WIRELESS TECHNOLOGY IN MEDICAL DEVICES AND THE NEW FDA GUIDANCE

The wireless technology that is so much a part of our everyday lives has made its way into the implantable medical devices, and the FDA draft guidance was quick to follow.

In 2006, the U.S. Food and Drug Administration gave “thumbs up” for the first implantable pressure sensor that combines wireless and microelectromechanical system (MEMS) technology. This innovative device called EndoSure is manufactured by CardioMEMS, Inc. (Atlanta, GA) and is based on the intellectual property from the Georgia Institute of Technology.

Officially known as the EndoSure Wireless AAA Pressure Measurement System, the device measures blood pressure in people who have an abdominal aortic aneurysm. Ruptures from this weakening of the lower aorta rank as the 13th leading cause of death in the United States. Although doctors can treat the bulging artery with a stent graft, stents can fail, so aneurysm patients require lifetime monitoring. Unfortunately, traditional testing methods such as CT scans are expensive, time-consuming and limited in scope because they only reveal the size of an aneurysm. In contrast, the EndoSure monitors pressure inside the aneurysm sac – the most important measurement for doctors to know.

CardioMEMS also makes testing easier for both doctors and patients. About the size of a paper clip, the EndoSure sensor is implanted along with the stent graft during endovascular repair. During checkups, patients don’t need to remove clothing: Doctors merely wave an antenna in front of the patient’s chest, and low-power radio-frequency waves activate the EndoSure system, relaying pressure measurements to an external receiver and monitor.

The FDA based its 510(k) clearance on the results from an international clinical study involving more than 100 hospital patients in the United States as well as Brazil, Argentina and Canada.

With CardioMEMS already extending its core technology to other applications such as devices to help hypertension patients monitor their condition at home and adjust medication accordingly or sensors that measure intracardiac pressure in patients with congestive heart failure, the use of wireless technology in medical devices is here to stay.

The FDA is obviously of the same opinion as supported by the January 3, 2007 issued guidance on the use of radio-frequency wireless technology in medical devices. The “Draft Guidance for Industry and FDA Staff; Radio-Frequency Wireless Technology in Medical Devices” covers wireless coexistence, performance, data integrity, security and electromagnetic compatibility. The FDA advices the industry to consider the above issues in all stages of the product life cycle and include them when preparing pre-market submissions.

While FDA finds a wired connection to be more reliable than a wireless connection, the guidance takes into consideration an increasing use of Radio Frequency (RF) wireless technology in medical devices and proposes ways to address related concerns. Specifically, the scope of the new guidance covers potential effects of RF wireless technology in and around medical devices on the ability of devices to function properly and the resultant safety of patients and operators. FDA recommends addressing the following issues:

Performance of wireless functions
Wireless coexistence
Wireless quality of service
Integrity of data transmitted wirelessly
Security of data transmitted wirelessly and wireless network access
EMC.

Performance of Wireless Functions:
A wireless receiver or transmitter of a medical device operates in a so-called “exclusion band” (passband) of RF frequencies. As such, medical electrical equipment would be exempt from the electromagnetic compatibility test requirements under the present IEC 60601-1-2:2001 standard. However, it is still necessary to assess if the wireless link will operate properly in the presence of EMD. FDA recommends that manufacturers describe in a pre-market submission the type of testing performed and results verifying that wireless functions will operate safely and effectively in the intended use environment.

Wireless Coexistence:
Each type of wireless technology faces coexistence challenges. FDA considers the limited amount of RF spectrum available and potential competition among wireless technologies for the same spectrum to be key contributors to a wireless medical device’s safety and effectiveness. Current RF wireless technologies include:

47 CFR Part 15 (Federal Communications Commission (FCC Part 15) devices
Wireless Medical Telemetry Service (WMTS)
cellular (mobile) telephones
wireless handheld computers and personnel digital assistants (PDAs)
wireless local area networks (WLAN 802.11.a/b/g)
wireless modems for laptop computers
personal area networks including 802.15.1 (Bluetooth), 802.153a (ultrawide band) (UWB), and 802.15.4 (Zigbee)
RF identification (RFID).

FDA recommends that manufacturers address the selection of appropriate RF wireless communication technologies in the design and development process, and include it as part of the risk management process.

Wireless Quality of Service:
What we find as the acceptable quality of service of cellular networks for voice communication may not be sufficient for medical functions. Connections lost without warning, failure to establish connections, or even slight degradation of service can have serious consequences, especially for wireless transmission of critical medical device alarms continuous physiological waveform data, wireless control of therapeutic devices and others.

Integrity of Data Transmitted Wirelessly:
Many RF wireless devices use the industrial, scientific, and medical (ISM) frequency bands such as 2.4GHz, and these can incorporate technology to minimize interference and data errors or corruption. However, wireless coexistence and data latency remain concerns because the data transfer rate can slow slightly or even dramatically with an increase in the number of similar transmitters in a given location. In many cases it is essential that medical data, including real-time waveforms and critical control signals and alarms, be transmitted and received without error.

Security of Data Transmitted Wirelessly and Wireless Network Access:
Security is a concern in the use of RF wireless technology because it can be easier for unauthorized eavesdropping on patient data or unauthorized access to hospital networks to occur.

Electromagnetic Compatibility (EMC):
FDA recommends for electromagnetic compatibility (EMC) to be an integral part of the design, testing, and performance for RF wireless medical devices. While as noted above, RF receivers are exempt from the EMC testing requirement indicated in the IEC 60601-1-2:2001 standard, FDA recommends either to follow the standard or perform other testing to demonstrate the wireless function will operate as intended in the expected environment of use.

The "Draft Guidance for Industry and FDA Staff; Radio-Frequency Wireless Technology in Medical Devices" can be accessed at www.fda.gov/OHRMS/DOCKETS/98fr/06d-0504-gdl0001.pdf.

The agency is accepting written or electronic comments on the draft guidance until April 3.

If you have comments regarding this update, please contact Romil Rambhia at 516-482-9001 or email at romil@mdiconsultants.com

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