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Measuring the Effectiveness of Protective Clothing
by Deborah Davis, MS, MBA
Barrier protection was once intended to prevent infection from being transmitted fromclinical practitioner to patient. Today, this protection is required for both healthcareworkers and their patients. Availability of personal protective equipment (PPE) ismandated by the Occupational Safety and Health Administration (OSHA). These requirementsare detailed in the OSHA standard on Occupational Exposure to Bloodborne Pathogens, whichwent into effect March 6, 1992, and include the implementation of the Centers for DiseaseControl and Prevention's (CDC) universal precautions. Universal precautions (standardprecautions in CDC's 1996 guidelines) as defined by CDC are a set of actions that involvethe use of protective barriers, such as gloves, gowns, aprons, masks, or protectiveeyewear, to reduce the risk of exposure of the healthcare worker's skin or mucousmembranes to potentially infective materials.
The Center for Devices and Radiological Health, Food and Drug Administration (FDA) hasresponsibility for regulating medical devices. Products, such as gloves, are required bythe FDA to meet certain performance requirements. These requirements define performanceproperties, such as the minimum strength, barrier protection, and fluid resistance, thatthese products must exhibit. For surgical gowns, the only required test is forflammability. If specific advertising and labeling claims are made, then the correspondingstandard must be met.
Manufacturers of PPE conduct extensive testing during product development and duringongoing quality control procedures to assure that their products meet the demandingperformance requirements of today's healthcare environment. Understanding the significanceof these tests can help clinicians assess the performance of each product as well as itsappropriate usage. Barrier effectiveness can be defined as the ability of PPE to withstandrigorous physical testing and bacteriophage penetration testing and to resist fluidpenetration under pressure. The efficacy of the barrier should not be compromised by theprocedure being performed. Standards and test methods may be developed by organizationssuch as the American Society of Testing and Materials (ASTM), the Association of Non-WovenFabrics Industry (INDA), the American Association of Textile Chemists and Colorists(AATCC), and various international groups. Typically, these organizations are made up ofscientists and engineers who have knowledge and experience in the behavior properties ofthe materials, the manufacturing processes, and the testing methodologies. Some of theorganizations develop test methods and standards based on a consensus approach, whichhelps ensure that the tests are not only scientifically sound and appropriate but alsothat the test methods fairly and accurately assess products made from a variety ofmanufacturing approaches, formulations, and materials.
For the most part, test methods are available for measuring clothing performance forseveral properties within each performance area (i.e., pull strength as well astear strength). The selected test methods should mirror expected-use conditions (allowingfor a margin of safety by simulating worst-case conditions) or at least rank clothingconsistent with in-use performance. Performance limits may be set in conjunction with thetest methods. For example, chemical protective gloves may be used against chemical"X" for a one-hour period. Selecting a chemical resistance test method and arequirement for chemical holdout is one way of judging acceptable performance. Performancelimits may sometimes be set by comparing results for an item of PPE that has alreadyprovided satisfactory performance. If the test method already has a pass/fail requirement,the conditions that lead to this determination need only be examined for their relevanceto the situation at hand.
Acceptable Quality Level (AQL). This typically refers to the barrier protectionconfidence level. A lower AQL number represents a higher quality product, i.e., amanufacturing process with fewer allowable defects. For purposes of sampling inspection,the AQL is used by manufacturers to identify the maximum number of allowable defects(pinholes) per hundred units. All gloves must be statistically sampled to verify theattainment of specific AQLs.
The 1000 mL water leak test and/or air inflation test is typically used to verify theAQL.
Water Leak. Consists of filling the glove with 1000 mL of water, suspending it,and allowing it to hang for two minutes then inspecting it for any leakage (ASTM D5151).
Air Inflation. Consists of inflating the glove with compressed air and visuallyinspecting for holes.
Chemical Permeation. This test method measures the resistance of protectiveclothing materials to permeation by liquid or gaseous chemicals under conditions ofcontinuous contact (ASTM F739).
PPE is designed to protect the wearer from exposure to a variety of potentiallyhazardous fluids and other materials. Effectiveness is measured in several ways.
Gowns and Drapes
Water Impact. A measurement of a fabric's resistance to the penetration of waterby impact, which indicates performance when fluid falls onto the fabric. Lower numbersreflect superior performance (AATCC 42).
Mason Jar. A measurement of the resistance of a fabric to an aqueous solutionunder constant pressure, which indicates performance when fluid remains standing on anarea of the fabric. Higher numbers reflect superior performance (IST 80.5).
Hydrostatic Head. A measurement of the resistance of a fabric to an aqueoussolution under constantly increasing pressure, which indicates performance when fluid isaccumulating on the fabric. Higher numbers reflect superior performance (AATCC 127).
Alcohol Repellency. A measurement of a fabric's resistance to aqueous isopropylalcohol solutions, which indicates the fabric's barrier capabilities to alcohol solutions.Higher numbers reflect superior performance (IST 80.8).
PPE comes under quite a bit of stress during its actual usage. Product strength ismeasured by its resistance to tearing, puncturing, and breaking and by its ability tostretch.
Tensile Strength. Measures how much force, in pounds per square inch, isrequired to stretch a sample of glove until it breaks. Higher numbers reflect superiorperformance.
Elongation. Measures how far, as a percentage of the original sample length, theglove stretches before it breaks. For example, if a 1" sample stretches 9"before it breaks, the elongation is 900%. Higher numbers reflect superior performance.
V-Tear. Measures the force in pounds per square inch necessary to start a tear(ASTM D412).
Trouser Tear. Measures the force (pounds per square inch) necessary to continuetearing once an initial tear has been made (ASTM D412).
Gowns and Drapes
Mullen Burst. A measurement of a fabric's resistance to puncture underincreasing pressure. Higher numbers reflect superior performance (ASTM D744).
Grab Tensile. A measurement of a fabric's resistance to tearing under increasingpulling stress without an initial tear in the material. Higher numbers reflect superiorperformance (ASTM D5034).
Elmendorf Tear. A measurement of a fabric's resistance to tearing undercontrolled force when there is an initial tear in the material (ASTM D1424).
All fabrics used in surgical gowns and drapes can burn. Manufacturers of gowns anddrapes incorporate a caution label on the package warning that the fabric can burn in theOR.
The rate of flame travel will vary with the specific material and can be measured usinga standard test method described in the Consumer Products Safety Commission (CPSC) 16 CFRpart 1610. This measure is the basis for the separation of various fabrics into threeclasses of flammability. Class I represents "normal flammability" or a flamespread time of 3.5 or more seconds.
Medical gloves, drapes, and gowns are required to undergo a variety of tests thatdemonstrate the potential of the material to cause irritation to the skin. These testsinclude:
While barrier effectiveness is foremost, if PPE is uncomfortable to wear, it is lesslikely to be used effectively. The discomfort may even interfere with the clinician'sability to do his or her job.
Tensile Stress (Modulus). Measures how much force, in pounds per square inch, isrequired to stretch a sample of glove twice its length. This is a measure of comfort;lower numbers reflect a softer, typically more comfortable glove.
Gowns and Drapes
Air Permeability. A measurement of the air flow that can be maintained through amaterial at a specified pressure, which indicates the fabric's breathability and comfortduring use. Higher numbers reflect superior performance (ASTM D737).
Handle-O-Meter (Stiffness). A measurement of the force of a fabric'sresistance to flexing (i.e., folding or draping). The higher the force, the stifferthe fabric (IST 90).
While fluid repellency and barrier tests are excellent indicators of PPE's performance,there is also testing, which more specifically demonstrates a material's ability toprevent penetration by microorganisms.
Bacteriophage penetration resistance is a test method that assesses the effectivenessof materials used in protective clothing for preventing the penetration of a surrogatemicrobe (Phi X 174 bacteriophage) suspended in a simulated body fluid under conditions ofcontinuous contact. This is a pass/fail test (ASTM F1671).
How the product is stored can affect the polymers and fabrics used in the products and,therefore, adversely affect barrier properties. Products should be stored in theiroriginal packaging in cool, dry environments and away from UV or fluorescent lights tohelp ensure the barrier effectiveness stability during storage. Stock should be rotated ona first in, first out basis.
Infection control is a vital concern in healthcare today. Intelligent and informed useof PPE is a critical component of your facility's infection control program. Understandingthe standards and tests that are used to measure the performance of this equipment willallow you to choose equipment that provides the best barrier protection and performancefor both healthcare workers and their patients.
Deborach Davis, MS, MBA, is Technical Director for the Gloves business unit ofAllegiance Healthcare Corporation (McGaw Park, Ill). Her primary responsibilities includedriving clinical research initiatives; coordinating various aspects of product developmentbetween the marketing, regulatory, manufacturing, and research and developmentorganizations; and publication and presentation of technical information for customers andfield sales personnel.
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