key: cord-259279-8dspud40
authors: Kahveci, Zafer; Kilinc-Balci, F. Selcen; Yorio, Patrick L.
title: Barrier Resistance of Double Layer Isolation Gowns
date: 2020-10-17
journal: Am J Infect Control
DOI: 10.1016/j.ajic.2020.09.017
sha: 
doc_id: 259279
cord_uid: 8dspud40

Isolation gowns are one of the crucial pieces of personal protective equipment (PPE) to prevent the migration of microorganisms and body fluids from patients to healthcare personnel and vice versa. Underperforming isolation gowns in terms of fluid resistance, could potentially put lives in danger. Wearing multiple layers of isolation gowns could theoretically increase the fluid penetration resistance. Extraordinary circumstances such as epidemics/pandemics and product recalls, bring extra burden on the health institutions in terms of PPE availability. Thus, shortages could occur, and PPE that provides an appropriate level of protection might not be available. Therefore, wearing multiple layers of lower barrier level gowns could be assumed as a solution. This study investigates if two-layer lower barrier level isolation gowns meet the barrier effectiveness requirements of a single higher barrier level isolation gown. Three ANSI/AAMI PB70 Level 2 isolation gowns were tested based on the ANSI/AAMI PB70 standard, in single and double-layer configuration. Test results demonstrated that the double layer isolation gown configuration does not always provide equal fluid resistance as the higher level of isolation gown according to results from the AATCC 42 and AATCC 127 standard test methods, which are described in ANSI/AAMI PB70.

As of April 9, 2020, the coronavirus disease 2019 (COVID-19) pandemic had resulted in 9,282 HCP infections, and among those 27 deaths, in the US alone (1). Significant efforts have been employed to develop new materials and manufacturing techniques to meet consumers' design needs and improve barrier protection in recent years. Isolation gowns are one of the main pieces of PPE for protecting HCP, patients, and visitors from infectious pathogens. There are many types of isolation gowns in the marketplace which offer varying barrier resistance to blood or other body fluids. Isolation gowns are generally classified as disposable or reusable, however mainly disposable gowns are used in the U.S. healthcare in contrast to Europe (2) . The building materials and design of the isolation gowns determine the barrier effectiveness. Disposable isolation gowns are typically constructed of nonwoven materials, which are made of a wide range of synthetic fibers or in combination with other materials such as plastic films (3). The ANSI/AAMI PB70 (4) standard is currently used to classify gowns according to the liquid barrier performance. The AAMI PB70 standard includes four standard tests to evaluate the barrier effectiveness of surgical gowns and isolation gowns. 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 (Table 1 ). The requirements for the design and construction of surgical and isolation gowns are based on the anticipated location and degree of liquid contact, given the expected conditions of use. ANSI/AAMI PB70 identifies certain areas of isolation gowns as critical zones. The critical zones include those areas where direct contact with blood, body fluids, and/or other potentially infectious materials is most likely to occur. According to the standard, for isolation gowns the whole garment is considered a critical zone which includes the seams, but excludes the cuffs, hems, and bindings (3).

AAMI TIR 11 is a technical guidance that provides considerations for selecting the protection level of PPE based on the anticipated exposure to potentially infectious fluids (5) . Some of the factors important to assessing the risk of exposure in healthcare facilities include source, modes of transmission, pressures and types of contact, and duration and type of tasks. According to the guidance, level 1 to 3 gowns could be used when minimal to moderate fluid exposures are expected such as, simple biopsies, ear, nose, and throat procedures, as well as mastectomies, gastrointestinal, arthroscopic orthopedic, and endoscopic urological procedures. Thus, identifying the expected fluid amount and duration of exposure has great importance when selecting the appropriate gown.

Although, selection of an appropriate gown depends on anticipated fluid exposure, it may be based on the availability of a gown at the specific level of protection within the healthcare institution. During times of pandemics or product recalls, PPE shortages could occur (6) (7) (8) . When gowns with higher levels of protection are not available, HCP may resort to wearing gowns with lower levels of protection. This study aims to investigate if wearing a double layer of lower level There are several studies that show benefits of double-gloving, as demonstrated by Guo et al.

where they provided evidence of advantages of using double layer glove configuration compared to single layer (9) . In addition, previous National Institute for Occupational Safety and Health (NIOSH) research showed the benefit of double gloving in terms of gown-glove interface barrier efficacy (11) . Although double-gloving is not directly related to wearing multiple layer gowns, since generally double-gloving is considered advantageous if a puncture or imperfection potentially occurs or exists in the first layer, where both layers of gloves are expected to be impervious to fluid, it is worth to mention, because double-gloving could be thought as an evidence-based justification for wearing multiple layer isolation gowns.

An experimental laboratory study was designed to investigate the impact of double layer gown configuration on the fluid resistance provided by the system using isolation gowns. Three commonly used (labeled as A, B, and C) ANSI/AAMI Level 2 isolation gown models were selected and tested in single layer and double layer configurations in accordance with ANSI/AAMI PB70 requirements. ANSI/AAMI PB70 requires testing the gown critical zones using AATCC 42 (12) and AATCC 127(13) standard test methods. All of the gown models had a medium weight multilayer nonwoven fabric design and heat-sealed seams. Some of the other specifications of the gowns are listed in the Table 2 .

The AATCC 42 (Water Resistance: Impact Penetration Test) determines the ability of a material to resist water penetration under spray impact. The test sample is clamped over pre-weighed blotter paper at a 45 angle and 500 ml of water is released from a spray head. The total water penetration is calculated and reported in grams by subtracting the weight of the dry blotter paper from the weight of the blotter paper after the test. Higher weights in grams represent lower water resistance. According to ANSI/AAMI PB70, this testing should be conducted on samples taken from the critical zones, which correspond to the entire gown for the isolation gowns, including sleeve seams and points of attachments. Ten specimens from two of the critical zones (chestcontinuous regions and sleeve seams) were tested for three isolation gown models. In total, 60 AATCC 42 tests were conducted.

The AATCC 127 (Water Resistance: Hydrostatic Pressure Test) determines the ability of a material to resist water penetration under increasing water pressure. The test sample is clamped in place, and the hydrostatic pressure is increased at a rate of 60 mbar/min until visible penetration of water droplets is observed. Thus, higher hydrostatic pressure represents higher water resistance. Similar to AATCC 42, ten specimens from two of the critical zones (chestcontinuous regions and sleeve seams) were tested for three isolation gown models. In total, 60 AATCC 127 tests were conducted.

Three ANSI/AAMI Level 2 isolation gown models (A, B, C) were tested in single layer and double layer configurations using two water resistance test methods; AATCC 42, and AATCC 127, which were previously defined. The test specimens were matched up from different samples for the same gown model when creating double layer configurations. AATCC 42 standard testing measures the total amount of water that penetrated through the gown fabric onto the blotter paper in grams; thus, higher numbers represent lower water resistance of fabric. Whereas, AATCC 127 hydrostatic test measures the water penetration resistance under constant hydrostatic pressure in cmH 2 O; therefore, high numbers in the test results represent higher water resistance of the fabric.

In total, 120 experiments were conducted to analyze the effects of gown model 

According to the AATCC 42 impact penetration results, fluid resistance of A, B, and C continuous region samples was increased about 89%, 97%, and 91%, respectively, when comparing single versus double layer configuration. However, the AATCC 127 hydrostatic resistance test resulted in about 62%, 26%, and 29% increase in the fluid resistance, respectively.

These results could be attributed to prolonged high-pressure water contact in the AATCC 127 test, in contrast to the single water spray in the AATCC 42, in which the outer fabric layer could resist the initial water impact causing the water to lose its initial impact energy resulting in a small number of droplets reaching the second inner layer. Although, there was an increase in the resistance performances of all models, most of the time double layer configurations of these 

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