Essentials of High Altitude Medicine relating to the Nanga Parbat region

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"Traveling at high altitude can be hazardous!"

The informations listed below are based on a thorough analysis of published and unpublished documents. They are intended for educational use only and are not a substitute for specific training or experience. We assume no liablity for any individual's use of or reliance upon any material contained or referenced herein. This document is prepared to provide basic information about altitude illnesses for the lay person.
Medical research on high altitude illnesses is always expanding our knowledge of the causes and treatment. When going to altitude it is YOUR responsibility to learn the latest information. The material contained in this article may NOT be the most current.

Table of Content:

Specific high altitude problems around Nanga Parbat: on the Diamer, Raikot or Rupal-face
 "Lake Louise Score"
High altitude  |  Acclimatization  |  Fluid balance  |  Acute mountain sickness
High altitude pulmonary oedema (HAPO  |   High altitude cerebral oedema (HACO)
Peripheral oedema  |  Retinal haemorrhage  |  Sleep and periodic breathing
Neurological disorders  |  Thrombosis  |  High altitude cough   |  Infections at high altitude
Asthma  |  Hypertension   |  Diabetes mellitus  |  Contraception  |  Pregnancy and fertility
Medical treatment of local persons  |  Portable hyperbaric chamber
Risk of travelling with organized groups  | Malaria
Disclaimer | Source of information

The term "Lake Louis Score" is useful as an keyword for internet-searches on AMS literature. One can download from this website as an pdf-File (57,701bytes) the worksheet of the "Lake Louise Score"-questionaire that we use by ourselve.
It is however important to realise that all scoring systems can overdiagnose AMS. An hangover or flu for instance will give a positive AMS score even at sea level, so it is important to use them in context of a recent rise in altitude.
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High altitude
The term "High Altitude" can be taken to mean heights between 2,400m - 4,300m (8,000ft - 14,000ft). In this range of elevations the most high altitude problems arise. 2,400meters (8,000ft) is a rough threshold above which altitude illness occurs. In airplanes the cabin-pressure is adjusted to an setpoint similiar to 8,000ft (2,400m). The range 4,300 - 5,500m (14,000-18,000ft) is named in the literature "Very high altitude", and is normally encounterd only by experienced, well conditioned climbers. Rapid ascent to such altitudes without prior acclimatization is dangerous and can cause all types of altitude illness.
At the "Extreme altitude" between 5,500-8800m (18,000-29,000ft) most climbers are acclimatized, those who are susceptible to altitude illness usually have been washed out.

At high altitudes, up to 100km, the composition of the atmosphere is the same as at sea level: about 21% oxygen. But the partial-pressure of the oxygen (and so the number of molecules present in a specific volume of air) is reduced in parallel with the reduction in atmospheric pressure at increasing altitudes (Daltons- and Boyle-Mariottes-Law of Gas-physics) . At 4,000m (13,000feet) the barometric pressure is only 60% of the pressure at sea-level, so there are roughly 40% fewer oxygen molecules per breath. When you reach to the Mazeno-Pass between the Rupal- and Diamer-side of Nanga Parbat, the air-pressure at this elevation of 5,377m is nearly the half of the standard-pressure at sea-level, and your arterial oxygen-saturation will fall below 80% of the normal value. Out of this your physical working-capacity will be decreased by about 30%. The table below gives you an rough idea of the altitude-related physics:

Height, pressure and temperature conversion table

Fluid balance
An adult male of average size loses 1.5-2 liters of water from his body each day in normal circumstances, out of which are 0.5-1 liter lost "insensible" by evaporation from the lungs to moisten the air that is inhaled. Specially at high altitude and low temperatures, where the watercontent in the air is heavily reduced, this quantity of fluid-loss increases significant, up to 6 liters. The principal cause of dehydration at high altitude is the increased fluid loss associated with more rapid and deeper breathing of cold air. The urine volume and color provides a highly reliable-indication of the balance between fluid intake and losses. A 24hour volume of less than 500ml of deeply colored urine is indicative of fluid depletion. Persons at high altitude must consiously force themselves to drink large volumes of fluid. Thirst alone is not a reliable indicator of the need for water. Almost any nonalcoholic fluid is suitable, but since water contains no electrolytes, fruit juices, soft drinks, soups and similar liquids should be used. Coffe, tea, and hot chocolate are not satisfactory because they contain caffeine and related substances, which are diuretics (stimulates excretion of urine) and increase renal (kidney) fluid loss. Fluids lost through vomiting, diarrhea, or excessive perspiration should be replaced with an electrolyte solution, known in Pakistan as "ORS" - oral rehydration salt solution. This powder for an oral fluid replacement solution is easily available in the shops and a larger collection of this inexpensive packages should be bought along with your equipment and food. Excessive fluid loss through the lungs due to altitude should be replaced by a solution of glucose, because no electrolytes are lost with the moisture in expired air. Assure you, that the water is taken from a clean source and that it is boiled. If you work "oldfashioned" and use chemicals as water disinfectant be aware, that at the given cold water-temperatures chemicals might not work well. We prefer "backpackers" waterfilter-systems that we operate strictly! ourselve and keep with our personal belongings.
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Acute mountain sickness (AMS)
There are no specific factors such as age, sex, physical condition that correlate with suspectibility to altitude sickness. Symtoms usually start 12-24hours after arrival at altitude and begin to decrease in severity about the third day. The most important risk factors for the development of AMS are altitude gained (especially sleeping-altitude), rate of ascent and level of exhaustion. Various studies in Nepal showed, that about 43-53% of trekkers who walk to altitudes above 4,000m over five or more days develop AMS. Exhaustion may be a risk factor for AMS, while lack of physical fitness is not.
There is no satisfactory test available which will predict who will get AMS, but one study has demonstrated those with a hypersensitive gag reflex, extreme dizziness on hyperventilation or short breath-holding time are more susceptible.
Hypoxia (lack of oxygen) causes alterations in fluid and electrolyte balance, favouring fluid retention and an increase in extracellular fluid. This is most evident as peripheral oedema, but also occurs in the brain.
The principal symtoms of AMS are headache, nausea, vomiting, anorexia, fatigue, dizziness and sleep disturbance. Gastrointestinal disturbance is common, with nausea and anorexia frequently the predominant symtoms. Absence of the normal diuresis (production of urine) experienced at high altitude is characteristic. Symptoms of AMS usually develop after about 6 hours and resolve in one to three days if further ascent does not occur.

 
There is one drug prophylaxis seen as preventing or minimizing AMS: Acetazolamide . This carbonic anhydrase inhibitor increases renal bicarbonate excretion and produces a metabolic acidosis and stimulates respiration. It can help to maintain oxygenation during sleep and can so prevent periods of extreme hypoxaemia. Acetazolamide is an sulpha drug and carries the usual precautions about hypersensitivity! It is known to cause severe allergic reactions to people with no previous history of Acetazolamide or sulfa allergies. Some M.D. recommends a trial course of the drug before going to a remote location where a severe allergic reaction could prove difficult to treat. Ask your medical doctor about details.
Simple analgetics may relieve headache but are often ineffective. Antiemetics can be used for nausea and vomiting. It cannot be overemphasized, that descent remains the most important and only definitive treatment for all form of altitude illness. If there is any doubt, descent ! At the  Diamer- and Rakhiot-Side of Nanga Parbat you can reach easily within hours to very safe and low altitudes below 2,400m (8,000ft). On the Rupal-side it is much harder to reach quickly to low altitudes.
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High altitude pulmonary oedema (HAPO / HAPE)
HAPO (or HAPE in other writing) accounts for the most deaths from high-altitude illness. As far as HAPO is understood, an abnormally powerful and uneven pulmonary hypoxic vasoconstriction (narrowing of blood vessels) leads to high vessel wall stress and capillary damage. So HAPO is characterized by very high pulmonary artery pressure and oedema of high protein content. HAPO usually occurs in the first two to four days after ascent to altitudes above 2,500m. It often follows abrupt ascent by an unacclimatized person. It may be more common in men than women and is often associated with exertion. The incidence of HAPO ranges from 0.6% at 3,500m to more than 2% above 4,000m. About 25% of untreated HAPO-cases are ending with death.
The first symptoms of HAPO are usually dyspnoea (laboured or difficult breathing) on exertion and reduced exercise tolerance, greater than expected for the altitude. Tachycardia (fast heart rate) and tachypnoea (fast breathing rate) are present at rest as the illness progresses. Fever is usually present, but the temperature rarely exceeds 38.3C. Blue lip-color and hard caughing are many times initial signs, wheras bubbling-noises during breathing are developing in a very late stadium. Situation becomes usually very worse at the second day or second night after reaching to the new altitude. Death commonly results from incorrect diagnosis and failure to descend. Descent is the treatment of choice. Oxgen often produces immediate and dramatic improvement, and can be lifesaving. Treatment in a portable hyperbaric chamber may relieve symptoms and faciliate descent. In any case keep the patient sitting upright. The vasodilator-drug Nifedipine has been shown to help relieve symptoms and is seen as most useful.
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High altitude cerebral oedema (HACO / HACE)
An increase in extracellular fluid, and an increase in cerebral blood flow can lead to cerebral thrombosis and haemorrhages. High altitude cerebral oedema (HACO or HACE in other writing) is a rare but life-threatening form of altitude sickness. It is likely to occur above 3,500m, but is has been described at altitudes as low as 2,500m. Probably 1-2% of those ascending to 4,500m are at risk. About 40% of untreated HACO-cases are ending with death.
People with HACO become confused, disoriented, irrational, unusually quiet or noisy, clumsy with their hands, unsteady on their feet and begin to hallucinate. Eventually they became lethartic and sleepy before slipping into a coma.The progression from initial symptoms to coma may take as little as 12 hours. Ataxia (in-coordination, stumbling unsteady walk) is one of the first signs to appear and can be readily tested by heel-toe walking.
Anyone suffering from symptoms of HACO should descend immediately or death is a likely consequence! The drug Dexamethasone is seen and oxgen, in combination with a prolonged hyperbaric treatment in portable hyperbaric chambers, is known as additional help to...Descent. The ingestion of alcohol, hypoglycemia and carbon monoxide poisoning show similar symptoms as HACO.
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Peripheral oedema
Peripheral oedema, especially involving hands and face, is common at high altitude (18% in one report), and is twice as common in women. Treatment is not usually necessary but diuretics (in the absence of symptoms of AMS) have been used, although there is the risk comming out of increased blood-viscosity.
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High altitude Retinal haemorrhage
Retinal haemorrhages (areas of bleeding in the eyes) occur in 30-35% of trekkers at 5,000m and is normally only detectable by using instruments. They are less common in those with previous high altitude exposure and in high altitude natives. Although descent might be advisable, no specific treatment is available. They are likely to resolve rapidly and spontaneously.
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Sleep and periodic breathing (Cheyne-Stokes respirations)
Sleep is of poor quality at altitude with a decrease in quantity of both deep sleep and rapid eye movement (REM) sleep. Periodic breathing characterized by repeated episodes of hyperpnoea (increased rate of breathing) followed by apnoea (arrest of breathing) is a common occurance at high altitudes (Cheyne-Stokes Respirations). This type of breathing is NOT considered abnormal at high altitude, but if it occurs during an illness other than AMS or after an injury, it may be a sign of a serious disorder. During the period when breathing stops the person often becomes restless and may wake with a sudden feeling of suffocation. The drug Acetazolamide is seen as an very effective treatment. It can reduce the amount of periodic breathing and so can improve arterial oxygen satuarion in sleep. As mentioned above (see: AMS), Acetazolamide is an sulpha drug and carries the usual precautions about hypersensitivity! At higher altitudes conventional sleep-providing-drugs should not be used because they can lead to unnecessarily low blood oxgenation during sleep, which may increase symptoms of AMS.
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Neurological disorders
Several mountaineers have developed focal neurological events whilst at high altitude, typically at heights above 5,500m. Most have taken the form of transient ischaemic attacks (critical reduction of blood supply), but permanent loss of function has been documented. Immediately descent and administration of oxygen (if available) is recommended. In addition, as in HACE, the drug Dexamethasone is seen as effectful as for HACE. Migraine at high altitude is very common.
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Thrombosis
Cerebral and venous thrombosis and cases of pulmonary thrombosis have been reported at high altitude, especially above 6,000m. Risk factors include cold, dehydration and decreased physical activity (e.g. while tent-bound in bad weather). Raised haematocrit and increased blood-viscosity may also contribute. Prevention is clearly important. The body (especially limbs) should be protected from cold and regular limb movement during periods of inactivity should be performed. Adequate hydration should be maintained.
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High altitude cough
Most cases of cough and sore throat at altitude do not have an obvious infectious aetiology (cause of desease). Increased ventilation, dry cold air and mouth-breathing dry the respiratrory mucosa (tissue covering the mouth, windpipe, food pipe) presumably leading to high altitude cough. Cold-induced rhinorrhoea (runny nose) is also common amongst high altitude travellers. Many climbers find relieve from high altitude sore throat by using throat lozenges.
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Infections at high altitude
Travellers have long noted that infections are common at high altitudes and are often slow to resolve. As studies showed, amongst high altitude trekkers in Nepal, 87% experience at least one symtom suggestive of infection: 75% develop coryza (discharge from the nose), 42% cough, 39% sore throat, 36% diarrhoea. The effect on high altitude on the immune response has not been studied extensively, but the information available suggests that susceptibility to bacterial infections is increased while response to viruses is unchanged.
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Asthma
Interestingly, asthma often first increases because of the cold air, but then improves at altitude because the less dense air reduces resistance in the airways and there are fewer allergens. Trekkers and climbers with asthma should be advised to continue taking their normal sea level medication, even if the symptoms seem to improve. Ask your medical doctor for informations!
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Hypertension
There are conflicting results from studies on the effects on blood pressure of ascent to high altitude. Because the body tries to compensate oxygen-deficit by increasing the blood-pressure, hypertension increases at high altitude, at least during the first days of acclimatization. It is reported, that changes in blood pressure are probably of a  minor degree in both normotensive and hypertensive subjects. Well controlled hypertension is not seen a contradiction for travel to high altitude, specially if ergometer-tests with a high working load show no risky increase in bloodpressure.
In the moment, we are doing research by our own about hypertension at high altitude. Specially we are checking the work and sideeffects of diuretics (hydrochlorthiazide), which are mostly used in therapy of hypertension.
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Diabetes mellitus
An increase in energy expenditure above sea-level activity (as it is likeley on treks or expeditions) may alter carbohydrate and insulin requirements. Several trekkers have died in Nepal of diabetic ketoacidosis at high altitude. The symptoms of Hypoglycemia can be misinterpreted as HACO, so fellow travellers in the party should know about a persons status as diabetic.
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Contraception at altitude
The increade blood viscosity resulting from the raised haematocrit may increase the risc of thrombosis associated with oestrogen and some progesterone-containing oral contraceptives.
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Pregnancy and fertility at altitude
Except natives, living at high altitudes since generations, pregnant women should avoid high-altitude sojourns. Fertility is seen as reduced in  men at altitude as a result of hypoxia to the testes but as it is said usually returns to normal by two to three weeks after return to sea-level.
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Medical treatment of local persons
Travellers are often approached by locals requesting medical assistance. In most cases the best approach is to refer them to the local health facility and not to dispense medications. By freely dispensing  medications the traveller reinforces the notion that foreign medicine is superior and runs the risk  of eroding confidence in local health services. To make matters worse, foreign medications are usually more colourful and attrctive than those produces in the country and are consequently considered to be more potent. On the other hand, confidence in Western medicine may be lost by inadequate or inappropriate therapy; only initiate therapies that will work and avoid the temptation to use placebos. In some situations, e.g. assisting someone injured, it is clearly appropriate to offer what you can confidently manage.
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Portable hyperbaric chamber
Portable hyperbaric chambers (pressure-bags) are seen as a regular practice for the treatment of altitude illness, although scientific studies showed, that the treatment led only to short term improvement but had no long term beneficial effect.
Two types of portable hyperbaric chambers are usually available:
One is cylindrical in shape with an weight of about 6.5kg. This chamber works with an internal pressure of 104mmHg, which is roughly equivalent to an altitude-decrease of 2,000m.
The other model is of conical shape with an weight of 4.8kg. It works with an internal pressure of about 165mm Hg, which is equivalent to an altitude-decrease of about 2,500m.
Researches showed, that the beneficial effects usually disappear within 10 hours. Furthermore, patients with HAPE frequently do not tolerate the recumbent position necessary for operation; raising the head end of the chamber by any means available may solve this problem.
Given the relatively short-lived benefits, portable hyperbaric chambers should only be used when descent is not immediately possible or to facilitate descent. There are no controlled data available to support any particular treatment schedule. However, pressurization for one to two hours is usually sufficient to reset the body chemistry to lower altitude which can last for up to 12hours outside of the bag and facilitate descent.
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Travelling with organized groups
There has been concern raised by an association between trekking in organized groups and the development of altitude illness. While trekkers with organized groups have a similar incidence of AMS to individual trekkers, their risk of dying from altitude illness is significantly greater. Trekkers with organized groups have to keep pace with the rest of their group and are often reluctant to admit symptoms of AMS for fear of upsetting the plans of others or being left behind. Group leaders may be reluctant to diagnose altitude illness to avoid the logistic difficulties arising from an altered itinerary. Local guides, porters, cooks and other staff are also vulnerable to altitude illness and should be cared for in the same manner as group members. Sick trekkers should always be in the company of a senior member of their trekking group.
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Malaria
Malaria is a problem in the Northern Areas, because malaria mosquitos are found up to 2,500 meters (8,000 feet). Specially in the Bunar-area the local persons are suffering from Malaria.
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