High blood pressure is a common risk factor for heart attacks, strokes and aneurysms, so diagnosing and monitoring it are critically important. However, getting reliable blood pressure readings is not always easy. MIT engineers believe they have the answer. Mechanical engineer Harry Asada and his colleagues have developed a prototype of a new blood pressure sensor that loops around the wrist and index finger. Just as accurate as traditional cuff devices, but much less cumbersome, the device can be worn for hours or days at a time to provide continuous monitoring of blood pressure. As a result, it can keep track of even the slightest changes in blood pressure, which can rise and fall minute by minute, to provide a comprehensive picture of heart health. "The human body is so complex, but the cuff gives only snapshot data," says Asada, who led the development of the new monitor and is also the Ford Professor of Engineering and Director of MIT's d'Arbeloff Laboratory for Information Systems and Technology. "If you get signals all of the time, you can see the trends and capture the physical condition quite well," he adds.

The device works differently than a regular blood pressure cuff. It uses a method called pulse wave velocity that measures the pulse at two points along an artery. In earlier models, the MIT engineers used the heart as one of the points, with a heart monitor measuring the EKG. However, because EKGs aren't always accurate and a heart monitor can be difficult to wear, the MIT team chose to use two points on the hand instead. This posed a different challenge: Blood pressure will vary depending upon the position of the hand. Should the hand be raised above the level of the heart, blood pressure is higher than if the hand is located below the heart. The researchers incorporated a sensor that measures acceleration in three dimensions, allowing the hand position to be calculated at any time. This resolved their dilemma.

The device is expected to be used in a variety of ways, including monitoring patients with hypertension, as well as the breathing habits of people with sleep apnea. Asada says that "eventually, doctors may be able to use data gathered from continuous monitoring to predict when a heart attack may occur." CardioSign, a company founded by a former Asada student, is currently working on commercializing the device and expects to begin clinical trials soon. Asada says that he "believes a commercial version of the device could be available within five years, once it becomes easier to use, more reliable and cheaper to manufacture."

News Release: Wearable blood pressure sensor offers 24/7 continuous monitoring MIT News  www.digg.com  April 8, 2009