Question

How do we sterilize hospital textiles? What are the ASTM standards used? Describe the methods and equipment used write a 5 page long report

Answer 1

Sterilization of medical textile
According to the CDC (centers for disease control and prevention), “sterilization means the use of a physical or chemical procedure to destroy all microbial life, including highly resistant bacterial endoscopes.”
Bacterial spores are the most resistant of all living organisms because their capability to withstand destructive agents. Although the chemical or physical process used to destroy all pathogenic micro
organisms including spores is not absolute, when all parameters of the sterilization process have been met, instruments, supplies and equipment are thought to be sterile. Sterilization is the process used to inactivate microbiological contaminants and thereby transform the non sterile items into sterile ones. It is essential for hospital applications that sterile products are employed, and there are various techniques by which this can be achieved. Sterilization by steam, dry heat, ethylene oxide, and irradiation process are used depending on the product type and fiber characteristics. A sterilization process can bring about changes in properties as strength, absorbency and
appearance. Many hospitals have added peroxide plasma systems, such as sterrad, to their standard
steam autoclaves and ethylene oxide chambers in the central supply room. When designing fabrics for sterilization it is essential to understand the impact of
sterilization procedures on fabric performance features. In the U.S., steam autoclaves generally operate at 250-2700 (121-1320c). In Europe, flash sterilization temperatures up to 1380c have been proposed in respect to concerns about jakob-crueze disease. The polymer selection must be made with this type of temperature exposure in mind.

Sterilization vs. Disinfection:

It becomes important to distinguish between sterilization and disinfection. Sterilization results in destruction of all forms of microbial life, while disinfection results in destruction of specific pathogenic microorganisms. Because disinfection is faster and less expensive, some hospitals substitute high level disinfection for sterilization of medical instruments. An object should be disinfected or sterilized depending on its intended use. Critical
objects (those that enter sterile tissues or the vascular system or through which blood flows, such as implanted medical devices) require sterilization before use. Items that touch mucous membranes or nonimpact skin, like endoscopes, respiratory therapy equipment, and diaphragms, require high-level disinfection.

Methods:
Reliable sterilization depends on contact of the sterilizing agent with all surfaces of the item to be sterilized. Selection of the agent to achieve sterility depends primarily upon the nature of the item to be sterilized. Time required to kill spores in the
equipment available for the process then becomes critical.
Steam:
Heat destroys microorganisms, but this process is hastened by the addition of moisture. Steam in itself is inadequate for sterilization. Pressure, greater than
atmospheric, is necessary to increase the temperature of steam for thermal destruction of microbial life. Death by moist heat in the form of steam under pressure is caused by the dematuration and coagulation of protein or the enzyme-protein system within the cells. These reactions are catalyzed by the presence of water. Steam is water vapor; it is saturated when it contains a maximum amount of water vapor.
Direct saturated steam contact is the basis of the steam process. Steam, for a specified time at required temperature, must penetrate every fiber and reach every surface of items to be sterilized. When steam enters the sterilizer chamber under pressure, it
condenses upon contact with cold items. This condensation liberates heat, simultaneously heating and wetting all items in the load, thereby providing the two requisites:

moisture and heat.

No living thing can survive direct exposure to saturated steam at 250 F (120◦ C) longer than 15 minutes. As temperature is increased, time may be decreased. A
minimum temperature-time relationship must be maintained throughout all portions of load to accomplish effective sterilization. Exposure time depends upon size and contents of load, and temperature within the sterilizer. At the end of the cycle, re-evaporation of water condensate must effectively dry contents of the load to maintain sterility.
Ethylene oxide:
Ethylene oxide is used to sterilize items that are heat or moisture sensitive. Ethylene oxide (EO) is a chemical agent that kills microorganisms, including spores, by
interfering with the normal metabolism of protein and reproductive, processes,(alkylation) resulting in death of cells. Used in the gaseous state, eo gas must have direct contact with microorganisms on or in items to be sterilized. Because eo is highly flammable and explosive in air, it must be used in an explosion-proof
sterilizing chamber inn a controlled environment. When handled properly, eo is a reliable and safe agent for sterilization, but toxic emissions and residues of eo present hazards to personnel and patients. Also, it takes longer than steam sterilization, typically, 16-18 hrs. For a complete cycle.EO gas sterilization is dependent upon four parameters: EO gas concentration, temperature, humidity, and exposure time. Each parameter may be varied. Consequently, EO sterilization is a complex multi-parameter process. Each parameter affects the other dependent parameters.

Dry heat:
Dry heat in the form of hot air is used primarily to sterilize anhydrous oils, petroleum products, and bulk powders that steam and ethylene oxide gas cannot penetrate. Death of microbial life by dry heat is a physical oxidation or slow burning process of
coagulating the protein in cells. In the absence of moisture, higher temperatures are required than when moisture is present because microorganisms are destroyed through a very slow process of heat absorption by conduction.
Microwaves:
The no ionizing radiation of microwaves produces hypothermic conditions that disrupt life processes. This heating action affects water molecules and interferes with cell membranes. Microwave sterilization uses low-pressure steam with the no ionizing
radiation to produce localized heat that kills microorganisms. The temperature is lower than conventional steam, and the cycle faster, as short as 30 seconds. Metal instruments can be sterilized if placed under a partial vacuum in a glass container.
Small tabletop units may be useful for flash sterilizing a single or small number of instruments, when technology is developed for widespread use.
Formaldehyde gas:
Formaldehyde kills microorganisms by coagulation of protein in cells. Used as a fumigant in gaseous form, formaldehyde sterilization is complex and less efficacious than other methods of sterilization. It should only be used if steam under pressure will
damage the item to be sterilized and ethylene oxide and glutaraldehyde are not available. Its use for sterilization has been almost abandoned in the united states, Canada, and Australia. The method dates back to 1820, and it is still used in Europeand Asia.
Hydrogen peroxide plasma:
Hydrogen peroxide is activated to create a reactive plasma or vapor. Plasma is a state of matter distinguishable from solid, liquid, or gas. It can be produced through the action of either a strong electric or magnetic field, somewhat like a neon light. The
cloud of plasma created consists of ions, electrons, and neutral atomic particles that produce a visible glow. Free radicals of the hydrogenperoxide in the cloud interact with the cell membranes, enzymes, or nucleic acids to disrupt life functions of microorganisms. The plasma and vapor phases of hydrogen peroxide are highly sporicidal even at low concentrations and temperature.
Ozone gas:
Ozone, a form of oxygen, sterilizes by oxidation, a process that destroys organic and inorganic matter. It penetrates membrane of cells causing them to explode. Ozone is an unstable gas, but can be easily generated from oxygen. A generator converts oxygen, from a source within the hospital, to ozone. A 6 to 12 percent concentration of ozone continuously flows through the chamber. Penetration of ozone may be
controlled by vacuum in the chamber, or enhanced by adding humidity. At completion

of exposure time, oxygen is allowed to flow through chamber to purge the ozone. Cycle time may be up to 60 minutes depending on the size of the chamber or load.
Chemical solutions:
Liquid chemical agents registered by the epa as sterilants provide an alternative method for sterilizing heat sensitive items if a gas or plasma sterilizer is not available, or the aeration period makes ethylene oxide sterilization impractical. To sterilize items, they must be immersed in a solution for the required time specified by the manufacturer to be sporicidal. All chemical solutions have advantages and
disadvantages; each sterility has specific assets and limitations. These chemicals are: peracetic acid, glutaraldehyde, and formaldehyde.
Ionizing radiation:
Some products commercially available are sterilized by irradiation. It is the most effective sterilization method but is limited for commercial use only. Ionizing
radiation produces ions by knocking electrons out of atoms. These electrons are knocked out so violently that they strike an adjacent atom and either attach
themselves to it, or dislodge an electron from the second atom. The ionic energy that results becomes converted to thermal and chemical energy. This energy causes the death of microorganisms by disruption of the dna molecule, thus preventing cellular division and propagation of biologic life. The principal sources of ionizing radiation are beta particles and gamma rays. Beta particles, free electrons, are transmitted through a high-voltage electron beam from a linear accelerator. These high-energy free electrons will penetrate into matter before being stopped by collisions with other atoms. Thus, their usefulness in sterilizing an object is limited by density and thickness of the object and by the energy of the electrons. They produce their effect by ionizing the atoms they hit, producing secondary electrons that, in turn, produce lethal effects on microorganisms. Cobalt 60 is a radioactive isotope capable of disintegrating to produce gamma rays.
Gamma rays are electromagnetic waves. They have the capability of penetrating to a much greater distance than beta rays before losing their energy from collision. Because they travel with the speed of light, they must pass through a thickness measuring several feet before making sufficient collisions to lose all of their energy. Cobalt 60 is the most commonly used source for irradiation sterilization. The product
is exposed to radiation for 10 to 20 hours, depending on the strength of the source.

ASTM Standards

ASTM F2407 - 06(2013)e1

Significance and Use

• This specification provides requirements for surgical gowns used for protection of healthcare workers where the potential for exposure to blood, body fluids, and other potentially infectious materials exists. The specification requires barrier testing based on the system of classifying gowns established in AAMI PB70 and sets general safety requirements for surgical gowns based on biocompatibility, sterility assurance, and flame spread. Documentation and reporting requirements are set for important physical properties including tensile strength, tear resistance, seam strength, linting resistance, evaporative resistance testing, and water vapor transmission rate.
• This specification does not address protective clothing used for non-surgical applications, such as isolation gowns or decontamination gowns; protective clothing for the hands, such as surgical gloves, patient examination gloves, or other medical gloves; protective clothing for the head, such as goggles or face shields, surgical caps or hoods, surgical masks, or respirators; protective clothing for the feet, such as operating room shoes, shoe covers, or surgical boots; or other types of protective clothing and equipment worn by health care providers.
• Surgical gowns are either multiple-use or single-use products as designated by the manufacturer. This specification is intended to provide the basis for manufacturer claims for surgical gown performance and efficacy. For multiple-use gowns, this specification takes into account the anticipated care and maintenance of these products, by examining test requirements for surgical gown materials both before and after the maximum expected number of cycles for laundering and sterilization.
• Additional information on the processing of multiple-use surgical gowns is provided in AAMI ST65.
• While surgical gowns are classified for barrier performance as specified in AAMI PB70, this specification establishes certain other physical performance and documentation requirements for surgical gowns and their materials. Design requirements and recommendations are also provided for surgical gowns.
• Additional information for the testing, selection, and use of surgical gowns is provided in AAMI TIR11.Information on barrier classes in AAMI TIR11 does not currently match the levels established in AAMI PB70. However, AAMI TIR11 provides other useful information that is intended to aid in the selection and use of surgical gowns.

Scope

• This specification establishes requirements for the performance, documentation, and labeling of surgical gowns used in the healthcare facilities. Four levels of barrier properties for surgical gowns are specified in AAMI PB70 and are included in this specification for reference purposes.
• Some properties require minimum performance and others are for documentation only.
• AAMI PB70 evaluates the barrier properties of surgical gown fabrics using water only in Levels 1, 2, and 3. Since surgical gowns are exposed to blood and other fluids with different surface tensions, the performance of additional testing to identify the barrier levels to simulated biological fluids is required for a Level 4 gown.
• This specification does not cover all the requirements that a healthcare facility deems necessary to select a product, nor does it address criteria for evaluating experimental products.
• This specification is not intended to serve as a detailed manufacturing or purchase specification, but can be referenced in purchase specifications as the basis for selecting test requirements.
• The values stated in SI units or in other units shall be regarded separately as standard. The values stated in each system must be used independently of the other, without combining values in any way.
• This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.