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By Nathan L. Belkin, PhD
How it All Began
From the time that an operating room gown first became a part of the surgeonsarmamentarium, its primary purpose was to protect the patient from the membersof the surgical team. In that capacity, the garment was made of a relativelyloosely woven, readily permeable, all carded cotton type 140 (thread count)material generically known as muslin. The material fulfilled the essentialrequirement of the application, in that it was considered effective in terms ofproviding what was believed to be a satisfactory aseptic barrier, was readilyavailable, and was economical to use.
Then in 1952, the surgical community was alerted to the fact that althoughthe muslin material may have been considered an effective bacterialogicalbarrier when it was dry, it lost its barrier capabilities once it became wet even when multiple layers were used.1
The Need for a Liquid Barrier
This disclosure encouraged the textile industry to develop more satisfactorymaterials for this unique application. In responding to the challenge, bothsegments of the industry the nonwoven disposable and woven reusable introduced a new generation of fabrics. Whereas both made claims about theirperformance capabilities, there was no similarity to the tests upon which thoseclaims were predicated.
In the meantime, the American College of Surgeons (ACS) Committee on theOperating Room Environment (CORE) charged the entire textile industry with theresponsibility to develop a test method that had the capability to simulate thestresses that they astutely described as usual conditions of use.2
Not being able to either correlate the results of the tests being used byindustry or consider them as simulating usual conditions of use, a distinguishedsurgical researcher not only developed a test method but introduced the term forthe phenomena of liquid penetration that has been commonly used ever since: strikethrough. The published results of his study indicated that someof the nonwoven materials that had passed their Mason jar test proved to betotally ineffective, and that some were moderately effective. However, includedwith the number that performed quite well was one woven reusable.3 Be that as itmay, it was these findings that supported the researchers appeal to theSurgical Device Classification Panel of the Food and Drug Administration (FDA)sBureau of Medical Devices for classification of aseptic barrier materials forsurgical gowns and drapes as Class II medical devices: high priority, that is,those in need of performance standards.4
One response to the FDA classification process has been the development ofvoluntary standards, user guidelines, and recommended practices by cooperativeworking groups comprised of representatives from the clinical community, otherhealthcare professionals, and industry. Thus it was that representatives fromthe three groups formed an ad hoc committee to address the issue.
Subsequently, the group was formally organized under the auspices of theAssociation for the Advancement of Medical Instrumentation (AAMI) and identifiedas the Committee on Aseptic Barriers. Unfortunately, because of a lack ofconsensus among its members, the Committee was disbanded and the task abandoned in May 1983.6
The Emergence of HIV
With the emergence of the era of the hazards associated with the transmissionof bloodborne pathogens, the primary purpose of the surgical gown suddenlychanged from third person to first person to protect the surgeon from thepatient. This also meant that whatever degree of strikethrough may have beentolerated in the past was no longer acceptable.
It was during this period that two clinical researchers,7-8 workingindependently of one another, reported on the barrier effectiveness of a varietyof products that were on the market. What exemplified the need for a standardtest method was the fact that some of the materials that had been found to besatisfactory under the conditions of one of the tests would have failed whensubjected to the challenge of the other test that had been especially designed for this purpose. What isparticularly noteworthy is that the results of the less challenging testreported detecting penetration of human immunodeficiency virus (HIV) throughplastic-reinforced materials in which strikethrough was not visible.
Nevertheless, the results of these studies exemplified the need for ameaningful test method that could be adopted by both the clinical community andindustry for use in assessing a materials barrier capability. It was alsoreasonable to assume that whatever test method would be developed would measurea materials ability to resist liquid penetration at various levels.9 Ratingthe materials in this manner would be in accord with the results of acomprehensive in vivo study specifically designed for that purpose. 10 More importantly, it would facilitate the selection process mandated by the Occupational Safety and Health Administration (OSHA)sfinal rule that the garments be appropriate for the task and degree of exposure anticipated. 11
The Development of New Tests
With the pressing need for a test method, an industry-driven committee of theAmerican Society for Testing Materials (ASTM) released a modification of one ofits existing mechanical devices that had originally been developed fordetermining the effectiveness of protective clothing worn by chemical workers.The group incorporated the methodology in two tests; one for liquid penetrationand one for viral penetration. Both methods were first adopted as emergencystandards and subsequently adopted as regular standards in 1995.
However, rather than the results of either of the tests being reported on acomparative basis, they were identified as pass/fail, with a passpredicated on the materials ability to resist penetration at a level of 2pounds per square inch (psi). In responding to how that level of resistance wasselected, the tests developer and chairman of the ASIMs committee advisedthat it had a high correlation to the manual elbow-lean test (simple andmanually executed) that had been used by one of its member manufacturers to demonstrate its materials effectiveness).14
It should be noted that prior to the ASTMs adoption of the test methods,several reports had been published in the clinical literature that indicatedthat the pressure exerted on surgical gowns and drapes in both in vivo and invitro circumstances had been found to be far in excess of 2 psi.15-17 Asobserved by one of the researchers, Because conditions of use are known tovary greatly by type of procedure and task, all materials do not need to havethe same level of resistance, yet the ASTM tests subject all to a single method.18
Notwithstanding the ASTMs noble mission to help reduce the risk ofoccupational exposure to bloodborne pathogens, the fact of the matter is thatthe healthcare delivery system is financially strained at an unprecedented leveland is being pressured to not only contain costs, but reduce them. Under thesecircumstances, to indiscriminately provide all healthcare workers with what theindustry group believes to be the maximum level of protection would be neitherprudent nor fiscally responsible. All things considered, it appears that theASTMs tests may have been developed for the benefit of its industry committeerather than for the benefit of the surgical community and can only be viewed asbeing blatantly self-serving and morally irresponsible.
The New Standard
The American National Standards Institute (ANSI) has recently published adocument which is said to provide a solution to this half-century need.19 TitledLiquid Barrier Performance and Classification of Protective Apparel andDrapes Intended for Use in Healthcare Facilities,20 it has been adopted bythe FDA and is considered to satisfy the agencys need for performancerequirements for those Class II medical devices
The standard establishes the useof four different test methods and two different liquids to classify thedifferences in the levels of a materials barrier performance.
To accommodate the need for determining a materials barrier performancefor the duration and level of anticipated exposure, AAMIs Protective Barrier Committee selected two other tests, the AmericanAssociation of Textile Chemists and Colorists (AATCC) #42-2000 water impactpenetration test and their #127 hydrostatic test for that purpose. (Itshould be noted that this same AAMI group had several years earlier maintainedthat neither of the two tests were suitable for use for this purpose.21
Thus the new standard establishes four levels of barrier effectiveness. For Level 1, the lowest of the four, the AATCCs 42-2000 water impactpenetration test is used. (See Figure 1.) The materials capability to resistpenetration is determined by being challenged by a fixed amount of water sprayedon it while being held at a 45-degree angle. An absorbent blotter affixed underthe fabric is then weighed to ascertain its weight gain. According to thestandard, the blotter should not have gained more than 45 grams to be considereda Level 1 fabric.
For Level 2 fabrics, there are two tests that can be used. One is the sametest used for Level I except that the weight gain of the blotter can be no morethan 1 gram. An alternate test is the AATCCs 127-1996 hydrostatic head test.(See Figure 2.) A sample of the fabric is clamped horizontally on the bottom ofa metered glass cylinder. The hydrostatic pressure is steadily increased as theheight of the water in the cylinder is raised. To be acceptable for a Level 2barrier, it must resist penetration of water when it reaches a height of 20centimeters.
For Level 3 fabrics, both of the AATCC tests may be used. However, for the impact penetration test, the weight gain of the blotter isagain 1 gram. For the hydrostatic head test, the water level in the cylindermust be at least 50 centimeters. For level 4 fabrics, the ASTMs mechanical device is used for both. Forsurgical gowns, the material must pass their F-1671 test for viral penetration;surgical drapes need only pass the F-1670 for resistance to penetration tosynthetic blood. The test sample is mounted in a vertical position onto a cellthat separates the challenge and a viewing port. The time and pressure protocolsspecify atmospheric pressure for five minutes, 2 pounds of pressure psi for oneminute, and atmospheric pressure for 54 minutes. The test is terminated ifvisible penetration occurs before or after 60 minutes.
(It should be noted that the standard makes no mention of the level ofprotection that a pass provides, i.e., 2 psi.)
Interpreting the Results
For Levels 1, 2, and 3, the results of the water impact penetration test muststand on their own merit since there is no known method of correlating theweight of the blotter to the level of pressure exerted on it.
For the hydrostatic pressure test used for Levels 2 and 3, the correlationbetween the height (in centimeters) of water and the level of pressure is known.For Level 2, the equivalent of pounds psi at 20 cm is 0.20; when the level ofwater is raised to 50 cm, the psi is 0.73.
The question that logically arises is how the barrier effectiveness of amaterial that is awarded a pass (at 2 psi) when tested with the ASTMsdevice can reasonably be compared to the psi of the Levels 2 and 3?Unfortunately, they cannot be. The culprit? Surface tension.
The Role of Surface Tension
As defined in the document, surface tension is the intermolecular forcesacting on the molecules at the free surface of a liquid. Surface tension affects the degree to which a liquid can wet a material(i.e., the lower surface tension, the more easily the liquid wets a materialssurface). Surface tension is measured by a unit of dynes per centimeter.
Whereas water used in both of the AATCC tests measures around 72 dynes/cm,blood is around 42 dynes/cm. (It is viscosity that makes blood thicker thanwater.) This means that liquids, such as blood, which have a low surfacetension, can penetrate fabrics more readily than those with a higher surfacetension such as water. Thus, in terms of interpreting the results of the testsfor Levels 1, 2, and 3, they do not mean that under actual conditions of use,they would not permit the penetration of blood.
Leakage in the Critical Zone
The ANSI/AAMI standard defines the critical zone as an area of protectiveapparel or surgical drape where direct contact with blood, body fluids, andotherwise potentially infectious material (OPIM) is most likely to occur.23
One of those areas of the surgical gown, in which leakage at the gown/gloveinterface was first reported in 1975.24 Some 20 years later, in a multi-center study of blood contacts in 8,502 surgicalprocedures, it was found that of the total of 1,043 contacts, 60 percent wereexperienced by surgeons, and that 53 percent of those involved the fingers,hands, and arms.25 (It is interesting to note that only 2 percent were on thebody.) A recent report on this danger zone included a proposed solution to thisproblem area that has yet to be pursued commercially in a wide fashion.26-27 Nevertheless, it now appears in the list of exclusions as one of the items that the standard does not cover.
In response to an inquiry of the FDA about the exclusion, the agency advisedthat AAMIs Barrier Committee excluded this subject because the standard isfor the barrier properties of the gowns and drapes, especially the criticalzone, and it is not possible to determine how an individual would select a gownthat assured there would no be a potential problem with this interface.29
In the interim, until such time as some changes in the design andconstruction of this area, the protective capability of the surgeon gown,regardless of the material of which it is made, will continue to be compromised.
It is to be noted that the standard classifies the patient drape as an itemof protective clothing. In so doing, it calls for the inclusion of abarrier-quality material in the critical zone. As recently stated, the influenceof a barrier material on the incidence of surgical site infections has not beenassessed by scientific studies.30 This confirms the statement made on their usemore than 20 years ago. In a commentary on the factors that must be consideredthat can influence post-operative wound infection, the author stated that thereis no convincing evidence for all of them; one of which was barrier materials.Thus, he concluded that their use was predicated on anecdotal experience andcommercial interests rather than scientific studies.31
Not to be overlooked is the fact that the authors of the standard failed toconsider the widespread use of incise drapes and the advent of minimallyinvasive surgical procedures that preclude the need of the protective capabilityof a costly barrier material.
Nathan L. Belkin, PhD, retired in 1991 following a 40-year career in thehealthcare industry. He is the author of more than 100 articles and consultedwith a variety of healthcare organizations including APIC and AORN.
1. Beck, W.C. and Collette, T.A. False faith in the surgeons gown andsurgical drape. Ann Surg. 85:125-126. 1952.
2. Bernard, H.R. and Beck, H.C. Operating room barriers: idealism, practicality, and the future. Bulletin ofthe American College of Surgeons. 60(9):16.1975.
3. Laufman, H.A., Eudy, W.W., and Vandervoot, A.M. Strikethrough of moistcontamination by woven arid nonwoven surgical materials. Ann Surgery.181:857- 862. 1978.
4. Laufman, H. Breach of truth in advertising regulations. Read before theSurgical Device Classification Panel of the Device Agency, Food and DrugAdministration. 1978.
5. Belkin N.L. Textiles as aseptic barriers: the past, present and future. Medical Instrumentation. 14:233-8. 1980.
6. Beck, W.C. and Meeker, M.H. Demise of aseptic barrier committee: successand failure. AORN Journal. 38:384-8. 1983.
7. Shadduck, P.D., Tyler, D.S., Lyerly, H.X., et al. Commercially availablesurgical gowns do not prevent penetration of HIV-1. Surgical Forum.41:77-80. 1990.
8. Smith, J.C. and Nichols, R.J. Barrier efficacy of surgical gowns. ArchSur. 26:756-761. 1991.
9. Belkin, N.L. Gowns: selection on a procedure- driven basis. InfectionControl Hosp Epidemiology. 15(11):713-716. 1994.
10. Quebbemen, E.J. and Telford G.L., et al. In-use evaluation of surgicalgowns. Surgery Gynecology and Obstetrics. 174:369-375. 1992.
11. Occupational Exposure to bloodborne pathogens: final rule. FederalRegister 56. Dec. 6, 1991. 64040-64182.
12. ASTM. Standard test method for resistance of materials used in protectiveclothing to penetration of synthetic blood. F1670-95.
13. ASTM. Standard test method for resistance of materials used in protectiveclothing to penetration by bloodborne pathogens using Phi-X174 bacteriophagepenetration as a test system. F1671-97b.
14. Stull, O.J. Response. OR Reports 2. July/August 1993.
15. Altman, K.W., et al. Transmural surgical gown pressure measurements inthe operating theatre. Am J Infection Control 19. June 1991. 147-155.
16. Smith, J.W., et al. Determination of surgeon-generated gown pressuresduring various surgical procedures in the operating room. Am J InfectionControl 23. August 1993. 237-246.
17. Telford, G.L. and Quebbeman, E.J. Assessing the risk of blood exposure in the operating room. Am J InfectionControl 2. December 1993. 351-356.
18. Nichols, R.L. The operating Room. Hospital Infections, fourth edition. Chapter 27. Lippincott-Raven Publishers. Philadelphia. 1998.
19. Koch, F. Perspectives on barrier material standards for operating rooms. AmJ Infection Control. April 2004. 115-117.
20. ANSI/AAMI PB 70:2003. Liquid barrier performance and classification ofprotective apparel and drapes intended for use in healthcare facilities. 2003.
21. AAMI. Technical Information Report. Selection of surgical gowns and drapes in healthcare facilities. AAMI TIR 11.1994.
22. Ibid. 20. Page 4 (3.2B).
23. Ibid. 20. Page 2 (3.9).
24. Ibid. 3.
25. White, M.C. and Lynch, P. Blood contact and exposure among operating roompersonnel, a multi-center study. Am J Infection Control. 1993.21:243-248.
26. Meyer, K.K. and Beck, W.C. Gown/glove interfaces: a possible solution to the danger zone. ICHE 16.August 1995. 488-490.
27. Ibid. 20. Page 1.
28. Ibid. 3.
29. Personal communication with C.S. Lin, Office of Device Evaluation, FDA. Oct. 5, 2004.
30. Rutala, W.A. and Weber, D.J. A review of single-use and reusable gownsand drapes in healthcare. ICHE 2001. 22:248-257.
31. Nichols, R.L. Postoperative wound infection. New England Journal ofMedicine. 1982. 307:21:1701-2.