Transcript Oral Report 4

Vanderbilt Senior Design 2010:
Non-Electronic Blood Pressure Assist
Device
Members:
Mentor:
Laura Allen (ChBE)
James Berry (BME)
Casey Duckwall (BME)
David Harris (ChBE)
Prof. Baudenbacher
Blood Pressure Assist Device
• The Engineering World Health (EWH)
Organization proposed the challenge:
▫ Can a mechanical adjunct for a
sphygmomanometer be designed to amplify the
oscillatory pressure signal?
▫ Can the design be used by minimally trained
users to identify at least systolic pressure?
(Ideally diastolic too)
Developing World Usability
• Self-sustainable
▫ Power supply from solar means
• Low Cost: Less than $10
▫ When produced in quantities of 5000+
• Mechanical adjunct to sphygmomanometer
▫ Eliminating the need for Korotkoff sound
identification
• Identify at least systolic
• Pictorial instructions for all users
Rationale
• Cardiovascular diseases kill more people
worldwide than any other disease1
▫ Even a leading cause in developing nations, where
AIDS and malaria receive greater attention
• Hypertension is a primary risk factor for
cardiovascular illnesses
▫ Managing blood pressure is vital for long-term
health of cardiovascular disease patients2
▫ Diagnosing hypertension can be challenging in
developing countries
Literature Review
• Patent search did not reveal any useful
information
• Researched the science behind blood pressure
• Investigated different methods of measurement
• Identified a range for oscillation frequencies
Preliminary Data Collection
• Findings indicate that measuring blood pressure
by observation of sphygmomanometer alone is
unreliable
Association for the Advancement of Medical Instrumentation and British
Society of Hypertension Protocol [3]
Results from Commercial BP Device
• Commercially available electronic blood
pressure devices in the range of $40 yielded
extreme variations in blood pressure readings,
going so far as to place some individuals in both
stage 2 hypertension as well as hypotension.
• Furthermore, these readings were extremely
variable between measurements on the same
individual, varying by more than 20mmHg for
systolic.
Project Budget
Electronic blood pressure cuff
Standard blood pressure cuff
4 solar cells
Pressure transducer
Batteries (AAA)
Rubber tubing (8mm)
T-junction
Total
Shipping
$45
$20
$15
$40
$8
$10
$10
$148
$30
Circuit Specification
• An electronic approach yields 5 new design
elements
▫
▫
▫
▫
▫
Power Supply
Filtering
Amplification
Readout
Transducer
Circuit
Power Supply
• Reusable
▫ Solar cell - $3.00
▫ 4.5V
• Sufficient voltage output
▫ ±3V operational amplifier rails
▫ ~1.8V LED
• Charging capacitor
▫ Relatively large capacitor to charge device in
sunlight as well as smooth voltage spikes
Filtering and Amplification
• Literature suggests frequency range of 20-75Hz
• First-order active filtering using
▫ High-pass filter > 10Hz
 50μF and 320Ω
▫ Low-pass filter < 80Hz
 3.33nF and 640kΩ
• Amplify signal to ~2.5V in passed range
▫ Gain of 2000
Output
• Two red LEDs
▫ 1) Power light - Demonstrate sufficient power to
the device
▫ 2) Indicator light – Light up during pass-band
frequencies
Transducer
• Pressure Sensor: $2.00 in bulk
▫ NovaSensor NPC-100
▫ Developed for usage in biomedical diagnostics
▫ Sensitivity ±1%
 5µV/V/mmHg
▫ Linearity ±1%
 For physiological range
▫ Full range -30mmHg to 300mmHg
▫ Test operating resistance to compute peripheral
resistor values
Device Budget
• Component pricing
agrees with previously
determined budget
• Total price below $10.00
Cost
$2.00
$0.95
$0.05
$3.00
$0.15
$0.15
$0.05
$0.05
$0.05
$0.05
Budget
Quantity Description Total
1 Transducer
$2.00
1 Op Amp
$0.95
2 Red LEDs
$0.10
2 Solar Cells
$6.00
1 Hosing
$0.15
1 T-Junction
$0.15
Resistors
1
320Ω
$0.05
1
640kΩ
$0.05
Capacitors
3
1μF
$0.15
3
10nF
$0.15
Total:
$9.75
References
(1) WHO. “Fact Sheet: The Top Ten Causes of Death.” WHO.
November 2008. Accessed October 28, 2009
http://www.who.int/mediacentre/factsheets/fs310_2008.pdf
(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.
References
(3) O’Brien E, Waeber B, Parati G, Staessen J, Myers MG. Blood
pressure measuring devices: recommendations of the European
Society of Hypertension. BMJ 2001; 322(7285): 531-6.