Critical Care Devices: UI Design Essentials
- Posted by Erika Lobo and Chris Justice
- On July 16, 2021
- Critical Care, UI/UX, usability, user interface
The patient has suddenly taken a turn for the worse. He collapses in bed and begins to shake uncontrollably. A once quiet room is now filled with the sound of persistent, loud alarms. In seconds, a clinician must interpret the screen of a critical care monitor to determine what’s wrong.
The ability of a critical care monitor User Interface (UI) to deliver easily decipherable information often means the difference for patient survival. While this scenario might seem intense, it’s one of many use cases to account for when designing the user interface of a medical device used in critical care settings.
This article describes common user interface (UI) elements of critical care medical devices. These UI considerations help communicate important information quickly and effectively, while avoiding human factors mistakes that could be life-threatening.
In our work designing critical care monitors, we have come to appreciate common design considerations that are unique to critical care. Many in our industry have created excellent User Interfaces, by necessity. In the same way that most rocket designers place the fins in back and cone up front, many good critical care UI’s share common design best practices. Here are five essential characteristics of critical care medical device user interfaces.
1. Information hierarchy
The rapid visual recognition of key information is a must for critical care clinicians. When well-designed, a UI places important primary information (such as real time vital readings) up front, readable at a distance. Secondary and tertiary information like historical data is available, but doesn’t visually clutter the display. Items like Wi-Fi status and battery charge level are there, but don’t distract. Users can drill down into secondary menus when needed. And on-screen text is kept to an absolute minimum. Despite text minimization, there is still a lot of information on the display, but only essential text earns screen real estate.
2. Legibility
Critical care monitors make diligent use of clean typography of adequately-large type size. Key information is displayed at a type size that can be read across the room, and sometimes from outside the patient room. A study published in Displays technical journal found that fonts size 45pt had better response speed and accuracy than sizes 35pt and 55pt[1].
Sharp color contrast further helps information to be accurately interpreted[2], even by users with imperfect eyesight or at a distance or while wearing PPE. Many critical care monitors use color text on a black background, which is readable in all ambient light conditions from a darkened cath lab to a room where patients may be trying to sleep, or a night transport scenario.
3. Streamlined user interface
Critical care UIs nearly all follow a modernist design ethic (form follows function, with non-essential elements removed). For example, these UIs don’t use unnecessary bounding boxes around waveforms of different parameter types; grouping is accomplished by color and proximity. It’s uncommon to see large numbers of visually bordered windows in these critical care monitors because the windows are unnecessary. Overly complex graphics and animations are seldom used because they are difficult to interpret and possibly distracting.
4. Standardization
Common visual design language is a hallmark of critical care user interfaces. Most critical care monitors look similar, use similar design language, organize information in similar ways, place interactive elements in similar locations. There are variations, but these are employed sparingly. Common design language helps clinicians who are trained on one manufacturers system to easily understand another manufacturers.
As an example, different physiological parameters are generally displayed similarly. For example, ECG and SpO2 both use scaled waveforms off to one side, with the present numeric value larger and off to the other. Some of this standardization is driven by design constraints (black background work best in light or dark rooms), so most manufacturers abide by the same constraints. Others are driven by historical precedent.
Our medical device industry relies heavily on standards, which include standards for iconography and standards for audible alarms. This is why clinicians intuitively recognize a high priority alarm from a new device, even without being trained on the new device. Alarms sound similar – by design!
For example, the table below shows visual standards for communicating alarms visually. This table is pulled from IEC 2020 Table 2 – Characteristics of alarm indicator lights[3]. Consistency of color, flash pattern and duty cycle all work together to make an intuitive interface for clinicians. This standardization of color, pulsing or flashing pattern creates a common guide to quickly assert the severity of a warning and the actions then required.
| Alarm Category | Indicator Color | Flashing Frequency | Duty Cycle |
| High Priority | Red | 1.4 Hz to 2.8 Hz | 20% – 60% on |
| Medium Priority | Yellow | 0.4 Hz to 0.8 Hz | 20% – 60% on |
| Low Priority | Yellow or Cyan | Constant (0n) | 100% on |
While the alarm icons below may not make sense to many people, they are the standard for medical devices. Clinicians who learn the meaning of icons on one monitor will recognize them as familiar on all monitors. These icons are standard, defined by IEC 2020 Table C.1 – Graphical Symbols for Alarm Systems[4]. Critical care monitors make excellent use of these standardized symbols, partially because this is required by standards bodies.
5. Interactive elements grouped
Many critical care monitors eschew clickable elements on every point of the screen, instead pushing the interactive elements (such as buttons) to the bottom and top of the screen. This positioning allows users to access touchscreen features, without putting sometimes wet or dirty hands in front of critical information. This consistent positioning also keeps the user interface streamlined; users have been trained to intuitively know where the interactive elements are anchored.
The Bottom Line
The way that Multiparameter Monitors display information is a matter of life and death. While there isn’t a set recipe for a perfect monitoring system, we find these UI design elements to be essential for any critical care monitor. We employ these elements as part of our broader Human Factors/Usability Engineering practices to design ultra-usable interfaces, and to validate with real users that our designs meet the mark. Because we know lives depend on it!
[1] Xiao-Teng Tang, Jun Yao, and He-Fan Hu. “Visual search experiment on text characteristics of vital signs monitor interface.” Displays, vol. 62, April. 2020, pp. 3-4. ScienceDirect https://doi.org/10.1016/j.displa.2020.101944. Accessed 09 July 2021.
[2] Xiao-Teng Tang, Jun Yao, and He-Fan Hu. “Visual search experiment on text characteristics of vital signs monitor interface.” Displays, vol. 62, April. 2020, pp. 4. ScienceDirect https://doi.org/10.1016/j.displa.2020.101944. Accessed 09 July 2021.
[3] International Organization for Standardization. (2020). Table 2 – Characteristics of Alarm Indicators (IEC Standard No. 6.3.2.2.2). https://www.iso.org/standard/63787.html
[4] International Organization for Standardization. (2020). Symbols and Markings – Table C.1 – Graphical Symbols for Alarm Systems (IEC Standard No. 60417-5307;5309;5319;5576;5576-1,2; 5576-3; 5649;5650;5651;6334A;5576-4;5576-5, ISO Standard No. 7000-1326). https://www.iso.org/standard/63787.html
ABOUT THE AUTHOR(S)
An Industrial Designer, Erika is a nuclear-powered designer focused on medical devices at Engenious Design. Her work at Engenious balances usability, aesthetics and pragmatic considerations in collaboration to create medical devices and high technology systems.
Chris has accumulated many lessons-learned from 22 years of medical device design. Chris is principal and co-founder of Engenious Design, a medical device design firm that works with complex electro-mechanical & embedded software systems that are developed from scratch, acquired, and multi-generation products.
