At what altitude would an average person feel the effects of lowered oxygen content?
For example, do most people notice any shortness of breath driving over the summit of Tioga pass in California?
By “average”, I mean to exclude persons with one lung and persons of Superior Physical Conditioning. 
Peace,
mangeorge
I think you need to look at relative vs. absolute altitude. I was listening to a college football playoff game this year where they were talking about the problems another team was having playing in Montana. The announcer said, “We’re at 3,800 feet altitude! There’s no oxygen up here!”
I was amused, because I live at over 5,000 feet and have no problem at all. I do get winded faster hiking at 10,000 feet, but it’s not a big deal to me. Friends from the coasts, even the ones in good shape, have trouble jogging a quarter mile at over 10,000 feet.
When I lived in Colorado at 7,000 feet altitude, I drove my car to the top of Pike’s Peak (14,000 feet) several times with no problem. When I drove out there from California while I was in college, my souped-up Camaro couldn’t even get to the top.
It’s all what you’re used to.
[nitpick]
The percentage of oxygen in the atmosphere doesn’t appreciably change with altitude. There’s about 23% oxygen in the air at sea level, and about 23% oxygen in the air at the top of Mt. Everest. So the ‘content’ is the same.
The problem is the pressure is lower, so there is less air to breathe.
As far as altitudes go, here is the relevant FAR:
It depends on the level of physical exertion. For a reasonable rule of thumb, figure that an increase in altitude of 5000’ makes running upstairs/uphill feel much more strenuous.
Tioga Pass is just shy of 10,000’ MSL. Helathy non-smoking adults acclimated to sea level wouldn’t notice much if exposed to that altitude for short periods while sedentary, but would almost certainly be sort of breath when engaged in any real exertion (e.g walking briskly, or even a short distance uphill).
The issue is of course the partial pressure of oxygen, which definitely declines with increasing altitude.
That’s what I was trying to say.
Airliners are typically pressurized to about 6,000 ft or more.
Here is a very readable, easy to understand medical article on the effects of altitude on the body.
I don’t know how “average” I am, but I live about 500 feet above sea level. When I go to Denver (elevation 5,281 ft) I’m okay, but when I get to Colorado Springs (elev. 6,035 ft.) I get a headache.
Once my host asked me how I liked Colorado Springs.
“It’s beautiful. When does the headache stop?”
“About 3 days.”
This is highly anecdotal, but from experience I would say a reasonably fit person, accustomed to living at sea level, might experience altitude effects (shortness of breath, etc) at 3000 metres but not at 2000 metres, when engaged in vigorous physical activity.
I drove over the pass in Rocky Mountain National Park. 12,300 feet. I felt no effects in my car. At the top I got out to do a short hike up a trail there. I could walk about 200 yards before having to stop and rest. Each time I walked, I could go less distance before stopping. I hiked maybe a mile total, and started to feel altitude sickness.
I drove down to the visitor’s center in the thick air of 10,000 feet and had some food and drink and was OK after a half hour or so.
When I got back to about 7500 feet I had to pull over and take a nap, I was just wiped out from the trip.
YMMV
I once spent a week in Denver (5280 feet), followed by several days in Aspen (~7000 feet). In Denver, I felt a definite difference when I ran, but could complete my two-mile run, albeit at a slower pace. In Aspen, I couldn’t run for much distance before running out of breath, and had to settle for going to the gym and walking on an inclined treadmill.
I’ve has similar experiences exercising in Santa Fe (~ 7000 feet).
Never get headaches from altitude though.
While sitting around doing nothing I’m fine at 5,000 MSL (I live at 534 MSL) but when I exert myself - climb a few flights of stairs, hike a mile or so, etc. - I notice reduce stamina. It’s anecdote. I’m far from an elite athlete. I do have asthma, but my last few lung function tests showed me performing at 95-98% of average for a woman my age/weight, so take that as you will.
[entirely off-topic]Broomstick, check your PMs.[/entirely off-topic]
More anecdotes. I worked for an aerial photography company here in Los Angeles. On occasion I would pinch hit as one of the photographers. I can not recall the exact altitudes that OSHA has in place with regards to having oxygen in an unpressurized cabin, but sometimes (though rarely) the work we did would be as high as 20,000 feet. I want to say it was at 10,000 that the use of oxygen became mandatory, but we would frequently just have the masks at hand and take occasional breaths from it.
One of the pilots and I day hiked up Mt. Whitney one year going from near sea level to nearly 15,000 feet in less than 24 hours. It’s an aside from what I want to say, but we got back to the truck and then drove back home to L.A. It was the longest damned day and a half of my life. Anyway, more to my point, I definitely noticed the effects of hypoxia while on the mountain. I was in excellent physical condition at the time so cardiovascular wise I did not have any problems at all. However, the headache and what I can only call a narrowing of focus was an interesting thing to note. It took a deliberate effort to life my eyes from the trail to look around and become aware of what I was doing. Of course some of this was due to the physical effort I was exerting (11 miles one way with a 6500 foot gain in elevation.) There were other symptoms such as nausea, but headache and semi tunnel vision I most recall.
Fast forward a few months and I was called upon to act as photographer with this same pilot. Our jobs took us to Central California and after finishing the work, refueling (both the plane and ourselves) we still had a lot of daylight left and so we took the scenic route home. It is now mid December and we flew to Mt Whitney and did two or three circles of the summit at about 16000 feet after which we took a long slow descent back to Burbank. Being curious I deliberately did not use the oxygen as I wanted to note the effects of a quick ascent to altitude versus our hike. I did not get the headache, but did notice a bit of euphoria and, most interesting, a lessening of mental ability. I had some minor paperwork to do so I filled it out, when it came time to do very simple addition I found I could not add two single digit numbers in my head. At least I struggled with it for a minute or two. It was a very odd experience, to know that I should be able to do this, but could not.
What brought this question for me was a (lucid) dream I had last night. It was chilly, and I had pulled the blankets up over my face as I dozed off. The slight smothering feeling brought a flash of memory of being in a car and feeling short of breath. I don’t remember much of the dream, but somebody, maybe my dad, told me it was due to the high altitude. I also remember a long descent and lots of signs about that descent. It was probably Tioga Pass that I remembered and brought that dream. I didn’t like that feeling so I woke up.
Thanks for the answers. I wondered if it could have been the altitube of that childhood trip that I remembered.
Guess I’ll never climb Mt Everest.
There are a number of physiologic adaptations to altitude, including an increase in hemoglobin, increase in respiratory exchange, and shift of the oxy-hemoglobin dissociation curve in a direction which causes the hemoglobin to bind less tightly to oxygen. These effects take hours to days to equilibrate.
Ordinary physiology, such as the capacity to increase cardiac output in response to a lowered partial pressure of oxygen, varies widely.
There is no specific altitude which causes problem, and the more serious problems such as high-altitude pulmonary and cerebral edema–or even ordinary altitude sickness–are not necessarily a reflection of how well-conditioned the individual is to lower-altitude activity. It’s not uncommon for the younger or more athletically-fit individual to be the one who craps out at altitude.
As a personal example, I headed a small party walking up Kilimanjaro (Uhuru peak is just over 19,300 feet). The oldest, fattest and laziest-trained (me) and the youngest hiked to the top. The middle three, in their 20s, crapped out from the high altitude. A few weeks back I was at Khardung-La in India, which is about 18,000 feet with a guy in his 60s who had lived his life at sea level. He was totally fine.
Somewhere around 17,000 feet I really started feeling the effects of the altitude as I was hiking toward Kala Patar (18,000’) in the Mt Everest base camp area.
Before I left for Nepal, I was living near sea level, but was in fairly good shape running 5 miles on a track in 30 minutes everyday for several months to get ready for the hike.
I hiked in from Lamasangu (6,000’) and took about 8 days to reach Namche Bazar (11,000’) where it is advised that one rest for 24 hours to acclimatize. Another rest day at 14,000 feet before reaching the final hamlet (Laboche) at 16.000’.
I felt fine leaving Laboche, but when I reached the base of Kala Patar, I was literally taking 2 steps and then having to sit down and rest. I almost didn’t make it to the top. (Kala Patar offers probably the best view of Everest in the area,)
Even after all the conditioning, gradual ascent from only 6,000’ and being at high altitude for over two weeks, 18,000 feet completely kicked my ass.
Dunno entirely, but my experience as a flatlander (US Midwest)
I was in excellent shape in High School (soccer team). We took a HS trip to Europe.
Even at a fairly low point in the Swiss Alps I was crippled. Short staircase up part of a small mountain and I was panting for breath at the top.
Less-than-average (fitness) guy
Until 2000 metres the effect is negligible for normal everuday activities or even mld exertion. Once you go up there you feel like a load on your shoulders. A couple of days at 2500 might be enough for acclimation. Over 3000 things get worse but most people can go by with some coca tea.
As a personal example I was able to walk for an hour at about 4700-4800 masl after four days at 3200. An hour of walking at sea level is something I avoid like the plague.
In Peru there used to be a team who played in first division football whose stadium was at 4400 masl. Sea-level would play there with little to no acclimation.