The body undergoes many processes to help cope with this change. At first the body will hyperventilate to try and gain more Oxygen, this in turn increases CO2 in the blood. Carbonic Anhydrase converts the CO2 to bicarbonate making the blood acidic. Acidotic blood causes breathing apnoea causing a reduction in extra oxygen intake. The reduction in oxygen intake then stimulates breathing. (Diamox can help in preventing the carbonic Anhydrase working, therefore preventing acidosis of the blood and keeping breathing stimulated without undergoing the apnoea). The body also has an increased cardiac output and an increase of haemoglobin to help transport oxygen.
Types of altitude illness:
- Acute Mountain Sickness (AMS) – most common, affecting approx 65% travellers.
- High Altitude Cerebral Edema (HACE) – if AMS is left to progress, 10% may develop this life threatening illness.
- High Altitude Pulmonary Edema (HAPE) – not necessarily preceded by AMS. Life threatening.
- AMS – Headache plus one or more of following: fatigue, loss of appetite, nausea, sleep disturbance, shortness of breath, dizziness. Normally occurs 6-10 hours after ascent. Usually benign and self-limiting and if further ascent is delayed it tends to resolve in 1-3 days.
- HACE – As AMS plus lethargy, confusion and ataxia. Usually occurs at least 2 days after ascent,
- HAPE – As HACE plus shortness of breath with exertion, and a dry cough, progressing to shortness of breath at rest. The cough may become productive with blood-stained sputum. Usually occurs at least 2 days after ascent
Be aware of the symptoms of altitude, Acclimatise slowly. Allow rest days every 3 days. Never sleep more than 300 metres higher than previous night and/or in the presence of symptoms of AMS. Drink lots of fluids and minimise exertion. ALWAYS attempt to descend if symptoms of altitude illness worsen at a altitude or if symptoms are severe. Consider Diamox as this will assist in acclimatisation. If you experienced AMS on a previous trip to high altitude it is more likely it will happen on any subsequent visits. If you have visited high altitude previously and did not suffer AMS it does not mean you won’t on subsequent visits.
- Insurance – The planned maximum altitude should be disclosed and emergency evacuation by helicopter included within the policy.
- AMS – If experiencing symptoms – REST. Most will disappear after 1-2 days. Take analgesia for headaches, consider anti emetics for nausea. If symptoms worsen descend immediately at least 500-1000m.
- HACE/HAPE – Descend immediately. Give Oxygen, Niphedipine and Dexamethasone for HAPE. Dexamethasone for HACE.
Pre-Existing Medical Conditions
Some medical conditions increase the likelihood of the traveller experiencing problems at altitude and should therefore see their GP prior to departure. These include: Pulmonary problems (COPD), cardiac disease and pregnancy.