KAN Report 31
|Ergonomics Guidelines for the Design of Medical Devices, 08/2005 (425 KB)|
Bookmarks in the pdf file link directly to the individual chapters.
The Commission for Occupational Health, Safety and Standardization (KAN) was founded in 1994 to assert German interests in OH&S matters, especially with regard to European standardization. KAN is composed of representatives of the social partners (employers, employees), the state (federal states and Laender), the Hauptverband der gewerblichen Berufsgenossenschaften (HVBG, Federation of institutions for statutory accident insurance and prevention) and the German Standards Institute (DIN). One of KAN's tasks is to pool the public interests in the field of occupational health and safety and to exert influence on current and future standardization projects by issuing coments on specific subjects.
KAN procures studies and expert opinions in order to analyze occupational health and safety aspects in standardization and to reveal deficiencies or erroneous developments in standardization work.
This study was based on the following task in hand:
A collateral standard (IEC 60601-1-6 "Medical electrical equipment – Part 1: General requirements for safety – 6. Collateral Standard: Usability: Analysis, test and validation of human factors compatibility") relating to the basic safety standard for medical electrical equipment (IEC 60601-1 "Medical electrical equipment – Part 1: General requirements for safety") is currently being drawn up. The collateral standard deals with fitness for purpose and thus with ergonomic aspects and user safety. The draft version of IEC 60601-1-6, dated 15 December 1999, makes the following statement concerning hazards for operators of medical electrical equipment:
"46.202.1. Safety Hazards for the Operator
To reduce Safety hazards for the operator of equipment ergonomic principles shall be taken into account.
To guide the application of human Factors engineering principles, potential safety hazards for the operator of equipment as mentioned in IEC/ISO/DIS 14971 /Annex D) have been supplied in the form of a checklist in Annex 2 of this collateral standard. Reference is made to essential requirements (in terms of achievable values or input in the design process) defined by ergonomic standards."
In the mirror committee (DKE/AK 811.0.4), KAN proposed that the approach taken in the ergonomics guidelines for machinery design (EN 13861 Safety of machinery - Guidance for the application of ergonomics standards in the design of machinery) be used for the design of medical electrical equipment too and put forward a suggestion for the checklist to be included in the annex (mentioned in the quote above) to draft standard IEC 60601-1-6. The German mirror committee concluded that there were two points requiring clarification in order for this to be done:
- the ergonomics guidelines for the machinery sector are based on the hazards specified in EN 1050. Other specific hazards might be relevant for the design of medical devices; and
- for the most part, the ergonomics guidelines for the machinery sector list European standards, draft standards and work items relating to ergonomic aspects. It is doubtful whether these can be referred to in an international IEC standard.
- These were the reasons which led KAN to commission a study with the objective described below.
Objective of the Study
The aim of the study was to prepare guidelines, based on a hazard analysis and risk estimation, on systematic consideration of the relevant ergonomic aspects when designing medical devices. To this end, the goal was to adapt the ergonomics guidelines developed for machinery design (EN 13861) to the special requirements of medical-device design.
The specific project tasks were:
preparation of guidelines on systematic consideration of the relevant ergonomic aspects when designing medical devices (unlike with the machinery sector, the standardization is carried out at the international level by IEC; according to EN 14971, medical devices are subject to special hazards). The following questions had to be answered in this context:
- Which of the hazards listed in the ergonomics guidelines for the machinery sector are also of relevance for users of medical devices?
- Are there – e.g. in ISO/DIS 14971 – other user hazards specific to medical devices which can be caused if ergonomic principles are not observed but which have so far not been documented?
- proposals for content for an annex to draft standard IEC 60601-1-6 which is being prepared by IEC TC/62A (WG 5); and
- developement of arguments to be presented by KAN in its comments concerning the potential hazard for users as a result of ergonomic principles not being observed.
On the European single market, directives 90/385/EEC (Active implantable medical devices), 93/42/EEC (Medical devices) and 98/79/EC (In-vitro diagnostic medical devices), which are based on Article 95 of the EC Treaty (previously Article 100a), specify the characteristics of medial devices. The essential requirements in these European product directives are intended to ensure "the health and necessary protection of patients, users [authors' italics] and third parties" (Section 1 of the German Medical Devices Act).
For the purposes of occupational health and safety, the user's health and safety are of primary concern in the design of medical devices. Users of medical devices include, for example, nursing staff and doctors but also service technicians. The patient can also be the user if he or she uses a medical device themselves. A key aspect for users' health and safety is ergonomic product design.
The legislation explicitly stipulates that medical devices to be placed on the market must comply with harmonized standards (Sections 8 (1) and 3 (18) of the Medical Devices Act). As well as safety requirements, standards can also include guidance on ergonomic design. Thus, standards should help designers of medical devices by showing them how they can prevent hazards to patients and users due to ergonomic principles not being observed.
Standardization in the Field of Medical-Device Design
The basic standards for medical devices are primarily drawn up at the international level. In this work, ISO/IEC follow a risk-management concept. This type of concept is defined as "systematic application of management policies, procedures and practices to the tasks of analyzing, evaluating and controlling risk" (DIN EN ISO 14971 "Medical devices – Application of risk management to medical devices").
The basic standard regarding safety of medical electrical equipment is IEC 60601-1 "Medical electrical equipment - Part 1: General requirements for safety". This standard does not explicitly deal with the ergonomics of medical devices or the hazard to the user due to ergonomic principles not being observed. There are no other basic standards specifically concerned with the ergonomics of medical devices.
Draft standard CD IEC 60601-1-6 "Medical electrical equipment - Part 1-6: General requirements for safety – Collateral standard: Usability" is the first to deal with medical devices' fitness for purpose.
The work already done in the area of machinery safety can serve as a basis for listing aspects which should be taken into account in ergonomic design of medical devices. The guidelines (EN 13861 Safety of machinery - Guidance for the application of ergonomics standards in the design of machinery) developed in this area are particularly intended as an aid to designers on how to give more consideration to ergonomic aspects when designing machinery. Taking these guidelines as the basis, a similar aid, tailored to medical electrical equipment, should be developed.
Deficits in the consideration awarded to ergonomic principles when designing medical electrical equipment devices often turn out to be deficits in fitness for purpose. The term "fitness for purpose" describes the extent to which a medical device is suited to the task, use, user's anatomy, expectations and abilities and his or her surroundings. In the US, fitness for purpose is already used as a criterion for approving new medical devices.
The risk-management concept presented in EN ISO 14971 covers the question of whether risks exist because of deficient fitness for purpose but does not provide for any specific risk-control measures. Consequently, is does not call for ergonomic principles to be taken into consideration when designing products either. It is not until the risk-assessment step that measures are taken to check whether a relevant hazard demands special (counter)measures on the part of the designer in order to eliminate or reduce the risk. If it does, the risk-assessment stage concludes by designating the hazard a "significant hazard".
The authors of these ergonomic guidelines for medical devices were asked to divide hazards resulting from ergonomic principles being neglected into relevant (theoretical) and significant (real) hazards. However, it proved difficult to compile a list of significant hazards. A field survey and the feedback from the parties involved in the KAN study illustrated that only very few injuries or near-misses involving medical devices were reported by the users concerned. In addition, incidents with ergonomic causes do not have to be reported and neglect of ergonomic principles is more likely to lead to harm of a long-term nature. Thus, the causal relationship between the incident and the harm is not obvious and the incident is not reported.
This report provides the following reference tools and aids for designers and developers of medical devices:
- a checklist, based on DIN EN ISO 14971, which helps the designer to identify occupational health and safety hazards and general safety-critical conditions of use;
- a table, based on EN 1050, with which to determine the hazards which are caused by ergonomic principles being neglected in product design. The comparisons with the contents of standards in the field of medical devices (EN IEC 60601-1 and EN ISO 14971) are intended to ensure that all hazards of relevance to the risk-management process are included;
- a list with brief details of the contents of selected ergonomics standards, intended to help designers, after they have analyzed the hazards, to design medical devices in an ergonomic manner.
A number of medical devices are produced by small and medium-sized companies which often do not have special departments responsible for managing quality and keeping abreast of new technical rules. These guidelines aim to help those target groups, in particular, so that they do not only take the common, obvious hazards related to medical devices (e.g. electrical hazards) into account, but also hazards due to ergonomic principles not being observed in the design.
Taking DIN EN ISO 14971 as their basis, these guidelines offer a clear introduction to the concepts and the system of risk analysis, evaluation and control for medical devices. During this study it became evident that there is presently not sufficient empirical data available on injuries or near-miss accidents from the user's point of view. It is therefore difficult, when conducting the risk-management process, to distinguish between significant and relevant hazards caused by ergonomic design principles not being taken into account.
The checklist, dealing with occupational health and safety aspects, is intended to draw attention to the fact that hazards to users of medical devices also have to be identified and considered. The guidelines also provide references to relevant standards for developers and designers, where they can discover what values, measuring methods and solutions can be of help for specific ergonomic issues.
Furthermore, the guidelines offer a sound foundation upon which to prepare practice-oriented instructions in the future.
Recommendations to KAN
The authors request that the KAN secretariat produce an abridged version of the guidelines itself or have it produced by another party; the abridged version should offer practice-oriented, clear instructions particularly for manufacturers (developers, designers).
The project team's report is to be published as a KAN report. When it is posted on the Internet, users should be able to choose between two versions (the abridged version for a compact overview and the long version for additional theoretical background information).
KAN should use the guidelines as the basis for its comments concerning ergonomic design of medical devices.
Recommendations to DIN/DKE
The authors request that the DIN/DKE standards bodies examine whether the guidelines can be used as an informative annex to standard IEC 60601-1-6 ("Medical electrical equipment – Part 1: General requirements for safety – 6. Collateral Standard: Usability") and whether the guidelines' contents can be incorporated into other standards .concerning medical devices.
Recommendations to the Federal Institute for Drugs and Medical Devices (BfArM) and the Federal Institute for Occupational Safety and Health (BAuA)
The data on injuries involving medical devices available to the study's authors is currently not sufficient to be able to distinguish between relevant and significant hazards. The authors therefore ask BfArM and BAuA to launch a study to record the necessary data. Research should be done in healthcare institutions to identify injuries/near-miss accidents and long-term phenomena which have led or can lead to hazards for employees due to medical devices not being fit for their purpose. The related ergonomic factors should be analyzed and a risk evaluation carried out. The addition of the findings of such a study to these guidelines would be desirable.
In this context, "currently" means 2000, the year in which the invitation to bid for the study was published.
 Medical devices are predominantly intended for medical purposes and achieve their principal effect in or on the human body and not – in contrast to drugs – by pharmacological means. The exact definition can be found in Section 3 of the Act on Medical Devices (which can be viewed in German at http://bundesrecht.juris.de/ bundesrecht/mpg)