A historical review of barrier materials

AORN Journal, Oct, 2002 by Nathan L. Belkin

In the early 1900s, the use of surgical gowns and drapes evolved as a standard of practice. (1) Just as it is today, their primary purpose was to protect sterile surgical zones from microbial invasion. Initially, the most commonly used material was muslin (ie, a relatively loosely woven, all-carded cotton, 140-thread-count fabric). It was considered suitable for this application because it was readily available, easy to work with, economical, and believed to be an effective bacteriological barrier.

In 1952, William C. Beck, MD, alerted the surgical community that although muslin may have been viewed as being an acceptable bacteriological barrier when dry, it lost that capability after it became wet, even when multiple layers were used. (2) Despite advances in textile technology, a historical review of the half-century after Dr Beck's revelation indicates that a meaningful test methodology for demonstrating a material's bacteriological effectiveness has yet to be developed.

Dr Beck's disclosure was the turning point that triggered research to develop more satisfactory materials for this unique application. The woven segment of the textile industry introduced a number of reusable materials to meet the newly established requirement of resisting the penetration of blood and aqueous liquids. Although these materials continued to be referred to as muslin and/or linen, they were not similar in construction or performance. (3) The surgical community also was introduced to a totally new category of textile products, which initially was referred to as paper. Known as nonwoven today, the material, single-use or disposable, was treated to make it waterproof, thus making it appear to possess the desirable bacterial barrier property.

DEMONSTRATING BARRIER EFFECTIVENESS

The two segments (ie, woven versus nonwoven, reusable versus disposable) of the textile industry were opposed, and the test methods each first used to demonstrate the barrier capability of its materials were quite different. For example, the nonwoven segment used a test developed by its trade association--the International Nonwoven and Disposables Association. It was called the mason jar test (Figure 1). First, a 4-inch depth of the test medium of microorganisms was placed in a jar. The jar then was inverted to challenge the material that had been affixed to the jar's opening, actually replacing its cover. The results of the test were expressed in terms of the amount of time the material was able to resist liquid penetration.

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The woven segment of the industry, on the other hand, used a test method that had been developed by the American Association of Textile Colorists and Chemists (AATCC). Identified as the AATCC 127 hydrostatic head test, it was designed to determine a rainwear fabric's water repellency capability (Figure 2). A sample of the test fabric was clamped in place horizontally on the bottom of a glass metered cylinder. Hydrostatic pressure was increased steadily by raising the height of the water column from 0 cm to a maximum level of 55 cm, which was known to exert a force of 0.75 psi on the fabric. The test was terminated when visible penetration of water droplets occurred. The water used contained no microorganisms. The results of the hydrostatic head test were expressed in terms of pressure, and the results of the mason jar test were expressed in terms of time, so the results of the two tests were not comparable.

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THE FIRST CLINICAL TEST

The literature indicates that the first test developed by a member of the clinical community for assessing the performance capability of a barrier material was introduced by Harold Laufman, MD, PhD, a surgical researcher. Dr Laufman is credited with creating the term for the phenomena of liquid penetration that has been used commonly ever since (ie, strike-through). (4)

Dr Laufman's testing device was relatively simple (Figure 3). Two pieces of the material to be tested were secured to six posts to form two hammocks. After a test liquid was poured into each hammock, a 2-kg weight was placed on top of the hammock. At 15- and 30-minute intervals, the bottom of each hammock was touched with an agar-based contact plate. Each specimen was checked for penetration in this manner four times. Although some of the new barrier materials passed the mason jar test, they did not pass Dr Laufman's liquid penetration stress test.

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THE NEED FOR A STANDARD TEST

During the period when the results of Dr Laufman's investigation were released, a number of significant events occurred. AORN stepped forward in support of the need for gowns and drapes to be made of barrier materials, and it was the first professional organization to do so. It called for barrier materials to be made of material that was resistant to blood and aqueous fluids. (5)

Shortly thereafter, the American College of Surgeons' (ACS) committee on the operating room environment (CORE) charged the textile industry with the responsibility for developing performance standards for barrier materials. In so doing, the committee cautioned that test methods used to demonstrate barrier capability should simulate "usual conditions of use." (6)