High Speed Decontamination for Infection Control PPE Applications
New antimicrobial textiles have very fast rates of self decontamination. Chlorine based systems can achieve 99.9% decon in 30 sec with model pathogens. From the standpoint of Heathcare, users need to know that their PPE textile materials are free of infectious particles. These high speed decon speeds are very helpful for PPE applications. The contamination state of textiles in infection control PPE affects doffing and disposal behavior. When the textile self-decontaminates in 30 seconds the doffing and disposal processes are lower risk.
Slash Zone PPE Material Testing
Measurement of textiles for pathogen contamination can be done using various test methods. AATCC Method 100
is the most common test used in the US. There are closely related methods used in Europe and Asia. Method 100 uses a pathogen challenge liquid, applied so it saturates the textile and after hold time. there is a liquid extraction from the textile used to measure the level of self-decontamination. This saturation challenge and liquid extraction assay are appropriate for bedding, wipes, dressings and other textiles used in direct contact with patients and infectious fluids. In infection control PPE, the splash zone materials are impermeable membranes like gloves or membrane textile laminates used in aprons and gowns.
Contact Transfer PPE Materials
In infection control PPE ensembles, there are textile components that are not in the splash zone in patient care and are not subject to saturation by infectious fluids. A good example is an inner glove worn to provide mechanical protection from barrier glove failure. The BioTecT self-decontaminating textile glove
is not used in patient contact or exposed to contact with splash risk. In this configuration the contamination risk to the inner BioTecT glove is from pin hole failures in the outer glove or doffing related contamination when the outer gloves are removed. A useful distinction in the infection control PPE ensemble should be made between Splash Zone materials and Contact Transfer Zone materials.
Contact Transfer Zone Material Testing
In order to evaluate these challenge conditions, a related test was developed which uses a plated liquid pathogen challenge on agar and then after hold time, a contact transfer is made to a second agar plate to measure the level of self-decontamination. Modified Method 100 for Contact Transfer Challenge Test (CTC Test) is the new test designation. This draft test method is attached to this blog post. This method is much more consistent with the pathogen challenges that Contact Transfer Zone materials are subject to in the PPE ensemble. Infection control PPE textile layers are used behind a barrier membrane and can be evaluated with the CTC test method. An important aspect of the CTC method is the opportunity to run the assay at speed. Because Contact Challenge and Contact Transfer assay can be preformed in seconds, the rate of self-decon can be evaluated for exposure times to 15-30 seconds. The method 100 assay is limited to exposure times greater than 10 minutes. Using CTC testing textile contamination state can be evaluated for activities times that include doffing and donning speeds. Knowing that the textile layers in the Infection Control PPE Ensemble have completed their self decon process improves the safety of PPE systems.
There are currently 3 primary materials used in Infection Control PPE:
- Barrier membranes (some with and some without textile layers)
- Filter textiles
- Basic textiles
- Missing: Self Decontaminating non-barrier textiles
The barrier membrane textiles are use naturally to prevent liquids from penetrating the Personnel Protective Equipment (PPE) ensemble. The barriers must be competent to prevent liquids containing viral particles from penetrating. The ASTM 1671 is the most common test criteria for these materials. Under the 1671 criteria the membranes must be capable of preventing viral penetration at 2psi or 54 inches of water pressure. As a result of this rigorous requirement the barrier membranes used in healthcare have limited moisture vapor transport. With low moisture transport from the ensemble the ever present heat stress risk in PPE becomes a serious issue in “Ebola type” treatment environments
. The reason is in high infection risk Ebola treatment we currently have high PPE coverage using barrier textile materials. Cooler work environments are helpful never the less work sessions wearing high coverage barrier garments must be short, 2 hours or less in many situations. Healthcare workers must move ~150 watts of heat in order to maintain core body temperatures. As barrier membrane coverage area goes up workers in PPE find that they are not able to move there metabolic heat out of the ensemble. CDC and NIOSH are working new standards for Healthcare PPE materials.
Filter textiles are well accepted in healthcare, the N95 mask is a good example. This air filter requirement defines a textile that traps 95 of small <1 micron particles in the respiratory air flows. The limit of 95% is based on the need to limit respiratory effort. If the capture rate is higher the filter creates unacceptable restrictions to breathing because of the pressure drop over the filter materials. battery powered air pumps can be used to overcome the pressure drop from higher capacity filters. This down side is these powered full face filter units are not disposable and must be decontaminated manually after each use. The CDC Blog has more details on filter performance and filtration mechanisms
Basic cotton and poly-cotton textiles are ubiquitous in Healthcare. Scrubs and many other garments are used in PPE, hoods and other articles. Basic textile layers are not considered a key part of the infection control system
Self Decontaminating Textiles In the Infection Control PPE Ensemble
Self-Decontaminating Non-Barrier Textile enable some really important new healthcare PPE solutions. The use of Self-Decon materials improves the thermal transfer of the PPE system. A significant reduction in heat stress can be achieved. The kill speed of the material in decontamination is important. We have now achieved 99.9% pathogen kill in 30 seconds and 99.99% in 90 seconds using a contact transfer test method. So modern Self-Decontaminating textiles can be used as part of the PPE system on high risk services. At the same time reducing the heat load for the healthcare worker. Like all PPE materials there are limits to the application of Self-Decon Textiles. They should not be used in the splash zone on the front and arms of the ensemble. Like the N95 mask the Self-Decon material can be used where splash risk is low. This provides the opportunity to build infection control PPE ensembles that have 50-60% of the area with good moisture vapor transport for lower heat stress. At the same time these materials provides a lower stress garment the safety of healthcare workers are not compromised because the material provides pathogen self-decon in 30 sec.
Take a look at our self-decontaminating gloves
for a good introduction to how these textile tools can help solve your infection control challenges.