1. 전북대학교 의학전문대학원 흉부외과학교실 최종범
심폐기의 발달과 구성
전북대학교 의학전문대학원 흉부외과학교실
최종범

2. Heart-Lung Machine Machine for cardiopulmonary bypass In the past
For open cardiac surgery
For supporting cardiac function, pulmonary function, or cardiopulmonary function
In the past
One unit
Recently
Separate units
Pump system (Heart)
Oxygenator (Lung)

3. History
First open cardiotomy (Apr 5, 1951)
Temporary mechanical takeover of both heart and lung function
Not survive due to unexpected complex congenital defect
4-yr experimentation of dogs followed
First successful OHS (Sep 2, 1952)
Dr. F John Lewis
ASD closure using general hypothermia and inflow occlusion
First successful OHS using CPB (by John Gibbon May 6, 1953)
ASD closure
High mortality rate
VSD closure by azygos flow concept (controlled cross-circulation) (Dr Walton Lillehei Mar 26, 1954)
University of Minesta hospital; Thomas Jefferson University hospital in Philadelphia; 18-yr-old woman; Oxford univesity, physics, architec;

4. DeWall-Lillehei helix bubble oxygenator (May 1955)
Beginning in a large series of patients
Method of choice worldwide for OHS
Rotating Disk oxygenator
Developed by Drs Fredrick Cross and Earl Kay
Used for early OHS in USA
Membrane oxygenator
Developed in 1950s-1970s; but clinically not frequently used
In the mid-1980s, microporous designs; frequently used.
Hemodilution
Major technologic advance in CPB
University of Minesta hospital; Thomas Jefferson University hospital in Philadelphia; 18-yr-old woman; Oxford univesity, physics, architec;

5. Cardiopulmonary Bypass
Goals
Still, bloodless heart for cardiac surgery
Replacement of cardiac and pulmonary function

6. Functions of CPB Respiration Temperature regulation (hypothermia)
Ventilation
Oxygenation
Circulation
Venous drainage (by gravity, centrifugal pump, or negative pressure)
Arterial inflow
Temperature regulation (hypothermia)
Low blood flow -> decreased blood trauma
Decreased body metabolism

7. Components of CPB Total CPB Partial CPB
Integral Components of Extracorporeal Circuit
Pumps
Oxygenator
Heat exchanger
Arterial filter
Cardioplegic delivery system
Cannulae (aortic; arterial; vena caval)
Suction and vent

8. Basic CPB circuit with oxygenator and centrifugal pump

9. Typical CPB Circuit

10. Pumps Two principle types Displacement pumps Rotatory pumps
Roller pump
Non occlusive roller pumps
Rotatory pumps
Radial (centrifugal) pumps
Axial pumps (Archimedes’ screw)
Diagonal pumps

11. Roller Pumps Most commonly used Volume Displacement
Non pulsatile blood flow
Used for
Forward flow
Cardioplegic delivery
LV vent suction

12. Roller Pumps Flow determined
Tubing diameter, roller RPM, length of tubing in contact with rollers
Proper set occlusion for minimal hemolysis
100% occlusion in cardioplegia and vent pumps
Full occlusion -> hemolysis
Larger tubing and lesser rotations cause minimal hemolysis.
High RPM and fully occlusive setting -> hemolysis
Tubing spallation cause microemboli
Easily pump air
Resistance = resistance of tubing + oxygenator + heat exchanger + filter + aortic cannula + SVR
Line pressure depends on SVR and pump flow rate
Pressure limit = mmHg ( >250 mmHg seldom accepted)

13. Nonocclusive Roller Pumps
Flat compliant tubing placed over the rollers
Positive pressure at the inlet to fill the tubing
Unlikely microair emboli
Require use of an in-line flowmeter

14. Radial (Centrifugal) Pumps
Impeller spinning within a rigid housing
Creates regions of lower and higher pressure
Blood moved from inlet to outlet
No spallation with rigid housing
Very dependent on afterload
Nonocclusive
Permit back-bleeding
Require occlusive device
Reqiure use of in-line flow meter

15. Axial / Diagonal Pumps Axial pumps Diagonal pumps
Low internal volume, high-velocity axial impeller
Currently best suited for ventricular assist application
Diagonal pumps
Very similar to centrifugal pump in design and application

16. Differences of Rotatory Pumps

17. Alternate Classification of Pumps
Roller pumps
Impeller pumps (Impeller >)
Centrifugal pumps (Cone >)

18. Centrifugal pumps > Roller pumps
Long-term CPB
In high-risk angioplasty patients
Ventricular assistance
Neonatal ECMO
Centrifugal pumps
Biomedicus Biopump (Medtronic Inc)
Sarns/3M centrifugal pump (Terumo)
Levitronix CentriMag blood pump
LVAD, RVAD, Bi VAD
BiVAD + oxygenator in RVAD = ECMO

19. Pulsatile Perfusion Significant physiologic advantages Problem
Diastolic run-off
Stimulation of the endothelium
Problem
Noncompliant high resistance CPB circuit
High flow with resultant shear stress
Hemolysis
Possible with roller pump and diagonal pump, but not with centrifugal pump
Requires larger bore arterial cannulas
Alternative method for generating pulsatile flow in high-risk patients
Use of IABP during CPB
Additional cost and invasiveness

20. Oxygenator Limited reserve for gas transfer vs. natural lung
Much smaller surface
Limited by diffusion
Types of oxygenator
Disk oxygenator
Bubble oxygenator
Membrane oxygenator
Maximum oxygen transfer
Less than 25% that of normal lung
Proportional to partial pressure difference and surface area, inversely to diffusion distance

21. Disk or bubble oxygenator
Direct contact oxygenators
Bubbles in direct contact with blood
Increasing cellular trauma

22. Bubble oxygenator Bubble oxygenator
Larger bubbles improve removal of CO2
Smaller bubbles are very efficient at oxygenation but poor in CO2 removal
Larger the No. of bubbles, Greater the efficiency of the oxygenator

26. Deforming Chamber of Bubble Oxygenator
Deforming the frothy blood
Large surface area coated with silicone
Increased surface tension of bubbles -> causing them to burst

27. Bubble Oxygenator Advantage Disadvantages Easy to assemble
Relatively small priming volume
Deforming the frothy blood
Low cost
Disadvantages
Micro emboli
Blood cell trauma
Destruction of plasma protein
Excessive removal of CO2
Deforming capacity exhausted

28. Membrane Oxygenator Charateristics Two types
Gas exchange across a thin membrane
No need in direct contact with blood and no need for deformer; so more physiologic
Minimal blood damage
Two types
Solid type (Silicone)
Microporous type (polypropylene)
um pores
Most popular design = hollow fibers ( um)

29. Membrane Oxygenator
Microporous / Hollow fibers

30. Microporous (Polypropylene) Membrane Oxygenator
Currently predominant design used for CPB
Micropores
Less than 1.0 um in diameter
Initially porous, but plasma protein coating the membrane-gas interface
Surface tension of blood prevent gas leakage into the blood phase
Conduit for O2 and CO2 exchange
Problems
Plasma leakage and membrane wet at use of period > 24 hours

31. Silicone Membrane Oxygenator
True membrane oxygenator
Silicone polymer
Improved biocompatibility -> long-term support
The 1980s-the mid-1990s
Still the membrane of choice for long-term procedures
ECLS/ECMO
Problems
Gas exchnage inferior to that of polypropylene (microporous) oxygenator
Need greater surface area and larger prime volume
Difficult in manufacturing and quality control

32. New Generation Membrane Oxygenator
Silicone polymer
A continuous sheet of silicone membrane rolled into a coil
Manufactured by Medtronic Cardiopulmonary Inc.
Membrane surface area M2
Most common use for ECLS/ECMO

33. Heat Exchanger
Intergrated into oxygenator for warming and cooling of the blood stream
Exchange surface made of
Stainless steel, aluminium, or polypropylene
Counter-current mechanism
Temperature difference between waterside and blood side
Historic reports : maximum difference of 10 °C
Recent recommendation : 6 °C and longer rewarming times
To improve neurocognitive outcome
Hyperthermic circulatory temperature
Blood damage (protein denaturation
Limit absolute maximum temperature (42 °C) in blood

34. Circuits Venous drainage by gravity into oxygenator
Height difference between venae cavae and oxygenator > cm
Mechanical suction Not desirable
Entrain air
Suck the vena cava walls against the cannula orifices
Arterial blood return to the systemic circulation under pressure

35. Size of cannula Adult Children SVC (1/3 of total flow) 28 24
IVC (2/3 of total flow)
Example: 1.8 m2 patient
Total flow 5.4 l/min
SVC 1.8 l/min, IVC 3.6 l/min
SVC > 30 Fr, IVC > 34 Fr : Single cannula > 38 Fr
36-51 Fr cannula required.

36. Arterial Return Ascending aorta just proximal to inniminate artery
Femoral artery access in
Dissecting aortic aneurysm (0.2-3%)
Reoperation
Emergency
Problems of femoral cannulation (more than ascending aorta cannulation)
Sepsis
Formation of false aneurysm
Development of lymphatic fistula
Arterial cannula
The narrowest part of CPB circuit
Should be as short as possible
As large as the diameter of vessel permits
< 100 mmHg in full CBP flow

37. Arterial Cannula Long or diffuse-tipped cannula
Minimize risk of dislodgement of atheroma in the ascending or transverse aorta
Axillary –subclavian artery, innimonate artery, LV apex
In special circumstances
Limitations and more complications
Dissection of aorta
All sites of arterial cannulation
Prompt recognition and surgical correction
TEE helpful for diagnosis

38. Other circuits Tubing sizes and lengths and connectors
Should minmize blood velocity and priming volume
Search for better biomaterials
Cardiotomy suction
Major source of microemboli and activated blood (humeral and cellular)
Minimize amount, substition by cell salvage
Cell processed blood may pose hazards
Hemoconcentrator
During and after CPB
Removal of plasma and raising of Hct
More cost effective than cell salvage and washing devices

39. Prime Fluid Risk of hemodilution Ideally close to ECF
Whole blood not used
Homologous blood syndrome
Postperfusion bleeding diathesis
Incompatibility reaction
Demand on blood banks
Advantages of hemodilution
Lower blood viscosity
Improve microcirculation
Counteract the increased viscosity by hypothermia
Risk of hemodilution
Decreased viscosity : SVR decreased
Low oncotic pressure
O2 carrying
Coagulation factor

40. Composition of Prime Average 1,500-2,000ml Hct 20- 25% Example
Balanced salt sol. RL ml
Osmotically active agent (Mannitol, Dextran 40, Hexastarch)
100 ml
NaHCO ml
KCL ml
Heparin ml

41. CPB for cardiac surgery
ECMO for ECLS
ECMO for supporting cardio/pulmonary function
VAD for supporting cardiac function
RVAD; LVAD; Bi VAD
BiVAD + oxygenator in RVAD = ECMO