Download - ISE789 End of Semester Review
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ISE789 End of Semester Review
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Course Projects
• They are being graded.• You can stop by my office on Monday to
pick them up.
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What we have covered
• Text on Healthcare– Organization and structure– Condition and methods– Position papers
• Biology for engineers– Disease and causes– Bioengineering
• Systems Engineering in Healthcare– Queueing models
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Continued• Engineering for Medical Devices
– Requirements– Anatomy– Biomechanics– Bio Inert– Bio active
• Bactericidal metals and models– Silver and other bactericidal metals– Ions
• Disinfectants and sterilization – Chapter posted two weeks ago– Methods and application
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The Exam
• Some multiple choice• Some short answers• Some problems• It will take you the entire time.
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Sterilization and Disinfection
ISE789Dr. R. A. Wysk
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Agenda
• What are disinfectants?• How do we disinfect, sterilize and clean?• Why do we disinfect?• What are the processes that can be used?
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Microorganisms
• Some good• Some not so good• Sterilize – no living forms• Disinfect – remove certain life forms
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Disinfect• Disinfectants are antimicrobial agents that are applied
to non-living objects to destroy microorganisms, the process of which is known as disinfection.– Cleaning an article of some or all of the pathogenic organisms
which may cause infection• A perfect disinfectant would also offer complete and full
sterilization, without harming other forms of life, be inexpensive, and non-corrosive.– There are no perfect disinfectants.
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The hows and how tos
• Cause the minimal amount of disruption to human and physical environment.
• Long or short life activities– Surgery
• Alcohol• Betadine
– Aldehydes
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Dry Heat Thermal MethodPrinciple/Conditions
Advantages Disadvantages Uses
Thermal inactivation: destroys by oxidation
Non-corrosive Simple design and principle
Less effective than moist heat; requires longer times and/or higher temperatures
Materials that are damaged by, or are impenetrable to, moist heat
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Hot Air OvenPrinciple/Conditions
Advantages Disadvantages Uses
160-180oC for 2-4 hours
•penetrates water-insoluble materials (e.g., grease and oil) • less corrosive to metals and sharp instruments than
steam
• slow diffusion, penetration • loading, packing critical to performance • not suitable for reusable plastics
•anhydrous materials, such as oils, greases and powders •laboratory glassware, instruments •closed containers
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Red Heat Flame MethodPrinciple/Conditions
Advantages Disadvantages Uses
Oxidation to ashes (Burning)
Rapid •initial contact with flame can produce a viable aerosol•possibility of accidental fire
Inoculating loops, needles, other disposable medical supplies
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Incineration MethodPrinciple/Conditions
Advantages Disadvantages Uses
Oxidation to ashes (Burning)1 – 60 minutes at temperatures up to 1000o C
Reduces volume of waste by more than 95%
•improper use may lead to emission of pathogens in smoke• requires transport of infectious waste•excess plastic (>20%) content reduces combustibility
• for decontamination of waste items prior to disposal in landfill
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Pasteurization MethodPrinciple/Conditions
Advantages Disadvantages Uses
Heating to below boiling point (generally 77oC) for up to 30 minutes
• can be used on heat sensitive liquids and medical devices •low cost
•Not particularly reliable •Milk and dairy products •some heat-sensitive medical equipment
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Boiling MethodPrinciple/Conditions
Advantages Disadvantages Uses
Maximum temperature attainable is ~100o C for 10- 30 minutes
Minimal equipment needed
•Not reliable•Cumbersome
• Small instruments and equipment
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Autoclaving MethodPrinciple/Conditions
Advantages Disadvantages Uses
• Steam under pressure15 – 90 minutes at temperatures up to 120o C at 5 psi•Steam under pressure4 – 20 minutes at temperatures up to 132o C at 27 psi
• Minimal time required• The standard for lab use, i.e., most dependable
•Loading and packing critical to performance• Items must be free of dirt and solid adhesions•Can damage heat sensitive items
• Penetration of sterile glassware •Decontamination of reusable supplies and equipment •Decontamination of infectious wastel
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Autoclave
A Front Loading Autoclave
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Autoclave
A Stove-top Autoclave
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Ultraviolet Light
• 260 nm light wave sources (UV lamps)• Effective for a variety of pathogens
(bacteria, virus and fungus)– Poor penetration (limited to light permeable
goods, like water)– Particulate, like dust, decrease the
effectiveness– Light source must be cleaned routinely
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Other methods
• Infrared radiation• Microwaves• Gamma radiation• Filtration
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Chemical Sterilants and disinfectants
• Instruments that can not be sterilized using high temperatures may undergo a gas sterilization process such as ethylene oxide or other chemical germicides.
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Chloride compounds (liquid bleach)Effective concentrations, contact time
Advantages Disadvantages Uses
•100 – 10,000 ppm (.01- 1%) free chlorine
•10 – 60 minutes
• broad spectrum •low cost •Widely available•Bactericidal at low temps
•Toxic, corrosive to skin and metals•Unstable•Inactivated by organic matter•Deteriorates under heat and light
•General disinfectant•Waste liquids•Surface contamination•Instruments
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Calcium hypochloriteEffective concentrations, contact time
Advantages Disadvantages Uses
•100 – 10,000 ppm (.01 - 1%) free chlorine
•10 – 60 minutes
• broad spectrum •low cost •Widely available•Bactericidal at low temps
•Toxic, corrosive to skin and metals•Unstable•Inactivated by organic matter•Deteriorates under heat and light
•General disinfectant•Waste liquids•Surface contamination•Instruments
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Iodine PreparationsEffective concentrations, contact time
Advantages Disadvantages Uses
•30 – 1,000 ppm (.003- .1%) free iodine
•10 – 30 minutes
• broad spectrum •Non-stinging •Less toxic•Less irritating
•Not consistent•Some iodophors support the growth of Pseudomonas
•Germicidal soaps•Surface decontamination•Instruments
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AlcoholsPrinciple/Conditions
Advantages Disadvantages Uses
•70-80% ethanol•60-90% isopropanol•10 – 30 minutes
• low toxicity •low cost•Low residue•Non-corrosive
•Rapid evaporation•Flammable•Damage to rubber, plastic and shellac•Ineffective against spores
•Skin disinfectant• Counter-tops
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Phenolic CompoundsPrinciple/Conditions
Advantages Disadvantages Uses
•400 – 50,000 ppm•10 – 30 minutes
• Tolerant of organic load •Leaves an active residue•biogradeable
•Pungent odor•Not sporicidal •Leaves a residue
•Antiseptic •some heat-sensitive medical equipment
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Hydrogen PeroxidePrinciple/Conditions
Advantages Disadvantages Uses
•3 – 30% aqueous solution•10 – 60 minutes•6% for 30
minutes
•Rapid action•No residue•Low toxicity •low cost •Environmentally safe
•Limited sporicidal•Corrosive to some metals•Potentially explosive at high concentrations•Can be irritating to eyes
•Surface decontamination •Instruments and equipment
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What to use? When?