Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-30 (of 74 Records) |
Query Trace: Zhuang Z[original query] |
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Evaluating source control efficacy against exhaled submicron particles: Total outward leakage of surgical masks and half facepiece respirators across a spectrum of particle sizes
Yang W , Myers WR , Bergman M , Fisher E , Ryan KJ , Vollmer B , Portnoff L , Zhuang Z . Aerosol Sci Technol 2024 The size of airborne particles emitted from infected individuals is crucial in the transmission of respiratory viruses. The use of source control devices is essential for interrupting the transmission of exhaled submicron particles, particularly in healthcare settings with high infection risk. This study evaluated the efficacy of five types of source control devices, commonly used in healthcare settings, in mitigating the transmission of exhaled submicron particles (20–210 nm). Total outward leakage (TOL) of these devices was analyzed across different particle sizes, and the TOL mean diameter (TOLMD) was calculated to characterize particle size distribution. The devices tested included N95 filtering facepiece respirators (N95 FFRs), N95 FFRs with an exhalation valve (N95 FFRV), surgical masks (SMs), elastomeric half-mask respirators (EHMRs), and EHMRs with a SM covering the exhalation valve (EHMRSM). The study also examined the effects of faceseal and flowrate on TOL and particle size characteristics. Results indicated that TOL varied with particle size, increasing from 40 to 90 nm before stabilizing. Aerosols larger than 90 nm had significantly higher TOL compared to smaller aerosols. Higher flow rates increased TOL for EHMR and EHMRSM across all particle sizes. Improved faceseal on N95 FFRs and SMs significantly reduced TOL and decreased TOLMD. The study underscored that using well-fitting devices without exhalation valves is crucial for preventing the transmission of exhaled aerosols potentially carrying viruses, in particular for larger particle sizes. This is especially crucial in the absence of proper indoor ventilation and other control measures. © This work was authored as part of the Contributor’s official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law. |
Impact of self-contained breathing apparatus (SCBA) weights on firefighter's kinematics during simulated firefighter tasks
Xu S , Jones R , Ratnakumar N , Akbas K , Powell J , Zhuang Z , Zhou X . Appl Hum Factors Ergon Conf 2024 131 142-149 Firefighters face a multitude of hazards in their line of duty, with overexertion being one of the foremost causes of injuries or fatalities. This high risk is often exacerbated by the burden of carrying a heavy self-contained breathing apparatus (SCBA). This study aims to explore the impact of SCBA weight on firefighters' musculoskeletal joint movements. Six firefighters participated in this study, performing four simulated firefighting tasks under three different SCBA weight conditions. A hybrid inverse kinematics approach was employed to analyze the kinematic data from two participants. The results revealed a notable decrease in lumbar range of motion (ROM) as the weight increased, particularly noticeable during hose advancement and stair climbing tasks. Conversely, an increase in hip ROM during stair climbing was observed, suggesting a compensatory response to reduced spinal flexibility. These findings underscore the critical need to understand the implications of turnout gear and SCBA weight to enhance firefighter performance and reduce the risk of injury. |
Total outward leakage of face-worn products used by the general public for source control
Yang W , Myers W , Bergman M , Fisher E , Ryan KJ , Vollmer B , Portnoff L , Zhuang Z . Am J Infect Control 2024 BACKGROUND: During COVID-19 pandemic, the general public used any face-worn products they could get to overcome the shortage of N95 respirators and surgical masks. These products, often not meeting any standards, raised concerns about their effectiveness in reducing the spread of respiratory viruses. METHODS: This study quantified total outward leakage (TOL) of units from nine face-worn product categories used by members of the general public. A benchtop system was devised to test two units from each category on two different-sized headforms with silicone elastomer skin. Each unit was donned five times per headform. RESULTS: Both face-worn product category and headform size significantly affected TOL (P-Value <0.05). The TOL of tested face-worn products varied from 10% to 58% depending on both model and headform size. Face-worn products donned on the medium headform had a higher mean TOL compared to those donned on the larger headform. CONCLUSIONS: Overall, single-layer cloth masks are the least effective measure for source control due to their highest TOL among the tested face-worn products. Three-layer disposable face masks may be a favorable option for source control among the public. A standard should be developed for face-worn product design and manufacturing to accommodate different facial sizes. |
Next-generation custom-fit reusable respiratory protective device with continuous fit monitoring - Part II: Continuous fit monitoring
Park S , Tian Y , Bergman M , Pollard J , Zhuang Z , Jayaraman S . J Int Soc Respir Prot 2024 41 (1) 38-56 Filtering facepiece respirators (FFRs) are manufactured in discrete sizes, with some models being limited in accommodating the fit of some sex and race combinations. This study presents the development of a custom-fit respiratory protective device (RPD) which conforms to a user's facial features and flexes and moves with facial movements during use. Our design also integrates a pressure-sensing network, which continuously monitors fit and will alert the user when the fit is compromised. In this Part II of the three-part series, we design and incorporate a continuous fit monitoring system in the RPD designed in Part I to enhance its role in protecting users from inhalation hazards in an effective manner during its use. The fit monitoring system comprises a fabric-based sensor network integrated into the RPD and an Android-based App designed to alert the user when the pressure at the faceseal falls below a given threshold established during the initial configuration of the RPD for the user. We also develop algorithms for the incorporation of the sensor slots and data buses into the custom-fit RPD using the Taxonomy of Landmarks defined in Part I. We enhance the structure developed in Part I to secure the sensor network during the use of the RPD. We develop algorithms for customizing a fastening hub to suit the head profiles of individuals to enable them to don the RPD quickly, easily, effectively, and in a repeatable manner. We demonstrate the successful application of the total design methodology by creating digital prototypes for three individuals with different facial profiles and make further advances to our goal of ensuring equitable respiratory protection for all including children, for whom RPDs are currently limited. |
Evaluation of self-contained breathing apparatus (SCBA) weight on firefighter stamina, comfort, and postural stability
Kesler RM , Powell J , Nguyen D , Massey KA , Joshi S , Xu S , Zhuang Z , Horn GP , Burd NA , Masoud F . Ergonomics 2024 1-14 Firefighters wear personal protective equipment to protect them from the thermal and chemical environment in which they operate. The self-contained breathing apparatus (SCBA) provides isolation of the airway from the hazardous fireground. National standards limit SCBA weight, however, integration of additional features could result in an SCBA exceeding the current limit. The purpose of this study was to examine the effects of increased SCBA weight on firefighters' physiological responses, work output, dynamic stability, and comfort. Completion of simulated firefighting activities induced a strong physiological response. Peak oxygen consumption was higher with the lightest SCBA than the heaviest SCBA. Few other physiological differences were noted as SCBA weight increased. Importantly, increased SCBA weight resulted in significantly more negative perceptions by the firefighters and a trend towards significance for the duration of work time prior to reaching volitional fatigue. These results should be considered when assessing changes to existing SCBA weight limits. | Increased SCBA weight above existing national standards resulted in negative perceptions by the firefighters, but not significant physiological changes after two simulated bouts of firefighting activity. SCBA weight had a nearly significant impact on the time firefighters worked before reaching volitional fatigue, with heavier SCBA trending towards decreased working time. | eng |
Elastomeric half-mask respirator disinfection practices among healthcare personnel
Hines SE , Thurman P , Zhuang E , Chen H , McDiarmid M , Chalikonda S , Angelilli S , Waltenbaugh H , Napoli M , Haas E , McClain C , Sietsema M , Fernando R . Am J Ind Med 2023 66 (12) 1056-1068 BACKGROUND: Disposable N95 respirator shortages during the COVID-19 and 2009 H1N1 influenza pandemics highlighted the need for reusable alternatives, such as elastomeric half-mask respirators (EHMRs). Two US medical organizations deployed reusable EHMRs during the COVID-19 response. In addition to wipe-based disinfection following patient care episodes expected per local policies at both organizations, postshift centralized cleaning and disinfection (C&D) was expected at one site (A), permitting shared-pool EHMR use, and optional at the other (Site B), where EHMRs were issued to individuals. Using a survey, we evaluated disinfection practices reported by EHMR users and predictors of disinfection behaviors and perceptions. METHODS: Surveys assessed EHMR disinfection practices, occupational characteristics, EHMR use frequency, training, and individual-issue versus shared-pool EHMR use. RESULTS: Of 1080 EHMR users completing the survey, 76% reported that they disinfect the EHMR after each patient encounter, which was the expected practice at both sites. Increasing EHMR use, recall of disinfection training, and work in intensive care or emergency settings significantly influenced higher reporting of this practice. 36% of respondents reported using centralized C&D, although reporting was higher at the site (A) where this was expected (53%). Confidence in cleanliness of the EHMR following centralized C&D was not influenced by individual versus shared-pool EHMR issue. CONCLUSIONS: Most EHMR users reported adherence with expected post-care individual-based disinfection of EHMRs but did not necessarily use standardized, centralized C&D. Future efforts to limit reliance on behavior related to respirator disinfection may improve EHMR implementation in healthcare to avert dependence on single-use, disposable N95 respirators. |
Total outward leakage of half-mask respirators and surgical masks used for source control
Myers WR , Yang W , Ryan KJ , Bergman M , Fisher E , Soo JC , Zhuang Z . J Occup Environ Hyg 2023 1-15 Both respirators and surgical masks (SM) are used as source control devices. During the COVID-19 pandemic, there was much interest in understanding the extent of particle total outward leakage (TOL) from these devices. The objective of this study was to quantify the TOL for five categories of devices: SMs, National Institute for Occupational Safety and Health (NIOSH®) Approved N95(®) filtering facepiece respirators (FFRs) without exhalation valves, NIOSH Approved N95 FFRs with exhalation valves (N95 FFRV), NIOSH Approved elastomeric half-mask respirators (EHMRs) with exhalation valves, and NIOSH Approved EHMRs with an SM covering the exhalation valve (EHMRSM). A benchtop test system was designed to test two models of each device category. Each device was mounted on a headform at three faceseal levels (0% faceseal, 50% faceseal, and 100% faceseal). At each faceseal level, the TOL was assessed at three flowrates of minute ventilations of 17, 28, and 39 L/min. The experimental design was a split-split-plot configuration. Device type, faceseal level, flowrate, and the interaction of device type and faceseal level were found to have a significant effect ( P - Value <0.05) on the TOL.This study found that the N95 FFRs without exhalation valves had the lowest mean TOL. The SMs had about three times higher TOL than the N95 FFRs without exhalation valves. The TOL of the N95 FFRV was comparable to that of the SM at 0% and 50% faceseal on average over all conditions, but the N95 FFRV had a significantly higher TOL than the SM at a 100% faceseal. The EHMRs had the highest TOL because of the exhalation valve. Using an SM to cover the exhalation valve did not improve the EHMRs' efficiency in mitigating the TOL. Caution should be exercised when using N95 FFRVs as a source control measure against respiratory activities with heavy work rates, such as performing CPR. Results of this study showed that reduced faceseal leakage for N95 FFRs and SMs improves source control. |
Fit evaluation of NIOSH Approved N95 filtering facepiece respirators with various skin protectants: a pilot study
Bergman MS , Grinshpun SA , Yermakov MV , Zhuang Z , Vollmer BE , Yoon KN . J Occup Environ Hyg 2023 20 (9) 1-10 Widespread disease outbreaks can result in prolonged wear times of National Institute for Occupational Safety and Health Approved N95 filtering facepiece respirators by healthcare personnel. Prolonged wear times of these devices can cause the development of various adverse facial skin conditions. Healthcare personnel have been reported to apply "skin protectants" to the face to reduce pressure and friction of respirators. Because tight-fitting respirators rely on a good face seal to protect the wearer, it is important to understand if fit is affected when skin protectants are used. This laboratory pilot study included 10 volunteers who performed quantitative fit tests to evaluate respirator fit while wearing skin protectants. Three N95 filtering facepiece respirator models and three skin protectants were evaluated. Three replicate fit tests were performed for each combination of subject, skin protectant (including a control condition of no protectant), and respirator model. Fit Factor (FF) was affected differently by the combination of protectant type and respirator model. The main effects of protectant type and respirator model were both significant (p <0.001); additionally, their interaction was significant (p = 0.02), indicating FF is affected by the combined effects of protectant type and respirator model. Compared to the control condition, using a bandage-type or surgical tape skin protectant decreased the odds of passing the fit test. Using a barrier cream skin protectant also decreased the odds of passing the fit test across all models compared to the control condition; however, the probability of passing a fit test was not statistically significantly different from the control condition (p = 0.174). These results imply that all three skin protectants reduced mean fit factors for all N95 filtering facepiece respirator models tested. The bandage-type and surgical tape skin protectants both reduced fit factors and passing rates to a greater degree than the barrier cream. Respirator users should follow respirator manufacturers' guidance on the use of skin protectants. If a skin protectant is to be worn with a tight-fitting respirator, the fit of the respirator should be evaluated with the skin protectant applied before use in the workplace. |
Evaluation of the effects of wiping decontamination for filter cartridges of elastomeric half-mask respirators (EHMRs)
Vo E , Horvatin M , Zhuang Z , McClain C , Streeter R , Brannen J , Suhon NL . Am J Infect Control 2023 BACKGROUND: A major concern among healthcare experts is a shortage of N95 filtering facepiece respirators (FFRs) during a pandemic. If the supply of N95 FFRs becomes limited, reusable elastomeric half-mask respirators (EHMRs) may be used to protect healthcare workers. The focus of this study was to evaluate the effects on filter performance of wiping decontamination for EHMR P100 filter cartridges. METHODS: The filter cartridge exterior of EHMR Honeywell, Moldex, and MSA models was wiped using quaternary ammonium and sodium hypochlorite wipes. These filter cartridge properties were assessed including observational analysis and filter performance tests. These wiping and assessing procedures were repeated after each set of wiping cycles (50, 100, 150, 200, and 400 cycles) to determine the effects of wiping decontamination. RESULTS: For sodium hypochlorite wipes, Honeywell, Moldex, and MSA models passed the NIOSH liquid particulate penetration criteria for all wiping cycles from 50 to 400 (penetrations < 0.014%). For quaternary ammonium wipes, filter penetrations of Moldex failed (penetrations >0.03%) after 150 cycles, while the filter penetrations of Honeywell and MSA passed for all wiping cycles (penetrations ≤ 0.013%). CONCLUSIONS: Wiping decontamination methods using sodium hypochlorite and quaternary ammonium wipes could be considered as promising decontamination candidates for Honeywell, Moldex, and MSA reuse, except for the wiping number selection for Moldex (< 150 cycles) when using the quaternary ammonium wipe. |
Paraquat Toxicogenetics: Strain-Related Reduction of Tyrosine Hydroxylase Staining in Substantia Nigra in Mice.
Torres-Rojas C , Zhao W , Zhuang D , O'Callaghan JP , Lu L , Mulligan MK , Williams RW , Jones BC . Front Toxicol 2021 3 722518 ![]() Paraquat (PQ) is a putative risk factor for the development of sporadic Parkinson's disease. To model a possible genetic basis for individual differences in susceptibility to exposure to PQ, we recently examined the effects of paraquat on tyrosine hydroxylase (TH)-containing neurons in the substantia nigra pars compacta (SNc) of six members of the BXD family of mice (n = 2-6 per strain). We injected males with 5 mg/kg paraquat weekly three times. The density of TH+ neurons counted by immunocytochemistry at 200x in eight or more sections through the SNc is reduced in five of the six strains relative to control (N = 4 ± 2 mice per strain). TH+ loss ranged from 0 to 20% with an SEM of 1%. The heritability was estimated using standard ANOVA and jackknife resampling and is 0.37 ± 0.05 in untreated animals and 0.47 ± 0.04 in treated animals. These results demonstrate genetic modulation and GxE variation in susceptibility to PQ exposure and the loss of TH staining in the substantia nigra. |
A manikin-based assessment of loose-fitting powered air-purifying respirator performance at variable flow rates and work rates
Strickland KT , Bergman MS , Xu S , Zhuang Z . J Occup Environ Hyg 2023 20 (7) 1-14 Loose-fitting powered air-purifying respirators (PAPRs) are used in healthcare settings, although barriers to routine, everyday usage remain, including usability concerns and potential interference with work activities. Loose-fitting PAPRs are approved by the National Institute for Occupational Safety and Health (NIOSH) and must meet minimum performance requirements, including a minimum airflow requirement of 170 L/min. One course of action to address usability concerns is to allow for the use of PAPRs designed with reduced airflow rates. The primary objective of this study was to assess the effect of PAPR flow rate and user work rate on PAPR performance, using a manikin-based assessment method. PAPR performance was quantified using "Manikin Fit Factor" (mFF), a ratio of the challenge aerosol concentration to the in-facepiece concentration. Flow rates from 50-215 L/min and low, moderate, and high work rates were tested. Two models of NIOSH Approved® loose-fitting facepiece PAPRs were tested, both having an Occupational Safety and Health Administration Assigned Protection Factor (APF), or expected level of protection, of 25. A two-way analysis of variance with an effect size model was run for each PAPR model to analyze the effects of work rate and flow rate on PAPR performance. Flow rate and work rate were found to be significant variables impacting PAPR performance. At low and moderate work rates and flow rates below the NIOSH minimum of 170 L/min, mFF was greater than or equal to 250, which is ten times the OSHA APF of 25 for loose-fitting facepiece PAPRs. At high work rates and flow rates below 170 L/min, mFF was not greater than or equal to 250. These results suggest that some loose-fitting facepiece PAPRs designed with a flow rate lower than the current NIOSH requirement of 170 L/min may provide respirator users with expected protection at low and moderate work rates. However, when used at high work rates, some loose-fitting facepiece PAPRs designed with lower flow rates may not provide the expected level of protection. |
Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19-Associated Emergency Department or Urgent Care Encounters and Hospitalizations Among Immunocompetent Adults - VISION Network, Nine States, September-November 2022.
Tenforde MW , Weber ZA , Natarajan K , Klein NP , Kharbanda AB , Stenehjem E , Embi PJ , Reese SE , Naleway AL , Grannis SJ , DeSilva MB , Ong TC , Gaglani M , Han J , Dickerson M , Fireman B , Dascomb K , Irving SA , Vazquez-Benitez G , Rao S , Konatham D , Patel P , Schrader KE , Lewis N , Grisel N , McEvoy C , Murthy K , Griggs EP , Rowley EAK , Zerbo O , Arndorfer J , Dunne MM , Goddard K , Ray C , Zhuang Y , Timbol J , Najdowski M , Yang DH , Hansen J , Ball SW , Link-Gelles R . MMWR Morb Mortal Wkly Rep 2022 71 (5152) 1616-1624 During June-October 2022, the SARS-CoV-2 Omicron BA.5 sublineage accounted for most of the sequenced viral genomes in the United States, with further Omicron sublineage diversification through November 2022.* Bivalent mRNA vaccines contain an ancestral SARS-CoV-2 strain component plus an updated component of the Omicron BA.4/BA.5 sublineages. On September 1, 2022, a single bivalent booster dose was recommended for adults who had completed a primary vaccination series (with or without subsequent booster doses), with the last dose administered ≥2 months earlier (1). During September 13-November 18, the VISION Network evaluated vaccine effectiveness (VE) of a bivalent mRNA booster dose (after 2, 3, or 4 monovalent doses) compared with 1) no previous vaccination and 2) previous receipt of 2, 3, or 4 monovalent-only mRNA vaccine doses, among immunocompetent adults aged ≥18 years with an emergency department/urgent care (ED/UC) encounter or hospitalization for a COVID-19-like illness.(†) VE of a bivalent booster dose (after 2, 3, or 4 monovalent doses) against COVID-19-associated ED/UC encounters was 56% compared with no vaccination, 31% compared with monovalent vaccination only with last dose 2-4 months earlier, and 50% compared with monovalent vaccination only with last dose ≥11 months earlier. VE of a bivalent booster dose (after 2, 3, or 4 monovalent doses) against COVID-19-associated hospitalizations was 57% compared with no vaccination, 38% compared with monovalent vaccination only with last dose 5-7 months earlier, and 45% compared with monovalent vaccination only with last dose ≥11 months earlier. Bivalent vaccines administered after 2, 3, or 4 monovalent doses were effective in preventing medically attended COVID-19 compared with no vaccination and provided additional protection compared with past monovalent vaccination only, with relative protection increasing with time since receipt of the last monovalent dose. All eligible persons should stay up to date with recommended COVID-19 vaccinations, including receiving a bivalent booster dose. Persons should also consider taking additional precautions to avoid respiratory illness this winter season, such as masking in public indoor spaces, especially in areas where COVID-19 community levels are high. |
Impact of tenofovir disoproxil fumarate use during pregnancy on maternal bone mineral density
Wang L , Kourtis AP , Wiener J , Chen L , Liu W , Fan B , Shepherd J , Bulterys M . Pediatr Infect Dis J 2022 41 (12) 976-978 Chronic hepatitis B virus (HBV) infection and HIV infection are diseases of great public health importance. Tenofovir disoproxil fumarate (TDF), a nucleotide analog reverse transcriptase inhibitor, is effective for the treatment of both HIV and HBV.1,2 However, information on the bone safety of TDF during pregnancy, a time with increased demands on bone metabolism, has not been systematically assessed. | We conducted a phase II randomized controlled trial (RCT) in Guangxi Zhuang Autonomous Region of the People’s Republic of China, to evaluate the bone mineral density (BMD) effects of TDF on women and their infants. Effects of TDF on bone health of infants have been reported elsewhere3; this report presents our findings on the effects of TDF on maternal BMD. |
Laboratory assessment of bacterial contamination of a sterile environment when using respirators not traditionally used in a sterile field environment
Myers W , Ajewole S , Xu S , Yorio P , Hornbeck A , Zhuang Z . Infect Control Hosp Epidemiol 2022 43 (12) 1-6 OBJECTIVE: During infectious disease outbreaks or pandemics, an increased demand for surgical N95s that create shortages and necessitate the use of alternative National Institute for Occupational Safety and Health (NIOSH)-approved respirators that do not meet the Food and Drug Administration (FDA) additional requirements. The objective of this research was to quantify the level of bacterial contamination resulting from wearing NIOSH-approved respirators lacking the additional protections afforded by surgical N95s. METHODS: Participants performed simulated healthcare tasks while wearing 5 different respirators approved by the NIOSH. Sterile field contamination resulting from use of a surgical mask cleared by the FDA served as a baseline for comparison with the NIOSH-approved respirators. RESULTS: The bacterial contamination produced by participants wearing the N95 filtering facepiece respirators (FFRs) without an exhalation valve, the powered air-purifying respirators (PAPRs) with an assigned protection factor of 25 or 1,000 was not significantly different compared to the contamination resulting from wearing the surgical mask. The bacterial contamination resulting from wearing the N95 FFR with an exhalation valve and elastomeric half-mask respirator (EHMR) with an exhalation valve was found to be statistically significantly higher than the bacterial contamination resulting from wearing the surgical mask. CONCLUSIONS: Overall, NIOSH-approved respirators without exhalation valves maintain a sterile field as well as a surgical mask. These findings inform respiratory guidance on the selection of respirators where sterile fields are needed during shortages of surgical N95 FFRs. |
Characteristics associated with healthcare worker knowledge and confidence in elastomeric half-mask respirator use
Thurman P , Zhuang E , Chen HH , McClain C , Sietsema M , Fernando R , McDiarmid MA , Hines SE . J Occup Environ Med 2022 64 (9) 802-807 OBJECTIVE: This study evaluated healthcare workers' (HCW) knowledge and confidence in using elastomeric half-mask respirator (EHMR) attributes known to influence usage. METHODS: HCW were surveyed regarding their EHMR donning and doffing experience. Respondents were categorized into competency categories based on their scores. Category differences were analyzed using chi square and multiple logistic regression. RESULTS: 72% showed high levels of EHMR donning and doffing knowledge and confidence (mastery); however, 21% had greater confidence than knowledge (misinformed). Respiratory therapists had greater odds of mastery than other HCW (p < .05), while those working in medical/surgical and pediatric units had greater odds of doubt than other HCW (p < .01). CONCLUSION: While most HCW show high knowledge and confidence with EHMR use strategies to confirm respirator use competency may ensure greater HCW protection. |
Effectiveness of two-dose vaccination with mRNA COVID-19 vaccines against COVID-19-associated hospitalizations among immunocompromised adults-Nine States, January-September 2021.
Embi PJ , Levy ME , Naleway AL , Patel P , Gaglani M , Natarajan K , Dascomb K , Ong TC , Klein NP , Liao IC , Grannis SJ , Han J , Stenehjem E , Dunne MM , Lewis N , Irving SA , Rao S , McEvoy C , Bozio CH , Murthy K , Dixon BE , Grisel N , Yang DH , Goddard K , Kharbanda AB , Reynolds S , Raiyani C , Fadel WF , Arndorfer J , Rowley EA , Fireman B , Ferdinands J , Valvi NR , Ball SW , Zerbo O , Griggs EP , Mitchell PK , Porter RM , Kiduko SA , Blanton L , Zhuang Y , Steffens A , Reese SE , Olson N , Williams J , Dickerson M , McMorrow M , Schrag SJ , Verani JR , Fry AM , Azziz-Baumgartner E , Barron MA , Thompson MG , DeSilva MB . Am J Transplant 2022 22 (1) 306-314 Immunocompromised persons, defined as those with suppressed humoral or cellular immunity resulting from health conditions or medications, account for approximately 3% of the US adult population.1 Immunocompromised adults are at increased risk for severe COVID-19 outcomes2 and might not acquire the same level of protection from COVID-19 mRNA vaccines as do immunocompetent adults.3 , 4 To evaluate vaccine effectiveness (VE) among immunocompromised adults, data from the VISION Network1 on hospitalizations among persons aged ≥18 years with COVID-19–like illness from 187 hospitals in nine states during January 17–September 5, 2021 were analyzed. Using selected discharge diagnoses,2 VE against COVID-19–associated hospitalization conferred by completing a two-dose series of an mRNA COVID-19 vaccine ≥14 days before the index hospitalization date3 (i.e., being fully vaccinated) was evaluated using a test-negative design comparing 20,101 immunocompromised adults (10,564 [53%] of whom were fully vaccinated) and 69,116 immunocompetent adults (29,456 [43%] of whom were fully vaccinated). VE of two doses of mRNA COVID-19 vaccine against COVID-19–associated hospitalization was lower among immunocompromised patients (77%; 95% confidence interval [CI] = 74%–80%) than among immunocompetent patients (90%; 95% CI = 89%–91%). This difference persisted irrespective of mRNA vaccine product, age group, and timing of hospitalization relative to SARS-CoV-2 (the virus that causes COVID-19) B.1.617.2 (Delta) variant predominance in the state of hospitalization. VE varied across immunocompromising condition subgroups, ranging from 59% (organ or stem cell transplant recipients) to 81% (persons with a rheumatologic or inflammatory disorder). Immunocompromised persons benefit from mRNA COVID-19 vaccination but are less protected from severe COVID-19 outcomes than are immunocompetent persons, and VE varies among immunocompromised subgroups. Immunocompromised persons receiving mRNA COVID-19 vaccines should receive three doses and a booster, consistent with CDC recommendations,5 practice nonpharmaceutical interventions, and, if infected, be monitored closely and considered early for proven therapies that can prevent severe outcomes. |
Effectiveness of 2-Dose Vaccination with mRNA COVID-19 Vaccines Against COVID-19-Associated Hospitalizations Among Immunocompromised Adults - Nine States, January-September 2021.
Embi PJ , Levy ME , Naleway AL , Patel P , Gaglani M , Natarajan K , Dascomb K , Ong TC , Klein NP , Liao IC , Grannis SJ , Han J , Stenehjem E , Dunne MM , Lewis N , Irving SA , Rao S , McEvoy C , Bozio CH , Murthy K , Dixon BE , Grisel N , Yang DH , Goddard K , Kharbanda AB , Reynolds S , Raiyani C , Fadel WF , Arndorfer J , Rowley EA , Fireman B , Ferdinands J , Valvi NR , Ball SW , Zerbo O , Griggs EP , Mitchell PK , Porter RM , Kiduko SA , Blanton L , Zhuang Y , Steffens A , Reese SE , Olson N , Williams J , Dickerson M , McMorrow M , Schrag SJ , Verani JR , Fry AM , Azziz-Baumgartner E , Barron MA , Thompson MG , DeSilva MB . MMWR Morb Mortal Wkly Rep 2021 70 (44) 1553-1559 Immunocompromised persons, defined as those with suppressed humoral or cellular immunity resulting from health conditions or medications, account for approximately 3% of the U.S. adult population (1). Immunocompromised adults are at increased risk for severe COVID-19 outcomes (2) and might not acquire the same level of protection from COVID-19 mRNA vaccines as do immunocompetent adults (3,4). To evaluate vaccine effectiveness (VE) among immunocompromised adults, data from the VISION Network* on hospitalizations among persons aged ≥18 years with COVID-19-like illness from 187 hospitals in nine states during January 17-September 5, 2021 were analyzed. Using selected discharge diagnoses,(†) VE against COVID-19-associated hospitalization conferred by completing a 2-dose series of an mRNA COVID-19 vaccine ≥14 days before the index hospitalization date(§) (i.e., being fully vaccinated) was evaluated using a test-negative design comparing 20,101 immunocompromised adults (10,564 [53%] of whom were fully vaccinated) and 69,116 immunocompetent adults (29,456 [43%] of whom were fully vaccinated). VE of 2 doses of mRNA COVID-19 vaccine against COVID-19-associated hospitalization was lower among immunocompromised patients (77%; 95% confidence interval [CI] = 74%-80%) than among immunocompetent patients (90%; 95% CI = 89%-91%). This difference persisted irrespective of mRNA vaccine product, age group, and timing of hospitalization relative to SARS-CoV-2 (the virus that causes COVID-19) B.1.617.2 (Delta) variant predominance in the state of hospitalization. VE varied across immunocompromising condition subgroups, ranging from 59% (organ or stem cell transplant recipients) to 81% (persons with a rheumatologic or inflammatory disorder). Immunocompromised persons benefit from mRNA COVID-19 vaccination but are less protected from severe COVID-19 outcomes than are immunocompetent persons, and VE varies among immunocompromised subgroups. Immunocompromised persons receiving mRNA COVID-19 vaccines should receive 3 doses and a booster, consistent with CDC recommendations (5), practice nonpharmaceutical interventions, and, if infected, be monitored closely and considered early for proven therapies that can prevent severe outcomes. |
Effectiveness of Covid-19 Vaccines in Ambulatory and Inpatient Care Settings.
Thompson MG , Stenehjem E , Grannis S , Ball SW , Naleway AL , Ong TC , DeSilva MB , Natarajan K , Bozio CH , Lewis N , Dascomb K , Dixon BE , Birch RJ , Irving SA , Rao S , Kharbanda E , Han J , Reynolds S , Goddard K , Grisel N , Fadel WF , Levy ME , Ferdinands J , Fireman B , Arndorfer J , Valvi NR , Rowley EA , Patel P , Zerbo O , Griggs EP , Porter RM , Demarco M , Blanton L , Steffens A , Zhuang Y , Olson N , Barron M , Shifflett P , Schrag SJ , Verani JR , Fry A , Gaglani M , Azziz-Baumgartner E , Klein NP . N Engl J Med 2021 385 (15) 1355-1371 ![]() ![]() BACKGROUND: There are limited data on the effectiveness of the vaccines against symptomatic coronavirus disease 2019 (Covid-19) currently authorized in the United States with respect to hospitalization, admission to an intensive care unit (ICU), or ambulatory care in an emergency department or urgent care clinic. METHODS: We conducted a study involving adults (≥50 years of age) with Covid-19-like illness who underwent molecular testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed 41,552 admissions to 187 hospitals and 21,522 visits to 221 emergency departments or urgent care clinics during the period from January 1 through June 22, 2021, in multiple states. The patients' vaccination status was documented in electronic health records and immunization registries. We used a test-negative design to estimate vaccine effectiveness by comparing the odds of a positive test for SARS-CoV-2 infection among vaccinated patients with those among unvaccinated patients. Vaccine effectiveness was adjusted with weights based on propensity-for-vaccination scores and according to age, geographic region, calendar time (days from January 1, 2021, to the index date for each medical visit), and local virus circulation. RESULTS: The effectiveness of full messenger RNA (mRNA) vaccination (≥14 days after the second dose) was 89% (95% confidence interval [CI], 87 to 91) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization, 90% (95% CI, 85 to 93) against infection leading to an ICU admission, and 91% (95% CI, 89 to 93) against infection leading to an emergency department or urgent care clinic visit. The effectiveness of full vaccination with respect to a Covid-19-associated hospitalization or emergency department or urgent care clinic visit was similar with the BNT162b2 and mRNA-1273 vaccines and ranged from 81% to 95% among adults 85 years of age or older, persons with chronic medical conditions, and Black or Hispanic adults. The effectiveness of the Ad26.COV2.S vaccine was 68% (95% CI, 50 to 79) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization and 73% (95% CI, 59 to 82) against infection leading to an emergency department or urgent care clinic visit. CONCLUSIONS: Covid-19 vaccines in the United States were highly effective against SARS-CoV-2 infection requiring hospitalization, ICU admission, or an emergency department or urgent care clinic visit. This vaccine effectiveness extended to populations that are disproportionately affected by SARS-CoV-2 infection. (Funded by the Centers for Disease Control and Prevention.). |
Comfortable SCBA weights from biomechanical models for firefighting tasks
Xu S , Hu M , Powell J , Zhuang Z . Advances in Simulation and Digital Human Modeling AHFE 2021 Lecture Notes in Networks and Systems 2021 264 231-238 Firefighters are required to use a self-contained breathing apparatus (SCBA) for respiratory protection when engaged in a variety of firefighting duties. While the SCBA provides crucial respiratory support and protection, it is also cumbersome and heavy. Questions have arisen to address the current weight limitation listed in 42 CFR Part 84, which mandates the maximum weight of 16 kg (35.2 lbs) for an SCBA system. The objective of the overarching study is to inform a maximum comfortable SCBA weight by developing static and dynamic biomechanical models and collecting physiological burden and postural stability data to evaluate stressors for firefighting tasks. This paper presents data from the static models. Eight representative firefighting tasks (stair climb, hose carry, weighted carry, rope pull, dummy drag, hammer slam, overhaul, and hose advance) were used in the biomechanical models. Maximum comfortable SCBA weights were calculated based on three biomechanical models (abdominal extension/tension, lateral extension/tension, and abdominal rotation). This study found that the maximum comfortable weight for an SCBA was 39 lbs for the static postures of interest. Further studies with human subjects to investigate the SCBA weight limit by using physiological burden and dynamic models are underway and will provide crucial data to inform updates to the current weight limits for SCBAs allowing more features and extended durations of these devices without compromising user safety, performance, or comfort. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG. |
Comparison of ISO work of breathing and NIOSH breathing resistance measurements for air-purifying respirators
Xu SS , King WP , McClain C , Zhuang Z , Rottach DR . J Occup Environ Hyg 2021 18 (8) 1-9 The National Institute for Occupational Safety and Health's methods and requirements for air-purifying respirator breathing resistance in 42 CFR Part 84 do not include work of breathing. The International Organization for Standardization Technical Committee 94, Subcommittee 15 utilized work of breathing to evaluate airflow resistance for all classes of respiratory protective devices as part of their development of performance standards regarding respiratory protective devices. The objectives of this study were: (1) to evaluate the relationship between the International Organization for Standardization's work of breathing measurements and the National Institute for Occupational Safety and Health's breathing resistance test results; (2) to provide scientific bases for standard development organizations to decide if work of breathing should be adopted; and (3) to establish regression equations for manufacturers and test laboratories to estimate work of breathing measurements using breathing resistance data. A total of 43 respirators were tested for work of breathing at minute ventilation rates of 10, 35, 65, 105, and 135 liters per minute. Breathing resistance obtained at a constant flow rate of 85 liters per minute per National Institute of Occupational Safety and Health protocol was correlated to each of the parameters (total work of breathing, inhalation, and exhalation) obtained from the work of breathing tests. The ratio of work of breathing exhalation to work of breathing inhalation for all air-purifying respirators is similar to the ratio of exhalation to inhalation resistance when tested individually. The ratios were about 0.8 for filtering facepiece respirators, 0.5 for half-masks, and 0.25 for full-facepiece respirators. The National Institute for Occupational Safety and Health's breathing resistance is close to work of breathing's minute ventilation of 35 liters per minute, which represents the common walking/working pace in most workplaces. The work of breathing and the National Institute of Occupational Safety and Health's breathing resistance were found to be strongly and positively correlated (r values of 0.7-0.9) at each work rate for inhalation and exhalation. In addition, linear and multiple regression models (R-squared values of 0.5-0.8) were also established to estimate work of breathing using breathing resistance. Work of breathing was correlated higher to breathing resistance for full-facepiece and half-mask elastomeric respirators than filtering facepiece respirators for inhalation. For exhalation, filtering facepiece respirators were correlated much better than full-facepiece and half-mask elastomeric respirators. Therefore, the National Institute for Occupational Safety and Health's breathing resistance may reasonably be used to predict work of breathing for air-purifying respirators. The results could also be used by manufacturers for product development and evaluation. |
Evaluation of total inward leakage for NIOSH-approved elastomeric half-facepiece, full-facepiece, and powered air-purifying respirators using sodium chloride and corn oil aerosols
Rengasamy S , Zhuang Z , Lawrence RB , Boutin B , Yorio P , Horvatin M , McClain C , Harris JR , Coffey C . J Occup Environ Hyg 2021 18 (7) 1-9 Recently, total inward leakage (TIL) for filtering facepiece and elastomeric half-mask respirators (EHRs) was measured according to the International Organization for Standardization (ISO) test method standard 16900-1:2014 that showed larger TIL for corn oil aerosol than for NaCl aerosol. Comparison of TIL measured for different aerosols for higher protection level respirators is lacking. The objective of this study was to determine TIL for EHRs, full-facepiece respirators, and loose-fitting and tight-fitting powered air-purifying respirators (PAPRs) using NaCl and corn oil aerosols to compare. TIL was measured for two models each of EHRs, full-facepiece respirators, and loose-fitting and tight-fitting PAPRs. After fit testing with a PortaCount (TSI, St. Paul, MN) using the Occupational Safety and Health Administration (OSHA) protocol, eight subjects were tested in the NaCl aerosol chamber first and then in the corn oil aerosol chamber, while another eight subjects tested in the reverse order. Subjects were randomly assigned to one of the two groups. TIL was measured as a ratio of mass-based aerosol concentrations inside the mask to the test chamber while the subjects performed ISO 16900-1-defined exercises using continuous sampling methods. The concentration of corn oil aerosol was measured with one light scattering photometer, alternately, and NaCl aerosol was measured using two flame photometers. Results showed the geometric mean TIL for EHR was significantly (p < 0.05) larger for corn oil aerosol than for NaCl aerosol. EHR models equipped with P100 filters showed relatively smaller TIL values than the same models with N95 filters showing that TIL was inversely related to filter efficiency. Interestingly, TIL was significantly (p < 0.05) larger for NaCl aerosol than for corn oil aerosol for PAPRs, but not for full-facepiece respirators. TIL was inversely related to fit factors of respirator types. Overall, filter efficiency and faceseal leakage determine TIL. The relative trends in TIL for the two aerosols' test methods differ between respirator types indicating that generalization of TIL for respirator types may not be appropriate when using different test agents. |
New technique to evaluate decontamination methods for filtering facepiece respirators
Vo E , Appavoo SR , Xu S , Horvatin M , Zhuang Z . Am J Infect Control 2021 49 (4) 416-423 BACKGROUND: A major concern among health care experts is a shortage of N95 filtering facepiece respirators (FFRs) during a pandemic. One option for mitigating an FFR shortage is to decontaminate and reuse the devices. The focus of this study was to develop a new evaluation technique based on three major decontamination requirements: 1) inactivating viruses, 2) not altering the respirator properties, and 3) not leaving any toxic byproduct on the FFR. METHODS: Hydrophilic and hydrophobic FFRs were contaminated with MS2 virus. In the solution-based deposition, the virus-containing liquid droplets were spiked directly onto FFRs, while in the vapor-based and aerosol-based depositions, the viral particles were loaded onto FFRs using a bio-aerosol testing system. Ultraviolet germicidal irradiation (UVGI) and moist heat (MH) decontamination methods were used for inactivation of viruses applied to FFRs. RESULTS: Both UVGI and MH methods inactivated viruses (> 5-log reduction of MS2 virus; in 92% of both method experiments, the virus was reduced to levels below the detection limit), did not alter the respirator properties, and did not leave any toxic byproduct on the FFRs. CONCLUSIONS: Both UVGI and MH methods could be considered as promising decontamination candidates for inactivation of viruses for respirator reuse during shortages. |
Speech intelligibility test methodology applied to powered air-purifying respirators used in healthcare
Xu S , Simons J , Yorio P , Rottach D , Zhuang Z , Radonovich L . J Occup Environ Hyg 2020 18 (1) 1-11 Powered air-purifying respirators (PAPRs) are worn to protect workers from hazardous respiratory exposures in a wide range of workplaces, including healthcare. However, PAPRs may diminish the ability of wearers to correctly hear words spoken by others, potentially interfering with safe performance of healthcare duties. Accordingly, the impact of PAPRs during healthcare use on speech intelligibility (SI) and consequently on user safety, usability, and patient care is not well studied. The objectives of this study were to (1) determine a listener's ability to comprehend single-syllable words spoken by a PAPR wearer; (2) determine a PAPR wearer's ability to intelligibly hear and identify single-syllable words spoken by a PAPR wearer; (3) to assess the variability between speakers, listeners, and PAPR models; (4) to investigate the effects of PAPR design features on SI; and (5) inform a SI requirement for certifying future PAPRs for use in healthcare. This study utilized a Modified Rhyme Test to assess SI for PAPRs. The current National Institute for Occupational Safety and Health (NIOSH) methods for assessing SI are limited to the recently introduced PAPR100 respirator class and the class of respirators claiming chemical, biological, radiological, and nuclear (CBRN) protections. Four NIOSH-approved PAPRs were evaluated using four human subjects. Four experimental conditions were examined:(1) Speaker and Listener with no PAPR; (2) Speaker and Listener both wearing PAPRs; (3) Speaker with a PAPR, Listener without a PAPR; and (4) Speaker without a PAPR, Listener with a PAPR resulted in a total of 144 experiments. Statistical analysis showed that the SI performance ratings were not significantly different among the PAPR models, but experimental conditions had significant impact on SI. The pattern of SI across the conditions of the experiment also showed a significant difference depending on PAPR model. The SI performance rating for all PAPRs could meet the current NIOSH CBRN certification requirement for speech intelligibility. |
New respirator performance monitor (RePM) for powered air-purifying respirators
Grinshpun SA , Corey J , Yermakov M , Wu B , Strickland KT , Bergman M , Zhuang Z . J Occup Environ Hyg 2020 17 1-8 Powered air-purifying respirators (PAPRs) that offer protection from particulates are deployed in different workplace environments. Usage of PAPRs by healthcare workers is rapidly increasing; these respirators are often considered the best option in healthcare settings, particularly during public health emergency situations, such as outbreaks of pandemic diseases. At the same time, lack of user training and certain vigorous work activities may lead to a decrease in a respirator's performance. There is a critical need for real-time performance monitoring of respiratory protective devices, including PAPRs. In this effort, a new robust and low-cost real-time performance monitor (RePM) capable of evaluating the protection offered by a PAPR against aerosol particles at a workplace was developed. The new device was evaluated on a manikin and on human subjects against a pair of condensation nuclei counters (P-Trak) used as the reference protection measurement system. The outcome was expressed as a manikin-based protection factor (mPF) and a Simulated Workplace Protection Factor (SWPF) determined while testing on subjects. For the manikin-based testing, the data points collected by the two methods were plotted against each other; a near-perfect correlation was observed with a correlation coefficient of 0.997. This high correlation is particularly remarkable since RePM and condensation particle counter (CPC) measure in different particle size ranges. The data variability increased with increasing mPF. The evaluation on human subjects demonstrated that RePM prototype provided an excellent Sensitivity (96.3% measured on human subjects at a response time of 60 sec) and a Specificity of 100%. The device is believed to be the first of its kind to quantitatively monitor PAPR performance while the wearer is working; it is small, lightweight, and does not interfere with job functions. |
Systems genetics and systems biology analysis of paraquat neurotoxicity in BXD recombinant inbred mice.
Torres-Rojas C , Zhuang D , Jimenez-Carrion P , Silva I , O'Callaghan JP , Lu L , Zhao W , Mulligan MK , Williams RW , Jones BC . Toxicol Sci 2020 176 (1) 137-146 ![]() Paraquat (PQ) is an herbicide used in many countries, including the USA. It is also implicated as a risk factor for sporadic Parkinson's disease (sPD), especially in those living in agricultural areas and drinking well water. Studies linking PQ to sPD are not consistent however and there appears to be inter-individual differential susceptibility. One likely reason is genetically based differential susceptibility to paraquat neurotoxicity in sub-populations. To address this issue, we tested the effects of paraquat in a genetic reference population of mice (the BXD recombinant inbred strain family). In our earlier work, we showed that in genetically susceptible mice, paraquat increases iron in the ventral midbrain, the area containing the substantia nigra. Our hypothesis is that genetic variability contributes to diverse PQ-related susceptibility and iron concentration. To test this hypothesis, we treated male mice from 28-39 BXD strains plus the parental strains with one of 3 doses of paraquat, 1, 5 and 10 mg/kg three times on a weekly basis. At the end of the treatment period, we analyzed the ventral midbrain for concentrations of iron, copper, and zinc, also we measured the concentration of paraquat in cerebellum, and proinflammatory cytokines in serum and cerebellum. The effect on paraquat treated mice with 5 mg/kg and principal component analysis of iron showed suggestive QTL on chromosome 5. Overall, our results suggest that gene Prkag2 and related networks may serve as potential targets against paraquat toxicity and demonstrate the utility of genetically diverse mouse models for the study of complex human toxicity. |
A technique to measure respirator protection factors against aerosol particles in simulated workplace settings using portable instruments
Vo E , Horvatin M , Bergman M , Wu B , Zhuang Z . J Occup Environ Hyg 2020 17 (5) 1-12 The aim of this study was to develop a new method to measure respirator protection factors for aerosol particles using portable instruments while workers conduct their normal work. The portable instruments, including a set of two handheld condensation particle counters (CPCs) and two portable aerosol mobility spectrometers (PAMSs), were evaluated with a set of two reference scanning mobility particle sizers (SMPSs). The portable instruments were mounted to a tactical load-bearing vest or backpack and worn by the test subject while conducting their simulated workplace activities. Simulated workplace protection factors (SWPFs) were measured using human subjects exposed to sodium chloride aerosols at three different steady state concentration levels: low (8x10(3) particles/cm(3)), medium (5x10(4) particles/cm(3)), and high (1x10(5) particles/cm(3)). Eight subjects were required to pass a quantitative fit test before beginning a SWPF test for the respirators. Each SWPF test was performed using a protocol of five exercises for 3 min each: (1) normal breathing while standing; (2) bending at the waist; (3) a simulated laboratory-vessel cleaning motion; (4) slow walking in place; and (5) deep breathing. Two instrument sets (one portable instrument {CPC or PAMS} and one reference SMPS for each set) were used to simultaneously measure the aerosol concentrations outside and inside the respirator. The SWPF was calculated as a ratio of the outside and inside particles. Generally, the overall SWPFs measured with the handheld CPCs had a relatively good agreement with those measured with the reference SMPSs, followed by the PAMSs. Under simulated workplace activities, all handheld CPCs, PAMSs, and the reference SMPSs showed a similar GM SWPF trend, and their GM SWPFs decreased when simulated workplace movements increased. This study demonstrated that the new design of mounting two handheld CPCs in the tactical load-bearing vest or mounting one PAMS unit in the backpack permitted subjects to wear it while performing the simulated workplace activities. The CPC shows potential for measuring SWPFs based on its light weight and lack of major instrument malfunctions. |
Modeling the Genetic Basis of Individual Differences in Susceptibility to Gulf War Illness.
Jones BC , Miller DB , Lu L , Zhao W , Ashbrook DG , Xu F , Mulligan MK , Williams RW , Zhuang D , Torres-Rojas C , O'Callaghan JP . Brain Sci 2020 10 (3) ![]() Between 25% and 30% of the nearly one million military personnel who participated in the 1991 Persian Gulf War became ill with chronic symptoms ranging from gastrointestinal to nervous system dysfunction. This disorder is now referred to as Gulf War Illness (GWI) and the underlying pathophysiology has been linked to exposure-based neuroinflammation caused by organophosphorous (OP) compounds coupled with high circulating glucocorticoids. In a mouse model of GWI we developed, corticosterone was shown to act synergistically with an OP (diisopropylflurophosphate) to dramatically increase proinflammatory cytokine gene expression in the brain. Because not all Gulf War participants became sick, the question arises as to whether differential genetic constitution might underlie individual differences in susceptibility. To address this question of genetic liability, we tested the impact of OP and glucocorticoid exposure in a genetic reference population of 30 inbred mouse strains. We also studied both sexes. The results showed wide differences among strains and overall that females were less sensitive to the combined treatment than males. Furthermore, we identified one OP-glucocorticoid locus and nominated a candidate gene-Spon1-that may underlie the marked differences in response. |
Validation of Computational Fluid Dynamics Models for Evaluating Loose-Fitting Powered Air-Purifying Respirators
Bergman M , Lei Z , Xu S , Strickland K , Zhuang Z . Proc 20th Congr Int Ergon Assoc IEA 2018 I Healthc Ergon (2018) 2019 819 176-185 Loose-fitting powered air-purifying respirators (PAPRs) are used in healthcare settings to reduce exposure to high-risk respiratory pathogens. Innovative computational fluid dynamics (CFD) models were developed for evaluating loose-fitting PAPR performance. However, the computational results of the CFD models have not been validated using actual experimental data. Experimental testing to evaluate particle facepiece leakage was performed in a test laboratory using two models of loose-fitting PAPRs. Each model was mounted on a static (non-moving) advanced headform placed in a sodium chloride (NaCl) aerosol test chamber. The headform performed cyclic breathing via connection to a breathing machine. High-efficiency particulate air (HEPA)-filtered air was supplied directly to the PAPR facepiece using laboratory compressed supplied-air regulated with a mass-flow controller. One model was evaluated with six supplied-air flowrates from 50-215 L/min (Lpm) and the other model with six flowrates from 50-205 Lpm. Three different workrates (minute volumes) were evaluated: low (25 Lpm), moderate 46 (Lpm), and high 88 (Lpm). Manikin penetration factor (mPF) was calculated as the ratio of chamber particle concentration to the in-facepiece concentration. Overall, data analyses indicated that the mPF results from the simulations were well correlated with the experimental laboratory data for all data combined (r = 0.88). For data at the three different workrates (high, moderate, low) for both models combined, the r-values were 0.96, 0.97, and 0.77, respectively. The CFD models of the two PAPR models were validated and may be utilized for further research. |
Numerical Simulations of Exhaled Particles from Wearers of Powered Air Purifying Respirators
Xu SS , Lei Z , Zhuang Z , Bergman M . J Int Soc Respir Prot 2019 36 (2) 66-76 In surgical settings, infectious particulate wound contamination is a recognized cause of post-operative infections. Powered air purifying respirators (PAPRs) are worn by healthcare workers for personal protection against contaminated aerosols. Healthcare infection preventionists have expressed concern about the possibility that infectious particles expelled from PAPR exhalation channels could lead to healthcare-associated disease, especially in operative settings where sterile procedural technique is essential. This study used computational fluid dynamics (CFD) modeling to simulate and visualize the distribution of particles exhaled by PAPR wearers. Using CFD simulations, the PAPR inside to outside ratio of particle concentrations was estimated. Also, the effects of particle sizes, supplied-air flow rates, and breathing work rates on outward leakage were evaluated. This simulation study reconstructed a geometrical model of a static median headform wearing a loose-fitting PAPR by capturing a 3D image. We defined a mathematical model for the headform and PAPR system and ran simulations with four particle sizes, three breathing workloads and two supplied-air flow rates (a total 24 configurations; 4×3×2=24) applied on the digital model of the headform and PAPR system. This model accounts for exhaled particles, but not ambient particles. Computed distributions of particles inside and outside the PAPR are displayed. The outward concentration leakage was low at surgical setting, e.g., it was about 9% for a particle size of 0.1 and 1 μm at light breathing and a 205 L/min supplied-air flow rate. The supplied-air flow rates, particle sizes, and breathing workloads had effects on the outward concentration leakage, as the outward concentration leakage increased as particle size decreased, breathing workload increased, and the supplied-air flow rate decreased. The CFD simulations can help to optimize the supplied-air flow rates. When the loose-fitting PAPR is used, exhaled particles with small size (below 1μm), or heavy breathing workloads, may generate a great risk to the sterile field and should be avoided. |
Assessment of respirator fit capability test criteria for full-facepiece air-purifying respirators
Bergman MS , Zhuang Z , Xu SS , Rengasamy S , Lawrence RB , Boutin B , Harris JR . J Occup Environ Hyg 2019 16 (7) 1-9 An ASTM International subcommittee on Respiratory Protection, F23.65 is currently developing a consensus standard for assessing respirator fit capability (RFC) criteria of half-facepiece air-purifying particulate respirators. The objective of this study was to evaluate if the test methods being developed for half-facepiece respirators can reasonably be applied to nonpowered full-facepiece-air-purifying respirators (FF-APR). Benchmark RFC test data were collected for three families of FF-APRs (a one-size-only family, a two-size family, and a three-size family). All respirators were equipped with P100 class particulate filters. Respirators were outfitted with a sampling probe to collect an in-mask particle concentration sample in the breathing zone of the wearer. Each of the six respirator facepieces was tested on the National Institute for Occupational Safety and Health 25-subject Bivariate Panel. The RFC test assessed face seal leakage using a PortaCount fit test. Subjects followed the corresponding Occupational Safety and Health Administration-accepted fit test protocol. Two donnings per subject/respirator model combination were performed. The panel passing rate (PPR) (number or percentage of subjects in the panel achieving acceptable fit on at least one of two donnings) was determined for each respirator family at specified fit factor passing levels of 500, 1,000, and 2,000. As a reasonable expectation based on a previous analysis of alpha and beta fit test errors for various panel sizes, the selected PPR benchmark for our study was >75%. At the fit factor passing level of 500 obtained on at least one of two donnings, the PPRs for three-, two-, and one-size families were 100, 79, and 88%, respectively. As the fit factor passing criterion increased from 500 to 1,000 or 2,000, PPRs followed a decreasing trend. Each of the three tested families of FF-APRs are capable of fitting >/=75% of the intended user population at the 500 fit factor passing level obtained on at least one of two donnings. The methods presented here can be used as a reference for standards development organizations considering developing RFC test requirements. |
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