Acute Mountain Sickness(AMS) Causes and Prevention

Mountain trekkers often like to challenge themselves by reaching new heights especially in the Himalayas. Most of us have a bucket list of treks, many of which are in remote destinations in the higher altitudes of the Himalayas. Theoretically, any altitude above 7000 feet is considered as high altitude, but as experienced trekkers, many of us tend to consider only altitudes above 13000/14000 feet as high altitudes. We are tempted to summit Himalayan peaks that lay at heights of 15000 feet and more. Truly, in the Himalayas, every region has its unique beauty and in every increase of 1000 feet altitude, the Himalayas tends to become more gorgeous. But, with increase in altitude, the chances of Acute Mountain Sickness also increases.

Effect of altitude on health

The higher we climb, the air becomes thinner, significantly lowering the density of oxygen with every 1000 feet increase in altitude. The following table states the rate at which the effective oxygen level decreases with altitude with reference to sea level.

Altitude (in feet)	Decrease in Oxygen level (Approx.)	Effective Oxygen level (Approx.)
8000	26%	74%
10000	32%	68%
12000	37%	63%
14000	41%	59%
16000	45%	55%
18000	50%	50%
20000	53%	47%
22000	57%	43%
24000	60%	40%
26000	63%	37%
29000 (Mt.Everest)	67%	33%

The human brain is not tuned to function in lower oxygen level and needs time to adapt to the new heights with lesser oxygen density. At times, if our body does not get accustomed to the new height, we fall prey to Acute Mountain Sickness.

This blog is all about understanding Acute Mountain Sickness (AMS), its symptoms and its prevention in high altitudes. 

Acute Mountain Sickness

I am not a doctor by profession. The information provided here is in consultation with Dr. Aniruddha Maiti. Dr. Maiti is a doctor by profession and a seasoned trekker by passion.

Acute Mountain Sickness is the first step to mountain sickness occurring due to non acclimatization of our body in the higher altitudes. It is caused by low air pressure and density of oxygen in the air. The sickness may start from 8000 feet altitude with many people.

The basic symptoms of Acute Mountain Sickness are:

• Headache
• Loss of appetite
• Nausea or Vomiting tendency
• Fatigue

Acute Mountain Sickness is just the beginning. If not taken care immediately, the advanced stages of AMS are- 

• HAPE (High Altitude Pulmonary Edema) and
• HACE (High Altitude Cerebral Edema)

I have seen experienced non technical high altitude trekkers trekking in the Himalayan region, ignoring the possibility of HAPE. Many try to ignore minor headaches and fatigue at 10000 feet altitude. They should understand that fatigue and headaches are the primary symptoms of AMS. If not treated immediately, within a span of 2 days, the person can be a victim of HAPE- said Dr. Maiti

What can lead to Acute Mountain Sickness?

The base reason for Mountain Sickness is low air pressure and reduction in oxygen density in the air. The only way to combat AMS is acclimatization. Some people acclimatize quickly, while some take time. Your acclimatization process may become slower if:

• Cardiac exercises were not done properly before the climb
• Ascending very fast thereby not giving adequate time to the body to acclimatize
• Improper intake of food, specially carbohydrate rich foods
• Drinking less amount of water on the slope
• Did not get adequate rest/sleep

On the slope you should always take your own time and hike. You are not in a race with the others to climb the peak. Climbing slowly gives time to your lungs to adjust with the less density of oxygen and act accordingly. Normally, in these situations, your lungs tend to absorb more oxygen from the air. Therefore, it is equally important to make yourself fit by practising cardio exercises like jogging, swimming etc. well ahead of your trek.- said Dr. Maiti

According to Dr. Maiti, the key to minimise the risk of Acute Mountain Sickness is drinking adequate quantity of water on the slope and sleeping at a lower altitude if you are climbing more than 1000 feet in a day.

There is a proverb “If you are thirsty on a slope, you have already been dehydrated”. Dehydration is another key factor for acute mountain sickness. One should keep on sipping water while hiking to avoid dehydration. Drinking alcohol and smoking is a big no in the high altitudes. Both of these dehydrate the body very quickly.

Acute Mountain Sickness Prevention

• Prepare well for the trek. Focus on cardio exercises and strengthening your calf muscles.
• Drink at least 4 litres of water each day starting 15 days before the trek. On the trail drink at least 2 litres of water in each 4 hours hike.
• Do not skip any meals- breakfast, lunch or dinner on the trek
• Eat more carbohydrates like potatoes, roti and vegetables. Prefer not to consume much of protein rich foods. Protein is hard to digest in the high altitudes.
• Keep yourself fit by doing some mild stretching exercises after the hike. 
• Sleep at a lower altitude if you have ascended 1000 feet or more in a day
• Do not ascent fast. Slow ascending will help you fight AMS
• Take short rests in frequent intervals while hiking.
• Do not take stress while ascending. Enjoy nature, keep chatting with your co-trekkers and ascend.
• Take a course on Acetazolamide (if required)

Acetazolamide helps you to acclimatize in the higher altitudes. I suggest, if you are climbing to 12500 feet and above, you may start the course of Acetazolamide. 250 mg Acetazolamide tab should be taken once a day starting 24 hours prior to the start of the trekking. The course completes 24 hours after your trek ends.- said Dr. Maiti

Caution: Acute Mountain Sickness may strike any experienced trekker. Everybody irrespective of beginners or experienced, are prone to AMS the moment they ascend to 8000 feet and above. 

You may also read: Beginners Guide to Himalayan Trekking-I

Acute Mountain Sickness treatment on the slopes

Follow are the golden rules to be followed in case of any emergency related to AMS:

• Do not panic as you are aware about the reason for the sickness
• The most important decision is to inform your trekmate and trek leader about your symptoms.
• Do not ascend till the symptoms vanish. 
• Eat adequate food and drink a lot of water. Do not smoke or drink alcohol.
• Do not exercise and remain on total rest.
• If you feel sick and have a headache, take some related medicines like P650 etc.
• In most of the cases, the victim will feel better within a day. If not, the only option left out is to descend. The quicker you descend, the earlier you will start feeling better. After the symptoms disappear, you can again start ascending.

Self-treating Acute Mountain Sickness is simple. There are no specific medicines to be applied for the sickness. For excessive sickness and body ache, you can take paracetamol. For reducing vomiting tendency take Promethazine (Avomine) or Ondansetron (Ondem) tablets. The only medicine to get rid of AMS is taking rest and drinking a lot of water. However, till the time the symptoms disappear, one should not ascend. Ignoring the sickness and ascending may lead to HAPE – said Dr. Maiti

High Altitude Pulmonary Edema (HAPE)

HAPE is a life threatening situation because there is fluid accumulation in the lungs. Ignoring the AMS symptoms and ascending to greater heights results in HAPE. However, HAPE can also occur without actually having the symptoms of AMS too.

Caution: Like AMS, HAPE can affect you at any altitude above 8000 feet.

The basic cause of HAPE is again supply of inadequate quantities of oxygen to the lungs. The symptoms are normally same to the symptoms of AMS with some added problems like:

• Shortness of breath even at rest
• Cough
• Massive weakness
• Congestion in the chest
• Severe fatigue

The cause of HAPE is not always necessarily rapid ascending and non acclimatization. Pneumonia, excessive exercising in high altitudes and pre-existing problems related to lungs may also contribute to HAPE – Dr. Maiti

What will you do if you have HAPE symptoms on the slopes?

• The first rule is to follow all the rules related to AMS as mentioned above.
• If required, supplementary oxygen has to be provided
• Strictly, no ascending
• The earlier you descend, the better is the situation for you.

“Immediate attention is required if any trekker has the symptoms of HAPE. Every high altitude trekking group should carry oxygen cylinders. The victim should be put through supplementary oxygen if the cough and chest congestion increases. It is a must that the victim should be moved to a lower altitude at the earliest else it might become a life threatening situation for the victim.” – Dr. Maiti

High Altitude Cerebral Edema (HACE)

HACE is the extreme level of Acute Mountain Sickness. As the name suggests, the illness affects the brain of the person. Affected by HACE, the victim will

• Lose all control of bodily movement
• Gradual change in mental status
• Extreme tiredness

Normally HACE effects in extreme high altitudes. Cases of HACE, although rare, have also been found in altitudes close to 10000 feet.

It is very difficult to recover a person suffering from HACE. Within a few hours, with a limit to maximum 24 hours, the illness can headway to coma and ultimately death as a result of brain swelling. – Dr. Maiti

The symptoms related to HACE are:

• All symptoms related to AMS
• Confusion in decision making
• Becoming unconscious frequently
• Rapid heart beat rate
• Losing control over body movements
• Drastic change in the mental state

What will you do if you have HACE symptoms on the slopes?

Practically, there is no such way to deal with HACE. The only way out is to descend as fast as possible after applying supplementary oxygen to the victim. In addition to oxygen therapy, a portable hyperbaric chamber (Gamow Bag) is also used as a temporary measure in the treatment of HACE.

Quick descent for a victim affected with HACE is literally impossible considering the altitude where the victim normally gets affected. This is one of the reasons people suffering with HAPE & HACE die on Mt. Everest. In critical situations, to buy time for the victim, Acetazolamide and Dexamethasone are advised to them – Dr. Maiti

Great!! By this time I am sure you have gained enough knowledge on the different mountain sickness types, their symptoms and their remedy. Acute Mountain Sickness, HAPE or HACE can beat anybody, irrespective of their trekking experience and fitness status. We the trekkers can only remain aware about the symptoms and take preventive actions while on the slope. Rest, we need to depend on our fortune for the successful completion of the expedition and come back healthy. Although Acute Mountain Sickness is common, the occurrence of HAPE and HACE to trekkers trekking at heights of below 16,000 feet are quite rare.

You may also read: Roopkund- The Skeleton Lake of India

I would like to thank Dr. Aniruddha Maiti for helping me with the valuable information on Acute Mountain Sickness, HAPE & HACE. Many of these informations are new to me and I expect people reading this blog to make sure you take Mountain Sickness seriously on the slopes while trekking.

Some frequently asked questions on Acute Mountain Sickness

Q. What are the types of Acute Mountain Sickness?

A. Sickness in the high altitues are divided into- Acute Mountain Sickness(AMS), HAPE(High Altitude Pulmonary Edema) and HACE(High Altitude Cerebral Edema)

Q. How do you treat Acute Mountain Sickness?

A. If you fee you are a victim of Acute Mountain Sickness, stop ascending immediately. Drink lots of water and take rest. If the symptoms vanish, ascend gradually, else keep descending till the symptoms are nil. It is always safe to use Diamox before you start ascending. This will recuce the chances of Acute Mountain Sickness.

Q. What is the main cause of Acute Mountain Sickness?

A. Ascending rapidly thereby not giving your body enough time to acclimatize with the change in oxygen percentage in the air causes Acute Mountain Sickness.

Q. What are the symptoms of Acute Mountain Sickness?

A. Headache, Nausea, Loss of Apetite, Fatigue and Vomiting are the most common symptoms of Acute Mountain Sickness.