Comparison Study of Connector and Tubing Blow-Off Line

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1 PROCEEDINGS Comparison Study of Connetor and Tubing Blow-Off Line Pressures Jerry D. Leaf, Charles Dyson, Robert Emerson UCLA Medial Center, Department of Surgery, Division of Thorai Surgery Abstrat The purpose of this study is to ompare the blow-off pressure of a seletion of onnetors, tubing and tubing attahment tehniques urrently available for onstrution of extraorporeal iruits. Eah onnetor and tubing ombination was filled with H 2 and sealed at both ends. Hydrostati pressure was inreased, through a leur side port, until a pressure drop indiated onnetion failure. Line pressure, P.S.I., was measured with a hydrostati gauge through a seond luer side port. Blow-off line pressures were inversely proportional to onnetor and tubing diameter, and diretly proportional to tubing wall thikness. Bentley, Cobe, Gis and Shiley onnetors were ranked in aordane with blow-off line pressures generated on Bentley, Harvey and Tygon tubing. Introdution The integrity of extraorporeal iruits for ardiopulmonary bypass is dependent on the adequay of the onnetors, tubing and attahment tehniques urrently available. Clinial grade tubing and disposable onnetors are manufatured having a high degree of exellene. However, the onditions in whih these devies are used an be suboptimal, resulting in exessive stress beyond the normal operating range. A tubing lamp plaed on the arterial line during bypass, aorti ross lamp oluding the perfusion annula, inadvertent kinking of lines and high flow through small annula are examples of onditions that an lead to exessive hydrostati pressure in extraorporeal iruits. This study was undertaken to ompare some of the onnetors, tubing, and attahment tehniques available, in terms of their relative ontributions to maintaining iruit integrity in the fae of exessive hydrostati pressures. Materials Connetors made by Bentley,a Cobe,b Giese and Shileyd were seleted as representative of shallow and steep barb designs, (see Figure I). Eah type of onnetor was tested in 1 /4", 3 /8" and 1 h" sizes. Three tubing types, Bentley, Harveye and Tygonf were seleted, based on handling harateristis that indiated possible differenes in ompliane. Some Diret ommuniations to: ATTN: Jerry D. Leaf, UCLA Medial Center, Division of Thorai Surgery, Room , Bldg. MDCC, Los Angeles, CA 924 Presented at AmSECT's 19th International Conferene, Marh 1981, San Franiso, CA Revised 2/82 Aepted 3/31/82 a Bentley Laboratories, In., Irvine, CA b Cobe Laboratories, In., Lakewood, Colorado 8215 Gis Pharmaeutials, In., Santa Ana, CA 9275 d Shiley Laboratories, In., Irvine, CA e William Harvey, Santa Ana, CA 9275 r Tygon (Norton Co.), Akron, Ohio 4439 Volume 14, Number 3, 1982 The Journal of Extra-Corporeal Tehnology 385

TABLE 1 Tubing Physial Charateristis ' BENTLEY COBE GICS SHILEY Bentley Harvey Tygon Durometer Hardness 7 ± 2 71 64 Shore A 15 se. 1 se. Tensile Strength 19 16 2 PSI Ult.

2 TABLE 1 Tubing Physial Charateristis ' BENTLEY COBE GICS SHILEY Bentley Harvey Tygon Durometer Hardness 7 ± Shore A 15 se. 1 se. Tensile Strength PSI Ult. Elongation % Tear Resistane lbs.jin FIGURE I. physial properties, obtained from the manufaturers, are listed in Table 1. Eah tubing type was tested in 1 /4'', %",and 1 h" inside diameters. Both 1 fj 6 " and % 2 " wall thikness were used, exept in 1 h" I.D. where only %2" wall was tested, due to the lak of resistane to kinking in 1 /16" wall required for linial use. Two attahment tehniques for joining tubing and onnetors were tested: 'banded,' using Cobe Laboratories loking ties, atalog number ,b and tubing 'pushed on' (without additional attahment aides). Tests showed attahments with Bentley loking nuts or Travenol ement (Cat. No. 5M286),g if properly used, an withstand hydrostati pressures at or above 2 pounds per square inh (PSI), (onversion fator for onverting millimeters of merury to PSI is.193, e.g., mmhg X.193 = PSI). Due to these high blow-off pressures, they were not tested further. However, loking nuts are relatively more expensive than loking ties (bands), and differenes in onnetor and tubing materials may require individually formulated ements. In addition, when emented onnetions are disrupted, piees of tubing may break away remaining attahed to the onnetor surfae, making it diffiult to ahieve a omplete seal, even though a loking tie is plaed. Methods Three-inh long piees of tubing were ut, using sissors, and pushed onto the onnetors. The onnetors and tubing were kept dry and no lubriants were used. In every ase the tubing was advaned just beyond g Travenol Laboratories, Deerfield, IL 615 the seond barb of the onnetor, in order to standardize the attahments. When bands were used, they were plaed between the first and seond barb of the onnetor, in the normal fashion. Bands were seured using a Cobe banding gun (Cat. No ),b set for maximum pull. r PRESSURE SYRINGEff CONNECTOR ATTACHMENT RESERVOIR SYRINGE FIGURE 2. Hydrostati test platform used to determine blow-off pressures. The test speimen was onneted at the port indiated by "onnetor attahment." Water in the "reservoir syringe" was drawn into the "pressure syringe" and injeted into the system to apply hydrostati pressure to the test speimen. Final blow-off pressure, in psi, was indiated by the "pressure gauge" fitted with a peak pressure indiator. 386 The Journal of Extra-Corporeal Tehnology Volume 14, Number 3, 1982

3 -I-t 6 a... Connetor Type Mean Pressure at Blow-off N = 6 ::J a... 2 FIGURE 3. Cobe Bentley Gis Shiley All onnetors, with tubing attahed, were pakaged in peel paks and gas sterilized, to approximate the onditions to whih linial tubing paks would be subjeted. Connetotubing samples were fitted on the hydrostati test platform shown in Figure 2. The hydrostati gauge, manufatured by Ashroft,h was fatory alibrated to an auray of.7% full sale, (-2 PSI). Samples were onneted to the test platform at the point indiated in Figure 2 by "onnetor attahment." The system was filled with water from the "reservoir syringe" and a tubing lamp plaed on the open end of the tubing of the test sample. A I ml or 3 ml syringe was used as a "pressure syringe" to generate hydrostati pressure. Pressure was inreased at an even rate until a sudden drop in pressure indiated failure of the onnetion by partial or omplete blow-off. The pressure gauge is fitted with a peak pressure indiator so that the highest pressure ahieved in eah test ould be determined. All tests were done at room temperature. Eah onnetotubing-attahment ombination was repeated a minimum of five times. A total number of 6 blow-off determinations were made in the study. Data was analyzed by omputer, using an analysis of variane proedure, Dunan's Multiple Range Test for Variable Pressure. Results. Connetor types, by mean blow-off pressures, are summarized in Figure 3. Cobe was signifiantly (p h Ashroft, Stratford, Conn f- -- Q_ '- ::1 4f- f- '-... 2f- FIGURE 4. Tubing Type Mean Pressure ot Blow-off N = 6 Bentley Harvey Tygon <.5) higher than the others, 15.4% higher than Bentley, and Bentley was signifiantly (p <.5) higher, 19.2%, than Gis and Shiley. Gis and Shiley are not signifiantly different from eah other. A breakdown of all pressure data is available on request. Tubing types, by mean blow-off pressure, are summarized in Figure 4. They are all signifiantly (p <.5) different, with Bentley tubing showing the highest H... :::J... Attahment Tehniques Mean Pressure at Blow- off' 6... N=6 f- 4 - f- 2 f- FIGURE 5. f.- Banded Pushed On Volume 14, Number 3, 1982 The Journal of Extra-Corporeal Tehnology 387

4 ... ::J J) J) Connetor Size, I. D. Mean Pressure at Blow-off - H 6 4 ' FIGURE 6. - N = 6 1;4 3;8 1;2 I. D. (inh) pressure, 12.2% higher than Harvey, and Harvey, 15.9% higher than Tygon. Attahment tehniques, by mean blow-off pressure, are summarized in Figure 5. Tubing attahed with bands demonstrated a 19.4% higher blow-off pressure than pushed on. Connetor sizes, by mean blow-off pressure, are summarized in Figure 6. Differenes in blow-off pressure due to tubing wall thikness are summarized in Figure 7. These blow-off pressures in Figures 6 & 7 are expeted to follow differenes in diameter and wall thikness, as predited by stress analysis in material engineering. 1 Sine the pressure data given in these figures are summaries, the differene in onnetor design and tubing material are inorporated in the data. The inrease in blow-off pressure, due to wall thikness, is diretly proportional to wall thikness, i.e. if you inrease the wall thikness, the blow-off pressure will be inreased. An inrease in blow-off pressure due to size (diameter), is inversely proportional to diameter. Using a simplified formula to express the latter relationship, we have: PO = C P = Pressure or D =Diameter P = C/D C =Constant The onstant, C, entails the wall thikness differene in tubing material and onnetor design, sine the data in Figure 6 are means of different wall thikness, tubing material and onnetor design for large populations - 6 H (j) a... 4,._,._ a... 2 FIGURE 7. Wall Thikness (Tubing) Mean Pressure at Blow -off,... - N = Wall Thikness (inh) sorted by onnetor size only. If the data are truly representative, it should be onsistent with the relationship P = CjD, where PO= C and C = 17.5 for our series. Connetor and Measured Calulated Tubing Size Pressure( PSI) Pressure( PSI) lf4'' /s" ih" The measured vs. alulated pressures are onsistent and, therefore, onfidene in the data is justified. The different onnetor types, by size, are summarized in aordane with the respetive mean blow-off pressures, in Figure 8. In the 1 /4'' size, all types are signifiantly (p <.5) different. In terms of pressure: Cobe is 16.4% higher than Bentley; Bentley is 21.7% higher than Gis; and Gis is 12.8% higher than Shiley. In the 3 /8" size Cobe is signifiantly (p <.5) higher than the others, Bentley and Shiley are not signifiantly different from eah other, but both are signifiantly (p <.5) different from Gis. In terms of pressure: Cobe is 15.6% higher than Bentley; Shiley I I% higher than Gis. In the 1 //' size, Cobe and Bentley are not signifiantly different from eah other but are signifiantly higher than Gis and Shiley. Gis and Shiley are not signifiantly different from eah other. In terms of 388 The Journal of Extra-Corporeal Tehnology Volume 14, Number 3, 1982

... a.. 1 8 6 :J V> V> a.. C1l :::2: FIGURE 8. Connetor Type and Size Mean Pressure of Blow-off Size I.D. (inh) : pressure, Cobe, the highest, is 31.8% higher than Gis, the lowest.

5 ... a :J V> V> a.. C1l :::2: FIGURE 8. Connetor Type and Size Mean Pressure of Blow-off Size I.D. (inh) : pressure, Cobe, the highest, is 31.8% higher than Gis, the lowest. Disussion, In this study the tubing was advaned on the onnetors just beyond the seond barb, as a standard. In some of the onnetor designs, greater blow-off pressure ould no doubt be ahieved by advaning the tubing further onto the onnetor. Cobe and Shiley onnetors were the least diffiult to push the tubing on. Considerable effort was required to push on the tubing beyond the seond barb with the Gis and Bentley onnetors. Fatory assembly of tubing paks allows the manufaturer to use speialized equipment and/ or appropriate plasti ements to assist in assembly. Those of us who assemble some of our own ustom tubing iruits should seek the advie of onnetor and tubing manufaturers to insure ompatability of material and plasti ements that are so tempting to use for easy assembly. In addition, it has been suggested by some engineers that use of inompatible materials or plasti ements an ause razing* and/ or leahing of plastiizers.** "Creep" 2 is one of the engineering onepts used to desribe the behavior of polymers. Creep is related to the visoelasti properties of plastis and is affeted by temperature and duration of stress. When tubing is pushed on a onnetor the fore exerted by the onnetor against the wall of the tube auses visous flow and stress relaxation. The pratial result of reep is that even the modest heat of gas sterilization and aeration ause plasti tubing to onform to the shape of the onnetor, and loking ties seem to loosen as the ompressive fore is relieved by visous flow of the tubing. The same phenomena will our over a longer period of time at room temperature. In a omparison of freshly assembled, unsterilized onnetor /tubing samples to gas sterilized samples, the latter had a lower blow-off pressure. The idea that it is safe to use modern onnetors for the arterial annula without the use of loking ties is quite orret. 3 This is partly due to the lak of the effet of reep on the freshly assembled onnetion. Cannula onnetions on long-term membrane support iruits may find the effet of reep requires some loking devies for safety, if they are not already universally used. Normal arterial line pressures experiened with proper annula seletion for required flow rates an keep line pressure below 1 PSI. 4 Abnormal onditions ausing exessive line pressure an exeed the blow-off pressure of most onnetor /tubing iruit designs. The onnetors in this study show some differenes in design with resulting differenes in line pressure. However, they were all satisfatory for normal operating onditions. The tubing wall thikness for eah tubing type was measured and found to be the same from one type to another for eah wall thikness. It is not obvious why there were the observed differenes in blow-off pressure for onnetor and tubing types. Evidently the small differenes in maximum diameter for onnetors, and tubing formulation differenes for tubing, were responsible. Additional information on the physial harateristis of the produts tested here, in the produt literature, would be helpful if high stress iruits need to be designed. Creep modulus*** and Young's modulust for tubing and fatory tested blow-off pressures are examples of information we would onsider desirable. * A raze is a region of material permanently deformed. The deformation an redue material density 5%. The razing seen in onnetors has the appearane of spider web-like fratures at the surfae. ** Plastiizers are low moleular weight polymers used in thermoplastis to make them more pliable. *** Creep modulus is the fore per unit area to produe a plasti, i.e. permanent, strain per unit length in a given time at a given temperature. t Young's modulus is the fore per unit area to produe an elasti, i.e. reversible, strain per unit length at a given temperature. Volume 14, Number 3, 1982 The Journal of Extra-Corporeal Tehnology 389

6 Conlusions Current onnetor designs are more than adequate for normal ardiopulmonary bypass line pressures and will maintain iruit integrity. Only suboptimal onditions due to obstrution of normal flow will result in failure. It is reommended that some form of tie or loking nut be used for tubing onnetions, due to the effets of reep that our with exposure to moderate temperature and extended storage time. If plasti ements are used for assembly of tubing iruits, the manufaturer of eah produt used should be onsulted. Aknowledgments We would like to thank Shiley Laboratories for their assistane and advie in preparing to do this study. The blow-off tehnique used in our study was suggested by their engineering staff. Speial thanks to Daniel R. Johnston, manager of the engineering Laboratory at Shiley Sientifi. Referenes I. Elements of the Mehanial Behavior of Solids, N. P. Suh and A. L. Turner, MGraw Hill, Book Co., New York, Ibid, p Cardiopulmonary Perfusion, C. Reed and D. Clark, Texas Medial Press, In., Houston, Texas, 1975, Heart-Lung Bypass, Priniples and Tehniques of Extraorporeal Cirulation, P. M. Galletti, G. A. Breher, Grune & Stratton, New York, The Journal of Extra-Corporeal Tehnology Volume 14, Number 3, 1982

Mechanical Properties of High-Strength Concrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2

Mechanical Properties of High-Strength Concrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2 1.1 Introdution Mehanial Properties of High-Strength Conrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2 Mehanial properties of High-Strength Conrete (HSC) an be divided in two groups as shortterm