When computers, servers and digital storage devices began to find their way en masse into businesses and homes in the late 1970s and early 80s, industrious users figured out these systems could be linked together into local area networks (LANs) that enabled the rapid exchange of information from machine to machine. Medical technology makers are now hoping to scale this model down to the personal level by connecting wireless sensors placed on (or even under) a patient's skin to create "medical body area networks" (MBANs) that provide doctors with real-time info about their patients.

An MBAN would help hospitals and healthcare clinics better keep tabs on important health-related information, including a patient's temperature, pulse, blood glucose level, blood pressure and respiratory function. Each sensor would communicate information about the patient's body via short-range wireless signals to a small receiver (either handheld or hooked onto a bed or wheelchair) that would use longer-range wireless signals to share that information with the healthcare facility's centralized computer systems—all without the jumble of wires needed to do this today.

As new sensors are developed, these body area networks might even turn into the human equivalent of General Motors OnStar vehicle maintenance services that drivers use to proactively inform them of the need for maintenance and to call for help when lost or in an accident.

Work in Progress
Before this can happen, a lot of work needs to be done developing low-power wireless sensors (that can operate with tiny batteries) and reserving space on the wireless spectrum to ensure this potentially life-critical data has priority status so it can get where it needs to go reliably and securely.

The technologies needed to make MBANs a reality are still being developed, says David Freeman, general manager of the parameters program at GE Healthcare Monitoring Solutions. GE is one of many businesses and research organizations trying to change this by developing the wireless sensors and infrastructure needed for MBANs. Another is Intelesens, a company based in Northern Ireland that develops wireless monitoring technology that uses Bluetooth to deliver medical data from sensors to a short-range receiver and Wi-Fi to send data over even longer distances. Dublin, Ireland-based Realtime Technologies also makes wearable wireless Bluetooth sensors that could be in used as part of an MBAN.

However, using Bluetooth, a wireless communications protocol for mobile phones, laptops and video game consoles, to make body sensor networks "really falls down when it comes to battery issues," says Nathaniel Sims, a physician at Boston's Massachusetts General Hospital and assistant professor of anesthesia at Harvard Medical School.

Bluetooth requires batteries powerful enough to send radio signals between roughly one and 10 meters. An MBAN would encompass a radius of about one meter, so it could use a much smaller battery. Sensors small enough to work effectively as part of a MBAN might not have the size needed to carry a battery powerful enough to operate a Bluetooth radio for any significant length of time (without completely sapping the battery).

Batteries aside, another hurdle could be a lack of bandwidth, says Rick Hampton, wireless communications manager for Partners Healthcare System in Boston. "What everyone is looking for is an area of the spectrum that's relatively secure and that can handle the bandwidth of all the new [wireless monitoring] devices that will come online," he says.

Bluetooth's ubiquity is both a blessing and a curse. A wireless system might work well using this wireless protocol in some situations if no one else is around but may be less reliable "if someone is sitting next to you with their Bluetooth headset on," says Mike Dempsey, a senior research and development engineer at the Center for the Integration of Medicine and Innovative Technology (CIMIT), a consortium of Boston teaching hospitals and engineering schools. "This is the reason that the medical industry needs to advocate for dedicated spectrum."

Body Sensor Network Bandwidth

Healthcare providers and technology companies are pushing the U.S. Federal Communications Commission (FCC) to allocate a dedicated piece of the wireless spectrum for secure, reliable transmission of patient data. The FCC is taking this request to heart and in August began soliciting comments from the public that will help the agency determine which portion of the spectrum, if any, is needed to protect MBANs from potential interference from unlicensed mobile devices or other interference. The comment period is expected to last 90 days, after which the FCC could make a decision.

"We're working to get some spectrum set aside to help us advance low power wireless sensors that could go on the body and replace wired sensors today," Freeman says, adding he is hopeful the allocation could happen by the end of the year.

The FCC has allocated spectrum for medical devices in the past. In 2000, the agency cleared space for the Wireless Medical Telemetry Service (WMTS) that allows potentially "life-critical" equipment such as heart, blood pressure and respiration monitors to wirelessly transmit patient measurement data to a nearby receiver on an interference-protected basis. Prior to this, medical telemetry devices had been operating unprotected from interference either on vacant TV channels or on special channels reserved for low-power operation.

Since the WMTS does not have a lot of bandwidth, this piece of spectrum is reserved for only the most important signals (such as heart rate and breathing) data. This excludes sensors collecting and monitoring less critical, though still key, data, such as blood glucose levels, body temperature or pulse oximetry (the oxygenation of a patient's hemoglobin), from the WMTS.

MBANs at Home
If all goes well, look for MBANs to fall into three categories in the near future—those used to monitor a patient's general health or "wellness," those measuring the health of the elderly, and those used to monitor patients with long-term medical conditions such as Parkinson's disease or epilepsy, says Paolo Bonato, director of the Motion Analysis Laboratory at Boston's Spaulding Rehabilitation Hospital and an assistant professor of physical medicine and rehabilitation at Harvard Medical School.. He also served as chair of the IEEE Engineering in Medicine and Biology Society (EMBS) Technical Committee on Wearable Biomedical Sensors and Systems in 2008.

Bonato is watching the MBAN space with special interest, since his work focuses on technology in rehabilitation for disabled people, in particular on wearable technology and robotics. As MBAN technology matures, it might also be used to address the needs of the world's aging population and problems with healthcare costs by allowing patients to be monitored remotely (yet unobtrusively) while at home. "Some conditions could be monitored in the field," he says. "We can't put everyone in medical facilities."