I once gave a very tongue in cheek slideshow about why Everest had never had a true ascent, in order to argue this case I looked in depth at the physiological changes that occur when we go to altitude, which are truly fascinating. Here I am going to look at how and why our bodies adapt to altitude, as well as looking at what lengths people now go to to avoid Acute Mountain Sickness and High Altitude Cerebral/Pulmonary Oedema (HACE & HAPE) on the highest peaks.
I guess the first thing to realise is why we need our bodies to adapt to altitude. This in essence comes down to the as we ascend the partial pressure of Oxygen gets less and less. This means that even at around 4000 metres we have around 40% less oxygen than at sea level, when you take this to 8000 metres we are talking about a 70% reduction in Oxygen we can get from the air we breathe.
As such when we first go to altitude we instantly have an oxygen deficit, which causes our blood to become slightly acidic, this blood acidosis is detected by the heart and a ventilation response is activated, making us breathe deeper increasing the volume of each breathe and quicker, both of which helps counteracts the hypoxia (Lack of oxygen).
Whilst the increased breathing increases the saturation of Oxygen in the blood it decreases the Carbon Dioxide saturation, leading to alkalosis which effects respiratory control and leads to the sleep aepnia (Temporary stopping breathing with a sudden gasping for breathe).
The next major change that happens in the first few hours of being at altitude is the renal response, where hyperventilation causes alkalosis in the blood is counteracted by a release of bicarbonate in the kidneys. As a part of the chemical reaction with the bicarbonate the kidneys, urination increases, which has a further benefit to the climber at altitude as it increases the concentration of red blood cells by reducing blood volume by excreting blood plasma. The blood does become more viscous or thicker, making it harder to pump round the body.
The loss of fluid through urination is exacerbated by dryer air found at Altitude, as such any climber at altitude needs to counteract the loss of so much water and remain hydrated through increased fluid intake. This needs to be achieved by balancing fluid out with the fluid you drink, another way is to take note of the colour of your urine, the dark and brighter the yellow the more dehydrated you are.
As we remain at altitude our bodies will remain in a oxygen starved state, and in order to maintain cognitive function, the blood flow to the brain is increased. As a consequent of this the brain starts to swell, at worst this can result in a cerebral oedema, at best it can result in a headache.
The next response the body has is one that amazes me, and takes around a week to ten days at altitude to occur. Eythropiotin is released by the kidneys, and when it arrives at the bone marrow, that itself has sense the hypoxia and put the EPO receptor to the surface of the cells to receive the EPO and the process starts to produce more red blood cells. In the process is halts dieresis and pulmonary hypertension.
EPO is a drug that many cyclist and endurance athletes have used to increase there red blood cell count without having to go to altitude and train. It has caused some athletes to have serious medical complications and has even resulted in death when used as an aid to performance. As such it is illegal under the World Anti Doping Agency (WADA), however it is very hard to detect as it is a naturally occurring hormone.
The last step is a muscular response where after prolonged exposure there is muscle loss. This is believed to help the capillaries get closer to the muscle cells and in particular the mitochondria, where the oxygen and energy are used to produce movement, by reducing the distance between them.
All of these changes help make the transfer of oxygen from the air to the muscle much more efficient. So much so that when fully acclimatises there is only a small difference between the oxygen saturation in our veins (after oxygen is used) between sea level and 5800 metres.
Now there are a growing number of ways that people have used to help acclimatisation. However the one true way to avoid any of the adverse effects of Acute Mountain Sickness or one of the Oedemas is through allowing your body the time it needs to acclimatise. With at least a week needed to start the process of growing more oxygen carrying red blood cells, some people simply don’t allow themselves enough time.
With low cost air fares and the ability to have ‘quick hits’ to the Alps some climbers might be interested in looking at medication to enhance the bodies ability to acclimatise. Alternatively you might be one of the lucky people who can afford to head up an 8000 metre peak, and therefore need to take some more radical steps to stay fit and healthy.
One of the most popular aids to acclimatisation is aspirin, whilst it has helped improve physical performance, and reduce altitude related headaches. Test has not shown it actually help you physiological, in that it doesn’t have an effect on blood oxygen saturation levels. Another simple and key thing to remember is that when first at altitude the body tries to compensate for the lack of oxygen by getting causing you to urinate a lot, so remember to counteract that by taking on as much water as you are losing from exercise and excretion.
The one drug that can help us acclimatise quicker is Diamox, this drug has been tested in a series of trails and has shown that it has a very real physiological effect on the body, by increasing the blood oxygen saturation level significantly in a 24 hour period at 3500 metres. It also has been shown to reduce the occurrence of sleep apnoea. It does have some side effects, and it needs to be prescribe by a doctor.
For most people travelling to most altitudes the use of proper hydration and time to acclimatise, a little aspirin to take the edge of a headache will be enough. If you were heading out for a quick route in the Alps, then it might be advantageous to look at taking Diamox to aid your acclimatisation.
At extreme altitudes that are found on the world highest peaks, there is a growing trend to use what were previously treatments for both pulmonary and cerebral oedema caused by altitude (HACE & HAPE), as preventative treatments. This was discovered in several tests that took a population of people with clinically diagnosed cases of HAPE, and then sending them up a cable car to 4500 meters. Half the group would take a placebo the other the drug for testing.
The results showed that both Nifedipine and Dexamethazone drastically reduce the participants having to be evacuated with pulmonary oedema. As such many climbers on Everest now take a heady concoction of Diamox, Nifedipine, Dexamethazone and supplemental oxygen.
Supplemental Oxygen has an very rapid and beneficial effect on the body, as little as two litres a minute of flow rate will effectively mean the equivalent descent of 1500 metre at about 6000m. Making it a very effective and essential treatment for AMS, HAPE and HACE, as well as virtually essential for ascents of the highest peaks like Everest.
As such I argued that there had been very few true ascents of Everest, as most summiteers will have taken one or other of the medical aids to altitude. After I gave that lecture, someone emailed me saying that Halaber and Messner had only taken sleeping pills and aspirin on there ascent. Which is as close as anyone has got to a ‘clean ascent’, although it should be noted that ‘sleeping pills’ have an adverse effect on acclimatisation as it suppresses the respiration.
One thing that I have found interesting from this research is that nowhere can I find a reference to using EPO as a acclimatisation aid. As if a climber was to take EPO before they headed to altitude, would they in essence pre-loaded there body with the higher levels of red blood cells that normally take a week to ten days to develop naturally? Of course I am no doctor, but whether this would be better or safer than using Diamox I don’t know, in fact I am not sure anyone does?
It also brings up a debate of ethics, what is acceptable for the average joe, going to the Alps, versus someone trying to put up new and exciting super alpine routes or ascend the world highest peaks. All of these medical aids to acclimatisation are arguably a form of cheating. However when does staying healthy and/or alive become unethical? I guess that is a question each individual needs to ask themselves, what is the level you are willing to reach alone and with enhancement.
Anyway, the above is just a basic guide to acclimatisation and altitude. I hope at the very least you found it interesting. If you are going to altitude I would advise that you look into asking your doctor or alternatively contact the BMC who have medical advice for mountaineers a link can be found on this interesting news item on Kilimanjaro.