Keeping medical electrical equipment safe from interference

Safe operation of medical equipment is essential to protect patients and users

By Morand Fachot

Electromagnetic compatibility (EMC), the ability of electronic and electrical systems or components to work reliably and safely when they are close together is crucial in many domains, in particular in the medical environment. 

Semi automatic defibrillator Defibrillators require a special EMC Standard (Photo: Defibtech)

A general framework

International Standards, Technical Reports and Technical Specifications in the field of EMC are prepared by IEC Technical Committee (TC) 77: Electromagnetic compatibility, and its Subcommittees (SCs). These publications have a horizontal function, and are referenced by product committees.

IEC TCs and SCs refer to a number of IEC TC 77 publications, and to IEC Guide 107:2014, Electromagnetic compatibility – Guide to the drafting of electromagnetic compatibility publications, developed by the Advisory Committee on Electromagnetic Compatibility (ACEC), to prepare specific International Standards for their products. 

General and particular requirements for EMC for MEE and MES

All medical electrical equipment (MEE) and systems (MES) must meet general EMC Standards prepared by IEC TC 77. However some specific International Standards are still needed for electrical equipment in medical practice. These are primarily developed by the SCs of IEC TC 62.

IEC SC 62A: Common aspects of electrical equipment used in medical practice developed IEC 60601-1-2:2014, Medical electrical equipment – Part 1-2: General requirements for basic safety and essential performance – Collateral standard: Electromagnetic compatibility – Requirements and tests. This Standard outlines general requirements such as risk management for MEE and MES and for non-MEE used in MES, as well as normative references, electromagnetic emission requirements for MEE and MES and guidelines for tests.

IEC SC 62B: Diagnostic imaging equipment, prepared IEC 60601-2-37:2015, Medical electrical equipment – Part 2-37: Particular requirements for the basic safety and essential performance of ultrasonic medical diagnostic and monitoring equipment. This Standard does not cover ultrasonic therapeutic equipment, but equipment used for the imaging or diagnosis of body structures by ultrasound in conjunction with other medical procedures.

IEC SC 62D: Electromedical equipment, developed IEC 60601-2-4:2010, Medical electrical equipment – Part 2-4: Particular requirements for the safety of cardiac defibrillator. A defibrillator is a medical electrical equipment intended to automatically analyse and/or to normalize the rhythm of the heart by an electrical pulse via electrodes applied either to the patient's skin with external electrodes or to the exposed heart with internal electrodes. The Standard covers various components such as electrodes, charging and discharge circuits, and more.

Another International Standard that was not developed by IEC TC 62 or its SCs relates to hearing aids. Hearing aids are wearable instruments intended to aid a person with impaired hearing. International Standards for hearing aids are developed by IEC TC 29: Electroacoustics.

To ensure EMC for hearing aids IEC TC 29 developed IEC 60118-13:2016, Hearing aids – Part 13: Electromagnetic compatibility (EMC). This Standard covers requirements for electromagnetic emissions, for electromagnetic immunity, electrostatic discharge and various test procedures.

As hearing aids are operating on radio frequencies (on may be affected by RFs disturbances), they shall comply with certain requirements set out by the IEC International Special Committee on Radio Interference (CISPR) "based on their classification". These requirements and classification are contained in CISPR 11:2015, Industrial, scientific and medical equipment – Radio-frequency disturbance characteristics – Limits and methods of measurement.

Although EMC International Standards and other publications developed by IEC TC 77 cover most MEE and MES, standardization work done by the SCs of IEC TC 62 and by IEC TC 29 are still essential for specific issues concerning certain categories of medical equipment.

Doctors using ultrasonic imaging Ultrasound imaging equipment is widely used in operations (Photo: Philips)
Semi automatic defibrillator Defibrillators require a special EMC Standard (Photo: Defibtech)
Hearing aid cross section EMC is important for hearing aids (Photo Siemens)