Transcript Oral Report 2

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

Non-electronic
 Many

Low Cost: Less than $5
 When

produced in quantities of 2000+
Mechanical adjunct to sphygmomanomter


rural clinics may be without electricity
Eliminating the need for Korotkoff sound identification
Identify at least systolic
 Pictorial
instructions for widespread 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 countires
Literature Review



Patent search did not reveal any useful information
Researched the science behind blood pressure
Investigated different methods of measurement
Preliminary Data Collection



Aim to test the accuracy of a standard
sphygmomanometer without the use of a
stethoscope
Visually observe oscillations and record blood
pressure three times
Take one “correct” measurement using stethoscope
and standard procedure
Correlation Coefficients, R
Laura vs. David vs. Casey vs. James vs. Laura vs.
Actual Actual Actual Actual David
Systolic
0.564
0.606
0.961
0.911
0.481
Diastolic
0.810
0.727
0.614
0.371
0.901
Correlation Issues
Many correlation coefficients are very low


No predictive power
Even higher correlations are for individual lines
Not y=x
 Calibration
be
 Not feasible

Laura Correlation
Systolic
Diastolic
Linear (Systolic)
140
y = 0.6362x + 42.752
R2 = 0.3178
130
would
required
Linear (Diastolic)
120
110
True

y = 1.2222x - 17.92
R2 = 0.6563
100
90
80
70
60
60
70
80
90
100
Predicted
110
120
130
140
Troubling Deviation Trends
Systolic Deviations
20
Laura
15
Deviation
David
10
Casey
James
5
Linear (Laura)
Linear (David)
0
Linear (Casey)
-5
Linear (James)
-10
100
105
110
115
120
125
130
135
140
True Systolic Pressure
Diastolic Deviations
10
Laura
Deviation
5
David
0
Casey
James
-5
Linear (Laura)
-10
Linear (David)
Linear (Casey)
-15
Linear (James)
-20
60
65
70
75
True Diastolic Pressure
80
85
90
Current Status

Research yielded few mechanical pressure transducers



No apparent combination applicable to design
Mechanical transducers are relatively expensive in terms
of our budget
Redefine the design statement


Rather than focus on “mechanical” aspect, we direct our attention
to portable, reusable electronics
Criteria provided by EWH still applicable other than electronic
aspect
New Design Criteria

An electronic approach yields 5 new design
elements
 Power
Supply
 Filtering
 Amplification
 Readout
 Transducer
Power Supply

Resuable
 Solar
cell
 Magnetic induction (shake flashlight)

Sufficient voltage output
 Operational
 Output
specs
Amplifier specs
Filtering and Amplification




Determine an appropriate range of frequencies for
blood pressure oscillations
Bandpass filter this range (ωlow to ωhigh)
Look into higher-order filters such as Butterworth,
Chebyshev, or Elliptic
Amplify signal to a range detectable by our output
Simple Output

Simple outputs may consist of simply a single 2-color
LED
Color 1: Allows user to know device is active. This color will
display during the range where there is no bp oscillations.
 Color 2: This color will light during the range of acceptable
bp oscillations.



When 1-> 2, user will note systolic bp
When 2-> 1, user will note diastolic bp
Transducer

Research into electronic transducers suitable to this
project is underway
A possible source of information is to simply reverse
engineer electronic blood pressure devices and
examine their transducer and its location

Guess indicates use of strain gauge

Validation

Electronic devices are cheap to produce
 More

likely to meet budget requirements
Design experiments and statistical analyze to
demonstrate deviation from current procedure
 If
large deviation, may be able to find better
transducer/filter
New Directions

Identify range of pass frequencies
 Design



filter
Identify applicable transducer
Research solar cells/magnetic induction techniques
Finalize display
 Identify
appropriate LEDs
References
(1)
(2)
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
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.