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3 Designing and Engineering Effective PPE Healthcare workers need to feel confident that the personal protec- tive equipment (PPE) they are being asked to use during an influenza pandemic will be reliable in reducing their risk of infection. Further, the equipment needs to be effective in a work environment that involves in- teraction with and examination of patients and long working hours in a crisis pandemic situation. As discussed in Chapter 1, PPE is one compo- nent of an overall systems approach to infection prevention and control, which during an influenza pandemic will also require environmental and policy measures including vaccination of healthcare workers, use of anti- viral medications, isolation precautions, and ventilation and air exchange controls. This chapter begins by setting out a proposed framework for the de- sign and development of PPE for healthcare workers that will facilitate greater interaction between the end users, designers and manufacturers, and standards and certification agencies. The discussion then focuses on specific research opportunities for enhancing the current generation of PPE and concludes by identifying next steps in the design and develop- ment of PPE. The chapterâs recommendations focus on innovative and systematic approaches to the design and engineering of healthcare PPE. FRAMEWORK FOR PPE DESIGN AND DEVELOPMENT A formal framework for the design and development of PPE encom- passes the three phases typically associated with a productâs life cycle: user requirements analysis, design realization, and field use and evaluation. 77
78 PREPARING FOR AN INFLUENZA PANDEMIC Key Design Drivers The design and development of PPE are influenced by the key factors shown in Figure 3-1. Since meeting the regulatory standards is manda- tory and not optional, the design and development of PPE often involve major compromises while attempting to simultaneously achieve a maxi- mal degree of protection with the highest level of comfort at the lowest possible cost. For example, the degree of protection provided by protec- tive clothing, such as a gown, can be considerably enhanced by the use of polyethylene film without substantial additional expense, but at a sig- nificant loss of comfort for the user. On the other hand, a high degree of protection and comfort can be achieved, but at a much higher cost, by using a breathable impervious nonwoven material (Pasko, 2007). Thus, although materials and manufacturing technologies exist that can maxi- mize any one design driver, designing the product to achieve the appro- priate balance is ultimately dictated by the requirements of the end user. As will be described in Chapter 4, a number of barriers and reasons have been identified by healthcare workers regarding why they choose not to wear PPE. These reasons include not having enough time to don the equipment (particularly in emergency response situations), the equipment is not available or they have not received training, the equip- ment is uncomfortable or difficult to use, the equipment interferes with their interaction with the patient and affects dexterity or the ability to perform a medical procedure, or they do not see the situation as a high risk. Better guidance is required on the unique needs of healthcare work- ers so that appropriate performance requirements can be developed and Degree of Protection Cost Comfort Regulations Regulations FIGURE 3-1 The design drivers for PPE.
DESIGNING AND ENGINEERING EFFECTIVE PPE 79 manufacturers can design and supply PPE to meet the specific needs of this workforce. Moreover, since the design (or solution) space is fairly large, it is possible to produce a large number of variations of the same item of PPE, thereby driving up its cost. By developing PPE based on a prescribed set of evidence-based performance requirements or standards, manufacturers will be able to create products that will be less expensive and more effective; such standards will also enhance compliance in the use of PPE since they will minimize, if not eliminate, the errors typically associated either with the selection of PPE by personnel responsible for PPE procurement in healthcare settings or with its use by healthcare workers themselves. Healthcare workers will be assured that they are receiving the right level of protection in the work- place. To realize this objective, there is a need for a structured design and development process for PPE, as well as thorough testing and certification efforts (Chapter 5). User Requirements AnalysisâData Collection for Design In the first phase of the design and development process, the re- quirements of the end user (i.e., the healthcare worker) should be as- sessed. The first step is to gain an understanding of the hazards and risks associated with the use of PPE in specific environments as well as to un- derstand the barriers to PPE use, particularly in emergency response and crisis situations in patient care (Chapter 4). A clear understanding of the threat will help establish the degree of protection the PPE must meet or exceed. In the case of an influenza pandemic, this calls for an under- standing of the nature of the influenza virus, its infectivity, and its modes of transmission (Chapter 2). A related factor that should be considered is the risk posed by the environment in which the healthcare worker must operate. The continuum of risk is not clearly defined for influenza be- cause so little is known about the routes of transmission of the virus be- tween individuals. Further, the many unknowns concerning the nature and level of infectivity of the influenza virus create challenges for de- signing effective prevention measures. Unlike many industrial exposures for which adverse health effects are the result of exposure to large concentrations of a chemical or other hazardous agent, infectious diseases (such as tuberculosis) may be spread by small numbers of bacilli or viruses.
80 PREPARING FOR AN INFLUENZA PANDEMIC As discussed in Chapter 4, research is needed that will provide a haz- ard assessment with insights into whether specific procedures or work situations (e.g., nebulization, endotracheal intubation, bronchoscopy, endotracheal suctioning, cleaning patientsâ rooms) place healthcare workers at higher levels of risk of influenza infection. According to the 2006 interim guidelines for an influenza pandemic, N95 respirators are recommended for healthcare workers in caring for patients with con- firmed or suspected influenza or in situations, such as bronchoscopy or resuscitation, that are likely to generate infectious respiratory aerosols (CDC, 2006). McCullough and Brosseau (1999) present a qualitative framework for the selection of respirators for the control of worker expo- sure to infectious aerosols, especially in situations where information on occupational exposure limits, toxicity, and airborne concentrations is absent. As stated in Chapter 2, information on the modes of transmission of the influenza virus is scarce and this type of qualitative approach may be valuable in assessing the risk in the healthcare setting during a pan- demic. The authors urge that assessments be conducted by industrial hy- gienists or other trained professionals. In developing evidence-based performance requirements, the ideal data acquisition process would involve use of the PPE component in the field and assessing the requirements; however, in the event this is not feasible, the data acquisition process should, at the very least, simulate the real-world usage of the specific component of the PPE ensemble. For instance, the healthcare worker will sweat during the course of normal day-to-day activities, and this in turn will affect the performance of the PPEâthe respirator may change its position on the userâs face or the gown may become increasingly uncomfortable if it does not effectively wick away perspiration from the userâs skin. Therefore, a treadmill or similar method can be used to simulate the use of PPE components to better understand and determine their performance requirements. The next step is to identify the key characteristics that should be con- sidered in the design of the PPE component. As shown in Figure 3-2, these involve considerations of function, use, comfort and wearability, durability, maintenance and reuse, aesthetics, and cost.
DESIGNING AND ENGINEERING EFFECTIVE PPE 81 Evidence-Based Performance Requirements Functionality Usability Comfort and Wearability Durability â¢ Protect against â¢ Maintain biomechanical â¢ Comfortableâno skin â¢ Adequate wear life influenza virus efficiency and sense of touch irritation or pressure â¢ Strengthâtear, â¢ Guard against and feel points tensile, burst contact with â¢ Odor-free â¢ Prolonged use â¢ Abrasion resistance contaminated â¢ Hypoallergenic without discomfort â¢ Corrosion fluids and â¢ Accommodate wide range of â¢ Breathableâair resistance aerosols users (face and body profiles) permeable â¢ Compatability across various â¢ Moisture absorbentâ elements of the PPE wickability ensemble and with other â¢ Low bulk and weight equipment (e.g., stethoscope) â¢ Dimensional stabiltiy â¢ Non-startling to patients and â¢ Easy to put on and families take off (don and doff) â¢ Facilitates communication with others (verbal, facial) Cost Maintenance and Aesthetics â¢ Product cost Reuse â¢ Total life-cycle â¢ Variety of styles cost â¢ Easy to and colors â¢ Minimal environ- decontaminate and â¢ Customizable mental impact discard disposable elements â¢ Easy to clean and replace parts in reusable PPE FIGURE 3-2 A structured approach to evidence-based performance requirements. For example, protection against the influenza virus and guarding against splashes and contact with bodily fluids are the major functional requirements of PPE. However functionally effective the PPE may be, it is unlikely to be used regularly in the field if the efficiency of the user in carrying out his or her task is impaired by the PPE. PPE should not affect the biomechanical efficiency (work and energy) of healthcare workers, especially since they rely on extensive interaction with the patient and must be able to hear the patientâs respiration and heartbeat, touch and feel the patientâs body, and so on. The PPE should be odor-free and hy- poallergenic and should comfortably fit a variety of body forms includ- ing facial profiles. Its appearance should not startle patients, especially younger children. It should also facilitate verbal and facial communica- tion with patients. User instructions that accompany PPE products should clearly specify appropriate practices to promote their correct usage. In terms of comfort and wearability, the PPE should be comfortable to wear during work activities and should not have any pressure points or cause skin irritation. It should be breathable and have good moisture absorp-
82 PREPARING FOR AN INFLUENZA PANDEMIC tion. It should be lightweight and have excellent dimensional stability since it will be subjected to extensive stresses and strains during wear. It should be easy to put on and take off (don and doff), especially in a very short period of time. It should be durable, with the wear life depending on the type of ensemble (e.g., gown, respirator), and should be of sound construction to prevent or minimize damage due to tear, tensile, and puncture deformations. Careful consideration should be given to the trade-offs between disposable and reusable PPE, particularly given the extreme demands that would be placed on a disposable PPE supply in an influenza pandemic. Maintenance and reuse are key factors for consid- eration in developing performance requirements (IOM, 2006). Minimiz- ing the environmental impact of PPE cleaning or discard should also be considered. The PPE should be customizable to meet the wearerâs aes- thetic needs including those of style and color. Finally, the product cost and the total life-cycle cost should be specified as part of the require- ments analysis. A similar user requirements analysis process has been employed successfully in the design and development of the Wearable Motherboard or Smart Shirt, an intelligent garment for biomedical moni- toring (Rajamanickam et al., 1998; Park and Jayaraman, 2003). Design RealizationâDesign and Engineering The second step in the framework is realization of the design by translating the evidence-based performance requirements into the spe- cific design of the PPE component in light of the regulatory requirements as shown in Figure 3-3. This part of the process begins with making appropriate trade-offs between the design drivers of degree of protection, comfort, and cost for the specific PPE component being designed. Once this âdegree of protection-comfort-costâ solution space has been established, appro- priate materials and manufacturing processes need to be chosen. For example, the level of required filter efficiency will determine the choice of materials and specific treatments during the manufacturing process for a respirator. Similarly, appropriate finishing treatments should be chosen
DESIGNING AND ENGINEERING EFFECTIVE PPE 83 Evidence-based Manufacturing processes performance requirements FMEA Degree of protection- Field-testing of comfort- cost solution space PPE component Regulations Materials Define the Determines the Results in the selection of Failure modes and effects analysis FIGURE 3-3 PPE design life cycle: evidence-based performance require- ments through field testing. to provide the required degree of thermal comfort for gowns to ensure the comfort of the healthcare workers who are using them. The potential modes of failure of the PPE component in the field should be anticipated and the product suitably designed to guard against such failures. A for- mal failure modes and effects analysis process should be adopted to en- sure the robustness of the resulting design. This process is aimed at proactively identifying where and how equipment and processes might fail and focusing on where changes are needed (IHI, 2007). Field Use and Evaluation: Product in Use As shown in Figure 3-3, and discussed in Chapter 5, in the final phase of the framework, the developed PPE component should be tested and evaluated in the field for a realistic assessment of its performance and to monitor any unintended consequences of use. For respirators, this will necessitate the integration of field testing into the certification proc- ess. During this field testing, the product should be subjected to the vari- ous failure modes identified earlier as part of the FMEA process. Protocols should be put in place to obtain feedback from users during the testing, and these inputs should be used to refine and enhance the design. For example, an ongoing study of the tolerability of various respirators and respirator-mask configurations should provide valuable insights into real-world usage (Radonovich, 2007). Once the product has been placed in service, appropriate mechanisms should be established to obtain continuous feedback on its performance. Programs should be instituted to ensure compliance with the right use of the right PPE for the right level of risk.
84 PREPARING FOR AN INFLUENZA PANDEMIC In summary, the proposed formal PPE development framework calls for a greater degree of input and collaboration between the various stakeholders associated with PPEâthe users (i.e., healthcare workers), the designers and manufacturers, and the regulatory or certification agencies (i.e., the National Institute for Occupational Safety and Health [NIOSH], the Food and Drug Administration [FDA], and the Occupa- tional Safety and Health Administration [OSHA]) responsible for certify- ing and approving PPE. Such a systems and iterative approach will lead to the development and deployment of effective and wearable PPE that can be used in the range of healthcare settings from patientsâ homes to hospitals to long-term care facilities. The remainder of this chapter identifies a set of research opportunities to enhance the current genera- tion of PPE and spur the innovations that will result in a new generation of protective equipment. RESPIRATORY PROTECTION: RESEARCH NEEDS The fundamental principle for making decisions regarding the selec- tion and use of respiratory protection is to understand the nature of the hazard and the risks that the wearer is expected to encounter when wear- ing that protection. While there is extensive knowledge regarding the efficacy of respiratory protection, little is known about the extent to which aerosol transmission contributes to the overall risk of infection by the influenza virus. Therefore, the most critical research need regarding respiratory protection for healthcare workers, as discussed in Chapter 2, is accurately defining the modes of transmission of the influenza virus and the likelihood of infection by each route. Lacking this knowledge, the selection and use of appropriate respiratory protection is qualitative and subject to opinions regarding acceptability of risk. Respiratory protection will be necessary in an influenza pandemic if there is a likelihood of aerosol transmission. If properly selected and used, respiratory protection has been demonstrated to significantly re- duce hazardous exposures. However, much of this work has been con- ducted in industrial settings and has focused on chemical exposures. When compared to no respiratory protection, Barnhart and colleagues (1997) estimated that the use of respiratory protection reduces risks of skin test conversion for tuberculosis by the following proportions: surgi- cal mask, 2.4-fold; disposable dust, fume, mist, or high-efficiency par- ticulate air filtering (HEPA) mask, 17.5-fold; elastomeric HEPA
DESIGNING AND ENGINEERING EFFECTIVE PPE 85 cartridge respirator, 45.5-fold; or powered air-purifying respirator (PAPR),1 238-fold. Teleman and colleagues (2004) found that the consis- tent use of N95 filtering facepiece respirators by healthcare workers for contact with severe acute respiratory syndrome (SARS) patients was strongly protective regarding risk of SARS infection (OR [odds ratio] 0.1, 95% CI [confidence interval] 0.02 to 0.86). A limited number of studies have looked at the effectiveness of PPE in other infectious dis- ease situations (Table 1-4). As discussed in Chapter 1, NIOSH has authority to define the con- struction and performance of respirators and to certify respirators for use that meet those requirements (NIOSH, 2004a); OSHA regulates the use of respirators in the workplace (OSHA, 1998). The FDA has regulatory authority to provide manufacturers with the approval to market respirators and other PPE (e.g., gowns, gloves) that will be used in patient care. Additionally, the American National Standards Institute (ANSI) has issued a consensus standard on the use of respira- tory equipment that is relevant to the use of respirators in the healthcare setting (ANSI, 2001). Respirators approved by NIOSH for protection from aerosols are broadly categorized by whether they are air purifying or air supplying.2 The types of respirators that have been designated for use against in- fluenza (CDC, 2006; OSHA, 2007b) are negative-pressure3 air-purifying respirators or PAPRs. For negative-pressure air-purifying respirators, the level of protection from aerosol exposure is primarily a function of leak- age through the faceseal due to the negative pressure created inside the facepiece of these respirators when the wearer inhales. Penetration may also occur through the respirator filter media. For a PAPR, the level of protection is primarily a function of the flow rate of air into the facepiece and secondarily of the efficiency of the filter. Respirators worn by healthcare workers will not only protect them, but may also reduce the spread of disease from one patient to another (via the healthcare worker) or from an infected but asymptomatic healthcare worker. Determining whether exhaled air from workers needs to be filtered is a critical re- 1 In this report, the term PAPR is used to refer to loose-fitting devices unless otherwise specified. 2 Air-purifying respirators use a filter, cartridge, or canister to remove air contaminants (ambient air passes through the air-purifying element). Air-supplying respirators supply the user with breathable air from a source independent of the ambient air (OSHA, 2007a). 3 Air pressure inside the facepiece during inhalation is lower than the ambient air pres- sure; this allows air to flow through the filter and into the facepiece.
86 PREPARING FOR AN INFLUENZA PANDEMIC search item. For filtering facepieces, this is accomplished by the elimina- tion of an exhalation valve, but there is no current solution for PAPRs. Medical masks are not designed to offer respiratory protection to the wearer (Chapter 1). These masks protect patients from droplets in the wearerâs exhaled breath and are not intended to fit tightly on the wearerâs face or to be constructed of high-efficiency filter media. Medical masks may serve to provide a barrier to infectious droplets but are not consid- ered respiratory protection. In the aftermath of the SARS outbreaks, re- searchers have conducted several studies to examine the level of protection that medical masks may provide to the wearer (for example, Balazy et al., 2006b; Li et al., 2006b). Further research is needed to clar- ify the role of medical masks in providing barrier protection during an influenza pandemic as these masks are widely available and will be ac- cessible to healthcare workers and to the general public. Enhancing the Fit Faceseal leakage is the most critical factor in the ability of a respira- tor to protect the wearer from exposure to airborne contaminants. OSHA requires that respirators be qualitatively or quantitatively fit tested before they are used (OSHA, 1998). Three important components of a respira- tory protection program are selecting the right size and shape for the wearerâs face, confirming fit by testing, and proper and consistent use of the respirator when worn. The fit factor (FF) is the fundamental parame- ter describing the effectiveness of the quality of the seal between the res- pirator and the wearerâs face and is defined as the reciprocal of the fraction of the contaminant concentration entering a respirator through leaks. The fit factor is measured and determined by fit testing, which can be conducted using quantitative or qualitative methods. Qualitative methods rely on the wearer to detect the presence of the challenge agent inside the respirator by smell or taste. Quantitative testing methods measure the amount of leakage of the contaminant into the respirator facepiece and include test aerosol, ambient aerosol, and dynamic nega- tive-pressure tests. Filtering facepiece and half-mask respirators can be tested by both methods. However, full-face respirators and tight-fitting PAPRs must be tested by quantitative methods. Fit testing and training on how to don, wear, and doff a respirator have been shown to increase the protection provided by the respirator while in use. One-on-one and classroom training significantly increase fit test pass rates compared to no training at all (Hannum et al., 1996).
DESIGNING AND ENGINEERING EFFECTIVE PPE 87 After conducting aerosol ventilation studies using technetium-99 (99mTc), Huff and colleagues (1994) found that personnel wearing fit-tested respi- rators had significantly lower counts from radiation contamination (disin- tegrations per minute) on nasal swabs than those wearing respirators that were not fit tested or medical masks. Other studies have shown that fit testing increases simulated workplace protection factors for elastomeric and filtering facepiece respirators (Coffey et al., 1999, 2004; Lawrence et al., 2006). In focus group discussions, healthcare workers during the SARS outbreaks expressed concerns about the variability be- tween fit testing and training methods used by different healthcare facili- ties (Yassi et al., 2004). Increased standardization of fit testing and training methods should be explored as should simpler, more efficient methods of fit testing. In use, the efficacy of the faceseal can vary greatly and may not nec- essarily be related to the fit factor as determined by fit testing. The mini- mum acceptable level of fit under these use conditions is the assigned protection factor (APF). The APF is defined as the anticipated level of protection provided by the respirator (based on supplying properly fitted and functioning respirators to a given percentage of trained users) (Bollinger, 2004). APFs are based on the analysis of workplace protec- tion factor (WPF) and simulated workplace protection factor (SWPF) studies (Coffey et al., 2004); the higher the APF value, the greater is the expected level of respiratory protection. OSHA, NIOSH, and ANSI have defined APFs for classes of respirators based on facepiece type and res- piratory inlet covering (Table 3-1; OSHA, 2006). The actual level of protection provided by respirators when worn un- der various work conditions is measured by the total inward leakage (TIL). This is the sum of the leakage through filters, respirator compo- nents (exhalation valves), and facesealsâfaceseal leakage being the most critical and variable factor. The TIL for various models within a respirator class or type has been shown to vary significantly, and some models have measured penetration values greater than 10 percent. Coffey and colleagues (1999) found significant variation in SWPFs of 21 N95 filtering facepiece respirators. Similarly, a study of 18 N95 filtering facepiece respirators found that 5th percentile SWPFs without fit testing ranged from 1.3 (indicating virtually no protection) to 48.0; fit testing was found to increase protection (Coffey et al., 2004). A TIL study using a standard European test method (EN 13274-1) found that half-mask elastomeric facepiece respirators had less leakage than filtering facepiece respirators and that leakage was significantly different between classes of
88 PREPARING FOR AN INFLUENZA PANDEMIC filtering facepiece respirators (Han and Lee, 2005). Lawrence and col- leagues (2006) compared SWPFs for 15 models of elastomeric N95 res- pirators, 15 models of filtering facepiece N95 respirators, and 6 models of medical masks. The 5th percentile SWPFs of 7 for elastomeric N95 respirators, 3 for filtering facepiece N95 respirators, and 1 for medical masks were all significantly different. There were also significant differ- ences among the models of filtering facepiece N95 respirators and medi- cal masks. The results of these studies indicate that filtering facepiece TABLE 3-1 OSHA APF Valuesa Type of Respiratory Inlet Covering Helmet Loose- Quarter Half Full or Fitting Class of Respirator b,c Mask Mask Face Hood Facepiece Air purifying 5 10d 50 â â Powered air purifying â 50 1,000 25/1,000e 25 Supplied air (airline) Demand mode â 10 50 â â Continuous flow â 50 1,000 25/1,000e 25 Pressure demand â 50 1,000 â â SCBA Demand mode â 10 50 50 â Pressure demand â â 10,000 10,000 â NOTE: SCBA = self-contained breathing apparatus. a These APFs do not apply to respirators used solely for escape. b Employers may select respirators assigned for use in higher workplace concentrations of a hazardous substance for use at lower concentrations of that substance or when required respirator use is independent of concentration. c The APFs are effective only when the employer implements a continuing, effective res- pirator program as required by 29 CFR 1910.134, including training, fit testing, mainte- nance, and use requirements. d This APF category includes filtering facepieces and half masks with elastomeric facepieces. e The employer must have evidence provided by the respirator manufacturer that testing of these respirators demonstrates performance at a level of protection of 1,000 or greater to receive an APF of 1,000. This level of performance can best be demonstrated by perform- ing a WPF or SWPF study or equivalent testing. Absent such testing, all other PAPRs and SARs with helmets or hoods are to be treated as loose-fitting facepiece respirators and receive an APF of 25. SOURCE: OSHA, 2006.
DESIGNING AND ENGINEERING EFFECTIVE PPE 89 N95 respirators may not provide the same level of protection and may provide less protection than elastomeric half-mask N95 respirators. Im- provements are needed in N95 technology; research and development efforts should focus on a new generation of respirators that can meet im- proved efficacy and comfort standards. As noted in the Han and Lee study cited earlier, many European countries measure TIL as part of their respirator certification process (European Standards, 2001). NIOSH is working to incorporate the TIL measure into its certification process (NIOSH, 2004a,b). The benefit of such a test protocol would be twofold; first, it would require that certified respirators demonstrate the ability to provide an effective faceseal under use conditions, and second, it would provide end users with data to compare the effectiveness of respirators and guide respirator selection (Lee et al., 2004). Thus, there is a need for the development of a validated set of meas- ures, including TIL, that would provide end users with an easy-to- understand method of comparing respirators and would enhance in- formed decisions on selecting respirators commensurate with the as- sessed risk and desired level of protection. Long-term goals for comparison metrics would include comparisons with other evidence- based requirements such as breathing resistance, ability to interface with medical devices, and other performance requirements shown in Figure 3-2. The variability of protection demonstrated in the studies described above also indicates the need to develop a new generation of respirators that provide more effective and consistent faceseals. Filtering facepiece N95 respirators can lose their original shape or structural integrity after they are worn for extended periods or are repeatedly donned and doffed, and it is possible that the effect of these conditions could compromise the level of protection provided by the respirator. Research is needed on in- novative approaches (including shape memory polymers discussed later in this chapter) that can easily achieve an effective faceseal for long-term use, possibly without the need for extensive fit testing. Defining Occupational Exposure Limits The maximum use concentration to which a respirator type can be used for protection is defined as the product of the APF and the occupa- tional exposure limit for the contaminant. Because of the lack of infor-
90 PREPARING FOR AN INFLUENZA PANDEMIC mation on influenza transmission, the MUC for influenza is unknown. Therefore, it is not possible to specify the conditions under which each type of respirator could be expected to provide adequate protection. This limitation alludes to the need to identify the predominant mode(s) of transmission of influenza and the risk of infectivity that would be ex- pected in certain exposure scenarios. Based on current information, the Centers for Disease Control and Prevention (CDC) has specified that N95 filters be used in most settings, with PAPRs used during procedures that may produce high concentrations of droplets and/or aerosols (CDC, 2006). A mathematical model has been proposed for predicting the probability of infection to Mycobacterium tuberculosis (Nicas, 1995) based on room, patient, worker breathing patterns, and ventilation factors that may be applicable to pandemic influenza. However, this method is complex and may not be applicable to some situations. McCullough and Brosseau (1999) have proposed a qualitative method for selecting respi- rators based on ranking for room ventilation rates, generation rate of aerosols, and level of infectivity. Research is needed that can provide data with which to more accurately select respirators based on the protec- tion provided in different healthcare exposure situations. Improving the Efficacy of Filtration NIOSH classifies respirator filters by the type of aerosol for which they can be used and their filtration efficiency (NIOSH, 2004a). Filters are categorized as N, not resistant to oil aerosols; R, resistant to oil aero- sols; and P, oilproof. The P series of filters can be used when oil particles are present and the filter is to be used for more than one work shift (Bollinger, 2004). Filtration efficiency is classified as 95, 99, or 100 percent. To be ap- proved by NIOSH, filters must pass test protocols that specify flow rates through the filter, the size of the challenge aerosol, and loading on the filter media (NIOSH, 2004a). Filters are tested for NIOSH certification using neutralized particles 0.3 Âµm in size, the particle size found to be most penetrating of filter material. The resulting ratings of 95, 99, or 100 percent filtration efficiency indicate the percentage of 0.3 Âµm particles that do not penetrate the tested filter. Thus, these ratings indicate a maximum risk of 5 percent penetration (at 0.3 Âµm) for filtering materials designated as 95 percent efficient with greater filtering efficiency for larger or smaller size particles.
DESIGNING AND ENGINEERING EFFECTIVE PPE 91 As discussed in Chapter 2, there is still much to be learned about in- fluenza transmission and the size and nature of the airborne particles that are of concern during an influenza pandemic. The size of the influenza virus is approximately 0.08 to 0.120 Âµm (Treanor, 2005), although the droplets containing the virus can vary widely in size. Details regarding filtration efficiency relevant to influenza need to be widely disseminated to healthcare workers. Filtration mechanisms have been studied extensively, and filter effi- ciency is well described by classical filtration theory down to nanoparti- cle sizes (Hinds, 1999). Filters collect aerosols by five mechanisms: impaction, interception, diffusion, electrostatic attraction, and gravita- tional settling (Chen et al., 1993). Factors affecting the efficiency of these mechanisms include the aerodynamic properties of the particles (size, shape, and density) and the velocity of air through the filter. Stud- ies have shown that the efficiency of bacteria and virus filtration also conforms to classical filtration theory and is similar to the efficiency measured by nonviable particles such as polystyrene latex and NaCl (Brosseau et al., 1997; McCullough et al., 1997; Qian et al., 1998). Gravitational settling is not an important removal mechanism for respira- tor filters because the settling velocities of respirable particles are insig- nificant compared to their velocity through the filter. The combined effect of these removal mechanisms results in a most penetrating particle size (MPPS) range in which the filter has minimum filtration efficiency or maximum penetration, usually 0.1 to 0.3 Âµm. Efficiencies of these removal mechanisms are increased by increasing the effective fiber di- ameter, density of the filter, and thickness of the filter. These characteris- tics result in increased resistance to air flow through the filter, which would make it more difficult to breathe. To overcome this problem, modern respirator filters are constructed with electrically charged (elec- tret) fibers that enhance collection efficiency by electrostatic attraction without increasing breathing resistance. A limitation of filters composed of electrically charged fibers is that the charge may dissipate over time or be reduced by the insulating effect of particles collected on the fiber re- sulting in a penetration risk greater than 5 percent (Kanaoka et al., 1984; Chen et al., 1993; Moyer and Bergman, 2000). Also, it has been demon- strated that the MPPS for electret N95 filters is shifted to approximately 30 to 70 nm and that penetration of particles of this size exceeded 5 per- cent whereas the filters met the required NIOSH <5 percent penetration at 0.3 Î¼m (Balazy et al., 2006a,b). These results indicate that NIOSH should explore whether challenge aerosols of 30-100 nm are more pene-
92 PREPARING FOR AN INFLUENZA PANDEMIC trating than those of 300 nm when testing electret filter media. If this is found to be the case, aerosols in this size range should be incorporated into the certification testing protocol for these filters. Determining the Optimum Filter Media and Efficiency Current technologies necessitate a trade-off between enhanced filtra- tion and physiologic burden to the wearer, particularly if the respirator has to be worn for extended periods of time. It has been suggested that 100 percent efficient respirator filter media be used in place of 95 percent efficient filter media to further reduce the risk of exposure to airborne pathogens as a result of filter penetration. However, the use of 100 per- cent efficient filters could create increased breathing resistance (pressure drop) across the filter causing increased flow rate through faceseal leaks, thus resulting in less overall protection. Studies using flow calculations based on theoretical leaks (Campbell, 1984) or measurements using fixed artificial leaks have demonstrated a positive correlation between pressure drop and faceseal leakage (Myers et al., 1991; Krishnan et al., 1994). Nelson and Colton (2000) observed an upward trend of actual faceseal leakage with increasing pressure drop as measured on several subjects. Janssen and Weber (2005) conducted a similar study with changes to address the limitations of the earlier study. They found that there was no increase in faceseal leakage with increasing pressure drop on respirators that fit well enough to pass the OSHA fit factor requirement of 100. These results would indicate that 100 percent efficient respirator filters would not result in increased faceseal leakage and decreased overall pro- tection. Opportunities exist for improving both the comfort and effi- ciency of respirators. Powered Air-Purifying Respirators PAPRs have been recommended for respiratory protection during procedures that may produce high concentrations of droplets and/or aero- sols (CDC, 2006). Based on current APFs, these devices are expected to provide about 2.5 times more protection than elastomeric and filtering facepiece N95 respirators. Current problems associated with using PAPRs in the healthcare setting include high noise levels inside the res- piratory inlet covering, facepiece flow rates, and limited battery life.
DESIGNING AND ENGINEERING EFFECTIVE PPE 93 PAPRs were developed for use in industrial environments, and the NIOSH approval requirements are intended to ensure their performance in those applications (42 CFR 84, Subpart KK). These requirements in- clude maximum noise levels inside the respiratory inlet covering of 80 dBA, flow rates of 115 liters per minute (L/min) into tight-fitting facepieces and 170 L/min into loose-fitting hoods or helmets, and filter penetration tests against silica dust and dioctyl phthalate. The facepiece flow rates are intended to prevent overbreathing by wearers performing moderate to moderate-heavy work with corresponding maximum inspira- tory flow rates of about 85 to 100 L/min. The silica dust test requires fil- ters to be challenged by 50 mg/m3 for a period of 4 hours, resulting in deposition of about 45 mg of silica dust on the filters. To meet these in- dustrial requirements, PAPRs are designed with blowers that have enough power to overcome the flow resistance created by these condi- tions at such high flow rates, which in turn increases noise levels and limits the battery life. The healthcare environment and wear conditions do not require PAPRs that meet such demanding flow rate requirements. It could be reasonably expected that healthcare workers would normally be perform- ing light to moderate work with maximum inspiratory flow rates of about 50 to 85 L/min. Given that the sound level of normal voice communica- tion in a quiet room at a distance of 3 feet is about 60 dBA, it would be extremely difficult for a healthcare worker wearing a PAPR with a back- ground sound level of 80 dBA to be able to hear a patient, let alone heart or lung sounds. Because of the differences between the industrial and healthcare environments, the current NIOSH performance requirements are not appropriate to PAPRs used by healthcare workers. Since PAPR air intakes and the belt to secure the PAPR must be located outside of protective gowns, special attention should be paid to decontamination procedures for these units. NIOSH has drafted a Proposed Industrial Powered, Air-Purifying Respirator (PAPR) Standard (NIOSH, 2006) that addresses some of the problems noted above. Notably, the proposal recognizes loose-fitting facepieces as a respiratory inlet covering. It also specifies base require- ments for all PAPRs and allows application-specific requirements for PAPRs designed for specific uses, including hospitals. The base re- quirements allow blower units to provide variable flow into PAPRs for low, moderate, and high ratings of 100, 170, and 370 L/min, respec- tively. Filter penetration tests are proposed for P95 and P100 filters using
94 PREPARING FOR AN INFLUENZA PANDEMIC the current protocol for nonpowered filters. Loose-fitting facepieces would have to demonstrate a minimum TIL of 250. The proposal allows a maximum sound level of 80 dBA inside the facepiece. It is presumed that a lower sound level could be specified in the application requirements for healthcare PAPRs. Other requirements that should be considered or explored include addressing the need for facepiece designs to accommodate medical procedures (e.g., use of a stethoscope), use of biocides on external surfaces of PAPR components, and designs that will facilitate a low probability of cross-contamination during donning and doffing. Development of this standard should be ex- pedited so it can go into effect at the earliest possible date. GOWNS, EYE PROTECTION, GLOVES, AND OTHER PPE Preventing large-droplet and contact transmission requires the appro- priate use of barrier garments including gowns, protective eyewear, and gloves combined with proper hand hygiene practices (respiratory protec- tion is addressed above). Large-particle droplets, generated by talking, coughing, or sneezing, or by procedures that generate spraying or splash- ing of respiratory secretions, remain airborne over short distances and can be deposited directly onto the respiratory mucosa or conjunctiva (eyes) of susceptible individuals within close range. Indirect contact transmission occurs when large airborne droplets settle rapidly out of the air and deposit the virus onto inanimate surfaces (fomites) such as beds, tables, or clothes, which can then be touched by hands and transferred by autoinoculation to the respiratory mucosa or conjunctiva. The following requirements are stated in the OSHA bloodborne pathogens standard: âPersonal protective equipment will be considered âappropriateâ only if it does not permit blood or other potentially infec- tious materials to pass through to or reach the employeeâs work clothes, street clothes, undergarments, skin, eyes, mouth, or other mucous mem- branes under normal conditions of use and for the duration of time which the protective equipment will be usedâ (OSHA, 2001). Recommenda- tions for healthcare workersâ use of gowns, eyewear, and gloves during an influenza pandemic follow the basic principles of standard precau- tions supplemented by droplet precautions and contact precautions as delineated in the CDCâs guidelines (Siegel et al., 2007; Table 3-2).
DESIGNING AND ENGINEERING EFFECTIVE PPE 95 TABLE 3-2 Use of Gowns, Gloves, and Protective Eyewear in Caring for Patients with Pandemic Influenza Gowns Use during procedures and patient care activities when contact of clothing or exposed skin with blood or body fluids, secre- tions, or excretions is anticipated Protective Use during procedures and patient care activities likely to eyewear or generate splash or spray of blood, body fluids, secretions, or faceshield excretions Gloves Use for contact with blood, body fluids, secretions, excretions, and contaminated items and for touching mucous membranes and nonintact skin; perform hand hygiene after removing gloves and between patient contacts SOURCE: Adapted from DHHS, 2005. Gowns Gowns are worn over clothes to prevent contamination of skin and clothing when physical contact with a patient or contact with potentially contaminated items in the patientâs immediate vicinity is anticipated. However, there are no data documenting the efficacy of gowns in reduc- ing the transmission of influenza. Testing has focused primarily on liquid penetration, particularly of blood, through gown materials with some studies examining penetration of bacteria through the fabric (Smith and Nichols, 1991; Leonas and Jinkins, 1997; Pissiotis et al., 1997; Granzow et al., 1998). The purpose of the gown is to prevent contamination of outer garments and skin that could become fomites and a secondary source of hand contamination. Available gowns vary in their design fea- tures, which should reflect the expected distribution of healthcare work- ersâ exposures to the body fluids of patients. Because body fluid exposures are most often to frontal surfaces and often occur at gaps be- tween protective garments (such as the wrist area at the junction between gowns and gloves), gowns should be designed to provide a continuous barrier in front (i.e., not V-neck or front-opening) and should have long sleeves and snug cuffs that provide an adequate overlap with gloves at the wrist. The wide array of gown materials vary in their liquid barrier per- formance and breathability. In general, as liquid barrier performance in- creases, the breathability of the material (and comfort of the garment) decreases. The ideal material would be an efficient liquid barrier with high breathability. It is acknowledged that materials with both properties
96 PREPARING FOR AN INFLUENZA PANDEMIC tend to be costly. Reusability is another consideration, but more informa- tion is needed on how laundering or other cleaning methods would im- pact the barrier performance and other performance characteristics (Rutala and Weber, 2001). Gowns may be made of material that is highly porous or totally im- pervious to liquid. Since there are no data showing different levels of efficacy in preventing pathogen transmission with different types of gowns, and no requirement for gowns to meet a specific liquid barrier performance test for a given situation, healthcare facilities are in need of guidance for gown selection. Selection is market driven and has led manufacturers to offer a wide variety of materials to meet the capricious market demands. Current cost pressures often create an incentive for healthcare facilities to favor cheaper, more permeable, and potentially less effective materials, particularly because there are few evidence- based standards. The Association for the Advancement of Medical In- strumentation standard AAMI PB70, a voluntary testing standard, de- fines four levels of liquid barrier performance for gown materials. Gown manufacturers label their products in accordance with AAMI PB70. However, there is a need to define the clinical situations under which each level of material is appropriate. Such prescriptive standards could potentially permit manufacturers to consolidate some product lines. The increased efficiency could reduce manufacturersâ production costs and potentially provide a cost benefit for healthcare institutions when pur- chasing gowns to meet the increased demand for barrier garments during an influenza pandemic. Innovations are needed in gown design (with particular attention to the interfaces with other PPE such as gloves), repellant finishes, and fab- ric technology. An in-depth analysis of the level of protection for single- use versus reusable gowns is needed. As outlined earlier in this chapter, evidence-based performance standards are needed that include wearabil- ity, functionality, durability, and other critical factors. Head Covers and Shoe Covers Little is known about the role of head and shoe covers in the preven- tion of influenza transmission. Because the head, hair, and shoes can po- tentially sustain droplet and contact contamination, including secondary contamination from hand contact, efforts should be made to explore the necessity for and effectiveness of head and shoe covers. These types of
DESIGNING AND ENGINEERING EFFECTIVE PPE 97 PPE would likely be worn as part of an ensemble with gowns, and fur- ther work on the elements of the appropriate PPE ensemble for health- care workers is needed with a focus on ease and effectiveness of donning and doffing the equipment without risking further contamination. Addi- tionally, potential interference of head covers with respiratory protection or face shields should be evaluated as part of PPE ensembles. Protective Eyewear Transmission of pathogens by contact with conjunctiva (mucosa of the eyes) has been observed in case studies for other pathogens such as rhinoviruses and bloodborne pathogens (Rosen, 1997; Ippolito et al., 1998; Hosoglu et al., 2003), but no relevant data exist for influenza. Until demonstrated otherwise, conjunctival transmission should be considered a plausible transmission route and appropriate measures should be taken to protect healthcare workersâ eyes from viral contamination during an influenza pandemic. In keeping with standard precautions, â . . . goggles or a faceshield are worn by hospital personnel during procedures and patient-care activi- ties that are likely to generate splashes or sprays of blood, body fluids, secretions, or excretions to provide protection of the mucous membranes of the eyes . . . from contact transmission of pathogens. . . . The wearing of . . . eye protection is mandated by the OSHA bloodborne pathogens final ruleâ (Garner and HICPAC, 1996, p. 63). In addition to protecting from sprays and splashes, eye protection, including face shields, obstructs the inadvertent contact of contaminated hands with the eyes. Eyeglasses do not constitute protective eyewear, and there is no evidence that side shields placed on eyeglasses provide any added protection. The specific circumstances under which protective eyewear should be worn during an influenza pandemic need to be explored and may in- clude the performance of procedures that can produce splashing or spray- ing such as intubation, extubation, suctioning, bronchoscopy, nebulizer treatment, irrigation, and the manipulation of equipment that pumps blood or body fluids under pressure (DHHS, 2005). In an 87-hospital surveillance network of healthcare workersâ blood and body fluid expo- sures, the eyes were the most frequently reported location of exposure (J. Jagger, University of Virginia, personal communication, June 19, 2007). In 94 percent of eye exposures, healthcare workers were not wearing eye protection when neededâindicating a vulnerable site requiring more
98 PREPARING FOR AN INFLUENZA PANDEMIC consistent protection that should be a focus of added attention in the event of pandemic influenza. When face shields and goggles failed to prevent eye exposures, either protective eyewear slipped out of place or fluid ran down from the forehead, indicating the importance of proper fit and the need for a seal above the eyes (Bentley, 1996). Additionally, since protective eyewear shields eyes from inadvertent contact with con- taminated hands it should also be worn when contact precautions are in effect, that is, in proximity to a symptomatic patient or a person likely to be incubating influenza. Eye protection is subject currently to only limited standards or re- quirements relevant to the healthcare workers. FDA does not regulate protective eyewear used as PPE as a medical device. The ANSI standards on eye protection are focused on the thickness and impact resistance of the eye protection and do not address issues related to influenza trans- mission. Industry-wide testing protocols are not available for properties related to the barrier effectiveness and wearability of eye protection. Ex- isting requirements specified by the OSHA bloodborne pathogens stan- dard state: âMasks in combination with eye protection devices, such as goggles or glasses with solid side shields, or chin-length face shields, shall be worn whenever splashes, spray, spatter, or droplets of blood or other potentially infectious materials may be generated and eye, nose, or mouth contamination can be reasonably anticipatedâ (OSHA, 2001). De- spite limited guidance on the subject, the following performance charac- teristics are important for consideration in designing and selecting protective eyewear: barrier effectiveness against fluids (including fluids running down from above, sprayed from below or from side angles), bar- rier effectiveness against hand contact with eyes, adaptability to different size faces, secure fit (resistance to slippage), compatibility with eye- glasses, comfort, clarity or nonobstruction of vision, potential for fog- ging, and compatibility with respirators. Innovations focused on integrating eye protection and respirators will be particularly important to the next generation of PPE products for healthcare workers. Gloves and Hand Hygiene Little is known about the potential for transmission of influenza virus by direct contact with intact or nonintact skin of the hands. Transmission of bloodborne pathogens has been documented by direct contact with nonintact skin (CDC, 1987). Gloves provide a barrier between contami-
DESIGNING AND ENGINEERING EFFECTIVE PPE 99 nated surfaces and the hands. Gloves also minimize patient-to-patient contamination (and contamination of environmental surfaces) if they are removed between patients and proper hand hygiene is performed. Gloved or ungloved hands can be a vehicle of self-inoculation when healthcare workers inadvertently touch the mucosa of the mouth, nose, or eyes with contaminated hands. The changing of gloves after each patient contact and strict adherence to hand hygiene protocols are essential for minimiz- ing patient-to-patient contamination, self-inoculation by healthcare workers, and environmental contamination from the influenza virus. Patient examination and surgeonsâ gloves fall under FDA regulation as Class I medical devices and require a 510k pre-market submission (see Chapter 5). Test procedures and acceptance criteria required by the FDA relate to the barrier properties of gloves and are based on tests for leaks and visual defects as well as sensitivity and biocompatibility (FDA, 2006). Much of the focus in glove design to date has addressed the risk of transmission of bloodborne pathogens. Current guidelines for healthcare workersâ glove use during an influ- enza pandemic are as follows (DHHS, 2005): â¢ A single pair of patient care gloves should be worn for contact with blood and body fluids, including during hand contact with respira- tory secretions (e.g., providing oral care, handling soiled tissues). Gloves made of latex, vinyl, nitrile, or other synthetic materials are appropriate for this purpose; if possible, latex-free gloves should be available for healthcare workers who have latex allergy. â¢ Gloves should fit comfortably on the wearerâs hands. â¢ Remove and dispose of gloves after use on a patient; do not wash gloves for subsequent reuse. â¢ Perform hand hygiene after glove removal. Adherence to proper hand hygiene protocols is complementary to glove use and essential for minimizing the hands as vehicles of viral con- tamination. Hand hygiene practices appropriate for pandemic influenza are the same as those recommended for seasonal influenza. The effec- tiveness of hand hygiene has been well studied (e.g., Ryan et al., 2001; White et al., 2003). The primary challenge with gloving and hand hy- giene is gaining high compliance rates among healthcare workers. In a pandemic influenza situation, strict adherence to hand hygiene protocols would be of great importance. Administrative procedures to achieve high compliance rates should be formulated in advance of a pandemic.
100 PREPARING FOR AN INFLUENZA PANDEMIC Innovations specific to the design and engineering of gloves are needed regarding the interface between the gloves and the gown or other protective equipment, as well as improving barrier protection and wearability. ADDITIONAL AREAS OF RESEARCH In addition to improvements in the design and engineering of PPE that are discussed throughout this chapter, the committee highlights a few areas of research below and then discusses key research questions that need to be addressed expeditiously so that healthcare workers will have effective protection against influenza transmission. Reusable Respirators One of the challenges faced by healthcare facilities in stockpiling supplies in preparation for a pandemic is the large number of disposable respirators that are anticipated to be needed and the associated cost of purchasing this stockpile. Research is needed to determine the necessary decontamination procedures to inactivate influenza viruses on respirators (IOM, 2006). Based on these findings, exploration should be made of the cost-benefit of reusable respirators that have a long-term shelf life and are built for extended wear during a pandemic. As outlined above, a number of other design elements that are critical to enhancing the weara- bility and use of the respirator would have to be factored in to either adapt current respirators or design and manufacture new approaches to respiratory protection. Design and Development of Intelligent PPE The role of PPE is to protect the healthcare worker. However, in use, the efficacy of the PPE may decrease over time. Knowing when the PPE is no longer efficacious is important for the healthcare worker for two reasons: (1) from a personal comfort or psychological standpoint, know- ing that s/he is safe and thus can focus on and be effective in carrying out the task at hand (e.g., taking care of patients), especially in the event of a pandemic, and (2) from a pragmatic perspective, knowing when to
DESIGNING AND ENGINEERING EFFECTIVE PPE 101 change the PPE to avoid being infected or becoming infectiveâboth are important to ensure a safe working environment. Therefore, there is a critical need for incorporating âend-of-service-lifeâ or âremaining-level- of-protectionâ capability in PPE. Research should be directed to develop and integrate such sensors to create intelligent PPE (e.g., respirators, gowns) and test their functionality in the field. In a similar manner, when PPE has been compromised, intelligent sensors integrated into the PPE could alert the wearer of the breach. For instance, a litmus paper-like sensor could be placed on the outer edge of the respirator that would change color when there is a leak in the face- seal. Such an indicatorâanalogous to an alarmâwould alert the wearer of the leakage and trigger appropriate preventive measures. Therefore, research should be directed to develop simple, yet functional, sensors to detect and alarm when such leakage occurs in respirators (or other PPE such as gowns). Application of Shape Memory Polymers to Enhance Comfort and Fit of PPE Since the healthcare workerâs temperature will change during the workday, research should be directed to investigate the use of shape memory polymers to develop respirators that conform to the wearerâs facial profile and maintain a tight faceseal with changing temperature. Shape memory polymers can ârememberâ their shape and return to it when subjected to heat. For example, a fender that has been dented in an accident could return to its original shape with the application of heat (Brennan, 2001). Shape memory polymers are composed of two compo- nent phases, one with a higher melting point and another with a lower melting point or glass transition temperature (Frund, 2007). They can be used as a membrane laminate to regulate garment cooling. When the body temperature rises above a preset level (controlled by molecular structure and molecular weight), micropores are formed in the laminate permitting heat and water vapor to escape. The permeability and dissipa- tion of heat through the laminate increase as the body temperature rises, thus maintaining the wearerâs comfort. When the body temperature falls below a threshold level, the micropores âclose,â thus retaining the heat of the wearer and keeping the wearer comfortable. Therefore, research should be directed to investigate the role and use of shape memory polymers to create more breathable and comfortable PPE.
102 PREPARING FOR AN INFLUENZA PANDEMIC Currently, fit testing is a critical requirement for ensuring the efficacy of respirators. However, it may not always be complied with for various reasons, including time and cost. Moreover, current methods preclude the fit testing of individuals with facial hair, and respirators are not designed specifically for young children. Therefore, the use of shape memory polymers in the design of respirators should be investigated to enhance ease of fit and comfort and potentially to minimize fit testing. A short- term goal should be to develop respirators that would be easy to fit, while a longer-term goal should be to find a way to obviate the need for fit test- ing of respirators while being efficacious for all individuals. Chemical Treatments on PPE with Biocidal Properties There are times when the fit of a respirator is compromised and pathogens can gain entry to the face (Li et al., 2006a). Moreover, the pro- tective effect of N95 respirators and medical masks is maintained only when the surface layer is hydrophobic and dry. Therefore, when the PPE is wetted, protection is reduced significantly. Also, if the surface is con- taminated with infectious agents, pathogens may penetrate the protective layers along with the droplets. The use of biocidal compounds as coatings for PPE is being explored (Sun and Xu, 1998; Li et al., 2006a). Li and colleagues (2006a) have de- veloped an antimicrobial nanoparticle coating from a mixture of silver nitrate and titanium dioxide and demonstrated its effectiveness against common hospital pathogens. In addition, Baker and colleagues (2005) have demonstrated that complete cytotoxicity to bacteria cells was possi- ble at low concentrations of silver nanoparticles. These promising studies highlight the value of such finishing treatments in enhancing the protec- tion afforded by PPE to healthcare workers. Therefore, research should be directed to investigate the use of chemical treatments (e.g., using nanoparticles) to impart biocidal properties to PPE to enhance their pro- tection capability and possibly extend their useful life. User safety is the primary consideration; testing standards will be needed to ensure that biocidal materials do not pose hazards to PPE wearers.
DESIGNING AND ENGINEERING EFFECTIVE PPE 103 OPPORTUNITIES FOR ACTION As discussed throughout this chapter, there are a number of areas in which research is needed to improve the wearability, functionality, and other critical aspects of healthcare PPE. The committee has identified several key actions that if addressed expeditiously (in the next 6 to 12 months) could have a significant impact on improving the nationâs readi- ness for pandemic influenza; longer-term opportunities and research questions abound and need to be explored for improving healthcare PPE products so that they can be used more effectively, with greater ease and comfort, and for longer periods of time. Immediate Opportunities There is an immediate need to examine the design of PPE for health- care workers, to improve coordination and expedite approval, and to un- derstand the efficacy of various decontamination techniques (e.g., bleach, microwave radiation, ultraviolet light) that could be employed on PPE in a healthcare setting. Questions of interest include the following: â¢ For what period of time does PPE remain contaminated with in- fectious influenza viruses, and what improvements can be made in doff- ing and decontamination procedures given that information? What are the appropriate PPE decontamination strategies that would not compro- mise the integrity of the PPE while being easy and cost-effective to im- plement in a healthcare setting? â¢ What are the differences in protection of N95 versus N100 or other respirators if exposed to human and avian influenza aerosols? â¢ Current PAPRs are designed to provide extremely high flow rates to protect the worker in an industrial setting. While appropriate to protect from significant dust exposures, they present serious design im- pediments for the healthcare worker. What are the flow rates and maxi- mum noise levels that would be required for NIOSH to certify a PAPR that would provide adequate protection for healthcare workers? What is the risk to patients from healthcare workers wearing PAPRs (from unfil- tered exhaled air), and what design modifications would be needed to eliminate such risk as well as facilitate interactions with patients? â¢ Could a nondisposable respirator be designed that could be eas- ily decontaminated and cost-effective?
104 PREPARING FOR AN INFLUENZA PANDEMIC â¢ What immediate systemic or strategic measures can be taken to facilitate closer collaboration between healthcare workers (end users), PPE manufacturers, and certification or regulatory agencies on the design and development of PPE for healthcare? Long-Term Key Research Needs â¢ What protective roles do gloves, gowns, and face shields or other eye protection play in preventing influenza transmission? What protec- tion would medical masks provide to the wearer during an influenza pandemic? â¢ Do specific procedures (e.g., nebulization, endotracheal intuba- tion, bronchoscopy, cleaning of patientsâ rooms) place healthcare work- ers at higher levels of risk of influenza infection? To what extent do various types of PPE offer protection during these procedures and processes? â¢ What technologies can improve fit to circumvent the need for fit testing? â¢ What innovative designs can improve wearability issues regard- ing PPE? â¢ Can the protection levels of the PPE worn by healthcare workers (e.g., N95 respirators) be continuously monitored during use to provide an alert to change the PPE when it is no longer effective? â¢ How does the penetration risk of N95 respirators made of differ- ent materials and designs change with high inhalation rates? â¢ How does the level of protection afforded by N95 change with and without fit testing? â¢ What is the impact of masking influenza patients on transmission risk? If effective, how long before the medical mask needs to be changed? â¢ What are the best practices for PPE removal to minimize risk of self-inoculation? â¢ What are the risks of self-inoculation when changing PPE (i.e., is the true acquisition risk the same when wearing a medical mask and changing to an N95 for high-risk procedures versus wearing an N95 throughout the shift)?
DESIGNING AND ENGINEERING EFFECTIVE PPE 105 SUMMARY AND RECOMMENDATIONS Healthcare workers need PPE that provides protection against influ- enza transmission and that can be worn while working without adding undue physiological burdens. Designing and engineering effective PPE that will meet the needs of healthcare workers during an influenza pan- demic will require careful consideration of three key factors: protection, cost, and comfort, while also achieving certification and approval criteria established by FDA, NIOSH, and other relevant agencies and organiza- tions. Critical to the design and development of PPE are a more thorough understanding of the threats posed by the influenza virus (see Chapter 2) and greater engagement of healthcare workers in the design and testing processes to provide information on the risks and the workplace envi- ronment. Innovative designs and materials are needed for the next gen- eration of PPE for healthcare workers. For respirators, the filter and the faceseal are the critical issues; other types of PPE provide barrier protec- tion and require innovations particularly regarding the interface between PPE (e.g., between eye protection and respirators). The development of design and performance standards is envisioned as an iterative process that will lead to more effective and wearable PPE products based on evolving technologies and feedback from all stake- holders including data from researchers on the transmission of influenza and input from healthcare workers on performance requirements. Based on an in-depth analysis of the design and engineering of effective PPE for healthcare workers, the committee has developed the following set of recommendations: Recommendation 2 Define Evidence-Based Performance Re- quirements (Prescriptive Standards) for PPE NIOSH, through the National Personal Protective Technology Laboratory (NPPTL), in collaboration with extramural re- searchers, manufacturers, and regulatory agencies, should de- fine a set of evidence-based performance requirements or prescriptive standards for PPE to facilitate their design and development that optimally balances the cost, comfort, and degree of protection of PPE and enhances compliance with their use in the field.
106 PREPARING FOR AN INFLUENZA PANDEMIC Recommendation 3 Adopt a Systems Approach to the Design and Development of PPE NIOSH should promote a systems approach to the design, de- velopment, testing, and certification of PPE using evidence- based performance requirements or prescriptive standards and fostering closer collaboration between users, manufac- turers, and research and regulatory agencies. Recommendation 4 Increase Research on the Design and En- gineering of the Next Generation of PPE NIOSH, the Department of Homeland Security, the Depart- ment of Defense, manufacturers, and other relevant organiza- tions and agencies should fund research directed at the design and development of the next generation of respirators, gowns, gloves, and eye protection for healthcare workers that would enhance their safety and comfort by â¢ utilizing innovations in materials such as shape mem- ory polymers (e.g., to obviate fit testing and enhance fit of respirators and comfort of gowns) and finishing treatments (e.g., safe antimicrobial or biocidal finishes); â¢ developing more effective and consistent faceseals for respirators, including examination of the effect of wear and repeated donning and doffing on the qual- ity of the faceseal of filtering facepiece respirators, and research on the effect of respirator filter effi- ciency on faceseal leakage and degree of protection; â¢ providing a seamless interface between PPE (e.g., eye protection and respirators); â¢ designing respirator facepieces to integrate medical devices such as a stethoscope and to improve commu- nication between the user and others; â¢ establishing a new set of performance requirements for PAPRs and for reusable filtering facepiece respi- rators that meet the needs of healthcare workers; and â¢ incorporating sensors into PPE to detect breaches and notify users of end of service life and other pro- tection information.
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