Safety assessment of the direct sequence spread spectrum wireless local area network with a medical device

Introduction

In conjunction with the Electronic Medical Record's Computerised Physician Order Entry project, KK Hospital has participated in the SingHealth Wireless Local Area Network (WLAN) Infrastructure project to evaluate the CISCO^®Wireless network technology product. The vendor, medical device manufacturers and local medical equipment distributors would not guarantee in writing that there would be no radiofrequency or electromagnetic interference (EMI) from the 2.4 GHz and 5 GHz direct sequencing spread spectrum system (DSSS) with medical devices. The Standards, Productivity and Innovation Board are able to conduct onsite electric field measurements but could not guarantee any EMI on medical devices. Senior management at KK Hospital requested an EMI test to be conducted inhouse to determine the potential effects of the WLAN on medical devices.

Methods

The test was conducted within a vacant room in the women's ICU. Selected medical devices were representative of technology used in KK Hospital ICUs and wards. The WLAN and medical devices were set up to replicate the actual environment as closely as possible. The test was conducted on both the 2.4 GHz and 5 GHz direct sequencing frequency bandwidth at a power setting of 50 mW with two PC Notebooks. A command was executed on the two PC Notebooks to generate continuous wireless transmission between the WLAN card of the PC Notebooks and the access point in the room. One women's ICU nurse was deployed to chart and monitor the parameters of each medical device under test. The project team also checked the equipment under test at 1 or 2 hour intervals.

Results

No electromagnetic interference was detected on any of the devices under test.

Conclusion

The EMI test was only a sampling, bench-top test and should not be taken as conclusive for EMI effects of the DSSS WLAN on each medical device within the hospital. However, due diligence was exercised in conducting the EMI test and there appears to be no evidence to suggest adverse EMI effects on the medical devices tested.