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AAMI Levels and Surgical Gown
Author:By Shaozhen(Alan), Yu
Time: 2021-01-21

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    INTRODUCTION

    Prevention of disease transmission in patients and personnel has taken on greater significance today, as health-care professionals are continually challenged by new pathogens and multi-drug resistant organisms, as well as increased economic pressures to reduce healthcare-associated infections. The inherent nature of the perioperative practice setting places both patients and members of the surgical team at greater risk for exposure to infectious agents. For every surgical patient, one of the expected outcomes is that he/she is free from signs and symptoms of infection. Today, the development of a Surgical Site Infection (SSI) is a common complication and represents one of the leading causes of postoperative morbidity and mortality; SSIs also may be associated with enormous additional costs for hospitals and health-care systems. For members of the surgical team, an exposure incident can result in illness, lost wages and productivity, and increased costs of care. As a safety advocate, protecting patients and safeguarding perioperative team members from transmission of potentially infectious agents continue to be a primary focus of the perioperative nurse. The appropriate use of surgical barrier materials plays a key role in reducing the risk for disease transmission. However, because the barrier quality of surgical gowns varies, perioperative personnel must select the appropriate gown based on its planned use and anticipated exposure to blood and bodily fluids.

    RATIONALE FOR THE USE OF SURGICAL GOWNS

    Surgical gowns are an important link in the chain of prevention of disease transmission for patients and OR staff members because they serve a critically important dual purpose in the operating room. Not only do they protect the patient from microorganisms that may be shed by the patient’s own skin and by members of the surgical team, they also protect members of the surgical team from potentially infectious microorganisms that may be harbored by the patient. This is especially important in today’s era of the hazards associated with the transmission of bloodborne pathogens (eg, Human Immunodeficiency Virus [HIV], Hepatitis B and C Viruses [HBV and HCV], and Other Potentially Infectious Materials [OPIM]). Wearing surgical gowns and other apparel (eg, surgical masks, gloves) is vital because there will always be microorganisms on or in the human skin, even after conducting strict hygienic and antiseptic procedures. Microorganisms are also found on the attire of health-care workers. A study conducted on bacterial contamination of home-laundered uniforms began by culturing uniforms worn at the beginning of the shift; 39% of the uniforms identified as “clean” had one or more microorganisms (eg, vancomycin-resistant enterococci, Methicillin-resistant Staphylococcus aureus, Clostridium difficile) identified. The uniforms were tested again at the end of the shift, at which time 54% had one or more microorganisms; some that were positive at the beginning of the shift were negative at the end of the shift. In one demonstration, bacillus spores were transferred from healthcare providers’ aprons and cotton uniforms to a mock patient. The importance of barrier protection in minimizing the risk of disease transmission to the patient and staff is widely accepted and is supported by various regulations, standards, and guidelines.

    STANDARDS AND GUIDELINES

    Federal agencies and several professional organizations that have published standards and guidelines pertaining to the selection and use of surgical gowns, include:

    • Occupational Safety and Health Administration (OSHA);
    • Centers for Disease Control and Prevention (CDC);
    • United States Food and Drug Administration (FDA);
    • Association of periOperative Registered Nurses (AORN);
    • ASTM International (formerly the American Society for Testing and Materials);
    • American National Standards Institute (ANSI);
    • Association for the Advancement of Medical Instrumentation (AAMI); and
    • American Association of Textile Chemists and Colorists (AATCC).

    Each of these guidelines is described in greater detail below, with an emphasis on the AAMI/ANSI PB70 standard.

    Occupational Safety and Health Administration (OSHA)

    Because engineering and work practice controls cannot prevent all occupational exposure to blood-borne pathogens, OSHA’s blood-borne pathogens standard also requires employers to provide appropriate Personal Protective Equipment (PPE), including gowns, to workers at risk of workplace exposure to bloodborne pathogens. PPE is defined as “specialized clothing or equipment worn by an employee for protection against infectious materials.” Under the OSHA standard, personal protective equipment is considered “appropriate” only if it does not permit blood or other potentially infectious materials to pass through to or reach the employee’s work clothes, street clothes, undergarments, skin, eyes, mouth, or other mucous membranes under normal conditions of use and for the duration of time for which the protective equipment will be used. The type and characteristics of protective body clothing provided must be commensurate with the “task and degree of exposure anticipated.”

    Centers for Disease Control and Prevention (CDC)

    The CDC has provided a number of recommendations and guidelines, based on current clinical research, related to the appropriate use of protective clothing, including personal protective equipment intended to decrease transmission of blood-borne pathogens and other related infectious diseases: In the Guideline for Prevention of Surgical Site Infection, 1999 the CDC’s Hospital Infection Control Practices Advisory Committee (HICPAC) recommends, among other things, that sterile team members wear surgical gowns that are effective barriers when wet (ie, materials that resist liquid penetration). Although gowns that do not allow penetration by liquids and viruses are preferred, HICPAC recognizes that only gowns reinforced with films, coatings, or membranes appear to meet ASTM standards for barrier protection. In the 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Health-care Settings, the CDC defines Standard Precautions as a group of infection-prevention practices that apply to all patients, regardless of suspected or confirmed infection status, in any setting in which health care is delivered; it includes the use of gowns.7 The application of Standard Precautions during patient care is determined by the nature of the health-care worker and patient interaction and the extent of anticipated blood, body fluid, or pathogen exposure. For gowns, this includes during procedures and patient-care activities when contact of clothing and/or exposed skin with blood/body fluids, secretions, and excretions is anticipated.

    United States Food and Drug Administration (FDA)

    The FDA regulates surgical gowns as medical devices. Manufacturers of new or modified surgical gowns must obtain FDA clearance to market their products. As part of the premarket clearance 510(k) process, manufacturers provide data to the FDA regarding the safety and efficacy of their products. (The FDA’s Guidance on Premarket Notification [510(k)] Submissions for Surgical Gowns and Surgical Drapes8 details the information that must be provided by manufacturers.) The FDA also mandates that Good Manufacturing Practices (GMPs) must be employed in the manufacture and commercial reprocessing of surgical barrier products, and that they must be labeled in accordance with FDA requirements. Surgical gowns also are subject to the FDA’s medical device reporting requirements. The agency has ruled that strikethrough events are reportable under medical device reporting regulations if strikethrough of a gown labeled as protective (eg, repellent, resistant, liquid-proof) caused or may have contributed to a death or serious injury.

    Association of periOperative Registered Nurses (AORN)

    AORN’s mission is to support registered nurses in achieving optimal outcomes for patients undergoing operative and other invasive procedures. Every year, the Association publishes Guidelines for Perioperative Practice, which is a compilation of recommendations based on the principles of microbiology, scientific literature, research, and the opinions of experts. Each recommendation is reviewed and revised periodically. The current “Guideline for Sterile Technique” emphasize the need to evaluate product safety and performance based on the planned use (ie, the resistance to penetration by blood and other body fluids, as well as wearer preferences such as comfort) and its anticipated exposure to blood and body fluids.9 It elaborates on the need to address barrier effectiveness, resistance to tears, punctures, and abrasions; seam strength; linting; function, and flexibility, and sizing in the selection and use of surgical gowns. For surgical gowns, AORN’s current recommendations include, but are not limited to, the following recommendations and interpretive statements:

    • Prior to purchase or use, surgical gowns to be used in the perioperative setting should be evaluated for safety, efficacy, and cost.
    • Surgical gowns should be evaluated and selected for use based on: Compliance with federal, state, and local regulations as well as standards-setting bodies.
    • Environmental considerations.
    • Product-specific requirements.
    • Procedure-related requirements.
    • Patient-related.
    • End-user requirements and preferences.
    • Surgical gowns must provide a barrier and should be resistant to punctures, and abrasions.
    • The seams and points of attachments of surgical gowns should minimize penetration of liquids and the passage of potential contaminants.
    • Surgical gowns should be non-abrasive and non-toxic.
    • The barrier materials used for surgical gowns should be as lint free as possible.
    • Surgical gowns should be functional and flexible.
    • Perioperative personnel should select and use surgical gowns for a procedure according to the barrier performance class of the product as indicated on the label and the anticipated degree of exposure to blood, body fluids, and other potentially infectious materials.
    • Surgical gowns are labeled by the manufacturer with the level of performance as determined by the barrier properties of the area of the gown where direct contact with blood, body fluids, and other potentially infectious materials is most likely to occur. (This is discussed in greater detail below.)

    ASTM International (formerly the American Society for Testing and Materials)

    ASTM International is globally recognized in the development of international voluntary consensus standards.10 It establishes evaluative test methods for manufacturers as a means of measuring critical parameters for healthcare or consumer products. If appropriate, limits are established, and requirements are defined in product-specific standards. ASTM has published a number of standards pertaining to the safety and efficacy of barrier materials, many of which are described in the following pages.

    American National Standards Institute (ANSI)

    ANSI has served in its role as administrator and coordinator of the United States private sector voluntary standardization system for over 90 years. ANSI was founded in 1918 by five engineering societies and three government agencies; it remains a private, nonprofit membership organization supported by a diverse community of both public and private sector organizations. ANSI facilitates the development of American National Standards (ANS) by accrediting the procedures of standards developing organizations (SDOs). These groups work cooperatively to develop voluntary national consensus standards. Accreditation by ANSI signifies that the procedures used by the standards body in connection with the development of American National Standards meet the Institute’s essential requirements for openness, balance, consensus and due process.

    Association for the Advancement of Medical Instrumentation (AAMI)

    AAMI, a nonprofit organization founded in 1967, is a unique alliance of approximately 7,000 healthcare technology professionals united by one key mission: to support the healthcare community in the development, management, and use of safe and effective medical technology.AAMI fulfills this mission through continuing education activities; certification of healthcare technical specialists; and publication of various technical documents, periodicals, software, and books. AAMI continues to be the primary source of consensus and timely information on medical instrumentation and technology and this is the primary resource for the industry, professions, and government for both national and international standards. American

    Association of Textile Chemists and Colorists (AATCC)

    The AATCC, founded in 1921, continues to evolve to meet the needs of personnel in the ever-changing textile and materials industries.13 Today, the AATCC provides test method development, quality control materials, education, and professional networking for a global audience. AATCC is also recognized internationally for its standard methods of testing fibers and fabrics, in order to measure and evaluate various performance characteristics, including appearance, colorfastness, soil release, dimensional change, and water resistance. New and updated test methods are published annually in its technical manual.

    AAMI STANDARD FOR CLASSIFICATION OF GOWNS

    The ANSI/AAMI PB70: 2012 – Liquid Barrier Performance and Classification of Protective Apparel and Drapes Intended for Use in Health Care Facilities establishes the minimum barrier performance requirements, a classification system, and associated labeling requirements for protective apparel intended for use in health care facilities.14 It provides examples of expected use conditions and procedural applications for the selection of materials for surgical gowns based on the required level of barrier protection. As noted above, surgical gowns must be labeled from least protective to most protective by the manufacturer with the gown’s level of performance, as determined by the barrier properties of the area of the gown where direct contact with blood, body fluids, and other potentially infectious materials is most likely to occur.

    For example, short procedures during which there is little or no anticipated exposure to blood or body fluids can be completed successfully using a surgical gown with minimal barrier protection. As the complexity and length of the planned procedure increases, there may be increased potential for exposure to bloodborne pathogens, and it would be prudent to select a gown with greater barrier capability. Table 1 outlines examples of surgical/invasive procedure and the barrier performance classification levels based on the level of on the anticipated blood and body fluid exposure

    Table 1 – Relationships between Barrier Performance and Anticipated Risks of Exposure


    Table-1-671x800.png


    It should be noted that this standard does not cover:

    • protective apparel for the:
      • hands, such as surgical gloves, patient examination gloves, and other medical gloves;
      • head, face, and eyes, such as goggles, face shields, surgical caps or hoods, surgical masks, and respirators; or
      • feet, such as OR shoes, shoe covers, and surgical boots.
      • other types of protective clothing worn by health care personnel:
      • apparel that is not intended or labeled as a barrier to liquid or microorganisms (eg, surgical scrub attire, cover coats) and
      • apparel or equipment that is used when handling hazardous chemicals, chemotherapeutic agents, or hazardous wastes.
    • absorbent OR towels;
    • all of the requirements needed to ensure the safety and effectiveness of the products within the scope of the standard;
    • the interfaces between products, eg, the gown/glove interface;
    • all of the labeling or other information that a health care facility might consider necessary or desirable in product selection;
    • protection from dry particulate and dry microbial penetration;
    • manufacturing, quality assurance, or purchasing specifications;
    • criteria for evaluating experimental products;
    • guidance on the proper handling, processing, or preparing products for reuse in health care facilities; and
    • evaluation of antimicrobial properties.

    The updates to this standard are intended to tighten up what is acceptable and can be taken to market and also gives manufactures greater latitude when testing their products. Although the standard is primarily for manufacturers, health care professionals also find it helpful to understand what kind of protection they can expect to get from a particular gown. The changes to the standard focus on the acceptance criteria for a product lot, by adding what is called a rejectable quality level (RQL) to help determine if the test results are acceptable and if the product can be released. The previous version of the standard recommended that manufacturers use only an acceptable quality level (AQL) to set the criteria; now it recommends manufacturers use both AQL and RQL. RQL is defined as that level of quality that the sampling plan will accept 10% of the time; this means lots at or worse than the RQL are accepted 10 % of the time at most, or alternatively stated, they are rejected at least 90% of the time. The use of both AQL and RQL criteria provides a high probability that the consumer will only receive an unacceptable product a very small percentage of the time.

    Critical Zones

    One key to understanding the significance of the ANSI/AAMI PB70 standard is defining the critical zones of a surgical gown. The barrier requirements for surgical gowns are based on the location and degree of liquid contact expected during use. The critical zones of a surgical gown are those areas where direct contact with blood, body fluids, and OPIM is most likely to occur. The entire front of a gown (See areas A, B and C in Figure 1), including the seam and other components, is required to meet the minimum level of barrier performance (Level 1). Since the back of a gown (See area D in Figure 1) is expected to stay dry, there is no liquid barrier performance requirement for that area. The critical zone of the surgical gown is comprised of at least areas A and B. The classification of the surgical gown is based on the lower performing component of the two.

    Figure 1 – Critical Zones of Surgical Gown

    Figure-1.png


    Levels of Barrier Performance

    As previously noted, ANSI/AAMI PB70 focuses on levels of barrier protection and the impact that material construction has on barrier performance. The AAMI standard classifies the barrier performance of surgical gowns through the use of four industry standard tests:

    AATCC 42-2007. Water Resistance: Impact Penetration Test. This test measures resistance of fabrics to penetration of water by spray impact (at 1 pound per square inch [psi]), as measured by weight gain of a blotter (in grams). The results obtained with this test method depend on the water repellency of the fibers and yarns and on the construction of the fabric.

    A lower number represents higher resistance. This test method has been in use for many years; however, the blotter paper employed in this test is no longer being manufactured, although some test houses still have a supply. The standard now allows manufacturers to use a test called WSP80.3, which does not require the use of any specific paper, but instead permits the use of any blotter paper that meets the specifications in PB70. It is a similar test that should give equivalent results, giving manufacturers some degree of flexibility while maintaining the same standard.

    • AATCC 127-2008. Water Resistance: Hydrostatic Pressure Test. This test measures resistance of fabrics to penetration of water under constantly increasing hydrostatic pressure (0.25 to 2.0 psi), measured as hydrostatic resistance (cm). As in AATCC 42-2007, water resistance depends on the repellency of the fibers and yarns as well as the fabric construction. A higher number represents higher resistance.
    • ASTM F1670-08. Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Synthetic Blood.19 This test is used to evaluate the resistance of materials used in protective clothing to penetration by synthetic blood under conditions of continuous liquid contact. Pass/fail determinations are based on visual detection of synthetic blood penetration.
    • ASTM F1671-13. Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Blood-Borne Pathogens Using Phi-X174 Bacteriophage Penetration as a Test System. This test measures the resistance of materials used in protective clothing to penetration by bloodborne pathogens, using a surrogate microbe under conditions of continuous liquid contact. Results are reported on a pass/fail basis. The Phi-X174 bacteriophage was selected as the most appropriate surrogate test material because it is similar in size to HCV (the smallest blood-borne pathogen) and it has a nearly spherical morphology similar to HIV, HBV, and HCV. It also is environmentally stable, is noninfectious to humans, has a limit of detection that approaches a single virus particle, grows very rapidly (assay results can be read within as little as 8 hours), and can be cultivated to very high titers similar to HBV, the most concentrated blood-borne pathogen discussed.

    The less stringent tests used for this standard – AATCC 42 and AATCC 127 – involve the use of indirect (splash or spray) and direct contact with water according to time and pressure protocols. The more stringent tests – ASTM F1670 and F1671 – involve the use of body fluid and blood-borne pathogen simulants according to time and pressure protocols that have been found to discriminate a higher level barrier performance in the laboratory setting.

    Based on the results of these standardized tests, four levels of barrier performance are defined, with Level 1 being the lowest level of protection and Level 4 being the highest level of protection (see Figure 2), as described below and summarized in Table 2

    • Level 1 is the lowest level of protection. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in one laboratory test (AATCC 42, Water Resistance: Impact PenetrationTest).
    • Level 2 provides a slightly higher barrier protection than does Level 1. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in two laboratory tests: AATCC 42 and AATCC 127 (Water Resistance: Hydrostatic Pressure Test).
    • Level 3 provides good fluid barrier protection. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in two laboratory tests: AATCC 42 and AATCC 127. For Level 3, the test criterion for AATCC 127 performance is set at a higher value than for Level 2.
    • Level 4 provides the highest level of barrier protection in the entire critical zone, including any seams or other attachments, such as the front belt on a gown, that are in the critical zone. It describes surgical gowns and protective apparel that demonstrate the ability to resist liquid and viral penetration in the laboratory test ASTM F1671.


    Figure 2 – AAMI Levels of Barrier Performance

    Figure-2.png

    Table 2 – Barrier Performance of Surgical Gowns

    Table-2.png


    d C), including the seam and other components, is required to provide a minimum level of barrier performance (Level 1). Since the back of a gown (area D) intended for surgical applications is expected to stay dry, there is no liquid barrier performance requirement for that area. The critical zones of the surgical gown (areas A and B) can be constructed to provide increased protection (Level 2, 3, or 4). The classification of the surgical gown is based on the lower-performing component of the two

    Labeling

    ANSI/AAMI PB70 requires that each surgical gown be prominently labeled with its class of barrier performance. In addition, gowns having back panels that do not meet at least Level 1 requirements must be prominently labeled with the warning, “Back is Non-Protective.” (Users concerned about potential contact with blood, bodily fluids, or OPIM from the back should not choose gowns with non-protective backs.) Labeling the device itself is particularly important because the original outer packaging is generally not immediately available to the end-user.

    The standard also calls for each package containing a barrier product with a barrier claim to be prominently labeled with the class of barrier performance of each item contained in the package that has a barrier claim. Manufacturers also are required to provide technical literature upon request, including:

    • detailed information on the barrier performance of each critical zone component, either as a graphical representation showing the class of barrier performance of each component or a narrative description of the level of barrier performance of each component, or both.
    • detailed information on the barrier performance of each area outside the critical zone.

    Education

    Manufacturers must provide technical information and/or training for the staff on the classification system and its implications for users, as follows.

    • The manufacturer shall provide technical information and/or training explaining the barrier performance classification system and its implications for the end-user. Thereafter, the end-user is responsible for making judicious selections of products according to (a) the barrier performance class of the product, and (b) the anticipated degree of exposure of health-care personnel to blood, bodily fluids, and OPIM during a given procedure or activity.

    In particular, it is important that users understand the significance of the standardized test methods used to determine levels of protection (eg, that the tests are laboratory tests, not in-use tests). In addition, professional organizations such as AORN support the use of educational materials to aid in the adoption of products and medical devices. According to AORN’s Guidelines for Sterile Technique, perioperative staff members should receive initial and ongoing education, as well as competency validation regarding their understanding of the principles of and performance of sterile technique processes; this education may include a review of the policies and procedures related to the selection and evaluation of surgical gowns.  Reinforcement of the proper use of medical devices can aid in the judicious use of surgical gowns.

    SELECTION CRITERIA FOR SURGICAL GOWNS

    All surgical gowns are not created equal; this is an important consideration when trying to decide what level of gown is needed for a surgical or invasive procedure. The AAMI standard addresses the barrier effectiveness of surgical gowns, but OR directors, infection preventionists, safety officers, material managers, and other product committee members should consider many other attributes related to the safety and efficacy of surgical gowns, as well as other protective apparel, when choosing these products.

    The safety and performance characteristics of protective materials identified by AAMI in TIR11, Selection and Use of Protective Apparel and Surgical Drapes in Health Care Facilities are:

    • barrier effectiveness (includes resistance to liquid and microbial penetration and resistance to penetration by airborne, aerosol-borne, or dry particles);
    • abrasion resistance;
    • strength, including breaking strength and tear strength;
    • drapeability;
    • comfort;
    • flammability;
    • lint generation; and
    • toxicity

    Other factors to be taken into consideration are compliance with regulatory guidelines, efficiency, cost effectiveness, and environmental concerns. All of these considerations are described in greater detail below

    Barrier Effectiveness

    Barrier effectiveness means that, given the specific circumstances of the procedure, the gown will minimize microbial penetration. As discussed, the barrier requirements for the design and construction of surgical gowns and other protective apparel are based on the anticipated location and degree of liquid contact, given the expected conditions of use. The critical zones include those areas where direct contact with blood, bodily fluids and OPIM is most likely to occur, although areas outside of the critical zones can inadvertently be splashed or sprayed as well. This TIR covers the selection and use of protective apparel. It includes information on types of protective materials, safety and performance characteristics of protective materials, product evaluation and selection, levels of barrier performance, and care of protective apparel. Definitions of terms and informative annexes also are provided. AAMI’s TIR11 was revised in 2015 to include new information on the general relationships between barrier performance and anticipated exposure risks to assist clinicians in choosing protective apparel that is labeled in accordance with ANSI/AAMI PB70 and that is appropriate for the procedure and for the level of protection required for both patient and staff.

    In this regard, it may not be necessary for staff to wear an AAMI Level 4 gown on a laparoscopic procedure with a small amount of fluid exposure; in contrast, a surgical gown rated at an AAMI Level 3 may not provide adequate protection during, for example, colectomy procedures where the length of the procedure and fluid exposure exceeds the barrier protection levels

    Abrasion Resistance

    Surgical barrier materials should not abrade significantly during normal use, under wet or dry conditions. Abrasion may weaken the material, which may adversely affect its barrier properties, cause it to tear, or cause it to generate more lint. Abrasion that occurs through the rubbing of a material against itself or against another material is of primary concern (eg, if the arm rubs against the chest area of a gown or if the stomach area of a gown rubs against a drape on the OR table).

    Strength

    The strength of a material includes both breaking strength and tear strength. Surgical barrier materials should be resistant to tears, punctures, and fiber strains over the expected life of the product and under normal conditions of use. Three widely used tests of fabric strength are:

    • The Grab Test (ASTM D5034 – Standard Test Method for Breaking Strength and Elongation of Textile Fabrics). The grab test determines the resistance (ie, breaking force and elongation) of fabrics under an increased pulling stress. It indicates the material’s resistance to breaking when there is no initial tear in the material. A high rating on the Grab Test indicates superior performance.
    • The Diaphragm Bursting Strength Tester Method (ASTM D3786 / D3786M - 13) measures the resistance of fabrics to bursting using a hydraulic or pneumatic diaphragm bursting tester. A high rating on this test indicates superior performance.
    • The Elmendorf Tear Test (IST 100.1) measures the resistance of fabrics to tear under a controlled force. It indicates the material’s resistance to tearing when there is an initial tear in the material. A high rating on the Elmendorf Tear Test indicates superior performance.

    Drapeability

    Gowns should fit comfortably and allow freedom of movement. Drapeability can be evaluated by tests that measure the softness of a material, such as the Handle-O-Meter Test (IST 90.3),  which measures the weight necessary to push a material through a ¼-in slit. The lighter the weight needed, the more drapeable the material. The Cantilever Stiffness test is also used to measure drapeability.

    Comfort

    Surgical gowns should be comfortable and should contribute to maintaining the wearer’s body temperature. Taken in its broadest context, comfort includes psychological, physical, physiological, and environmental elements. In practice, comfort is usually defined primarily in terms of air permeability and water vapor transmission.

    In the Air Permeability Test (ASTM D73731 and IST 70.132), the rate of airflow passing perpendicularly through a known area of fabric is adjusted to obtain a prescribed air pressure differential between the two fabric surfaces. Air permeability indicates the material’s breathability and coolness during use.

    Two types of Water Vapor Transmission Rate tests are used to evaluate the breathability of a material:

    • the desiccant method, which measures the rate of water vapor movement through the specimen into a desiccant; and
    • the water method, which measures the rate of vapor movement through the specimen from a dish of distilled water. These tests are described in ASTM E9633 and IST 70.4.

    These tests measure only the air or moisture vapor permeability of small samples of barrier materials, not the thermal and evaporative resistance of multi-component clothing systems under work and environmental conditions. After determining that the product’s protective properties are appropriate for the intended application, the best assessment of overall comfort can be made by wear-testing the product during use in surgery.

    In addition to being breathable, comfortable barrier materials should be as follows.

    • The mass per unit area (ie, basis weight) of a fabric’s structure can be determined using the ASTM D3776, Standard Test Methods for Mass Per Unit Area (Weight) of Fabric. A numerical rating is appropriate.35
    • The Measuring Absorbency Time, Absorbency Capacity, and Wicking Rate test (IST 10.1) determines the volume of fluid absorbed by a fabric. 36 It indicates how much fluid a fabric can hold. The wicking rate test measures the rate at which water is absorbed into a fabric. It indicates how fast a fabric will absorb fluid. A high rating, on either of these tests, indicates superior performance.
    • Non-glare, to minimize eyestrain and distortion from reflected light.
    • Soft
    • Quiet
    • Nonirritating
    • Nonabrasive

    Flammability

    All surgical gowns, whether they are made of natural or synthetic fibers, are flammable under the right circumstances, especially in the oxygen-enriched environment of the operating room. The most basic concept in fire prevention and control is the “fire triangle,” which is the three key elements that must be present for a fire to occur: a combustible material, an ignition source, and oxygen or an oxidizer to support combustion. Most barrier materials used in surgical gowns are made of natural and/or synthetic materials that ignite and burn at various rates. Carefully choosing and handling flammable materials can help reduce the risks of ignition and fire. Fire prevention also requires safe handling of ignition sources, minimization of oxygen accumulation, and training of staff on proper actions in the event of a fire emergency.

    Lint Generation

    Some materials have a tendency to generate more lint (minute nonviable particles) than do other materials. As noted, surgical gowns should be low-linting. Lint has been reported to be a pathway for the introduction of viable organisms into the surgical site. The Gelbo Flex Test (IST 160.1) is the standard test method for measuring resistance to linting of nonwoven fabrics. It determines the relative propensity of fabrics to generate particles when continuously flexed and twisted by a particle generator. A low number on the Gelbo Flex Test indicates superior performance. The Helmke Drum Test (BS 6909) determines the cleanliness of garments by measuring the particles emitted per minute when test samples are rotated in a stainless steel drum. The test determines particle counts on wipes, instrument wraps, facemasks, and similar woven and nonwoven fabrics; the smaller the count, the cleaner the garment.

    Toxicity

    Materials used in the construction of surgical gowns should be free of toxic chemicals, non-fast dyes, noxious odors, skin irritants, or allergens. Permanently bonded chemicals or other additives are sometimes used to enhance barrier properties or stain resistance. Some of these substances may leach out; others may be non-leaching.

    Efficiency

    A number of criteria for the selection of barrier materials fall under the heading of efficiency. Packaging and folding methods, for example, have implications for ease and convenience of use. Today, many gown manufacturers are color-coding gown packaging to reflect the gown’s classification level according to AAMI/ANSI PB70 standard.

    Personnel can quickly and efficiently reach for the gown packaged in the color that corresponds to the level of protection required for the procedure.

    Ready availability of product is another consideration. Large inventories and storage space cost money. Among other things, products should be selected based on how responsive the vendor is in supplying needed items quickly without overloading storerooms. A “just-in-time” inventory may be ideal.

    Contracting with a full-line supplier provides a number of advantages, as a full-line supplier may be able to:

    • Help reduce costs by taking advantage of volume discounts;
    • Incorporate waste management into the total service package; and
    • Design custom packs for specific procedures and physician preferences.

    In addition, vendors that offer value-added programs or efficiency studies can provide valuable information to assist in the decision-making process.

    Cost-Effectiveness

    Factors to take into account when comparing the costs of different surgical gowns include initial purchase costs, storage costs, inventory costs, reprocessing costs for reusable gowns, replacement costs, and disposal costs. Choosing the right products for the right procedures makes the best use of available economic resources. For example, gowns with minimal or low barrier protection can be used very effectively for less-invasive procedures, while moderate or high barrier protection may be necessary during more fluid intensive procedures.

    Barrier products often are misused due to both a lack of product knowledge and cost-saving measures by the facility, with the most common misuse being under- or over-protection.40 This can be problematic because caregivers need adequate barrier protection and by not optimizing the level of protection, facilities spend needlessly or sacrifice protection. For example, some users perceive high barrier protection products to be warm and uncomfortable and thus opt for comfort over protection; on the other hand, some facilities are using all Level 4 gowns to provide the ultimate level of protection for their staff, which can be seen as “overkill.” Health-care facilities can best meet the needs of both staff and patients by using a mix of protection levels, based on their procedure mix. This is usually the most cost-effective option, and still provides the staff with the best combination of comfort and protection. Many facilities have found that they can standardize gowns based on the new options in materials and meet all of their needs for protection. By standardizing on fewer and smarter products, facilities can make product selection simpler and more cost effective.

    Environmental Concerns

    Gowns used in the OR are constructed of either single-use or reusable materials, which each have advantages and disadvantages. Environmental considerations that do not compromise the quality of patient care, such as the potential for reprocessing/recycling, opportunity to decrease waste, conserve resources, and reduce costs, often play a part when deciding what type of gown to use. The decision to choose disposable or reusable gowns depends on all of the criteria discussed above, as well as issues related to the availability and condition of laundry, sterilization and/or incineration facilities, storage capacity, and cost considerations. Each facility’s needs must be analyzed in detail in order to develop a cost-effective system of disposables, reusables or both. It is also important to keep in mind that the transport and disposal of waste materials must follow local, state, and federal regulations. When choosing barrier materials for use in a surgical setting, consider the incineration, processing, and/or storage capabilities of the practice setting, as well as community requirements for collecting, transporting, and disposing of waste materials. Ensure that materials used in surgical gowns are compatible with landfill and incineration requirements.

    Clinical Evaluation

    In addition to reviewing test data provided by manufacturers, users may need to conduct clinical product evaluations, particularly if comparative tests are not conclusive as to the most appropriate product for a particular use. For example, few, if any, standard tests are available for certain performance qualities and aesthetic and comfort considerations. It is recommended that health-care personnel first screen products based on material test data and then evaluate the safety and performance of selected surgical gown products under actual conditions of use. Clinical product evaluations should include as many conditions of use as possible in order to evaluate product acceptability. The gowns chosen should reflect the protective materials used in construction, the intended application, and the manner in which the product will be integrated with other protective products (eg, boots, face shields) into a complete personal protective system.

    Staff should be involved in clinical product evaluations. Rarely can department managers make product choices for successful large-scale conversions without staff involvement and input, including in-use trials. This is true because of the variety of clinical input needed and because of the psychological impact of active participation.

    Some have argued that, rather than choosing surgical gowns from the perspective of their performance on standard tests of barrier effectiveness, the materials manager should evaluate them from the perspective of their influence on the outcome of the surgical procedure (ie, the rate of SSIs). Of course, such an approach is necessarily retrospective and thus is of limited value in the initial product evaluation.

    MAKING A FINAL DECISION

    The classification system defined in ANSI/AAMI PB70 is designed primarily to assist manufacturers in testing and labeling the barrier performance of their products. While it provides common definitions for four different levels of barrier protection, it does not take into account potential variations in procedures and techniques used in different health- care facilities.

    Choosing products with the appropriate level of barrier protection will require a thorough understanding of the hierarchy of risks associated with the anticipated volume of blood, bodily fluids, and OPIMs in the type and duration of procedure or activity being performed. Ultimately, the end-user is the best judge of the barrier level required, based on experience and on known exposure risks. The end-user should choose the appropriate gown according to the:

    • barrier performance class of the product; and
    • anticipated degree of exposure of health-care personnel to blood, bodily fluids, and OPIM during a given procedure or activity.

    Within each facility, users will have to assess their own situations and make a determination of how much fluid is expected for specific procedures and surgeons and then decide the appropriate level of protection:

    • Level 1 is the lowest level of protection. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in one laboratory test (AATCC 42, Water Resistance: Impact PenetrationTest).
    • Level 2 provides a slightly higher barrier protection than does Level 1. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in two laboratory tests: AATCC 42 and AATCC 127 (Water Resistance: Hydrostatic Pressure Test).
    • Level 3 provides good fluid barrier protection. It describes surgical gowns and other protective apparel that demonstrate the ability to resist liquid penetration in two laboratory tests: AATCC 42 and AATCC 127. For Level 3, the test criterion for AATCC 127 performance is set at a higher value than for Level 2.
    • Level 4 provides the highest level of barrier protection in the entire critical zone, including any seams or other attachments, such as the front belt on a gown, that are in the critical zone. It describes surgical gowns and protective apparel that demonstrate the ability to resist liquid and viral penetration when tested according to ASTM F1671.

    The challenge with surgical barrier materials is that clinicians want both comfort and protection. Higher barrier protection fabrics can sometimes be very uncomfortable to wear for long periods of time. However, the microfiber technology used in some Level 4 gowns allows the gown to react to increasing temperature by increasing its moisture vapor transfer rate. Some Level 4 gowns are made of multi-layered, high performance fabrics.

    SUMMARY

    Surgical gowns are an important link in the chain of prevention of disease transmission for both patients and staff members. They serve a critically important dual purpose in the operating room: they are worn to reduce the incidence of healthcare-associated wound infections in patients and to prevent the exposure of personnel to pathogens in blood and other bodily fluids from the patient. In an attempt to provide barrier materials that are safe, comfortable, and cost-effective, manufacturers have developed surgical gowns designed to meet the needs of the end-user. Selection of surgical gowns based on standard selection criteria can help end-users to make appropriate choices, based on the gown’s planned used as well as the anticipated exposure to blood and bodily fluids. The revised ANSI/AAMI PB70 standard simplifies the selection of barrier products by providing examples of expected use conditions and procedural applications for surgical gowns based on the required level of barrier protection, thereby making purchasing and case picking decisions quicker and more efficient. It enables consumers to use an objective standard to select the best gown materials to satisfy the barrier requirements for specific procedures.