Understanding Barrier-Level Protection of Medical Gowns

Exposure to the pathogenic microorganisms harbored in blood, body fluids and other potentially infectious material (OPIM) can lead to occupationally acquired infections (OAIs) in healthcare workers (HCWs). That’s why it’s critical that healthcare providers don key pieces of personal protective equipment (PPE) and understand the levels of barrier protection these PPE items can afford them in patient-care and surgical situations.

The Association for the Advancement of Medical Instrumentation (AAMI) standard, “Liquid Barrier Performance and Classification of Protective Apparel and Drapes Intended for Use in Health Care Facilities” (ANSI/AAMI PB70), has served as the gold standard for the manufacturing of medical gowns’ barrier performance, which is key in preventing fluid and microbial strikethrough – a contributor to OAIs. The AAMI standard addressed the issue raised by the Occupational Safety and Health Administration (OSHA)’s Standard on Occupational Exposure to Bloodborne Pathogens, which mandated that the employer provide the HCW with protective apparel that is commensurate with the task and degree of exposure anticipated. What was needed was a method by which to assess a gown’s protective properties and ensure that it was suitable for the clinical task at hand; the AAMI standard introduced a classification system that guided manufacturers in the testing and labeling of the barrier performance of their products. In addition to strikethrough, the standard addresses parameters for flammability resistance and linting, which can serve as a carriage vehicle for microbial particles.

At the heart of this AAMI standard are the four levels of barrier protection, ranging from level one, which is the lowest level of protection, to level four, which is the highest level. Utilizing these classification levels, manufacturers are able to label their products according to the level of protection their product provides, and HCWs can more easily select the appropriate barrier they need. All gowns and surgical drapes are subject to this classification system.

The first classification level is determined by using a test called AATCC 42 – Water Impact Penetration, which measures the material’s resistance to water penetration under single-spray contact. The material is placed on top of a piece of pre-weighed blotter paper and positioned at a 45-degree angle; a 500 mL stream of water is then sprayed onto the material from a funnel located at a specific distance above the sample. The material is then removed and the blotter paper is weighed to ascertain how much water has been absorbed. For a level one classification, a material must pass water impact penetration with a result lower than 4.5 grams; material with a result higher than 4.5 grams is considered to be non-protective.

The second classification level is determined by using a test called AATCC 127 – Hydrostatic Head Test, which measures the material’s resistance to water penetration under increasing pressure. For a level two classification, the material must pass water impact penetration with a result less than 1.0 gram. The water or hydrostatic pressure is steadily increased until three water droplets form on the material sample. The hydrostatic pressure is then recorded; for a level two classification, the material must have a result higher than 20 cm on the hydrostatic head test. The higher the hydrostatic pressure, the more resistant the material is to penetration by water.

The third classification level is determined by testing material using the aforementioned water impact penetration and hydrostatic head tests. For a level three classification, the material must have a result of less than 1.0 gram on the water impact test and greater than 50 cm on the hydrostatic head test.

To attain level four classification, material must be considered to be impervious, and is subjected to the blood barrier test (ASTM F1670) and the viral barrier test (ASTM F1671). The blood barrier test measures a material’s resistance to synthetic blood under constant contact. The sample is mounted on a cell between the synthetic blood and a viewing port, then subjected to atmospheric pressure for 5 minutes, 2.0 psi for 1 minute and atmospheric pressure for 54 minutes. If there is any strikethrough on the sample during the 60-minute test, the sample fails the test. The viral barrier test measures the material’s resistance to penetration of a microorganism under constant contact. The sample is mounted similarly to the blood barrier test and is then subjected to the same time and pressure protocol. If any liquid penetration occurs, the sample fails. If there is no visible liquid penetration at the end of 60 minutes, a microbial assay is performed to determine if any non-visible penetration occurred. If any microbial penetration is found, the sample fails the test.

Many HCWs, whether they are new to the field or seasoned veterans, can be confused by the provisions in the AAMI standard, and perhaps have not been educated sufficiently about the selection and use of protective apparel. Healthcare epidemiologist Suzanne Pear, RN, PhD, CIC, associate director for infection prevention practices within the Scientific Affairs and Clinical Education Department of Kimberly-Clark Health Care, points to herself as an example. “I have been an active and I think, well-read and informed healthcare clinician for over three decades, but the first time I became acquainted with the AAMI PB70 Standard when I was called upon a few months ago to develop an accredited clinical education program on the topic. Until that time I was ignorant of the fact that there was a scientifically reliable and replicable means of evaluating the liquid barrier protection provided by different types of protective apparel, in particular gowns used for cover, isolation or surgery.”

Pear acknowledges that much is still left to learn. “Our knowledge about the types of exposures and contaminations, (e.g., viral, bacterial, fungal) that occur to HCWs, the methods of exposure (e.g., aerosol to mucus membranes, microbial penetration of apparel with or without a body fluid vehicle, or by contaminated hands transfer) and the infectious outcomes is very limited,” she says. “We do know that using isolation gowns in addition to gloves can reduce cross transmission to patients and reduce patient infection incidence, but the protective benefit of gowns to the HCW has not been adequately studied.”

Pear continues, “Although known patient benefit of HCW gown use should be sufficient to ensure compliance with Standard- and Transmission-based use of personal protective equipment (PPE), it usually isn’t. HCW compliance with PPE is similar to compliance with hand hygiene – suboptimal. Most hand hygiene occurs after patient contact, with leads one to think that HCWs are cleaning their hands to protect themselves rather than their patients. Maybe if there were more data about the real risk that HCWs expose themselves to from either not wearing protective apparel or wearing inadequately protective apparel, maybe that would change both HCW behavior and demand for the level of PPE necessary for the situation.”

AAMI guidelines are not the most user-friendly, and sometimes healthcare professionals must endeavor to be students of science to interpret them.

“As I understand it, the AAMI PB70 barrier protection levels were developed by textile engineers – and rightly so as they are the experts in that area,” Pear says, adding, “However, the AAMI standard does not connect the clinical dots from the laboratory bench to the patient’s bedside. What that means is that clinicians usually have to guess at the appropriate AAMI level gown (if they know about AAMI and have them available) for the potential exposure they will be facing or else use only apparel classified to meet the highest level of exposure risk to ensure protection adequacy.”

Knowledge deficits or gaps about infectious materials exposure and barrier protection issues may exist, so barrier-product manufacturers are on the lookout for opportunities to help educate HCWs.

“While we can always do better in educating the clinicians that wear protective products, I am always impressed with their knowledge of standards that are in place to both protect them and their patients,” says Frank Czajka, president of Medline’s Proxima division. “Medline teamed with DuPont to create continuing education programs on AAMI, with literature that focuses on AAMI levels in our products, including posters for posting in facilities, brochures explaining the standard, and clear color identification and labeling for the AAMI levels.”

Manufacturers have endeavored to make gown selection easier for HCWs by providing visual cues in their product packaging and labeling.

“Medline color codes our products in three visual places as well as clearly labels our products to their AAMI level,” Czajka explains. “The gowns are color coded on the neck binding of the product, the exterior package and the passcard on the front of the gown to its specific AAMI level: Green equals AAMI level two; purple equals AAMI level three, and blue equals AAMI level four. This helps to avoid mis-selection of products by making the protection level easy to identify and also allows team members to clearly see the level of protection that is being worn by all. All Medline reinforced drapes exceed AAMI level four standards in that they pass the ASTM F 1670 required by AAMI and additionally pass ASTM F 1671 (viral penetration test).”

Judson Boothe, marketing director of medical supplies for Kimberly-Clark Healthcare, explains that the company organized its isolation gown portfolio into three performance-based levels after identifying the need for a better understanding among HCWs of AAMI guidelines as well as ease of selection. “The three categories for our isolation gowns are KC100, KC200, and KC300, which correspond to the AAMI level that each isolation gown meets,” Boothe says. “For example, KC100 isolation gowns meet AAMI level one, KC200 isolation gowns meet AAMI level two, and KC300 isolation gowns meet AAMI level three. To assist HCWs in recognizing what AAMI level of protection they will need for the types of procedures they perform, we identified specific procedures as reference points for each category level. KC100 isolation gowns provide protection for uses that expect the risk of fluid exposure to be low. KC100 is recommended for basic patient care, transporting patients, laundry and housekeeping duties. KC200 isolation gowns provide protection from low to moderate fluid exposure seen in procedures such as suturing, blood draw, inserting IVs and specimen handling. KC300 isolation gowns provide protection for uses where moderate exposure to fluids is expected such as in trauma units, ER, burn units, critical care units and contact isolation areas. Also, each isolation gown features a custom neck tape that easily identifies their AAMI level of protection.”

ICT asked barrier-product experts to share their best suggestions for how healthcare workers can assess a product’s protective capabilities and suitability for the degree of anticipated exposure.

Czajka suggests, “Going by the AAMI levels is a great start. Level two is great for about 60 percent of cases, level three for about 85 percent. The remaining (wetter/longer) cases should have level four protection. I also think the clinicians need to rely on their product manufacturer for information and guidance in order to make sure the right product is selected.”

Pear notes that “At a minimum, HCWs must know about and understand the AAMI PB70 Standard. They also need to know what AAMI level gown(s) they are being provided with. AAMI PB70 is the only liquid barrier performance standard currently available with which to base any judgment of fabric liquid barrier performance. Without that information, clinicians will just have to keep their fingers crossed that their protective apparel will really protect them.”