Patient monitor human interface design

Hewlett-Packard Journal, Oct, 1991 by Gerhard Tivig, Wilhelm Meier

A design based on human factors leads to an intuitive and easy-to-use human interface for the HP Component Monitoring System.

The design of the human interface for the HP Component Monitoring System involved a coordinated effort of R&D, marketing, and industrial design, working with valuable inputs and feedback from the principal users-the intensive care unit (ICU) nurse and the anesthesiologist. Mg. I illustrates the basic elements of the design process for the human interface.

The functionality of the Component Monitoring System goes beyond the classical real-time patient monitoring functions. The monitor offers extensive support for medical procedures, such as cardiac output and S-T depression and elevation measurements, a powerful data management capability with various calculation and report facilities, and a review facility for alarms and patient information from 'another bed" using the proprietary HP serial distribution network (SDN). This functional complexity had to be handled with a single consistent and simple operating structure so that it did not lead to a complex user interface. Because it is a key element in the user's ultimate buying decision, usability was a critical issue in the design.

Environments and Users

The Component Monitoring System is used in a variety of environments, including the surgical ICU, the neonatal and cardiology ICUs, and the operating room. There is a wide spectrum of users, including the nurse in the ICUs and the nurse anesthetist, the anesthesiologist, and the perfusionist in the operating room.

The primary user in the operating room is the anesthesiologist. Some of the tasks performed are of a clerical nature, such as logging patient and hfe support device data, observing the monitor, and scanning the area. There are also physical tasks, not directly related to the monitor, such as patient preparation, administration of drugs and fluids, and patient observation.

In the surgical and neonatatal ICUs, 90% of users are nurses. The tasks performed by the nurse include 300/o clerical activities, such as recording medical data, writing down and checking doctors' orders, writing down the medication plan, and filling out the patient's flowsheet. The other 70% of the tasks performed are of a physical nature, such as administering fluids and drugs, taking measurements, making physical examinations, ensuring patient hygiene, and performing medical procedures.

In most cases, nurses and physicians have no computer experience. It can be expected that many of them will have doubts about the introduction and use of computer-based monitoring equipment. Therefore, it was considered advisable not to make the Component Monitoring System look like a computer.

The main focus is on the patient. The nurses and the physicians do not have time to interact extensively with the monitor. They are in a crowded and stressful environment, where it is not unusual to encounter critical situations requiring immediate action to prevent degradation of the patient's situation. Clinical personnel also face a wide variety of equipment from different manufacturers, all with different user interface standards.

Equipment training often includes no more than one or two hours of instruction at monitor installation time. The turnover of the nursing staff may be very high. Because the workload is heavy, there is no time to read extensive operating manuals, instruction cards, or help texts. Because of economic pressures on the health care system and clinical personnel shortages, especially in nursing, less time is available for in-service training.

All of this suggests that intuitiveness and ease of use are fundamental requirements for the Component Monitoring System human interface.

Design Objectives

As the performance and computational power of a patient monitor increase, the challenge is how to present and use the medical information provided by the monitor in an easy-to-interpret, simple, interactive way that will lead to more efficient patient care delivery. It is possible to control a monitor with two buttons and a lot of key pushing and watching. It is also possible to have 100 buttons or more for the same job and assign a distinct function to each button. An optimum is somewhere in between.

The main goal was to design a consistent control structure for all applications in the monitor and across all present and future members of the Component Monitoring System family. Working towards a simple model in the user's mind was considered more important than reducing the number of keystrokes required to access a given function to an absolute minimum. Having formed a model of how the system operates, the user can extrapolate how a particular function might work. If the system is consistent, the user's prediction will work, the system will be perceived as easy to use, and user acceptance and satisfaction will increase. The control structure needs to be self-explanatory to the novice user and allow fast access to the experienced user. Access to critical functions requiring immediate action (like silencing an alarm or freezing the screen) should be simple and fast and should not interrupt the user's activity in a given operating window.