Every year many people all over the world travel to mountains for recreational holidays, adventure sports and to visit places of worship. Trekking and mountain climbing are drawing more and more enthusiasts every year to sites as high as 5000-6000 m.

Apart from temporary visitors, some people reside permanently in mountainous regions. There are some 140 million permanent inhabitants at  High Altitudes (HA, terrestrial heights more than 2500 m or 8000 feet above mean sea level) in the Himalayan, Central Asian, East African, Andean and Rocky mountain regions.

High Altitude Environment and its Effects

High Altitude (HA)  presents an extreme environment with hypoxia (less oxygen in the atmosphere), extreme cold, high wind velocity, increased UV radiation. These areas are also arid in nature with sparse vegetation and less availability of potable water.

These factors vary in magnitude depending upon location and season, and set a formidable challenge to human adaptability. They cause stress to human beings encountering them for the first time and affect their normal efficiency. The bodies of permanent dwellers have been adapted to some of these conditions.

 Acute mountain sickness

The decreasing atmospheric pressure along with increasing altitude is the major biophysical governing factor at high altitudes. For centuries it was well known that breathing in high mountains is difficult. By 37 BC, the ancient Chinese recognized a peculiar illness when they traversed certain high passes of what they later called little headache and great headache mountains.

The first westerner who described mountain sickness was the Jesuit priest, Joseph de Acosta (1590), who accompanied the Spanish Conquistadors in Peru while crossing through Andes.

Whymper (1892), the conqueror of the Matterhorn (Swiss/Italian border, 4480 m) who opened up the way for the scaling of peaks throughout the world, was under no illusion that all that was required was expertise in climbing and determination.

After his expedition into Andes he concluded that none can escape from the high altitude effects on respiration. He describes intense headache, a marked acceleration of pulse and  'an indescribable feeling of illness pervading the whole body' while they were 'preoccupied by paramount necessity of obtaining air.'

Since then researchers have named the syndrome Acute Mountain Sickness (AMS). Acute Mountain Sickness is characterized by a constellation of symptoms; headache being the main one. Nausea, vomiting, dyspnea (shortness of breath), and insomnia are other common symptoms.

The travelers can also experience impaired cognition and balance. Onset of symptoms typically occurs within hours to three days after arrival at altitude.

These symptoms tend to resolve after several days but can persist for up to two weeks. AMS can be the harbinger of the more severe conditions, High Altitude Cerebral Oedema and High Altitude Pulmonary Oedema, collection of fluids in brain and lungs respectively.

Anorexia and weight loss

Many studies have shown that subjects lose significant amounts of body mass, fat mass as well as fat free mass during a climb to and/or a short stay at HA. HA induced weight loss is mainly caused by malnutrition probably due to hypoxia related anorexia, independent of AMS.

Hypophagia (less eating, from the Greek word phagein, ‘to eat’) is more pronounced during the first three days of exposure to HA even when the  best possible food is available. Various studies have been undertaken by the Defence Institute of Physiology and Allied Sciences(DIPAS), DRDO, to explore the physiological basis of anorexia of HA in humans, especially Armed forces personnel posted there, as well as in experimental animals.

Detailed studies are required to understand the basis of anorexia at extreme altitude above 5000 m to develop effective therapeutic and preventive measures. How to prevent ill effects?

Acclimatization

Acclimatization is the gradual adaptation of the human body to increased altitude and a key element on climbs or mountain treks above 2500 m. The concept of acclimatization was noted as early as the 19th century. Himalayan explorers dreaded the rigors of crossing high passes, but they also knew that initial unpleasantness of altitude diminish with time spent in the mountains.

Explorers, physicians and researchers in the mid 18th century knew that the people who live permanently at high elevation, like Sherpas in Himalaya or Andean natives, are better adapted to altitude than visitors. There is also evidence that climbers adapt a little if they have been at high altitudes. Expert climbers like Meissner have even climbed the Everest without carrying oxygen cylinders.

However, even accomplished climbers of Himalayan peaks will be off their game, perhaps severely, if they go from sea level to 3500 m without acclimatizing. Skiing and snow boarding are sports that require at least short term exposure to altitude above 2500 m.

Some people get AMS and some people do not, and some people are more susceptible than others.
Gradual acclimatization of varying days at different heights, i.e. 6-7 days at 3500 m and subsequently four days for each 1000m ascent is to be followed.

A person is said to be acclimatized at HA when he can eat well, sleep well and work efficiently. The best single index of acclimatization is one’s ability to maintain body weight. The induction to high altitude by road provides better acclimatization in comparison to air induction.

Carbohydrate, fat diet

High carbohydrate diets are beneficial at HA. Carbohydrates provide higher yield of energy per mole of oxygen. The energy equivalent of oxygen is 4.48 kcal/l for protein, 4.7 kcal/l for fat and 5.06 kcal/l for carbohydrate. Diets high in carbohydrates are shown to enhance the glucose metabolism at HA. To maintain adequate calorie intake fat is also important.

After acclimatization there is no change in macronutrient utilization and their digestability. Since fatty foods are calorie dense (one gram of fat provides 9 kcal whereas carbohydrates give only 4 kcal) you can maintain your calorie intake. In a study at DIPAS, intake of 325g/day fat was found to be well tolerated with 95.5 percent digestibility.

Fluid intake

In addition to cold induced diuresis, hyperventilation together with a dry environment at HA makes individuals prone to hypo-hydration. Acute exposure to moderate altitude causes transient hypo hydration, which is due to increased diuresis and reduction in thirst perception.

Prolonged stay at extreme altitude may cause severe salt and water retention. So people going to HA regions should ensure that they drink plenty of water to prevent dehydration.

Carry drinking water, if necessary
Supplementation with antioxidants and adaptogens: Studies have been carried out by DIPAS on nutritional status of troops with regard to vitamin requirement at altitude of 3600 m while subjects were consuming either fresh or tinned foods. It was found that health food supplements and “adaptogens” such as Composite Indian Herbal Preparation (CIHP) and Panax ginseng, enhance the acclimatization of soldiers at HA.

Both of these products have been evaluated for their effect on physiological, biochemical variables and also on psychological well being of soldiers.

Professional tour operators organizing strenuous treks like Kailash-Mansarovar Yatra carry this kit for providing first aid to persons suffering from High Altitude Pulmonary Oedema. Patients are placed inside the bag which is then inflated by  pumping air to a higher pressure which results in simulation  of lower altitude atmosphere.

Hapo Bag from DRDO

Defence Bioengineering and Electromedical Laboratory (DEBEL), also of DRDO, has indigenously developed a HAPO bag  which  has been accepted for use by the Indian Army. It can also be used by other trekkers and mountaineers. This automated version has some features that are superior to the imported ones like the Gamow bag and it is cheaper.

Shashi Bala Singh
Director, Field Research Laboratory (FRL), DRDO, Leh

Anuradha Ravi
 Senior Scientist, Defence Bioengineering and Electromedical Laboratory (DEBEL), DRDO, Bangalore

Tips to follow

To ensure that a family holiday or a group excursion does not end in a fiasco, please follow the following important preventive and safety measures:

Ascend slowly and gradually to higher altitude. Mountains must be approached with respect. Never be in a hurry. Don’t go ‘too fast, too high’.

Avoid physical exertion and cold exposure on arrival at HA. There is a popular saying ‘In the land of LAMA don’t try to be a GAMA’.

Take sufficient rest for at least 72 hours on arrival and follow the acclimatization schedule.
Take plenty of fluids (water, tea, coffee, tetra pack juices, hot soups, etc.), adequate food and avoid alcohol.

Carry necessary woollen clothing like sweaters, gloves, socks and thermal inner wear
Change wet garments   immediately to prevent heat loss and cold injuries.
Apply sun protective creams to exposed parts.

Siachen record

Permanent residency is restricted to about 4300 m, although some ethnic groups like miners in the Peruvian Andes are reported to live at heights 5500 m. La Rinconda in southern Peru at the height of 5100 m is probably the highest permanently inhabited town in the world.

However our soldiers are deployed at strategic peak heights up to 5800 m. Siachen Glacier with an altitude of 4500-6700 m has Armed Forces of two neighbouring countries facing each other under conditions which are unique in the world.