Creative Collaboration: User-Centered Design in Practice

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

Originally Published March 2000

A case study of the development of a blood parameter monitor illustrates the benefits of teamwork and human factors engineering during the design process.

In 1993, CDI Products (Tustin, CA), part of 3M Health Care's (St. Paul, MN) cardiovascular sytems department, began development work on its next-generation blood parameter monitor, the System 500. Blood parameter monitors are used by perfusionists during cardiopulmonary bypass procedures to continuously provide ongoing information about critical blood parameters, such as pH, CO₂, and O₂. CDI chose to partner with an outside consultant for this project to develop and adhere to a user-centered design process. It selected the design and engineering consultancy IDEO Product Development (San Francisco), a firm with a background in the development of medical devices.

The finished product, released in the middle of 1998, was the result of a strong collaboration in which user-centered design played a crucial role throughout the development process. CDI considers the System 500 a breakthrough product in terms of ease of use, accuracy, amount of data collected, and overall design methodology. This article discusses the product, the team, the initial problems and opportunities identified in the early stages of the design process, and the ultimate solutions discovered

THE PRODUCT

The System 500 blood parameter monitor is a small, pole-mounted product with an active-matrix color LCD screen and a companion calibration device with two gas bottles (Figure 1). It measures 11 X 12.5 X 6 in. and weighs 16 lb. It includes three optical probes on the right side of the device for measuring the various arterial and venous blood parameters.

CDI's System 500 blood parameter monitor.

The front of the System 500 (Figure 2) has three areas of navigation: buttons for soft labels on the right side of the screen, buttons for navigating the system map (or steps in the procedure) along the bottom of the screen, and a general navigation and confirmation area below the screen. The back of the product, shown in Figure 3, has an area for cable management, power connections and data ports, and a cover for the printer

The System 500 uses an optical fluorescence technology to measure blood gases, pH, and potassium. In addition, it uses an optical reflectance technology to measure oxygen saturation, hematocrit, and hemoglobin

THE DESIGN TEAM

Development of a complex device requires the input of specialists from design and engineering. The System 500 team included personnel from CDI and IDEO who were experts in human factors, industrial design, interaction design, chemistry, optics, manufacturing, and mechanical and electrical engineering. Core technology and engineering was performed in-house by CDI; IDEO's people focused on overall design from the process standpoint.

Figure 1. Cutaway view of the active-matrix LCD screen (a) and calibration device with two gas bottles (b). The optical sensors (c) measure arterial blood, venous blood, and hematocrit saturation.

Experts in human factors provide the insight and connection with the end-user that allow designers to create user-centered devices. Human factors specialists come from backgrounds in cognitive psychology, anthropology, human factors engineering, and ergonomics. The role of human factors is to keep the focus on people within the context of technology, tackling those issues—physical, cognitive, social, emotional, and cultural—that affect the success of the design. The process includes collecting market research, evaluating competitive or current products, and performing ergonomic evaluations and ethnographic studies—that is, observing and interviewing people in their usual environments to learn the rituals and behaviors they engage in when using products in real-life situations.

Challenges for the System 500 project included analyzing the entire operating room environment to understand the context in which the product is used; considering the different steps in a typical procedure and how the product can support those steps; and exploring concerns for user input, weight, visibility, and feedback.

Industrial Design. Industrial design shapes the interactions between people and products by asking the simple questions about how people relate to a product: Who uses it? What is it used for? What will be important in the device-user interaction? What opportunities exist to make the product special or to reflect a company's identity? Is there a possible design solution that will have an immediate appeal as well as give satisfaction and enjoyment throughout the life of the product? Industrial design encompasses more than aesthetic styling; it provides the sensory cues and visual semantics that enable a user to have a successful and emotionally gratifying user experience.

For the System 500, industrial designers needed to consider an appropriate design that conveyed ease of use without appearing sterile or intimidating. In addition, they needed to address numerous functional concerns, such as the positioning of sensors, cable management, the presentation of user input, and the location of peripheral functions such as printing and calibration.

Interaction Design. Interaction design is often thought of as interface design. It extends beyond interfaces, however, especially when that term includes both hardware and software. Interaction design focuses principally on designing the user experience, whether that experience pertains to an object with simple mechanical controls, a product with sophisticated displays, computer-based graphical user interfaces or media-rich software, or information management and interaction within environments. The skill set is equally broad: information design, communication design, user interface, and issues of navigation, structure, time, and behavior.

A particularly critical design challenge for the System 500 was creating an appropriate conceptual model for the user interface—how to give the users a sense of where they are in the procedure and what their next step will be. Connecting the on-screen interface to the hardware and its input devices was equally important, as was deciding how to display and organize a wealth of data about the procedure.

Figure 2. For user navigation, the System 500 has buttons for soft labels on the right (a), buttons for navigating the system map along the bottom (b), and a general navigation and confirmation area below the screen (c).

Science and Engineering. The foundation of product integrity is based in both science and engineering. Although their contributions to a product are often not immediately visible to the user, it is scientists and engineers who determine the reliability of the product, develop solutions for complex mechanisms and electronics, provide evaluation models for testing prior to manufacturing, lower manufacturing costs by reducing the number of parts, source new manufacturing processes, and lower assembly costs.

Although this article focuses on the System 500 design solutions, engineers played a crucial role in making those solutions happen, from improving the performance of the electronics to sourcing display technologies appropriate for the operating room environment.

The Collaboration. CDI and IDEO were partners during the design and engineering process. It was the responsibility of the project managers to maintain a strong collaborative spirit throughout the process, integrating contributions from all experts involved. CDI brought firsthand knowledge of the product and its users, elaborate sensing technology, and an understanding of manufacturing. IDEO team members brought innovations to the overall design process. The synthesis of these attributes was crucial to the System 500 design.

THE DESIGN PROCESS

Application of a design methodology is important in the development of any product, especially complex devices for the medical industry. For the System 500, IDEO proposed a four-step process leading from research to manufacturing.

Step One: Understand and Observe. During the understand-and-observe phase of the System 500 project, research was gathered to inform the design process. The predecessor product was evaluated using feedback from CDI's marketing department on areas for improvement. At the same time, feedback was obtained from end-users concerning any potential limitations or inconveniences they discovered while using the predecessor product. IDEO also conducted a review of competitive products and other devices in the product line to understand their drawbacks and recognize design opportunities. Designers attended cardiovascular surgery procedures to understand the environment in which the product was used and learn how it fit into the existing system of equipment. Workshops were conducted to role-play device setup, calibration, and operation to identify opportunities for improvement.

As a result of this research phase, a series of difficulties—which translated into design opportunities—emerged:

Step Two: Visualize. During the visualization phase of the System 500 project, the job of the designers and engineers was to explore potential solutions to the design challenges that were identified in the understand-and-observe phase. Engineers provided sketches and prototypes of alternative mechanisms for sensors and probes. At the same time, industrial designers began form explorations with sketches; the designers addressed not only style, but also cable management and the effective placement of controls. Particularly strong design directions were executed using foam models. Concurrently, interaction designers mapped out conceptual models for the user interface and created flow diagrams for content navigation. These preliminary directions were shared among all the team members. From the subsequent conversations, the following directions were chosen for the System 500 design:

Step Three: Evaluate and Refine. During the evaluation-and-refinement phase, initial design directions were brought to a higher degree of resolution so they could be more easily evaluated from ease-of-use and manufacturing points of view. Detailed engineering prototypes were developed for reliability and manufacturing viability. Industrial and interaction designers worked together with human factors specialists to determine the number and location of buttons. Detailed foam models of the product were then created to show form, cable management, and pole mounting. Design directions for the user interface were explored, and a computer-based walk-through of the procedure was created to show the navigation possibilities.

The hardware and software directions were evaluated by CDI and by potential users. Feedback from both groups caused the design to evolve until the product reached a degree of resolution suitable for user trials. During this phase, the following work was undertaken:

Step Four: Implement. Once a final design direction was selected, functional prototypes were prepared for bench testing. CDI completed the tooling, engineering, and software development. IDEO monitored the prototype development to ensure that design integrity was maintained and to help resolve issues that emerged during prototyping.

Figure 3. The back of the System 500, with a large opening for cable management (a), an area for power connections and data ports (b), and a printer cover (c).

Figure 4. The System 500's probes are positioned on the right side, which provides easy access to the calibrator and keeps the probe cables separate from the data and power cables.

DESIGN SOLUTIONS

The System 500 incorporates several solutions and innovations in both hardware and software, many of which stemmed from the initial research of the understand-and-observe phase.

Cable Management. A large, mouth-like opening on the back of the System 500 allows for temporary storage of the power and data cables, keeping excess cable off the floor and away from the ports and sensors (Figure 3). Data and power cabling emerge from the back of the product, while probes are placed on the right side (Figure 4); this setup separates the cables and allows easy access to the calibrator.

Identifying the Probes. To differentiate the arterial and venous probes, each was assembled with a colored stripe—pink for the arterial probe and blue for the venous cable (Figure 5). This color extends to identification labels at the connection points on the System 500. The on-screen interface also extends the color coding (Figure 2).

Figure 5. To enable the user to differentiate between probe cables, the arterial probe cable is colored pink and the venous cable blue.

Improving the Sensors. On the predecessor product, a transparent optical interface material was placed on the backs of the sensors. The hematocrit-saturation cuvette contained an optical window and a magnet to enable the user to verify the correct connection between the probe and the cuvette (Figure 6). In the design modifications for the System 500, the optical window was used again, but the sensor size was reduced and the designers added winged snaps for easy handling. The snap provides the user with audible and tactile feedback when the cuvettes have been properly snapped into place (Figure 7). In addition, the designers used a small-bore chamber and standard luer connectors to allow a more universal application to blood circuits. Finally, the former two-piece disposable sensor was reduced to a single disposable sensor, a change that lowered cost and eliminated extra steps.

Figure 6. The hematocrit-saturation cuvette contains an optical window and a magnet, allowing the user to verify the probe-cuvette connection.

Figure 7. Wings on the calibration cuvettes provide tactile feedback when they are snapped into place.

Creating a Conceptual Model. The procedure for moving through the interface was designed to follow the actions perfusionists take during the cardiopulmonary procedure itself. A system map (Figure 8) across the bottom of the screen tells the users where they are in the procedure and allows them to navigate through each step—setup, calibration, standby, and operate. In the operate mode there are three views the user can toggle through: numeric, graphic, and tabular.

Figure 8. This system map appears at the bottom of the screen and allows users to navigate through each step of the procedure.

Managing Content. Each screen is divided into four distinct areas, as shown in Figure 9. The screens were designed to communicate information clearly and to make the relationships between screen and buttons easily understandable. The typefaces were evaluated for legibility and efficiency; a bold, compressed type was selected for its contrast and because its compressed width accommodates highly variable word lengths (the interface operates in eight languages).

Figure 9. The System 500 screen includes the message bar (a), the central content area (b), the soft label area (c), and the system map (d).

Figure 10. The System 500's numeric data display screen, with the pink arterial values on the left and the blue venous values on the right.

The top of the screen has the message bar, showing the date and time, instructions or error messages, and an animated green status bar that indicates that the device is collecting data. The central content area is where the screen's core information is displayed, as well as any supplemental dialog boxes. The soft label area on the right shows all of the screen-specific functions to which the user has access. The system map at the bottom of the screen shows the current mode. Below the screen are the general input and navigation buttons: + and – keys for adjusting values, a set of four-way directional buttons for basic navigation, and OK and Cancel keys.

Displaying Data. During a procedure, there are three methods for displaying collected data: numeric (Figure 10), graphic (Figure 11), and tabular (Figure 12). The numeric mode shows the current readings taken by the device: the values on the left (in pink) are arterial, the values on the right (in blue) are venous, and the values along the bottom (in purple) are not specific to either arterial or venous blood. Colors were selected to match the color coding on the probes, and colored shading was used both to identify and group values, and to reduce eyestrain.

Figure 11. The System 500's graphic data display screen.

Figure 12. The tabular data display screen for the System 500.

The graphic mode displays historic data by graphing three user-selected values against one another and displaying time in multiple intervals. Users can select up to six different groups of values to monitor during a procedure. The bar of numeric data across the top displays the measured values at a particular point in time; users can move the crosshair to any point along the graph to see specific values. The vertical bar of numeric data on the left shows the current measured values.

The tabular mode displays a table of all measured values, ordered from most to least recent. A horizontal cursor allows the user to scroll through the values to any point in time; because the device measures so many values, the table scrolls both horizontally and vertically, like a spreadsheet. Color coding helps the users locate their place within the spreadsheet. As with the graphic mode, the current values are displayed down the left side of the screen.

THE RESULTS

The commercial release of the System 500 produced immediate results. The improvements in ease of use, accuracy, and consistency, and the addition of new parameters were enthusiastically received by the perfusion community—the resulting market response challenged manufacturing to ramp-up production at a faster rate than was initially anticipated.

The System 500's success was largely due to a strong partnership that emphasized user-centered design. Both CDI and IDEO placed a strong value on design and encouraged exploration and collaboration during the design process.

Note: In July of 1999, Terumo Medical Corp. (Somerset, NJ) acquired 3M Health Care's cardiovascular systems business. The CDI System 500 is now part of the Terumo Cardiovascular Systems product line.

Duane D. Bray is senior interaction designer with IDEO Product Development (San Francisco).

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