same train, though because CO2 is more diffusely soluble in the blood, the effect is much less (the train cars are relatively larger in the eyes of the Manufactured CO2 needing a ride out).

In the alittude chamber ride, we're talking 25,000 or about 0.4 of an atmosphere. All nonessential brain shuts down in about fifteen seconds. Judgement is lacking and information processing slows to a bare crawl. At that point dehydration is an "IF I survive...." phenomenon.

 

[Mtns2Skies]

Being acclimated to 8,000 (thats where I live) and in very good shape Approximately what height would I start to really need O2 (hypothetically disregarding FARs) is it much if at all different from flatlanders?

 

[thomascannon]

Like any pilot, I assume I'm indestructible. In some ways, I am. I can pull G's like a champ.

Can't handle altitude though. I start getting hypoxic above 11,500. Don't smoke, I get plenty of exercise (mostly in the water, so the lungs get a workout too) and I'm in my 30's.

No idea why I'm more susceptible than I wish I was, but I am. Would love to know why, but don't even have a guess.

 

[Henning]

When we drink bottled water at altitude (we go as high at 10,500 routinely), it's always educational to watch the bottle collapse during the descent.

This makes me especially grateful that our bodies are not airtight vessels...

The downside to that though is it makes us susceptible to all the other gas laws which is what makes us susceptible to getting "the bends" and a few other pressure/expansion issues.

 

[bbchien]

Being acclimated to 8,000 (thats where I live) and in very good shape Approximately what height would I start to really need O2 (hypothetically disregarding FARs) is it much if at all different from flatlanders?

That is Soooooooo very variable that for years FAA would not make a comment on that, nor tell you oxygen flow rates.

Best thing is to buy a $40 drugstore pule oximeter and check it out. Most us 90% blood sturation as the cutoff because the body starts the tachycardia (attempt to deliver more O2) jsut below that level.

It's even variable from day to day, (same person).

 

[Henning]

That is Soooooooo very variable that for years FAA would not make a comment on that, nor tell you oxygen flow rates.

Best thing is to buy a $40 drugstore pule oximeter and check it out. Most us 90% blood sturation as the cutoff because the body starts the tachycardia (attempt to deliver more O2) jsut below that level.

It's even variable from day to day, (same person).

It's even variable morning to evening of same day same person....

 

[azure]

Can't handle altitude though. I start getting hypoxic above 11,500. Don't smoke, I get plenty of exercise (mostly in the water, so the lungs get a workout too) and I'm in my 30's.

No idea why I'm more susceptible than I wish I was, but I am. Would love to know why, but don't even have a guess.

I'm definitely more susceptible too, and always have been. When I did the Longs Peak trail at 27 (14,260 MSL or something like that) it took me a week of acclimating myself to altitude at 9,500 before I felt ready to tackle it. I could function at 12,000 but got short of breath easily. Two cross-country cyclists I was camping with did the climb their second day at the campsite and they were from San Jose. When I was a student pilot I had a semi-panic attack at 8,500 on one of my later solo XCs because my elevated pulse rate freaked me out. That's something I wish CFIs would cover, the effects of altitude are so variable that some of their students might encounter some of them even in a normally aspirated single.

I'd like to piggy-back a mystery on this subject though. I took a friend to MCD a few weeks ago. We were at 8,500 on the way up for about an hour, and then 7,500-8000 and a little higher on the way back (climbing over some clouds) for maybe 45 minutes. What we did there wasn't too strenuous, some easy cycling, hiking in the Arch Rock area (to get away from the crowds), and then we rode back up the British Landing road to the airport. She is not in great shape but is fairly healthy, but with a decades-old history of CFS/ME (in complete remission for about 5 years now). She seemed fine that day. But when I talked to her last night, she reported that the next day she felt terribly lightheaded and weak, completely unable to function until the evening. She has flown with me before and was fine every other time except after a trip three years ago to 3W2, when we cruised there at 6,500. Last night she told me that she had the same delayed-reaction illness the next day at that time. We walked quite a bit around the island that day, too; it was somewhat exhausting for me too.

Does anyone know whether some people with CFS/ME have a delayed reaction to mild hypoxia plus mild exercise, something like (or maybe another form of) post-exertional malaise?