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Everyone who thinks about climbing Kilimanjaro or any other substantially high hill also thinks about the affects of altitude and its potential not only to wreck the dream of summiting but also to have a far more profound, even life-threatening, impact on their well-being. But what is high altitude, why is it an issue and how can one manage the risks? The pages under this "high altitude" heading are a summary of our reading and while they are hopefully informative of our experience, they are by no means definitive advice on the subject, on how any individual will react when in a high altitude environment or what to do to treat anyone suffering from the affects of being there. For that, everyone intending to ascend to altitude should undertake their own research and seek their own professional advice. The International Society for Mountain Medicine and www.altitude.org seem pretty good places to start, the latter being recommended in papers given to us when we went to the doctor for our jabs. The first thing that struck us is that high altitude is not necessarily as high as you might think being anything above just 1,500m. 3,500m sees you moving into very high altitude and as you pass the 5,500m contour you find yourself at extreme altitude. This means that the average Alpine trek can take you well into the high altitude bracket although most who write on this subject suggest that the affects of altitude are unlikely to impact significantly on the average person much below about 2,500m. We certainly haven't experienced any ill affects during our many excursions in the Alps or similarly high mountains but Kilimanjaro is a different prospect as its summit falls well into the extreme altitude bracket. Indeed virtually the entire climb is in the very high bracket with camp at the end of day 1 already near the top end of the high altitude bracket at around 3,000m. The reason people struggle as they ascend to these extremes is that while the air still contains the same 21% oxygen, its density decreases, or, to put it another way, the air is thinner and every breath therefore contains less oxygen. At the summit of Kilimanjaro there is less than half the oxygen per breath as there is at sea level. The body therefore has to work harder to get enough oxygen by breathing deeper and faster. This is especially so when it is being worked harder by an activity like climbing a mountain. The result is that you feel out of breath, which is OK as long as your breathlessness reduces rapidly when you stop to rest. However, despite breathing deeper and faster it is not possible to attain normal (for your home altitude) blood oxygen levels at high altitude unless you have moved to that altitude at a rate that allows the body to adjust or acclimatise. In simple terms, if you do not allow the body time to adjust it cannot continue to function properly and you may suffer from Acute Mountain Sickness (AMS), which is also known as altitude sickness. In addition, and if you fail to react to what your body is telling you you may succumb to the much more sinister and potentially life-threatening High Altitude Cerebral Oedema (HACE) or High Altitude Pulmonary Oedema (HACE). Key to success is therefore allowing your body time to adjust to its new environment. Literature suggests that this takes between 1 and 3 days at any particular altitude. So, if you climb to 3,000m and stay there for several days your body acclimatises to that altitude. If you then climb to 3,500m your body must acclimatise again. But this does not mean you can helicopter yourself in to some extreme altitude and expect your body to cope simply by staying there for a few days - it just doesn't work like that. You have to start low and gradually move higher. The literature also explains that while everyone acclimatises at a different rate a good rule of thumb is that above 3,000m you should not sleep more than 300-500m higher than the previous night and for every 1,000m height gain you should spend a second night at the same elevation. Climbing higher than this on any day should be OK (within reason) as long as you drop back down to sleep at lower altitude. Climbers often refer to climbing high and sleeping low. The problem on Kilimanjaro, and the reason anything between 30% and 60%+ fail in their attempt to reach the summit (depending on which statistics you are reading), is that the "acclimatisation maths" simply doesn't add up. The average overall height gain between entry gate and summit is about 4,000m, so if one were to increase altitude by 500m per day and to stay a second night at the same altitude for every 1,000m height gain it would take something like 11 days to reach the summit; reduce the daily climb to 300m and you need a whopping 16 or 17 days just to reach the top. Trouble is, most Kilimanjaro climbs last only 6 days, though an extra day is offered on some tours such as ours and some of the treks coming in from the west take about 10 days. Therefore, unless a climber is already well acclimatised before they step onto the mountain, perhaps by climbing on Mount Meru beforehand, which, of course, adds to the cost, they will almost certainly have some issues with the altitude ranging from perhaps a mild headache to severe AMS or worse. While important acclimatising is not just a question of ascending slowly but is also influenced by fluid intake, diet and other factors. To give the best chance of success in this hostile environment literature suggests the climber should ensure they:
If, despite your best efforts to acclimatise, the mountain takes its toll on you the golden rule appears to be to know your body (and those climbing with you) and to turn back when it is the altitude that is preventing progress rather than your own fitness or motivational level - identifying which is affecting a climber is of course the million dollar question! The other altitude links provide more detail on AMS, a phenomenon known as periodic breathing and what we will be doing to help our acclimatisation in addition to following the instructions of our guide once we are on the mountain.
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