When climbing to high altitude, the amount of oxygen available in the air decreases and the body must quickly acclimatise to cope with this. Failure to acclimatise can result in altitude related illnesses. Two of these illnesses in particular can affect the brain: Acute Mountain Sickness (AMS) and High Altitude Cerebral Oedema (HACE). The most common complaint at high altitude is a headache, one of the key symptoms of AMS. If this and other symptoms of AMS (feeling sick, vomiting, tiredness and sleep problems) are ignored and the affected person continues to climb then HACE may develop, leading to difficulty walking, unconsciousness, fits and even death.

Our brain research intends to look closely at why these altitude related illnesses occur in some people and how they affect the brain. We looked at brain oxygen levels at rest and during exercise using a special probe, which sticks to the head (Near Infrared Spectroscopy or NIRS). We also studied the eye?s pupil reaction times and reflex eye movements to investigate the effect of reduced brain oxygen levels. Detailed psychological tests were performed on subjects as they climbed higher and higher to see if the changes we detected with our monitors translated into a deterioration of brain function. We also took photographs of the retina (the light sensitive lining within the eye) to look for abnormal changes that may occur high on the mountain.

Combined with information from other research carried out by the Caudwell Xtreme Everest team, it may be possible to explain why some people are more prone to the effects of high altitude than others.