baxter (flo-gard 6201) volumetric infusion pump flow rate accuracy - test design and performance...
DESCRIPTION
In the clinical settings, continuous monitoring the fluid line (e.g. saline, medications, antiseptic drugs) is critical for quality control and safety purposes. Thus, there is a serious need for a reliable infusion pump that is sensitive, electrically safe and patient safe. One of the most important factors impacting a pump performance is its flow rate. Subsequently, there are various methods to verify the degree to which the flow rate is accurate. At times, depending on the application of the infusion therapy (in anesthesia or for the purpose of medication administration), accuracy of the flow rate can critically endanger both the safety of the user and the patient. This report presents five methods to examine the accuracy of the Baxter (Flo-Gard 6201) infusion pump.TRANSCRIPT
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UNIVERSITY OF BRITISH COLUMBIA
BMEG 550 GRADUATE PROJECT WRITTEN FINAL REPORT
APRIL 3, 2013
______________________________________
BAXTER (FLO-‐GARD 6201) VOLUMETRIC INFUSION PUMP
FLOW RATE ACCURACY: TEST DESIGN AND PERFORMANCE VERIFICATION
______________________________________
Soheil Haji Mohammadi Hanieh Kamelian Kousha Talebian
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Abstract In the clinical settings, continuous monitoring the fluid line (e.g. saline, medications, antiseptic drugs) is critical for quality control and safety purposes. Thus, there is a serious need for a reliable infusion pump that is sensitive, electrically safe and patient safe. One of the most important factors impacting a pump performance is its flow rate. Subsequently, there are various methods to verify the degree to which the flow rate is accurate. At times, depending on the application of the infusion therapy (in anesthesia or for the purpose of medication administration), accuracy of the flow rate can critically endanger both the safety of the user and the patient. This report presents five methods to examine the accuracy of the Baxter (Flo-‐Gard 6201) infusion pump.
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Table of Content Abstract .......................................................................................................................................................... 2 1. Scope .......................................................................................................................................................... 4 2. Objective ................................................................................................................................................... 4 3. Introduction ............................................................................................................................................ 5 3.1. Baxter Infusion Pump ................................................................................................................. 5 3.2. Flow Rate Calculation ................................................................................................................. 5 3.3. Clinical Consideration While Setting the Flow Rate ...................................................... 6 3.4. Flow Rate Accuracy ..................................................................................................................... 6 3.5. Functional Block Diagram ........................................................................................................ 7
4. Methods to Test the Flow Rate Accuracy ................................................................................... 8 4.1. Test Parameters ............................................................................................................................ 8 4.2. Criteria to be Considered During Testing .......................................................................... 8 4.3. Instruments Needed .................................................................................................................... 8 4.4. Test Setup ........................................................................................................................................ 8 4.5. Test Procedures ......................................................................................................................... 10 4.5.1. Method 1 -‐ Measurement by Weight per Time .................................................... 10 4.5.2. Method 2 -‐ Measurement by Volume per Time ................................................... 10 4.5.3. Method 3 -‐ Measurement by Time per Volume ................................................... 11 4.5.4. Method 4 -‐ Measurement Incorporating VTBI Option ...................................... 11 4.5.5. Method 5 -‐ One-‐Hour Accuracy Test ........................................................................ 11
5. Results .................................................................................................................................................... 12 6. Discussion ............................................................................................................................................. 14 7. Factors Affecting Test Results & Accuracy .............................................................................. 15 8. Conclusion ............................................................................................................................................. 16 9. Recommendation / Future Work ................................................................................................ 16 10. Bibliography ...................................................................................................................................... 17 Appendix A: Method 1 Data ................................................................................................................ 18 Appendix B: Method 2 .......................................................................................................................... 19 Appendix C: Method 3 & Method 4 ................................................................................................. 20 Appendix D: Method 5 .......................................................................................................................... 21
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1. Scope This report introduces five methods to measure and examine the accuracy of the Baxter Single Channel (Flo-‐Gard 6201) Infusion Pump flow rate. The report is partitioned to the following sections: Objective, Introduction (i.e. Types of Infusion, Baxter Infusion Pump, Flow Rate Calculation, Clinical Consideration While Setting the Flow Rate, Flow Rate Accuracy and Functional Block Diagram), Methods, Results, Discussion, Factors Affecting the Accuracy of the Flow Rate and, Conclusion.
2. Objective As mentioned previously in the Abstract, inaccuracy and malfunction of infusion pumps can result in serious and critical complications and harm to the patient. Accordingly, our aim from this project was to design test methods to measure and verify the Baxter infusion pump flow rate accuracy.
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3. Introduction Infusion pumps are electronic devices used to control administration of intravenous fluids in very small amounts and at a carefully regulated rate over selected period of time. They are classified based on their volume capacity (i.e. small or large), type of pump (i.e. volumetric or syringe) and flow rate mechanisms (i.e. through gravity or roller pump). According to FDA, an infusion pump is a Class II device. However, Health Canada has classified it as a Class III device by (Rule 11 and Sub Rule (1)), where it is described as an active, therapeutic and surgically invasive device (Chan, 2013).
3.1. Baxter Infusion Pump The Baxter (Flo-‐Gard 6201) infusion pump is an electromechanical type pump. Similar to any other infusion type, it is used for the intravenous infusion of liquids such as medications, nutrients and antiseptic administrations; the user can select the rate. The pump is composed of a linear peristaltic pump head, which is programmable (MadWrench, LCC, 2011) (Systems Integrated Medical, 2011). The pump uses Volume-‐Time Programming. This technology allows us to select a volume-‐to-‐be-‐infused (VTBI) and the amount of time over which the infusion is to take place. Then, the pump automatically calculates the flow rate required to deliver the desired VTBI in that specific time period. If the calculated flow rate is higher than the pump’s capabilities, the pump will display the message “Hi”; similarly, if the calculated flow rate is lower than the pump’s capabilities, the pump will display the message “Lo” There are currently 5 applicable methods to test for the flow rate accuracy of the Baxter infusion pump (MadWrench, LCC, 2011) (Systems Integrated Medical, 2011).
3.2. Flow Rate Calculation Fluid flow rate (FR) occurs as a result of the relationship of pressure (P) and resistance (R).
𝐹𝑅 =𝑃𝑅
Flow rate impacts resistance and resistance impacts the amount of pressure required to achieve the flow rate (Mocklin, 2011).
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3.3. Clinical Consideration While Setting the Flow Rate The following principles apply to flow rates (Mocklin, 2011):
• High-‐resistance systems require the most amount of pressure (e.g., infusing into a hypertensive patient with left ventricular hypertrophy or pulmonary hypertension).
• High flow rates in low resistance systems will require less pressure than in high resistance systems (e.g., infusing fluid rapidly into a hypotensive patient in shock).
• Low flow rates in high resistance systems will require less pressure than high flow rates (e.g., infusing at the Keep Vein Open [KVO] rate into the hypertensive patient).
• Low flow rates in low resistance systems will require the least amount of pressure. For example, KVO rate into a hypotensive patient.
3.4. Flow Rate Accuracy Most infusion pump manufacturers state the accuracy of the delivered dose as a percentage. A user manual may read ‘accuracy: ±5%’. Ideally, this should be the flow rate accuracy, meaning that over the complete period of infusion, the flow rate (in mL/hour) will not vary beyond these limits. Such pumps should have a smooth and steady delivery. Sometimes, however, the quoted accuracy may refer to the total volume delivered by the end of the infusion period. In such cases, the final dose will be within the specified limits, but no indication is given on how constant or smooth the flow has been during infusion. For syringe pumps, which make use of single-‐use syringes, many manufacturers define the accuracy of the linear displacement of the plunger. This is the mechanical accuracy of the pump itself and excludes the additional error caused by the inconsistency of single-‐use syringes. The user should be aware that single use syringes might cause flow deviations up to 4% greater than those specified for the linear displacement. As the maintenance of constant blood levels may be critical for some drugs, it is important to search the user manual or any accompanying literature for further references to accuracy (Ferrari & Beech, 1995).
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3.5. Functional Block Diagram Figure 1 shows the functional block diagram for a generic volumetric infusion pump. On the left hand side, the user input (e.g. VTBI)/output interface is shown. On the right hand side, the internal block diagrams of the pump are shown.
Figure 1: Functional block diagram of an infusion pump
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4. Methods to Test the Flow Rate Accuracy
4.1. Test Parameters ● Weight (g) ● Volume to be Infused (VTBI) (mL) ● Time (s)
4.2. Criteria to be Considered During Testing The following assumptions and factors were considered during the testing: ● The infusion set is correctly primed and used. ● There are no structural and functional defects in the infusion pump. ● The infusion line is good for the repetition of tests. ● There is no movement in the line as the water is passed through. ● The height at which the line is set at is the same as the one set for patient’s
infusion therapy.
4.3. Instruments Needed ● Baxter (Flo-‐Gard 6201) volumetric infusion pump ● A crystal bowl ● A calibrated scale with a resolution of at least 0.1 grams ● ASTM Class A 25mL graduated cylinder with a resolution of at least 0.2mL ● Baxter Continu-‐Flo solution set ● Solution fluid (i.e. distilled water)
4.4. Test Setup The following four steps are required for the preparation of the test (MadWrench, LCC, 2011) (Systems Integrated Medical, 2011). The experimental setup is shown in Figure 2:
1. Using a solution container (distilled/sterile water, 0.9% sodium chloride, or D5W) and a Baxter Continu-‐Flo administration set with at least one Y-‐site, prepare the administration set according to the instructions accompanying the set. 2. Spike the solution container and fully prime the set. Remove all trapped air bubbles from all components. Hang the solution container, and ensure the fluid level is at least 18” above the top of the pump handle throughout the test.
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Note: The tubing must be clean and dry before it is inserted into the pump. Make sure that the tubing is placed and seated properly in the guide channel, pump mechanism, sensors, and safety clamp. Ensure that there is no slack in the tubing and that it is not kinked or pinched before closing the pump door.
3. Load the set into the pump. Close the pump door. There should be no excessive resistance. Never use tools or excessive force to close a pump door. 4. Place the distal end of the administration set in a container or sink to dispose of pumped solution.
Note: Do NOT reuse a tubing segment once it has been used.
Figure 2: Experimental setup.
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4.5. Test Procedures Below represents four short time accuracy tests, as well as a one-‐hour long accuracy test for the Baxter infusion pump. The four short tests compute the infusion rate by measuring weight per time, volume per time, time per volume, and VTBI (Volume to Be Infused). At the end of this document, five data-‐collection charts are included to referring to the five tests. All methods are used to calculate the infusion rate, but only M1, M2 and M5 are used to measure the accuracy of the infusion rate. And for validating the accuracy of each of three methods better, there are two approaches to M1, M2 and M5: one is measuring the infusion rate by plotting the result and calculating the slope and the other one is dividing the final volume by the total time to get the average infusion rate. The following five methods have been taken from the operation manual (MadWrench, LCC, 2011) (Systems Integrated Medical, 2011). As such, the content has been modified, but may still contain phrases from the original script.
4.5.1. Method 1 -‐ Measurement by Weight per Time 1. Program a PRI VTBI of at least 500mL and start the pump at 200 mL/hr. 2. Place a container on a calibrated scale with a resolution of 0.1 grams or
better and zero the scale. 3. Measure the weight of the container every 30 seconds ± 3 seconds for
duration of 10 minutes and 30 seconds. 4. Divide the weight by specific gravity of the solution (water’s specific gravity
is 0.998 g/mL at room temperature) and plot the results. The slope of the line is the infusion rate.
5. Divide the final weight from the total time and by the specific gravity to get the average infusion rate.
6. The total solution collected at the 10-‐minute deadline should be between 32.5mL to 37.5mL.
4.5.2. Method 2 -‐ Measurement by Volume per Time 1. Program a PRI VTBI of 20mL and start the pump at 200mL/hr. 2. Collect the solution in an ASTM Class A 25mL graduated cylinder, with a
resolution of 0.2mL or better. 3. Monitor and measure the collected volute for 6 minutes and 30 seconds
using 30 seconds ± 3 seconds interval, or until the pump switches to KVO mode. Note: Stop the pump within 10 seconds after the KVO alert, since fluid delivered after the KVO alert adds to the test error
4. Plot the results. The slope of the line is the infusion rate. 5. Divide the final volume from the total time to get the average infusion rate. 6. The total solution collected at the 6-‐minute deadline should be between
18.6mL to 21.4mL.
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4.5.3. Method 3 -‐ Measurement by Time per Volume 1. Program a PRI RATE of 200mL/hr and a PRI VTBI greater than 35mL. 2. Collect the solution in an ASTM Class A 25mL graduated cylinder, with a
resolution of 0.2mL or better. 3. Measure the time within 3 seconds that it takes to collect 25mL ± 0.2mL. 4. Calculate the flow rate in mL/hr by dividing 35mL by the measured time
converted to hours. 5. The flow rate should be between 186.0mL/hr and 214.0 mL/hr.
4.5.4. Method 4 -‐ Measurement Incorporating VTBI Option 1. Program a PRI RATE of 200mL/hr and a PRI VTBI of 35mL. 2. Start the pump and collect the solution in a container of known weight. When
the pump goes into KVO alert mode, stop the pump within 20 seconds. 3. Use a calibrated scale with a resolution of 0.1 grams or better to weigh the
container and solution. Then divide the solution weight by the specific gravity of the solution (water’s specific gravity is 0.998 g/mL at room temperature).
4. The solution collected should be between 32.5mL and 37.5mL.
4.5.5. Method 5 -‐ One-‐Hour Accuracy Test 1. Program a PRI RATE of 125mL/hr with a PRI VTBI of 1000mL. 2. Place a container on a calibrated scale with a resolution of 0.1 grams or
better and zero the scale. 3. Place the distal end of the infusion set into a container, and place the
container on a calibrated scale with a resolution of 0.1 grams or better. Record the weight of the container.
4. Simultaneously, start a timer and press the START key. 5. Measure the weight of the container every 3 minutes ± 3 seconds for
duration of 1 hour. 6. Divide the weight by specific gravity of the solution (water’s specific gravity
is 0.998 g/mL at room temperature) and plot the results. The slope of the line is the infusion rate.
7. Divide the final weight from the total time and by the specific gravity to get the average infusion rate.
8. The solution collected should be between 116.25mL and 133.75mL. 9. If the volume of solution collected is NOT between the mentioned range
a Verify proper test technique b Check for a loose belt c Check for a properly moving backplate or damaged backplate springs d Replace the pump head assembly
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5. Results Table 1 summarizes the results of the five measurement methods performed. The raw data is included in the appendix for reference (Appendix A: Method 1 Data to Appendix D: Method 5). Rate is in mL/hr. Average measured rate is calculated by dividing the final volume value by the total time, where the slope (the measured rate) is calculated by fitting a linear line to the measured data. From here on, methods are referred to as M1 through M5 for ease of reference. Similarly, the average percent error is referred to as APE, and the slope percent error is referred to as SPE.
Table 1: Results obtained from the five accuracy tests.
M1: Weight per
Time Method
M2: Volume per Time Method
M3: Time per Volume Method
M4: VTBI Method
M5: One-‐Hour Accuracy Test
Target Rate (mL/hr)
200.0 200.0 200.0 200.0 125.0
Measured Infusion Rate (mL/hr)
Average 206.9 209.7 209.8 204.5 128
Slope 205.1 208.0 N/A N/A 127.7
The fit line for M1, M2 and M5 are shown below respectively. They are labeled as “Weight per Time” (Figure 3), “Volume per Time” (Figure 4), and “One-‐Hour Test” (Figure 5) respectively. The chi-‐squared value of .9999 (about 1) for all three methods suggests a very uniform infusion rate and a high quality data. It is important to note that M3 and M4 are single data measurements and therefore, there are no corresponding graphs for them.
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Figure 3: Weight per time test method.
Figure 4: Volume per time test method.
Figure 5: One-‐Hour Test measurement method.
y = 3.4486x -‐ 0.3963 R² = 0.99998
0
10
20
30
40
0 5 10 15
Volume (mL)
Time (min)
Weight per Time
Series1
Linear (Series1)
y = 3.4951x -‐ 0.1424 R² = 0.99995
0
5
10
15
20
25
0 2 4 6 8
Volume (mL)
Time (min)
Volume per Time
Series1
Linear (Series1)
y = 2.1332x -‐ 0.0804 R² = 1
0
50
100
150
0 20 40 60 80
Volume (mL)
Time (min)
One-‐Hour Test
Series1
Linear (Series1)
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6. Discussion According to the collected data, all methods were within the acceptable range suggested by the manufacturer (this refers to the last bullet point of each method). Comparing M1, M2 and M5, M5 percent error (% 2.2 ± .2) shows that it is the most accurate method. This also shows that the longer the infusion time, the more accurate the results would be. In addition, chi-‐squared value for all three calculated to be .9999; this shows that the data for all is of good quality and that all three methods are accurate.
Table 2: Error percentages of Method 1, 2 and 5.
M1: Weight per Time Method
M2: Volume per Time Method
M5: One-‐Hour
Accuracy Test
% Error Average (APE) 3.45 4.85 2.39
Slope (SPE) 2.54 4.00 2.20
% Error Avg of APE & SPE
3.00 ± 0.45 4.43 ± .43 2.2 ± .2
Chi-‐Squared 0.9999 0.9999 0.9999
As mentioned in the previous paragraph and as shown in Table 1, there are different targeted infusion rates for M1, M2 and M5. Therefore, the normalized percent error is used as a matric for analysis. The APE and SPE of M1, M2 and M5 are then analyzed. For M1, the average of the two approaches yields 3.00% ± 0.45%. M2 yields 4.43% ± 0.43%. M5 yields 2.20% ± 0.2%. As expected, the One-‐hour test (M5) results in a more accurate measurement of the rate, as evident by the error in APE vs SPE measurements.
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7. Factors Affecting Test Results & Accuracy In general, the following factors can influence the flow rate measurement and performance of an infusion pump: ● Air trapped in the Continu-‐Flo solution set ● Non-‐sterile fluid path ● Solution set stored in temperatures less than 15 C or more than 30 C ● Leakage or occlusion in the IV tube ● Disrupt or malfunctioned electrical connections
From the manufacturing recommendation, the resolution of the scale and the graduated cylinder need to be 0.1g and 0.2mL respectively. The scale used for this setup had a resolution of 0.01g, which has a higher resolution than the manufacture’s recommendation. The graduated cylinder, however, had a resolution of 0.2mL, which was the same as the manufacture’s recommendation. Therefore, method 1, and method 5 are better test procedures. The same infusion line was used for all five tests. The pump used a clamp for securing the infusion line, as well as stopping the infusion. As a result, the line should be moved for each test as to move the clamping location of the line. Otherwise, the clamping location can become a bottleneck which would ultimately affect the infusion rate. Due to the limitation of our resources, time and setup, this was not possible, and the line was not moved after each test.
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8. Conclusion According to the collected data, all methods were within the acceptable range suggested by the manufacturer (this refers to the last bullet point of each method). This implies that the volume to be infused of the infusion pump was measured successfully for all five methods. Method 3 & 4, however, were not used for accuracy analysis because they were single data collection. As seen in the results, the flow rate accuracy is dependent on the length of the test. Method 1 (10.5 minutes) had an experimental to target error of 3.0% ± 0.45%. Similarly, Method 2 (6 minutes) had an error of 4.43% ± 0.43%. Finally, Method 5 had an error of 2.2% ± 0.2% (60 minutes). Comparing the three methods illustrates that Method 5 is the most accurate of the three tests, and it is due its longer infusion time. Therefore, the accuracy of the infusion rate of the Baxter Flo-‐Gard 6201 is within 2.2% ± 0.2%.
9. Recommendation / Future Work The accuracy measurement for infusion rate is a very simple procedure. A digital scale that can be connected to the pump can be used to measure the weight of the solution to be collected (as done in Method 1 & Method 5). The total weight can then be fed into the pump. Using the data, the system can automatically calculate the experimented infusion rate and compare it to the target infusion rate. Using such closed system will automate the validation of the accuracy test, and could update the parameters as needed.
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10. Bibliography Chan, A. (2013). Infusion Devices. Retrieved February 2013, from UBC CHBE: ww.chbe.ubc.ca: https://courses.chbe.ubc.ca/manhat2012-‐bin/send_file?crs=BMEG/BMEG530550&id=dmmpqywl9mSaH3&user=ac8994&fname=fil_01282013100001_9QgHhZ&info=inf_01282013100001_DI86nc&attach=1&grp=4&ext=.pdf Ferrari, R., & Beech, D. R. (1995). Infusion pumps: guidelines and pitfalls. Australian Prescriber , 18, 49-‐51. MadWrench, LCC. (2011). Service Manual Flo-‐Gard 6201. Retrieved from Service Manual Flo-‐Gard 6201: http://photos.medwrench.com/equipmentManuals/3191-‐2396.pdf Mocklin, D. (2011). Infusion Pump Therapy -‐ A Guide For Clinicians and Educators. Lake Forest: Hospira. Sabah Jarjees, M. (2011). Design and Implementation of Microcontroller Based Drug Delivary System. Eng & Tech J. , 2580 -‐ 2588. Systems Integrated Medical. (2011). Operator's Manual, Flo-‐Gard 6201. Retrieved from Systems Integrated Medical, Inc.: http://www.integratedmedsys.com/customer/inmesy/manuals/Baxter-‐6201-‐Op-‐Manual.pdf Weitz & Luxenberg P.C. (n.d.). Types of Infusion. Retrieved from Weitz & Luxenberg P.C.
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Appendix A: Method 1 Data Time (minute) Weight (g) Volume (mL)
0.5 1.4 1.3972 1 3.15 3.1437 1.5 4.8 4.7904 2 6.49 6.47702 2.5 8.21 8.19358 3 9.85 9.8303 3.5 11.67 11.64666 4 13.41 13.38318 4.5 15.16 15.12968 5 16.85 16.8163 5.5 18.6 18.5628 6 20.36 20.31928 6.5 22.05 22.0059 7 23.76 23.71248 7.5 25.56 25.50888 8 27.31 27.25538 8.5 28.92 28.86216 9 30.72 30.65856 9.5 32.42 32.35516 10 34.12 34.05176 10.5 35.96 35.88808
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Appendix B: Method 2 Time (minute) Volume (mL)
0.5 1.6 1 3.4 1.5 5.1 2 6.8 2.5 8.6 3 10.4 3.5 12 4 13.8 4.5 15.6 5 17.4 5.5 19.1 6 20.8
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Appendix C: Method 3 & Method 4 Method 3 Total time to infuse 25mL = 429 seconds Method 4 Volume to be infused (Target) = 35mL Experimental volume infused = 35.79mL Time to infuse = 630 seconds
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Appendix D: Method 5 Time (minute) Weight (g) Volume (mL)
3 6.32 6.30736 6 12.72 12.69456 9 19.1 19.0618 12 25.54 25.48892 15 31.88 31.81624 18 38.46 38.38308 21 44.82 44.73036 24 51.29 51.18742 27 57.65 57.5347 30 64.15 64.0217 33 70.47 70.32906 36 76.89 76.73622 39 83.3 83.1334 42 89.69 89.51062 45 96.1 95.9078 48 102.51 102.30498 51 108.96 108.74208 54 115.37 115.13926 57 121.8 121.5564 60 128 127.744