By Rod Webb, JD
Room disinfection using hydrogen peroxide (HP) "fogging" methods has been shown to eradicate or significantly reduce methicillin-resistant Staphylococcus aureus (MRSA),1-2 Clostridium difficile (C. diff),3-4 vancomycin-resistent Enterococci (VRE),5 and Acinetobacter baumanni6 in healthcare settings. These fogging methods include "dry gas,"2 "dry mist,"4 "microcondensation,"1, 3, 5 and "activated,"6 also known as ionized hydrogen peroxide (iHP). Hydrogen peroxide (HP) fogging decontamination has recently gained notice in healthcare institutions due to its many benefits such as superior efficacy, safety and materials compatibility. HP fogging can be an essential intervention to rapidly reduce transmission of healthcare-associated pathogens.10 One hospital study reports a 53 percent reduction of hospital-wide incidence of C. diff using HP fogging.3
Despite the benefits of HP fogging, its use has been limited to isolated outbreaks and not widely adopted for routine disinfection of patient care areas. One reason is that CDC guidelines recommend against using disinfectant fogging methods.7-8 However, these guidelines contemplated fogging using quaternary ammonia, phenolics, formaldehyde, hypochlorite solutions or other disinfectants that are harmful, not effective, and/or impractical for healthcare environments.9 Additionally, long process times, cost of equipment and inconvenient operation have been barriers.15
The prevailing approach for reducing environmental surface pathogens is programmatic manual cleaning focused on high-touch surfaces, but this approach has practical challenges as well:
- Not all environmental surfaces are targeted, and even cleaning of high-touch surfaces is susceptible to human error. Interventions not effectively targeting all environmental surfaces leave reservoirs of pathogens.17
- Training and oversight in an increasingly overburdened, under-resourced work environment may prove daunting and difficult to sustain. Low hand hygiene compliance is a current example of just how difficult. One study reports only a 50 percent compliance rate in the U.S. even after years of publicity, education, training, product innovations and other efforts.18
- There is no data showing the impact of cleaner surfaces to environmental pathogen levels or their transmission.11-12
- There is no cost-benefit analysis showing the financial value of programmatic manual cleaning.
As HP fogging leaves virtually no reservoir of pathogens on treated surfaces, and as equipment and processes are optimized for faster process times, reduced disruption and lower-cost, broad adoption as a valued intervention will follow.
The 2003 Guidelines for Environmental Infection Control in Health-Care Facilities from the Centers for Disease Control and Prevention (CDC) states, ". cleaning and disinfecting environmental surfaces as appropriate is fundamental in reducing their potential contribution to the incidence of healthcare-associated infections."7 This statement is made in the context of applying to all environmental surfaces to minimize transmission of infections by hand. However, high-touch housekeeping surfaces (e.g., doorknobs, bedrails, light switches, wall areas around the toilet in the patients room, and the edges of privacy curtains) should be cleaned and/or disinfected more frequently than [other] surfaces."7 At the time of drafting these guidelines, it was believed contaminated surfaces did not contribute significantly to healthcare-associated infections.7 Recent studies indicate otherwise, and the industry struggles with what type of cleaning is "appropriate," particularly for high-touch surfaces, and how is cleanliness assessed. So far, manual wipe cleaning is the prevailing practice and quality is assessed by visual observation. More recently, programmatic regimens with covert, qualitative marking methods have been developed. The limitation of either method is a visually clean surface does not necessarily equate to a pathogen clean surface or reduction in infection rates.11, 13
Programmatic regimens produce cleaner surfaces with less variation in controlled studies, but questions remain if they can be implemented for broad, measurable and sustained impact in an increasingly regulated and understaffed industry.11 Process control is a serious practical consideration. Further, there most certainly is an associated cost that is not documented and, perhaps more importantly, because these programs only focus on high-touch surfaces and are not 100 percent effective even then, a reservoir of pathogens will remain and can survive on surfaces for months.17, 19 So while surfaces are cleaner, there may be little correlation to reduced infection rates.
In contrast, HP fogging is highly effective against known healthcare-related pathogens and is used to safely disinfect all environmental surfaces. Equipment today is easily programmed and reliably operated with minimal training and supervision. Surface coverage is complete and uniform and is immediately confirmed using chemical indicator strips that turn color upon exposure to HP. These characteristics make HP fogging a low-risk alternative to programmatic cleaning regimens. Costs are being reduced as more competitors enter the market, equipment is optimized, and process times are shorter.
HP fogging was developed by the American Sterilizer Co. as a "dry gas" process in the late 1970s, and in 1989, successfully decontaminated an ultracentrifuge.14 STERIS Corp. acquired the technology and continues to offer various products using the dry gas process. In the late 1990s, Bioquell developed a "microcondensation" decontamination process and today offers the Clarus line of products. The "dry gas" and "microcondensation" processes have dominated the room decontamination market for the last decade, primarily in the pharmaceutical market. Sterinis provides a "dry mist" method and is seeking EPA approval of its chemical for launch in the U.S by Advanced Sterilization Products. SixLog Corp. offers the ionized hydrogen peroxide process, also known as iHP. All processes are highly effective at reducing various healthcare-associated pathogens by 91 percent to 100 percent.1-4, 6 While there are differences in the disinfection delivery methods of the various systems, the high efficacy of each process is likely more an indication of the effectiveness of HP as a biological killing agent than the process by which it is generated and delivered to the surface. The substantive differences between the processes are the extent to which they are optimized in terms of cost, convenience, reliability of operation, and process time.
Process time and cost are the primary distinguishing characteristics of the various fogging methods. Since process time impacts cost and operational convenience, much effort has been expended to reduce process time, which currently stands at two to four hours or more depending on the room size and method used. Most facilities desire a room turnover time of less than one hour (unpublished data) although at least one study indicates this aggressive schedule is not adhered to currently and some rooms in a busy hospital stay vacant for hours after cleaning and available for occupancy.15
iHP is the most recently developed method, and it achieves a compelling balance between process times of 1 to 1.5 hours and an efficacy of 99.98 percent reduction.6 However, additional investigation should be performed to confirm if this balance is maintained across the spectrum of pathogens in healthcare settings. A review of how iHP works provides a better understanding of this performance.
Similar to all hydrogen peroxide fogging methods, iHP starts with a liquid solution that is flowed under pressure through a nozzle device to create a fine mist sprayed into the air. Unlike other methods, there is no need to pre-condition the area, which adds to the process time. The mist must stay suspended in the air in order to uniformly disperse to exposed surfaces. iHP uses the novel process of ionization to rapidly disperse the disinfectant. Immediately after the mist droplets exit the nozzle and before they become airborne, the droplets pass through a cold plasma arc created between two high energy electrodes at 17,000 volts. This causes the droplets to become ionized, or charged with the same polarity. Ionizing causes the droplets to be mutually repulsive, like trying to attach the same-polarity ends of magnets together, which will never touch, and, in fact, actively move away from each other in a repulsive action. By the same token, the droplets become attracted to opposite polarity surfaces floating in the air or settled on surfaces. Continuing with the analogy, the droplets act like the opposite poles of magnets, they actively seek the other surface. If the surface happens to be a microorganism like a cell, spore or fungi, the droplet attaches to it, whereby the hydrogen peroxide oxidizes the walls exposing the nuclei, and kills it on contact. One advantage of iHP, therefore, is the active manner and speed with which the mist droplets are dispersed to surfaces.
A second effect of ionizing hydrogen peroxide is the acceleration of the activating, breaking apart or disassociation of the constituent antimicrobial components from the hydrogen peroxide. Activation creates one or more highly reactive antimicrobial agents such as hydroxyl radicals, reactive oxygen species, reactive nitrogen species, ozone and ultraviolet. These agents kill the microorganism. The more agents that are created by the activation process, the more effective the killing action is. Hydrogen peroxide activates naturally upon exposure to oxygen, or it can be activated chemically using peracetic acid or other chemical, but these reactions take time and they may not create a high number of these antimicrobial agents. iHP activation takes place in about one second and creates all of the antimicrobial agents in high concentrations. While it does take time for the iHP droplets to travel from the nozzle to exposed surfaces and uniformly cover them, the microorganisms are killed upon contact and additional time is not needed for natural or chemical activation to take place.
All HP fogging methods require aeration of the treated area after disinfection to reduce the hydrogen peroxide concentration below regulated levels. iHP offers speed advantages here as well. Because the activation process for iHP is fast and efficient, the maximum concentration of hydrogen peroxide in the treated space during the process is very low at approximately 200 ppm or less. The lower this concentration of hydrogen peroxide, the less time needed for aeration. Aeration is achieved in most healthcare settings by circulating the room air through activated carbon media to capture airborne residual hydrogen peroxide. After aeration, the room can be occupied.
HP fogging provides high efficacy for the disinfection of healthcare-related pathogens on all exposed environmental surfaces. Historically, its use has been limited for disinfection of critical rooms and equipment after a confirmed outbreak as a control intervention but has not proven feasible for routine room disinfection due to long process times. Recently, however, new methods like iHP offer faster processing with high efficacy and reduced cost. As such, HP fogging can be an effective prevention strategy for routine disinfection of patient care areas. Equipment operation is automated through touch screen computer control and coverage is verified by chemical indicators placed on surfaces which turn color upon exposure to the HP mist. The process is virtually fail safe, reliable and, once integrated into facility operations, requires little oversight.
One disadvantage of HP fogging is that the room cannot be occupied. This creates a challenge when disinfecting double occupancy rooms after discharge of one patient and not the other. Possible solutions include coordinated planning of discharge schedules to minimize single occupancy of double rooms, moving the remaining patient to another area while the process is performed, sealing the vacant area from the occupied area by impermeable screens during fogging, or performing manual disinfection in these limited cases. Further investigation of these or other options is warranted.
Visual organic contamination must be removed from the surface to ensure adequate contact by the hydrogen peroxide disinfectant fog to microorganisms. It is expected that current housekeeping cleaning efforts are sufficient as some surface contamination is tolerable without impacting efficacy, but adequacy of current cleaning levels should be confirmed through additional investigation.
Further investigation should be conducted to compare the long-term feasibility of hydrogen peroxide fogging versus programmatic manual cleaning regimens. Investigation should compare direct and indirect costs of developing, implementing and sustaining each approach, the effect on pathogen transmission and infection rates, and cost savings resulting from the reduction, if any, in infection rates.
Rod Webb is corporate development manager for Astro Pak Corp. He has 15 years of experience in contamination control practices and testing technologies in aerospace, hydraulics, automotive, semiconductor and laser industries and has authored numerous articles on contamination control. He has a law degree from Oklahoma City University School of Law and an economics degree from Southwestern Oklahoma State University. Astro Pak Corporation is the parent company of SixLog Corp.
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