Understanding Use Errors in Medical Devices

In healthcare settings, use errors with medical devices represent a critical issue that can threaten patient lives. Since April 1, 2024, medical device companies have been required to comply with JIS T 62366-1:2022 “Medical devices – Part 1: Application of usability engineering to medical devices.” This standard serves as a guideline for ensuring compliance with usability requirements stipulated in Articles 9 and 16 of the Essential Principles of Medical Device Safety and Performance, and it is a vital element supporting medical safety.

Definition of Use Error – From IEC 62366-1:2015

A use error is defined as “an act or omission of an act by a user, when using the medical device, that produces a result that is different from that intended by the manufacturer or expected by the user.”

Note 1: Use errors include situations where users are unable to complete tasks.

Note 2: Use errors can occur due to mismatches between characteristics of the user, user interface, task, or use environment.

Note 3: Users may or may not be aware of use errors.

Note 4: Unexpected physiological responses of patients do not constitute use errors.

Note 5: Malfunctions of medical devices are not included in use errors.

Essential Understanding of Use Errors

System design issues are deeply involved in the background of use errors. Non-intuitive interface design, inappropriate feedback, and complex operational procedures carry risks of causing serious accidents. Furthermore, in healthcare settings, factors such as time constraints during emergencies, fatigue from night shifts, and simultaneous management of multiple tasks act as triggers for use errors.

Annex A of IEC 62366-1 clearly explains that many use errors are not the result of user carelessness or negligence, but rather direct consequences of poor user interface design. This perspective is based on the “New View” advocated by Sidney Dekker, which emphasizes investigations aimed at understanding situations rather than blaming users.

Important Considerations Regarding Use Errors

Understanding the concept of “use error” correctly is extremely important when considering medical device safety. Particular attention should be paid to the following conceptual relationships.

Relationship Between Use Error and Misuse

Use error is part of reasonably foreseeable misuse. In the integrated framework of IEC 62366-1 and ISO 14971, “reasonably foreseeable use” includes both normal use and abnormal use. Furthermore, normal use is divided into correct use and use error.

ISO 14971 requires addressing all risks, including reasonably foreseeable misuse. On the other hand, IEC 62366-1 focuses on use errors that can be controlled through usability engineering, excluding abnormal use from its scope. This is because abnormal use consists of deliberate actions that cannot be controlled through user interface design.

For example, when healthcare professionals deliberately remove safety devices from medical equipment for use, this is abnormal use and outside the scope of IEC 62366-1, but it remains a consideration in ISO 14971 risk management. Conversely, mistakes arising from misunderstanding operational procedures are use errors and fall within the scope of IEC 62366-1.

Difference Between Use Error and Human Error

Use error and human error are not the same. While the term “human error” suggests user fault, use error does not necessarily imply user responsibility. Rather, many use errors result from system design problems or incompatibility with the use environment.

IEC 62366-1 considers the term “use error” more appropriate than “human error.” This is because not all errors associated with medical device use result from user oversight or carelessness. In fact, the majority of use errors are direct consequences of inappropriate user interface design.

For example, if an important button is difficult to locate during an emergency due to design issues, this should be regarded as a design problem rather than user fault. This perspective means that manufacturers bear the responsibility to identify and reduce use errors during the design phase through the usability engineering process.

Representative Examples of Use Errors and Abnormal Use

Examples of Use Errors (Within the Scope of IEC 62366-1)

Use errors in healthcare settings include the following examples. These are all unintentional mistakes that can be reduced through usability engineering.

• Pressing the wrong switch due to physical layout issues
• Inappropriate operations due to misinterpretation of panel icon meanings
• Misreading infusion settings due to panic during emergencies
• Device damage due to unclear instructions for use
• Impact on device performance due to insufficient consideration of the use environment
• Omission of steps due to use of inappropriate quick reference guides
• Mix-ups of pharmaceuticals or medical devices with similar appearances
• Setting errors due to misunderstanding screen displays

Examples of Abnormal Use (Outside the Scope of IEC 62366-1, but Considered in ISO 14971)

The following are examples of abnormal use, involving deliberate actions or deliberate omissions of actions. These cannot be addressed through usability engineering but should be considered in risk management.

• Using equipment without performing the pre-operation inspection items specified in the instruction manual (deliberate omission of procedures)
• Continuing operations despite alarm warnings, judging there to be no problem (deliberate disregard of safety information)
• Continuing to use equipment without performing periodic inspections (deliberate disregard of maintenance requirements)
• Having untrained personnel operate equipment due to emergency situations (deliberate disregard of training requirements)
• Using equipment without functional verification after dropping it (deliberate omission of necessary verification)
• Unauthorized modification of infusion pump settings by accompanying persons (deliberate operation outside authority)
• Using non-sterile scalpels due to shortage of sterile ones (deliberate disregard of contraindications)
• Using medical devices with protective covers removed (deliberate removal of safety devices)
• Using medical devices for purposes other than their intended use (e.g., exceptional violations such as using them as hammers)

These abnormal uses represent conscious and deliberate actions or deliberate omissions that violate or contravene normal use and are beyond any further reasonable means of user interface-related risk control by the manufacturer.

Human Cognitive Characteristics and Medical Device Design

Consideration of healthcare professionals’ cognitive limitations is essential. Memory limitations, attention allocation, and mismatches between expectations and actual operations can contribute to use errors. Therefore, incorporating mechanisms to prevent erroneous operations during the design phase, taking these characteristics into account, is required.

In IEC 62366-1, the relationship between user perception, recognition, and action is shown in Figure A.1, requiring design that enables users to perceive information, understand it, and act appropriately. Safety-related information in particular must be perceptible and understandable to users of the intended user profile in the intended use environment, and must support correct use of the medical device.

Practice of Usability Engineering

In medical device development, usability engineering must be implemented from the initial stages of design. This includes analysis of the use environment, understanding of user characteristics, risk analysis, and iterative evaluation. Evaluation assuming actual use conditions is particularly key.

JIS T 62366-1:2022 requires the following processes:

• Establishment of use specifications (intended medical indications, patient populations, user profiles, use environments, etc.)
• Identification of safety-related user interface characteristics and potential use errors
• Identification of known or foreseeable hazards and hazardous situations
• Identification and description of hazard-related use scenarios
• Selection of hazard-related use scenarios for summative evaluation
• Establishment of user interface specifications
• Establishment of user interface evaluation plans (formative and summative evaluations)

Notably, the 2020 revision (Amendment 1) introduced the concept of critical tasks (tasks where use errors could lead to serious harm) and strengthened requirements for summative evaluation.

Responsibilities of System Designers

Medical device designers bear the following responsibilities based on IEC 62366-1:

1. Inherently safe design and manufacturing: As the first priority, prevent use errors through design itself.
2. Protective measures in the medical device itself or manufacturing process: Implement design that prevents serious consequences even when errors occur.
3. Safety-related information, and user training where appropriate: Provide information that users can perceive, understand, and that supports correct use. The 2020 revision explicitly added user training as a risk control measure.

Consideration of healthcare professionals’ cognitive load is necessary in all of these. Additionally, manufacturers must appropriately document and maintain these efforts and their results in the usability engineering file.

Importance of Continuous Improvement

Knowledge gained from analysis of use errors should be utilized for system improvement. Feedback from use environments, findings from usability tests, and incident reports are valuable resources leading to the development of safer medical devices.

JIS T 62366-1:2022 requires review of post-production information, mandating review of available post-production information including field reports on complaints and accidents or near incidents. Instances of use errors that could cause hazardous situations, or instances where field information suggests hazards or hazardous situations attributable to insufficient usability nearly occurred, must be maintained in the usability engineering file and utilized for continuous improvement.

Regulatory Requirements and Transition Periods

According to a notification from the Ministry of Health, Labour and Welfare (Notification No. 0930-1 of the Pharmaceutical and Medical Devices Agency dated September 30, 2022), compliance with JIS T 62366-1:2022 became required. This notification took effect on October 1, 2022, and the transition period ended on March 31, 2024.

For medical devices manufactured and marketed after April 1, 2024, marketing authorization holders, foreign special approval holders for manufactured medical devices, and foreign designated high-risk medical device manufacturing businesses must have systems in place to confirm compliance with JIS T 62366-1:2022.

It should be noted that in addition to JIS T 62366-1, internationally recognized standards or Japanese Industrial Standards such as IEC 62366-1:2015+Amendment 1:2020 and JIS T 60601-1-6:2023 may also be used to satisfy the requirements of the Essential Principles regarding usability.

Summary

Use errors are not mere operational mistakes, but complex issues with design and use environment problems in the background. Compliance with JIS T 62366-1:2022 is the first step toward addressing this. Future medical device development requires incorporating human-centered design philosophy and making efforts to minimize use error risks.

What is important is not to regard use errors as user responsibility, but to recognize them as system design issues and address them systematically through the usability engineering process. Additionally, understanding the difference between use errors and abnormal use and adopting a risk management approach that appropriately integrates IEC 62366-1 and ISO 14971 is the best path to improving medical safety.

Manufacturers are encouraged to implement comprehensive usability engineering not only to ensure medical devices can be used safely, but also to realize commercial advantages by providing excellent usability. This can reduce the risk of medical accidents due to use errors and ensure the safety of healthcare professionals and patients.