Integration of information technology into healthcare:
roleS OF WIRELESS AND ad-hoc immunity testing

Bernard Segal
Departments of Otolaryngology, Electrical & Computer Engineering, Biomedical Engineering
McGill University, SMBD-Jewish General Hospital,
Montreal, Canada H3T 1E2

Abstract: Information technology can improve healthcare efficiency and prevent medical errors, but wireless information technology will likely be crucial to help do this best. However, increased wireless usage must not cause electromagnetic-interference medical-device malfunctions. Ways to reduce electromagnetic-interference risks are overviewed. The importance of ad-hoc testing in reducing this risk is summarized, as are ways to improve such testing.

INFORMATION TECHNOLOGY AND HEALTHCARE

Information and healthcare are inseparable, because information is used throughout the healthcare system. In the past, such usage has primarily included paper-based systems (charts, mail), wired telephones, and even public-address systems. 

Recently, it has become apparent that healthcare needs integrative computerized informatics systems -- to improve healthcare delivery, by increasing its efficiency and by reducing accidental deaths in hospitals due medical errors. Surprisingly, such medical errors are said to result in more deaths than those due to heart disease, car accidents, or AIDS [1]. However, maximal increase of efficiency, and maximal reduction of medical errors, requires mobile data, which is likely best provided by wireless information technology. A wide range of new radio-frequency (RF) telecommunication devices (e.g., mobile computers on wireless local areas networks, wireless mobile tablets) has been, and will continue to be, developed to provide this capability. However in the past, wireless communication in hospitals was sometimes unsafe, causing medical-device electromagnetic interference (EMI) that has led to inappropriate patient therapy, patient injury, and even patient death [e.g., 2]. Clearly, the required increased wireless-informatics usage must take place without compromising patient safety.

This paper will overview how to safely implement integrative wireless information technology in healthcare.

IMPLEMENTATION OF wireless informatics

Implementation of integrative wireless-information technology should typically have 2 stages. First, a wired informatics system should be implemented, ensuring that real user needs (useful, easy) are met, and that the implementation is cost-effective, secure and reliable. Second, a wireless informatics system should be implemented, possibly in parallel with the first stage. The RF-wireless system must preserve patient safety, by ensuring electromagnetic compatibility (EMC) between wireless sources and life-supporting critical-care medical devices.

Procedures to use wireless safely are well known [2-6]. All hospitals should develop a wireless-EMC policy appropriate for their hospital. This policy should include three groups of recommended [3] activities: (1) Management of RF sources and susceptible medical devices,   (2) EMC Education, and (3) Estimation of immunity of existing medical devices. An outline of these activities follows; details have been described elsewhere [e. g., 2, 3]. 

1. Management of RF sources &life-support medical devices

Management of RF sources and medical devices is based on using RF sources having minimal transmission power, using medical devices having maximal immunity, and separating RF sources from medical devices as much as possible. Generally, zones should be established where only suitably-approved RF sources and medical devices are permitted. Also, personnel should maintain minimum separations between RF sources and medical devices, so that RF-source fields never exceed medical-device immunity. Procedures should be established for reporting, investigating and documenting suspected EMI occurrences.

2. Education

Education is essential to minimize EMI risk in healthcare. It should be directed at many groups, including hospital administrators, medical and non-medical hospital staff, as well as users of RF sources, or of susceptible medical devices. Seminars, preferably with demonstrations, should teach medical staff about relevant EMI issues.

3. Estimation of EMI immunity of existing medical devices

The immunity of most medical devices in use today is largely unknown. Although it is unfeasible to measure the full-frequency-range immunity of all existing medical devices, it is realistic to estimate their immunity by using ad-hoc testing [e.g., 7], procedures that assess immunity to specific frequencies radiated by particular RF sources that are likely to operate nearby. Such testing cannot ensure immunity to all potential EMI sources, but the procedure is likely to identify unusually susceptible medical devices that are highly susceptible at multiple frequencies.

APPLICATION: IMPORTANCE OF AD-HOC  TESTS

Consider how a hospital seeking to minimize medical errors might introduce a wireless-informatics system into a critical-care area, applying the above recommendations. A “critical-care-wireless zone” would be established, where only approved RF sources and medical devices would be permitted. To maximize patient safety, the new Medical EMC Standard IEC 60601-1-2 recommends [8] separations about 3 times those required in free-space environments (Table 1). To maximize wireless mobility near medical devices, minimal separations should be minimized, by appropriate selection of RF sources and medical devices. Ideally, very-low-power RF sources, say 10-mW, and high-immunity medical devices,  say 10-V/m, should be used, which would allow RF source operation to within 23 cm of medical devices.  

TABLE 1
Separations between RF sources and medical devices:
IEC triple-free-space requirements compared to free-space

RF Power (mW)	3 V/m Device		10 V/m Device
	IEC  separation (m)	Free-space separation (m)	IEC separation (m)	Free-space separation (m)
10	0.8	0.2	0.2	0.1
125	2.7	0.8	0.8	0.2
600	5.9	1.8	1.8	0.5

However, many hospitals may be unable to implement these ideal conditions. First, the immunity of available medical devices might be unknown. Second, only higher-power RF sources may be available, having associated larger minimal separations and resultant reduced mobility due to their inability to come close to medical devices. In some cases, such safety considerations would preclude selection of some sources. For example, a 600-mW source could not be brought closer than 5.9 m from a 3-V/m medical device.

Ad-hoc immunity testing would be crucial in trying to resolve these problems. Such testing can approximately estimate minimal-separation distances when equipment immunity is unknown. Also, such testing might indicate that a device’s immunity at frequencies employed by a particular higher-power RF source is higher than the device’s rated immunity, so that smaller-minimal separations might be possible. However, great care would be required to ensure that minimal separations estimated during testing were also applicable when the device was operated in the critical-care area. Finally, ad-hoc testing might also reveal the consequences of operating RF sources closer than the IEC separations.

IMPROVED AD-HOC TEST PROCEDURES 

To provide information required to resolve the above problems, the current ad-hoc test procedure requires several improvements. First, the procedure provides meaningful free-space minimal-separation estimates only if both the ad-hoc test site and the wireless-critical care zone approximate free-space environments. Thus, there is a need for procedures that can assess the validity of this approximation in both locations. If the clinical zone did not approximate free-space, suitable correction of ad-hoc estimates of minimal separations might be possible. However, better understanding of indoor propagation would be required [e.g., 9,10]. An alternate need would be for a new ad-hoc procedure that would assess immunity and minimal separations in the clinical zone itself (i.e., in-situ testing). Clearly, many extensions of the current ad-hoc procedure are desirable.

CONCLUSIONS

Wireless can help information technology provide major benefits to healthcare, but care and research is required to best achieve this. 

REFERENCES

[1] L. T. Kohn, J. M. Corrigan, M. S. Donaldson, To Err is Human. Institute of Medicine. National Academy Press: Washington DC, 2000

[2] B. Segal, D. Davis, C. Trueman, T. Pavlasek, “Risk of patient injury due to electromagnetic-interference malfunctions: Estimation and minimization,” in Proc 2001 Inter Symp on Electromag Compat, pp. 1308-1312, 2001

[3] B. Segal, S. Retfalvi, D. Townsend, T. Pavlasek, “Recommendations for electromagnetic compatibility in health care,” Proc Can Med Biol Eng Conf Vol.. 22, pp. 22-23, 1996

[4] AAMI. “Guidance on electromagnetic compatibility of medical devices for clinical/ biomedical engineers. Part 1: Radiated RF electromagnetic energy”. Technical Information Report No. 18-1997, AAMI: Arlington, VA, 1997.

[5] S. Kelly, A. R. Ravindran, H. Grant, R. Schlegel, “Electromagnetic Interference Management in the Hospital Environment,” EMC Report 1996-1, Center for the Study of Wireless Electromagnetic Compatibility, The University of Oklahoma: Norman, OK, 1996

[6] J. M. Lyznicki, R. D. Altman, M. A. Williams, “Report of the American Medical Association Council on Scientific Affairs and AMA Recommendations to Medical Professional Staff on the Use of Wireless Radio-Frequency Equipment in Hospitals,” Biomed Instrument & Technol. Vol. 35, pp. 189-195, 2001.

[7] ANSI, Recommended practice for an on-site, ad hoc test method for estimating radiated electromagnetic immunity of medical devices to specific radio-frequency transmitters. ANSI C63.18-1997, New York: ANSI, 1997.

[8] International Electrotechnical Commission, “Medical electrical equipment, Part 1: General requirements for safety. 2. Collateral standard: Electromagnetic compatibility,” IEC 60601-1-2, Ed.2, 2001

[9] D. Davis, B. Segal, T. Pavlasek, “Electromagnetic-interference risk: statistical quantitization when using free-space minimal-separations between wireless sources & medical devices,” in Proc 1999 Can Med Biol Eng Soc Vol. 25, pp. 126-27, 1999.

 [10] D. Davis, B. Segal, D. Martucci, T. Pavlasek, “Volumetric 1.9-GHz fields in a hospital corridor: Electromagnetic compatibility implications,” in Proc 2001 Int Symp on Electromag Compat. pp. 1131-4, 2001