Transcript Catheterization-cardiac outputSa_ch5

414BMT
Introduction to Biomedical Engineering
Catheterization & Cardiac Output
Dr Ali Saad, College of Applied medical sciences/
Department of biomedical technology
King Saud University
Example of Catheters
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
2
Measurement of Heart Valve Surface Area
Bernoulli’s Equation:
pressure due to kinetic energy
pressure due to potential energy
Pt  P  gh 
u2
2
Pt : total fluid pressure
P : local static fluid pressure (this is the term we want to measure)
 : fluid density
g : acceleration of gravity
h : height of fluid w.r.t. a given reference
u: fluid velocity
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
3
Measurement of Heart Valve Surface Area (cont.)
heart valve
orifice c.s. area = A
P1
P2
pressure
sensors
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
4
Measurement of Heart Valve Surface Area (cont.)
Assumptions:
•frictionless flow
•difference in heights at 2 sensor locations is zero (h1 = h2)
•velocity at location 1 is small compared to location 2
velocity (u1 << u2)
Bernoulli’s equation at location 1:
P1t  P1  gh1 
u12
2
(1)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
5
Measurement of Heart Valve Surface Area (cont.)
Bernoulli’s equation at location 2:
P2 t  P2  gh2 
u22
2
(2)
subtract (2) from (1):
P1  P2 
u22
2
or:
 2 P1  P2 
u2  




1/ 2
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
6
Measurement of Heart Valve Surface Area (cont.)
flow at orifice:
F  Au2
assumes velocity through orifice = velocity at location 2
orifice c.s. area:


F

A
 F

u2
 2 P1  P2 
1/ 2
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
7
Measurement of Heart Valve Surface Area (cont.)
If friction is taken into account:

F

A 

cd  2 P1  P2 
1/ 2
cd : discharge coefficient
semilunar valve: cd = 0.85
mitral valve: cd = 0.6
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
8
Phonocardiography: Measurement of Heart Sounds
100
aortic pressure
mm Hg
dicrotic
notch
aortic valve
opens
mitral valve
closes
mitral valve
opens
left ventricular
pressure
R
0
T
P
ECG
Q
S
heart sounds
4th
3rd
1st
2nd
4th
(phonocardiogram)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
9
Heart Sound Generation
heart sounds are due to vibrations produced by
acceleration or deceleration of blood, some theories:
n first: movement of blood during V. systole, closure of AV
valves, turbulence at aortic and pulmonary valves.
n second: deceleration and flow reversal of blood in aorta
and pulmonary artery; closure of semilunar valves.
n third: termination of rapid filling of ventricles from atria.
n fourth: due to propulsion of blood into ventricles during
atrial contraction.
n heart murmurs: due to turbulence resulting from heart
valve stenosis (impeded flow through valve) or
regurgitation (backflow through valve after valve closure).
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
10
Heart Sound Measurement
n
Stethoscope: Transmit sounds from the chest wall to ears.
n frequency response: many resonances:
10
1
0.1
40
log f
1000
firmly applied chest piece attenuates low frequencies;
skin serves as diaphragm, becomes taught.
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
11
Heart Sound Measurement (cont.)
n
Dynamic microphone:

B
diaphragm
+
Vo
_
frequency response: 20-2000 Hz
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
12
Heart Sound Measurement (cont.)
n
crystal microphone
piezoelectric crystal
chest
+
_
frequency response: 0.1 - 1000 Hz
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
13
Measurement of Blood Flow
n
n
n
Indicator Dilution Methods: cardiac output
n Fick Method
n Rapid Injection Methods
n Dye Dilution
n Thermodilution
Electromagnetic Flowprobes
Ultrasound Flowprobes
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
14
Indicator Dilution Methods
indicators: •oxygen
•dye
•heat
consider a given volume of water: V,
add to it a given mass of indicator: m
m
C

resulting change in indicator concentration:
V
or:
m  C V
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
15
Indicator Dilution Methods (cont.)
n
n
Now suppose the volume of water is time-varying: V(t)
In order to maintain the same C, must make m time
varying as well:
mt 
C 
V t 
n
n
m(t )  C V (t )
or:
take time derivative: dm / dt  C  dV / dt
or
F
dm / dt
C
F = Flow = dV/dt
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
16
Fick Method
Indicator is O2 gas
dm / dt
F
Ca  Cv
F = blood flow (l/min)
dm/dt = O2 consumption (l/min)
Ca = arterial O2 concentration (lO2/lblood)
Cv = venous O2 concentration (lO2/lblood)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
17
Fick Method (cont.)
O2
nose
plug
O2 is supplied continuously
gas
flowmeter
sample venous blood: Cv
dm / dt
soda-lime
container
PA
(Cv in peripheral veins
varies widely)
(absorbs excess CO2)
sample
arterial blood: Ca
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
18
Indicator Dilution via Rapid Injection
n
In indicator dilution, one continuously adds indicator to an
expanding volume of water in order to maintain a constant
C:
mt 
C 
V t 
n
If the ratio is not constant, we get:
mt 
Ct  
V t 
(1)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
19
Rapid Injection
n
This is the case in the rapid injection method, a quantity of
indicator is added over a short period of time. Equation (1)
becomes:
Ct V t   mt 
n
take derivative:
dV dC
dm
Ct 

V (t ) 
dt
dt
dt
(2)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
20
Rapid Injection (cont.)
Assume that:
Ct 
dV
dC

V (t )
dt
dt
(2) becomes:
Ct 
dV dm

dt
dt
or:
dm
Ct  F 
dt
(3)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
21
Rapid Injection (cont.)
Now integrate both sides of (3):

F Ct dt  m
where we assumed F is constant. Solving for flow:
F
m
 Ct dt
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
22
Typical C(t) Curve
F t
1
0
m
Ct dt
C(t )
due to recirculation
t
t1
0
t1 typically around 30 s
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
23
Indicators
n
n
Non-Toxic Dye:
n indocyanine green: injected in pulmonary artery, C(t)
measured from blood drawn from catheter placed in
femoral or brachial artery (leg).
Heat: used in thermodilution
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
24
Thermodilution
inject 4 ml of cold saline
Q
F
b cb
t1
0 Tb t dt
F = flow (m3/sec)
Q = heat in injectate in Joules Q  vi Ti i ci 
b = density of blood (kg/m3) (can be determined from hematocrit)
cb = specific heat of blood (J/kgoK) (can be determined from hematocrit)
Tb(t) = Tb - Tbaseline (oK)
i = density of injectate (kg/m3) (known)
ci= specific heat of injectate (J/kgoK) (known)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
25
Swan Ganz Catheter
cold
saline injected
from syringe
pulmonary
artery
R. Atrium
thermistor
Tb
thermistor
Ti
Tb
balloon
due to recirculation
exponential fit
t
Tbaseline
0
t1 typically around 30 s
t1
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
26
Density and Specific Heat of Blood
Hematocrit (Ht)
cb
b
35
0.88
1.053
40
0.87
1.058
45
0.865
1.061
50
0.86
1.064
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
27
Example of Swan Ganz Catheter
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
28
Example of Swan Ganz Catheter (cont.)
A. Rounded, Tapered Tip
B. Deflated Profile Flush with Catheter
C. Polyurethane or Latex Balloon Option
D. Polyurethane Catheter Material
E. Large High-Flow Port Holes
F. Vivid Depth Insertion Marks
G. Triple Seal Extension Divided Junction (DJ)
H. Transparent Extensions
I. Color coded, Labelled Extensions
J. Three Thread Winged, Connector Hub
K. Easy Handling Stopcock
L. Balloon Inflation/Deflation Indicator (I)
M. Mushroom Shaped Lumens for Strength and Flow
N. Rugged Computer Connector
O. Thermoset, Industry Standard Thermistor
P. Pressure Release Valve (PRV) (Available Upon Request)
Q. Contamination Sheath (CMS)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
29
Examples of Cardiac Output Computers
World Medical
Columbus
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.
30