A novel model for blood impedance for indirect viscosity measurement

A novel model for blood impedance for indirect viscosity

measurement

Zu-yao Chang, Gerard C.M. Meijer and Gheorghe A.M. Pop

Faculty of Electrical Engineering, Mathematics and Computer Science,

Soz 2004.

Structure

• Introduction• Contents of Blood• Measurement techniques• Measurement setup• Experimental results• Conventional Model• Novel Model• Conclusions

Soz 2004.

Introduction

• Heart and arterial diseases death cause no 1.

296,900

234,600

0

100,000

200,000

300,000

400,000

Heart & arterialdiseases

Cancer

Number of deaths in The Netherlands in the year 2001

Source: Centraal Bureau voor de Statistiek

Introduction• Higher viscosity higher risk of blood-clot forming• Good correlation between blood viscosity and blood impedance.

Circadian rhythm

10

15

20

25

30

35

40

45

50

55

60

8.00 AM 12.00 AM 16.00 PM 20.00 PM 24.00 PM 4.00 AM 8.00 AM

Time

He

amat

ocr

it H

t (%

) &

Vis

cosi

ty

(m

Pa.

s)

80

100

120

140

160

180

200

220

240

260

Sp

eci

fic

Re

sist

ance

(Oh

m.c

m)

Ht

T=37°C

shear rate=0.87s-1

Soz 2004.

Introduction

HT=48%T=37ºC

0

2

4

6

8

10

12

14

0 20 40 60 80 100

Shear rate (s-1)

Vis

cosi

ty (

mP

a.s

)

135

140

145

150

155

160

165

170

Sp

eci

fic

resi

sta

nce

(O

hm

.cm

)

Viscosity (mPa.s)

Specif ic resistance (Ohm.cm)

Soz 2004.

Contents of Blood

• Plasma (volume 55%)• Blood Cells (volume

45%)– Leukocytes

(white blood cells)

– Thrombocytes

(platelets)

– Erythrocytes

(red blood cells)

Soz 2004.

1_4VZ =I

2 3

M e a s u rin g C e ll

I

V

A Cs o u rce

rin g e le ctro de s 1 4

• Two-electrode measurement technique

Measurement technique

• Four-electrode measurement technique

2_3Z

R ct W arburgV co n tact p o ten t ial

Z l iq , 1 _ 4

elec trode 4elec trode 1Cd l

R ct W arburgV co n tact p o ten t ial

Z l iq , 1 _ 2

elec trode 4elec trode 1Cd l

Z l iq , 2 _ 3 Z l iq , 3 _ 4

elec trode 2 elec trode 3

Soz 2004.

Zpol

Measurement setup(4-electrodes)

Z.Chang, 2003.

LabVIEW

Labview|Z|,

Gain G,Phase

Mathematical calculations

HP4192A

Gain Phase analyzer

measurementcircuit

measurement cell

1 2 3 4Ele ct ro de s

Measurement cell

Measurement circuit

Vosc

Impedance of Blood

Experimental resultsNyquist Plot

0

100

200

300

400

500

200 300 400 500 600 700 800 900 1000 1100 1200

Re(Z) in Ohm

-Im(Z

) in

Ohm

2-electrodes measurement

4-electrodes measurement (scaled)

12.6MHz

1.0 MHz

100 MHz

20 kHz

100 Hz

1.5MHz500 kHz

Ht=45%T=24C

Soz 2004.

PolarizationeffectsBloodDielectric

Properties ofwater

Conventional Model

• Resistor Rp: plasma resistance with non-conducting blood cells.

• Capacitor Cm: cell-membrane capacitance.

• Resistor Ri: interior cell-resistance.

Rp

Ri Cm

Where is the dielectric capacitance of water ?

Soz 2004.

Conventional Model

0

10

20

30

40

50

60 70 80 90 100 110 120 130 140 150 160

Re(Z) in Ohm

-Im

(Z)

in O

hm

12.6MHz

800kHz1.2MHz

100kHz

100Hz

Blood, Ht=45%, T=24ºC

Nyquist plot of four-electrodes measurement

conv. model<1.2 MHz

conventional modelfull freq. range

Soz 2004.

Conventional Model

Soz 2004.

0

100

200

300

400

500

200 300 400 500 600 700 800 900 1000 1100 1200

Re(Z) in Ohm

-Im

(Z)

in O

hm

100MHz800kHz1.2MHz

100Hz

20kHz

Nyquist plot of two-electrodes measurement

Blood, Ht=45%, T=24ºC

Cliq

Improved model total freq. fit

Novel Model• Resistor Rp: plasma

resistance with non-conducting blood cells.

• Resistor Ri: interior cell-resistance.

Rp

Ri

Soz 2004.

• Constant-Phase element CCPE_m: cell-membrane capacitance. CCPE_m

CPE

1

( j )nZ

C

Cliq

• Capacitor Cliq: dielectric capacitance.

Novel Model

0

10

20

30

40

50

60 70 80 90 100 110 120 130 140 150 160

Re(Z) in Ohm

-Im

(Z)

in O

hm

12.6MHz

100Hz

Blood, Ht=45%, T=24ºC

Nyquist plot of four-electrodes measurement

Soz 2004.

Conv. model, 3pnt Conventional model, all

novel model

Novel Model

0

100

200

300

400

500

200 300 400 500 600 700 800 900 1000 1100 1200

Re(Z) in Ohm

-Im

(Z)

in O

hm

100MHz

100Hz

20kHz

Nyquist plot of two-electrodes measurement

Blood, Ht=45%, T=24ºC

Soz 2004.

Conventional model with Cliq

novel model

Conclusions

• It is possible to predict blood viscosity via blood impedance.

• The validity of the early model of blood impedance is limited.

• A novel model of blood impedance is found and its validity verified until 100MHz.

Soz 2004.

Questions ?

Soz 2004.