High climbers record lowest blood-oxygen levels ever
For the first time, measurements of blood-oxygen levels were taken in climbers near the top of Mount Everest. This feat was accomplished by an expedition led by doctors from the University College London in the UK. Their results were recently published in the New England Journal of Medicine. Mount Everest: the mere mention of its name inspires awe. Mountaineers book years in advance for the privilege of climbing to its summit. Now, a team of doctors from the University College London has succeeded in establishing a base on its slopes that will be used to conduct scientific research into the effects of the mountain's extreme conditions on human systems. Their findings will benefit both climbers and those who suffer other illnesses such as acute respiratory distress syndrome (ARDS) and 'blue baby' syndrome, among others. The Caudwell Xtreme Everest team comprised doctors who were experienced mountain climbers. They trekked 8,400 metres above sea level and made blood measurements, using blood drawn from leg arteries, close to the mountain's summit. The researchers established in practice what has long been theorised: that high-altitude climbers have incredibly low levels of oxygen in their blood, which at sea-level would only be seen in patients close to death. The team made the trek with oxygen masks which they removed 20 minutes before the test so as to equilibrate their lungs with the low-oxygen atmosphere. With temperatures reaching -25°C and winds above 20 knots, they were unable to conduct the tests at the summit; retiring to a safer site below but still close to the summit was a necessary safety precaution. Once they reached their new destination they removed their gloves, unzipped their down suits and drew blood from the femoral artery in the groin. Blood collected from four team members was then carried back down the mountain to be analysed within two hours at a science laboratory set up at the team's camp at 6,400 metres on Everest. The normal average arterial oxygen level in humans is between 12 and 14 kPa and patients with a level below 8 kPa are considered critically ill. The expedition's samples showed levels averaging 3.28 kilopascals (kPa), with the lowest value being 2.55 kPa. Because the values they found were so far below what they expected, the scientists speculated that accumulation of fluid in the lungs as a result of the high altitude might have contributed to the low oxygen levels. The expedition was led by Dr Mike Grocott, a UCL Senior Lecturer in Critical Care Medicine, who commented: 'By observing healthy individuals at high altitude where oxygen is scarce, we can learn about physiological changes that can improve critical care at the hospital bedside, because low oxygen levels are an almost universal problem in critical care. These extraordinary low levels of oxygen found in high-altitude climbers may cause doctors looking after critically ill patients to revaluate treatment goals in some patients who have been ill for some time and might have adapted to low levels of oxygen in the blood.' However, caution should be exercised when interpreting the study's results. 'Our findings will need further careful evaluation before they can be translated into clinical practice,' said Dr Grocott. 'We hope that ongoing research will eventually lead to better treatments for patients with acute respiratory distress syndrome, cystic fibrosis, emphysema, septic shock, blue baby syndrome and other critical illnesses.'
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