1. 4/17/2017
414BMT Introduction to Biomedical Engineering Catheterization & Cardiac Output
Dr Ali Saad, College of Applied medical sciences/
Department of biomedical technology
King Saud University

2. Example of Catheters
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

3. Measurement of Heart Valve Surface Area
Bernoulli’s Equation:
pressure due to potential energy
pressure due to kinetic energy
Pt : total fluid pressure
P : local static fluid pressure (this is the term we want to measure)
r : 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.

4. Measurement of Heart Valve Surface Area (cont.)
orifice c.s. area = A P1 P2
pressure
sensors
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

5. 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:
(1)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

6. Measurement of Heart Valve Surface Area (cont.)
Bernoulli’s equation at location 2:
(2)
subtract (2) from (1):
or:
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

7. Measurement of Heart Valve Surface Area (cont.)
flow at orifice:
assumes velocity through orifice = velocity at location 2
orifice c.s. area:
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

8. Measurement of Heart Valve Surface Area (cont.)
If friction is taken into account:
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.

9. Phonocardiography: Measurement of Heart Sounds
100
aortic pressure
dicrotic
notch
aortic valve
opens
mm Hg
mitral valve
closes
mitral valve
opens
left ventricular
pressure R T P
ECG Q S
heart sounds
(phonocardiogram)
3rd
4th
4th
1st
2nd
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

10. Heart Sound Generation
heart sounds are due to vibrations produced by
acceleration or deceleration of blood, some theories:
first: movement of blood during V. systole, closure of AV valves, turbulence at aortic and pulmonary valves.
second: deceleration and flow reversal of blood in aorta and pulmonary artery; closure of semilunar valves.
third: termination of rapid filling of ventricles from atria.
fourth: due to propulsion of blood into ventricles during atrial contraction.
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.

11. Heart Sound Measurement
Stethoscope: Transmit sounds from the chest wall to ears.
frequency response: many resonances: 10 1
0.1
log f 40
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.

12. Heart Sound Measurement (cont.)
Dynamic microphone: + Vo
diaphragm _
frequency response: Hz
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

13. Heart Sound Measurement (cont.)
crystal microphone
piezoelectric crystal + _
chest
frequency response: Hz
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

14. Measurement of Blood Flow
Indicator Dilution Methods: cardiac output
Fick Method
Rapid Injection Methods
Dye Dilution
Thermodilution
Electromagnetic Flowprobes
Ultrasound Flowprobes
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

15. Indicator Dilution Methods
indicators:
oxygen
dye
heat
consider a given volume of water: V,
add to it a given mass of indicator: m
resulting change in indicator concentration:
or:
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

16. Indicator Dilution Methods (cont.)
Now suppose the volume of water is time-varying: V(t)
In order to maintain the same DC, must make m time varying as well:
or:
take time derivative: or
F = Flow = dV/dt
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

17. Fick Method Indicator is O2 gas 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.

18. Fick Method (cont.) O2 O2 is supplied continuously nose plug gas
flowmeter
soda-lime
container O2
nose
plug
O2 is supplied continuously
sample venous blood: Cv
(Cv in peripheral veins
varies widely) PA
(absorbs excess CO2)
sample
arterial blood: Ca
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

19. Indicator Dilution via Rapid Injection
In indicator dilution, one continuously adds indicator to an expanding volume of water in order to maintain a constant DC:
If the ratio is not constant, we get:
(1)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

20. Rapid Injection
This is the case in the rapid injection method, a quantity of indicator is added over a short period of time. Equation (1) becomes:
take derivative:
(2)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

21. Rapid Injection (cont.)
Assume that:
(2) becomes:
or:
(3)
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

22. Rapid Injection (cont.)
Now integrate both sides of (3):
where we assumed F is constant. Solving for flow:
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

23. Typical DC(t) Curve t t1 t1 typically around 30 s due to recirculationt1
t1 typically around 30 s
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

24. Indicators Non-Toxic Dye:
indocyanine green: injected in pulmonary artery, DC(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.

25. Thermodilution inject 4 ml of cold saline F = flow (m3/sec)
Q = heat in injectate in Joules
rb = density of blood (kg/m3) (can be determined from hematocrit)
cb = specific heat of blood (J/kgoK) (can be determined from hematocrit)
DTb(t) = Tb - Tbaseline (oK)
ri = 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.

26. Swan Ganz Catheter t Tbaseline t1 t1 typically around 30 s pulmonary
cold
saline injected
from syringe
pulmonary
artery
R. Atrium
thermistor Tb
thermistor Ti
balloon
due to recirculation
exponential fit
Tbaseline t t1
t1 typically around 30 s
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

27. Density and Specific Heat of Blood
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

28. Example of Swan Ganz Catheter
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.

29. 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.

30. Examples of Cardiac Output Computers
World Medical
Columbus
BMT 414, Dr. Ali Saad, modified from Dr. Carlos Davila southes. meth. univ.