Sensors for Humans: Sensor Technology at MIT （2）

Published:2011/7/28 21:43:00 Author:Amy From:SeekIC

By Delano L. Klipstein

Wireless physiological data measurements

Phil Shaltis, research assistant in the Department of Mechani­cal Engineering, agrees. He reported a sensor in the form of a finger ring which can measure blood pressure and oxygen sat­uration levels and transmit them wirelessly to a monitoring station.

The challenge in this case is not the instrumentation technol­ogy itself, but the problem of minimizing power consumption. The data are measured on an artery in the finger. The ring itself was designed using finite element methods to guarantee reliable operation: it must not press too hard against the bones in the finser, or errors will be introduced into the readings, ultimately giving rise to incorrect measurements of blood pressure: but on the other hand, the better the ring fits, the better the signal-to-noise ratio achieved. Pressure is therefore only applied locally on the finger in the spots where the artery in question lies. The pressure itself is measured using infra­red sensors.

What can we do with a sensor like this in everyday life? This is being researched at the Massachusetts General Hospital (MGHi in Boston, located opposite MIT on the other bank of the Charles River. Similar measurement devices for these kinds of data are already used in hospitals, and although they are very advanced the)’ are also comparatively large: the ring developed at MIT is a thousand times smaller. At present it is used in parallel with traditional instruments, including at a stress EKG unit. Early results are already available: identical measurements are obtained from patients at rest, while under stress the ring sensor gives much more accurate readings and. most importantly, fewer artefacts.

Many different approaches were taken in trying to minimize the power consumption of the ring. A high modulation rate is used during data transmission to keep the transmit time as short as possible. A "sleep mode’ for the ring saves yet more power there is no need to take measurements continuously. For special applications like this one a dual-architecture processor has been developed at MIT which meets the extreme performance requirements better than conventional processors. The device also has an interesting market in the area of fitness. Once the system has proved itself in hospitals, the next project is to create a monitoring system for intensive training.

Other experiments are being carried out to record stress situa­tions while driving. There is a close relationship between brain function and cardiac activity. Stress, anger and physical tiredness are reflected in an increased heart rate. For example, a system which provided continuous medical monitoring of the driver of a long-distance coach could increase safety. As well as this sensor ring, active sensors have been placed in cuffs to be worn on the arm: so-called "wearable cuffs’. Many people require continuous monitoring of the most important body functions in order to be able to call for help quickly in case of an emergency. Another approach to monitoring such patients is to use "smart shins”, which connect together a whole network of body sensors. At present they require too much wiring to be used inconspicuously: development work is in progress to reduce the number of connections to just two (for the power supply). The power supply wires can be used simultaneously for signal transmission, forming a bus system for the data to be communicated. Such unprotected bus sys­tems are susceptible to interference, in particular to the inevitable noise. An initial analysis of the noise spectrum indicates that this idea is practical over a wide range of fre­quencies, certainly above 100 kHz.

Reprinted Url Of This Article: http://www.seekic.com/blog/project_solutions/2011/07/28/Sensors_for_Humans__Sensor_Technology_at_MIT_（2）.html

Print this Page | Comments | Reading(290)