IEC 60601-1-3: Identify Essential Performance of a Medical Device
The difference between IEC 60601-1 edition 2 and edition 3 is that clause 4.3 of IEC 60601-1 requires the manufacturer to identify essential performance by applying risk management. Essential performance is defined as performance necessary to achieve freedom from unacceptable risk. Essential performance is most easily understood by considering whether its absence or degradation.
|Vimal K. Puthiyadath|
To determine which aspects of a device's performance are essential, the following steps may be followed:
- List all aspects of performance as potential sources of harm (i.e., hazards).
- For each function, determine whether operation in excess of or below the specified level of performance would result in harm.
- The levels of performance at which harm would occur establish the range of operation that constitutes essential performance. If variation in a given performance characteristic does not result in injury, then it is not essential performance.
- Once the essential performance is identified, all information, including test data, clinical research, and scientific literature, must be placed in the risk management file.
- The failure to provide essential performance by definition results in unacceptable risk. Since acceptable risk must be maintained under normal and single-fault conditions (according to 60601-1, clause 4.7), the manufacturer must maintain essential performance in both normal operation and during the failure of any one component of the device.
It is also important to note that ensuring essential performance is one of the most critical tasks associated with risk management as per ISO 14971. The alarm signal is intended to maintain risk at acceptable levels. Therefore, the design must ensure that the circuitry responsible for producing the alarm signals must be independent of the system components for realizing the functionality of the medical device. If the same components that cause a failure are also used to control the alarm, the mitigation is insufficient.
All risks associated with the interactions between the equipment (including labeling and the accompanying documents) and operators must be assessed through the application of usability engineering. This includes cases in which unintended actions by the operator (e.g., selecting an incorrect control or setting) could result in harm. It also includes cases in which information provided by the equipment (such as unclear or misleading information displayed by the equipment, or contained in labeling or the instructions for use) causes the operator to take inappropriate and hazardous actions.
For each hazard associated with the man-and-machine interface, the manufacturer must identify a design requirement to ensure that the associated risk is maintained at an acceptable level (according to the manufacturer's risk acceptability criteria). These usability design requirements must be identified in a document called the Usability Specification. As with any specification, implementation of the usability requirements must be verified before release of the design. In addition, usability specifications must be validated to demonstrate that they effectively reduce risks to acceptable levels.
In the end, all that is important is to do no harm. Do you think the inclusion of essential performance will drastically reduce the risk associated with medical devices?
Vimal K. Puthiyadath, Biomedical Electronics Engineer