Documenting Radiated Electromagnetic Field Strength in the Hospital Environment

Abstract

Electromagnetic interference (EMI) in the hospital environment can cause medical devices to malfunction and poses a significant risk to patient safety. The purpose of this work was to document radiated electromagnetic (EM) field strength levels found in different areas of the hospital. Field strength measurements were made in various patient areas such as telemetry, intensive care, labor and delivery, emergency rooms, and operating rooms. Electric and magnetic field strength levels were highly dependent on environmental conditions within the hospital. Local sources present in a specific area (i.e., medical and communications equipment) were primarily responsible for field strength intensity in a given location. However, it was also determined that the hospital proximity to external transmitting antennas could affect ambient field strength in certain areas. In some cases, these field strength measurements exceeded the radiated EM immunity levels specified in the International Electrotechnical Commission (IEC) Standards for medical device electromagnetic compatibilitv (EMC).10–12Generally, medical devices must be able to withstand exposure to the field strength levels typical of the different environments in which they may be used. Therefore, the environment in which a medical device is used must be considered in the assessment and mitigation of EMI. This study was performed to document these environmental conditions and field strength levels in the hospital. The findings of this work show that 63% of all electric field strength measurements and 7% of all magnetic tield strength measurements collected in the hospital exceeded the proposed IEC immunity requirements for medical devices. Index under: electromagnetic environment, electromagnetic interference, EMI, radio-frequency interference, RFI, electromagnetic compatibility, EMC, medical device immunity, medical device emissions