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"What is altitude sickness? Altitude illness is the name given to the physiological and symptomatic reactions of the human body to the low oxygen pressure (&amp;#039;thinner&amp;#039; air) that occurs at high altitude. It has 3 presentations, the last 2 of which can be fatal:  Acute mountain sickness (AMS) High altitute pulmonary oedema (HAPE) High altitude cerebral oedma (HACE)\u200B.  Where do you get altitude illness? About 20 per cent of people experience mild symptoms at altitudes between 2200 and 2500 metres above sea level. Many ski resorts are found at these altitudes. It is estimated that over 38 million people live most of their life above 2400 metres.  The incidence of altitude illness, which varies from one individual to another, is directly related to the rate of ascent. It&amp;#039;s also significantly related to how long a person stays at that height. Being physically fit does not stop you getting sick.  The risk of getting altitude illness in areas, such as Nepal and the Andes mountains, where tourist regions can be as high as 3000 to 4000 metres is very real. Each year, out of 50,000 travellers to Nepal, there are at least seven altitude-related deaths. The death rate is about 4 per cent for trips to peaks above 7000 metres. These figures have been dwarfed by the April earthquake with over 9000 deaths, 23000 wounded and the destruction of a whole economy and way of life. How do you get altitude illness? When oxygen pressure falls, the body puts in place a number of counter measures. Breathing and pulse rates increase, as does the heart&amp;#039;s pumping efficiency and the size and number of red blood cells, which are responsible for the blood&amp;#039;s oxygen carrying capacity. But the shortage of oxygen also has a number of unwanted consequences:   increased pressure in the pulmonary (lung) circulation changes in blood pH (acidity) values disturbances in the fluid or electrolyte (salt) balance leakage and spread of blood or fluid into surrounding vessels and tissues (fluid extravasation or oedema).   Altitude illness&amp;amp;nbsp;can occur by travelling relatively quickly to a greater height and staying at the new height for more than 24 hours, without adequate acclimatisation beforehand.  Altitude illness&amp;amp;nbsp;isn&amp;#039;t dependent on a person&amp;#039;s fitness and can affect even the most experienced athletes. How can altitude illness&amp;amp;nbsp;be prevented?   By taking a graded ascent. Climb relatively slowly to higher levels, and allow adequate periods of acclimatisation (two to three days) at a given height (starting from 2200 metres) before spending a night at a greater height.  It&amp;#039;s fine to climb up during the day, but you should try to get down to 2200 metres (or the height you are currently acclimatised to) in the course of the same day. Then you can move up, depending on your individual tolerance, by 300 to 500 metres, until you rest and get acclimatised again for at least a couple of days, and so on.  If you feel ill at a particular height, come down to your previously acclimatised height. Drink plenty of rehydration solutions (at least three litres a day). Avoid drinking alcohol.  Avoid getting cold.   To a certain extent, altitude illness&amp;amp;nbsp;can be prevented by taking acetazolamide (Diamox).  One day before ascent: take 125 mg twice a day. Day of ascent: take 125 mg twice a day. One to two days after: take 125 mg twice a day. Some experts suggest that to get to know the possible drug side-effects, it&amp;#039;s wise to give it a two-day trial before the trip. This is an unlicensed use of this medicine, which is also only available on prescription. So, it should only be undertaken on the advice of a doctor.  Possible side-effects include:  nausea taste disturbance tingling hands and feet frequent and copious urination visual disturbances skin rash.  But taking Diamox doesn&amp;#039;t mean people can ignore advice about slow ascent.  Danger signals for altitude illness Danger signals usually develop in the first 36 hours. They affect more than 50 per cent of travellers above 3500 metres and almost 100 per cent of people who climb quickly to 5000 metres without acclimatising.&amp;amp;nbsp;Acute mountain sickness symptoms can be non-specific\u200B.  An insignificant headache that disappears with one to two ordinary headache tablets. Nausea and general malaise/fatigue. Slight dizziness. Some difficulty sleeping.  With these symptoms at heights below 3000 metres, you can usually allow yourself to stay on and to rest for a couple of days before further permanent ascents. At heights around 3500 metres, you should try moving down 300 to 500 metres and stay there for two days before further permanent ascents. Serious symptoms of altitude illness  A severe, enduring headache, which is not cured by a couple of ordinary painkillers. Marked nausea and repeated vomiting. Irritating dizziness or actual difficulty with balance and direction. Regular visual disturbances, with flickering vision and problems judging distance.  Pressure in the chest, rapid breathing and pulse rate, crackles in breathing and shortness of breath. Swelling beneath the skin (oedema), typically around the eyes and in some cases swollen ankles and hands. Confusion. Convulsions.   In the presence of these symptoms, medical attention must be sought immediately, and the patient brought down to the lowest possible height. Acute mountain illness that can kill\u200B Acute mountain illness that can kill is related to two life-threatening complications of acute altitude illness. Both have a high mortality rate and may occur when you have already spent 24 to 36 hours at &amp;#039;too great&amp;#039; a height (typically over 3500 metres). These are:  HAPE: high altitude pulmonary oedema (water in the lungs) HACE: high altitude cerebral oedema (fluid on the brain).   High altitude pulmonary oedema (HAPE) The symptoms of HAPE are predominantly severe and include: increasing difficulty breathing, dry cough, pressure in the chest, palpitations and fatigue.  A bubbling noise may be heard during breathing (oedema in the lungs). The lips, outer edges of the ears and nails may look blue (cyanosed) due to a shortage of oxygen.  The patient should be transported to the lowest possible altitude as soon as possible.  If possible, oxygen should be given by nasal catheter, or if an oxygen mask and bottle are available as CPAP (continuous positive airways pressure), or better still, hyperbaric treatment (Gamow-bag). A calcium antagonist (nifedipine capsules 10 to 20mg (quick-acting) can be considered by a knowledgeable and expert physician \u2013 this must not be repeated, but followed by slower acting nifedipine tablets 20mg every six hours).  Dexamethasone injection (into a vein or a muscle) can be considered by a knowledgeable and expert physician. The victim should be transported sitting on a stretcher or something similar.  High altitude cerebral oedema (HACE) The symptoms of HACE are essentially:  severe headaches visual disturbances light shunning irritability vomiting vagueness and confusion possible unconsciousness convulsions.   The patient should be transported to the lowest possible altitude as soon as possible. Oxygen (CPAP) or better still, hyperbaric treatment (Gamow-bag) should be given. Dexamethasone injection (into a vein or a muscle) should be given. Convulsions may be treated with a benzodiazepine \u2013 eg diazepam (rectally if required). Transportation should be in the recovery position (strapped lateral) to avoid vomit getting into the lungs.  Who should never be exposed to high altitude?   People with chronic diseases of the heart/lungs (eg angina pectoris or chronic bronchitis, emphysema and some people with severe asthma). People with anaemia, including sickle-cell anaemia (low haemoglobin content in the blood, even sickle cell trait may be affected). People with untreated blood clotting disorders and a history of thromboses (clots), such as antiphospholipid syndrome (Hughes&amp;#039; Syndrome). People who have previously developed HAPE or HACE.   Who should be careful at high altitude?   People with successfully treated chronic diseases (eg heart/lung, emphysema, asthma, kidney failure, transplant recipients).  Pregnant women. Children. People with severe diabetes. People with high blood pressure.  People with a tendency to sleep apnoea. People who have previously developed HAPE or HACE.  Other problems to consider are the prevention of snow blindness, cold, frostbite and sunburn. International information sources International Society for Mountain Medicine (ISMM) British Mountaineering Council (BMC)  Epilepsy action Foreign &amp;amp;amp; Commonwealth Office travel advice Frostbite Chinookmed Fit for travel  International Porter Protection Group (IPPG) Kathmandu Environmental Education Project (KEEP) Medex \u2013 Medical Expeditions has a full list of UK doctors holding the UIAA Diploma of Mountain Medicine Mountains for Active Diabetics (MAD) Oxygen (constant flow system) Topout and Poisk Oxygen (demand flow system) Summit Oxygen Portable Altitude Chamber (PAC) Union Internationale des Associations d&amp;#039;Alpinisme (UIAA) The High Altitude Medicine Handbook, by Drs Pollard &amp;amp;amp; Murdoch  Bugs, Bites, and Bowels, by Dr Wilson-Howarth  Altitude Illness: Prevention &amp;amp;amp; Treatment, by Dr Stephen Bezruchka  Pocket First Aid and Wilderness Medicine, by Drs Jim Duff and Peter Gormley  Last updated 19.07.2015 "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.netdoctor.co.uk/conditions/a5671/altitude-illness/>