Medical Electronic Equipment

Heath facilities including hospitals, surgeries, GP practises, veterinarian clinics, dentists etc. use a variety of electrical equipment. The equipment ranges from specialist medical, laboratory and IT equipment to ordinary domestic appliances.

Any electrical equipment for the purpose of treating, monitoring or diagnosing a patient’s condition is classed as a medical electronic device according to IEC 60601, the global harmonized standard governing the design and
approval of medical devices.

The official definition of medical electrical equipment according to IEC 60601 is:

“Electrical equipment, designed for treatment, monitoring or diagnoses of patients, powered from not more than one connection to mains supply and which are necessarily in physical or electrical contact with the patient or transfers energy to or from the patient or detects such energy transfer to or from the patient.”

Medical and non-medical electronic equipment can also be combined into a medical electronic system. To ensure safety of patient and operator, this system must meet the design requirements of IEC 60601.

The definition of a medical electronic system is;

“Combination of equipment of which at least one is classed as medical electrical equipment and as such specified by the manufacturer to be connected by functional connection or use of a multiple portable socket-outlet.”

Commonly used terms and definitions in IEC 62353 / 60601

Equipment under test

The equipment (EUT) which is the subject of testing.

Device under test

The device (DUT) which is the subject of testing.

Applied part

Part of the medical equipment, which is designed to come into physical contact with the patient, or parts that are likely to be brought into contact with the patient.

Patient connection

Individual physical connections and / or metal parts intended for connection with the patient, which form (part of) an applied part.

Patient environment: Volumetric area in which a patient can come into contact with medical equipment or contact can occur between other persons touching medical equipment and the patient, both intentional and unintentional. (See appendix D)

F-Type applied part

Applied part which is electrically isolated from ground and other parts of the medical equipment. i.e. floating. F-Type applied parts are either type BF or type CF applied parts.

Type B applied part

Applied Part complying with specified requirements for protection against electric shock. Type B applied parts are those parts, which are usually ground referenced. Type B are those parts not suitable for direct cardiac application.

Type BF applied part

F-Type applied part complying with a higher degree of protection against electric shock than type B applied parts. Type BF applied parts are those parts not suitable for direct cardiac application.

Type CF applied part

F-Type applied part complying with the highest degree of protection against electric shock. Type CF applied parts are those parts suitable for direct cardiac application.

Class I*

Equipment protection against electric shock by (grounded) additional protection to basic insulation through means of connecting exposed conductive parts to the protective ground in the fixed wiring of the installation.

Class II*

Also referred to as double insulated. Equipment protection against electric shock is achieved by additional protection to basic insulation through means of supplementary insulation, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor and no reliance upon precautions to be taken in the fixed wiring of the installation.

*not to be confused with FDA classifications

Protective ground

Dedicated circuit intended to carry the fault and leakage current in class I equipment and to be connected to the protective ground terminal.

Functional ground

Dedicated circuit intended to provide an electrical screening and to be connected to a functional ground terminal.

Live to ground voltage

Applied voltage between the live wire and ground conductor, affecting the leakage current.

Leakage current

Current that is not functional.

Macro shock

Non-invasive applied current which passes from one side of the body to the other, typically hand to hand or hand to foot, and therefore crossing through the heart.

Micro shock

Invasively applied current which passes directly across the heart tissue.

NOTE: Class II equipment may be provided with a functional ground terminal or a functional ground conductor.

Symbols and Markings

The IEC 60601 defines the requirements for information / data to be present on the medical equipment's nameplate, in order to form an unambiguous identification of the equipment.

Information must include; manufacturers name, model number, serial number, electrical requirements etc.

The IEC 60601 standard refers to a large variety of symbols for use on medical equipment, medical systems, accessories and other related parts. A full overview of the symbols used in IEC

60601 is provided in table D1 of the standard.

For the purpose of this article, a selection of the most commonly used symbols is displayed below.

Product Lifecycle

For many years, ME equipment has been subject to extensive approval processes from clinical trials, to type testing all the way through to end of production line testing, to ensure it operates properly before leaving the factory. In addition, manufacturers recommend that regular electrical safety and essential performance checks are carried out to ensure there’s no risk of harm to the patient and operator once the device goes into service.

Fig.5 Safety stages through a product lifecycle

Fig5 Safety stages through a product lifecycle

R&D	During this stage a concept is subject to initial & clinical trials. Electronic and mechanical design of the product (where applicable) must be in line with the IEC 60601 standard.
Type Testing	During this stage the product is expected to have completed the clinical trials and subject to type testing is ready for marketing. The hardware and software of the product is verified against the design standards. When CE marking is obtained, the medical product can be marketed.
Production	During this stage the products are being assembled, tested and inspected for release into the market place.
Acceptance	Once a medical device reaches the client, an acceptance test is performed. This test is to verify that the device is delivered in an acceptable condition, complete without any defaults and available with all specified accessories. A performance and electrical safety test are often completed as part of a reference for future maintenance.
Preventative Maintenance	(Planned) Preventative Maintenance or PPM is a process whereby the device is subject to scheduled inspections and tests, in order to verify that the safety and operation are within acceptable levels and criteria. This is referred to as pro-active maintenance.
Repair Maintenance	Should a device create a fault or require an upgrade, the device will be susceptible to further inspections and testing. This is referred to as re-active maintenance.
Decommissioning	At the end of a product lifecycle, is the decommissioning stage. The device, depending on its function and material content may be required to follow a set process (i.e. An environmentally hazardous product will need to follow a recycling process. Under certain conditions, the device can be made available to other organizations in which a second lifecycle can start at the acceptance stage.