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By Nathan L. Belkin, PhD
Theneed for surgical drapes to be made of barrier-quality materials is recommendedon the basis of theoretical rationale, but it has not been supported byunbiased, statistically valid, conclusive research.
The use of surgical gowns and drapes has evolved as a standard of practice.Their primary purpose is to protect sterile surgical zones from microbialinvasion. Reusable woven fabrics had been used universally as aseptic barrierssince the turn of the century. The most popular and commonly used material wasreferred to generically as muslin (i.e., a loosely woven, all cotton, 140-thread count fabric). The material was readily obtainable, easy to work with,economical and thought to be an effective bacteriological barrier.
It was not until 1952 when Beck alerted the surgical community that whilemuslin was deemed acceptable as a bacteriological barrier when dry, it lost itseffectiveness once it became wet -- even when multiple layers were used. Areview of the literature reveals this was the turning point that triggeredresearch to develop more satisfactory materials for unique application.
One of the new products that became available was initially described aspaper. Today they are known as single-use disposables. The producers of wovenreusable materials responded to the need, igniting heated controversy betweenreusables and disposables that overshadowed the concern for patient welfare andthe possibility of these products being able to reduce the incidence of surgicalsite infections (SSIs).
The Era of Barrier Materials
Intent on examining the impact draping materials have on SSIs, the AmericanCollege of Surgeons' (ACS) Committee on the Operating Room Environment (CORE)issued a position paper challenging the textile industry to develop performancestandards for these new barrier materials. CORE cautioned that the methods fortesting and evaluating the performance capabilities of these materials shouldsimulate what they described as "usual conditions of use."
For some time, most hospitals continued to use the traditional, looselywoven, readily permeable fabrics for their surgical gowns and drapes. Lackingscientific evidence to support the implementation of the new bacteriologicalbarriers, the surgical community relied on industry's efforts to support theiruse.
Barrier Materials and SSIs
In the latest Guideline for the Prevention of SSI, the Centers for DiseaseControl and Prevention (CDC) reviewed a number of published studies in whichresearchers attempted to demonstrate whether or not the use of the newgeneration of barrier-quality materials could influence the incidence of SSIs.They concluded, "There is limited data that can be used to understand therelationship of gown and drape characteristics with SSI risk." As a result,it ranked their importance as Category 1B, which is described as "stronglyrecommended for implementation and supported by some experimental, clinical orepidemiological studies and strong theoretical rationale."
In a recent review of the same and a number of other studies dedicated to thesame objective, the authors concluded the studies "have limited relevancebecause of methodological flaws and product improvements." It should benoted that of all the studies that appear in the literature, none reportedhaving achieved a lower infection rate in clean cases than that reported inCruse's classic 10-year study in which all the gowns and drapes were made of the"usual cotton material."
Interpreting the Barrier Studies
Notwithstanding the results reported in any of the studies, detailedinformation about a number of vital factors all but prohibit theirinterpretation and a reasonable conclusion. For example:
1. Since gowns and drapes used were made of a barrier material, they failedto show whether it was the gown, the drape or the combination of the two thataccounted for the results.
2. The studies did not take into consideration the influence of other factorsdescribed by Laufman as the five "Ds": Discipline of the surgeon;design of the surgical suite; defense mechanism of the patient; drugs(prophylactic antibiotics); and a myriad of other devices used.
3. There is no information regarding the performance capability of barriereffectiveness of the materials of which the gowns and drapes were made.
Testing for Barrier Effectiveness
The introduction of the new generation of barrier materials was accompaniedby a variety of test methods, with every manufacturer using one that best suitedits purpose. As an industry, the non-woven segment ultimately adopted itsmason-jar test method that their trade association had developed. The woven,reusable manufacturers used one of several existing test methods that had beenused for rainwear fabrics.
When the publication of two studies that examined the effectiveness of someof the new materials -- one by Laufman and another by Schwartz -- disclosed thatmany of the alleged barrier materials permitted what Laufman identified asstrike-through, the industry retreated to its drawing board.
The Need for Protective Gowns
With the emergence of the era associated with the transmission of bloodbornepathogens, the surgeon's gown suddenly acquired an additional role - protectingthe members of the surgical team from the patient. Notwithstanding the need fora universally accepted test method, this also meant that whatever degree ofstrike-through may have been experienced in the past was no longer to betolerated.
It was during this period that two clinical researchers, Shadduck andNichols, working independently of one another, reported on the results of theirexamination of a variety of barrier materials. The need for a standard testmethod became evident when some of the materials found to be satisfactory underthe conditions of Shadduck's test would have failed when subjected to thechallenge of the device used by Nichols.
Not to be overlooked is the importance of the findings of the Quebbeman andTelford in-vivo evaluation of surgical gowns demonstrating the level of barrierprotection was contingent on the level of exposure, or as was later stated bythe Occupational Safety and Health Administration (OSHA)'s final standard as the"level of exposure anticipated." Thus it was reasonable to believethat whatever test method would be adopted would express a material's protectivecapability on a comparative basis.
The Level of Anticipated Exposure
With a pressing need for a test method, the American Society for TestingMaterials (ASTM) announced the development of a new mechanical device to fillthe void. Under the provisions of F1670-95, a material was first to be testedfor its resistance to liquid penetration. If it passed that test, it qualifiedto be tested for its resistance to viral penetration under the provisions ofF1960-95.
The results are reported as pass/fail rather than on a comparative basis.Furthermore, the test methodology tends to characterize a material as beingliquid-proof and/or impervious. Actually, the "pass" is predicted on afabric's ability to withstand penetration at a challenge of 2 pounds per squareinch (psi) which is contrary to what has been reported in the literature.
For example, under in-vivo conditions, Smith and Nichols reported pressuresto be as high as 2.9 psi; Telford and Quebbeman discovered gowns that had passedthe ASTM's test permitted varying amounts of strike-through; Ahman, et. al,reported experiencing penetration through gowns made of plastic laminatedmaterials; and Leonas found that a material known as having passed both of theASTM's tests failed in an in-vitro situation when tested under far less of achallenge than 2 psi.
The ASTM's tests are titled, "Standard Test Method for Resistance ofMaterials Used in Protective Clothing." Whether or not surgical drapes areto be considered as items of protective clothing is an issue unto itself.However, another question that arises is whether or not the language means thatthe maximum level of resistance to penetration for a draping material is to bethe same as that used in a surgeon's gown, namely, 2 psi. If so, it would appearthat an explanation as to how that was determined is in order.
New Questions to be Answered
What seems to have been overlooked are the variances in gowning and drapingpractices that have accompanied the advances made in surgical techniques sincethe time those studies were conducted. These may preclude the need for all gownsand drapes to be made of materials that meet the ASTM "pass"requirements. For example:
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.