Evolving Standards Reshape Medical Power Supplies

Apr 1, 2007 12:00 PM
By Peter Resca, Director of Engineering, and Dave Murray, Senior Product Engineer, Astrodyne, Mansfi

ISO 14971

ISO 14971:2000 “Medical Devices — Application of Risk Management to Medical Devices” was developed in a joint ISO/IEC committee along with the third edition 60601 standards. As such, they are tied closely together in defining the procedure and requirements for the certification of medical devices. Specifically, Clause 4.2 in the third edition standard states: “A risk-management process complying with ISO 14971 shall be performed.” The goal and major shift in this approach, summarized in Table 3, is to guide the development engineer through a process that ensures hazards are identified and mitigated. In this way, the standard can last over time and include current and future advancements in medical technology.

The process begins by analyzing potential hazards the medical device may cause in its application. It also considers possible misuse and fault conditions to account for all potential dangers. Once presumed risks are identified, an evaluation is made to determine the level of each risk. During the risk-control phase, the manufacturer must consider methods to mitigate or identify the potential hazards. This includes design considerations (design-in safety and/or protection and alarms), system considerations (design-in safety in application) and notification (markings, notes and instructions). Following the risk-control phase, the potential dangers are reevaluated with the identified measures taken. If the residual risk is deemed acceptable, the process continues to the report, which documents the steps taken and considerations made. The concluding step completes the loop by evaluating the medical device data in production.

The importance of ISO 14971 cannot be understated in the application of the third edition IEC 60601-1 standard. The role of risk management is mentioned more than 100 times in the standard. To support device compliance, the third edition describes a risk-management file, which is the supporting body of work that the risk-management process was applied to the device under evaluation. Documented evidence, including the analysis of hazards, steps taken to mitigate hazards and identification of unavoidable hazards, would be found in the file.

U.S. Adoption

For the United States, there is a more subtle change that would occur with the adoption of the new medical standard. The decision was made that the American Advancement for Medical Instrumentation (AAMI) would publish the standard as opposed to Underwriters Laboratory, who had published the previous editions based on the IEC 60601 medical standards. This is a minor shift, as the prior UL standards were based on the IEC standard and included input from the AAMI ES 1 standard and both AAMI and UL have long histories with the common goal of promoting the development of safe devices for the market.

However, the AAMI has attempted to publish a document more in line with the harmonized standard published by the IEC. The AAMI 60601 standard has reduced the U.S. country deviations to two pages. This is a significant change as the current UL 60601-1 has 32 pages of deviations for the United States. The deviations primarily include requirements outlined by the National Fire Protection Association (NFPA) and the National Electrical Code (NEC). Although it is likely the deviation list may grow slightly to resolve a few outstanding issues, it will maintain its goal of minimizing the differences for global compliance. The standard has been published as American National Standards Institute (ANSI)/AAMI ES 60601-1:2005 and is available through a variety of outlets including the AAMI website, www.aami.org.

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