AAMI Update: Human Factors Engineering: Essential Elements in the Product Development Process

By Tressa Daniels

Human factors engineering (HFE), while certainly not new, is having a moment. This article explores the critical importance and methodologies of HFE, highlighting its pivotal role in enhancing safety, efficiency, and user satisfaction in the development of medical devices.

How does HFE accomplish these important goals? Simply put, by designing products that align with human capabilities, expectations, and limitations. HFE is particularly valuable in fields such as healthcare, aviation, and consumer electronics, where it can lead to significant improvements in usability, reduce the risk of use errors, and tailor devices to diverse user needs.

Before conducting usability testing in the design and development phase, several steps are necessary to optimize HFE. Initial research and observation are invaluable to understanding points of user confusion, workflows, workarounds, and environmental considerations involved with predicate or competitor products. This research can assist in identifying user needs as well as understanding user profiles and potential use errors.

Key activities in this phase include:
1. User Research: Understanding user problems and needs through interviews, surveys, and other research methods.
2. Workflow Analysis: Studying how users interact with existing systems and tools to identify pain points and opportunities.
3. Contextual Inquiry: Observing users in their real-world environments to gain insights into their natural behaviors and needs.

TASK ANALYSIS
In addition to research and observation, a task analysis is an important method used to break down the steps required to complete a task and analyze each step for possible areas of design deficiency. A task analysis can start before a prototype exists by using a similar in-market product or the defined product purpose developed during concept and feasibility.

PERCEPTION, COGNITION & ACTION
The Perception, Cognition, and Action (PCA) model is a key part of the task analysis, used to better understand and analyze human interactions with systems, particularly in identifying the root cause of use errors later in design and development formative testing. It involves perceiving relevant stimuli, processing the information to make decisions, and taking actions based on cognitive processing. Here’s a breakdown of PCA:

1. Perception

• Stimuli: Users must perceive (see, hear, touch) relevant stimuli from the environment or device interface.
• Challenges: Issues can arise if stimuli are not noticeable or are misinterpreted.

2. Cognition

• Processing: Users process (understand, comprehend) the perceived information to make decisions.
• Challenges: Cognitive overload, misunderstandings, or incorrect assumptions can lead to errors.

3. Action

• Execution: Users take actions (push, pull, press, twist, etc.) based on their cognitive processing.
• Challenges: Physical limitations, incorrect actions, or delays can cause errors.

By applying the PCA model, potential use errors can be systematically identified and addressed during the design and testing phases, thereby reducing post-market problems.

During design and development, the project team will plan a minimum of two to three formative usability tests. In addition, there are other methods of formative evaluations that can also be conducted. Formative Evaluation Methods involve both analytical and empirical techniques to assess and improve the user interface (user interfaces include software, hardware, IFUs, training material, accessories, and packaging). Analytical methods include task analysis, heuristic evaluations, and expert reviews and do not include feedback from intended users. Empirical methods involve gathering direct user feedback through in-depth interviews, contextual inquiry, cognitive walkthroughs (note: these can be done with or without users), and usability testing.

FORMATIVE TESTING

Formative Testing is an iterative design process to identify and fix user interface problems early. It involves three key steps:

1. First, identifying issues by revealing 90% of design flaws with 8-10 intended users (not employees).
2. Next, modifying the design to eliminate errors and use problems.
3. Finally, confirming effectiveness of the changes by conducting human factors validation testing.

HUMAN FACTORS VALIDATION
HFE is not complete without Human Factors Validation. Human Factors Validation testing is used to prove that the final design is safe and effective for use. This includes identifying and mitigating potential hazards through risk analysis, iterating on the design to fix issues through formative testing, and proving the design is safe and effective through HF validation testing.

Human Factors Validation Testing requirements include:

• 15 users per intended user group
• All critical tasks be performed
• Final production equivalent product
• Simulated environment of use
• Realistic training scenarios
• Uninterrupted use conditions

Human Factors Validation Testing is essential to demonstrate that the final design is safe and effective for use.

HFE is a specialized skill set that considers all aspects of medical device design holistically. It strikes a balance between safety and usability, focuses on risk reduction, and ensures compliance with global regulations.

And what’s the bottom line on HFE? The return on investment (ROI) for incorporating human factors can be observed in several areas:

1. Preventing costly recalls: Early identification and mitigation of usability issues can prevent expensive recalls.
2. Higher user satisfaction and loyalty: Improved user satisfaction can lead to increased market share.
3. Decreased Costs: Addressing usability issues early in the design process can save significant costs associated with redesigns and post-market fixes.

In summary, investing in human factors engineering is not just about meeting regulatory requirements; it’s about creating products that truly meet the needs of your users, customers, and patients.