Vanderbilt University School of Engineering

Departments of Biomedical Engineering and Chemical and Biomolecular Engineering

Laura Allen

James Berry

Casey Duckwall

David Harris

Professor Franz Baudenbacher (Advisor)

Mary Judd (Administrative Contact)

Justin Cooper (EWH Contact)

Project title

Non-Electronic Blood Pressure Assist Device

Abstract

While a large deal of research has focused on the elimination or the alleviation of “major killer” illnesses, the leading cause of death in the world is still cardiac illnesses.1 Blood pressure measurements are essential to heart health diagnosis. A traditional sphygmomanometer requires that its user be trained to detect ennui while measuring an individual’s blood pressure.

When a sphygmomanometer is first inflated it compresses the artery, allowing no blood to flow. The sphygmomanometer is gradually evacuated, lowering the pressure on the blood vessel. The pressure at which the first vibrations are detected in the cuff is the systolic pressure. As more pressure is released, the number of oscillations transmitted will first increase before later decreasing. The pressure allowing maximum transmittance of oscillations is the mean blood pressure. Finally, the pressure at which oscillations once again cease being transmitted to the device is known as the diastolic pressure.2

Engineering World Health is an organization dedicated to overcoming obstacles facing public health in developing nations using engineering and innovative designs. Alongside this organization, we propose the design of a device that would act as a supplement to a traditional sphygmomanometer, amplifying the region of pressures over which blood pressure oscillates. This allows for much simpler readout of sphygmomanometer data. The device should allow identification of at least systolic blood pressure, if not both systolic and diastolic pressures. Additionally, it should be durable with an extremely low cost and simple production parameters.

Project tasks:

Determination of mechanical identification of pressure
Design of a cheap adjunct to traditional sphygmomanometer
Ensure ease-of-use of device

Proposal Narrative

Introduction

According to the WHO1, each year cardiovascular diseases kill more people worldwide than does any other individual cause. Even in developing nations, where life expectancies are shorter and thus death from chronic disease is not as prevalent, heart disease and other related illnesses (e.g. stroke) are still very high on the list of leading causes of death. Thus, although cardiovascular disease is not as high-profile a killer as other more in-vogue issues like AIDS and malaria, these statistics clearly demonstrate that it is still the greatest health problems facing the world today and is very much worthy of attention.

Hypertension, or high blood pressure, is one of the primary risk factors for illnesses like heart disease and stroke, and so managing this condition is vital for the long-term health of its sufferers.2 However, such a goal is no trivial matter in the developing world, where even diagnosing the condition can be a challenge. Accordingly, health organizations are beginning to make a concerted effort to identify and treat hypertension as a way to quickly improve living conditions in the developing world.

Engineering World Health (EWH), an organization that works to mobilize “the biomedical engineering community to improve the quality of health care in vulnerable communities of the developing world” has announced the development of an easy-to-use, non-electronic blood pressure measurement-assist device as one of their annual “Projects That Matter.”3 This project seeks to develop a cheap add-on that could be used in conjunction with a traditional sphygmomanometer to visually identify both the systolic and diastolic pressures and, thus, enable minimally-trained personnel to take blood pressures. Since second-hand sphygmomanometers are readily-available and the add-on would necessarily be cheap, it would be easy to implement in any part of the world. In doing so, the pressing issue of diagnosing hypertension in the developing world, where there is a decided lack of fully-trained medical personnel, would be greatly alleviated.

History and Context

To begin our design process, we did a literature search to identify existing methods for measuring blood pressure. According to the American Heart Association, the most common method is the auscultatory method, which uses Korotkoff sounds to identify systolic and diastolic blood pressure. The brachial artery is occluded by an inflatable blood pressure cuff, which is connected to a sphygmomanometer. A stethoscope is used to listen for the appearance and disappearance of sounds thought to be caused by the turbulent flow of blood underneath the cuff. The initiation of sounds signals systolic pressure and the termination of noise represents the diastolic pressure.2

A second method for obtaining blood pressure without a stethoscope is the oscillatory method. This method measures the oscillations in pressure from a pressure above the systolic pressure to below the diastolic pressure. The maximum oscillation is called the mean arterial pressure, which can be used to calculate systolic and diastolic pressure. One issue with this technique is that the amplitudes can depend on other factors besides blood pressure.2

A third common method for measuring blood pressure is called tonometry. This involves measuring the pulsations of an artery as it is pressed up against bone. It is most commonly practiced at the wrist, where the radial artery lies over the radius bone. Other methods for measuring blood pressure include a finger monitor or ultrasound. None of the methods described above are invasive.

We have decided to use the oscillatory method for our design. At this time, we have no drawings or prototypes to share.

Team

The team consists of four undergraduate engineering students in their senior year. Laura Allen is studying chemical engineering and medicine, health, and society (MHS). David Harris is studying chemical engineering, chemistry, and mathematics. James Berry is studying biomedical engineering, and Casey Duckwall is studying biomedical engineering, chemistry, and mathematics. The team was formed because of their common interest in the medical device needs of developing countries and their diverse backgrounds in undergraduate coursework. Every team member has a foundation in basic engineering principles and design accompanied with experiences in various medical settings. Each member will play an active role throughout the design process. The team has recently acquired an on-campus advisor, Professor Franz Baudenbacher. He is a professor in the Department of Biomedical Engineering.

Work Plan and Outcomes

We have several goals that we hope to achieve through our participation in designing an easy-to-use, non-electronic blood pressure measurement-assist device. Our two primary goals will be (1) to learn about the engineering design process and how it works so that we will have all the tools to design effectively in the future, and (2) to submit a feasible design that could be successfully implemented in the developing world. If we are able to accomplish both of these goals, the process will certainly qualify as a success.

To accomplish our goals, we will learn and follow standard engineering design protocols throughout the process. This will include setting out a detailed list of checkpoints on a timeline as well as frequently reviewing these goals for completion status and/or reevaluation as we progress through the year. We will seek frequent guidance from more experienced engineers regarding both the planning and technical design portions of the project to ensure that everything is moving forward as it should and to adjust as needed. We will also meet regularly as a full group, even during times that we may be focusing on separate aspects of the project, to maintain a well-organized and congruous plan. We feel that these steps will maximize our possibilities for a successful final product at the end of the course.

At the end of the project course in the spring, we will hopefully have a working prototype design that meets all of the specifications set out by Engineering World Health. At that point, we will submit this final design to EWH in the hope that it will be accepted as the winner of the design competition. If it is selected as the best solution to the blood pressure project and chosen for implementation in the field, we will then have the opportunity to continue on with the project and help out with its deployment overseas. This would be a great opportunity to witness the impact that our work will have in actual use.

Evaluation and Sustainability Plan

The blood pressure assist device is intended to be usable by clinics in developing countries. Therefore, success of the device will be based on how well it achieves this main goal. Several factors will be evaluated as indicators of usability in remote clinics. If the device is affordable (less than $5) then it will have met cost goals. Also, to succeed it is very important the device be non-electronic because some clinics may not possess electricity. Along those same lines, durability will be factored into the success of the device because it is important for the device to be able to withstand conditions present in developing countries. The device’s ability to amplify the oscillatory signal and its ability to visually distinguish the systolic pressure will be indicators of its usability by minimally trained users. It is also important that along with the usability of the device we design understandable instructions for operation of the blood pressure system, using pictures to allow the training of a wider population. In general, our success will be measured in the development of a durable, inexpensive, easy to use blood pressure device that can be readily implemented and maintained.

References

(1) WHO. “Fact Sheet: The Top Ten Causes of Death.” WHO. November 2008. Accessed October 28, 2009 < >.

(2) Pickering TG. , Hall JE, Appel LJ, Falkner BE, Graves J, Hill MN, Jones DW, Kurtz T, Sheps SG, Roccella EJ; Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Recommendations for blood pressure measurement in humans and experimental animals: Part 1: blood pressure measurement in humans: a statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension. 2005 Jan;45(1):142-61.

(3) EWH. “Who We Are.” EWH. 2009. Accessed October 28, 2009 < >.