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Updated 23 May 2013

Altitude can be a killer

Climbers and extreme adventurers test the limits of human endurance, but less intrepid trekkers often face the same forces of nature. We asked an expedition doctor for some tips.

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When Dr Charlotte Noble's six-year-old, Clea, is asked where she was born, she points to a spot on the garden path of her family’s home in Scarborough, Cape Town.

At 3am in the morning before Clea's birth, Charlotte wasn't feeling too good. She decided to remedy this as usual – by going for a run. She’d only gone about 5km when it became clear that Clea was on the way, but, when you're giving birth, says Charlotte, "5km can take forever". She made it back home (as far as the garden path anyway), before Clea made her appearance.

This anecdote is not a particularly stand-out one in Charlotte’s life. The more one talks to her, the more these kinds of stories are revealed: of athletes and adventurers for whom pushing themselves to extremes is par for the course.

This unassuming, quietly-spoken GP, marathon runner, surfer and not least parent (with renowned climber Andy de Klerk) to four lively kids under seven, is familiar with conditions where the human body is tested to the limits of endurance. She has worked as team doctor on various expeditions, including the controversial first South African Everest attempt, and an exploratory National Geographic climbing trip with John Krakauer (author of Into the Wild) in Antarctica.

The health risks on such trips are of a different order of magnitude to those faced by the average outdoor enthusiast. But Nature can turn on any of us who venture into her territory, especially when we’re less fit and well-equipped than we think, and haven’t done our wilderness homework.

We asked Charlotte about some of the lessons learned as an expedition medic – specifically, the strange things that happen to human physiology when it heads for the very high hills.

High, hostile places
As if scaling the topmost peaks isn’t difficult enough in terms of sheer exertion, it is done in a beautiful but hostile environment of bitter cold, gaspingly thin air, and alternately searing sunlight and wild storms. Mountains are not forgiving of human error and vulnerability.

An expedition doctor, says Charlotte, needs to be up to the physical and psychological rigors of the job. You must be able to keep up with your potential patients, and many doctors are climbers or trained in other adventure and endurance sports themselves.

And of course, you must also be well-versed in the medical conditions you're likely to encounter. Charlotte explains that expedition doctors need emergency room-type skills, to deal with acute crises such as trauma from falls.

Falling, however, is only one risk of high-altitude climbing. Climbers are also at risk for hypothermia, frostbite, and, ironically in these snow-and-ice environments, sunburn, snow-blindness and dehydration.

But they are also beset by the problems that come with simply being way, way up high.

Normal acclimatisation
There’s a reason mountains are one of the last outposts of solitude on the crowded planet: the human body doesn’t like it up there. It prefers to be beside the seaside, where temperatures tend toward the moderate and the air is “thick” with oxygen molecules.

The body may get a little less happy when it’s been hanging out at 0m altitude on a Cape Town beach, and is then rudely whisked off to Joburg (1750m), for example, but it generally manages fine with this sort of modest increase in elevation.

As you ascend above about 2000m however, you’ll start to notice some changes. This is your body acclimatising – adapting to the lower levels of oxygen in the air – a process that takes days or even weeks.

The following symptoms are considered normal in otherwise healthy people, and don't constitute altitude sickness: faster and deeper breathing; shortness of breath when exercising; changed breathing patterns at night; frequent waking at night; increased urination.

Altitude sickness
Altitude sickness (or acute mountain sickness, AMS for short) is the well-known malaise that waits for us in high places. It should always be taken seriously, because (apart from ruining your holiday) its severe forms are deadly.

There’s no certain way to know who’s going to get AMS, and physical fitness is no protection. The mechanism of altitude sickness also remains somewhat mysterious, but it is related to the decrease in air pressure and oxygen levels that accompanies increased altitude. Symptoms appear to be primarily caused by fluid leaking from blood vessels as a result of air pressure differentials.

Typical symptoms include headache, appetite loss, nausea or vomiting, fatigue, dizziness, trouble sleeping. But the rule to follow is that if you’ve recently ascended to high altitude, you feel unwell and there is no other obvious cause, then always assume it’s AMS.

NB: Don’t ascend further until you feel quite well. If symptoms get worse, descend as soon as possible.

AMS starts to become a risk above about 2400m, although some people are susceptible lower down, especially when arriving at high altitude straight from sea level. Risk increases with exertion and elevation, but you certainly don’t need to be summiting Everest to get it.

It’s not unknown, says Charlotte, for climbers flying in to the village of Namche Bazaar (a stopover en route to Everest base camp), at a relatively modest 3500m altitude, to collapse in their hotel rooms.

To get an idea of relative altitudes:

Table Mountain: 1000m
Johannesburg: 1750m
Highest Drakensberg peaks: 3500m
Namche Bazaar: 3500m
Everest base camp: 5000m
Death zone: altitude above which oxygen is too low to support life: 7000 - 8000 m
Summit of Everest: 8 848 metres

AMS is not a concern within South Africa, which only reaches 3500m at its highest peaks, but it should be for several other African outdoor destinations – like Mount Kenya (5 199m) and Mount Kilimanjaro (5 985m), both of which have routes that allow hikers to rapidly ascend to potentially dangerous altitudes.

Altitude sickness should also be a consideration if you’re flying abroad to high altitude destinations such as ski resorts. And keep in mind that high places aren’t necessarily mountains, as such. One notorious altitude sickness destination (to which the author can attest) is La Paz, Bolivia: the highest capital city in the world, it ranges in altitude from 3100m to over 4000m at the airport. Other examples are Lhasa, Tibet (3658m) and Cuzco, Peru (3399m).

Preventing and treating altitude sickness
Be patient with your body and allow it enough time to acclimatise. Avoid travelling straight from low altitude to high: break the journey at an intermediary level. There's no hard-and-fast rule as regards this, because each person acclimatises differently, but the following recommendations from the International Association of Mountain Medicine are useful to follow:

  • Spend at least one night at an intermediate altitude below 3000m.
  • At altitudes above 3000m, don’t increase your sleeping elevation more than 300-500m per night.
  • Every 1000m, spend a second night at the same elevation.
  • "Climb high, sleep low". On “rest days” (when you’re spending a second night at the same altitude), you can do short day-hikes to higher elevations: these help you acclimatise. But be sure to return to a lower elevation to sleep.

Symptoms of AMS take some hours to manifest, so just because you’re feeling fine on arrival doesn’t mean you should rush off and tackle the Bolivian Andes (as I tried to do soon after arrival in La Paz, with dismal results). Rest up for a few days, and take in plenty of fluids.

It's best to avoid alcohol, sleeping pills and narcotic pain medications, as these can worsen breathing abnormalities at altitude.

If you’re heading for a high altitude destination, ask your doctor if acetazolamide (Diamox) would be appropriate: this medication can both help prevent symptoms and aid recovery if they develop. It's important to remember, though, that even if you're taking Diamox, you still need to allow yourself to acclimatise.

Also let your doctor know if you are diabetic or have a heart or lung condition, as this might put you at risk for additional complications at altitude.

When altitude kills
Altitude sickness usually resolves after a couple of days, but it can progress to two deadly conditions: HACE (high altitude cerebral edema), fluid build-up in the brain; and HAPE (high altitude pulmonary edema), fluid in the lungs.

When someone has HACE, they may have symptoms of AMS, and typically also become confused and unco-ordinated.

"Cerebral edema can develop very quickly, and lack of co-ordination is typical: they'll stagger, or won't be able to tie their shoelaces properly. Then they'll gradually lose consciousness," says Charlotte, who recalls the death of a female sherpa from HACE when she was on Everest in 1996. "The sherpas, and similarly Andean peoples, are genetically adapted to high altitutude conditions, but even so, they are also vulnerable."

Symptoms of HAPE may look like a chest infection. On a trip to the Peruvian Andes, one of Charlotte’s team had what seemed to be bronchitis, which she treated with antibiotics. But deep in the night, it became clear that he was getting worse and his chest was filling up with fluid.

“Pulmonary edema is often more insidious than cerebral. It also tends not to improve if someone who’s had it returns after recovering; generally, if you’ve had it once it tends to mean that you can’t do high altitude."

"In these extreme cases, you need to get the person down urgently, or they will die," says Charlotte. High-altitude medical equipment often includes a Gamow or hyperbaric bag: if rapid descent is not possible, then the patient is placed inside the bag, which is pumped up to simulate the higher air pressure of lower altitudes. HACE and HAPE are also treated with drugs and oxygen.

- Olivia Rose-Innes, EnviroHealth Editor, Health24, updated August 2011

Read more:

Altitude sickness
Altitude training - the basics

Additional Sources:
Centers for Disease Control. Altitude Sickness
International Society for Mountain Medicine. An Altitude Tutorial

 
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