10 May 1998

High Blood Pressure Leads To Evacuated Trousers

It's difficult to imagine what kind of catwalk could accommodate the latest fashion to be adopted in the search for blood pressure conditions leading to stroke. Astronauts in zero-gravity wear special evacuated pants that reduce air pressure, pulling the blood to their legs and mimicking the effect of gravity. By using these 'trousers' doctors could discover which patients are susceptible to stroke, according to Dr John Absher, assistant professor of neurology at the Wake Forest University Baptist Medical Center, presenting the results of a small-scale study today.

Sealing off the lower body in a plastic drum, Absher used a vacuum to lower pressure inside the drum. This in turn lowered pressure in the brain by pooling blood in the legs. PET scan images of blood flow in the brain were taken during stages of pressure reduction around the legs of patients. The test was stopped as symptoms began, blood flow returning to normal in 10 seconds. Absher compared the technique to the standard treadmill test for heart disease patients in which the test is stopped when the patient shows signs of interrupted blood flow. "It's a safe and reproducible way to see what happens when blood pressure drops. We know we have 25 per cent of people who have high blood pressure and even though we are treating these people with medication to lower their blood pressure, some of them continue to have strokes," said Absher.

Until now doctors have not known how low they could go: "This technique may be able to help us do that."

The American Heart Association estimates that 50 million Americans have high blood pressure, the leading factor for stroke. Half a million Americans suffer stroke every year - it is the third leading cause of death and the leading cause of disability in the U.S. The damage is done when a blood vessel to the brain is blocked by a clot or haemorrhage, preventing oxygen reaching the brain.

Wearing interesting trousers for the purposes of medical research is infinitely more appealing than disability, and may catch on for health purposes. Having one's circulation enhanced mechanically provides the "vascular conditioning" that working-out may never achieve.