Transcript Final Poster - Research

Solar Powered Blood Pressure Assist Device
Laura
Vanderbilt University School of Engineering
1
Allen ,
2
Berry ,
2
Duckwall ,
James
Casey
David
2
Advisor: Dr. Franz Baudenbacher
1
Harris
Department of Chemical and Biomolecular Engineering1, Department of Biomedical Engineering2, Vanderbilt University, Nashville, TN
The Problem
• Hypertension, or high blood pressure, kills more people worldwide
than any other disease, and it is estimated that hypertension
caused 7.6 million premature deaths worldwide in 2001.
• A recent estimate found that the prevalence of hypertension in
SSA is just as high as many developed countries (approximately
30% ), but with lower detection and treatment.
• In a study published by Curb et al., only 75% of healthcare
professionals passed a standardized measurement test after an
extensive training session. This inaccuracy often stems from
• inability to use to Korotkoff sounds to identify systolic and
diastolic pressure
• incorrect cuff placement
• incorrect arm positioning
• incorrect stethoscope placement
• Therefore, we have used
Engineering World Health’s proposal
and set out to design a blood
pressure (BP) measurement
device which can be used to accurately measure BP without
formal training to identify Korotkoff sounds.
Engineering World Health
Device Design
Results
•GE Novasensor’s NPC-100t will detect pressure variations arising from turbulent blood
flow during the pressure regime between systole and diastole
• Range of operation
• Pressure: -30 – 300 mmHg
• Temperature: -13 – 158oF
• Humidity: 10-90%
• The NPC-100t has a 3/16” OD connection. This
can be readily connected to numerous existing
sphygmomanometers through the use of hosing
and appropriately sized T-junctions
Figure 3: NPC-100T pressure transducer
included in the final design
•Output from the sensor will pass through a
differential amplifier of gain 10, to eliminate the
linear voltage drop through the pressure range
•Two SCC2433B-MSE solar cells power the prototype; each generate approximately 3V
indoors and 4.5V in sunlight
• Two red LEDs as well as the existing pressure gauge from the sphygmomanometer will
be used to allow easy operation of the device: one as “power indicator” and one in
response to oscillations.
• In testing, the chosen solar cells produced approximately 1.5V in
indirect sunlight inside the BME lab, conditions similar to those we
expect to be encountered in the field. This voltage was very stable,
with few oscillations to disturb our sensor output.
• After verifying the stability of the solar cell output, we assembled
the circuit as described previously. Pumped up to physiological
pressures, we simulated heart-beat oscillations by gently tapping
the cuff. These oscillations are easily identified (see below).
• These oscillations will be used to light an LED that will indicate
when the pressure is between systolic and diastolic.
Project Goals
• The primary goal of this project is the development of an adjunct
device to an existing blood pressure cuff that aids in the visual
identification of systolic blood pressure.
• The device should be self-sustainable,
reusable, portable, durable and have a long
shelf-life.
• The device should cost less that
approximately $10 when manufactured in
bulk, and should be easy to assemble with
the use of pictorial instructions.
• Minimally trained operators should able Figure 1: Solar cell included
to use the device with the aid of pictorial
in final design
instructions.
Device Theory
Figure 5: Electronic schematic of the circuit controlling
pressure transducer and LED outputs
Figure 4: Device circuit realized on breadboard
Figures 7 and 8: Sensor output recorded with blood pressure cuff inflated. Gentle
tapping on the cuff band simulated oscillations that occur in blood pressure in the
physiological range.
Safety Considerations
• Pictorial manual with minimal writing
• Allows use by operators of all education levels; warnings highlight risks such as overinflation or entanglement
• Casing houses all electronic components other than face of solar cells to prevent
accidental wire contact
• Maximum current capable from solar cells is only 18mA
Prototype
Table 1: Budget for the manufacture of a single
device
Description
Pressure Transducer
Solar Cells
Other Circuit Components
Housing and Other Supplies
Total
Figure 2: Pressure response over the regime of physiological use; our device will
identify systolic and diastolic with LED outputs
Figure 6: The completed prototype on breadboard.
Cost
$2.00
$6.00
$1.45
$1.82
$11.27
Conclusions
• Additional testing and calibration must be performed.
• Using simple circuit design powered by solar cells, we have
created a rugged, cheap device that can be used in locations
lacking a centralized power grid.
• Through simplistic design and inclusion of pictorial instructions, the
device can be readily used by anyone, not solely trained medical
personnel.
• Future work entails experimentally ascertaining blood pressure
oscillation amplitudes in the arm. This will allow for proper circuit
filtering to more accurately determine systolic pressure.
Acknowledgements
Dr. Franz Baudenbacher – VU Biomedical Engineering
Dr. Paul King – VU Biomedical Engineering
John Dunbar – VU Biomedical Engineering
We would like the thank the Biomedical Engineering Department at
Vanderbilt University for funding our project.