Cause of High Altitude Sickness
The primary cause of High Altitude Sickness is that amount of available oxygen in the atmosphere decreases with altitude. While the percentage of oxygen (21%) in the atmosphere remains constant the density of the atmosphere decreases so that the available oxygen when you take a breath becomes less. The decrease in density of the atmosphere is not linear and that density decreases more rapidly with increasing altitude so that the impact of going from 10,000 to 20,000 feet is not as significant as going from 20,000 to 30,000 feet.
Normal Symptoms at Altitude
It’s perfectly normal to have symptoms as a result of altitude which include; Hyperventilation (extra breathing), increased urination, restless sleep and Periodic breathing at night. Periodic breathing occurs during sleep and may result in you waking up and feeling you have missed a breath. Periodic breathing is also likely associated with restless sleep as your body tries to regulate itself and adjust its normal patterns.
Symptoms of High Altitude Sickness
One of the difficulties during the early stages of High Altitude Sickness is that the symptoms can be similar to other common conditions such as; dehydration, fatigue or the common cold or flu. It’s important to make the correct treatment choices and always error on the side of safety. One of the most common symptoms is the development of a High Altitude Headache. Diagnosis of High Altitude Sickness is made when a High Altitude Headache is present along with one or more of the following symptoms; loss of appetite, nausea, vomiting, fatigue/weakness, dizziness and serve insomnia. High Altitude Headache alone is not sufficient for a diagnosis and the trekker may decide to continue gaining elevation but should be on increased alertness for the development of other symptoms. If High Altitude Headache occurs along with at least one other symptom either descend in elevation or at least stay put until symptoms resolve.
High Altitude Sickness left untreated can advance to high altitude cerebral edema (HACE) or High Altitude Pulmonary Edema (HAPE). The symptoms of HACE are unmistakable as the individual will have a drunken like walk. The symptoms of HAPE are completely different and are as follows; coughing pink or frothy sputum, tightness of the chest, shortness of breath at rest, a gurgling breath as if the lung is congested, a bluish discoloration of the skin (Cyanosis) and/or an abnormally fast resting heart rate of over 100 HBM. Once HACE or HAPE develops death is possible within hours unless the trekker is immediately evacuated to a lower elevation. If someone has signs of HACE or HAPE its key that a responsible member(s) of the trekking party accompany this person to a lower elevation immediately no matter the time of day or the weather conditions.
Pulse Oximetry at High Altitude
Hand-held pulse oximeters are now commonly used in the diagnosis of High Elevation Sickness as well as HACE or HAPE. Oxygen saturation readings below 75% may be useful in the diagnosis of HAPE. A limiting factor in the use of the devices is that Oxygen saturation may remain normal as individuals tend to breathe faster at higher elevations and thus have normal readings. The common consensus is that their best use may be as a confirmation tool for someone who already has definitive symptoms of elevation sickness.
Medications to Prevent High Altitude Sickness
The most common medication used to prevent High Elevation Sickness is Diamox (Acetazolamide). This can be easily purchased on arrival in Kathmandu and a dose of 125mg twice daily starting 1 day before ascent has been suggested by the Everest Base Camp Medical Centre. If you already have High Elevation Sickness the dose can be increased to 250mg twice daily. It’s a common myth that this drug only masks the symptoms of High Elevation Sickness but it actually works to speed the natural acclimatization process by acidifying the blood and thereby stimulating the depth and frequency of your breathing.
A recent study done on trekkers in Nepal suggests that three times daily dosage of ibuprofen at 600mg may be effective at reducing high elevation sickness. The caveat here is that while it may effectively reduce the symptoms of high altitude headache it may only be masking the impact of high elevation sickness.
The Facts about Proper Acclimatization
The best rate of acclimatization is to gain no more than 300m (1000 feet) per a day. If you increase this rate you will be much more susceptible to Elevation Sickness. This should be considered based on where you sleep at night and not how high or low you trek during day. In fact trekking higher during the day and then returning to a lower elevation to sleep can speed the rate at which you acclimatize but its not an excuse to break the basic rule.
Drinking Alcohol and Coffee at High Elevation
Alcohol is a member of the benzodiazepine family and as such can suppress breathing which results in lower blood oxygen levels so should be avoided as a general rule. Coffee has no impact on acclimatization and if you typically drink several cups a day keep at it. If you are a regular coffee drinker be aware that stopping abruptly could cause a severe headache that might be confused with a high altitude headache.
Group Psychology and High Elevation Sickness
Several studies have suggested that individuals trekking in organized groups may be more susceptible to high elevation sickness. The postulated reasons are that individuals are impacted by group psychology and don’t want to cause difficulties for the group as a whole. It’s important to keep this in mind as an individual and maintain a level of self awareness. It’s better to rest a day and get proper acclimatization then deny symptoms which may result latter in an evacuation.