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FAA rules require that pilots flying above 12,500 ft for more than half an hour need to be on supplemental oxygen, and pilots flying above 14,000 ft need to be on oxygen all the time. Therefore, isn't it dangerous for unacclimatized drivers to go up Mount Evans or Pikes Peak? Doesn't the likely hypoxia increase the chance of car accidents a lot?

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3 Answers 3

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Yes, it can be. Assuming you just spend a little time at altitude, the problem here isn't actually the AMS or HAPE/HACE, that will come later. The main problem is the severe drop of pO2 for people who are not acclimatized. And this will happen immediately. Your oxygen saturation in the blood will drop from something like ~98% to somewhere in the 60s or 70s. This leads to a lack of concentration and reaction times before any of the more "severe" symptoms like headaches etc. start to show.

I'm guessing this is the reason for the FAA rules, to keep pilots alert at all times.

Personal anecdote: Did a study in a hypoxic chamber, went from roughly sea-level to about ~5000m (~16000ft) by stepping through a door. I was running the equipment for an experiment and had to do some last minute programming. It was a really basic task like I did thousands of times before, but I almost couldn't do it. I just felt slightly stupid but otherwise had no symptoms. The headaches only started the next day.

So if you build the same road, once flat and once over a high altitude peak, I'm certain, the high altitude one will have a higher accident rate (assuming same amount of traffic and so on) due to the impaired cognitive ability.

A study for example

Quote: Conclusions: Selective and sustained attention are impaired at altitude and improves with acclimatization.The observed changes are associated, in part, with AMS score and SpO2. The gains in cognition with acclimatization during a first exposure are not carried over to repeated exposures.

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No activity in life is totally risk free, including stepping into or out of the bathtub. That having been said, altitude sickness is real, affects some people at relatively low altitudes, and even can affect experienced climbers accustomed to high altitudes.

However, according to the Harvard Medical School:

Altitude sickness is more likely to occur in people who have a previous history of altitude sickness. It is more likely if you climb quickly, if you exercise vigorously during your first few days of altitude exposure, and if you have been living at low elevation prior to your climb. Obesity appears to increase the risk for altitude sickness. Genetics may also put some people at increased risk, particularly for high altitude pulmonary edema (HAPE).

A key point in the above quote, for a healthy person, is "exercise vigorously". A drive up, a stroll to take in the sights and shoot a few photos, and a drive down reduces the chances of an adverse reaction to altitude. Driving up, a vigorous hike or climb, followed by camping overnight, is a different scenario, with an increased risk of non-trivial altitude sickness.

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  • While exercise does contribute to altitude sickness, it is not a necessary factor. There are quite a number of reports of people with altitude sickness just by driving up with the Jungfraubahn or taking the cable car to Klein Matterhorn and taking a few photos there. And those places are below 4000m
    – Manziel
    Commented Aug 27, 2023 at 7:31
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    @Manziel Not questioning your comment, but just pointing out that It is estimated that about 1 person in the U.S. dies every day from a bathroom-related injury occurring in either the bathtub or the shower. Many more of course are merely injured. Also, like bathroom injuries, altitude sickness comes in many levels of seriousness. One has to pick one's risks.
    – ab2
    Commented Aug 28, 2023 at 23:27
  • Risk comparisons by absolute numbers are pointless if you compare groups of different sizes. Everyone goes to the bathroom every day. But a lot less people ascend to a higher altitude without prior acclimatization. As I pointed out in my answer, at 4300m altitude sickness tends to be rather mild. This is not high enough for the dangerous symptoms like HACE and HAPE, especially for shorter times spent at altitude.
    – Manziel
    Commented Aug 29, 2023 at 6:40
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    I know how to do risk analysis, thank you. Neither of us is doing it at all rigorously. Neither of us has given a denominator. Neither of us has given any of the other pertinent information: for example, how many of the people who get altitude sickness on auto excursions to high altitude have compromised lungs. Or how many people who die or are injured in the bathroom have poor balance as measured in an ordinary doc's annual exam. Time to stop.
    – ab2
    Commented Aug 29, 2023 at 13:43
  • Of course, nobody is doing a proper risk analysis here. But those two activities are so far off, that we are not even comparing apples to oranges. I understand your intended message, that life can be deadly in the most unexpected ways. But as a forum, there is also the responsibility to not downplay any risks by suggesting that one will only get altitude sickness if exercising. The key part about altitude sickness is not exercising, the key part is to drive down after a short time of high altitude exposure
    – Manziel
    Commented Aug 30, 2023 at 7:46
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There are some huge difference between a plane and a car: the car can pull to the side and stop mid-travel if the driver does not feel well. It is also likely that one of the passengers can switch with the driver. Car travel falls into the real of private and self-responsibility.

That said, driving from 1600m to 4300m without any acclimatization is very likely to cause high altitude sickness and I would rather not recommend it. However, at this altitude and with a shorter stay, symptoms are most likely limited to a headache and not feeling well. HAPE (high altitude pulmonal edema) and HACE (high altitude cerebral edema) are very unlikely at this altitude

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  • The thing is, you don't notice when you have hypoxia if you aren't cautious for the signs. Reportedly, hypoxia sometimes leads to euphoria, and the driver will be unaware that this is due to AMS. If the driver doesn't notice, they may lose useful conciousness while driving up, perhaps.
    – Johannes
    Commented Aug 25, 2023 at 13:10
  • Not sure if that is high enough. But for children that can be a problem, especially little ones that do not understand what is happening and cannot communicate properly their symptoms.
    – Manziel
    Commented Aug 27, 2023 at 7:34
  • At tripadvisor.com/… - a question about safety driving up/down Pikes Peak, of the 25 answers currently there one indeed notes a child's altitude sickness (likely headache and/or nausea, not HACE/HAPE) as a reason to turn back. So, yes, it happens, and yes, there are risks. But driving the 500-1000 miles from Texas to Colorado also had risks.
    – Jon Custer
    Commented Aug 29, 2023 at 14:59
  • The air pressure in a passenger airplane is typically equivalent to somewhere between 1800 and 2500 meters, an often for substantially longer than it takes to drive up and down Pikes Peak.
    – Jon Custer
    Commented Aug 31, 2023 at 19:07
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    Congratulations, you are not as sensitive to altitude as some others. But you asked about the general population. As noted in the introduction to one article (Open Access J Sports Med. 2015; 6: 319–328.) - "25% of conference attendees at a medical conference in the Rocky Mountains, at elevations of ~2,000 m, reported symptoms attributable to acute mountain sickness (AMS)". Time at altitude plays a role, so the few hours driving up and down is less likely to lead to symptoms than driving up and camping overnight. But some people will get symptoms and should turn around and go back down.
    – Jon Custer
    Commented Sep 13, 2023 at 15:47

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