Category: Electrical Safety
Before discussing the documentation relevant to electrical safety of medical electrical equipment, it is important to distinguish between "type tests" and routine tests.
Standards for the manufacture of equipment normally detail tests which are intended to be carried out on a single representative sample of a piece of equipment for which certification of compliance with a standard is being sought. Such tests are carried out by approved test houses under tightly specified environmental conditions. These tests are called "type tests" and are not intended for routine use. Indeed, repetition of many of the tests would certainly cause deterioration in performance and safety of the equipment under test.
Routine tests have an entirely different purpose than that for type tests. Routine tests are intended to provide good indicators to the safety of equipment without subjecting it to undue stress that would be liable to cause deterioration.
In summary then, it should be understood that International Electrotechnical Commission (IEC) or British Standards (BS) manufacturers' standards for medical electrical equipment referred to below are intended only for type testing and should not be used for acceptance, in-service or routine testing of equipment. However, any tests that are used for the latter purposes should ideally be consistent with the standards to which the equipment has been manufactured. Routine tests and test limits may therefore be derived (in modified form) from the standards, with the strict proviso that any such tests should not damage or even stress the equipment under test.
In 1963, the Department of Health and Social Security published Hospital Technical Memorandum number 8 called "safety code for electro-medical apparatus". The purpose of the document was to establish adequate standards for the design and construction of electro-medical apparatus since no other relevant national standard existed at the time. Although the document was produced essentially for the guidance of manufacturers, biomedical departments in hospitals were quick to adopt tests from the document for the basis of their own medical electrical equipment safety testing regimes. Although tests detailed in the code were type tests, many of them could be fairly easily be repeated without adverse effects on the equipment as routine tests. Performance of the electrical safety tests was made easier by the development of specialised medical equipment safety testers, specifically, the Liverpool tester. The HTM was withdrawn on publication of BS5724 part 1 (see below).
In 1979, HTM 8 was superseded by the British Standard BS 5724 part 1. This document is a comprehensive specification for safety of medical electrical equipment. Part 1 covers the general requirements, i.e. requirements common to all medical electrical equipment regardless of function. A series of part 2's detailing particular requirements for specific categories of medical electrical equipment followed publication of part 1 (see Annex 1).
BS 5724 is a far more detailed document than HTM 8, which it replaced. Like the HTM, the tests contained in the standard are type tests. Some guidance was given in the 1979 edition of the standard on recommended testing during manufacture and/or installation. Unfortunately, some routine test regimes based on BS 5724 tended to be too rigorous for such application and in some cases caused damage to equipment.
BS 5724 part 1 was revised in 1989, making it identical to the International Electro-technical Commission standard IEC 601-1: 1988. References to routine tests were made even less specific than in the previous edition. The standard was subsequently re-numbered as IEC 60601-1.
Any manufacturer obtaining compliance of an item of their equipment to BS5724 or IEC 60601 will be in possession of a uniquely numbered certificate issued by the test house verifying that fact. Compliance to the standard is a commonly used route used by manufacturers to obtain CE marking (see paragraphs at 5.6.1 below).
The third edition of IEC60601-1 was introduced in December 2005. The standard has been renamed "General requirements for basic safety and essential performance" to reflect the fact that inadequate equipment performance may give rise to hazards. The new standard is stated to replace the second edition, although it is recognised that, in practice, due to the references made to the general standard by particular standards (part twos), there is likely to be a fairly long transitionary period for compliance by equipment manufacturers.
There are some significant changes in the new standard, some of which are worth noting here.
The new standard states that the manufacturer must have in place a risk management process that complies to the requirements of ISO 14971 in order to ensure that the equipment design process results in equipment that is suitable for its intended purpose and that any risks associated with its use are acceptable.
Certain changes in terminology and numbering systems have been introduced in order to make the standard more compatible with other IEC standards, in particular IEC 60950-1 (Information technology equipment).
Collateral standards for medical electrical systems (IEC 60601-1-1) and programmable electrical medical systems (IEC 60601-1-4) have been incorporated into the body of the new standard as new clauses.
The Department of Health has, in the past, issued two stand alone documents giving detailed guidance on acceptance testing or pre-use checks on medical devices. Although both of these documents have been superseded, they are discussed briefly below because they have been used by many equipment user organisations as the basis for acceptance testing regimes, and even for routine testing regimes. Additionally, a number of manufacturers of medical equipment safety testers have incorporated protocols derived from these guidance documents into their testers' firmware.
A comparison between the test recommendations of both documents is provided in annex 2 for information.
In August 1981, the DHSS issued HEI 95 entitled "Code of practice for acceptance testing of medical electrical equipment". The document was produced partly to address the problems that had arisen due to the misapplication of type tests from BS 5724 by some NHS biomedical departments.
As indicated by the title of the document, the code of practice detailed inspection and test procedures to be performed on newly acquired medical electrical equipment before it was put into service. Inspection procedures were clearly explained and the standard acceptance test log sheet given in the appendix of the document contained references to the explanatory text.
The electrical safety testing recommendations offered in HEI 95 provided a testing regime that was effective whilst being considerably simpler than many test regimes that were developed from the recommendations of BS 5724. The reason for this is that the recommended electrical safety tests are generally applied under worst-case conditions.
Although designed as a code of practice for acceptance testing the document has been widely adopted and used as the basis of routine test regimes by hospital biomedical departments.
The document was officially withdrawn in December 1999 on the publication by the Medical Devices Agency of MDA DB9801 Supplement 1 (see below).
In December 1999, the Medical Devices Agency (now the Medicines and Healthcare Products Regulatory Agency or MHRA) published Device Bulletin 9801 Supplement 1 entitled "Checks and tests for newly delivered medical devices". The document was a supplement to Device Bulletin 9801, "Medical device and equipment management for hospital and community based organisations", which was published by the Medical Devices Agency in January 1998. The supplement superseded HEI 95.
The document was intended to be applicable to all newly delivered medical devices, including non-electrical equipment, before being placed into service. Delivery checks detailed included paperwork checks, visual inspection procedures and functional checks. Electrical safety checks and tests as well as calibration checks were also recommended.
DB9801 Supplement 1 emphasised that new equipment under test should not be subjected to currents or voltages exceeding those experienced under normal operating conditions. Hence none of the recommended tests involved shorting applied parts together or applying high voltages to electrodes. It was also suggested that medical electrical equipment not having applied parts could be safety tested satisfactorily using non-specialist portable appliance testers.
Specimen forms for recording the results of checks and tests were given in the document. Rationales for the checks and tests prescribed were also given in the annexes of the document.
DB0801 and its supplements were replaced by DB2006(05) in November 2006 (see below).
In November 2006, the MHRA published (on their website only) Device Bulletin DB2006(05) - "Managing Medical Devices - Guidance for healthcare and social services organisations". The document updates and replaces guidance previously given in DB9801 ("Medical device and Equipment Management for hospital and community based organisations") and its supplements. Section 4 of the new guidance addresses "Delivery of a new piece of equipment" and hence replaces guidance previously given in DB9801 Supplement 1. Having said that, much of the basic philosophy behind, and recommendations from, the latter document have been retained.
The guidance stresses the importance of acceptance checks as a means of improving efficiency and reducing risk. It also emphasises the necessity of recording checks and test results in order to meet health and safety requirements, possible litigation demands and to enable safe and effective future device management.
Delivery checks relevant to medical electrical equipment on delivery are divided into administrative tasks ("paperwork/database") and visual inspection. Recommended administrative checks and tasks include:-
The guidance further recommends that functional checks, electrical safety tests and calibration checks (where appropriate) should be carried out prior to the equipment being placed into service.
No specific detail is given on safety tests, other than to emphasise that "pre-use tests should not exceed the bounds of normal use". In connection with this, it states that the tests described in IEC 60601-1 are "type tests" and are therefore not suitable for pre-use or maintenance tests (see paragraphs at 5.1 above).
The guidance does, however, point out the legal requirements for electrical safety testing under the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989. The guidance states that "Responsible organisations should ensure that they have implemented electrical safety testing procedures to comply with this legislation". The legal requirements are further discussed in these notes under paragraphs at 5.6 below.
The full text of DB2006(05) is available free of charge on the MHRA website at www.mhra.gov.uk
The International Electrotechnical Commission has been preparing IEC 62353 Edition 1: "Medical Electrical Equipment - Recurrent test and test after repair of medical equipment" for some years. Publication of this document is expected in the near future.
Also in preparation by the Institute of Physics and Engineering in Medicine (IPEM) is a publication called "Electrical Safety Testing: A Workbench Guide".
There are a number of items of legislation applicable in the UK that impact in a fairly direct way on maintenance procedures for medical electrical devices. These are discussed briefly below.
Since the Medical Devices Directive (Council Directive 93/42/EEC) became law in the UK in 1994, it has been mandatory that all medical devices put on to the market are appropriately CE marked to indicate compliance with the directive. An important component of the directive is a list of "essential requirements" to which all medical devices must comply. Compliance with these requirements can be interpreted essentially as meaning that the medical device is fit for purpose.
Depending on the risk class under which a particular medical device is classified, there are various means by which a manufacturer is able to demonstrate conformity with the directive. For devices in the lowest risk category (class I), self declaration is acceptable, whilst for medium and higher risk devices (classes IIa, IIb and III), the assessment route is more rigorous and may include auditing of the manufacturers' quality assurance system and independent type testing to a recognised standard (e.g. IEC 60601) of a representative production sample by a "notified body". Each notified body may be identified by a unique number that appears to the top right of the CE mark on medical devices.
In each member state a "Competent Authority" is authorised by that country's government to ensure that the requirements of the directive are carried out. In the UK, the competent authority is the Secretary of State for Health who has delegated day to day running of the competent authority to the Medicines and Healthcare Products Regulatory Agency (MHRA). The Medical Devices Directive is enshrined into UK law by the medical Devices Regulations 2002.
As far as the purchaser of equipment is concerned, all medical devices purchased within any EEC member state should be appropriately CE marked. Conformity to the directive should be confirmed by the equipment supplier by means of a "declaration of conformity" prior to purchase.
The Health and Safety at Work etc. Act 1974 (HASAWA) act may be regarded as the "catch all" act that covers all aspects of health and safety in the workplace. It places responsibility on employers and employees for the health, safety and welfare of all persons that may be affected by activities of an employer (including NHS Trusts). The overarching nature of the act is illustrated by part 1, section 3, paragraph 1 of the act that states:
"It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health and safety".
There are many sets of Regulations that are made under the act that spell out in detail what must be done to meet the requirements of the act. The Regulations are said to be "made under the Act", and non-conformity to any such regulations is therefore an offence under the HASAWA.
Particular requirements with regard to electrical equipment are imposed by the Electricity at Work Regulations 1989. Some significant extracts from the regulations are quoted below. It should be noted when reading them that the word "systems" refers to electrical installations and any equipment capable of being made live by them.
Regulation 4(1)"All systems shall at all times be of such construction as to prevent, so far as is reasonably practicable, danger".
Regulation 4(2)"As necessary to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger".
Regulation 4(3) "Every work activity, including operation, use and maintenance of a system and work near a system, shall be carried out in such a manner as not to give rise, so far as is reasonably practicable, to danger".
Regulation 16"No person shall be engaged in any work activity where knowledge or experience is necessary to prevent danger or, where appropriate, injury, unless he possesses such knowledge or experience, or is under such degree of supervision as may be appropriate having regard to the nature of the work."
Although the Electricity at Work Regulations clearly put requirements on employers and employees with regard to the necessity for maintaining electrical safety, the means by which this should be done are not spelt out in the Regulations.
The Management of Health and Safety at Work Regulations 1999 set out the need for organisations to develop formalised management systems for health and safety. These systems will form a part of the organisations health and safety policy.
The policy should detail arrangements for effective planning, organisation, control, monitoring and review of protective and preventative measures. Hence protocols for electrical safety inspection and testing of medical equipment should be a part of this policy.
A major plank of the regulations is prescription of the use of risk assessments as a tool in managing health and safety effectively. The prime obligation under health and safety legislation is to eliminate or minimise risks to health and safety of anyone who may be affected by work activities. Safe systems of work and effective preventative measures to achieve this can only be developed following effective risk assessments.