Cutting healthcare costs with wireless

Bluetooth Low Energy may be just what the medical sector needs

BY ALF HELGE OMRE
Nordic Semiconductor
Trondheim, Norway
http://www.nordicsemi.com

Medical authorities are crying out for practical wireless health-monitoring devices that patients can wear while living normal lives at home. The body-worn wireless sensor networks (WSNs) — using inexpensive, low-power, interoperable, interference-immune wireless sensors communicating with a cell phone and cellular network — could allow ill people to retain independence while being constantly in contact with their healthcare providers.

The wishes of medical authorities are hardly surprising considering that the August 2008 ON World Inc. report “Wireless Sensor Networks for Healthcare” concluded that the use of body-worn WSNs could save the healthcare industry $25 billion a year in direct costs by 2012. These savings are likely to become even greater as chronic diseases related to obesity and a graying population become more common.

Wireless connectivity has not, to date, been enthusiastically embraced by the medical sector because the sector presents some stringent demands that haven’t been met by existing proprietary or standards-based technologies.

The demands are driven by the need to guarantee that the technology does not increase the risk to a user’s health and is totally reliable and include:

• Interoperability . An open standard is vital – proprietary systems need not apply.• Sensors . Must be accurate and reliable, incorporate simple pairing, be plug & play, and feature auto-recovery.• Ultra low power and long battery life . Sensors require a low power RF radio with streamlined protocol so they can run for months or even years on a coin cell battery.• System and device security . Transmission of data must be secure to keep medical data confidential.• Distribution network . Sensors need to communicate with services such as the Internet and the cellular network so that information can be relayed to remote health practitioners.• A compelling case for adoption . Healthcare institutions are very conservative and need a convincing argument to take up new technology.

Bluetooth Low Energy meets the challenge

Bluetooth Low Energy will meet all of these demands. This short-range ultra-low-power 2.4-GHz wireless technology is an extension of the Bluetooth technology that has become almost ubiquitous in cell phones and personal computers.

Due for ratification in late 2009, the Bluetooth Low Energy specification will detail a communication technology with a lightweight protocol stack. The integration with “classic” Bluetooth will require the adoption of a new generation of dual-mode Bluetooth chips that are currently under development by major semiconductor manufacturers (see Fig. 1 ).

Fig. 1. Bluetooth Low Energy wireless has dual-mode and single-mode implementations.

Because Bluetooth Low Energy’s protocol stack has been kept streamlined, the radios consume around 15 mA for the short periods (because only small amounts of data are sent) required to transmit or receive, tens of microamps in standby mode, and around 900 nA in deep-sleep mode for an average power consumption in the microampere range. (The Bluetooth Special Interest Group’s (SIG) provisional figures for Bluetooth Low Energy are 15 mA when transmitting/receiving, tens of microamps in standby mode and around 900 nanoamps in deep sleep mode). The technology supports strong AES encryption vital for secure medical data.

Moreover, its open standard ensures that sensors from different manufacturers will interoperate. And, because Bluetooth Low Energy builds on the legacy of Bluetooth, it will easily form body worn WSNs with several sensors — for example, measuring arrhythmias, blood glucose, pressure and oxygen levels, and pulse rates — communicating with a single master device.

Apart from interoperability, Bluetooth Low Energy’s biggest advantage over rival wireless technologies is in how the data generated by the sensors get to the physician. The sensors will be able to communicate directly with the Bluetooth chip, which is now a standard fitment in most cell phones (providing the cell phone is using a next generation dual-mode Bluetooth chip adhering to the low energy specification as noted above). The handset will act as the master in an ad hoc body-worn WSN, and will ensure secure communications. No rival technology can access the established cellular network in this way.

Nordic Semiconductor plans to be the first company to release single-mode Bluetooth Low Energy chips meeting the version 1.0 specification. The company recently announced the forthcoming release of its µBlue products (see Fig. 2 ). µBlue is a single-mode Bluetooth Low Energy solution supporting applications that can run on coin cell batteries for months to years.

Fig. 2. Nordic’s forthcoming µBlue single-mode Bluetooth Low Energy controller/transceiver can run on coin cell batteries.

The µBlue nRF8001 is scheduled to be generally available second half 2009. µBlue is suited to ULP medical sensor applications (and other applications in the consumer, sports, and industrial sectors).

Not tomorrow, but soon

While Bluetooth Low Energy is the only wireless technology capable of meeting the demands of the medical community for reliability, security, and interoperability, there are still some challenges to overcome. For example, while it’s an impressive achievement, the cellular network is not perfect. Coverage is less than total, especially in areas that are sparsely inhabited.

And even where the network is fully developed, calls can be dropped. That’s annoying when talking to a friend, but it’s a bit more serious for a heart disease sufferer whose wireless sensor is trying to contact a doctor because it detects an irregular cardiac rhythm. In the home, call integrity could be ensured by relaying the sensor’s data via a wired phone, but that’s not a solution for a patient who demands full mobility.

And there are some other questions to be addressed, too. For example, before the doctor sends out an ambulance he will want to be positive that 78-year-old Martha’s blood pressure and pulse rate have risen rapidly because she’s ill, not because John, the handsome gentleman from next door, has paid a visit. ■