In July 2010, the FDA released a warning on a number of fibrin-based bleeding control products that were demonstrated to cause air embolisms in patients when used improperly during surgery. The article reported that the embolisms, though rare, could be caused by the clinician using pressure settings that were too high, or when the sprayer tip was held too close to the bleeding site. The FDA has emphasized that clinicians need to follow the manufacturer’s recommendations for use and those instructions have been rewritten to make the hazard more clear. The FDA also recommended that clinicians should monitor patients for signs of embolism.

Ergonomic assessment tool developed to understand optimal comfort range for a handheld device.
Unfortunately, this is not an unusual situation. A recent FDA report indicated that each year, more than 100,000 medical errors involving medical devices are reported. Over one-third of them were due to use error. While there is the temptation to blame the user for using a device incorrectly or not following instructions, very often the device itself might invite incorrect use. Poor user interface, awkward controls, overly complicated operation are just a few aspects of product design that may increase the chances that the user will make an error. Devices can be designed to better mitigate errors or misuse, and the FDA is making a new push to ensure that device developers consider usability of the device early and often in the development process.

In light of this pressure, the field of Human Factors is receiving increased attention within the device community. The new HE 75 Guidelines, published by the ANSI/AAMI (American National Standards Institute/Association for the Advancement of Medical Instrumentation) and endorsed by the FDA, describe Human Factors as the relationship between humans, the tools we use, and the environments we live in. This includes awareness of human capabilities, limitations, and tendencies. With the primary goals of improving patient safety and reducing user error, Human Factors Engineering (the application of the principles of the field of Human Factors) has become a critical component in the development of surgical instruments.

The FDA requires manufacturers to evaluate the Device-User System for possible hazards, looking across the use environments, user characteristics, and device characteristics. In fact, the FDA identifies 11 different areas for a developer to consider when working on a device — from aspects such as light, noise, and vibration within the use environment (the actual location where the device will be used by a person), right down to the device itself, including its complexity, procedures, and user interface.

Human Factors in Prototyping

A designer's rendering of a physician's simultaneous range of vision and motion in a clinical setting. This is used, for example, to inform the optimal height and distance of a device screen in the oper- ating room.
Understanding exactly how the FDA wants to see evidence of the integration of Human Factors Engineering can be a challenging task for device makers. Following the principles of Industrial Design, the Human Factors experts at Ximedica, a medical device development firm based in Providence, RI, have developed a system that is embedded in every device design project. The “Cross-Phase Usability Assessment Tool” allows a project manager to ensure that all HF concerns are considered during every phase of development, from the initial collection of user needs, to verification and validation. It aids the project team in considering people (users and stakeholders), ability (human capacity), place (type of environment in which the device will be used), and task (user actions), as the design and engineering of the device proceed. “Human Factors and Industrial Design are complementary fields, and when they are tightly integrated, it results in a smarter and safer device,” says Aidan Petrie, chief innovation officer and co-founder of Ximedica.

Two recent projects at the firm illustrate the application of Human Factors engineering to the design process. In one, an early-stage device design arrived at Ximedica as an innovative and technically proven concept, complete with a breadboard model. The client asked the Ximedica team to determine the best system configuration for the end user. This was a device to be used regularly during surgery, and its previous version had often been criticized for taking up too much space and possibly presenting a tripping hazard to the busy clinicians. The focus on usability and hazard reduction was indeed necessary. In order to best understand how these hazards affected care and how different product designs might affect handling and safety, several non-working prototypes were built to scale. Surgeons and scrub nurses were invited to “use” the device in an operating room that was set up at a nearby hospital training/simulation center. Complete with all the appropriate equipment and mannequins on the OR table, these clinicians showed the designers and engineers how they would pick up and manipulate the device around the patient. They also simulated what would happen to the device should the team need to move the patient during surgery. With more than 20 surgeons and nurses participating in structured interviews and observations, this human factors engineering effort provided invaluable feedback as to how to ensure that the design minimized interference with the patient and his or her care.

The second project involved another device that was also a system used in surgery. It was made up of several components, including a large power supply and a handheld instrument. During its development, the project team utilized the Usability Assessment Tool to evaluate the system, including important aspects of the user interface (the method through which the user interacts with the device). While the client wanted to make the interface as simple as possible, interviews with users indicated that the prototype interface (using computer simulation) was too simple and did not meet the needs of surgeons who were looking for more specific data from the system. In this case, it turned out that oversimplifying the interface could have led to user error due to feedback ambiguity. Fortunately, the assessment had been done using computer simulation, allowing appropriate changes to be made early in development and therefore saving the development team a considerable amount of time and money. “By cross-checking each component against the usability tool, we could show our client, and eventually the FDA, that we were conducting our due diligence to ensure that the design was optimized for success in the OR — both for the doctor and the patient,” said Breck Petrillo, engineering manager at Ximedica.

Assessing the impact of Human Factors is a critical element of device development. In the OR, with many clinicians working quickly under a great deal of stress, and with device alarms regularly going off, distractions abound. Sometimes a manufacturer’s rep may be present to help with a device, but this is rarely the case. In order to fully assess the usability of a surgical device, users must be involved in the early stages of product development and concepts, and prototypes must be tested in the true use environment (or close simulation) with real users. The FDA will increasingly expect more evidence that such testing has taken place in new applications — investigating all aspects of usability (environment, user, and device) will make the path to regulatory approval a little smoother.

This article was written by Tiffany L. Hogan, Ph.D., Research and Product Strategist at Ximedica in Providence, RI. For more information, Click Here .