Almost every trekking season in Nepal, some ignorant trekker, usually in the Everest region, will die of altitude sickness. Majestic mountains make great pictures and impart a sense of peace. It’s not immediately obvious that the very atmosphere surrounding these snowy giants is most hostile to the fragile human being. Why do some aunties collapse after landing at Lhasa? Why do some hunks who think they are stronger than the aunties collapse after running around for a day?
At sea level where most Singaporeans reside, the air pressure pushes 76cm of mercury(Hg) up the tubing of a mercury barometer. As one ascends, air pressure drops. When the pressure is lower, molecules of oxgen become spread further apart. While the relative percentage of oxygen in the air remains unchanged, fewer molecules of oxygen are taken in with every breath. The degree of oxygen starvation depends on the altitude, pressure and air density. The higher you go, the lower the pressure/air density and the greater the degree of oxygen starvation or hypoxia. What happens to the body when it is starved of oxygen?
The first symptoms of AMS are usually headache and nausea/loss of appetite. Dizziness and loss of balance/coordination may follow. Without appropriate remedial action, serious, life-threatening situations like High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE) may ensue.
Fortunately, the human body is able to adjust and adapt to living at high altitude. It has been estimated that 40 million people live and work at altitudes between 3000m(52cm Hg) to 5000m (34cm Hg). At 5000m, the pressure is half that at sea level. This means that the body only receives half the amount of oxygen as that at sea level. How do these individuals survive?
Before we talk about acclimatisation, let’s take a look at when acclimatisation kicks in. Do we need to acclimatise before we take a bus to the Cameron Highlands (a gain of more than 1000m)? Why not?
To answer that, let’s take a look at the oxy-haemoglobin dissociation curve. Trace the curve from right to left. Notice that it goes flat for quite a while. This means that declining pressure has no effect on the ability of haemoglobin to pick up oxygen from the air up to a certain point.
This point has been identified as an altitude corresponding to about 3048m. With this knowledge, airlines can keep cabin pressures at altitudes around 2000m without affecting passenger comfort. You can certainly take a bus to the Cameron Highlands or even to Mt Bromo without acclimatising. It’s only when you hit 3000m that the body senses that something is amiss and tries to compensate.
Immediate responses include hyperventiltation (quicker breathing), increased heart rate and increased cardiac output. While hyperventilation increases the amount of oxygen that is brought into the lungs, it also causes the body to lose carbon dioxide. When the body loses carbon dioxide, blood becomes more alkaline. The mild, first symptoms of AMS are probably due to changes in blood pH.
Given enough time to react, the body makes long term adjustments to hypoxia by increasing the oxygen carrying capacity of blood. This is accomplished by decreasing plasma volume by promoting urination and synthesising more red blood cells and haemoglobin. How long does it take?
Well, theoretically, full acclimatisation to 3000m takes about 2 weeks. From here, every 600m gain would require an additional week. This means that theoretically, a trek to Kala Patar (5545m) will take 4-5 weeks. That’s totally unrealistic for any working Singaporean.
However, you might like to know that many Singaporean trekkers can complete a Kala Patar trek in just 14 days. And one cold winter afternoon on 25th January 2009, a 45-year-old Singaporean arrived at Island Peak base camp (5100m) having landed in Lukla (2850m) only 5 days before that. He was still in Singapore 6 days before that. According to the Sherpas, he is the only non-Sherpa who has managed to make such a rapid ascent and survived.
How do these people cheat AMS? In the less extreme case of a 14-day Kala Patar trek, a one day rest at Namche Bazaar is adequate for the majority of people. They may struggle a bit to get to Tengboche, but beyond that, the walking gets easier. Another rest day at Dingboche is probably adequate for most people. This can be followed by another rest day at Lobuche. To avoid the problem of debilitating AMS, the final assault on Kala Patar is best based from 4900m Lobuche and not 5164m Gorak Shep. Many trekkers have disagreed with me on this strategy. They felt that with Gorak Shep so close to Kala Patar, it would make more sense to trek to Gorak Shep first, spend the night there and then take a leisurely stroll up Kala Patar the next morning.
Since Everest was first climbed, it was widely held that a staged ascent was the way to go for any alpine peak.
For this style of climbing, climbers would plan and place camps along the route of ascent and deposit supplies at each camp. As they move higher and higher, they acclimatise and make a final push from the last and highest camp. The kiasu can place 100 camps and take a few steps out of the last camp to summit. Purely from an acclimatisation point of view, a staged ascent is probably the only way to go.
In reality, staged ascent (also known as seige tactic) is full of disadvantages. First of all, you need an army of porters to carry supplies that will last you for months on the mountain. With more people involved and slower movement, there is greater risk of confusion, miscommunication and casualties. Longer stays by large expedition groups strain the environment. Prolonged exposure to the elements may cause more health problems. Staying high up on a mountain for long periods exposes climbers to hazards like avalanche and falling seracs.
Highly critical of seige tactics is the greatest contributor to mountaineering of all time, Reinhold Messner. The alpine style of climbing he pioneered shocked the world which didn’t believe it was possible to climb Everest without oxygen and/or full acclimatisation.
Pure alpine style requires great skill, talent and commitment. It can even be dangerous if the weather turns foul and there are no camps nearby to descend to. The climbers are self-sufficient, carry all their supplies with them, do not fix ropes and often do not even set up higher camps. They leave base camp or get out of their bivouacs in the dark and head for the summit in one tremendous bound. It may seem a dangerous, foolhardy thing to do, but the alpine climber’s exposure to the mountain is actually shorter than the expedition climber’s. Obviously, not many of us can do this sort of thing. I don’t even recommend it. My reason for mentioning this is to illustrate the fact that you don’t have to spend months acclimatising on a mountain to be able to summit it. You can spend some time at base camp, do a few practice climbs without staying any higher than base camp and then head for the summit in the dark and return in one day.
Consider the folks who race up 4095m Mt Kinabalu. Are they acclimatised to 4000m or even 3000m? Not necessarily. Yet, these competitors who can race to the summit and return to Park HQ within a couple of hours might fall ill from AMS if they were not allowed to descend and have to spend a night at Laban Rata or the summit. The majority of people who have a high level of endurance can do a hit and run on the summit without developing AMS. In fact, some strong trekkers who suffered AMS at night at Laban Rata, unable to climb any higher the next morning, are known to summit on the first day on another trip without spending the night at Laban Rata. The duration of one’s exposure to high altitude is what triggers AMS.
You probably won’t be reading this if you’re already a climber of big peaks. You probably have your own style. For those not so familiar with high altitude trekking, it might be interesting to note that you can get away without full acclimatisation if you can do a quick hit and run to base camp within a day. This is precisely the logic for staying at Lobuche, moving out to Kala Patar at dawn and then returning to Lobuche on the same day. The trekker may feel exhausted, but recovery is rapid. If he had ascended to Gorak Shep and spent the night there, the next morning may find him sick in bed, unable to take even one step out of the lodge.
Aid To Acclimatisation
The purists may not believe in them, but certain drugs can help in acclimatisation. One drug that every high altitude trekker should carry is Diamox or acetylzolamide. The dosage is 125mg twice daily starting one day before ascent. For maximum efficacy, it is important to take this drug prior to ascent. How does this drug work? It is a carbonic anhydrase inhibitor. Remember we mentioned about hyperventilation reducing blood pH because of carbon doxide being breathed out from the lungs? Carbonic anhydrase is the enzyme that causes carbonic acid to dissociate into carbon dioxide and water. A drug that inhibits this process will help retain carbon dioxide and maintain a stable blood pH. Maintaining stable blood pH is also important in promoting healthy breathing patterns during sleep. Diamox has positive effects on the process of acclimatisation. It does not just mask symptoms as some folks claim. For individuals not allergic to sulphonamides, Diamox is a safe and useful prophylactic drug for a fast ascent.
The body will attempt to dump fluid to decrease plasma volume during the acclimatisation process. It is important to keep the body well hydrated. Headache is sometimes caused by dehydration. Drinking sufficient water is very important. Ironically, the body will not be able to hold “sufficient” water. As one acclimatises, urine output increases and blood gets thicker. You may get a headache at the end of a long day’s trek even if you don’t have AMS. Drinking lots of water will get rid of the headache if it’s caused by dehydration. However, as your headache clears, you may find yourself running to the toilet every 10 minutes.
With low carbon dioxide level in the blood, the body may “forget” to breathe deeply during sleep. It is unhealthy to sleep for long hours during the daytime at altitude. This may worsen symptoms of AMS. It is also not advisable to overexert (like the hunks who think they’re not aunties). When you first arrive at a place situated at high altitude, stay awake but restrict activity.
Many Westerners think that herbs are awful-tasting placebos that only ignorant Asians would use. I can only provide personal experience and anecdotal evidence for the use of herbs to give the high altitude trekker or climber an edge over his peers. One highly potent cocktail I’ve discovered, is ginseng coffee. I’m not sure if the 3 in 1 coffee mixes work. Personally, I use filter bags of a branded wild American ginseng. The coffee doesn’t really matter as long as it’s genuine coffee. Trekkers and climbers tend to feel lethargic at high altitude. I find this mixture highly ergogenic.
Perhaps the biggest aid to acclimatisation or pre-trip acclimatisation is a device called a hypoxicator. This device delivers oxygen-deficient air to the user when he/she is still at home in the lowlands. His/her body senses the lower oxygen level and gets tricked into producing more red blood cells, resulting in pre-trip acclimatisation. Fortunately, one does not need to breathe from a hypoxicator 24/7 to yield the desired results. A hypoxicator I designed myself works best when used for 2 hours every day for 2 weeks before the trip. The user will feel breathless and giddy while breathing from the hypoxicator. Recovery is rapid once the hypoxicator is removed. Longer term adverse effects from the use of this device includes subconjunctival bleeding. The whites of the eyes turn red for a few days, but does not affect vision. Someone who has used my hypoxicator can safely and rapidly ascend to 4500m without any problems. Above this, the same rule of one day’s rest every 500m ascent is recommended.
Strategies For Fast Ascent
By now, it should be obvious to anyone that it’s a waste of time trying to acclimatise below 3000m. Only the rare, highly susceptible individual will be adversely affected below that altitude. One should head straight for a nightstop above 3000m on the first day and rest for 1 or 2 days if you can afford the time. If the “highlight” of the trip, whether it’s a summit or the equivalent of a Kala Patar can be reached by a hit and run technique, go for it. This may take 2-3 days off a “standard” itinerary.
Why should anyone listen to me? Because I’m that 45-year-old Singaporean who is the only non-Sherpa to have walked from Lukla to Island Peak base camp in 5 days.
© Chan Joon Yee 2009
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