Covid 19 | Research/ Review Paper | Textile Articles

TESTING THE QUALITY OF SURGICAL GOWNS

Published: July 27, 2020

Author: TEXTILE VALUE CHAIN

Abstract: A surgical gown is a personal protective garment intended to be worn by health care personnel during surgical procedures to protect both the patient and health care personnel from the transfer of microorganisms, body fluids, and particulate matter. A surgical gown is a class 2 medical textile used to reduce the transfer of bacteria from the skin of the surgical staff to the air in the operating room, as well to protect the surgical staff from contact with bodily fluids. Gowns are most often constructed from fibers such as polypropylene and polyester, by using a nonwoven technique. These fibers are relatively to cheap to make but produce a high quality product. Typically, a gown uses the nonwoven technique known as SMS which stands for spun bond, melt blown, spun bond. In some cases the SMS process can include more than one melt blown layer between the outer spun bond layers. This article discuss the testing procedures for surgical gowns and the various standards to assess the performance of the surgical gowns.

Introduction

Because of the controlled nature of surgical procedures, critical zones of protection have been described by national standards. As referenced in Figure 1: the critical zones include the front of the body from top of shoulders to knees and the arms from the wrist cuff to above the elbow. Surgical gowns can be used for any risk level (Levels 1-4). All surgical gowns must be labeled as a surgical gown.

The entire front of the gown (areas A, B, and C) is required to have a barrier performance of at least level 1.
The critical zone compromises at least areas A and B.
The back of the surgical gown (area D) may be nonprotective.

Classification of Protection Level

Surgical gowns can be separated into four different categories based on protection level. This system of classification for protective apparel used in healthcare settings is based on liquid barrier performance. There are four tests that are performed: Spray Impact Penetration Test; Hydrostatic Head Test. The Spray Impact Test determines if the product is protective or nonproductive. The Hydrostatic Pressure Test result determines the level of protection, ranging from 1 to 4.

Level 1: Minimal risk, to be used, for example, during basic care, standard isolation, cover gown for visitors, or in a standard medical unit
Level 2: Low risk, to be used, for example, during blood draw, suturing, in the Intensive Care Unit (ICU), or a pathology lab
Level 3: Moderate risk, to be used, for example, during arterial blood draw, inserting an Intravenous (IV) line, in the Emergency Room, or for trauma cases
Level 4: High risk, to be used, for example, during long, fluid intense procedures, surgery, when pathogen resistance is needed or infectious diseases are suspected (non-airborne)

Within each category, there are standardized test methods and minimum performance levels for protective gowns.

Level 1: During impact penetration tests, critical zone components must have a blotter weight gain of 4.5 g or less.
Level 2: During impact penetration and hydrostatic pressure tests , critical zone components must have a blotter weight gain of 1.0 g or less, and a minimum hydrostatic resistance of 20 cm.
Level 3: For impact penetration and hydrostatic pressure tests, critical zone components must have a blotter weight gain of 1.0 g or less and a minimum hydrostatic resistance of 50 cm.
Level 4: When tested for resistance to Bacteriophage Phi-X174, critical zone components are required to show an AQL of 4%.

Testing Standards For Surgical Gowns

The performance of gowns is tested using the following standards:

American Society for Testing and Materials (ASTM) F2407 recognized by the FDA describes testing for surgical gowns: tear resistance, seam strength, lint generation, evaporative resistance, and water vapor transmission.

Tensile Strength: ASTM D5034, ASTM D1682
Tear resistance: ASTM D5587(woven), ASTM D5587 (nonwoven), ASTM D1424
Seam Strength: ASTM D751 (stretch woven or knit)
Lint Generation (ISO 9073 Part 10)
Water vapor transmission (breathability) ASTM F1868 Part B, ASTM D6701 (nonwoven), ASTM D737-75

American National Standards Institute (ANSI) and the Association of the Advancement of Medical Instrumentation (AAMI): ANSI/AAMI PB70:2003 describes liquid barrier performance and classification of protective apparel and drapes intended for use in health care facilities.Below is a table summarizing the ANSI/AAMI PB70:2012 standard recognized by the FDA.

AATCC 42 This test is called the “Water resistance: Impact Penetration Test.” It indicates how the fabric will resist strikethrough when fluids splash or spray onto the fabric.

AATCC 127 This test is called the “Water resistance: Hydrostatic Pressure Test”. It indicates how the fabric will resist strikethrough when water pressure is applied to the surface of the fabric.

Liquid Barrier Performance

Classifies a gown’s ability to act as a barrier to penetration by liquids or liquid-borne pathogens based on four levels. The critical protective zones for surgical and non-surgical gowns are defined differently by the standard. While the critical zones designate different protective areas for the different gowns, the levels of protection are the same for both surgical and non-surgical gowns. Liquid barrier performance is not related to the strength of the material.Within that standard, AAMI has identified AATCC (American Association of Textile Chemists and Colorists) 42 and AATCC 127 as the key test requirements that a surgical gown must pass in order to be labeled AAMI Level 3.

Fluid And Bacteriophage Barrier (ASTM 1671) Measures resistance of materials used in protective clothing to bloodborne pathogens using viral penetration at 2psi and ambient pressure

Hydrostatic Pressure Test (AATCC 127) Tests for fluid resistance by measuring the force required for water to penetrate a fabric (including seams).

Gelbo Lint Test Determines the relative number of lint particles released from a fabric.

Martindale Abrasion Test (ASTM D4966) A visual test of the abrasion resistance of fabric using a standard abrasive surface and a specified force to assess barrier/fabric integrity and lint production.

Laser And Ignition Resistance (ISO 11810) Used to assess the laser-induced flammability properties of gown fabrics, in the oxygen-rich environment of the OR. Includes front and back panels and sleeves. cpsc standard for the flammability of clothing textiles measures a fabric’s burn rate.

Bacterial Filtration Efficiency (BFE): Bacterial Filtration Efficiency (BFE) measures the filtration effectiveness of materials when challenged with a biological aerosol of Staphylococcus aureus or other organisms. Items such as face masks, surgical and isolation gowns, and other barrier materials can be tested. Known quantities of the challenge agent are applied, under positive air pressure, to the surface. Organisms migrating through the fabric are measured as a percentage of the original sample.

The standards established by AAMI (The Association for the Advancement of Medical Instrumentation). Specifically, ANSI (American National Standards Institute)/AAMI PB70:2012 is the standard that establishes a classification system (Levels 1-4) for protective apparel used in health care facilities, including surgical gowns, based on liquid barrier performance using standardized test methods. The U.S. Food and Drug Administration (FDA) have adopted ANSI/ AAMI PB70:2012 as the standard by which all surgical gown manufacturers must abide.

Table 1 Protection level and its application

Conclusions

The use of surgical gowns and drapes dates back from a century. Their primary purpose was to protect the sterile surgical zones from microbial invasion. Most of the items were made of a loosely woven, readily permeable, reusable fabric generically known as muslin. Surgical gowns with impermeable areas and edges will block the transfer of bacteria, viruses, infections, blood borne pathogens, and other harmful agents and chemicals to and from the patient. Surgical gowns are widely considered to be the foremost item of protective equipment today..Surgical gowns are worn by doctors and nurses in the operating theater to perform a dual function of preventing transfer of microorganisms and body fluids from the operating staff to the patient, and also from patient to staff.

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