Student Projects
Contact Information
University and Department: Penn State, Department of Bioengineering
Team Members: Chris Goodrich, Stephen Fresta
Primary Email Address:cjg5044@psu.edu
Project Information
Describe the challenge your project is trying to solve.
"Take heart" has many meanings. To our team, it means to have compassion for those we are working for and to incorporate their culture into all aspects of our design. Very literally, it guides us to develop a medical device that will accurately record heart and lung sounds to aid in the diagnosis of common cardiac and pulmonary disorders. Most importantly, take heart means "to be confident or courageous". With Mashavu, we not only want to improve healthcare for patients in East Africa, but we also want to empower them by making Mashavu a sustainable business venture.
Our mission is to develop a relatively simple and inexpensive digital stethoscope to collect heart and lung sounds at Mashavu kiosks.
The goal of Mashavu is to connect patients in East Africa to physicians worldwide, improving their access to pre-primary healthcare. Our goal is to aid in providing that care.
Privacy
One of our first cultural considerations was with regard to privacy, particularly how much privacy would be expected by a patient during a clinical visit. Would female patients be comfortable having these vitals taken beneath their clothing, or should our design be sensitive enough to take measurements through them? We spoke with those who have travelled to Kenya and been to similar health facilities and were informed that the patients are accustomed to having measurements taken beneath their clothing. Therefore, we were able to justify sacrificing some noise-reducing technology in our design.
Common Diseases
While a stethoscope is well known for its use in listening to heart sounds, the device, if made sensitive enough, can also be used to listen for abnormalities in the lungs. Pulmonary disorders are common in developing countries like Kenya and Tanzania where ventilation is poor and women and children are often exposed to smoke and pollution (NYT article by Amanda Haag from class). An accurate stethoscope can aid in the diagnosis of these pulmonary diseases, like pneumonia in children and bronchitis or emphysema in adults.
Describe how you addressed the challenge through your project.
The Mashavu stethoscope design is modeled similarly to a professional stethoscope and includes a computer interface feature as well as an inexpensive construction plan.There are four main components to the design concept.
1. Conical Chest Piece: A conical shape was decided on for the chest piece because of its ability to condense the sound vibrations from over a circular surface area over the skin. In order to maintain a low cost, a small funnel found in Wal-Mart, was used for the chest piece.
2. Amplification Tubing: A small hole from the funnel then transfers the condensed sound vibrations through about a foot of ¼ inch latex tubing. From testing, it was found that the latex tubing does amplifies the sound slightly.
3. Reverberation Chamber: The latex tubing fits directly into a 3/8 inch clear vinyl tube that is 4 inches long. The vinyl tube is the reverberation chamber, where the sound vibrations can resonate and be picked up by an electret microphone.
4. Electret Microphone: Two different micrphones were used in the design. A basic electret microphone from RadioShack and also a computer microphone found online. Both were inexpensive options, costing under six dollars. The microphone fits securely in the end of the vinyl tubing. Each connection made throughout this design is a tight and clean fit to ensure proper sound wave conduction. The electret microphone can pick up frequencies ranging from 30 to 15,000 Hz and requires 4 to 10 VDC. The microphone was wired to an adapter jack, so that the design remains simple and can plug directly into a headphone jack on a computer. The daq device is not needed and the votage is suplied through the computer connection. The computer microphone picks up frequencies ranging from 20 to 15,000 Hz and does not require voltage.
Figure: A diagram of the completed design that is labeled with each component.
Table: Cost Anaylsis
Final Design | Cost ($) |
mini funnel | 0.38 |
vinyl tubing | 0.13 |
latex tubing | 1.57 |
electret microphone and computer jack | 2.79 2.99 |
total cost | 7.86 |
* Note: the computer microphone is only $1.25, which makes the total cost for that prototype $3.33.
In order to convert the stethoscope’s captured sound waves to a digital signal and eventually to interpretable data, the physical sound must be converted to an electric signal and then processed using a computer.
The microphone generates an analog signal, which is fed into the computer via the computer's built-in TRS "line-in" or microphone jack. Within the computer, the signal is accepted and interpreted by LabVIEW.
In LabVIEW, the signal may be manipulated by the user for clarity and visualization. The signal can be played back through the computer speakers or headphones in real-time. The signal can also be digitally amplified and filtered to remove background noise as needed. For simplicity of use, two filter settings, "Heart" and "Lungs" are available to the user, which filter out frequencies above 200 and 1000 Hz, respectively. The resulting amplified and clearly audible heartbeat sound can be recorded and saved to a .wav file and is automatically presented as a signal waveform in graphic format as well, for later review.
*The blockage shown in this diagram, was put in place to act as a filter. Later in the design process, a filter funtion was added to the Labview and the block was removed.
Testing
The stethoscope design consists of a conical chestpiece that transmits sound through a reverberating chamber to a small elecret microphone. The electret microphone is supplied a nominal voltage of 5V by a data acquisition (DAQ) device. The other microphone leads are attached to a headphone jack that can be connected to a computer. The signal from the microphone is then sent to LabVIEW, where the sound is filtered to remove higher frequency background noise. Peak-finding capabilities of LabVIEW have also allowed for the determination of a heart rate by analysis of the signal. The result is a numerical heartbeat and an audible sound file for the physicians to analyze.
