In order to properly protect healthcare workers from potentially infectious disease microorganisms it is important they don the appropriate Personal Protective Equipment (PPE). The Occupational Health and Safety Administration (OSHA) mandates that employers provide workers with levels of PPE protection consummate with the requirements of the clinical tasks required. Employers are encouraged to conduct a thorough risk assessment first to identify potential exposures to blood and body fluids, which often depends on the stage of the disease or condition in question. Other than face masks and gloves, the most widely-used type of PPE is gowning. A common misconception is that one is protected from blood, body fluids, and other potentially infectious materials when wearing any type of fluid-resistant garment. This blog explores the different classifications of gowns and how they are tested in order to help clarify levels of barrier protection and define the appropriate uses of each class.
Testing Methods and Classification Levels
The national standard for liquid barrier performance, “Liquid Barrier Performance and Classification of Protective Apparel and Drapes Intended for Use in Health Care Facilities” (ANSI/AAMI PB70), was established by the Advancement of Medical Instrumentation (AAMI) and accepted by the Food and Drug Administration (FDA) in 2004. This standard establishes four levels of testing for barrier protection. The tests were developed by either the American Association of Textile Chemists and Colorists (AATCC) or the American Society for Testing and Materials (ASTM):
- AATCC 42 – Water Impact Penetration test (WIP): a piece of blotter paper is first weighed and the material is placed on top of i
- A 500 mL stream of water is sprayed on the material from a specific distance
- The blotter paper is then weighed to discern how much water penetrated the material
- Material must pass the WIP with a result less than 4.5 grams; anything greater than this deems the material non-protective
- Minimal risk use: basic care, standard isolation, cover gown for visitors, or in a standard medical unit
- AATCC 127 – Hydrostatic Head Test (HHT): tests water resistance under increasing pressure
- The higher the hydrostatic pressure, the more water-resistant the material
- Material must have a higher than 20 cm result on the HHT
- AATCC 42 – Water Impact Penetration test (WIP): material pass the WIP test with a result of less than 1.0 gram
- Low risk use: blood draw, suturing, in the Intensive Care Unit (ICU), or a pathology lab
- AATCC 127 (HHT): material must have a WIP result of less than 1.0 gram
- AATC 42 (WIP): material must have a HHT result of greater than 50 cm
- Moderate risk use: arterial blood draw, inserting an Intravenous (IV) line, in the Emergency Room, or for trauma cases
- ASTM F1670 – Blood Barrier Test (BBT): measures resistance to synthetic blood under sustained contact for 60 minutes under varying levels of pressure; a
- Any blood penetration, or strikethrough, fails the test
- ASTM F1671 – Viral Barrier Test (VBT): measures resistance to microorganisms under sustained contact under varying levels of pressure
- A microbial assay is subsequently performed to search for microorganisms
- Any obvious liquid penetration or a positive result from the assay will fail the test
- High risk use: during long, fluid intense procedures, surgery, when pathogen resistance is needed or infectious diseases are suspected (non-airborne)
- It is crucial to remember that only Level 4 gowns are tested for viral penetration resistance; therefore, only Level 4 garments are considered impermeable to microbial penetration. Gowns complying with Levels 1, 2, and 3 standards may not be considered impermeable. Always look for the manufacturer’s intended use of the garment, as only product use is standardized, names of products are not. It is equally important to remember that conformance with recognized consensus standards is voluntary for a medical device manufacturer. A manufacturer may choose to conform to applicable recognized standards or may choose to address relevant issues in another manner.
Surgical Gowns v. Isolation Gowns
- Surgical gowns are regulated by the Food and Drug Administration (FDA) as Class II medical devices requiring a 510(k) premarket notification. Surgical gowns are designed with certain specified areas, called critical zones, rated for protection. These critical zones are based on anticipated user contact with blood or other potentially infectious fluids, although other areas of the garment may unexpectedly have contact with hazardous agents. For surgical gowns, the critical zones comprise, at minimum, the front panel and lower sleeves. The garment is then rated per the lower performing component. The AAMI standard allows the back of the gown to be non-protective, but mandates the entire front of the gown to have a barrier performance of at least Level 1. This means most of the garment may be Level 1 although the garment itself may be classified as a Level 4 gown.
- Isolation gowns are rated for the garment as a whole, due to the unpredictable types of potential contact associated with their use. The entire isolation gown, including the seams, but excluding the cuffs, hems, and bindings, must achieve the rated barrier performance. Open-backed isolation gowns do not meet the critical area parameters, and therefore they cannot be rated.
- Employers and healthcare workers should consider garment coverage, fit, tensile strength, and design in addition to fluid penetration rating when selecting a protective garment. While gowns are both more common and familiar to most healthcare settings on account of the ease with which they are donned and doffed, coveralls offer more effective overall protection to both front and back as well as to the extremities.
- Seam barriers are also an important consideration, especially when contact from hazardous materials or potentially contaminated sources can come from multiple directions and transmission methods. Coveralls with a zipper closure could potentially compromise user protection if the closure is not effectively covered with a flap of barrier material. Similarly, most surgical gowns rated for high levels of barrier protection only include those high-performance barrier materials in certain portions of the gown, typically the sleeves and front panels.
- The strength and proper fit of the garment are no less important considerations when selecting garments. If the fabric or seams and barrier layer on the fabric is not durable enough to withstand typical stresses expected during wear or use, or if the wrong size garment is used, they may tear when the user kneels, reaches, bends, or else snag on equipment or other objects and tear. The AAMI has also created a standard for sizing and labeling of protective garments, which will assist employers and healthcare workers choose the correct size when switching between suppliers. The American National Standard for Limited-Use and Disposable Coveralls—Size and Labeling Requirements (ANSI/ISEA 101-2014) includes a sizing chart and a set of exercises by which a user can validate a garment is the proper size and fit.