Hiking at Altitude

Hiking or trekking at altitude is not for the feint hearted, and certainly not for the unfit or unprepared either! When you consider that the highest mountains in the UK are Ben Nevis at 1,344 metres, Snowdon at 1,085 metres and Scafell Pike at 978 metres, to jump to Machu Picchu at 2,430 metres would be absolute madness without any build up preparation or training, and that’s for fit people. I recollect recently a Jeremy Vine show on BBC Radio 2 where one of the topics was ‘Altitude Sickness’.  Some very sad cases were related, from which we should all learn!

Have you ever wondered what happens to you, or an aircraft when you are flying in it? When the aircraft is sat on the ground, you’re snugly strapped in as you await take off to your holiday or business destination, the inside of the aircraft is at normal atmospheric pressure, which in this case for arguments sake is roughly the same as sea level. If the aircraft took off and climbed to it’s cruising altitude without nothing being done about the rise in altitude, everyone on board would have become unconscious and have died due to the lack of Oxygen contained in the ‘Rarefied Air’.  Essentially then, as the aircraft takes off and climbs, something has to be done to counteract this rarefied air, so the aircraft is pressurised. Now, although aircraft fuselages are strong, they could not stand the stresses if we tried to pressurise it to the same as at sea level when it is say at a cruising altitude of 34,000 feet, it would simply explode. No, aircraft cabins are normally pressurised to approximately the same pressure found at around 8,000 feet above sea level (2,460  metres), where there is still enough Oxygen contained in the air to support normal activity ‘At Rest’.

Altitude Sickness, are the effects the body starts to feel as the body is exposed to an atmosphere where the Oxygen levels are becoming less and less, this can be flying in an unpressurised aircraft that is climbing to a high altitude, or someone akin to a mountain climber attempting the peak of Everest. Everest is approximately 28,756 feet (8,848m), which is way above 8,000 feet and mountain climbers are certainly not ‘At Rest’, hence they must carry and use additional Oxygen. The signs and symptoms of Altitude Sickness below are from the Wikipedia site. Please follow the link for expanded explanation.


The rate of ascent, altitude attained, amount of physical activity at high altitude, as well as individual susceptibility, are contributing factors to the onset and severity of high-altitude illness. Altitude sickness usually occurs following a rapid ascent and can usually be prevented by ascending slowly. In most of these cases, the symptoms are temporary and usually abate as altitude acclimatisation occurs. However, in extreme cases, altitude sickness can be fatal.


  • High altitude: 1,500 to 3,500 metres (4,900 to 11,500 ft) (Machu Picchu falls into this category)
  • Very high altitude: 3,500 to 5,500 metres (11,500 to 18,000 ft)
  • Extreme altitude: above 5,500 metres (18,000 ft)

Signs and symptoms.

People have different susceptibilities to altitude sickness; for some otherwise healthy people, acute altitude sickness can begin to appear at around 2000 meters (6,500 ft) above sea level. (This is below the altitude of Mach Picchu)

Headaches are the primary symptom used to diagnose altitude sickness, although a headache is also a symptom of dehydration. A headache occurring at an altitude above 2,400 metres (8,000 ft) combined with any one or more of the following symptoms, may indicate altitude sickness:

  • Lack of appetite, nausea, or vomiting
  • Fatigue or weakness
  • Dizziness or lightheadedness
  • Insomnia
  • Pins and needles
  • Shortness of breath upon exertion
  • Nosebleed
  • Persistent rapid pulse
  • Drowsiness
  • Excessive flatulation
  • General malaise
  • Peripheral oedema (swelling of hands, feet, and face)

Symptoms that may indicate life-threatening altitude sickness include:

Pulmonary Edema (fluid in the lungs)
  • Symptoms similar to bronchitis
  • Persistent dry cough
  • Fever
  • Shortness of breath even when resting
Cerebral Edema (swelling of the brain)
  • Headache that does not respond to analgesics
  • Unsteady gait
  • Gradual loss of consciousness
  • Increased nausea
  • Retinal hemorrhage

The most serious symptoms of altitude sickness arise from edema (fluid accumulation in the tissues of the body). At very high altitude, humans can get either high altitude pulmonary edema (HAPE), or high altitude cerebral edema (HACE). The physiological cause of altitude-induced edema is not conclusively established. It is currently believed, however, that HACE is caused by local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressures. On the other hand, HAPE may be due to general vasoconstriction in the pulmonary circulation (normally a response to regional ventilation-perfusion mismatches) which, with constant or increased cardiac output, also leads to increases in capillary pressures. For those suffering HACE, dexamethasone may provide temporary relief from symptoms in order to keep descending under their own power. (Remember the film ‘Vertical Limit’)

HAPE can progress rapidly and is often fatal. Symptoms include fatigue, severe dyspnea at rest, and cough that is initially dry but may progress to produce pink, frothy sputum. Descent to lower altitudes alleviates the symptoms of HAPE.

HACE is a life threatening condition that can lead to coma or death. Symptoms include headache, fatigue, visual impairment, bladder dysfunction, bowel dysfunction, loss of coordination, paralysis on one side of the body, and confusion. Descent to lower altitudes may save those afflicted with HACE.

So, we must remember, especially as we get older or have had sedentary type jobs all of our working life, that the holiday of a lifetime should be that and not end with unfortunate suddenness or sadness that could be avoided. Plan your trip well in advance, work on your fitness levels and do some trekking to altitude as a warm up to build up the bodies acceptance to changes in altitude more readily. Ben Nevis might be a good training ground, but after all it’s still over 3,250 feet lower than somewhere like Machu Picchu. If you start to suffer any of the signs or symptoms, go and see a Doctor just to be on the safe side.

Be safe, enjoy and do come back to relate your trip of a ‘Lifetime‘.