CASE Medicine
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NEWS: 17th Aug 2010
The Xtreme Alps Oxygen Extraction Study

This component of the expedition is specifically designed to look at the ability of the body to extract oxygen from blood when challenged by exercise at high altitude. When oxygen delivery (the quantity of oxygen circulating in arterial blood) is reduced - such as at altitude, oxygen consumption (the amount of oxygen used by cells) is protected by an increase in tissue oxygen extraction (the amount of oxygen taken up by the tissues). This continues until a point where extraction reaches its maximum capability and oxygen consumption begins to fall. At this point, anaerobic metabolism starts to dominate as the primary mechanism for generating cellular energy. In healthy individuals such imbalance of oxygen metabolism is only seen during maximal exercise. On the expedition we therefore use exercise to increase the body?s demand for oxygen and assess how it is able to modify its ability to extract oxygen to facilitate this. In the clinical scenario of critical illness, prolonged deprivation of oxygen can lead to organ dysfunction and failure so we are using our model of exercise at high altitude in order to learn more about oxygen extraction in these patients.

Using sophisticated breath-by-breath analysis equipment, exercise bicycles and analysis of arterial and central venous blood we hope to measure changes oxygen extraction at the Margherita Hut. The Siemens arterial blood gas machine that was used on Mount Everest in 2007 has been put through its paces during this experiment. Cardiac output is measured by a non-invasive technique (NICOM). Each of the five subjects requires a central venous and arterial catheter for blood sampling. The test takes approximately three hours and requires a dedicated team of six investigators. Such experiments are rarely performed at sea level due to their complexity.

Dan Martin