How Human Factors Lead to Medical Device Adverse Events
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.
Design considerations
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.
Visual considerations:
- 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.
Auditory considerations:
- 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.
Tactile considerations:
- 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.
Reporting problems
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. See the
nearby link to 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.
REFERENCES
1. FDA’s Human Factors Program: Promoting
safety in medical device use.
http://www.fda.gov/cdrh/humanfactors/index.html. Accessed March
27, 2008.
2. Sawyer D. Do it by design: An
introduction to human factors. http://www.fda.gov/cdrh/humfac/doit.html.
Accessed March 27, 2008.
3. Rich S. Medical devices and patient
safety: The role of human factors. Association for Vascular Access
Pre-Conference, Indianapolis, Ind., September 8, 2006.
4. Food and Drug Administration.
Manufacturer and User Facility Device Experience (MAUDE).
http://www.fda.gov/cdrh/maude.html. Accessed March 27, 2008.
5. Eakle M, et al. Luer-lock misconnects can be deadly. Nursing2005. 35(9):73, September 2005.
Suzanne Rich is a senior project manager of the patient safety staff
at the Office of Surveillance and Biometrics, Center for Devices and
Radiological Health at the Food and Drug Administration in Rockville,
Md. (Article reprinted from June Nursing2008, Volume 38, Number 6, Pages 62-63)
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Source ~ FDA
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