Altitude Sickness

This can occur in some people as low as 8,000 feet but serious symptoms do not usually occur until over 12,000 feet. Even then it is not the height that is important, rather the speed in which you ascended to that altitude. At Winter Park we are at 9,000 feet. At the top of the mountain we are at 12,000 feet. So by definition we are high altitude. Most people can go to 8,000 feet without problem.

Causes of altitude sickness

Percentage of oxygen in the atmosphere at sea level is about 21% and the barometric pressure is around 760 mmHg. As altitude increases, the number of oxygen molecules per breath is reduced. At 12,000 feet the barometric pressure is only about 480mmHg so there are fewer oxygen molecules per breath so the body must adjust to having less oxygen. In addition, high altitude and low air pressure causes fluid to leak from the capillaries in both lungs and the brain which can lead to fluid build-up.

Acclimatisation

The main cause is going too high too quickly. Given enough time your body will adapt. This process is known as acclimatisation and generally takes 1-3 days. Several changes take place in the body which enable it to cope with decreased oxygen:

The depth of respiration increases
The body produces more red blood cells to carry oxygen
Pressure in pulmonary capillaries is increased forcing blood into parts of the lung which are not normally used when breathing at sea level
The body produces more of a particular enzyme that cause the release of oxygen from haemogloblin to the body tissues

Sometimes people breathe differently at night when asleep known as Cheyne-Stokes breathing. This is not considered abnormal at altitude but Acetazolamide is helpful with this.

Acute mountain sickness

AMS is very common at high altitude. Over 10,000 feet 75% of people will have mild symptoms. The symptoms usually start 12-24 hours after arrival at altitude and begin to decrease in severity around the 3rd day.

Symptoms

Headache
Nausea and sickness
Loss of appetite
Fatigue
Shortness of breath
Disturbed sleep
General feeling of malaise

Symptoms tend to be worse at night. Symptoms decrease with acclimatisation.

Symptoms worsening normally mean moderate mountain sickness and together with decreased co-ordination indicate that the person should be taken down to a lower altitude. Symptoms of severe mountain sickness which will include inability to walk, decreasing mental function, disorientation, shortness of breath at rest and fluid build up in lungs as well as the above indicate immediate descent to a lower altitude.

Prevention

If possible start below 10,000 feet
Do not overexert yourself for 24 hours
If you go above 10,000 only increase the altitude by 1,000 feet per day
If you begin to show symptoms do not go higher until symptoms decrease
If symptoms increase go down
Take account of the whole group
Stay properly hydrated. Drink at least 4-6 litres per day. Urine output should be copious and clear to pale yellow.
Take it easy for the first few days
Avoid tobacco, alcohol, which can worsen the symptoms
Eat a high calorie diet while at high altitude

Treatment

Either acclimatisation or descent.

Symptoms of mild AMS can be treated with painkillers for the headache, acetazolamide and dexamethasone. These help to reduce the severity of the symptoms but do not cure it.