The DEPART Device: A Continuous Ambulatory Blood Pressure Monitor; Using Actor Network Theory to Improve the Linear Process Model of Medical Device Development

Examining How Sociotechnical Systems Influence Medical Device Design

The National Society of Professional Engineers (NSPE) states, “the services provided by engineers require honesty, impartiality, fairness, and equity, and must be dedicated to the protection of the public health, safety, and welfare” (The National Society of Professional Engineers, 1993). This theme of responsibility in engineering has been central to my STS courses over the past two semesters, during which we focused on the existence of engineering solutions within a larger context. From examining the steps for problem definition, to critiquing the ethical implications of engineering solutions and failures, we have taken a deep dive into the social and ethical aspects of sociotechnical systems. This has helped me realize that I have a tendency to focus on the technical solution, ignoring the system it exists within. However, the Katrina and Boeing case studies highlighted the detrimental effects of disregarding the social, cultural, and ethical implications of the larger system. My STS topic examined how Actor Network Theory illuminates these social, cultural, and ethical implications within the medical device design process, challenging the current model of design. This critique emphasized that the ability to practice agile design for medical devices creates technology oriented to specific users. I also considered these results as I worked on my technical topic, which focuses on creating and testing an ambulatory blood pressure monitor.

The technical portion of my thesis produced a prototype for a continuous blood pressure monitoring system that can be worn throughout the course of a day. We decided to create this system because of problems with the blood pressure cuffs used in doctors’ offices. This outdated system fails due to ill-fitting cuffs or user-error. It can also produce incorrect readings because of the “white coat effect,” an increase in a patient’s blood pressure due to the stress of being in a hospital or doctor’s office. Our project compared two different metrics for determining blood pressure. The first was the pulse arrival time (PAT), which is the time it takes for a heartbeat to travel from the chest to another location in the body, found using ECG and PPG sensors. We found the PAT to a location on the chest and the fingertip. The other was the differential pulse arrival time (dPAT), which is the difference between the PAT to the finger and the PAT to the chest. My technical work was inconclusive in determining which model was a better predictor of blood pressure. These models should be studied in more depth so they can then be used in future research to create an accurate blood pressure monitor.

In my STS research, I used Stanforth’s treatment of Actor Network Theory to modify the medical device design lifecycle. I found that this cycle attempts to fit the design process into a “stage-gate” model, which is a linear process that occurs in individual phases, without overlap between each step. This is not sufficient because it does not account for large design changes in later stages of the process. The later stages of the medical device design process involve more actors; therefore, increasing fluidity of the process in these stages will allow for more creativity and innovation. By using a fluid model like the one described in Stanforth’s treatment of ANT, a wider range of actors, such as the opinions of patients and physicians, can be considered. This will create devices with a wider appeal and implementation. I also found that the strict nature of the FDA approval process contributes heavily to the linearity of the medical device design process. Continuing to dive deeper into this research could help to illuminate how the FDA process should be updated in order for it enhance innovation, without compromising the safety and efficacy of medical devices. This insight will also help medical device companies to create the best possible technological solutions for patients.

By doing these two projects together, I gained a different perspective on medical device design. My STS research allowed me to focus on the critical social and ethical implications of the design of my capstone project, including the prevalence of hypertension. Simultaneously, participating in the medical device design process through my capstone project allowed me to examine design, including the FDA approval process, in a practical nature. The combination of these projects exemplified how engineering practice fits into a sociotechnical system; in order to create a usable blood pressure monitor, the design process must account for the social aspects of this system, including the physicians and patients who will be utilizing the device. Taking STS courses and working on my STS topic in conjunction with my technical one gave me vocabulary, including using concepts like opinions as intangible actors, to articulate the problems with the medical device design process. This enhanced my own technical design project.

Thank you to my advisor, Dr. Eugene Parker, and the team at Barron Associates. Thank you to Dr. Angadi and Nathan Weeldreyer for allowing us to use their lab and giving advice on our experimental protocol and IRB application. Additional thanks to the University of Virginia Department of Biomedical Engineering, including Drs. Allen and Barker and our TAs, and the University of Virginia STS department, especially Dr. Neeley.

School of Engineering and Applied Science
Bachelor of Science in Biomedical Engineering
Technical Advisor: Shannon Barker
STS Advisor: Kathryn Neeley
Technical Team Members: Kayla Craig, Alex Duerre, Kiersten Paul