1. Modifying Cardiopulmonary Bypass Machine for Pediatric Patients
Pumped and Ready Group 5: Kelsey Henderson, Krishane Suresh, Kaylee McCormack, Holly Rollin
Department of Chemical Engineering, Auburn University, Auburn, AL, USA
When a patient undergoes open-heart cardiopulmonary bypass surgery, the
blood is transferred to an artificial heart lung machine which receives the deox-
ygenated blood from the patient, oxygenates it, and returns it to the body. This
allows surgeons to temporarily stop the heart while they perform the necessary
repairs. Since most heart lung machines (HLM’s) are designed for adults, and
simply scaling down the machines for pediatric versions may cause unwanted
complications, new designs for pediatric HLM’s are typically considered.
Minimize priming volume of system
Select tubing diameters that maintain laminar flow
Optimize diameter of tubing to minimize shear stress
Minimize length of tubing to reduce effects of shear stress
Optimize for cost and safety of process for patient
Analyze and select ideal process components
1. Laminar flow
2. Differences between male and female negligible
3. Constant density
Modifications and Analysis
Design Schematics
References
Assumptions
Conclusions
Cost and Safety Analysis
Component Analysis
Other necessary components: arterial filter, cannulae, PVC tubing,
air removal device & monitor.
Patient
Classification
Patient age
(years)
Body Surface
Area (m2
)
Aortic Annulus
Diameter (m)
Blood Flow
Velocity (m/s)
Blood Flow
Rate (m3
/s)
Shear Stress
(N/m2
)
Infant/Toddler 0 – 5 0.41 0.0087 0.57 3.39 x 10-5
0.915
Child/Tween 5 - 13 1.10 0.0143 0.595 9.55 x 10-5
0.585
Adult 13 + 1.65 + 0.0201 0.575 1.83 x 10-4
0.400
Table 1: Patient classifications based on various given
Fig 1: Based on these analyses a
membrane oxygenator, a centrifugal
pump, and a pressurized reservoir
were selected as the ideal system
components for each of our rede-
signed systems.
0
50
100
150
200
0 2 4
PrimingVolume(mL)
Tubing Length (m)
Tube Length vs Priming Volume
Separate System
Integrated System
0
50
100
150
200
250
0.0
0.5
1.0
1.5
2.0
2.5
1/8 3/16 1/4 5/16 3/8
PrimingVolume(mL)
ShearStress(Pa)
Tube Diameter (in)
Tube Diametervs ShearStress andPrimingVolume
Shear Stress
Optimal Shear
Stress
Priming
Volume
Final Design Specifications
Minimized priming volume of system by optimizing length and
diameter of tubing
Laminar flow maintained for all tubing sizes
Optimized diameter and length of tubing to minimize shear stress
Optimized for cost and safety of process for patient
Analyzed and selected ideal process components as shown
4. Temperature changes negligible
5. Newtonian fluid (constant viscosity)
6. Tubing surfaces can be considered smooth
0
500
1000
1500
2000
1/8 3/16 1/4 5/16 3/8 7/16 1/2 9/16
ReynoldsNumber
Tube Diameter (in)
Tube Diametervs. ReynoldsNumber
Infant
Child
Fig 7
Fig 8
$32,500
$24,375
$1,000
$24,375
$0
$5,000
$10,000
$15,000
$20,000
$25,000
$30,000
$35,000
Non-Integrated
(conventional HLM)
Integrated (mini-HLM)
Cost(USD)
Cost Comparisonof Non-Integratedand
IntegratedHLMs Startup Costs
Variable Costs
Figures 7 & 8, from Mozol, K., et al., compare
groups M and C. Group M contains infants who
underwent surgery with the miniaturized HLM,
while group C used the conventional HLM.
Figure 9, displays the comparison of start up and
variable costs for the two designs compiled from
data found during research.
Fig 9
Design 1 (Integrated) Design 2 (Standard) Design 3 (Integrated) Design 4 (Standard)
Volumetric Flow Rate (mL/min) 700 700 700 700
Length of Tubing (m) 1 3 1 3
Diameter of Tubing (in) 1/4 1/4 5/16 5/16
Head of pump (cm) 14.361 34.052 6.096 14.161
Shear Stress (Pa) 0.813 0.813 0.416 0.416
Priming Volume (mL) 110.653 149.959 128.458 203.374
Table 2: Critical data for each of the final four designs
1. Arens J., Schnoring H., Reisch. F., et al: Development of a miniaturized heart-lung machine for neonates with congenital heart defect. ASAIO Journal 2008.
2. Viscosity and Density of Blood. http://www.unc.edu/~tammyj/Viscosity.htm (accessed December 2, 2014).
3. Wedro, Benjamin. Pediatric Vital Signs: Get a Helpful Chart. http://www.emedicinehealth.com/pediatric_vital_signs/article_em.htm (accessed December 2, 2014).
4. Mozol K., Haponiuk I., Byszewski A., Maruszewski B.: Cost—effectiveness of mini-circuit cardiopulmonary bypass in newborns and infants undergoing open heart surgery. Kardiologia Polska 2008; 66:9.
5. Perfusion.com. Equipment Sales. http://www.perfusion.com/services/clinical/equipment/equipment-sales (accessed Nov. 30. 2014).
6. Pfuntner, A., Wier L., Steiner C. Cost of Hospital Stays in the United States, 2010. Agency for Healthcare Research and Quality [Online] 2013, 145, 2. http://www.hcup-us.ahrq.gov/reports/statbriefs/sb146.pdf
(accessed Nov. 30, 2014).
Fig 4: Optimization of tube
length with respect to prim-
ing volume
Fig 6: Maintenance of
laminar flow through
varying tube diameter
Fig 5: Optimization of
tube diameter with re-
spect to shear stress and
priming volume
Fig 3: Standard Heart Lung Machine
Fig 2: Integrated Heart Lung Machine
Membrane Oxygenator vs. Bubble Oxygenator
Centrifugal Pumps vs. Positive Displacement Pumps
Pressurized Reservoir vs. Vented Reservoir
Background and Significance
Goals and Parameters
Patient Specifications