The Clinical Engineer: A Ghost Hunter or Manager of EMI

The dependence in medicine on technology to deliver services is continuously growing. The number of microprocessor-based diagnostic, therapeutic, and patient monitoring devices used in the clinical environment is ever-increasing. As device malfunctions are noted and investigated by clinical engineers, increases in the number of device failures attributable to interference generated by equipment producing electromagnetic energy in the radio frequency (RF) spectrum have been documented. Warnings are issued by manufacturers and agencies that monitor the safe uses of biomedical instrumentation. For the most part, manufacturers and agencies depend on reports from institutions using the affected products. In spite of the risks to devices, and therefore to patients, many events attributable to electromagnetic interference (EMI) go unreported. The clinical engineer, educated in the causes and effects of EMI, is capable of implementing a risk-reduction program that includes training for users, environmental assessment, identification of possible sources, and mitigation of the risks (wherever possible) resulting from these conditions.

Years of research have shown that all clinical facilities, whether in urban, suburban, or rural areas, are subject in varying degree to the effects of EMI. The quantity of documented incidents of EMI affecting clinical devices may represent but the tip of the iceberg. Experiences during investigations of EMI at Texas Children's Hospital, St. Luke's Episcopal Hospital, and various other facilities indicate statistically that many events demonstrably attributable to EMI go unreported. Under-reporting appears to be caused by lack of training and knowledge in the identification of EMI-related device failures, lack of reporting structure, and concern with a potential admission of implied risk that could result in subsequent litigation.

BENEFITS OF CONIROLLING THE ELECTROMAGNETIC ENVIRONMENT

Patients as well as the facility in which they are cared for are dependent on the reliable operation of clinical devices. Reliable operation is complicated by an environment made ever more hostile by increasingly complex impinging electromagnetic fields emanating from a variety of sources. This has resulted in the increase of momentary, partial (visible and invisible), and complete failure of clinical devices due to EM!. Failure of active clinical devices increases risk to patients and reduces cost-effectiveness, because use of the device is restricted until the cause of failure can be diagnosed and corrected. Therefore, a comprehensive program for managing EMI through monitoring, education, and control has proven to be of benefit in terms of both risk avoidance and cost containment.

ROUTES TO A SUCCESSFUL PROGRAM

In order to be successful, a program for managing the risks associated with EMI must have the following elements:

• Facility commitment for the operation of a comprehensive program supported by qualified personnel and test equipment appropriate for the tasks required, including the performance of the necessary tests and analysis and interpretation of the test data.
• Qualified personnel educated in both the science and technologies related to EMI and trained in its detection and mitigation. The primary requirement is a knowledge of RF generation and propagation. One path to the attainment of the knowledge and appreciation (almost an instinct) of the nuances of RF propagation is through the pursuit of the avocation of amateur radio, a hobby that requires study and proof of knowledge demonstrated through Federal Communications Commission-sponsored examinations to attain operating privileges.
• A plan of education that includes care givers who use medical devices, security and plant personnel, and other users of hand-held radio transmitters, biomedical equipment technicians, and administrative personnel. Personnel performing educational functions should be able to describe the risk potential of EMI on devices in various clinical areas, the steps necessary to report EMI incidents, and how to mitigate the effects.
• Procedures for reporting, investigating, and monitoring incidents of EMI and their results. These procedures should include scheduled footprinting of high-risk areas and prepurchasing fingerprinting of representative types of incoming devices.
• Cooperation with manufacturers in the development of devices with higher immunity to EMI and proper maintenance procedures that sustain the properties of the devices as they relate to susceptibility to EMI.

HINTS AND KINKS: THE GIVEN OF GHOST HUNTING

Unlike most applications of maintenance of electronic and electromechanical devices, the detection and mitigation of the effects of EMI have been likened to "ghost hunting." Conventional troubleshooting techniques provide limited results when we are looking for the cause of EMI.

To be successful in the detection of EMI and the mitigation of its effects, the clinical engineer must understand and fully appreciate the following guidelines:

• Approach each instance of EMI from a fresh perspective. There is more than one way EMI can affect a device, and therefore the path to mitigating the effects of EMI varies. At Texas Children's Hospital, we have demonstrated that identical devices placed in close proximity to each other do not react identically when exposed to an RF field.
• Observe the RF environment carefully. It is constantly changing. New licenses for radio-based services are issued daily. More unlicensed devices are being added all the time. Careful observation of the current RF environment coupled with acquisition of data during an aggressive footprinting/fingerprinting program will provide a direction toward the solution of specific EMI problems.
• Involve care givers in the investigation of a device failure. Careful questioning by an educated clinical engineer can provide the engineer with valuable information about a particular EMI problem and at the same time educate the care giver in important ways.
• Understand that there may not always be a tidy solution to a specific problem. Successful detection of the cause of specific EMI will not necessarily point to a practical method of mitigating it. Sometimes alternative solutions must be sought, ranging from more aggressive supervision of the affected device when in clinical use to replacement by a device with greater irrununity to EMI.
• Find a place in the building that provides some degree of shielding from RF sources that originate outside. Appropriate locations would be basement or sub-basement areas, preferably in the center of the building, or a radiology area that is still shielded but no longer used. Such an area, after footprinting, will be the area in which individual devices will be fingerprinted.
• Maintain and repair clinical devices properly. A device might pass all bench and manufacturer's tests, but because cabinet hardware was not properly seated, it may now be susceptible to electromagnetic radiation. Or because internal spray shielding used in the control of device susceptibility is worn or otherwise damaged, the device may be more likely to affect other devices through leakage of electromagnetic radiation. Add procedures to the regular maintenance schedule that include inspection and rectification of the RF containment seals and shielding.
• Set repeatable measurement procedures based on standards such as those recommended by ANSI, IEEE, FDA, and others. Realize that RF emissions and their amplitudes are different in each facility, and therefore an institution may need to deviate from testing standards to produce a viable program of EMI management. You should know how deviation from a published test protocol might affect device performance results.

Responses by institutions have been varied and range from aggressive, adequately funded and staffed EMI reduction programs to apathy based on disbelief. The most common complaint encountered is the lack of personnel with experience in the dynamics of RF and related EMI. Following closely is lack of funding to meet the equipment requirements for successful "ghost hunting," limiting mitigation options. Last is a diminishing number of institutions that do not yet believe that EMI poses a threat to diagnostic and therapeutic clinical devices and, consequentially, risk to patients utilizing those devices. It is hoped that further education of clinical, technical, and administrative staff will further reduce the number of such institutions. Therefore, clinical engineers are faced with the challenge and responsibility to guide these institutions toward safer patient care environments.

CASE HISTORIES: MEMORABLE GHOST HUNTS

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