A Guide to Developing Usable Instructions For Use For Medical Devices
By Arathi Sethumadhavan, Naomi Cherne, and Adam Shames, Core Human Factors Inc
Medical devices can be complex and may require users to understand specific information about storage, use, disposal, or reprocessing. Although it is optimal to guide the use of devices via intuitive design to the greatest extent possible, manufacturers may have to rely on instructional materials to convey important information supporting safe and effective product use. Instructions for use (IFU) are therefore considered part of the product user interface.
Know Your Users And Their Use Environment
The design needs of instructional materials are, generally speaking, the same as the design needs for any product. Good design incorporates an understanding of a product’s real-life use: Who are the users of the product and what are their attributes? What are their goals, their strengths, their capabilities and limitations, and what are the characteristics of the use environment? Likewise, in order to effectively design instructional materials, you must learn about your users. You can do so through a combination of techniques, such as focus groups, interviews, field research, contextual inquiries, and literature reviews.
Instructional material design should take into account users’ needs as well as their perceptive, cognitive, and motor abilities. Instructional materials may rely on users’ perceptual abilities (such as visual acuity, color sensitivity), cognitive abilities (such as literacy, ability to focus, working memory, symbol comprehension), and motor abilities (such as grasping, unfolding). It also is important to consider what users already know — be it from similar, non-medical devices, or other products in the targeted therapy area — and how this would impact their use of the proposed product.
Instructional material design also should be mindful of the user’s environment. Will their environment be bright, dim, dry, damp, cold, hot, dusty, or drafty? Will the instructions be held close to the face, at arm’s length, on a nearby surface, or on a distant surface? Will the instructions be accessed in advance of use, or at the point of use?
Seemingly simple design choices can cause usability problems when they conflict with the intended users’ capabilities or use environments. Examples of these conflicts include choosing too small a font for a product intended for use by elderly patients in dimly-lit homes; using dense paragraphs of text to convey complex steps to busy clinicians, whose attention is diverted by other device displays and alerts; or providing instructions in booklet format for patients with rheumatoid arthritis, or for use in a cold environment, where users may be wearing gloves.
The more you know about your users and the environments where they will be using the IFU, the more capable you will be of designing effective instructional materials. Further, understanding the tasks a user must perform to use the product, errors that could occur during use, and the consequences of these errors helps focus design efforts on the information that will have the most impact on safety.
Design Usable Instructions
Designing usable IFUs involves selecting appropriate textual content, layout, organization, font, font size, contrast, and use of graphics. IFU usability becomes even more critical if your product requires complex actions of the user, has confusing steps, or the potential for harm. Below is a sample list of usability design heuristics for IFU development. The list is not exhaustive, and not all heuristics are relevant to all products; rather, these provide a starting point for considering the usability of your product given its unique risk profile, indication(s) for use, and specific user/use environment.
- Use short, action-based sentences.
- Present one action in each item of a list to avoid missing steps.
- Label all the key components in diagrams to minimize user confusion.
- State or depict the expected outcomes of actions so users can confirm they have performed the actions correctly.
- Avoid labeling that requires users to match text to symbols (e.g., relying on a key to interpret the meaning of symbols on a diagram, such as “K: power button”).
- Define any necessary technical words, and then introduce them in parenthesis. For example, “Before using the pen for the first time, you need to remove air bubbles from the cartridge (priming).”
- Include “negative” statements at the beginning of a sentence (e.g., “Do not press the button”).
- Identify consequences or potential risks of misuse to motivate compliance with instructions.
- Specify units to avoid misinterpretation of abbreviations (e.g., “5 seconds” versus “5s”)
- Redundantly present critical information in a “Frequently Asked Questions” (FAQ) section, within relevant steps, to minimize reliance on memory.
- Provide images that match the textual information in the instructions while accurately depicting proper use of the product; actions without illustrations may be overlooked, or interpreted as “optional.”
- Select a font size that is legible during use; ANSI/AAMI HE-75:2009 suggests 0.168 inches for the smallest lower-case letter and a reading distance of 24 inches with normal vision.
- Consistently associate information categories with visual cues to avoid critical information being overlooked or misinterpreted by users (e.g., if some actions are numbered steps, all actions are numbered steps).
- Present conditional determination as part of a step to prevent the step from being missed or inappropriately followed.
- Use symbols with ordinal meaning (e.g., “1, 2, 3”) for lists where order of action matters, and symbols without ordinal meaning (e.g., dots) when order of actions does not matter.
Test Your IFU
It is not possible to predict all use errors — incorrect or unintended use of a product, stemming from a user’s ability to access and interpret information in instructional materials — or to predict which instructional material designs will be most successful, without conducting usability testing. Usability testing helps reveal issues that users may encounter when using instructional materials, as well as identify what aspects of the IFU caused, contributed to, or failed to counteract the use errors. Therefore, it is necessary to test instructional materials before they reach real-world users, to evaluate their effectiveness and to confirm that they do not cause any errors or difficulties.
Various testing techniques can be employed to assess instructional materials:
- Participants can be asked to read sections of the instructional material and to restate, in their own words, what the sections convey, to determine if their comprehension of the text matches the original intent of the text. This technique assesses the text’s effectiveness in conveying critical information.
- Participants can be asked to perform tasks step-by-step, as they read the IFU, to discover whether it leads them to perform any task incorrectly, or to omit tasks. This technique assesses whether content and layout changes could make the instructional material more comprehensible for representative users.
- Participants can be asked to answer questions about the product’s use by referencing the instructional material. This methodology can reveal barriers to locating information, such as user expectations of where the information would be located (e.g., within a particular step, within a certain section), or the format in which users expect the information to be presented (e.g., picture, table, number, highlighted text).
Instructional material is part of the product’s user interface and is included during validation testing. However, validation testing involves simulated use of the product, meaning instructional materials are made available to participants, as they would be during actual use, but participants are not asked, and are under no obligation, to use the IFU.
Understand IFU Limitations
There is a great deal of variability in how users interact with instructional materials during simulated use studies. Users differ on which IFU sections they choose to reference; when, during use of a product, they engage with instructions (if at all); and the depth with which they read the IFU. Many individuals who appear to read the IFU later report that they were not fully engaging with the instructions, but instead “skimming” the material, only reading text that was bolded, or just looking at the images.
Many reasons could drive this variability. For example, readers may be familiar with similar products, and assume (accurately or not) that they already know the necessary information. They could assume that design affordances will be sufficient for guiding use, and that the instructions are redundant or secondary. Some users consider IFUs to be a troubleshooting resource, and would reference them only if they struggle to use the product. Users might avoid the IFU because of previous experience with worthless instructions, or because the instructions seem as if they will require too much effort to comprehend. Conversely, readers may be more drawn toward informing themselves about a product if they think the product is intimidating (i.e., due to its complex appearance or a scary use goal, such as injecting important medication).
Therefore, while instructional materials are a great informational resource for users, there is no guarantee that users will seek this information, or consume it in a stepwise manner.
Take-Home Messages:
- Avoid conflict between the design choices for instructional materials and the characteristics of intended users or their use environments.
- Focus design efforts on information that will have the most impact on safety by identifying tasks a user must perform to use the product, errors that might be expected to occur during use, and the consequences of those errors.
- IFU usability is more important if your product requires the user to take complex actions, has confusing steps, or the potential for harm.
- Perform IFU usability testing to reveal issues that users may encounter, as well as identify which aspects of the IFU caused, contributed to, or failed to counteract the use errors.
- IFUs are a great informational resource for users, but their proper use is not guaranteed.
Adam Shames is a well recognized human factors expert and the founder and CEO of Core Human Factors, Inc., a 20+ person consulting firm. He has an M.B.A. in international business from the Fox School of Business and Management at Temple University and a B.S. in human factors engineering and psychology (double major) from Tufts University, where he received the De-Florez Prize in Human Engineering. Adam also has a Certificate in Applied Ergonomics Training from the United States Army Center for Health Promotion and Preventive Medicine. Adam spent the better part of two decades conducting usability research, has been the Principal Investigator on hundreds of usability studies with tens of thousands of participants in cities around the world and has worked as a consultant for over 15 years. Adam is a long-time member of the AAMI Human Factors Committee, has been recently appointed by the American National Standards Institute (ANSI) as an Expert on the IEC Joint Working Group on Human Factors, and is a contributing author on all of the international human factors standards for medical devices.
Naomi Cherne is a Director at Core Human Factors, Inc. She received a Ph.D. from the Department of Psychology at the University of California Los Angeles, where she studied how people develop habits and how they overcome bad habits. She also spent many years conducting research on visual attention in healthy adults, memory in neurodegenerative patient populations, and used functional and structural neuroimaging to study the interactions of memory systems in the brain. Her interest in how people learn to do things and what can lead them to make mistakes was a natural transition to human factors and user research. Before joining Core, she spent four years performing forensic human factors analysis and safety-focused usability testing on products and environments ranging from roadways to factory equipment to children’s products.
Arathi Sethumadhavan is a Senior Director at Core Human Factors Inc, where she leads human factors activities across the product lifecycle for several medical device and combination products, including user needs identification, use-related risk analysis, and planning and executing formative and validation studies. Prior to joining Core, Arathi spent seven years providing human factors engineering leadership to multiple products in the Cardiac Rhythm and Heart Failure portfolio including the world’s smallest pacemaker. She has also spent many years examining human-automation interaction issues in air traffic control and in human-robotic teams and developed training programs for the Marine Corps and HAZMAT teams. Arathi is the Department Editor of Ergonomics in Design, published by the Human Factors and Ergonomics Society. She has delivered more than 40 talks and has published more than 30 articles. She has also won awards from the American Psychological Association, the American Psychological Foundation, and the Human Factors and Ergonomics Society. She has an M.A. and Ph.D. in Experimental Psychology with a specialization in Human Factors from Texas Tech University.