IEC 60601 defines the requirements for medical equipment and systems regarding the safety of patients. Medical equipment includes all electrical devices used for the diagnosis, treatment, and monitoring of patients, which could be the origin of electrical current flowing to a patient. The standard places specific requirements on medical electrical systems, particularly when medical equipment is connected to building cabling by means of a network cable. Finally, the standard requires protection for patients against electric shocks, specifying the necessity of two independently operating means of protection.
Title 47 CFR 15 defined rules limiting the potential for interference to licensed operations by nonlicensed transmitters. With many medical device designs adopting 802.11, a test engineer needs to broadly understand CFR 15.247 and the limits it defines for spread spectrum devices. Supporting CFR 15.247, ANSI C63.10 is a compilation standard of measurement procedures for testing many unlicensed wireless devices for compliance with FCC rules.
The ANSI C63.18 protocol is recommended for basic testing using representative units of real-world hospital-environment critical and life support medical equipment, such as ventilators, infusion pumps, and anesthesiology machines to characterize significant EMI issues. The standard serves as a guide for healthcare organizations in evaluating radiated electromagnetic immunity of existing medical device inventories. Some facilities use ANSI C63.18 for prepurchase evaluation of medical devices.
FDA and industry groups continue to study RFID’s potential effects on medical devices. Specifically, FDA is investigating RFID’s effects on critical care medical equipment such as AEDs, ventilators, and implantable neurostimulator devices. FDA is working with manufacturers to test their products for any adverse effects from RFID and requests suppliers consider RFID interference in new product design. Georgia Tech University has published research on potential RFID interference.
Network Interoperability and Coexistence
The IEEE 1900.2: Recommended Practice for Interference and Coexistence Analysis document includes an extensive list of coexistence factors to consider during testing and recommends analysis criteria for measuring interference between radio systems. A structure for a coexistence report is also suggested. In support, the IEEE 802.19 Wireless Coexistence Working Group promotes analytically assessing each 802 standard to determine scenarios in which interference may occur. However, to satisfy risk-based product design, an analytical analysis is insufficient. Groups focused on wireless medical device RF coexistence testing have begun work to this end. The ANSI-accredited committee C63, namely C63.27, held preliminary teleconferences and meetings in 2012, while another group that has been very active and provided much research on network coexistence is the University of Oklahoma Wireless and Electromagnetic Compliance and Design Center (Tulsa, OK).