ADVERSE EVENTS involving medical devices or equipment can lead to serious problems, including incorrect or delayed diagnosis and treatment or patient injuries. When errors involving medical devices recur repeatedly, people typically blame the users instead of the real culprit, which is often a poorly designed interface between the medical device and the user. Human factors is the science that focuses on understanding and supporting how people interact with technology.
In health care, the objective of human factors is to improve human performance with medical products, including medical devices, and to reduce the likelihood of error or injury, thus improving patient and workplace safety.1 In this article, I'll discuss some common problems and steps you can take to prevent them.
The complexity and diversity of medical devices used simultaneously contribute to human factors errors. A key objective of human factors in medical device design is to enhance the likelihood of good performance under less-than-ideal conditions.
To minimize human factors problems, devices should be designed according to users' needs, abilities, limitations, and work environments. This includes the design of the device's user interface, which includes controls, displays, software, labels, and instructions—anything the user may need to operate and maintain a device.
Good design should include:
- operation that's intuitive and doesn't require frequent reference to an instruction manual
- easy-to-read displays
- easy-to-use controls
- appropriate connections of device-to-device and device-to-outlet for safe use
- effective alarms
- easy repair and maintenance.2
Consider three major areas when evaluating medical-device-related adverse events from a human factors perspective:
- user characteristics, including the person's abilities and training and her expectations of the device
- device design considerations, which focus on the device-user interface, including instructions for use
- the environment in which the device is used, including the lighting, noise, distractions, and time constraints.1,2
Let's examine these elements in more detail, starting with the device user. For examples of errors in each major area, see Troubling human factors problems.
Training and expectations
Make sure everyone using a device has received training on it.Then consider a less obvious factor, the user's expectations of how the device works.
Whether a user is a health care professional or a patient, she may expect a device to work like another device that looks similar. For example, based on her experience, she may expect a device to deliver the same prescribed treatment or dose as a similar device, or expect the alarms to be in a specific sequence or pattern of sounds. Many reported I.V. fluid pump programming errors resulted when the actual device function wasn't what the user expected.3
Looking at design
A user's ability to interpret or understand device communication is often impaired by incomplete, confusing, or misleading labeling and instructions for use. Ambiguity about the sequence of steps required for device setup and operation can also be a factor.
Sometimes the instructions for use aren't easily accessible, which prompts users to operate devices based on previous experience instead of on the requirements found in the labeling. An example of this problem is when the text or numeric font is difficult to find in the device's display panel.
When similar devices are made by different manufacturers, the vocabulary in text displays may be inconsistent. For example, adverse events have involved devices that used different units of measure, such as cubic centimeters instead of milliliters. When devices display unfamiliar text abbreviations or words, this may further compound difficult or confusing navigation through menus to set up the device, leading to errors.
Make sure that when your facility chooses devices, it takes into account the following visual, auditory, and tactile features of the interface between user and device.
- The user can see the device displays, labels, or markings.
- Display screens are easy to see, have clear contrast, and are bright enough to be seen without glare.
- The font is large enough to be read by all users.
- The user can easily hear and interpret alarms.
- The sequence of sounds is appropriate in volume, frequency, tone, and pitch.
- The alarm's timing clearly defines the acuity of the warning and gives the user enough time to make adjustments and corrections.
- The device's components can be connected easily.
- The device's components can't be easily disconnected or connected by mistake. (Problems have been reported with some electrodes, cables, and I.V. tubing.)
- The device's components can be connected so that the user feels a “click” to help ensure a proper connection.
- The user can feel the controls of knobs, buttons, switches, and keypads.
Instructions for maintaining and cleaning the device should be clear and include what compounds can and can't be used. Some devices, such as electronic medical devices, shouldn't be cleaned with fluids, which can leak into the device housing and cause performance problems and even fires. Some cleaning agents may degrade or otherwise affect a device's plastic casings, impairing performance.
Consider the environment
Both user and device performance can be influenced by physical characteristics of the environment, such as adequate lighting, clear and unobstructed views of devices (especially those used for monitoring), and controls for temperature and humidity.
These workplace constraints can contribute to medical device errors or adverse events:
- staff with heavy workloads, such as multiple high-acuity patients
- staff working double shifts
- float and temporary staff who may be unfamiliar with the unit's equipment
- different brands or models of the same type of equipment within the same facility. Some organizations have moved to using a single brand or model throughout their facilities.
If an error or an adverse event occurs despite your best efforts, take action. Medical-device-related adverse events involving death or serious injury must be reported. Reporting near misses or events that could cause patient harm can help identify system improvements that can prevent similar adverse events in the future. Follow your facility's policies and procedures. You can report events to MedWatch online at https://www.accessdata.fda.gov/scripts/medwatch/.
Addressing human factors in both the design and clinical use of medical devices mitigates risk, improves patient safety, and improves workplace safety.
Troubling human factors problems
Adverse events reported to the Food and Drug Administration involving human factors errors range from the simple to the complex. Here are examples of errors in each major area involving human factors:4
User expectations. One error involved an otoscope and transilluminator that look similar but have different light intensities. During an urgent intervention, the health care provider picked up an otoscope, thinking it was a transilluminator. When he tried to use it to locate a child's vein for an I.V. catheter insertion, the patient experienced a second-degree burn.
Device design. Another error concerned noninvasive blood pressure (BP) tubing that was mistakenly connected to I.V. tubing. The patient, who was being monitored in the ED with a noninvasive automatic BP device, also had an I.V. catheter. The BP cuff tubing was disconnected when the patient went to the bathroom, and it was reconnected upon his return. The patient's wife found the patient “blue from the neck up.” Despite resuscitation efforts, he died. The BP cuff tubing had been connected to the I.V. catheter and had delivered about 15 mL of air. An autopsy confirmed a fatal air embolus.5
Environment. A safety issue was reported when newly purchased ventilators were placed into service in a trauma ICU. Staff immediately noted that the ventilators had an alarm that wasn't audible when the patient-room door was closed. Although the devices weren't defective, they weren't suited to the environment where they were being used.