생체계측 ii report #9 2005200427 송성진 medical instrumentation ii

생체계측 II Report #9

2005200427 송성진

Medical Instrumentation II

<Topics Covered in Chapter 8>

• Cardiac Output Fick Technique Method Indicator Dilution Thermodilution• Electromagnetic Flowmeter (Not good)• Ultrasound Flowmeters• Plethysmography

Medical Instrumentation II

Chap 8. Part I. Flow and Volume of Blood

1. Indicator Dilution Method

• Fick Method• Indicator Dilution using

rapid injection• Thermodilution

Medical Instrumentation II

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iF oF FFF oi )(densityCi )(densityCo

dt

dm(Infusion rate) -> We Known

FCdt

dmFC oi (Mass balance

equation)

min/min// gllg

io CCdt

dmflowF )(Conclusio

n :

Fick Method

Medical Instrumentation II

dt

dm

Substitution of Equation!

ao CC

vi CC

(O₂ density of Artery Blood)

(O₂ density of Vein Blood)

(O₂ Consumption, L/min)measure By Spirometer

Indicator Dilution using rapid injection

Medical Instrumentation II

Dye Dilution MethodIndocyanine green (cardiogreen)

Extrapolation

Indictor dilution curve

)(tC

tBolus injection

Recirculation

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Find Area!

)(tCdv

dm dvtCdm )(

FtCdt

dvtCdvtC

dt

d

dt

dm )()()(

TT

dttCFdmm00

)(

T

dttC

mF

0)(

Conclusion :

Medical Instrumentation II

Weak Point : Once dye get an injection, it remains in our body.

The dye should be excreted in the urine. In order

to remeasure the blood flow, you should wait for a long time.

Thermodiltion (standard)

Medical Instrumentation II

T

tBolus injection

Weak Point : We unknown temperature of Right artium.

Using 4 lumen catheter(Swan-Ganz catheter)

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]/[)(

3

0

smdttTC

QF T

bbb

Conclusion :

][JCTVQ iiii (Heat content of injectate)

]/[ 3mkgb

]/[ KkgJCb

(Blood density)

(Specific heat of blood)

Medical Instrumentation II

-> pressure element, approvaled by 1MHz frequency.Ex)

t

No reflection

Primary Echo

skin

2. Ultra Sound

Medical Instrumentation II

2

f

v

MHzf

3

Near field

Far field

D

2.1sin

Transit Time Flowmeter

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Du

Velocity of RBC, WRC, and plate.

c Velocity of ultrasound.

Medical Instrumentation II

i ) Down stream ( = Blood flow direction)

ii ) Up stream ( = Blood flow reverse direction)

cosuc

DtD

coscos uc

D

uc

Dttt DU

cosuc

DtU

2222

cos2

cos

cos2

C

Du

uc

Du

Because… C >> ucosφ

Conclusion :

Continuous Doppler Flowmeter

Medical Instrumentation II

u

c

u

f

f

o

d

cff d

cfo

Doppler frequency shift

Ex) aviation, ship, submarine…

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Pulsed Doppler Flowmeter

D

1u2u

3u2u

1u

12321 uuuuu

Flow profile measuremen

t

Thermal Convection Flowmeter

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Thermister

f

2T

1T

i ) Bias current -> Thermister heatingii ) T₂Thermister is cooled by thermal convection

Weak Point : Invasive and Probe position is difficult.

Medical Instrumentation II

-> Volume, blood flow measurement

V

`i Howland Current

Source

Cuff

Artery openVein close

mmHg60

3. Plethysmography

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t

Z)(v

Venous Thrombosis

NormalVolume

Cuff On Cuff Out

Slope = flow

Arterial

Patient monitoring (Respiration monitoring)

Part II. Pulmonary Function Test

Medical Instrumentation II

1. ArchitectureTrachea

Bronchus

Alveoli

Area TT Au ,

AA Au ,

AATT AuAuQ

A

TTA A

Auu

TA uu Because… O₂ & CO₂ diffusion at alveoli

Medical Instrumentation II

2. Physiological Functions

• O₂ transport into blood stream• CO₂ removal from blood

stream• Homeostasis of pH, Po₂, Pco₂

Medical Instrumentation II

3. Respiration

• Ventilatory mechamis - RC equivalent circuit model

• Gas transport - Mass balance equation(Diffusion

process)

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4. Pressure measurementDifferential pressure transducer

1P 2P

Diaphragm

i )

ii )1P 2P

Diaphragm

2C1C

1x 2x

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iii )

Mesh screen

1P 2P

Differential pressure sensor

Q

Flow

Mouth

RQPP 21

R

PPQ 21 Conclusio

n :

Airpump

Medical Instrumentation II

Ballon sensorHole Ballon

Gas

Pressure sensor

Pv5

MPiv

Control

Pressure

Metal switch

Switch On ->Switch Off ->

v0v5

iPP iPP

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5. Flow measurement

• Rotating Vane• Ultrasound Flowmeter• Thermal Convection Flowmeter• Pneumotachometer (standard)

Medical Instrumentation II

6. Volume measurement-> Plethysmography

t

TLC

FRC

RV

TV (Tidal Volume)

ERC

IC VC

Weak Point : It is Relative value, not absolute value.

Medical Instrumentation II

Water Spirometer

Water

Air

Pen

Rotating Paper

Mouth

CO₂ absorber

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Dry Spirometer

Air (gas)

Mouth

Inspiratory gas

Expiratory gas

Valve

Piston

Gas is Separated by two section

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7. FRC measurementHe dilution technique - patient at FRC

- prepare a spirometer of volume VSP and

initial He, concentration of fIHE

- patient breaths tooth spirometer - find He concentration of expiration F

SPFHeFHeIHe VFFFFRC

Medical Instrumentation II

N₂ washout technique - patient at FRC - prepare a spirometer of O₂, VSP

- patient breaths to the spirometer - Measure N₂ concentration in (FFN₂)

the expiratory.

2)(8.0 FNSP FVFRCFRC

Medical Instrumentation II

8. Gas concentration measurement

• Mass spetroscophy• Gas chromatography• Infrared spectrography• Raman spectrography• Emission spectrography• Paremagnetic O₂ analyzer

Medical Instrumentation II

9. Gas transport measurement

Gas distribution test(Single breath N₂ wachout) - RC -> TLC O₂ inspiration - Pause (hold breath) - Expiration and measure fN2

Medical Instrumentation II

Diffusion test(CO diffusion capacity) - Inspire ω, He in air - fICO, fIHe

- Hold breath for 10sec - Expire to measure FFCO, FFHe

He

He

CO

CO

I

F

F

I

B

ACO f

F

F

f

Pt

vD ln

)47(

60