Reduced Cabin Pressure, Oxygen Finds No Activation of Blood Clotting System
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Researchers simulating conditions of reduced cabin pressure and reduced oxygen levels, such as may be encountered during an 8 hour airplane flight, found no increase in the activation of the blood clotting system among healthy individuals, according to a study in the May 17 issue of JAMA.
Venous thromboembolism (blood clots in vein) has been associated with long-haul air travel, but it has been unclear whether this is due to the effects of sitting for a long time, or whether there is a relationship with some other specific factor in the airplane environment, according to background information in the article. One hypothesis has been that hypoxia (reduced oxygen in the blood), associated with decreased cabin pressure that occurs at altitude, produces changes in blood that increases the risk for blood clots.
William D. Toff, M.D., of the University of Leicester, England, and colleagues conducted a study, from September 2003 to November 2005, to assess the effects of hypoxia in conditions similar to that which might be encountered during commercial air travel, on a variety of markers of activation of the hemostatic (blood clotting) system. The study included 73 healthy volunteers who spent 8 hours seated in a hypobaric (below normal pressure) chamber and were exposed to hypobaric hypoxia, similar to the conditions that would occur with reduced airplane cabin pressure at an altitude of about 8,000 feet. Blood was drawn before and after exposure to assess activation of factors associated with hemostasis (blood clotting). Similar measurements were taken of the volunteers who also spent 8 hours seated in a controlled environment equivalent to atmospheric conditions at ground level (normobaric exposure).
The researchers found that when comparing the results between the normobaric and the hypobaric exposures, there was no significant difference in the overall change for markers of coagulation activation, including reduced fibrinolysis (normal breakdown of small, naturally occurring blood clots), increased platelet activation (mobilization of platelets, cells that promote clot formation), and increased endothelial cell activation (changes in the cells that line the interior surface of blood vessels).
American Medical Association (AMA)
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