HIGH ALTITUDE DISEASES An Overview of Illnesses at High Altitude
HIGH ALTITUDE DISEASES © Tómas Guðbjartsson 2022 Illustrations: Árni Árnason Layout: Björg, bjorgvilhjalms.is Translation to English: xxxxxxxxxxxxxx This book may not be reproduced by any means, such as by photography, printing, recording or by any similar means, in part or in whole, without the prior written consent of the author and publisher. Reykjavík 2022
HIGH ALTITUDE DISEASES AN OVERVIEW OF ILLNESSES AT HIGH ALTITUDE
TÓMAS GUÐBJARTSSON
TABLE OF CONTENTS ABOUT THE AUTHORS .................................................................6 INTRODUCTION .........................................................................7 MOST COMMON HIGH ALTITUDE DISEASES ........................................8 WHERE ARE YOU MOST LIKELY TO DEVELOP HIGH ALTITUDE ILLNESS? ... 10 The fourteen highest mountains in the world .............................................. 12 The highest cities in the world ..................................................................... 12 Other cities and towns at high altitude ........................................................ 12 The ten highest ski resorts in the world ...................................................... 13 NORMAL ACCLIMATISATION ......................................................... 14 Mount Everest conquered without supplemental oxygen ........................... 15 ACUTE MOUNTAIN SICKNESS ........................................................ 17 Principal signs and symptoms ..................................................................... 18 HIGH-ALTITUDE PULMONARY EDEMA ..............................................20 HIGH-ALTITUDE CEREBRAL EDEMA ................................................ 21 WHAT EFFECTS HAS HIGH ALTITUDE ILLNESS ON YOUR BODY?..............22 Acute mountain sickness and high-altitude cerebral edema .......................22 High-altitude pulmonary edema ...................................................................23 WHO DEVELOP HIGH ALTITUDE ILLNESS? .........................................23 HOW HIGH ALTITUDE ILLNESS CAN BE PREVENTED .............................26 Acute mountain sickness and high-altitude cerebral edema .......................26
General recommendations . . . . . . . . . . . . . . . . . . .
26
Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
What kind of medicine is acetazolamide?. . . . . .
28
HIGH-ALTITUDE PULMONARY EDEMA . . . . . . . . . . . . . . . . . . .
29
TREATMENT OF ACUTE MOUNTAIN SICKNESS . . . . . . . . . . . . . . . . . .
30
General recommendations . . . . . . . . . . . . . . . . . . .
30
Medicines and other treatments for acute mountain sickness . . . . . . . . . .
30
Treatment of high-altitude pulmonary edema. . . . . . . . . . . . . . . . . .
31
Treatment of high-altitude cerebral edema. . . . . . . .
31
OTHER HIGH ALTITUDE DISEASES . . . . . . . . . . . . . . . . . . .
33
Sleep disturbance . . . . . . . . . . . . . . . . . . . . . . .
33
Altitude-related cough
33
.. . . . . . . . . . . . . . . . .
Gastrointestinal problems . . . . . . . . . . . . . . . . . . . 34 Eye disorders . . . . . . . . . . . . . . . . . . . . . . . .
36
Frostbite . . . . . . . . . . . . . . . . . . . . . . . . . . .
36
Factors contributing to high altitude illness . . . . . . . . . . . . . .
25
LISTS OF MEDICINES . . . . . . . . . . . . . . . . . . . . . . . .
36
Mountain expedition to an altitude of 2500–6000m . . . . . . . . . . . . . .
36
Mountain expedition to an altitude of over 6000m . . . . . . . . . . . . . .
36
ABOUT THE AUTHORS Engilbert Sigurðsson is a professor of psychiatry at the University of Iceland and consultant psychiatrist at Landspitali - The National University Hospital of Iceland. After completing his medical degree, he studied psychiatry and graduated with an MSc in epidemiology from London School of Hygiene & Tropical Medicine. Engilbert is an experienced hiker and mountain skier, both in Iceland and abroad, with ascents that include both Kilimanjaro and Monte Rosa. Gunnar Guðmundsson is a a respiratory physician at Landspitali - The National University Hospital and professor at the University of Iceland’s Faculty of Medicine. He completed his medical degree in Iceland, studied pulmonary and critical care medicine at the University of Iowa, and graduated with a PhD degree from the University of Iceland’s Faculty of Medicine. Gunnar was a member of a search and rescue team in his younger years, and is an experienced mountaineer, both in Iceland and in mainland Europe, Africa, the United States and Nepal. For many years, Gunnar has also advised Icelandic mountaineers in their expeditions to the world’s highest peaks. Magnús Gottfreðsson is a professor of infectious diseases and senior consultant at Landspitali - The National University Hospital. After graduating with a medical degree from the University of Iceland, he moved to North Carolina, where he trained in internal medicine and infectious diseases. Magnús has climbed Mount Kilimanjaro and numerous mountains in Iceland and the Alps in addition to being an experienced mountain and marathon runner. Ólafur Már Björnsson is an ophthalmologist at Sjonlag Eye Center. He trained in ophthalmology in Oslo after completing his medical degree in Iceland. He has trekked to Everest Base Camp, and gone on many mountain ski and hiking expeditions, both in the Alps and in Iceland. He is also an avid photographer. Tómas Guðbjartsson is a professor of surgery and senior consultant at the Department of Cardiothoracic Surgery at Landspitali - The National University Hospital. After completing his medical degree and PhD at the University of Iceland, he trained in general surgery and later cardiothoracic surgery in Lund, Sweden, and Boston, USA. Tómas has climbed Aconcagua, Kilimanjaro, Mont Blanc, Monte Rosa og Mount Rainer in addition to taking part in mountain ski expeditions in Europe and North America. He has also many years of experience as a mountain guide and medical consultant for Icelandic mountaineering expeditions overseas. 6 High Altitude Illness
INTRODUCTION This booklet provides an overview of the most common diseases that may occur at high altitudes; both acute mountain sickness (AMS), which is the most common form of high altitude illness, and life-threatening conditions such as high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE). Acclimatisation, i.e. the body’s natural response to lack of oxygen, is explained in brief, and other common conditions at high altitude, such as sleep disturbance, gastrointestinal problems, snow blindness and frostbite, are also discussed. Treatment of the most common conditions is reviewed, and at the back is a list of medicines that may be helpful to bring along when mountaineering abroad. The authors are five doctors who are all avid outdoorsmen and have taken part in overseas montaineering expeditions. In 2019, the authors published a review on high altitude illness in the Icelandic Medical Journal, and while the present text is partly based on this review, the approach is geared towards general readers as opposed to healthcare professionals. Tables have also been added and all illustrations are new. Graphic designer Björg Vilhjálmsdóttir and illustrator Árni Árnason are responsible for the design of the booklet, which is printed on water-resistant paper and in a size that should fit comfortably into a backpack. Special thanks go out to the Iceland Touring Association, which provided funding for this publication, as well as the the companies 66°North, Fjallakofinn and Everest, who also provided support without imposing any conditions on the authors. Reykjavík, 1 September 2022 On behalf of the authors,
Tómas Guðbjartsson, Editor
High Altitude Diseases 7
MOST COMMON HIGH ALTITUDE DISEASES Those who travel to an altitude of more than 2500 m may experience various disorders associated with thin air, usually within a few days. The risk is mainly determined by the altitude and rate of ascent, and the symptoms may vary greatly and manifest in various organs and organ systems. Before symptoms occur, the body will have responded to the lack of oxygen by initiating an adjustment process called acclimatisation. However, the body's response is not always sufficient, or it may overrespond, in which case high altitude illness may develop. By far its most common form is acute mountain sickness (AMS), but the more dangerous, and potentially lifethreatening, high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE) may also occur. While high altitude illness is caused by lack of oxygen and insufficient acclimatisation, the form it takes is determined by the body’s response. The most common symptoms of AMS include headache, fatigue, weakness, nausea and loss of appetite, but sleep disturbance and gastrointestinal symptoms are also common complaints. The most frequent symptoms of HAPE include severe shortness of breath and lack of energy while HACE is usually characterised by ataxia, confusion and reduced consciousness. Finally, there are conditions associated with high altitude that cannot be traced directly to lack of oxygen, such as frostbite and diarrhoea.
8 High Altitude Diseases
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WHERE ARE YOU MOST LIKELY TO DEVELOP HIGH ALTITUDE SICKNESS? More and more Icelanders are travelling abroad for hiking, skiing, climbing and mountain biking at altitudes exceeding 2500 metres. Destinations include the highest altitude areas in the world, such as the Himalayas, where the 20 highest mountains in the world can be found, the South American Andes, the Rocky Mountains in the United States, and the Alps in Europe. Several major cities also have a high altitude and there is no time for acclimatisation when landing at an airport in such cities. One such city is La Paz in Bolivia, whose elevation above sea level makes it the highest capital city in the world. Many ski resorts are also at a high altitude so it is common to experience symptoms of acute mountain sickness there, especially when disembarking from the highest lifts.
10 High Altitude Diseases
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NORMAL ACCLIMATISATION At sea level, the percentage of oxygen in inhaled air is 21%, the same as it is on the summit of Kilimanjaro (5895 m) and the peak of Mount Everest (8848 m). However, with increased elevation, the atmospheric pressure decreases exponentially, meaning that instead of 760 mm of mercury (equivalent to 1013 millibars or 101.3 kPa) at sea level, the atmospheric pressure is only half of this (50 kPa) on the summit of Kilimanjaro (5895 m) and a third (34 kPa) on Mount Everest, Earth’s highest mountain. The amount of oxygen per volume of atmosphere on the summit of Mount Everest is therefore only a third of the amount per the same volume at sea level. At heights of more than 2500 metres, the effects of reduced oxygen may be felt, and symptoms may occur at lower elevations in individuals with conditions such as cardiovascular disease. To make the most of the available oxygen, your body will begin to acclimatise to the elevation. This is a complex physiological process that begins as soon as you reach a higher elevation, but may take weeks or months to become fully effective. Thus, a person who has not undergone acclimatisation will only survive for half an hour on the summit of Mount Everest, while specially trained mountaineers who have spent six to eight weeks at a high elevation can ascend Earth’s highest peaks with the aid of supplemental oxygen.
14 High Altitude Diseases
Mount Everest conquered without supplemental oxygen On 8 May 1978, Peter Habeler and Reinhold Messner became the first men to reach the summit of the world’s highest mountain, Mount Everest, without the use of supplemental oxygen. The expedition was meticulously planned and is considered one of the greatest mountaineering achievements of all times. Equipment was kept as light as possible, allowing the mountaineers to travel faster on Mount Everest than anyone had done before them. Before their expedition, it was widely believed that it was physiologically impossible to reach the summit without supplemental oxygen, as oxygen levels there are only a third of the levels at sea level. Habeler and Messner proved this wrong, and over two hundred mountaineers have since followed in their footsteps. Reinhold Messner would later become the first person to ascend the 14 highest mountains in the world without the use of supplemental oxygen. Most of the body's organs acclimatise to higher elevation, but the response of the lungs, heart and blood are most important. When blood oxygen levels decrease, the receptors in the arteries that carry oxygen to the brain are stimulated, resulting in an elevated respiratory rate and deeper inhalation, both of which increases gas exchange in the lungs.
High Altitude Diseases 15
The faster and deeper breathing lowers the amount of CO2 in the blood while raising pH levels in the blood. The main symptoms of hyperventilation are numbness in the fingers and around the mouth. Exertion may also result in more shortness of breath than before. Meanwhile, the heart increases its cardiac output by beating faster (a faster pulse) and increasing the contractions of the heart muscle, both of which reduces the time it takes to supply oxygen to tissue such as the brain and muscles. The kidneys gradually join in the response to rising pH levels by increasing the excretion of bicarbonate in the blood (it usually takes the kidneys a few days to fully correct the pH levels). The body also begins to produce more urine, which may exacerbate dehydration. The kidneys start producing more erythropoietin, a hormone that stimulates the synthesis of red blood cells in the bone marrow. Maximum secretion of erythropoietin is reached in two to three weeks, resulting in increased haemoglobin levels. An important part of acclimatisation is that with lower blood oxygen levels it becomes easier for red blood cells to deliver oxygen to tissues. A hormone that stimulates the formation of blood vessels in tissues lacking oxygen is also produced. This increases blood flow and the availability of oxygen to the tissues. Finally, there is a change in the metabolism of mitochondria,
16 High Altitude Diseases
which provide energy for cells, to ensure optimal utilisation of oxygen. To begin with, acclimatisation can keep pace with the reduced oxygen in inhaled air, but at heights of more than 5,000 metres, the rate of oxygen desaturation starts to exceed the rate of acclimatisation. At this point, oxygen saturation begins to decrease at a much faster rate with increased elevation, the effects on the body are greater, and the risk of high altitude illness increases. Withstanding such elevation requires many weeks of acclimatisation, with mountaineers who tackle the summit of Mount Everest, and other mountain peaks with an elevation of more than 8000 metres, often showing hemoglobin levels of around 190 g/L, compared to approximately 140 g/L under normal conditions.
ACUTE MOUNTAIN SICKNESS Acute mountain sickness is a collection of symptoms where headache is the main symptom, but other symptoms are also frequently present. Acute mountain sickness is a very common problem, with research from the Rocky Mountains and the Alps indicating that more than a fifth of those who reach heights of 2,500-2,900 metres experience symptoms, more than 40% of those who reach heights of over 3,000 metres, and close to 60% when heights exceed 5,000 metres.
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Many of these symptoms can also be caused by conditions other than acute mountain sickness. Specific criteria with different weighing of symptoms is therefore used. The most commonly used international criteria are the scoring system named after Lake Louise in Canada.
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This means that while a person with actual acute mountain sickness will always have a headache, they must also have recently ascended to an elevation of more than 2,500 metres, thus not having completed their acclimatisation. One or more of the following symptoms will also be present: gastrointestinal symptoms (loss of appetite, nausea or vomiting), dizziness, weakness and fatigue. Insomnia, on the other hand, is no longer part of the diagnostic criteria for acute mountain sickness, as it has been shown that up to 40% of people with AMS do not have disturbed sleep. Symptoms typically appear 6-10 hours after reaching a great height, but may commence up to one hour after arrival or one to two days later. Barring further ascent, the symptoms usually go away in one to three days.
HIGH-ALTITUDE PULMONARY EDEMA This dangerous disease is much rarer than acute mountain sickness, with a frequency of around 5% at 5,500 metres, and is mostly determined by the rate of ascent. Highaltitude pulmonary edema is considered the most fatal form of high altitude illness for mountaineers. Its symptoms may appear two to four days after ascending to an elevation of more than 3,000 metres. It is caused by fluid retention in the lungs and the first symptoms are dry cough, shortness of breath with activity and lack of energy
20 High Altitude Diseases
when climbing or walking up a slope. The increased retention of fluid in the lungs, and the resulting drop in oxygen saturation, often manifests in increasing shortness of breath when walking on level ground, and even breathing difficulties. Sputum may also become frothy and blood-coloured. It is important to keep in mind that common symptoms of acute mountain sickness, such as headache and nausea, only occur in about half of all cases of imminent high-altitude pulmonary edema, and at its earliest stages, HAPE may be difficult to distinguish from respiratory infections, which are very common at high altitude.
HIGH-ALTITUDE CEREBRAL EDEMA Like high-altitude pulmonary edema, high-altitude cerebral edema is a life-threatening form of high altitude illness. It is believed to be caused by a fluid imbalance in the small vessels of the brain due to insufficient acclimatisation. Symptoms usually do not appear until altitudes of 3,000 metres or more. Unsteadiness when walking is usually the first noticeable symptom while people with more advanced cerebral edema experience balance disorders that may turn rapidly into drowsiness, and even disorientation and reduced consciousness. Risk factors include a history of high altitude illness, insufficient acclimatisation and heavy physical exertion. High-altitude cerebral edema is less common than high-altitude pulmonary edema, with a frequency of 0.5-1% at an altitude of 4,000-5,000 metres. Symptoms of acute mountain sickness, such as headache and nausea, and even symptoms of highaltitude pulmonary edema, usually precede the onset of high-altitude cerebral edema, although high-altitude cerebral edema has been known to develop without such preceding symptoms.
High Altitude Diseases 21
WHAT EFFECTS HAS HIGH ALTITUDE ILLNESS ON YOUR BODY? The pathogenesis of acute mountain sickness is complex, but can be traced to the body’s response to insufficient oxygen levels. The pathogenesis of high-altitude pulmonary edema is slightly different from the pathogenesis of acute mountain sickness and high-altitude cerebral edema, which some consider to be an extreme form of AMS. There is considerable overlap in the main forms of high altitude illness, although high-altitude pulmonary edema may occur without symptoms of acute mountain sickness. Acute mountain sickness and high-altitude cerebral edema There is still much unknown about what triggers the complex trajectory of these diseases, although it seems like those who develop acute mountain sickness typically have lower blood oxygen saturation levels than those who remain asymptomatic. Various factors are thought to be involved, such as insufficient respiratory rate increase when oxygen pressure decreases, reduced gas exchange in the lungs due to edema and abnormal fluid retention in the body, plus other factors. It is clear that lack of oxygen triggers hyperventilation, which lowers carbon dioxide levels in the blood and causes the blood vessels to the brain to dilate. This increases blood flow to the brain, but in severe cases of acute mountain sickness and high-altitude cerebral edema, capillary leakage makes the brain swell with fluid, increasing pressure inside the skull. 22 High Altitude Diseases
High-altitude pulmonary edema In these individuals, lack of oxygen is believed to result in localised pulmonary hypertension which causes increased blood flow to other areas of the lungs, capillary leak and ultimately pulmonary edema.
WHO DEVELOP HIGH ALTITUDE ILLNESS? The biggest risk factor for high altitude illness is rapid ascent at high altitude. A history of high altitude illness is also a known risk factor, especially in the case of high-altitude pulmonary edema, where more than half of individuals with a history of high-altitude pulmonary edema become sick again, with similar symptoms, if they return to the same elevation. The elevation of sleeping spots is also important. There is no difference in frequency of high altitude illness by gender, but age is a factor, as people between 50 and 70 are at a lesser risk of developing acute mountain sickness than those who are younger, while the risk increases again after the age of 70. Overexertion and infections, particularly respiratory infections, are known risk factors for high-altitude pulmonary edema.
High Altitude Diseases 23
High exercise capacity and physical training do not protect against high altitude illness, and there is much to indicate that athletes who compete in endurance sports such as marathons and swimming are no less susceptible than others. Studies of some of the most prominent mountaineers in history, including Reinhold Messner, have furthermore shown that they do not have more exercise capacity than top athletes in various endurance sports. There are many indications that genetics may partly explain differing susceptibility to the disease. Thus, ethnic Tibetans who have lived at high altitudes for centuries are much less susceptible to high altitude illness than Chinese people who have moved to Tibet from the lowlands in the last few decades. The heredity of high altitude illness and the body’s response to lack of oxygen is a complex and still largely unexplained phenomenon. Several genetic variations have been described, with the so-called ACE gene, the angiotensin-converting gene, providing the strongest link.
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Commented [L1]: Ath. flútt
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HOW HIGH ALTITUDE ILLNESS CAN BE PREVENTED Various methods can be used to prevent high altitude illness, both general recommendations and medicines. Below is a special joint discussion of preventing acute mountain sickness and high-altitude cerebral edema, as well as a look at preventive treatment for high-altitude pulmonary edema. ACUTE MOUNTAIN SICKNESS AND HIGH-ALTITUDE CEREBRAL EDEMA General recommendations Here, the golden rule of mountaineering applies: to allow enough time for acclimatisation. This is something that is much too frequently forgotten. You should avoid ascending straight from sea level to an altitude of more than 2,700-3,000 metres. It is best to stay overnight at an average altitude of perhaps 2,500-2,800 metres before continuing the ascent. After this, it is recommended that daily altitude gain does not exceed 500-600 metres between places of sleep, with a day of rest for each 1,000-1,200 metres of altitude gain. The sleeping altitude is often more important than the altitude ascended to during the day, i.e. most acclimatise as they finish their trek of the day with a descent to the place of sleep. You should walk calmly and steadily and not overexert yourself, especially if you have been subjected to high altitude illness before.
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Medicines The medicines most commonly used for the prevention and treatment of high altitude illness can be seen in the table below. All medications must be administered after consultation with a physician. Paracetamol and anti-inflammatory agents such as ibuprofen and celecoxib are effective for high-altitude headaches, but the most commonly used specialised medicine is acetazolamide.
Medicine
Indication
Ingestion
Commented [L2]: Hér virðist vanta ofan á töfluna, s.s. línuna fyrir Dexamethasone
AMS: acute mountain sickness, HACE: high-altitude cerebral edema, HAPE: high-altitude pulmonary edema
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What kind of medicine is acetazolamide (Diamox®) and how effective is it? This medicine, originally developed to treat glaucoma, inhibits renal reabsorption of bicarbonate and sodium, thus increasing the amount of bicarbonate excreted in the urine, which leads to acidification of the blood (metabolic acidosis). To correct the blood pH, the body will respond by increasing oxygen uptake in the lungs. Results on the efficacy of this medicine have varied, but recent studies indicate that it may reduce the rate of acute mountain sickness by as much as half, although users will experience increased tingling in their hands and feet and carbonated beverages, such as soft drinks, will have an unpleasant taste.
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It is up to each individual whether to take acetazolamide, but it is not considered necessary as an altitude illness prevention for all who ascend to great heights, although those who have experienced more than a touch of acute mountain sickness should consider such treatment to reduce the likelihood of developing symptoms of high altitude illness. Those who intend to travel from sea level to a sleep altitude of more than 3,000 metres without allowing for acclimatisation, should consider taking this or other medicine that prevents high altitude illness. You will begin taking acetazolamide 24 hours before ascending and stop when you are back to below 2,500 metres, or if you stay at the same altitude for more than 4–5 days. Those who are allergic to sulfa drugs should avoid acetazolamide due to potential cross sensitivity. To ensure that the medicine is well tolerated, it is often recommended to test it at sea level about two weeks prior to the intended use. Dexamethasone is a glucocorticoid medication that may help to prevent cerebral edema by reducing leakage in brain capillaries. This medicine should only be used as a preventive treatment after consultation with a physician, for instance if acetazolamide is not well tolerated or if its use is contraindicated. Intake of glucocorticoids for more than 10 consecutive days is not recommended due to the risk of adverse reactions, and it is important to keep in mind that symptoms of high altitude illness may recur when treatment is discontinued. Various other medicines have been studied for their potential to prevent high altitude illness, including magnesium citrate and ginkgo biloba, but most studies do not support their efficacy.
HIGH-ALTITUDE PULMONARY EDEMA In general, the preventive guidelines that apply for acute high-mountain sickness also apply for high-altitude pulmonary edema, although it is especially recommended to avoid over-exertion, especially for those who have a respiratory infection. Those who have had high-altitude pulmonary edema before should ascend very carefully and consult a physician before ascending to a high altitude. The use of so-called phosphodiesterase inhibitors, such as tadalafil and sildenafil, which are used primarily for the treatment of erectile dysfunction, is rarely appropriate for preventive purposes, except in isolated cases of patients who have previously suffered from high-altitude pulmonary edema, and then only after consultating a physician.
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TREATMENT OF ACUTE MOUNTAIN SICKNESS General recommendations Most important is to descend to a lower altitude at once, and this must always be done if conditions permit. If symptoms are mild, staying put may be an option. A descent of 500–1,000 metres is often enough to reduce symptoms significantly. After resting and acclimatisation, further ascent may be attempted if the symptoms were mild. Those who have had cerebral or pulmonary edema are advised against attempting to ascend further. It is always recommended to drink plenty of liquids and quench thirst as soon as it arises to avoid dehydration and reduce the effects of acute mountain sickness. Fluid overload should be avoided, however, as it may result in lower blood sodium and acute mountain sickness-like symptoms. Medicines and other treatments for acute mountain sickness Medicines may be used exclusively if symptoms are mild or if conditions do not allow for descent to a lower altitude, for instance due to weather or darkness. Medicines most commonly used for patients with severe symptoms of acute mountain sickness can be seen in the table on page 27. Full doses of painkillers such as paracetamol, ibuprofen or celecoxib may be used for mild symptoms, especially headache. Acetazolamide should be administered as soon as possible after the onset of symptoms while more potent medication, such as dexamethasone, may be used as an alternative, after consultation with a physician. Acetazolamide is mostly used for mild cases of acute mountain sickness. If symptoms subside once medicine 30 High Altitude Diseases
has been administered, descending to a lower altitude may not be necessary. Dexamethasone, on the other hand, is preferred in cases of moderate or severe acute mountain sickness. It is never recommended to ascend to a higher altitude before symptoms have subsided. Administering oxygen nasally reduces symptoms quickly but is rarely available, as oxygen cylinders are cumbersome and heavy. Some cabins have portable hyperbaric (Gamow) bags, in which the patient can be placed and pressure applied with a foot or hand pump, resulting in a decrease in effective altitude of up to 3,000 metres. Treatment of high-altitude pulmonary edema It is especially important in these cases to bring the patient to a lower altitude, but a hyperbaric bag may be useful when transporting the patient is not possible. Administering oxygen, e.g. 1–2 litres/min nasally via a nasal mask, is effective but rarely available at high altitudes. Phosphodiesterase inhibitors, such as tadalafil or sildenafil, can be administered, in consultation with a physician, to decrease pulmonary artery pressure, for which nifedipine tablets can also be used. Diuretics and morphine are not recommended for the treatment of high-altitude pulmonary edema, as diuretics may increase dehydration. How is erectile dysfunction medication effective against high-altitude pulmonary edema? Sildenafil was originally studied as an antihypertensive agent, but did not prove to be sufficiently effective. However, many men did not want to stop taking the drug at the conclusion of clinical trials. That is how its effectiveness as treatment for erectile dysfunction was discovered. These medicines increase the production of nitrous oxide (NO) in the pulmonary arteries, dilating them without having an effect on blood pressure elsewhere in the body. That is why they are used to treat high-altitude pulmonary edema and unexplained pulmonary hypertension. Studies on their efficacy in treating high-altitude pulmonary edema are limited, but nevertheless sufficient to recommend their use.
Treatment of high-altitude cerebral edema Most important is to move the patient further down the mountain, as far far down as conditions allow. This is always the case unless descent is prevented by external conditions. In such circumstances, administering oxygen, if available, may be appropriate, if oxygen is available, and the same applies to hyperbaric bags. Dexamethasone in tablet form is sometimes used, administered intravenously or intramuscularly, if conditions allow. High Altitude Diseases 31
OTHER HIGH ALTITUDE DISEASES Sleep disturbances These are some of the most common altitude-related complaints, and may be caused by various environmental noises that disturb sleep, but also by unfamiliar sleeping conditions, such as sleeping in a tent or a crowded cabin. Lack of oxygen is believed to be the main cause of such sleep disturbances. Symptoms include irregular, periodic breathing, which is common at high altitudes, but can often be treated with acetasolamide. Those who experience severe sleep disturbances despite acetazolamide may take sleeping medicine such as zolpidem, which is less likely to suppress breathing than other sleeping medicine. Altitude-related cough Coughing is common at higher altitudes where the cough reflex is more sensitive. Breathing is also accelerated and the air is dryer, which dries up the respiratory tract and may result in coughing. This especially applies to people with asthma or other respiratory diseases. In addition, mountain air is often very dusty, and bacterial and viral infections are easily transmitted in cramped spaces such as tents. Rest and descending to a lower altitude is effective in alleviating the problem, but medicines with codeine can also be used to control coughing.
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Gastrointestinal problems Changes in diet and digestion are often part of travel in different cultures. Sanitary facilities and fresh water are usually not easily accessible at high altitudes, and preserving food is difficult. Bacteria can be killed by boiling, if circumstances allow. Filtration can be used as an alternative, but gastrointestinal viruses may pass through filters so this method is not completely safe. Chlorine and iodine tablets have also been used to kill germs, in which case the water must be reasonably clear and ideally filtered beforehand. In addition to this, water may be purified without external substances, e.g. by using an UV lamp or solar energy. Diarrhea, often accompanied by abdominal pain, is another frequent affliction. In such conditions, it is important to drink plenty of liquids containing sugars and electrolytes. Antibiotics are not recommended to treat altitude-related diarrhea except in obvious cases of serious bacterial infection, in which case an antibiotic like ciprofloxacin is most often used. Unnecessary antibiotic use, however, often compromises the body's natural gut microbiota, which can lead to further gastrointestinal symptoms and increase the risk of antibiotic-resistant bacteria in the digestive system. Flatulence is a frequent problem that may be caused by both a change in diet and more air being swallowed due to rapid breathing.
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Eye conditions The most common eye condition at high altitude is acute keratitis, often called snowblindness. It is caused by powerful ultraviolet radiation at high altitudes, as well as dry and cold air. Acute keratitis is characterised by eye pain, redness, foreign object sensation, excessive tearing, photophobia and vision impairments. Symptoms are often not felt until several hours from exposure to radiation and they usually subside in one to three days. For treatment, artificial tears are used and sometimes antibiotic eye drops with anti-inflammatory steroids. Snow blindness can be prevented by using glacier glasses that protect the cornea from UVA and UVB radiation. Lack of oxygen may cause high altitude retinopathy and macular hemorrhage that only becomes apparent at altitudes of over 4,000 metres. This is often accompanied by impairment of vision, which is usually reversible, and these patients often also suffer from high-altitude cerebral edema.
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Frostbite Skin damage due to frost results in frostbite, which can be either superficial, when the top layer of the skin freezes, or deep frostbite where deeper layers of tissue are damaged. The parts of the body most sensitive to frostbite are the face, ears, hands and feet, where the surface is proportionally large and the are no large muscles to heat the tissue. In cases of surface frostbite, the skin will become white or grey and sore to the touch. The frostbitten part is cold and stiff, while the tissues under the skin remain soft. The symptoms are mainly a stinging sensation and pain. In cases of deep frostbite, the skin is even colder and harder and does not move when pushed. The colour of the skin will be white or grey-white. Pain is not as pronounced as in cases of surface frostbite and over time, blisters may develop. Frostbite is treated by moving the patient from the cold and to a warm place while removing clothing and anything else that may be in the way of the injury. It is important to prevent the frostibite area from freezing again, but rubbing the area is not recommended. A variety of heating techniques may be applied as conditions permit, such as inserting an affected body part into a warmer armpit or groin area or using a warm, damp cloth. If conditions allow, the frostbite area is then heated for 15-60 minutes in water that is 37-39 degrees Celsius. It is important to administer painkillers as frostbite is often very painful. Dry and clean bandages are then applied to prevent infections.
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LISTS OF MEDICINES Mountain expedition to an altitude of 2,500–6,000m •
Paracetamol
•
Paracodeine
•
Ibuprofen
•
Acetazolamide
•
Antibacterial eye ointment
•
Ciprofloxacin
•
Sildenafil/adenafil
Deleted: T
Mountain expedition to an altitude of over 6000m •
Paracetamol
•
Paracodeine
•
Ibuprofen
•
Acetazolamide
•
Antibiotic eye ointment
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Ciprofloxacin
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Sildenafil/adenafil
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Dexamethasone
36 High Altitude Diseases
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The authors standing in front of the Landspitali – The National University Hospital of Iceland in Reykjavik. From the left: Ólafur Már Björnsson, Gunnar Guðmundsson, Magnús Gottfreðsson, Engilbert Sigurðsson and editor Tómas Guðbjartsson. Photograph by Kristinn Ingvarsson.
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High Altitude Diseases 37
HIGH ALTITUDE DISEASES This booklet provides an overview of the most common diseases that may occur at high altitudes; both acute mountain sickness (AMS), which is the most common form of high altitude illness, and lifethreatening conditions such as high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE). Acclimatisation, i.e. the body’s natural response to lack of oxygen, is explained in brief, and other common conditions at high altitude, such as sleep disturbance, gastrointestinal problems, snow blindness and frostbite, are also reviewed. Treatment of the most common conditions is discussed, and at the back is a list of medicines that may be helpful to bring along when mountaineering at high altitudies.
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