Medical products are being challenged to meet rising demand for in-home treatment options, but the home is a unique space and requires careful planning. Home healthcare device design presents challenges relative to its in-clinic counterpart. The home introduces an uncontrolled environment with more variables and an unknown user. Further, designing to the 60601-1-11 Home Healthcare standard takes careful attention. This article highlights the steps we took to develop a body-worn therapeutic and accompanying console for home use.

In-home design forces product designers to consider the extremes of the environment, the user, safety, and connectivity, which, for this project, called for different design requirements for the wearable and console. For this wearable device, we designed features that ensured position repeatability, user feedback, and robustness, while the console’s design reflected hardware and software features for preventing misuse and supporting cybersecurity, portability, and power. These design decisions stem from questions relative to in-home use and 60601-1-11 compliance.

1. How big can the tethered console be for adequate home use?
Considerations: Where/when does it need to be used? How often? Does a person need to carry it upstairs? Is it heavy enough to require a cart? How long will the cords be?

For our product application, the user needed to be lying down during use of the system, which made a bedside or coffee table a viable platform for the console. This determination alone starts to constrict the device size and weight. Homes, unlike clinics, are not guaranteed to have elevators, laminate floors, or standardized surfaces, which required us to consider these unknowns carefully when weighing the device features with use cases.

In terms of device size, smaller is not always better, but bigger certainly brings placement and transport challenges. For example, if we designed a small device, but the user had to put it on the floor, the device’s user interface (UI) might not be visible from the bed position. On the other end of the spectrum, if it was massive and hard to locate near the bed, it would be difficult to interact with during set-up. In the end, size reduction options were limited by internal hardware space claims, so we moved forward with a requirement that a table or surface must be available to place the console. We also pursued a design that included handles and weight maximums that ensured it could be carried by a single person.

In 60601-1-11 terms, these considerations led to our definition of the console as “non-transit operable and portable” and the wearable as “non-transit operable and body-worn.” Of the classifications in 60601-1-11, our console and wearable were subjected to different mechanical stress tests based on the different intended uses. Lightweight body devices might see more human interaction, and thus are more likely to be dropped from six feet, whereas a console may be less likely to drop, but more damage could incur.

2. Where is the nearest power outlet? What happens if power fails?
Considerations: Does it require wall power? How far is the nearest outlet from the use location? What happens if the house loses power?

The location of the console defined other power and portability constraints. The 60601-1-11 standard required us to evaluate the risk of power reliability and availability at the onset of electronics design. In balancing the device and usability needs, we determined a wall-powered console was appropriate. Unlike hospitals, homes are not necessarily protected by isolated power systems and are categorized as part of a public mains network. The 60601-1-11 standard requires all portable devices for home healthcare to be Class II internally powered. This can have profound implications on electrical safety architectures because it implies protective earth cannot be used as a method of protection. Power-quality concerns also affected the console design process in several ways, including additional risk analysis on patient safety due to loss of power, extra consideration of auditory alarms in addition to visual, and supplemental electromagnetic compatibility conducted immunity tests.

3. Where will the device be stored and used?
Considerations: Does the device need to work in the dead of winter in mountainous Colorado or in the raging summer in Arizona? What if the device is stored in the attic?

It can be easy to lose appreciation of the consistent environment in clinic as designing a home device provides a new set of challenges. The 60601-1-11 standard expands the general standard environmental conditions to 5°C to 40°C, and 15 percent to 93 percent RH (relative humidity) versus 10°C to 40°C and 30 percent to 75 percent RH, respectively, for a hospital device. Both standards allow manufacturers to define smaller operating regions, but the product value will be affected if, for example, all of Southern California cannot use the device in the summer. To ensure safety at the temperature extremes, the console and wearable include redundant temperature monitoring circuitry and diagnostics to prevent use over a specific ambient or operating temperature.

4. How could misuse result in harm to the patient?
Considerations: What happens if the wrong person puts on the device? What if a person puts a wearable designed for the abdomen on their leg?

The paradigm shift from a trained clinician to an average person is a significant consideration in designing in-home devices and a focus of the 60601-1-11 in-home healthcare collateral standard. Early usability analysis was crucial input for our in-home wearable in order to shape the physical form and system-user feedback. We considered wearable features that made it difficult to place in the incorrect location and complex feedback systems to verify and even adjust placement if necessary. Additionally, following 60601-1-11 guidance, we designed additional ingress protection on both the wearable and console to compensate for the increased risk of exposure to fluids. We also considered software controls that severely limited unwarranted access to the device, including complex cybersecurity techniques that included password-protected user interfaces. The feedback loop and device control are critically important for both patient safety and compliance for a therapeutic administered without oversight.

5. How do you design a complex medical device for a non-medical professional?
Considerations: How does the system show complex analyses in a simple form? What do you show the user, and how do you show it?

Without a trained clinician to operate the system, the device must automate checks that would otherwise have been done manually. Specifically, the wearable must eliminate use errors wherever possible by design, and the console must detect and effectively communicate sometimes complex errors and instructions to the user. To ensure all errors that could cause unintended risk are detectable or preventable, significant work was required to assess usability of the device and necessary redundancy of software and hardware controls. The 60601-1-11 standard considers this unique requirement for an in-home device, and, for example, requires auditory alarms for all medium- and high-priority errors or issues.

Home devices are expanding into a realm of complex therapeutics and diagnostics, opening questions about how to have a patient interpret device results. This adds a whole new dynamic to reducing complexity for user simplicity. Both the console and the wearable required complex algorithms and processing, distilled into simple feedback to the user. In our device, we found simple light and vibration were familiar during placement of the device, and additional device setup was best shown through a user touchscreen interface.

6. How can the device design encourage or ensure patient compliance, and how are product successes and issues tracked?
Considerations: How can the design promote compliance? How can troubleshooting be done with minimal inconvenience to the user? How can important use data be collected reliably and safely to understand product issues and identify potential areas of improvement?

Another in-home development consideration involves designing the device to encourage correct usage and to simultaneously indicate when it is not being used properly. Without a clinician present during normal use, these burdens fall on the product, affecting everything from long-life component selection to the addition of secondary software modules, and to database and device connectivity features. The 60601-1-11 standard considers the need for in-home technical support and has requirements outside design specifics to ensure documentation, labels, and instructions adequately provide sufficient information for users.

For our design, we considered the need to collect clinical data for initial device performance assessments. This exposed the possible need for a cloud database and significant cybersecurity design because it was not reasonable to assume regular access to local storage in devices across patients’ homes. In turn, this not only made us think about how the device logged data (i.e., WIFI interface) but what was logged (e.g., device actions, user actions, results, etc.). The goal is always to balance data storage and transmission requirements with the desire to be able to paint a picture of each use and understand how users can be inadvertently affecting the success of the device. It is critical for a device to consider these secondary users and what they need to access in order to ensure the safety and success of the product in the home marketplace.

Conclusion
The expansion of medical devices into the home offers huge opportunities for medical advancement. The implications of the added unknown user and uncontrolled environment require early risk and usability assessments to ensure the product is not only safe, but functional in the hands of an untrained user. Although the 60601-1-11 Home Healthcare collateral standard drives these key design decisions by establishing paths to assess the home’s added risk, it is up to designers to recognize the cascading impact of these unknowns and apply mitigations early for successful home healthcare product development. 

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Rachael Scott is a lead electrical engineer at Key Tech with six years of product development experience. She has been an electrical and system design lead on a number of medical designs, including large development in-vitro diagnostics and patient-care devices. Scott has experience architecting, designing, and testing complex devices relative to 60601 and 61010 general and collateral standards in various capacities including feasibility design, prototype system testing, EMC pre-screening and compliance testing, and formal device verification.