Altitude Sickness | Acute Mountain Sickness AMS

Altitude Sickness Overview.

With the Acute mountain sickness the travellers are drawn to high-altitude places in ever-increasing numbers – Nepal alone now receives more than one hundred thousand trekkers from around the world every year. It can be easy to underestimate the dangers of altitude illness. Because deaths from these conditions are all the more tragic because they are entirely preventable.

Mountain climbers, serious trekkers, romantics sauntering through the foothills of the Himalayas, native porters, skiers in North America and Europe, pilgrims to high altitude shrines, diplomats posted to La Paz or Lhasa, miners in South America, and Everest marathon runners have something in common: they are all exposed to the effects of high altitude, and maybe at risk from a potentially fatal but eminently preventable problem: acute mountain sickness, commonly referred to just as AMS.

AMS consists of headache plus any one of the following symptoms in different degrees. Nausea, tiredness, sleeplessness or dizziness, occur at altitudes of around 8000 ft or higher where path physiological changes due to lack of oxygen may manifest. Another term, “altitude illness”, is also widely used – an umbrella term that includes the benign acute mountain sickness and its two life-threatening complications, water accumulation in the brain (high altitude cerebral oedema, HACE) or high altitude pulmonary oedema (HAPE, water accumulation in the lungs). The latter two complications may follow AMS, especially when people continue to ascend in the face of increasing symptoms. In keeping with the Jesuit tradition of painstaking documentation, Father Joseph de Acosta, a sixteenth-century Spanish Jesuit priest, is credited with having first described the effects of high altitude on humans. In vernacular Nepali, mountain sickness is called “Lake Lagne”.

Those most in danger from complications are people who do not “listen to their body”, and heed the early warning signals of AMS; they can go on to suffer from HAPE and HACE and may even die – a process that has been carefully documented in important autopsy studies performed by Walter Bond and John Dickinson during the Seventies in the old Shanta Bhawan hospital in Nepal.

Chronic mountain sickness is an entirely different condition, recognized by Carlos Monge Medrano in high-altitude long-term residents of South America during the Twenties. Such maladaptation is seldom found in the Sherpas or Tibetans, possibly due to thousands of years of exposure to high-altitude living. (South American populations are relatively newcomers to high-altitude sure.)

The present discussion will be confined to acute exposure to altitude in short-term sojourners.

Acute Mountain Sickness.
If a participant on an Everest trek suffers from a mild headache and nausea at Namche Bazaar (12,300ft), he might take aspirin and wait for these symptoms to go away; however, if the symptoms progress to vomiting and a splitting headache, he must assume that he is suffering from AMS and make plans to descend. It is amazing how many people in this situation ignore the dangers and continues to ascend with their friends, trying to blame their symptoms on poor fitness or the flu. For some people, it’s the high investment of time, effort and money, for others perhaps it’s peer pressure or reluctance to accept defeat. A further problem is that many in the burgeoning adventure travel industry are clueless about mountain sickness.

AMS may set in within hours to days of arrival at high altitudes. The onset of symptoms is usually gradual, which is why it is so vital to watch out for early warnings. Thus, does a person feel excessively tired; is she the last one to drag herself into camp?

What causes AMS?
Lack of oxygen is the main reason for AMS. Although the proportion of oxygen in the atmosphere always remains the same (21%), as we go higher the “driving pressure” decreases. The driving pressure depends directly on the barometric pressure and forces oxygen from the atmosphere into the capillaries of the lungs. Reduced driving pressure results in decreased saturation of oxygen in the blood and throughout the tissues.
Just what causes some people to suffer from AMS but not others are largely unknown, but there are clear-cut and important preventive factors that are now (see below). AMS’s exact mechanism (path physiology) has similarities to that of HACE.

High Altitude Cerebral Edema (HACE).
Our trekker in the above example would probably go on to suffer from HACE if he continued to ascend despite the headache and vomiting; the symptoms of HACE are an extension of those of AMS. From fatigue, there is progression to lethargy and then to come. Or there may be confusion and disorientation. A useful test is to see if the person can walk a straight line. If someone walks erratically or is unsteady, it is thought that he has HACE, which is life-threatening, so immediately get assistance. An immediate helicopter evacuation is necessary given how crucial this situation is. Fluid changes in the brain’s tissues are most likely the cause of HACE. Reduced oxygen levels cause swelling within the confines of the bony skull. The resulting rise in pressure may lead to lethargy and eventually coma.

High Altitude Pulmonary Edema (HAPE).
This disease may follow AMS, but often it may appear independently. Usually, the tourist discovers that, although not have a headache or feeling sick, walking makes him breathless. There may be a nagging cough and he too may have ascribed these symptoms to a cold. He may be suffering from subclinical or early HAPE, a well-recognized entity. With further ascent this may progress to short breath even at rest – descent is now obligatory, or the outcome may be fatal. Low oxygen causes the pulmonary artery to narrow and this results in the exudation of blood near the smaller branches of the lungs (the alveoli).

If the exudation continues, blood may escape into the alveoli leading to a cough with watery, blood-tinged phlegm. Such exudation or “water-logging” of the lung tissue interferes further with oxygenation. A popular, compact device called a pulse oximeter can measure the oxygen level. In the mountain blood is simply and rapidly, using a sensor attached to the index finger. It can be very helpful in confirming if HAPE is present.

What is acclimatization?
Acclimatization is a state of physiological “truce” between the body of a visitor. Actually, it is the hostile low-oxygen environment of high altitude. This truce permits the trekker to ascend gradually. (This is distinct from “adaptation” – a permanent change to the organism, perhaps over thousands of years, perhaps even at a genetic or evolutionary level, to facilitate survival at altitude. Scientists are trying to decipher if the Sherpas or Tibetans have made such an adaptation.)

For acclimatization to take place the single most important step is hyperventilation. Especially when the trekker unconsciously breathes faster and more deeply than normal, even at rest, to make up for the lack of oxygen. However, hyperventilation also leads to the loss of carbon dioxide from the blood, making the blood more alkaline, and in turn depressing ventilation. However, 48 to 72 hours after exposure to high altitude, the kidney comes to the rescue and begins to excrete alkali from the blood to restore a more balanced environment in which hyperventilation can continue unabated.

How to Prevent Altitude Sickness for Trekkers.
Drink 3 to 5 Liters of Water Per Day
Quite simply, drink a minimum of five litres of water per day, no matter what. This is easier at lower elevations when it’s hot, but becomes more burdensome. But when temperatures cool off and you perspire less. After a few litres, you may feel properly hydrated. Because your body is doing extra work with less oxygen and needs the water. Force down five litres per day, without exceptions.

Avoid Dramatic Gains in Elevation.
Treks at altitude should avoid big single-day gains in elevation (more than 1,500 vertical feet). A common misconception about trekking at high altitudes is that physical condition dictates the body’s ability to fend off altitude sickness. This causes many people who are “in good shape” to ignore the rules of acclimatization, go too high too fast, and have problems. Your itinerary should factor in altitude gains and consequently, some hiking days will end early. Embrace the pace, rest your legs and hydrate.

Climb High, Sleep Low.
You will acclimatize better if you expose yourself to higher altitudes but return to a lower altitude to sleep. After reaching the campsite, scramble up a nearby hill, scope out the scenery, and back down for better sleep. When you have a rest day, using the opportunity to hike to higher elevations and back down is worth the effort. At higher altitudes around 10,000 feet and above this rule becomes even more important to your body. It is the learning to cope with considerably less oxygen.

Eat, Eat, Eat…
Because soy is nourishing and rich in carbs, your body is working harder than normal. The Snickers bar is available in even the smallest communities (and for very cheap). Yes, too much sugar but full of good things like nuts and chocolate. Do a good deed and buy some for your porters and guide whenever possible.

Listen to Your Body.
By following the above rules, you will greatly increase your odds of staying healthy throughout your trek. But everybody reacts differently to altitude so pay close attention to how you feel. Every trek should have rest days built-in and you shouldn’t be afraid to use them. Stay hydrated, wear sunscreen, and have layers available for protection from the powerful sun. Avoid alcohol and other substances. Monitor yourself and always communicate any health concerns to your group. An estimated 75% of people feel some effects of altitude, mostly headaches, nausea, fatigue, and trouble sleeping. These are mild manifestations of Acute Mountain Sickness (AMS). Mild AMS should not interfere with normal activity and the symptoms should subside as acclimatization occurs. As long as the symptoms are mild, it’s generally okay to continue hiking up at a moderate rate. If feeling poorly persists or worsens, turn around.