A preliminary assessment of EMI control policies in hospitals

The use of wireless devices around critical-care medical equipment poses the risk that the electric field strength will exceed the immunity of the equipment, potentially resulting in equipment failure and possibly harming the patient. As medical staff and visitors carrying wireless transmitters move through the hospital, there may be times when number and type of transmitters near a medical device produce an electric field that exceeds the equipment's immunity level. This paper presents a method for estimating the risk that the immunity level will be exceeded from wireless transmitters carried by medical staff throughout a 24-hour period. The method is applied to a simplified scenario of three patients in beds and twelve transmitter locations surrounding the beds, with eight medical staff on the floor. The risk of electromagnetic interference can be reduced with a suitable management policy. This paper describes a method for evaluating the usefulness of a management policy quantitatively, and then compares three policies: unrestricted use of wireless devices, restricted use, and a ban on wireless devices.