For most of us, the mountains are a source of health and wellbeing. The combination of clean mountain air, physical exercise and mental decluttering makes for healthy living.
It’s when we start pushing our bodies, our capabilities and altitude, that the pendulum swings. Clean mountain air becomes bitterly cold wind that sucks warmth and life from you, physical exercise mutates into exertion so intense that your body gives up, and the mind declutters to the point that you throw out every morsel of non-essential thought so as to focus solely on survival.
The body is a remarkable thing, an intelligent system capable of extraordinary feats of endurance in the face of disquieting odds. Mountains know no such adversity and instead inflict it.
Here’s how altitude works on the body:
“A climber on the upper slopes of Everest is like a sick man climbing in a dream.”
Accurate words from Eric Shipton on the Everest expedition of 1938 paint a picture of the dulled cognition and acute mountain sickness experienced by mountaineers.
These are signs that the body and brain are struggling to cope with the thin air, all whilst exerting oneself to climb higher into it.
Cells need oxygen in order to respire effectively, helping to convert what we eat into useful energy that sustains us. As we go higher, there are fewer molecules of oxygen in the air. Therefore fewer red blood cells carry oxygen to areas that need it.
Your body adapts to make up for this shortfall, but only to a point. Rate of breathing increases, blood vessels dilate in certain areas to provide them with more oxygen, and more red blood cells are made. However some adaptations can be a double-edged sword and give rise to the symptoms described here.
The Respiratory System at Altitude
To cope with the thinner air at altitude, we simply suck more of it in. Normal breaths aren’t taking in enough oxygen, so control centres within your brain increase the rate of breathing.
We ordinarily breathe through our noses. Here layered folds of tissue within the nose do a great job at heating and humidifying the cold, dry air so as not to damage cells within the respiratory tract.
Breathing faster at altitude, much like during exercise at sea level, means that we all become mouth breathers – inhaling frigid air and losing moisture. The delicate cells of your lungs and connected pipework become damaged and dried out, thus contributing to a persistent cough: the “Khumbu Cough” or “high altitude hack”.
An Everest expedition of 1971 saw four members fracture their ribs through intense coughing.
Joe Tasker described the difficulties experienced by himself and his team that are all too familiar to many high altitude mountaineers:
“I could hear [him] long before I could see him, his hacking coughs echoing up […] I imagined his throat raw and bleeding.”
Coughing, of course, can be a sign of infection, another common predicament with the often unsanitary conditions to be found on long expeditions. It can also be the start of a far more severe ailment: pulmonary oedema.
If they could, anyone that has drowned would tell you that liquid isn’t a lung’s best friend. Pulmonary oedema is like slowly drowning internally, as fluid builds up in a region where only air belongs. Once it’s in full swing, you’re unlikely to recover to tell people how nasty it is.
After noticing that your extensive coughing and shortness of breath are worsening, you start to get a gurgling in the chest, pink frothy sputum and a slightly elevated body temperature (not the silver lining it might seem to be on a cold mountain – think more along the lines of a horrible fever).
In low oxygen conditions, the blood vessels in your lungs are constricting. This tightening breaks the barriers between air sacs of the lungs and the surrounding blood vessels, causing leakage of fluid that eventually builds to life-threatening levels. Bummer.
The Brain At Altitude
Your brain likes blood, particularly the oxygen in it. Despite making up a mere 2% of bodyweight, it greedily consumes its unfair share of blood: some 20% of it. It’s no wonder that when oxygen becomes hard to come by, the brain suffers.
First is the headache. As your body pumps more blood to the brain to meet oxygen demands, its blood engorged expansion is stymied by a suitably tight fitting skull.
If your brain’s appetite for oxygen continues to go unsated, dizziness, nausea and confusion set in. Climbers often report time moving very strangely. American mountaineer Conrad Anker remarked that:
“At altitude, it’s as if there’s a house burning, and the house that’s burning is you, but everything’s happening at such a dragged-out pace you can’t do anything about it. You just watch the house burn down.”
Soon enough you start handing Kendal mint cake to imaginary climbing partners, now the deleterious end-game has begun – cerebral oedema.
Put simply, this is an accumulation of fluid in or on the brain. Symptoms are self-evident for any compression of the brain by stuff that shouldn’t be there – nausea, confusion, dizziness, seizures, psychosis, disturbed vision and finally death (the ultimate “symptom”).
Like in pulmonary oedema, fluid in your blood leaks into places it shouldn’t. Blood vessel expansion puts stress on the barrier between blood and brain tissue, and leakage ensues. Cells within the brain also take on more fluid than they can pump back out. Ultimately this swelling gives you the worst and last headache you’ll ever have.
Further Reading
A succinct, but more detailed overview of high altitude cerebral oedema (HACE) that what I have been able to mention here:
- Jensen JD, Vincent AL. Altitude Illness, Cerebral Syndromes, High Altitude Cerebral Edema (HACE) [Updated 2017 Oct 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430916/
For an in-depth review of the pathophysiology of high altitude pulmonary oedema (HAPE):
- Paralikar, S. J. (2012). High altitude pulmonary edema-clinical features, pathophysiology, prevention and treatment. Indian Journal of Occupational and Environmental Medicine, 16(2), 59–62. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3617508/
Hallucinations, psychosis and “third man syndrome” at high altitude are being studied more. It is thought that it can happen with or without high altitude cerebral oedema. Though like much unusual mental phenomena, its mechanism is largely unknown. This is an expanding and very interesting area of study:
- Hüfner, K et al. (2017). Isolated psychosis during exposure to very high and extreme altitude – characterisation of a new medical entity. Psychological Medicine, 1-8. https://www.cambridge.org/core/journals/psychological-medicine/article/isolated-psychosis-during-exposure-to-very-high-and-extreme-altitude-characterisation-of-a-new-medical-entity/C2BCDEDCB0C6415B16531008857D730C/core-reader
The simple cough is far more complicated than you may think, with entire journals dedicated to its study. The mechanisms I have outlined here are only part of the story, the long held “dry air theory” that is being questioned:
- Mason, Nicholas P. “Altitude-Related Cough.” Cough (London, England) 9 (2013): 23. PMC. Web. 18 Apr. 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176487/
An account of great suffering and hardship, attempting to climb Everest via the notorious West Ridge in winter without supplementary oxygen:
- Tasker J. Everest the Cruel Way. London: Eyre Methuen Ltd; 1981.
London Outdoorsman 