By: Alpa Patel, B.S., RM (NRCM) and Alyessa D’Ewart, MPC
Consideration of human factors when designing a medical device should be a high priority. It is important that concerns regarding human factors are considered during the development phase of new medical devices. For many years, this phase of the process has been overlooked and ignored; however, great efforts have been made so that user errors are eliminated or reduced as much as possible. The FDA has released a human factors guidance document for medical device manufacturers. This document provides steps and guidance manufacturers should take to ensure new devices do not have potential for dangerous outcomes due to human error.
The risk management process for each medical device should include the elimination or reduction of hazards due to user error. User-related hazards generally occur when a user cannot interpret the correct use of the device or instruction for use (IFU) correctly. Human factors engineering and usability engineering should be incorporated into the risk management in the early development stages of the process to help manufacturers identify anticipated and unanticipated user-related hazards. Undertaking the human factor tasks during the early stages can help develop measures to reduce the possibility of user-related errors, and would demonstrate how the design supports safe and effective use.
When conducting the risk management analysis, it is important to consider not only the device users but also the user environment, and the user interface. Device users can range from professional caregivers, to installation and maintenance professionals, to patients and their family members. Regardless of the intended user, the device should be able to be used without potentially life-threatening errors. The characteristics of each intended user population is important to consider in the design of the device to accommodate the varying limitations of each intended user population. The user environment should also be analyzed as lighting, noise levels, equipment, and people in the room can distract users during performance.
The major factor to consider during a risk management analysis is the user interface of the device. This includes all points of interaction between the intended user and the device itself. Elements such as the size and shape, software systems, components or accessories, and how the intended user manipulates the device should be deliberately chosen to reduce the amount and severity of user-related errors. It is also important that the information and manipulation of the device is laid out in a logical sequence for the intended user. Users will expect medical devices to function similarly to other devices they have used, and disrupting this flow may cause user-related errors.
User tasks for each medical device should be identified and categorized based on the amount of potential harm that could result from user errors in each task. The tasks should be analyzed to determine the errors a user might make, the circumstances that may cause a user error, the potential harm from the error, and how the occurrence of the error might be reduced or eliminated. Critical tasks are those where serious harm could come from the task being done incorrectly or not at all. These tasks may change as the device design is modified, so it is important to continually reassess the critical tasks. It is also helpful to identify user-related issues in similar medical devices that are already on the market. This information should be used to reduce the potential user errors that can occur with the medical device being manufactured.
Other forms or methods of evaluation of the device can utilize expert reviews and heuristic analysis to identify weaknesses in the device design and establish modifications to reduce user errors.
Empirical approaches to identifying use-related errors may also be helpful by gathering data from representatives of the intended users. Observing the representatives interacting with the device and asking questions about why decisions are made can help the manufacturer when designing a medical device for specific tasks. Interviews can also provide valuable insight to known problems with a device and to possible solutions. These evaluations are beneficial during the design phases because it can allow the manufacturer to make modifications before the device goes to market.
Eliminate or Reduction of Use-Related Hazards
User-related hazards identified in the preliminary evaluations should be reduced or eliminated as much as possible during the final development stages of the device. This can be done by modifying the design of the device to remove the hazards, incorporating protective measures in the device to avoid the hazards, and by providing safety instructions and clear training for intended users. It is important to continue to reassess the device after each evaluation and modification to ensure that the user-related hazards were addressed correctly, and new hazards were not created.
Human factors validation testing should be performed to show the device can be used by intended users, for the intended purpose, and under the intended conditions, without user errors. This testing should be sensitive enough to capture user-related errors, even if the user is not aware they have made them. The user should be able to use the device as independently and naturally as possible, without any interference or guidance they would not normally have during actual use. The validation should also show that all user-related hazards have been reduced or removed during the development stages of the device. Information gathered during the preliminary analysis of the device is used to guide the validation testing.
The validation test participants should represent the variety of characteristics of each of the intended user populations. These characteristics should include considerations such as age, functional limitations, and previous experience. Similarly, the tasks performed during the validation should include the full range of critical tasks defined in the preliminary evaluations.
Generally, human factors validation testing should be done under simulated conditions, but on occasion, the validation can be performed during actual use or as part of a clinical study. This should only be done when simulated-use test methods are not able to allow adequate evaluation of the users and the device.
Incorporating human-use factors into the design of a device is a process that should be considered from the beginning of the manufacturing phase. Reducing and eliminating user-related hazards can greatly improve the safety and efficiency of the device. Best practices include performing a preliminary risk management evaluation, modifying the design of the device to eliminate as many hazards as possible, and conducting human factors validation testing.