Flow and Volume of Blood
Dept. of Biomedical Engineering
2003200449
YOUNHO HONG
Contents
 Cardiac Output - Fick
- Indicator Dilution
- Thermo Dilution
 Electromagnetic flow meter
 Ultrasound flow meter - Transit time
- Continuous Doppla
- Pulsed Doppla
- Thermal Convection
 Plethysmography
Indicator Dilution and Fick Method
# Indicator Dilution
Fi
Ci
F : flow
C : concentration
The unit of blood flow : l/min or ml/s
Fo
Co
dm
(infusion rate)
dt
Mass Balance Equation
The quantity of in and out is the same,
and there is no leakage.
dm
Ci  F 
 Co  F
dt
# Fick
dm
F  dt
C o  Ci
dm
: O2 consumption, L/min ( measured by spirometer)
dt
Co = Ca : concentration in artery
Ci = Cv : concentration in vein
dm
F  dt
C o  Ci
Indicator Dilution ( Dye dilution Method)
c(t)
indicator dilution curve
recirculation
bolus
injection
Extrapolation
dm
 C (t ),
dv
T
dm  C (t )  dv ,
dm  C (t )  F  dt
T

0
t
T
dm  F  C (t )  dt  m
0
Use Cardio green or
Indocyannine green for a dye.
dm
dv
 C (t )   C (t )  F
dt
dt
F
m

T
0
C (t )  dt
Thermo-dilution
c(t)
T
Use cold saline(4˚C)
bolus
injection
t
F
Q
t1
b cb  Tb (t )dt
[m3 / s]
0
Q  Vi Ti i ci  heat contentof injectate,[J]
 b  blood density,[kg/m3 ]
cb  specificheat of blood,[J/kg K]
Ultra Sound
Primary echo is bigger than
secondary echo.
t
ultra-sound generator
skin
Transit time flowmeter
velocity of ultra sound
μ
c
D
θ
(1) down-stream
td 
velocity of RBC, WBC
and platelit
D
c   cos
(2) up-stream
D
tu 
c   cos
D
D

c   cos c   cos
2 D cos
2 D cos
 2

2
2
c   cos 
c2
t  tu  t d 
(c 2   2 cos2  )
Doppler flowmeter
(1) Continuous Doppler flowmeter
(cf) Radar system
fo, c
f+fd, c
object
u
c  3 108 m / s
fd u

fo c
(2) Pulsed Doppler flowmeter
u1
f
u2
u2
u1
u3
T
fd1 fd3 fd1
fd2 fd2
t
x
Thermal convection flowmeter
Thermister
F
T2
Invasive, probe positioning is difficult.
The stronger F gets, The sharper the temperature of T2
is decreased.
(1) Bios current => Thermister heating
(2) T2 Thermister is cooled by thermal convection.
(cf.) respiratory monitoring by thermister
Temp. of inspiration is 25˚C.
Temp. of expiration is 36.5˚C.
Plethysmography
leg
open artery
close vein
cuff
Z(V)
i
V
toes
normal
slope
= flow(in artery)
slope
= flow(in vein)
cuff
dv
 f ( flow)
dt
cuff
off
Venous
Thrombosis
t
Respiratory System
# Architecture
Tracher
velocity
uT A T
Q  uT  AT  u A  AA
air flow
Bronchas
[l/min or ml/s]
cross-sectional area
The total of volume flow is not changed.
…
Alveoli
uA
AA
# Physiological functions
- O2 transport into blood stream
- CO2 removal from blood stream
- Homeostasis of PH, PO2, PCO2
AT
u A  uT
 uT
AA
velocity of the air
at alveoli is almost zero.
# Respiration
- Ventilatory mechanics
=> RC equivalent circuit model
- Gas transport
=> Mass balance equation
(Diffusion process)
Pressure measurement
(1) Differential pressure transducer
diaphragm
P1
P2
diaphragm
strain gage
(2) Balloon Sensor
Vi
hole
P
gas
ballon
0V : switch on => P>Pi
5V : switch off => P<Pi
metal switch +5V
pressure
sensor
P
Pi
air
pump
MP
control
pressure
(Pi)
Flow measurement
(1)
(2)
(3)
(4)
Rotating vane
Ultrasound flowmeter
Thermal convection
Pneumotachometer
# Pneumotachometer
P1
P1  P2  R  Q
P2
measurement
Q
(flow)
mouth
mesh screen
resistance
P1  P2
Q
(Calibratio n)
R
Volume measurement
(1) Water spirometer
single turn potentimeter
vital capacity
air
TLC
pen
IC
water
FRV
Vc
TV
ERC
Rv
CO2
absorber
mouth
(2) Dry spirometer
mouth
expiratory
gas (empty)
inspiration
gas
valve
pistol
change the position of
the pistol during breathing.
FRC measurnment
(1) He Dilution technique
- Patient at FRC
- Prepare a spirometer of volume Vsp and imitial He
Concentration of FIHe
- Patient breaths Fb the spirometer
- Find He concentration of expiratory gas FIHe
Vsp  FI He  (Vsp  FRC)  FI He
FRC 
FI He  FFHe
FFHe
 Vsp
FRC measurnment
(1) N2 washout technique
- Patient at FRC
- Prepare a spirometer with O2, Vsp
- Patient breaths to the spirometer
- Measure N2 concentration in the expiratory gas
0.8  FRC  (FRC  Vsp )  FFN2
Gas concentration measurement
(1) Mass spectroscophy
(2) Gas chromatography
(3) Infrared spectroscophy
(4) Ramen spectroscophy
(5) Emission spectroscophy
(6) Paramagnetic O2 analyzer
Gas transport measurement
(1) Gas distribution test
=> single breath N2 washout
- RC => TLC O2 inspiration
- pause (hold breath)
- Expiration and measure FN2
(2) Diffusion test
=> CO diffusion capacity
- Inspire CO, He in the air to TLC from RC
- Hold breath for 10sec
- Expire to measure FFCO and FFHE
DCO
FI CO FFHe
60U A

ln[

]
t ( PB  47) FFCO FI He
Thank You.