Vanderbilt University
Department of
Biomedical Engineering
Developing a Model of the
Inferior Cardiovascular Venous System
April 27, 2009
James Clear
Chase Houghton
Meghan Murphy
Table of Contents……………………………………………………………………………………………………………… 1
Abstract…………………………………………………………………………………………………………………………… 2
Introduction…………………………………………………………………………………………………………………….. 3
Available Models ………………………………………………………………………………………………….. 3
Model Objectives…………………………………………………………………………………………………... 5
Methodology…………………………………………………………………………………………………………………….. 5
Water Retention……………………………………………………………………………………………………. 6
Closed Circuit & Flow Dynamic………………………………………………………………………………. 7
Catheter Insertion Points……………………………………………………………………………………….. 7
Size & Portability…………………………………………………………………………………………………… 8
Heart Design Improvements…………………………………………………………………………………... 9
Results…………………………………………………………………………………………………………………………….... 9
Conclusions……………………………………………………………………………………………………………………….. 11
Recommendations…………………………………………………………………………………………………………….. 12
References…………………………………………………………………………………………………………………………. 12
1
Abstract
Currently, interactive cardiovascular models exist as specific models for accommodating specific
devices. These models are expensive and generally do not allow for visualization of the device inside of
the model. We set out to develop a model of the inferior venous cardiovascular system for visualizing
catheterizations and testing new catheter technologies. In our design, we considered specifications
presented by Vanderbilt University Cardiology Fellow Dr. Michael Barnett, the relevant technology
available, the design flaws of a previous prototype, and machining constraints. The primary objectives
were to make the model anatomically accurate, eliminate water leakage, create a simulated venous
flow and increase its portability. Our final model achieved our design objectives, the expectations of Dr.
Michael Barnett and functioned in the catheterizations identified as specific devices to be tested. The
model that was constructed has commercial and instructional applications. Expansion of the model is
possible in order to simulate arterial or other systems, as well as identifying the source and following
the progression of air embolisms during catheterization.
2
Introduction
In today’s quickly changing field of medical research, attracting venture capitalists and making
proof of concept presentations is essential in developing potential devices. This need presented a
challenge for Dr. Michael Barnett, a Fellow of Cardiology at Vanderbilt University Medical Center. Dr.
Barnett is actively researching and developing several cardiac catheters. His research requires a model
of the inferior venous system for demonstrating catheter function at conferences. Two particular
catheters are currently in development and require a model for demonstration: one is a steerable
catheter and the second is an optical scope catheter. The steerable catheter is intended to improve the
maneuverability of catheters through complex motions while en route to the intended destination. The
optical scope catheter is intended to add a visual display for the doctor of the internal anatomy of the
veins while en route and at the destination site.
In proof of concept studies, Dr. Barnett’s research requires a model to study how feasible
catheter development is, offer metrics of catheter performance, identify any technical issues with the
catheter function, and establish a budget for catheter production. A model of the inferior venous
system that meets these demands does not currently exist. The relevant technology that is currently
available includes catheterization simulators, cast models of the heart or the veins exclusively, and
various models designed for device specific testing. Each of these models has restrictions which do not
allow clear visualization of catheterizations.
Available Models
The Mentice VIST is a pricey endovascular simulator which is commonly used in clinical training.
The simulator is able to present the physician with various scenarios that occur during catheterizations.
Unfortunately the simulator does not allow for any visualization of
catheter movement within the patient, as would be the case during
actual surgery. While the simulator has a series of available modules,
no modules are available for testing Dr. Barnett’s developing
prototypes.1 For these reason, the simulator does not meet the
demands of Dr. Barnett. Further, the cost of the Mentice,
approximately $40,000, puts it well outside a reasonable price range
Figure 1. Mentice VIST endovascular
for a clear system offering visualization of catheter movement.
simulator1
Dynamic Med Demo is second producer with interactive medical products. Dynamic Med offers
models meeting more of the demands Dr. Barnett is seeking, including clear acrylic casts, but the
models do not offer both venous vasculature and access to the heart. Dynamic Med offers a peripheral
showcase and a heart valve replacement demonstrator. The peripheral showcase shown in Figure 2
would allow visualization of catheter movement through the vasculature but being an open circuit, no
flow would be possible and access to the heart would not be feasible.2 The heart valve replacement
demonstrator (Figure 3) offers a crystal clear heart for visualizing a heart valve replacement but lacked
1
2
http://www.mentice.com/archive/pdf_products/Mentice_A4_broschyr_LR2.pdf
http://www.dynamicdemo.net/an_05.html
3
anatomical accuracy. The system does involve full flow by
manually squeezing a bilge pump but a secondary
technician would be necessary to introduce flow during
catheterization. The model also included external
equipment (a flat screen display of the valve replacements)
that was costly and of no use in Dr. Barnett’s proof of
concept demonstrations. Costing $8,000, the model was
outside Dr. Barnett’s price range, especially considering the
model lacks anatomical accuracy.3
In a second form of device testing, there exist
companies that will perform testing particular devices at a
high cost. Mecmesin is one such company. Mecmesin’s
purpose is to test the usability and “fitness-for-purpose” of
medical devices and whether the device conforms to
regulatory standards. Device testing offered by Mecmesin
includes tensile and compressive strength testing for
materials, sharpness and penetration forces, torque testing,
etc.4
Figure 2. Dynamic Med Demo
Peripheral Showcase
Figure 3.Dynamic Med Heart Valve
Replacement Demo
Other device specific models have been patented
with the same purposes. The models are developed with
very specific purposed and do not accommodate for
visualization or modularity. For example, a model was patented for testing prosthetic tricuspid valve
replacements. The leaflet valve is exposed to in vivo loading including forward pressure applied to the
valve as well as backflow pressure. This device was intended to simulate the fatigue experienced by
prosthetic valves in term long use. The device was also intended to test for defects affecting
functionality.5 Another model that has been created is used for modeling flow dynamics through a
prosthetic bicuspid valve. The model uses an agar gel with characteristics of biological tissue and an
ultrasound to study flow through the left ventricular and aortic chambers.6 A third model was identified
that tests ventricle assist devices (LVAD). The model demonstrates pumping performance and flow
dynamics through LVADs with resistance comparable to the native heart.7
3
http://www.dynamicdemo.net/dem_01.html
http://www.mecmesin.com/test-solutions/solutions-by-industry/medical-devices
5
Appartus for Testing Prosthetic Heart Valve Hinge Mechanism. More RB et al., inventors. United States Patent
US5531094. http://www.freepatentsonline.com/5531094.pdf accessed 12 Nov 2009
6
Durand LG, Garcia D, Sakr F, et al. A New Flow Model for Doppler Ultrasound Study of Prosthetic Heart Valves.
Journal of Heart Valve Disease. [Internet] 2006 Nov 4 [cited 12 November 2009]; 17. Available from:
http://www.icr-heart.com/journal/
7
Pantalos GM, Koenig SC, Gillar KJ, Giridharan GA, Ewert DL. Characterization of an adult mock circulation for
testing cardiac support devices. ASAIO. Feb 2004; 50(1):37-46
4
4
Model Objectives
The goal of our design process was to develop a portable and anatomically accurate model of
the inferior venous system for demonstrating various catheter insertions. Further, we felt making such a
model commercially available would potentially expand research in catheter development. A senior
design group attempted to address this need in 2009and generated a model that was somewhat
functional for Dr. Barnett (Figure 4). However, there were fundamental issues with the model which we
intended to address in our model’s design.
Figure 4. Prototype established in 2009 under Dr. Barnett
To fulfill the goals of our design process and in light of the prototype established in 2009, we
established several design objectives for our model. The first objective was to establish a clear model
free of visual obstruction. The second objective was to ensure the model was entirely water tight yet
capable of being emptied and refilled. After achieving a clear model without leaking, the next objective
was to generate an anatomically representative venous flow gradient. The fourth objective was to
create an anatomically representative heart that would allow for catheter access. The fifth objective
was to meet the size constraints of carry-on luggage with model dimensions of 22” x 14” x 9”8. Finally,
we established a manufacturing cost objective of approximately $2,000 considering the costs of
currently available models.
Methodology
The ultimate design of our cardiovascular model entailed prioritizing the features we were
seeking and making adjustments to the model previously created by the senior design team in 2009.
Considering the aforementioned design objectives and the previous model, we sought to eliminate all
leaking joints, modify the structure of the model to eliminate wasted space and increase its portability,
close the circuit and add fluidic flow, and improve the anatomical representation of the interior of the
8
http://www.delta.com/traveling_checkin/baggage/carryon/index.jsp
5
heart. Finally, we sought an aesthetic, professional model that would be well regarded during
presentations.
Water Retention
In order to develop a tubing system that did not leak, we began with studying materials and
considering several adhesives. We first discussed some options with a silicone tubing distributor and
learned that silicone glue could only be melded if at the same ratio and material that it’s being glued to.
Following this, in discussions with John Fellenstein at the Vanderbilt machine shop, we were informed
that acrylic could be sealed to other acrylic pieces using dichloroethylene or an acrylic cement.
Dichloroethylene is a very strong acrylic adhesive as it welds two neighboring acrylic parts together by
melting the plastic structures together. However, the adjoining pieces must have a very flat surface
interface. The acrylic cement on the other hand would more properly join acrylic pieces at machined
surfaces. It was therefore primarily used but the dichloroethylene was used supplementary to ensure
complete water tightness. In addition to gluing acrylic parts to each other, we designed a Y-connector,
which represents the inferior vena cava bifurcation, by using double o-rings to prevent leaking at those
joints. This type of o-ring connection also contributed to the modularity of the model and the ability to
exchange the limbs representing the femoral veins.
In order to connect the pump to the rest of the acrylic circuit, flexible silicon tubing (½'' inner
diameter , ¾" outer diameter) was used. In a push on fashion the flexible tubing was sealed over the
pump input and output connectors which
had a ½'' outer diameter. This provided a
proper seal at the pump interface as but was
unsuitable for interfacing with the ¾'' outer
7/16''
9/16''
diameter tubing of the model. Therefore two
tubular connectors were manufactured: one
for the input to the model from the pump
and one for the output from the heart to the
Figure 5. Schematic of connector to interface silicon
pump (Figure 5). One end of these
tubing from pump to the acrylic tubing from the
connectors was tapered with a maximum
model.
outer diameter slightly under ½'' so that it
would slide into the ½'' inner diameter of the model. The other end had an outer diameter slightly over
½'' so that the flexible silicon tubing would form a water tight seal after being pushed over this end. To
further ensure proper sealing metal tube clamps were used over the silicon tubing pressed over the
larger diameter end of the connector. The smaller diameter end was glued into the ½'' inner diameter
tubing prevalent in the model. It is important to note that one connector was constructed from acrylic
tubing while the other was constructed from aluminum tubing. The acrylic connector was an inch long
and connected to a two inch segment of ½'' inner diameter tubing. This tubing was then pushed into
the bottom Y-connector. The aluminum tubing was three inches long to allow for more overlap
between the connector and the silicon tubing in an attempt to prevent leaks. It was constructed from
aluminum to give it more structural integrity which allowed for the tube clamp to be sealed much
tighter and further reduce the potential for leaking.
6
To prevent leaking from the heart, where the two halves were bolted together, a material was
chosen for the septum that was slightly flexible to allow compression, but firm enough to withstand the
pressures created by the pump. Finally, in order to capture any liquid that might leak during use of the
cardiovascular model, a rectangular acrylic base was constructed for the model to rest on while in use,
and was equipped with 1” high acrylic walls around the edge that were glued using acrylic bonding
cement.
Closed Circuit & Flow Dynamic
In order to create a closed circuit, part of the rigid acrylic tubing needed to be bent into a semicircle. We decided that if we heated the tubing, we may be able to bend it. Using a heat gun, we
experimented using high and medium heat, as well as bending the tube faster or slower. Throughout all
bending experiments, we kept the tubing flat on the table so as to be sure that all bending was
occurring in one plane and that no twisting occurred. We found that if the tubing got too hot or if we
bent it too fast, it would result in kinks. We also experimented with putting sand into the tube to help
reduce the amount of kinking and maintain the same inner diameter of the tube throughout the
bending process. This however, ended with sand being engrained in the part of the tubing that was
heated, causing a decrease in the clarity. The best results occurred when we attempted slower heating
over a 1”-1.5” length of tubing and allowed for some cooling before bending. In order to ensure a
standard bending radius for the final bent tubes, we used a metal cylinder to bend the tubes around.
The cylinder was coated in acrylic glue to prevent the heated tube from sticking to the metal during
bending. This grease did not leave any residue engrained in the tubing after cooling of the acrylic tube.
In selecting a pump to create flow throughout the cardiovascular model, we consulted with Dr.
David Merryman, an assistant professor in the Departments of Biomedical Engineering, Medicine and
Pediatrics. On his advice we explored using a bellows metering pump to generate a pulsatile flow
similar to that found in the venous system. A Gorman Rupp Industries bellows pump was selected for its
suitable flow requirements and compact size. The pump used was an adjustable Compact Bellows
Metering Pump with a 2” bellows size, a motor RPM of 90 at 60 Hz, a maximum flow rate of 1620
mL/min, and a ½” inner diameter input and output.9
Catheter Insertion Points
Unlike the previous prototype, this cardiovascular model was designed to be a closed circuit to
allow for flow from the femoral veins through the heart. Accordingly catheter access holes need to be
created in the tubing. This was accomplished by drilling holes into the tubing representing the femoral
veins. The holes were drilled at a 45 degree angle to prevent the catheters from needing to bend at an
extreme angle when inserted into the model. Moreover, the largest hole possible was drilled (a ½” hole
into a ½” inner diameter tube) in order to allow the largest feasible device to be inserted into the
model. To accommodate for smaller catheters, rubber stoppers were inserted into the catheter access
holes. These rubber stoppers were then drilled to create a more appropriately sized catheter insertion
9
Gorman Rupp Industries. Compact Bellows Pump Selection Guide. [Internet] ©2009. Available from:
http://www.gripumps.com/upload/products/CompactBellowsPumpSelectionGuide0310.pdf
7
point. These smaller holes were sealed with a catheter sheath with a one way valve that prevented
water from squirting out. The diameter of these holes could be adjusted between stoppers to
accommodate the various sizes of the catheters. However, because the catheter insertion hole was
drilled at an angle, a normal rubber stopper was not able to properly seal the hole. To accommodate
for this, an endmill was used on one end of another ½” inner diameter, ¾” outer diameter acrylic tube
at 45 degrees so that it would line up exactly with the hole drilled into the femoral vein tube (Figure 6).
This angled tube was then glued onto the femoral vein tube and since it terminated in a circle a rubber
stopper created a proper seal.
ID:
OD:
Figure 6. Side profile of bent acrylic tubing representing femoral
vein complete with catheter insertion point.
Size & Portability
Our overall goal for the size of the model was that it could be small enough to fit inside of a
standard carry-on suitcase in order for it to be able to travel safely and easily. The most significant way
in which we decreased the size of the old model was by eliminating all of the tubing representative of
the veins superior to the heart. Weight considerations of materials remained a priority for all parts of
the cardiovascular model as well. While a prime candidate for effectively sealing joints, hard acrylic
tubing was heavier than the soft plastic used in the previous model. However, because the acrylic is
relatively light, and because the leaking issue and poor clarity at joints was a key problem with the
previous design, this trade off was acceptable. We further minimized the size of the model by reducing
the bend radius of the tubing representing the femoral veins. This was the limiting factor to the model
height and after establishing this radius the exterior heart size and pump location were designed
accordingly.
Another feature of our cardiovascular model that helped increase its portability was the use of
o-rings at the Y-connector which simulated the inferior vena cava bifurcation. Because the parts of the
model are not glued at this juncture, the limbs representing the femoral veins are removable from the
upper half of the model and can be stored separately during travel. This allows the model to be
disassembled into parts which are 13'' x 6 '' X 6 '' at the largest. This feature also allows for the
8
interchange of different sized limbs representing the femoral veins. This exchange permits the distance
between the insertion point and heart to be easily changed if need be.
Heart Design Improvements
Initially we explored materials and methods for casting a model of the heart. Machining acrylic
leaves a slightly hazy finish which we hoped to eliminate all together by constructing the heart from
clear casting materials. We experimented with two shore hardness ratings of clear polyurethane
casting compound (70A, 80D). After attempting several casts we noticed that the polyurethane had
numerous bubbles and was also hazy. We came to learn however, by contacting the manufacturing
company, that the polyurethane was rated at clear only up to ¼'' thickness. Furthermore, we struggled
with releasing the mold as well with what to make the mold out of and which materials to use.
Eventually we deemed that casting the heart was unfeasible given our objectives and difficulty achieving
success with the geometry and clarity. We finally decided on making a machined acrylic model of the
heart which would mimic the shapes and volumes of the right atrium and ventricle. By taking this
approach we were able to generate a model of the heart with ovular/ellipsoid chambers of relative
similarity to the actual heart while also devising a way for the chambers to contact the septum. For the
purposes of our model we concerned ourselves only with the right side of the heart. We wanted an
input from the modeled inferior vena cava coming directly into the right atrium and an output returning
to the rest of the model exiting from the right ventricle. This was due to the need to model only inferior
venous catheterizations.
Results
Our final model of the venous system
consisted of clear, acrylic tubing and a heart
fabricated from acrylic blocks. Each half of the
heart was sealed with acrylic cement, as was the
inferior vena cava – heart connection. The
inferior vena cava bifurcation was created out of
acrylic blocks and was sealed with double o-rings
at each connection. The final bend radius of the
acrylic tubing was 2”. The model rests on a blue
acrylic base with 1” tall walls and flexible tubing
connecting the venous circuit with a bellows
metering pump (Figure 7).
Figure 7. Top view of final cardiovascular
The final heart model consists of 4 blocks
model resting on blue acrylic surface.
of acrylic with hemi-elliptical shapes hollowed into
them. Each half of the heart is formed from a bottom and top half. The two halves of each side of the
heart are sealed together with acrylic cement. The right and left sides of the heart are bolted together
but are separated by a cork gasket representing the septum. The atria are modeled by an ellipsoid with
radius 0.7'' and height 0.75'', while the ventricles are represented by an ellipsoid with radius 0.75'' and
9
height 1.2''. The top and bottom half of these shapes are hollowed out into the respective portions of
the acrylic blocks. When sealed together these blocks created the chambers of the heart with a close
representation to the anatomy of the heart, as shown in Figure 8. The septum was modeled by a cork
gasket. Each chamber of the heart had direct access to the septum through an oval window created by
cutting down the side of the ellipsoid shaped heart approximately 0.2'' from the side of the hollowed
out heart. This cut was made after the top and bottom half of one side of the heart were glued together
so as to provide more structural integrity during the cut. This process was akin to slicing through a
bowling ball pin a few centimeters from the edge.
Figure 8. Top view of our computerized design of the two sides of the heart model (left), an
electrocardiogram of a heart (middle), and our final acrylic heart (right).
Our final cardiovascular model prototype successfully
addressed the design objectives outlined. With the entire model
assembled and filled with water, the model successfully retained all
water after sitting for 72 hours. In addition, no leaking occurred
while the pump was turned on for a continuous 30 minutes. To
visually confirm that the water was flowing while the pump was
turned on, a bolus of dye was injected into the model at one of the
catheter insertion points. The dye was then observed to flow up
the femoral vein limb, into the heart and pump, followed by return
into each of the femoral vein limbs.
6”
6”
10”
1” ID
9”
9”
In addition to passing tests of water retention and
simulated venous flow, the dimensions of our cardiovascular model
½” ID
were satisfactorily comparable to their corresponding anatomical
values, as shown in Table 1 and Figure 9. Although the model was
Figure 9. Overall layout of final
not anatomically exact the model was representative in the sense
model, with dimensions
of depicting approximate physiology. The percent errors of the
model dimensions hover between 20 and 30 % (Table 1) but this error was an acceptable trade off to
10
helping to visualize catheter deliveries as requested by Dr. Barnett. The model furthermore is modular
to pieces 13’’ x 6’’ x 6’’ or smaller. This fulfills the ability of the model to be stowed in carryon luggage if
properly packed to prevent damage in travel. The only exception to this objective is the blue base which
is 28’’ x 16’’. This however can be stored on checked baggage and would therefore still be portable.
Vein
Tubing Value
1"
0.5”
10” (not including SVC)
Error
IVC Inner Diameter10
R/L Femoral Inner Diameter11
IVC Length12
Anatomical Value
~0.81”
~0.41”
~14” (including SVC)
Chamber
R/L Atrium13
R/L Ventricle14
Anatomical Volume
~2.37 in3
~3.60 in3
Model Volume
1.53 in3
2.82 in3
Error
35%
22%
23%
20%
29%
Table 1. Comparison of Anatomical Sizes with Model Sizes
The proposed model is able to successfully demonstrate the use of various catheters and other
intracardiac devices in a system that is anatomically representative of an average human. The model
offers a competitive cost advantage over
Model
Total Cost
the models currently available. Further,
Proposed
$2,380
the majority of the expense in building our
Mentice VIST
$40,000
model came from machining costs which
Dyanamic Med Peripheral Showcase
$4,000
would be lowered if the model were
Dynamic Med Valve Replace.
$8,000
produced on a commercial scale. The ease
Table 2. Comparative table of current
of machining also allows for adaptations to
cardiovascular models.
the model as demanded by various users.
Conclusions
The prototype created successfully meets the specific device objectives. For proof of concept
presentations or for use in clinical training, the model allows for clear visualization of catheterizations.
10
Prince, MR., Novelline, RA., et al. The Diameter of the Inferior Vena Cava and Its Implications for the Use of
Vena Cava Filters. Radiology. 1983;149:687-689.
11
Hertzberg, BS., Kliewer, MA., et al. Sonographic Assessment of Lower Limb Vein Diameters: Implications for the
Diagnosis and Characterization of Deep Venous Thrombosis. American Journal of Roentgenology. 1997;168:12531257.
12
Takayama, T., Hirai, S., et al. Measurement of the Vena Cava at Postmortem Examination, From the Upper End
of the Superior Vena Cava Via the Right Atrium to the Lower End of the Inferior Vena Cava. Clinical Anatomy.
6:349-352 (1993).
13
Wang, Y., Gutman, JM., et al. Atrial volume in a normal adult population by two-dimensional echocardiography.
Chest. 1984;86:595-601.
14
Nakagawa, Y., Fujimoto, A., et al. Assessment of the normal adult right ventricular diastolic function using Mmode echocardiographic measurement of tricuspid ring motion. International Journal of Cardiac Imaging.
1998;14:391-395.
11
Further, the model offers anatomically representative dimensions with an accurate venous flow
gradient. Catheters of various diameters may be inserted with a maximum outer diameter catheter size
of .5in. This size allowance meets the requirements for the optical scope proof of concept testing and
demonstration. Access to the right atria and ventricle allows for use of Swan-Ganz catheters to measure
intracardiac pressures. Access between the right and left atrium and ventricles and the presence of a
biomemetic septum allows for testing catheters penetrating the septum.
Recommendations
Future work will involve establishing a means of casting the heart to achieve an anatomically
correct exterior in addition to an anatomically correct interior. This casting will potentially involve
plaster of paris and a cadaver heart. This construction will involve close work with Mr. Ray Booker and
the Vanderbilt Simulation Center.
A second avenue of future work will involve adding a modular superior venous system as well as
portions of the arterial system. Expanding the vasculature represented will allow for simulation of a
larger number of processes and catheterizations. This could be done by adding on to the current model
or by producing other models. Factors such as the size, portability and complexity will need to be
considered to determine the best approach to accomplish these expansions. One possible use for an
anatomically expanded device is detecting the introduction of air embolisms during catheterization. This
avenue is of particular importance to the Simulation Center as Mr. Bookers has communicated a need
for this training in the lab. His emphasis on the short comings of the Mentice VIST simulator and the
demand for a system with clear visibility reiterates the value of our model and the future uses for our
model.
Ethical issues will arise in casting the heart from a cadaver heart but this is a worthwhile avenue
to pursue because of the advantages of our model and its demand. Otherwise, the model was
constructed entirely of acrylic tubing and presents no other ethical concerns. Its uses will be limited
entirely to in vitro demonstrations.
References
http://www.mentice.com/archive/pdf_products/Mentice_A4_broschyr_LR2.pdf
http://www.dynamicdemo.net
http://www.dynamicdemo.net
http://www.mecmesin.com/test-solutions/solutions-by-industry/medical-devices
Appartus for Testing Prosthetic Heart Valve Hinge Mechanism. More RB et al., inventors. United States
Patent US5531094. http://www.freepatentsonline.com/5531094.pdf accessed 12 Nov 2009
12
Durand LG, Garcia D, Sakr F, et al. A New Flow Model for Doppler Ultrasound Study of Prosthetic Heart
Valves. Journal of Heart Valve Disease. [Internet] 2006 Nov 4 [cited 12 November 2009]; 17.
Available from: http://www.icr-heart.com/journal/
Pantalos GM, Koenig SC, Gillar KJ, Giridharan GA, Ewert DL. Characterization of an adult mock circulation
for testing cardiac support devices. ASAIO. Feb 2004; 50(1):37-46
http://www.delta.com/traveling_checkin/baggage/carryon/index.jsp
Gorman Rupp Industries. Compact Bellows Pump Selection Guide. [Internet] ©2009. Available from:
http://www.gripumps.com/upload/products/CompactBellowsPumpSelectionGuide0310.pdf
Prince, MR., Novelline, RA., et al. The Diameter of the Inferior Vena Cava and Its Implications for the
Use of Vena Cava Filters. Radiology. 1983;149:687-689.
Hertzberg, BS., Kliewer, MA., et al. Sonographic Assessment of Lower Limb Vein Diameters: Implications
for the Diagnosis and Characterization of Deep Venous Thrombosis. American Journal of
Roentgenology. 1997;168:1253-1257.
Takayama, T., Hirai, S., et al. Measurement of the Vena Cava at Postmortem Examination, From the
Upper End of the Superior Vena Cava Via the Right Atrium to the Lower End of the Inferior Vena
Cava. Clinical Anatomy. 6:349-352 (1993).
Wang, Y., Gutman, JM., et al. Atrial volume in a normal adult population by two-dimensional
echocardiography. Chest. 1984;86:595-601.
Nakagawa, Y., Fujimoto, A., et al. Assessment of the normal adult right ventricular diastolic function
using M-mode echocardiographic measurement of tricuspid ring motion. International Journal
of Cardiac Imaging. 1998;14:391-395.
13