Before Reinhard Messner and Peter Habeler's first successful attempt at climbing Mount Everest, it was commonly believed that survival at this extreme altitude was impossible without supplemental oxygen.
I remember the excitement among us medical students when Peter Habeler was invited to give a lecture about their "Gipfelsieg" (mountain conquest) at our physiology class.
While high-altitude trekking is a popular tourism activity, participants often spend months preparing for their journey by increasing aerobic fitness, doing resistance training and building up strength and lung capacity.
Employees who are sent to work in high-altitude environments do not always have the same amount of time to prepare. Some don't give it any thought. But long-term exposure to high altitude and the associated medical risks need special consideration.
In Papua New Guinea, areas of high altitude include the mountainous eastern and western highlands provinces. Mount Hagen stands at 1722m while Mt Karoma reaches 3623m. Parts of the Kokoda mountain range are over 2000m elevation.
Symptoms of altitude sickness
Altitude sickness, or acute mountain sickness, may occur at an altitude as low as 2000m and is caused by a lack of oxygen to the body. Oxygen is essential for human life and air usually contains 21% oxygen.
However, it is not the portion of oxygen in air that is important but the number of oxygen molecules per volume of air. This again is influenced by ambient air pressure (barometric pressure). Ambient pressure changes with altitude. The higher the altitude the lower is the barometric pressure, so air at high altitude contains less oxygen and hence less oxygen is available to the body. Air at 4000m contains 40% less oxygen than air at sea level barometric pressure. Therefore a sudden exposure to this low concentration of oxygen causes loss of conciousnesss within seconds in un-adapted humans. This is why oxygen masks must be available immediately in instances of a sudden cabin pressure drop in airplanes flying at high altitudes.
The human body can adapt to mild-moderate low levels of oxygen by increasing red blood cells and oxygen-carrying molecules. In addition there is an increase in the rate and depth of breathing. This contributes to the enhanced exercise tolerance, which is beneficial to survival at high altitude and is how athletes prepare themselves for competition, especially for endurance sports.
People have different susceptibilities to altitude sickness. Mild symptoms of altitude sickness range from impaired night vision to shortness of breath, severe headache, gastrointestinal disturbances, dizziness, vomiting, pins and needles, swelling of the hands and feet, and insomia. These symptoms are not uncommon and can be observed in up to 40% of people exposed rapidly to this range of altitude.
Symptoms often occur about 6-10 hours after ascent and generally subside in one to two days but occasionally develop into more serious conditions.
At higher altitudes (above 3500m) more severe symptoms may occur involving the brain and lungs.
Swelling of the brain (cerebral oedema) and accumulation of fluid in the lung (pulmonary oedema) are increasing in frequency as more people spend extended time at altitude. In remote environments, the lung impairment caused by pulmonary oedema and an elevated blood pressure can be life threatening.
Retinal haemorrhage can also develop at very high altitudes.
Adaptation is important for people to cope with low levels of ambient oxygen even if they will be at altitude for a short time. All age groups may be affected and risk is increased in people with a history of altitude sickness.
Risk factors for developing altitude-associated diseases include pre-existing heart and lung diseases, heavy exertion on arrival, low altitude residence before ascent and obesity. Cardiovascular exercise testing is advised for people at risk of heart or lung disease prior to deployment.
Prescription drugs can help prevent symptoms but should be arranged by the individual's regular GP in consideration of their full medical history.
Mining operations conducted at high altitude require special attention because of the long-term exposure of workers. Over time, red blood cells increase excessively and a high blood pressure in the lung vessels causes chronic diseases of the cardiovascular system.
Avoiding alcohol consumption which causes dehydration and strenuous activity in the first 24 hours at high altitude reduces altitude sickness symptoms. Altitude-induced swelling of the brain or fluid on the lungs are acute medical emergencies and a delayed or inappropriate response can result in death. If symptoms occur, the patient should be transported immediately to lower ground. In hostile or remote locations, or places with severe weather conditions, it is not always possible and several medications are available to gain valuable time. The patient must receive supplemental oxygen or should be placed in a portable hyperbaric chamber until a descent can occur.
In the mining sector, pre-deployment health checks and screening of workers, allowing time to acclimatise and ongoing health surveillance is important to prevent excessive workforce losses due to altitude-related diseases. Workers should be educated about the symptoms and know how to recognise early signs of altitude sickness.
Emergency plans should be in place for treating or evacuating people who develop altitude sickness, along with suitable medical equipment at a central, attainable location. Careful diagnosis is important because of the possibility of other diseases with similar symptoms which require a distinct and different therapeutic approach.
A 48-year-old structural engineer was sent to the PNG highlands for his first four-week rotation. He flies from his hometown, Auckland in New Zealand to Port Moresby, spends one night there and then flies with a charter helicopter to the minesite the next day. After reaching the site - at an elevation of 2700m - Joe gets to work. Six hours after reaching the site he starts feeling a bit queasy. Initially he does not make much of it, thinking it must have been something he ate in Port Moresby.
Later however, he starts getting a headache that he describes as "splitting" in nature. He also feels rather weak and decides to lie down but his headache just increases in intensity and he starts vomiting.
One of his colleagues notices that Joe is not well and takes him to the site medic. The medic does a few basic investigations to rule out diseases like malaria (an important differential to altitude sickness in the tropics) and after discussion with a doctor, diagnoses acute altitude sickness.Joe is given two litres of intravenous fluid, some ibuprofen and an antiemetic. He is flown back to Port Moresby where he makes an uneventful recovery within a day and a few days later is able to go to a different site at a lower altitude to begin acclimatising.
Haisjackl holds degrees in public health and medicine, specialising in anaesthesia and intensive care with a focus on lung function. He grew up in the Austrian Alps, where his passion for outdoor activities in mountainous areas led to his interest in associated medical issues.