Atul P Kulkarni, Department of Anesthesia, Critical Care and Pain, Division of Critical Care Medicine, Tata Memorial Center, Homi Bhabha National Institute, Mumbai, Maharashtra, India, Phone: +91 9869077526, e-mail: ni.oc.oohay@kaaylaviak
Copyright © 2020; Jaypee Brothers Medical Publishers (P) Ltd.© The Author(s). 2020 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Understanding the concepts of disinfection, sterilization, cleaning and asepsis is of prime importance to prevent transmission of infection to patients and to protect healthcare workers (HCWs). Proper disinfection of surfaces after cleaning, an important consideration at all times, has assumed special significance during the current pandemic. The global shortage of disposable equipment such as personal protective equipment (PPE), specifically N95 masks and surgical 3 ply masks, and other items makes the HCWs vulnerable to transmission of infection while caring for these patients. Therefore, resterilization of such items has assumed equal importance. Cleaning, the first step in the process of sterilization, is of vital importance to reduce bioburden. The type of disinfection required depends on the nature of the equipment and its intended use. For example, critical items need high-level decontamination. In this narrative review, we elaborate on the methods of decontamination and sterilization. Many chemicals can be used for both sterilization and disinfection, and the difference lies in the concentration of the chemical and exposure time. We have also summarized strategies which can be used for resterilization of single-use items, in view of the shortages caused by the current pandemic.
Kothekar AT, Kulkarni AP. Basic Principles of Disinfection and Sterilization in Intensive Care and Anesthesia and Their Applications during COVID-19 Pandemic. Indian J Crit Care Med 2020;24(11):1114–1124.
Keywords: Chemical methods of sterilization, COVID-19 pandemic, Disinfection, Physical methods of sterilization, Personal protective equipment, Resterilization, Reuse, Sterilization
Disinfection, sterilization, cleaning and maintenance of asepsis are extremely important for health care workers (HCWs), particularly in the intensive care units (ICUs) and operating rooms. This helps in preventing transmission of infections to patients and protecting HCWs, not only every day, but also during outbreaks and pandemics. Nonadherence to established guidelines can cause outbreaks of infection and has adverse impact on outcomes. 1
In pre-coronavirus disease 2019 (COVID-19) era, single use (disposable) items were resterilized and used due to cost constraints in the low-income countries. During the current pandemic, due to the upsurge in the number of patients, the developed world is forced to resterilize single-use items ( Fig. 1 ).
A giant sterilizer machine that can sterilize up to 80,000 respirator masks per day
In this narrative review, we discuss sterilization of equipment and disinfection of environmental surfaces, and strategies for the reuse of disposable items. For further in-depth understanding, the reader is referred to a review by McDonnell et al. 2
Bioburden is the number of microorganisms present on the surface before disinfection or sterilization. Biological byproducts of patients, e.g., upper and lower respiratory tract secretions, saliva, feces, and urine, can potentially transmit infections.
Cleaning is a process of reducing the bioburden by the physical removal of organic matter, involving washing (with soap and cold water) and scrubbing (mechanical action).
Disinfection eliminates many or all microorganisms, except some bacterial spores. It is further classified into high-, intermediate-, and low-level disinfection.
Sterilization destroys or eliminates all forms of microorganisms including bacterial spores. (Details below).
Asepsis ensures maintenance of the sterility of the already sterilized products or equipment. By itself, it does not ensure sterility, if sterilization is flawed.
McDonnell described a triad of human safety, machine compatibility and agent efficacy for disinfection or sterilization process, which can be adapted for HCWs.
Spaulding classified all hospital equipment into three categories based upon their intended use. 4 These categories depended on the risk of infection, nature of exposure to tissues and meticulousness of the sterilization, and disinfection.
These are used in the sterile tissues or the vascular system. These are surgical instruments, cardiac, vascular and urinary catheters, pressure transducers, implants, and various needles. They need complete sterility before use, and hence, they are either sterilized (e.g., steam sterilization for surgical instruments) or procured as sterile single-use devices (needles or catheters). Equally important is the maintenance of asepsis during their use.
These are exposed to intact mucous membranes or nonintact skin, but do not ordinarily break the tissue barrier, hence pose an intermediate risk. The tissues are susceptible to infections produced by bacteria and viruses but are resistant to infection caused by bacterial spores, so sporicidal sterilization is not required. These include breathing systems, laryngoscope blades, fiberoptic endoscopes, etc. A high-level disinfection (HLD) is mandatory for these items.
These include blood pressure cuffs, pulse oximeters, electrocardiography (ECG) cables and electrodes, and patient surroundings such as furniture and floors that are in touch with intact skin. The risk of transmission of the infections to patients with these items is very low, but they should not be exposed to nonintact skin (pressure sore, skin abrasions, etc.). These need either intermediate-level or low-level disinfection based on the bioburden. It is important to remember that incorrect method or inadequate sterilization/disinfection can expose both the patient and the HCWs to the risks of infection. On the other hand, unnecessary high level of sterilization/disinfection wastes resources and reduces the life of the equipment.
It is vital to always follow the manufacturer's recommendation for disinfection, sterilization, and cleaning. The use of incompatible methods voids the warranty and can permanently damage the equipment beyond repair and, thus, worsen the supply shortage. For example, the use of alcohol-based disinfectants for disinfection of ultrasound probes can cause permanent damage to the probes due to its reaction with the rubber head of the transducer. 7 The methods for sterilization and disinfection for the routinely used equipment in ICU and operation theater (OT) are given in Table 1 .
Sterilization/disinfection of routinely used equipment in ICU and ORs
| Categories of hospital equipment | Item | Preferred method | Alternative method |
|---|---|---|---|
| Semicritical | Steel laryngoscope blades 8 | Cleaned with cool running tap water. Immersed in disinfectant solution as per manufacturer's recommendations (glutaraldehyde, hydrogen peroxide, ortho-phthalaldehyde, and peracetic acid with hydrogen peroxide 1% sodium hypochlorite or alcohol-based disinfectants) for a minimum of two minutes and rinsed with lukewarm running tap water. Brushed in enzymatic detergent and rinsed again in reverse osmosis (RO) water to remove detergent residuals. Dried with a lint-free cloth or filtered pressurized air. The bulb may be cleaned with a cotton ball dampened in alcohol (IPA), 1% sodium hypochlorite or alcohol-based disinfectants | Autoclave |
| Video laryngoscope blades | Plasma sterilization 70% IPA Wipe 9 Ethylene oxide (EtO) gas 10 | ||
| Silicone face mask and manual resuscitator bag 11 | Disassemble and rinse parts under cold running water. Submerge all parts in water containing dish washing detergent at 60–70°C and clean with brush Cidex OPA (ortho-phthalaldehyde) 0.55% solution for 60 minutes Or sodium hypochlorite 0.5% solution for 20 min Autoclave or chemical disinfection as per manufacturer's recommendation | Autoclave | |
| Silicone breathing systems (circuits) of ventilators 12 | ETO (banned in some countries) | ||
| Oral thermometers | 1% sodium hypochlorite or alcohol-based disinfectants | ||
| Temperature probes | |||
| Noncritical | ECG cable | 1% sodium hypochlorite or alcohol-based disinfectants | |
| Pulse oximeter 9 | Cleaning with alcohol solution Disinfection with glutaraldehyde solution: 2.0% | 1:10 bleach CIDEX OPA if HLD is required | |
| Axillary thermometers | Wash with cool water 1% sodium hypochlorite or alcohol-based disinfectants | ||
| Stethoscopes | 70% isopropyl alcohol solution | ||
| Plastic blood pressure cuffs | 0.5% hydrogen peroxide | ||
| Cloth blood pressure cuffs | Remove the tubing and inflation bag. Wash cuff with soap water | ||
| Ultrasound probe 13 | Alcohol-free quaternary ammonium wipes | Sodium hypochlorite wipes | |
| Environmental surfaces | Ventilator screen 9 | Isopropyl alcohol (70% solution) | |
| Bleach (10% solution) | |||
| Anesthesia workstation | Disinfection as per manufacturer's recommendation | Can be covered with sterile plastic sheet which can be changed between two cases | |
| Monitor screen 14 | Cleaning with a lint-free cloth, moistened with warm water (40°C) and soap, a diluted noncaustic detergent, ammonia- or alcohol-based cleaning agent | Do not use bleach | |
| Disinfection with ethanol 70%, isopropanol 70%, or Cidex-activated dialdehyde solution | |||
| Ultrasound machine 13 | Covering with plastic sheet to change between the patients | Alcohol-free quaternary ammonium wipes |
This is the first and key step during the decontamination process. Disinfection or sterilization is not effective unless the equipment is completely cleaned. If possible, the equipment should be dismantled. A temperature above 45°C causes coagulation of the proteinaceous material (which forms a protective layer), making removal of microorganisms difficult and should be avoided. Cleaning should be done in a separate room to prevent potential exposure to patients and HCWs.
Automated methods for cleaning, such as washer disinfectors, low-temperature steam, and ultrasonic baths, can be used to avoid exposure of the HCWs to the chemicals and microorganisms. Manufacturer's recommendations should be followed while using automated methods.
Sterilization can be done by physical or chemical methods. Steam under pressure, dry heat, ethylene oxide (EtO) gas, gas plasma, and liquid chemicals like glutaraldehyde are the principal sterilizing agents used in healthcare. The key features of different methods of sterilization are summarized in Table 2 .
Commonly used sterilization techniques in health care
| Technique | Process | Mechanism of action | Uses | Advantages | Disadvantages |
|---|---|---|---|---|---|
| Steam sterilization | 121°C for 15 minutes or 134°C for 3 minutes | Denaturation and coagulation of enzymes and structural proteins | Surgical instruments can be used for stainless steel laryngoscope (battery removed) | Safe to patient, HCWs and environment | Damage to heat-sensitive equipment |
| Low cost | Loss of sharpness (needles, etc.) | ||||
| Can work in the presence of moisture | |||||
| Ethylene oxide (EtO) gas sterilization 15 | Concentration of 450–1200 mg/L, at temperatures of 37 to 63°C and RH of 40 to 80% for 1 to 6 hours | Alkylation (replacement of a hydrogen atom with an alkyl group) of microbial proteins, DNA and RNA | Heat-sensitive equipment and instruments | Can sterilize heat- or moisture-sensitive medical equipment | Moderate cost, prolonged cycle time Potential toxicity to patients, HCWs, and environment Banned for use in respiratory equipment in some countries |
| Disposable catheters and guidewires | |||||
| Hydrogen peroxide vapor (HPV) and hydrogen peroxide gas plasma (HPGP) sterilization 16 | Concentration of 6 mg/L, temperature range of 37–44°C | Hydroxyl [·OH, the neutral form of the hydroxide ion (OH−)] and hydroperoxyl (HO2·)-free radical and gas plasma formation | Heat-sensitive equipment and instruments | Low-temperature sterilization Safe to patient, HCW, and environment | High cost Does not work in the presence of moisture, cellulose, or cotton. Poor penetration due to condensation at surface 17 |
| Cycle time of 75 minutes |
HCWs, healthcare workers
The key features of other chemicals used in healthcare are enumerated in Table 3 .
Commonly used chemical disinfectants in health care
| Chemical, concentration used | Uses | Caution/limitation |
|---|---|---|
| Alcohols Ethyl alcohol (ethanol, alcohol) and isopropyl alcohol, 60 to 90%; use of higher concentrations leads to quick evaporation and reduced contact time 18 | Environmental surface cleaning (recommended for COVID-19) | No sporicidal activity Concentrations less than 50% have poor antimicrobial activity Avoid exposure to face visor, goggles, and ultrasound probes |
| Disinfection of oral and rectal thermometers, hospital pagers, scissors, and stethoscopes. Rubber stoppers of multiple-dose medication vials or vaccine bottles | ||
| Surface cleaning | ||
| Halogen-releasing agents: Hypochlorite solutions: 0.1% (1000 parts per million/ppm) for surface cleaning | Environmental surface cleaning (recommended for COVID-19) Sporicidal activity present but not commonly used for sterilization 20 | Irritation of eyes, skin, and mucous membrane Avoid exposure to persons with reactive airway disease like asthma Cause corrosion of metal. Fresh dilution should be prepared daily Solution should not be exposed to direct sunlight or kept open for long time |
| Higher concentration of 0.5% (5000 ppm) for large (>10 mL) spills of blood and body fluids and C. auris and C. difficile 19 | ||
| Hydrogen peroxide >0.5% 18 | Environmental surface cleaning (recommended for COVID-19) | Irritation of eyes Organisms with high cellular catalase activity such as Staphylococcus aureus, Serratia marcescens, and Proteus mirabilis are relatively resistant and require nearly an hour of exposure No need for daily fresh preparation Solution should not be exposed to direct sunlight or kept open for long time. |
| It can enhance the removal of organic matter and organisms, hence also used for washing of wounds | ||
| Glutaraldehyde 2% (Cidex®) for 20 minutes, 21 or ortho-phthalaldehyde (Cidex®OPA) 0.55% for 12 minutes 22 | Disinfection of optical instruments such as cystoscopes or bronchoscopes | Meticulous cleaning to remove organic matter Prior leak test Avoid ortho-phthalaldehyde for urological instruments |
| For sterilization, exposure as long as >10 hours is required. 5 | ||
| Noncorrosive and has no deleterious effects on lens cement | ||
| Halogen-releasing agents iodine and iodophors 20,23 | Skin preparation | Should not be used on silicone catheters 18 |
| Nasal spray and mouthwash for patients to protect HCWs 24 | ||
| Chlorhexidine impregnation or 0.2% aqueous solution 25 | Vascular catheters, needleless connectors, and antimicrobial dressings, gargles or mouthwash. | Poor action against coronaviruses, nonenveloped viruses, mycobacteria Maximum bactericidal effect occurring within 20 seconds |
| Chlorhexidine 2% in 70% alcohol 0.5% in 70% alcohol | Preprocedural skin preparation\Skin preparation for central neuraxial blockade. 26 (2% in 70% alcohol) Hand disinfectant (0.5% in 70% alcohol) | Efficacy comparable with that of 10% povidone-iodine solution 27 |
| Quaternary ammonium compounds: up to 7th generations available). See text for the mechanism of action 28 | Environmental sanitation of noncritical surfaces, such as floors, furniture, and walls 18 | Effective dose of the QACs is compromised if used with cotton mops or cleaning towels |
| Better to use wipes and follow manufacturer's recommendation. |
Quaternary ammonium compounds are cationic surfactants, with wide antimicrobial spectrum including bacteria, enveloped viruses like human immunodeficiency virus (HIV) and Hepatitis B virus (HBV). Quaternary ammonium compounds kill microorganisms by adsorption, penetration, and destruction of cytoplasmic membrane and cell wall and by degradation of proteins and nucleic acids. They are sporostatic at low concentrations (0.5–5 mg/L) and do not act against nonenveloped viruses but are microbiocidal at higher concentrations (10–50 mg/L). 28,29 Quaternary ammonium compounds of different generations have been used; the first generation being benzalkonium and alkyl chains, and the latest 7th generation is Bis-QACs with polymeric QACs.
Peracetic acid is a high-potency biocidal oxidizer with a similar mechanism of action to other oxidizing agents. It releases free oxygen and hydroxyl radicals leading to microbiocidal effects against bacteria (including mycobacterium) and bacterial spores, fungi, and viruses (poliovirus, rotavirus, HBV, and HIV) rapidly (2O2. In the concentrated form, peracetic acid is corrosive and irritating. It is available as 0.2% and 0.35% solutions. It is safer but costlier than glutaraldehyde, and in the future, after further trials, it may be an alternative to glutaraldehyde.
Ultraviolet germicidal irradiation (UVGI), which damages the microbial nucleic acid, has been used for the disinfection of titanium implants, contact lenses, etc. Its maximum bactericidal effect occurs at 240–280 nm (UV-C). Mercury vapor lamps are commonly used as they emit radiation at 253.7 nm.
Upper-room UVGI provides disinfection of the upper part of air in the room and can be used in the occupied rooms without using protective clothing. Effective air disinfection in the lower part of the room depends on vertical air movement. There is a lack of data supporting its use in isolation rooms. It can cause occasional skin erythema and keratoconjunctivitis in patients and visitors. The use of UVGI for the decontamination of masks [filtering face piece respirators (FFRs)] is described below in detail.
Disinfection can be classified into high-, intermediate-, and low-level disinfection. While sterilization mandates prolonged exposure, disinfection needs shorter exposure. These terms are not interchangeable.
It destroys all microorganisms but not bacterial spores. Many chemicals can be used for disinfection (glutaraldehyde, hydrogen peroxide, etc.) with exposure times varying from 8 to 45 minute, at 20 to 25°C. They can be used for sterilization when used for prolonged period. High-level disinfection is mainly used for semicritical items.
It destroys all microorganisms but spares spores and some small nonenveloped viruses. Intermediate-level disinfection is used for noncritical items, which are visibly soiled with patient's fluids and blood. This is done with alcohol or QACs, etc.
It destroys most microorganisms and some viruses but has no action on Mycobacterium tuberculosis and spores. Low-level disinfection can also be achieved with alcohol or QACs, etc., at lower exposures. Low-level disinfection is used for noncritical items.
Transmission of the SARS-CoV-2 virus can occur directly between humans and indirectly through contact with surfaces or objects. 33 It remains viable in the surroundings of the infected person. The viability of the virus depends on bioburden, ambient temperature, relative humidity (RH), and pH. In the areas surrounding even stable COVID-19 patients, there is high likelihood of contamination of environmental surfaces and ICU furniture, including common electronic equipment, e.g., telephones, computers, etc. It is therefore vital that all surfaces are frequently cleaned and disinfected.
SARS-CoV-2 virus can survive up to seven days at room temperature (22°C) with a RH of 65% on stainless steel and plastic surfaces, indicating possible fomite transmission. It is extremely stable over a pH of 3–10. Viable virus can still be present on the outer layer of a surgical mask on the seventh day. It becomes nonviable on cardboard in 24 hours. 36 On copper surfaces, it becomes nonviable within 4 hours. Soap solution (1:49) did not achieve effective virucidal effect.
The selection of disinfectants should be based on various factors such as targeted microorganisms, availability of disinfectants, etc. The persons preparing and using the disinfectant solution should be protected using the appropriate PPE.
Most disinfectants get rapidly inactivated in the presence of organic material. Hence, it is important to clean the surface with soap water or detergent and mechanical action. The following disinfectants are recommended for disinfection of environmental surfaces in healthcare settings.
Ethanol 70–90% (higher concentrations lead to quick evaporation with reduced contact time)Chlorine-based products (e.g., hypochlorite) at 0.1% (1,000 parts per million/ppm) for general environmental disinfection or 0.5% (5,000 ppm) for large spills of blood and other fluids
Hydrogen peroxide >0.5%When the disinfectants are used on surfaces in recommended concentration, for appropriate duration, they achieve a >3 log10 (99.9%) reduction of coronaviruses 20 ( Table 4 ).
Cleaning and disinfection of environmental surfaces: recommended schedule and methods 19
Ethanol 70–90% Hypochlorite 0.1% (0.5% for blood and body fluids large spills) Hydrogen peroxide >0.5%Terminal cleaning is the disinfection and sterilization of patient supplies and equipment after patient discharge, while concurrent cleaning is the disinfection and sterilization during hospitalization. Some countries use vaporized hydrogen peroxide or ultraviolet (UV) irradiation for terminal disinfection. If either technique is used, it should supplement and not replace the manual cleaning and disinfection using ethanol, hypochlorite, or hydrogen peroxide. The supplemental methods (vaporization or irradiation) should be used only with the room empty.
Spraying individuals with disinfectants (in a tunnel, cabinet, or chamber) does not reduce an infected person's ability to spread the virus and can be harmful to the individuals due to toxic chemicals. World Health Organization does not recommend spraying or fogging with chemicals in indoor spaces due to its adverse health effects on HCWs. Similarly, spraying or fumigation of outdoor spaces is not useful at its best and can be harmful to individuals, at its worst.
We must emphasize here that if adequate PPE is available, resterilization and reuse should not be carried out solely to save money. Due to overwhelmed healthcare systems, and shortage of disposables, we need to decontaminate and resterilize PPE but maintain its functionality. For the methods of sterilization/decontamination for reuse of items which form the part of PPE, see Tables 5 and and6 6 .
Current methods for sterilization/decontamination for reuse of various items constituting PPE
Hydrogen peroxide vapor Moist heat 65 ± 5°C and 50–80% RH for 30 minutes UV germicidal irradiation Cleaning with soapy water, detergent, or disinfectants Sterilization using steam or EtO Use of alcohol or household bleachIf adequate PPE is available, resterilization and reuse should not be carried out solely to save money
Decontamination and sterilization methods for N95 FFR
50 cycles of 85°C heat at 30% RH 20 cycles with dry conditions with temperatures up to 100°C 10 cycles with UV irradiationIf adequate PPE is available, resterilization and reuse should not be carried out solely to save money
UVGI, ultraviolet germicidal irradiation; HPV/VHP: hydrogen peroxide vapor; MGS, microwave-generated steam; EtO, ethylene oxide; H2O2, hydrogen peroxide; HPGP, hydrogen peroxide gas plasma
These are first wiped with neutral detergent solution using clean cloth or rinsed if needed and cleaned with 0.1% hypochlorite solution. Alcohol is avoided as it can damage and discolor plastic.
Single-use disposable PPE suits and three-ply surgical masks are manufactured from the heat-sensitive material and should not be resterilized. While PPE protects an individual when it is being worn, incorrect technique of removal (doffing) and incorrect disposal of contaminated PPEs can expose the wearer and other people to virus. Hence, proper doffing and disposal is key to prevent exposure. If reusable PPE suit is available, care should be taken during doffing, cleaning, and repacking for sterilization. It is highly desirable to use PPE suit that has undergone quality control testing and is certified by competent authorities like National Institute for Occupational Safety and Health (NIOSH).
The following points must be considered for decontamination:
Virucidal effect of disinfection method: measured as log reduction in viral load (three log10 reduction indicates reduction in viable virus number by 1,000 times).
Quality of filter: The filter resistance should not increase as it makes it hard to breathe. At the same time, the filter should block at least 95% of airborne particles.
Mask fitting: There should not be a significant change in the shape of mask, and the elastic quality of the strap should be maintained to allow tight fit. This is tested using smoke or fragrance ideally. The wearer should not be able to smell it, if the mask fit is good. Detailed procedure for the assessment of mask-fit is beyond the scope of this article. Readers are referred to the Occupational Safety and Health Standards recommendations. 48
One simple strategy, not requiring sterilization, is to issue five such N95 respirators to each HCW on the first day. These can be numbered and one FFR is used every day. At the end of each shift, the respirator is carefully removed (considering it is contaminated) and stored in a breathable paper bag. The virus is unlikely to survive after 72 hours; hence, the first mask can be safely reused on the sixth day. Additionally, they should wear a three-ply mask over FFR to protect it from contamination. Face shield over the disposable respirator prevents surface contamination. 49
UK government recommends folding the mask to keep the outer surface inward and against itself and to reduce likely contact with the outer surface during storage in a clean sealable bag/box marked with the person's name and stored in a well-defined place. 50
While donning the FFR and performing a seal check, a pair of clean nonsterile gloves should be used. 51 Degesys et al. demonstrated high failure rate of used duckbill-shaped (Kimberly-Clark 46727 and Halyard 46867) N95 FFR in relation to the mask-fit. 52
Typically, HCW uses his own FFR for repeat use. The FFRs, which are soiled, damaged, or hard to breathe with, should be immediately discarded. FFR used during aerosol-generating procedures or close contact with the infected patients requiring contact precautions should be discarded. 51 Tie-on masks, difficult to remove without damaging, are discarded. Most FFRs have elastic ear hooks and can be considered for reuse. It is prudent to perform hand hygiene before removing the facemask and after keeping it in the designated place. Procedures for resterilization of contaminated FFRs and the supporting evidence are summarized in Table 6 .
Centers for disease control and prevention (CDC)-approved methods for decontamination are vaporous hydrogen peroxide (HPV), UVGI, and moist heat sterilization. 53 Some institutes in the United States are using hospital-grade UV treatment. 54 Household UVGI sterilization cabinets are NOT RECOMMENDED for use. 55 Ozone is another promising method for sterilization. 46 It has faster virucidal action and causes slower degradation of FFR. Unlike UVR, ozone easily reaches the crevices of mask. Previously, ozone in concentration of 27.73 mg/L was shown to inactivate SARS-CoV-1 virus within four minutes. 56 In summary, disposable N95 FFR can be resterilized by hydrogen peroxide vapor, UV radiation, moist heat, dry heat, and ozone gas. Methods such as soap water, alcohol, bleach immersion, EtO, ionizing radiation, microwave, high temperature, autoclave, or steam should be avoided. 46
The process of sterilization can be monitored with various mechanical, chemical, and biological indicators which ensure compliance to specific conditions of the sterilization process. However, they do not confirm sterility. Thermometers can be used to record the temperature of the sterilization cycle. Chemical indicator tapes change color and can distinguish sterilized packets from the one which are yet to be processed. Biological indicators in the form of nonpathogenic spore-forming heat-resistant bacteria are most accurate for checking sterilization effectiveness. Disinfectants concentrations (e.g., chlorine percentage in hypochlorite solution) can be checked if facilities are available. It is preferred to use certified consumables. Visual inspection is not a reliable method of assessment of cleanliness. Ultraviolet marker pens can be used to make marks on the surfaces, which are frequently touched, known as “high-touch objects.” These marks are not seen with the visible light but are fluorescent under a near-UV light known as black light. These fluorescent marks disappear with cleaning and hence can be used to monitor sustained improvement in cleaning. 57,58
Prevention of transmission of infectious diseases to patients and healthcare workers is a top priority, particularly during the pandemic. Healthcare workers should understand the criticality of the equipment and also the concepts of bioburden, sterilization, disinfection, cleaning, and Asepsis. Checking compatibility of the “anti”-COVID methods of sterilization/disinfection with the equipment (based on manufacture's recommendation) avoids damage to the equipment and ensures its longevity. Environmental surface decontamination is an important strategy during COVID-19. The reuse of single-use PPE like disposable face shield N95 FFRs is possible, provided the recommendations are followed stringently. Resterilization of single-use (PPE) suit and three-ply surgical mask should be avoided due to the presence of heat-sensitive material and lack of evidence suggesting appropriateness of its sterilization/decontamination.
Source of support: Nil
Conflict of interest: None
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