I know the theory behind effects of high altitudes on the human body is not entirely understood and because of cross-influence it is a difficult topic. It's not an exact science.
Having said that I will give an example case which happened to myself this year. I try to give all relevant information. And I am asking myself for quite a while (and therefore I am asking you now) what exactly occurred in my body in high altitude and how I could react better the next time.
My background is:
- quite a few alpine tours under 4000m (13.000')
- good fitness level but no fitness enthusiast (I am able to do tours with 10 hour walking and/or 2000m elevation gain without big problems in a proper speed)
- mild lung problems (no 100% capacity, maybe 80-90%)
So we did a trip to South-America, started doing proper acclimatization tours where we always slept around 3000m (10.000') and climbed 4 mountains with increasing height between 4200m (13.800') and 5100m (16.700'). On that tours I had no problems at all and seemed to be very fit. We also had days to rest.
Then we tried to climb a mountain of 5900m (19.300') height. We were supposed to sleep from 5pm to 10pm which I wasn't really able to. I slept maybe 15 minutes which of course is not the best preparation for a long day. Still I was motivated, ate and drunk as much as possible before we start. We were driving by car until 4800m (15.700') I think. There we start climbing. From 5000m (16.400') on I got problems with the stomach. I felt bad and this got worse. As a consequence I wasn't able to eat and I even stopped drinking properly. Later on I was starting to feel weaker and weaker. I had no lung problems or problems breathing but I felt so extremely exhausted. I had no headache at all. Finally at 5500m (18.000') I made the decision to turn around. Even descending I had to stop and even sit down each few minutes because of the exhaustion. I never felt like this before.
I know it's normal to fatigue when you are not sleeping/eating/drinking enough. But the body has reserves. Because I had no headache I asked myself over and over again if I got AMS (wiki) and how serious my situation is and when I have to stop ascending. This is the main question here, how to decide and react properly in such a borderline situation.
There was a lot written about AMS and I knew the symptoms before my trip. This question covers the general ideas of diagnosing severe altitude illness. I doubt my question is a duplicate, it is just a very special case (a case example) which shows how difficult correct judging about the necessity to turn around is.
Like the linked Lake Louise Score states, it is always headache plus symptom X and maybe others. Because of the missing headache I was really unsure of my situation and how far to proceed. The mountain guides climbing with me are not able to assume the responsibility.
While descending under 5000m (16.400') I started feeling stronger. That's the main reason I assume afterwards that I got altitude sickness. But I (and also the mountain guides) was not able to judge correctly on the way up.
How would you judge? How would you react? What to do better next time preparing a high altitude climb?