Transcript Simulation of Cooling Preservation Systems for Human

Multidisciplinary Analysis,
Inverse Design,
Robust Optimization
and Control Laboratory
Simulation of Fully Conjugate Cooling Preservation Systems for
Human Hearts Destined for Transplantation
Abas Abdoli1, George S. Dulikravich1, Chandrajit Bajaj2, David F. Stowe3 and M. Salik Jahania4
1Florida
International University, 2University of Texas at Austin, 3Medical College of Wisconsin and 4Wayne State University
Heart Transplantation
Heart Geometry
Thermo-Fluid Analysis
Stress Analysis
• The U.S. Organ Procurement and Transplantation Network
(OPTN)’s 2011 annual report indicated that approximately 18% of
patients died due to lack of matching hearts [1].
• OPTN also reported that ONLY in a few states ~70% of adult waitlisted patients received a heart transplant within one year.
 A 3-D high resolution human heart geometry extracted from CTangio data was used for this research [2].
 Conjugate heat transfer simulation was carried out using
OpenFOAM platform. The University of Wisconsin solution was
used as the cooling liquid. Laminar and turbulent UW flows were
simulated by using Navier–Stokes equations and k-ε turbulent
model.
 Inlet temperature was 4oC. Outlet pressure was 101 kPa. Inlet
velocities were 0.4 m/s and 1 m/s for internal circulations and 0.4
m/s for external circulation. All cooling container’s walls were
assumed to be thermally insulated.
 The average volumetric temperature was reduced to +5.0°C after
25 min. The maximum temperature was 12.0°C at 25 min.
• Stress analysis with small deformation has been performed to
obtain the stress field due to pressure and temperature fields.
OpenFOAM has been used as the platform for simulations.
• That maximum value of Wall Shear Stress was 9.2Pa and occurred
at tips of the pulmonary valve [3].
a)
b)
Outermost
surfaces
Innermost
surfaces
Figure 1. Percent of adult wait-listed patients in 2010 who received a deceased
donor heart transplant within one year [1].
• OPTN prioritizes organ allocation to the most critically ill-heart
matching candidates.
• To facilitate transplant coordination and to minimize ischemic time,
five concentric geographic zones were defined by OPTN for the
heart allocation.
• In most cases, the donor and the recipient of the compatible heart
are at vastly different geographic locations thus preventing
transplantation.
• An optimal preservation protocol is key to extending the current
preservation time, thereby expanding the transplant geographical
zones and increasing the number of heart transplants to the most
critically ill-heart matching recipients.
Heart Preservation and Research Objectives
• Cold (hypothermic) preservation is the most common preservation
method. It is less complicated, less expensive compared to other
methods.
• The idea behind this method is to decrease cell metabolism, thus
decrease oxygen and glucose consumption, and carbon dioxide
production.
Optimal cooling preservation should:
• Cool the heart as fast and as uniformly as possible.
• Prevent tissue damages due to thermal and hydraulic stress during
the cooling process.
• Prevent damages due to ice crystals formation by avoiding
temperatures lower than the freezing temperature of water (+4oC).
Research Objectives
• Design a cooling container including required inlets/outlets and
connections for coolant circulations.
• Cool the heart as fast and as uniformly as possible.
• Prevent tissue damages due to thermal and hydraulic stress during
the cooling process.
• Prevent damages due to ice crystals formation by avoiding
temperatures lower than the freezing temperature of water (+4oC).
TEMPLATE DESIGN © 2008
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Figure 2. Heart model: a) whole heart and b) innermost contact and
outermost surfaces.
a)
a)
b)
 Separate surfaces to define different computational domains and
apply different boundary conditions.
a)
b)
c)
b)
Figure 7. WSS magnitude: a) entire fluid contact surfaces, and b) cut-away
enlarged view of higher shear stresses region.
Conclusion
d)
c)
• A cooling container for human heart preservation was designed. In
this protocol external and internal cooling took place by pumping
the UW solution inside and outside of the heart.
• Different cooling scenarios were simulated in which laminar flow,
turbulent flow and unsteady periodic inlet velocities were applied.
• Results showed that the cooling case with laminar flow pattern,
inside and outside of the heart had the best performance in terms of
cooling the heart as fast as possible and at the same time
preventing tissue damages due to thermal and shear stresses.
• Tave of the heart in this case was reduced to 5oC after 25 min.
d)
Figure 3. Heart’s surfaces: a) sagittal view, b) outermost surfaces in red, c)
right (pulmonic) heart circulation domain in green, d) left (systemic) heart
circulation domain in blue.
Cooling Container Design
Acknowledgement
 A cooling container with 214 mm length, 212 mm width and 282
mm height, 4 inlets and 4 outlets for internal circulation has been
designed.
 For circulating the coolant outside of the heart, two inlets (15 mm
diameter) and two outlets (20 mm diameter) were placed in
opposite corners of the container walls.
The authors also gratefully acknowledge the FIU Instructional and
Research Computing Center for providing HPC resources in
conducting this project. The research of Chandrajit Bajaj was supported
in part by NIH grant R01-EB004873..
Inlet 1 for External
Circulation
Inlet or Outlet for
Internal Circulation
Figure 5. Velocity and temperature distributions: a) and b) external circulation,
c) and d) internal circulations.
a)
b)
References
c)
1.
Inlet 2 for External
Circulation
2.
d)
e)
f)
3.
Annual Report of the U.S. Organ Procurement and Transplantation
Network and the Scientific Registry of Transplant Recipients:
Transplant Data 2010-2011.
Zhang, Y., Bajaj, C. (2004). Finite element meshing for cardiac
analysis. ICES Technical Report 04-26, the University of Texas at
Austin.
Abdoli, A., Dulikravich, G. S., Bajaj, C., Stowe, D. F., and Jahania, M.
S. (2014). Human Heart Conjugate Cooling Simulation: Unsteady
Thermo-Fluid-Stress Analysis. International Journal of Numerical
Methods in Biomedical Engineering, DOI: 10.1002/cnm.2662.
Contact Information
Outlet 1 and 2 for
External Circulation
Figure 4. Cooling container with all connections and caps for internal
circulations and inlets and outlets for external circulation.
Figure 6. Temperature distribution at: a) 0 min, b) 5 min, c) 10 min, d) 15 min,
e) 25 min, and f) 60 min of cooling.
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