Medical Instrumentation II
Chap 7. Blood pressure and sound
1. Blood pressure : Invasive blood pressure
Non-invasive blood pressure
2. Intraocular pressure : Tonometry
3. StethoscopeMedical Instrumentation II
1. Tonometry
Medical Instrumentation II
P
M
P
M
Contact Area = A
F = Mg(We Known
factor)
F
Ball Ball
AFP /Force per unit Area
• Measurement structure
Medical Instrumentation II
LED
PhotoSens
orEx) Photo diode & Photo Transistor
Intraocular
pressure
2. NIBP
Medical Instrumentation II
Cuff pressure
Cuff
Spuit
Stethoscope
• Heart structure
Medical Instrumentation II
Pulmonary Vein
Aorta
Pulmonary artrySuperi
or
Inferior
Venacava
Coronary vein
Coronary
artery
- Systemic circulation- Pulmonary circulation- Coronary circulation
• Blood pressure graph
Medical Instrumentation II
120mmHg
90mmHg
Systolic pressure
Diastolic pressure
NIBP measure the value of systolic & diastolic pressure. Also It isn’t the print graph
• About PCB (Printed Circuit Board)
Medical Instrumentation II
PCB is Classified MLB(Multi layer Board), Double substrate 1. Spec2. Circuit design3. CAD : schematic
(OrCAD)4. CAD : layout(OrCAD)5. PCB produce6. Components apply7. Test & programming8. Debugging
• Automatic Blood pressure graph & principle
Medical Instrumentation II
P
80mmHg
120mmHg
Blue is pressurize
Red is decompress
Cuff pressure decrease
-2 ~ -3 mmHg / sec
Cuff > inner vessel
Systolic
pressure
Diastolic
pressure
Medical Instrumentation II
• Blood pressure sound graph
NoiseHeart sound
graph
Osillometric
Method
3. Invasive BP measurement
Medical Instrumentation II
Dome Diaphragm
Strain gage
Cable
Diaphragm is flexible
Pi
Po
Blood vessel
Saline
• Catheter
Medical Instrumentation II
1. Length2. Diameter3. Material4. Air bubble in
Catheter
Catheter have several trouble!!!
Pi(t) Po(t)
t t
≠
Equivalent circuit model of catheter – sensor system Voltage, v, [V] Pressure,
P, [pa] Current, i, [A=C/s] Moving
flow, f, [m³/s] Charge, q, [C] Volume,
v, [m³]
Medical Instrumentation II
EX)
(Center of Mass )
M F = Mg
A
Air potentia
l
m f = mg
Hight ↑ Pressure ↓
Medical Instrumentation II
Dome Diaphragm
Strain gage
Cable
Pi
Po
Blood vessel
Saline
• Apply measurement
Length is applied resistor,
Capacitor and Conductor
Pi & Po is applied voltages
Blood flow is applied
Current
1. Resistance
Riv
A
L
i
vR
A
L
EX)
P1
P2
Medical Instrumentation II
Pipe represent Resistor.
As length & diameter.
R
PPkF 21
2. Capacitance of compliance
Medical Instrumentation II
dt
dvCi
dt
dPCf YC
Young’s
modulus
Pressure is increasing,
Compliance is increasing
Medical Instrumentation II
3. Inductance / Inertance
dt
diLv
dt
dfLP
2A
mL
Mass is increasing, innersure is increasing,And inductance is increasingAs a result, current flow (di/dt) is decreasing.