In a previous blog, I covered the importance of identifying all your medical device users and provided examples of some of those users. Once the users are identified, you need to determine how they will use the product and their needs. There are multiple ways to identify the users and their needs. I prefer the following process.
- “Follow” the device from its initial delivery to first use, then to its next use. In a home use setting this may be very limited. However, in a hospital setting, the device may move through many departments from inventory management to clinician use to decontamination back to inventory management. This process of “following the device” enables you to identify all the users.
- Once the users are identified, determine how each one interacts with the device. Use cases and use case diagrams are excellent tools to help you understand how the user interacts with the device. Where possible, confirm these interactions by direct observation. Including someone trained in human factors is helpful. Observation can be done on a similar product and throughout development as part of confirming usability, which is described in the FDA guidance document Applying Human Factors and Usability Engineering to Medical Devices.
- Identify additional use environments and repeat step 2 above.
Below are two examples that illustrate how the user and their needs may change based on the device use.
Example 1: Blood glucose meter, pocket size
This common medical device is used by many different types of users. The meter and strips are typically supplied to the user in a box from a pharmacy or diabetic supply company. Once delivered to the user, there is no additional movement of the device to other users or types of users. In this scenario, focus on the users, their required performance for the intended use, and all the different environments.
Home users of a glucose meter may include a parent testing a pediatric patient, an active or young adult, and a user with limited mobility. Any of these users may also have limited dexterity and/or eyesight. Another primary user is a clinician who provides point of care services. These services may be through home cares services or in a clinical setting, such as a nursing home.
Starting with the active or young adult, determine how and where they will use the device. They may use it in multiple locations: home, school, or job. The device must be portable to go many places. It may sit in a car when not being used, so the meter and the strips may be exposed to wide temperature and humidity variations.
A user with limited mobility may be elderly and use the device only in the home. Issues with neuropathy, manual dexterity, and the ability to read information on the display can affect their correct use of the device. Portability is not a significant concern.
A meter being used by a clinician may have a more controlled physical environment, but needs to prevent contamination between patients, usually through a decontamination process. You may need to work with a clinician to determine the best way to decontaminate the device without damaging the meter.
In October 2016, the FDA released two guidance documents related to portable blood glucose meters. The first guidance document is Self-Monitoring Blood Glucose Test Systems for Over-the-Counter Use. This guidance document describes lay users and in-home use. The second guidance document is Blood Glucose Monitoring Test Systems for Prescription Point-of-Care Use. This guidance document discusses glucose meters used in professional healthcare settings, such as nursing homes. The FDA points out that the use settings and use populations differ significantly, which manufacturers should consider when designing their devices.
Example 2: Surgical, powered hand tool
Surgical powered hand tools have been used for years. However, the number of female surgeons has been growing and they have consistently identified a need for tools that are smaller and lighter. The existing tools are too heavy causing fatigue and frequently require both hands to operate affecting fine adjustments.
Many different users handle powered surgical tools. By following the device from delivery through its ‘movement’ in the organization, you can determine all the users and their requirements. When a new surgical tool arrives, it is entered into a tracking system. It may need to be cleaned and sterilized before the first use. This may be an internal service or sent to an external service. Then tools are setup prior to surgery by a surgical nurse. The surgeon uses the tool. Following surgery, the device needs to be decontaminated and sterilized again prior to use with another patient. The facility may also track the tools by surgery, so additional handling may be required for inventory purposes. This path is consistent with a hospital. However, the device may be used in stand-alone surgical centers or in a physician’s office. You will need to follow the device’s path in each setting.
When receiving a new hand tool, the existing serial number should be easily found and the institutions tracking information should be easily added. Next, the device goes to cleaning and sterilization. In this environment, the user is looking for a process similar to other products. Where special cleaning procedures are needed, the user needs an easy method to find that procedure. For sterilization, the device needs to be stable to the method used, often autoclave with steam sterilization. Next, the setup for the surgical nurse should be simple and intuitive. The device should fit a setup tray and be easy to give to the surgeon. The surgeon is looking for a hand tool that is light and can be used with one hand. Any post-surgical preliminary cleaning or soaking procedures need to be clear to the operating staff.
In this example, the hand tool goes to many different users. However, each user handles the device in a specific, controlled way.
You may find conflicting user requirements based on your analysis. These should be resolved based on the intended use and target markets. Once the use has been explored and the user needs identified, a spreadsheet is a common method to capture the actual requirements and build traceability between the user needs and the design inputs (or product requirements.)