P09021: VAD Test Loop
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Establish Target Specifications

Table of Contents

Step 1. Prepare the List of Metrics

The table below presents the metrics, or engineering specifications, that will be used by the team to design against.

List of Metrics
Metric No. Metric Importance Units
1 System Leakage 5 number of leak locations
2 Systemic Vascular Resistance 3 MPa-s/m^3
3 Arterial Complaince 5 mL/mm Hg
4 Venous Compliance 5 mL/mm Hg
5 Blood Damage 5 g Hgb/100 mL
6 Portability 3 minutes
7 Drain Time 3 minutes
8 Fill Time 3 minutes
9 Cost 3 U.S. Dollars
10 System Volume 3 liters
11 Fluid Viscosity 5 N*s/m^2
12 Fluid Density 5 kg/m^3
13 Pressure 5 mm Hg
14 Flow Rate 5 liters/minute
15 Temperature 5 degrees C (F)
16 Data Processing/Ouput 3 seconds
17 Sample Extraction Time 3 seconds
18 Sample Extraction Size 3 milliliters
19 Height 1 inches
20 Length 1 inches
21 Width 1 inches

The metrics, or engineering specifications, that have been created in the preceding list are also directly related to the customer needs. The following link explains the relationship between the related customer needs against the against the metrics (or engineering specifications).

Specifications QFD

Step 2. Collect Competitive Benchmarking Information

The table below contains specifications from existing products/devices that pertain to the LVAD test loop being developed in this project. A field containing "None" denotes either a specification that was not tested by the benchmarking product, or the values were not reported.

Benchmark 1
The University of Virginia created a mock human circulatory loop to test an LVAD under various cardiovascular conditions. The loop was created in an effort to bench test and characterize continuous flow LVADs. This test loop incorporates both the right and left ventricular simulators, while the loop being created by our senior design team will only focus on the left ventricle.

public/UV LVAD Loop.png public/UV LVAD output.png

Competitive Benchmarking Matrix
Metric No. Need Nos. Metric Importance Units Benchmark Value
1 System Leakage 5 number of leak locations None
2 Systemic Vascular Resistance 3 MPa-s/m^3 None
3 Arterial Complaince 5 mL/mm Hg 2.2
4 Venous Compliance 5 mL/mm Hg 50
5 Blood Damage 5 g Hgb/100 mL None
6 Portability 3 minutes None
7 Drain Time 3 minutes None
8 Fill Time 3 minutes None
9 Cost 3 U.S. Dollars None
10 System Volume 3 liters None
11 Fluid Viscosity 5 N*s/m^2 None (water or water/glycerine blood analog)
12 Fluid Density 5 kg/m^3 None (water or water/glycerine blood analog)
13 Pressure 5 mm Hg 80 - 120
14 Flow Rate 5 liters/minute 3.2 - 10.3
15 Temperature 5 degrees C (F) Room temperature
16 Data Processing/Ouput 3 seconds Instantaneous pressure and flow
17 Sample Extraction Time 3 seconds None
18 Sample Extraction Size 3 milliliters None
19 Height 1 inches None
20 Length 1 inches None
21 Width 1 inches None

Step 3. Set Ideal and Marginally Acceptable Target Values

Given the customer needs, awareness of the marketplace, and resource limitations of the current project, preliminary engineering specifications were assigned to each of the metrics. In addition to setting the nominal or target value or each specification, the ideal value that the team should strive for is included in the table below.

List of Metrics
Metric No. Need Nos. Metric Importance Units Marginal value Ideal Value
1 System Leakage 5 number of leak locations 0 - 2 0
2 Systemic Vascular Resistance 3 MPa-s/m^3 90 - 120 100
3 Arterial Complaince 5 mL/mm Hg 1 - 2.2 2
4 Venous Compliance 5 mL/mm Hg 10 - 200 50
5 Blood Damage 5 g Hgb/100 mL 12 - 20 16
6 Portability 3 minutes 1 - 10 5
7 Drain Time 3 minutes 0.5 - 5 2
8 Fill Time 3 minutes 0.5 - 5 2
9 Cost 3 U.S. Dollars 1,000 - 3,000 2,000
10 System Volume 3 liters 0.5 - 1.5 1
11 Fluid Viscosity 5 N*s/m^2 0.0005 - 0.0035 0.0027
12 Fluid Density 5 kg/m^3 800 - 1500 1060
13 Pressure 5 mm Hg 0 - 200 100
14 Flow Rate 5 liters/minute 0 - 10 6
15 Temperature 5 degrees C (F) 21(70) - 49(120) 37(98.6)
16 Data Processing/Ouput 3 seconds 0 - 60 10
17 Sample Extraction Time 3 seconds 1 - 30 10
18 Sample Extraction Size 3 milliliters 2 - 5 4
19 Height 1 inches 36 - 60 48
20 Length 1 inches 12 - 48 36
21 Width 1 inches 12 - 36 30

Step 4. Reflect on the Results and the Process

The final specifications were established to meet the customer needs and are listed above. Determining the necessary metrics as well as the ideal values to fulfill the customer's expectations was no simple task. As the Senior Design course progressed, it was realized that modifactions to these metrics were needed to ensure that the results would be achievable, but still meet the requirements of the customer.

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