Last year, I trekked up Kilimanjaro in Tanzania - Africa's highest mountain and the world's highest 'free-standing' mountain - as the expedition doctor for Charity Challenge.
After six days of trekking the Rongai route from the north, we climbed the last 1,200 metres at night, when the loose scree is frozen, and arrived at Uhuru Peak at dawn.
From among the glaciers clustered around the crater, we saw a magnificent sunrise.
It was a test of stamina and will power. You trek for six to eight hours a day, but on some days for up to 15 hours. It is not a free holiday. You are there as the doctor, under contract and with a job to do. You have to be pretty fit to manage the trek yourself. You must be a good communicator and support the mountain leader who is in charge.
It is a partnership and, with the guides and porters, it is very much a team effort.
A lot of the medicine is very general, dealing with blisters, strained muscles, headaches, gastroenteritis, sore throats and coughs, so a GP will feel at home with this.
I held a small surgery at my tent after each day's trekking, but I made it known that I was happy to be consulted at any time of day. As the doctor, you walk at the tail end of the extended column, with a porter to carry your medical kit. Clients with problems can then drop back to consult you.
This means your personal ascent rate is slow, which is excellent for your own acclimatisation to altitude, and you have lots of time to stop and take photographs.
There is a limited supply of drugs and you must be able to improvise. For instance, co-codamol can be used as a pain killer, but also to help diarrhoea or a troublesome cough.
Understanding the basics of altitude medicine is vital. As a minor study, I have taken a haemoglobin oxygen saturation meter on each trip and the climbers measured their haemoglobin saturation as they ascend.
I produced similar composite curves for both Everest base camp and Kilimanjaro, showing decreasing haemoglobin saturation with increasing altitude.
Altitude sickness only sets in above 2,500m. Above this, you should only climb 300-500m/day and for every 1,000m increase in altitude, you should have an acclimatisation day, where you stay at the same camp for two nights - 'climb high and sleep low' during this time to aid acclimatisation. The main treatment for altitude sickness is descent, dependent on severity.
Acute mountain sickness (AMS, mild cerebral hypoxia) is common and patients have headache, nausea and anorexia. Analgesics and antiemetics, and perhaps acetazolamide to aid acclimatisation are needed.
Perhaps 30 per cent of the climbers had this mildly at times. For a few, when it failed to settle while camped overnight, it meant they could go no higher. You have to make the occasional tough decision.
Risk of AMS depends on the rate of ascent and individual susceptibility.
HACE and HAPE
More serious is high-altitude cerebral oedema (HACE) - increased microvascular permeability and the cerebral vessels dilate in response to hypoxia, resulting in confusion and ataxia.
This is life threatening for 1-2 per cent. It is managed with dexamethasone, oxygen and immediate descent.
In high-altitude pulmonary oedema (HAPE) the pulmonary vessels do the opposite, they vasoconstrict in response to hypoxia coupled with increased microvascular permeability. The lungs fill up with fluid, the patient is breathless at rest, cyanosed, and produces frothy blood-stained sputum.
Vasodilator plus oxygen
The treatment is a vasodilator plus oxygen, and immediate descent. Nifedipine is the standard but impotence drugs also work.
I treated mild HACE in a guide who drank half a can of lager at high altitude. He became very confused and ataxic and had to be carried off the mountain.
I have also treated two cases of mild HAPE - you need to carry a lightweight stethoscope.
I have built up experience and grown more confident, but I am not complacent. Mountains require respect and mountain sickness needs to be taken seriously.
Probably my greatest test has been to treat severe hypothermia (core temperature 29oC) in an Australian who descended at night in rain from Ama Dablam in Nepal and then collapsed in a warm shower.
We warmed him slowly with warm hot water bottles in his groins and axillae, wrapped him up, gave him oxygen, glucose drinks, steroids, furosemide and acetazolamide. By morning he was fine.
Many experiences are compressed into a 12-day trek.
- Dr Johnson is a GP in Brecon, Wales
Doctors who would like to participate in a similar challenge must be fully qualified. As such, they will be part of a large crew providing support for all the participants on a top quality challenge, such as the Kilimanjaro summit climb. Experience of an outdoor adventure pursuit is an advantage.
You are expected to: