High blood pressure constitutes one of the principal vital signs of your body and is a common risk factor for heart attacks, strokes and aneurysms, so diagnosing and monitoring it are critically important. However, with all this technology around us, getting reliable blood pressure readings is not always easy.
Visits to the doctor's office can provoke anxiety that distorts blood pressure readings, and even when accurate, such visits provide only one-time snapshots of the patient's condition. To overcome these obstacles, MIT engineers have built a wearable blood pressure sensor that can provide continuous, 24-hour monitoring.
Blood pressure does tend to change during the day. When we wake up, it typically is somewhat higher than it is after we've had a chance to sit down or .eat some breakfast. So, continuous monitoring offers a much broader image of one's cardiovascular health. The new monitor, which loops around the wrist and the index finger, is just as accurate as traditional cuff devices but much less cumbersome, allowing it to be worn for hours or days at a time.
"The human body is so complex, but the cuff gives only snapshot data," says Harry Asada, an MIT mechanical engineer who led the development of the new monitor. "If you get signals all of the time you can see the trends and capture the physical condition quite well."
Devices like this one could be used to keep track on hypertension during the whole day, as well as sleep apnea. The data gathered from this devices can be used eventually by the doctors to predict when a heart attack that may occur.
CardioSign is the company that is working on commercializing the device and hopes to start clinical trials soon. The company was launched by Asada's former student. He thinks that a commercial version of the device could be available within five years, once it becomes easier to use, more reliable and cheaper to manufacture.
The latest prototype was developed jointly with industrial sponsor Sharp Corporation, and Dr. Andrew Reisner of Massachusetts General Hospital took the lead in clinical applications and human subject tests.
No cuff required
Traditional blood pressure monitoring requires a cuff, wrapped around the upper arm and inflated until blood flow is completely cut off. The examiner then gradually releases the pressure, listening to the flow until the pulse can be detected.
With this new device for monitoring blood pressure, no cuff is required. The sensor use a method called pulse wave velocity, which allows blood pressure to be calculated by measuring the pulse at two points along an artery.
Using this method the errors due to height changes will be removed. The sensors can also be calibrated for more accurate measurements. Once the blood pressure information is gathered, the data can be transmitted via wireless Internet. This new blood pressure monitor runs on a tiny battery, about the same size as the ones that power watches.
The wearable blood pressure sensor was born from a collaboration called the Home Automation and Healthcare Consortium, which launched in 1995 and included several MIT faculty members and about 20 companies.
The project was funded by the National Institutes of Health, National Science Foundation and the Sharp Corporation.
Photos: Donna Coveney
