|
  FULL ARTICLE of 2011winter_news
 Medical Risk-Based Testing with the IEC60601-1 3rd Edition
We have been advising clients to use risk-based testing methods since the inception of our company 10 years ago. However, only recently have the standards started catching up. One example of this is with medical standard IEC/EN 60601-1 3rd Edition. This marks the first time a medical standard requires users to base their testing approach on the risks they uncover during the risk analysis. We are hopeful that other industries are soon to follow.
In this article, the discussion will center on the International Standard for medical devices, the third edition of the IEC / EN 60601-1: Medical Electrical Equipment, Part 1: General Requirements for Basic Safety and Essential Performance (the General Standard). The newsletter will also discuss the changes from the 2nd Edition to the 3rd Edition of the General Standard. This newsletter will only look at the Standard at a very high level due to the recognition that there are a bewildering variety of medical devices on the market such that a detailed treatment of the standard is beyond the scope of this newsletter.
The 3rd Edition of the General Standard (IEC) was published in 2005 with the harmonized version of that Standard (EN) published the following year. It supplanted the 2nd Edition that was first published in 1988 with a number of amendments over the subsequent years leading up to the 3rd Edition. It was recognized that Basic Safety is not enough for Responsible Organizations that have to depend on other performance specifications regulated by market pressures such as Essential Performance (EP) functions or features.
The 3rd Edition of the General Standard covers four general safety levels:
The anticipated 2nd Edition “withdrawn” dates are shown below:
Europe / most of world: June 1, 2012
US: June 30, 2013
Canada: June 2012 for new products
Europe date is firm
US date not yet set in concrete
After these dates, the Medical Electrical Products must be compliant to the 3rd Edition of the General Standard. Exceptions can be made however by working with your 3rd Party Notifying Body (i.e.: TUV, UL, CSA, NSAI, BSI, etc.) by providing objective evidence of striving for compliance and a timeline for meeting the requirement objectives.
When the product is to be marketed, or ready to be marketed, as a medical electrical equipment (MEE) and /or system (MES), the applicable International Standard is the 3rd Edition of the General Standard. Unlike the 2nd Edition of the General Standard, in the 3rd Edition it always starts with Risk Management. The Risk Management File (RMF) is a set of records and other documents that are produced by the Risk Management Process as defined in the Standard ISO 14971:2009. Typical RMF documents can be FMECAs (Use, Design, Process, and Software FMECAs as well as System Hazard Analysis (HA) are use widely), Fault Tree Analysis (FTA), Fishbone analysis, etc. The RMF Report summarizes the highest risks determined from the analysis. It is these documents that the test house will review first to determine any single fault conditions or risk mitigations that need to be tested in addition to the Basic Safety tests that the General Standard requires. In essence, the 3rd Edition now becomes more of a Risk-Based standard as opposed to the 2nd Edition which was more of a Test-Based standard.
Another new requirement is the Usability Engineering File (UEF) which can take elements of the RMF as inputs. UEF is the application of knowledge about human behavior, abilities, limitations, and other characteristics to the design of TOOLS, machines, equipment, devices, systems, tasks, jobs, and environments to achieve adequate USABILITY (Characteristic that establishes effectiveness, efficiency, and OPERATOR learn-ability and satisfaction). The Collateral Standard for Usability, IEC 60601-1-6, will soon be replaced by the IEC 62366 Standard; Application of Usability Engineering to medical devices. The inputs to 62366 Standard takes many of same elements of the RMF Report outputs as well as the Accompanying Documents (i.e.: Instructions for Use (IFU), Operating Manuals, Patient Handbooks, etc.).
When preparing the RMF, one will need to clearly define the Medical Electrical Equipment (MEE) or Medical Electrical System (MES) products Basic Safety and Essential Performance function or features as well as the products Applied Parts and those components that have High-Integrity Characteristics. The definitions of these are from the Standard:
There are 17 Clauses in the 3rd Edition of the General Standard (consolidated from the 59 Clauses of the 2nd Edition). The first three clauses, Clauses 1, 2, and 3, pertain to the Scope and the Objective of the Standard as well as the related standards (the Collateral and Particular Standards), the Normative References, and the definitions of the terms used in the General Standard.
The General Standard requirements begin with Clause 4 which defines the General Requirements of the Standard. The key requirements in this clause are as listed below:
RMF (Identifying not just the Hazards as defined in ISO 14971, but also the Risks and Hazards identified in the other Clauses of the General Standard)
Defines: BS, EP, Expected Service Life, AP, Components of MEE (Fig. 5 in the General Standard), Hi-Reliability Components (components of high integrity)
Equipment to remain Single Fault Safe or the risk remains acceptable through the application of the Risk Management Process.
Equivalent Safety (4.5) - Where this standard specifies requirements addressing particular RISKS, alternative means of addressing these RISKS are acceptable provided that the MANUFACTURER can justify that the RESIDUAL RISKS that result from applying the alternative means are equal to or less than the RESIDUAL RISKS that result from applying the requirements of this standard.
Figure A.5 in Annex ‘A’ of the General Standard illustrates by way of example what constitutes an Applied Part (the Wall Stand and the Patient Support), a non-Applied Part (X-ray source), and which non-Applied Parts that could be touched by the Operator and / or Patient and thus needs to be tested as a though it is an Applied Part (X-ray source can be adjusted by the Operator who could conceivably simultaneously touch the Patient).
Figure 5 in Clause 4 of the Standard illustrates the flowchart used in determining the components qualifications:
Clause 5 defines the General Requirements for Testing MEE that is used in the General Standard. Some of the Clause’s highlights are listed below:
Type Tests (one representative production sample), No. of Samples (if necessary and could reduce your overall test time / schedule)
Ambient Conditions as defined in IFU
Define least favorable operating conditions (voltage, temp., humidity from IFU or RMF)
Applied and Accessible Parts (tests using the Standard Finger and Hook)
Repairs and Modifications
Test sequence per Annex B
Clause 6 defines the general Classifications ME Equipment and ME Systems
Class I or II (electrical class depending upon the type and levels of insulation used)
Type B, BF, or CF (B-Body, BF- Body Floating, and CF- Cardiac Floating each in order of increasing degrees of protection from electrical shock)
IPXX (ingress protection per IEC 60529, the 1st X number is for protection from solid ingress and the 2nd X number is for protection from liquid ingress)
Method of Sterilization (to be indicated in the IFU if applicable)
Use in an Oxygen-Rich Environment
Mode of Operation (continuous or non-continuous)
Clause 7 details requirements for the products Accompanying Documents such as the Instructions for Use (IFU) or the Directions for Use (DFU), product labeling including durability tests, etc. There are new Safety Signs and Symbols in the 3rd Edition of the General Standard that were not in the 2nd Edition.
Protection requirements against Electrical Hazards are defined in Clause 8. The requirements for Leakage Current & Dielectric Strength and Creepage Distances & Air Clearances in the 3rd Edition have changed very little from the 2nd Edition. One of the biggest changes between the 2nd Edition and the 3rd Edition is in the definition of the Means of Protection (MOP) (sub-clause 8.5.1) and the figure below illustrates how it may be possible to use lower cost electrical components. If the component part is Applied Part that comes into contact with the Patient, then requirements for the Means of Patient Protection (MOPP) is the same as it was in the 2nd Edition of the General Standard. However, if the component part is only in contact by the Operator (MOOP, Means of Operator Protection), the Manufacturer has the choice of selecting a part that complies with the IEC 60950-1 (the International Standard for Information Technology products) or a part that complies with the MOPP requirements of the General Standard.
For Protection against Mechanical Hazards, Clause 9 details the requirements of the following:
Accessible moving parts (crush hazards), edges/corners
Instability & Expelled Parts
Acoustic / Vibration
Pressure Vessels & Support Systems
Clause 10 details the requirements for Protection against Excessive Radiation. This includes X-Rays, Particle, µ-wave, Laser, Infra-Red (IR), and Ultraviolet (UV) radiation.
For Protection against Excessive Temperatures, Clause 11 details the requirements for following items:
Internal MEE temperatures and Touch Temperatures,
Fire prevention & fire enclosure,
Flammable agents / gases,
Ingress protection / classification,
Material Biocompatibility / Sterilization
For the requirements for Instruments and Controls Accuracy, Clause 12 details the accuracy of the output limits as well as the hazards associated with exceeding the safety limits. The Usability of the Controls and Alarms are addressed in this clause by following the Collateral Standards 60601-1-6 and 60601-1-8 respectively.
Clause 13 regarding Hazardous Situations defines and details specific hazards and Single Fault Conditions (SFC) such as battery leakage, overheating of transformers, failure of over-temperature devices, mechanical hazards, motor overload conditions, etc.
The requirements for Programmable Electrical Medical Systems (PEMS) are defined in Clause 14. This clause was originally a stand-alone Standard, IEC 60601-1-4, which was incorporated into the 3rd Edition of the General Standard. In general, it details the requirements for the PEMS:
Risk Management Plan (tied closely with RMF),
Software / Firmware used in the Medical Device,
S/W Development Life Cycle, Architecture, V&V, Network / Data Coupling (IEC 60304), and
Modifications to the Software.
General MEE Construction requirements are defined in Clause 15. The Clause details the Mechanical Strength requirements such as push, impact, drop, rough handling, moulding stress relief, etc. as well as the general assembly of components including the use of batteries. Table 28 in sub-clause 15.3.1 illustrates the types of tests required per type ME Equipment in your product.
The general requirements for Medical Electrical Systems (MES) are defined in Clause 16. This clause was originally a stand-alone Standard, IEC 60601-1-1, which was incorporated into the 3rd Edition of the General Standard. In general, it details the requirements for the MES:
System - Connection of the Equipment(s) (to be described in the Accompanying Documents),
Power supply(ies), Enclosure, Separation of Devices (leakage currents), and
Connections / Wiring.
Clause 17 describes the requirements for Electro-Magnetic Compatibility (EMC). The radiated and conducted immunity sub-tests are detailed in IEC/EN 60601-1-2:2007.
The annexes in the last section in the Standard provide useful information on following the clauses and sub-clauses. Two in particular; Annex A: Guidance & Rationale and Annex B: Recommended Test Sequence gives the . Working with your 3rd Party Testing House & Notifying Body and your RA/QA Departments early in the your project can save considerable time and expense.
The relationship between the General Standard to the Collateral and Particular Standards are illustrated in the figure below (source: Intertek, Changes from IEC 60601-1 2nd to 3rd Edition, Sept. ‘08)
A few of the Collateral Standards were discussed earlier. These standards provided additional requirements to the General Standard depending on your products applicability. For example, if your product is an X-Ray device, then IEC 60601-1-3 applies. Among the newest Collateral Standards are IEC 60601-1-9 for Environmental requirements and IEC 60601-1-11 for Household use ME products.
The Particular Standards provide requirements that supersede the requirements in the General Standard. For example, IEC 60601-2-2 provide leakage current and safety requirements for high frequency surgical products over and above the requirements stated in the General Standard with specific test set-ups and measurements.
If your medical device product is currently on the market and your firm wishes to continue marketing the product, Ops A La Carte can provide Gap Analysis guidance services as well as test recommendations to help get your 2nd Edition device to be compliant with the 3rd Edition of the General Standard, IEC / EN 60601-1: 2006.
top of page
| | |
