Monitoring such parameters of bodily functions as heart rate, respiration, temperature, blood glucose, and even the heart's electrical activity (an EKG rhythm strip) does not require a very large bandwidth. A transmission capability as low as 8 bits per second, and an 8-bit microprocessor can accomplish this. FitSense created a low-power (microwatt) local area network (LAN) to handle multiple wireless sensors attached to clothing or jewelry (FitSense Technology Corporation Inc., 2005).
There are several devices currently available that monitor heart function and transmit data in real time to a monitoring station. These device include both externally worn and implantable monitors. EKG monitors consisting of one to three leads that are no larger than a music tape cassette can monitor heart rhythm and transmit information by landline, cellular, or satellite phone. Small, light, battery-powered Holter monitors are also available. Implantable cardiac pacemakers employ low-power sensors to measure heart rhythm and deliver a counter shock when a dysrhythmia is noted. These devices have been limited to employing 8-bit microprocessors in order to minimize heat generation during operation within the body. Conceivably, these devices could be adapted to store and forward physiological data for public health purposes (Schiller AG, 2005).
Pulse oximeters measure the degree of blood oxygenation noninvasively. Models currently available weigh a few ounces, are battery powered, and feature digital signal processing. Adding a transmitter to such devices is technically quite feasible (Nellcor Inc., 2005).
Commercial vendors sell a variety of wearable devices that are intended for monitoring human performance in clinical trial settings or exercise settings. Wrist and elbow devices manufactured by Pittsburgh-based BodyMedia, for example, measures movement, heat flow, skin temperature, ambient temperature, and galvanic skin response. A transceiver mounted on each unit allows the instrument to both transmit data in real-time to a workstation, and to receive data from another, third-party device.
Biometric gear offers great potential, but is expensive and evaluated only with small groups of volunteers thus far. Government agencies have yet to adopt these systems as standard issue.
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