An evaluation of hospital special-ventilation-room pressures.

OBJECTIVE: To quantitate the magnitude and consistency of positive (airflow out) and negative (airflow in) hospital special-ventilation-room (SVR) airflow. DESIGN: A room-pressure evaluation was conducted during two seasons on a total of 18 rooms: standard rooms, airborne infection isolation rooms, and protective environment rooms. The pressures were measured using a digital pressure gauge-piezoresistive pressure sensor that measured pressure differentials. With doors closed, the rooms were measured a minimum of 30 times each for a cooling season and a heating season. RESULTS: The standard rooms showed the least amount of variability in pressure differential, with an average of -0.2 Pa (median, -0.2 Pa), and an interquartile range (IQR) of 0.4 Pa. Airborne infection isolation rooms showed more variability in pressure, with an average of -0.3 Pa (median, -0.2 Pa) and an IQR of 0.5 Pa. Protective environment rooms had the greatest fluctuation in pressure, with an average of 8.3 Pa (median, 7.7 Pa) and an IQR of 8.8 Pa. Dramatic pressure changes were observed during this evaluation, which may have been influenced by room architectural differences (sealed vs unsealed); heating, ventilation, and air-conditioning zone interactions; and stack effect. CONCLUSION: The pressure variations noted in this study, which potentially affect containment or exclusion of contaminants, support the need for standardization of pressure requirements for SVRs. To maintain consistent pressure levels, creating an airtight seal and continuous pressure monitoring may be necessary.

Testing the reliability and validity of a measure of safety climate.

The lack of compliance with universal precautions (UP) is well documented across a wide variety of healthcare professions and has been reported both before and after the enactment of the Occupational Safety and Health Administration's Bloodborne Pathogens Standard. Gershon, Karkashian, and Felknor (1994) found that several factors correlated significantly with healthcare workers' lack of compliance with UP, including a measure of organizational safety climate (e.g., the employees' perception of their organizational culture and practices regarding safety). We conducted a secondary analysis using data from a cross-sectional survey of a convenience sample of 1,746 healthcare workers at risk of occupational exposure to bloodborne pathogens to assess the validity and reliability of Gershon's measure of safety climate. Findings revealed no relationship between safety climate and employees' gender, age, education, tenure in position, profession, hours worked per day, perceived risk, attitude toward risk, and training. An association was demonstrated between safety climate and (1) healthcare worker compliance with UP and (2) the availability of personal protective equipment, providing support for the construct validity of this measure of safety climate. These findings could be used by occupational health professionals to assess employees' perceptions of the safety culture and practices in the workplace and to guide the institution's risk management efforts in association with U.P.

Microbial bioburden in endoscope reprocessing and an in-use evaluation of the high-level disinfection capabilities of Cidex PA.

Most endoscopy clinics use 2% glutaraldehyde as a high-level disinfectant for reprocessing flexible endoscopes. However, even with contact times greater than 30 minutes, survival of organisms has been documented. We compared the high-level disinfection capabilities of glutaraldehyde (45-minute immersion) with a new peracetic acid germicide (20- to 25-minute immersion). Channels, valve housings, and outer sheaths were sampled to quantify bioburden levels after a patient procedure, after manual cleaning, and after disinfection. Total mean bioburden after clinical use was greater than 6 log10 colony-forming units (CFU). Manual cleaning reduced the bioburden by means of 4.7 log10 CFU (gastroscopes) and 6.2 log10 CFU (colonoscopes). High-level disinfection with the new product was achieved in five of six (product stressed by EPA Reuse Test) and 7 of 10 (product stressed by dilution and organic load) successfully disinfected endoscopes, whereas glutaraldehyde achieved it in 4 of 10 (product stressed by dilution and organic load). We conclude that the new peracetic acid product (20- and 25-minute contact time) is at least as effective as glutaraldehyde (45-minute contact time) for reducing the bioburden of vegetative aerobic organisms in endoscopes.

Improved methods for generation, sampling, and recovery of biological aerosols in filter challenge tests.

In preparation for filter efficiency tests and sampler comparison studies, methods of biological aerosol generation, sampling, and filter recovery were modified from previous studies. Methods described include (1) techniques for generating aerosols that reduced nuisance particles to negligible levels and increased the cell culturability of Mycobacterium abscessus by 30%, (2) sampling techniques that lowered the detectable range of biological particle size from 0.65 to 0.45 micron and reduced the sampling flow from the chamber from 28.3 to 1.5 L/min, and (3) development of methods to remove culturable organisms from respirator filter media. These methods were developed for filter challenge tests with M. abscessus and were applied to two other bacteria. They may also have application to a wider variety of organisms and bioaerosol assessments.

Collection of three bacterial aerosols by respirator and surgical mask filters under varying conditions of flow and relative humidity.

A variety of respirator filters and surgical masks were challenged with three aerosolized bacteria: Mycobacterium abscessus (M.a.) (a rod), Staphylococcus epidermidis (S.e.) (a sphere), and Bacillus subtilis (B.s.) (a rod). Tests were conducted at two flow rates (45 and 85 l./min) and two humidity levels (30 and 70%). Aerosols were measured with a total-particle, direct-reading, spectrometer and a viable particle cascade impactor. Measurements up- and downstream of the filter or mask were used in determining aerosol penetration; respirator or surgical mask fit was not evaluated. Bioaerosol penetration measured with two aerosol sampling instruments was found to correlate. Additionally, bioaerosol test parameters were evaluated with respect to their effect on penetration. Increasing flow resulted in increased penetration of all organisms while an increase in relative humidity did not exert a consistent effect on all organisms. Of the respirators approved by the National Institute for Occupational Safety and Health (NIOSH), filter efficiency was as expected with dust/mist respirators having the lowest and HEPA filters the highest efficiency. Surgical masks were the least efficient of all filters tested; these are not certified by NIOSH. Bioaerosol penetration was compared to that of a polystyrene latex sphere (PSL) aerosol. Penetration of the test aerosols was predicted on the basis of particle aerodynamic diameter and was expected to be in this order: PSL > M.a. > S.e. = B.s. The PSL aerosol was the most penetrating, as predicted. However, results showed that B.s. was more penetrating than S.e. The aerodynamic diameter may not be the best parameter for predicting aerosol penetration of non-spherical particles in these filters.

Compliance with universal precautions among physicians.

This study characterized and assessed self-reported levels of compliance with universal precautions (UP) among hospital-based physicians, and determined significant factors associated with both compliance and noncompliance. The physicians (n = 322) were a subgroup of a larger study population of hospital-based health care workers recruited from three geographically distinct locations (n = 1746), and were surveyed using a detailed confidential questionnaire that assessed personal, work-related, and organizational factors. Compliance with UP was measured through 11 items that examined how often physicians followed specific recommended work practices. Compliance was found to vary among the 11 items: they were high for certain activities (eg, glove use, 94%; disposal of sharps, 92%) and low for others (eg, wearing protective clothing, 55%; not recapping needles, 56%). Compliance with all items was low (31% to 38%). Stepwise logistic regression revealed that noncompliant physicians were likely to be age 37 or older, to report high work stress, and to perceive a conflict of interest between providing patient care and protecting themselves. Compliant physicians were more likely to be knowledgeable and to have been trained in universal precautions, to perceive protective measures as being effective, and to perceive an organizational commitment to safety.

Compliance with universal precautions among health care workers at three regional hospitals.

OBJECTIVE: To assess and characterize self-reported levels of compliance with universal precautions among hospital-based health care workers and to determine correlates of compliance. DESIGN: Confidential questionnaire survey of 1716 hospital-based health care workers. PARTICIPANTS: Participants were recruited from three geographically distinct hospitals. A stratified convenience sample of physicians, nurses, technicians, and phlebotomists working in emergency, surgery, critical care, and laboratory departments was selected from employment lists to receive the survey instrument. All participants had direct contact with either patients or patient specimens. RESULTS: For this study, overall compliance was defined as "always" or "often" adhering to the desired protective behavior. Eleven different items composed the overall compliance scale. Compliance rates varied among the 11 items, from extremely high for certain activities (e.g., glove use, 97%; disposal of sharps, 95%) to low for others (e.g., wearing protective outer clothing, 62%; wearing eye protection, 63%). Compliance was strongly correlated with several key factors: (1) perceived organizational commitment to safety, (2) perceived conflict of interest between workers' need to protect themselves and their need to provide medical care to patients; (3) risk-taking personality; (4) perception of risk; (5) knowledge regarding routes of HIV transmission; and (6) training in universal precautions. Compliance rates were associated with some demographic characteristics: female workers had higher overall compliance scores than did male workers (25% of female and 19% of male respondents circled "always" or "often" on each of the 11 items, p < 0.05); and overall compliance scores were highest for nurses, intermediate for technicians, and lowest for physicians. Overall compliance scores were higher for the mid-Atlantic respondents (28%) than for those from the Southwest (20%) or Midwest (20%, p = 0.001). CONCLUSIONS: This study supports earlier findings regarding several compliance correlates (perception of risk, knowledge of universal precautions), but it also identifies important new variables, such as the organizational safety climate and perceived conflict of interest. Several modifiable variables were identified, and intervention programs that address as many of these factors as possible will probably succeed in facilitating employee compliance.

Evaluation of a rapid readout biological indicator for 121 degrees C gravity and 132 degrees C vacuum-assisted steam sterilization cycles.

OBJECTIVE: A biological indicator (BI), based on fluorescent detection of a spore-associated enzyme, has been developed. We evaluated the new BI against five conventional self-contained BIs in a 121 degrees C gravity-displacement sterilizer and, packaged in towel packs and disposable steam test packs, in a 132 degrees C vacuum-assisted sterilizer. DESIGN: In the 121 degrees C gravity-displacement sterilizer, rapid readout BIs and conventional BIs were tested together in an otherwise empty chamber. Exposure times were 5, 10, and 15 minutes. In the 132 degrees C vacuum-assisted steam sterilizer, BIs were contained in towel packs or disposable steam test packs. Surgical packs were added to represent a full load. Exposure times were 0, 1, and 2 minutes. RESULTS: In gravity-displacement 5-minute cycles, the rapid readout BIs yielded 100% positive results within 30 minutes. The conventional BIs ranged from 72% to 100% positive in 48 hours. At 10 minutes, the rapid readout BIs were 83% positive after 3 hours, whereas the conventional BIs ranged from 0% to 37% positive after 48 hours. All indicators were negative after 15-minute exposures. In vacuum-assisted cycles, all indicators were negative after 3 minutes. After 1-minute exposures, the rapid readout BIs were 40% to 60% positive, whereas the conventional BIs were 15% to 20% positive. CONCLUSION: The rapid readout BIs are a more sensitive indicator of marginal steam sterilization cycles than conventional self-contained BIs. They yield results within 3 hours, as compared to 24 to 48 hours for the conventional BIs.

Respiratory protection devices.

OSHA authority and responsibility have led to the requirement that health care workers potentially exposed to patients with active tuberculosis in situations where engineering controls are not feasible for protection must utilize personal protective equipment at least equivalent to HEPA respirators. ICPs generally believe that this approach is unnecessarily conservative and imposes undue burdens on patient care. The arguments on both sides of this controversy have some merit. Reported cases of tuberculosis and skin-test conversions among health care workers since 1988 and the absence of a demonstrated safe level of exposure have led many to the conclusion that HEPA respirators are justified. On the other side, tuberculosis currently is not a major problem in some areas of the country, and many believe that less stringent personal protective devices (e.g., DM respirators) may provide protection equivalent to HEPA filters--at least in terms of preventing infection if not in terms of filtration efficiency. They believe that the lesser discomfort and lower cost associated with DM respirators justify the argument for a more flexible standard. Perhaps additional research can help to resolve the remaining controversy. Definitive answers are unlikely to surface quickly, however, and it is likely that the controversy and confusion will continue for at least awhile longer.

Atrial natriuretic peptide fragments in dogs with experimental heart failure.

1. This study in the canine arteriovenous (AV) fistula model of high-output heart failure (HOHF) evaluated the chronic temporal changes in plasma ANF and pro ANF 31-67 and their relationship to body-fluid balance and the renin-aldosterone axis. In addition, the haemodynamic, hormonal and renal excretory effects of synthetic pro ANF 31-67 infusions were examined in normal and AV fistula dogs with compensated HOHF. 2. Following the construction of the AV fistula, the dogs exhibited chronic parallel elevations in right atrial pressure and the plasma concentrations of ANF and pro ANF 31-67. The gradual increases in the two peptides were associated with a gradual decrease in plasma renin activity and the re-establishment of sodium balance. 3. In normal and compensated AV fistula dogs, synthetic pro ANF 31-67 produced similar significant reductions in arterial blood pressure, right atrial pressure and elevations in urinary sodium excretion. These effects were not associated with increases in plasma or urinary cyclic GMP (cGMP). 4. These results suggest that the elevation in the endogenous circulating levels of pro ANF 31-67 in the AV fistula dogs may represent one chronic adaptive mechanism to achieve body fluid homeostasis. Furthermore, via potentially different mechanisms of action, ANF and pro ANF 31-67 may coordinate and contribute to the regulation of haemodynamic and renal function during physiological and pathophysiological situations.

Evaluation of single-use masks and respirators for protection of health care workers against mycobacterial aerosols.

BACKGROUND: The recent increase in multidrug-resistant tuberculosis has spawned a major controversy concerning the degree of respiratory protection needed by health care workers, particularly during sputum-inducing procedures. The objective of this study was to measure the filtration efficiencies of a single-use submicron surgical mask, two disposable dust/mist respirators, a dust/mist/fume respirator, and a high-efficiency particulate air respirator against aerosolized mycobacteria. Facial fit was not addressed. METHODS: In a specially designed enclosed test apparatus, an aerosol was generated with a Collison nebulizer from a known concentration of Mycobacteria chelonae, used as a surrogate for Mycobacterium tuberculosis. Aerosol concentrations were measured with Anderson samplers upstream and downstream of the test masks and respirators, which were heat sealed to a metal plate. RESULTS: Mean efficiencies ranged from approximately 97% for the surgical mask and a dust/mist respirator to more than 99.99% for the high-efficiency particulate air respirator. Measurements of filter efficiency with an Aerodynamic Particle Sizer for the M. chelonae aerosol and independent challenge tests with latex spheres correlated closely with measurements of M. Chelonae collection efficiency determined with Andersen samplers. CONCLUSIONS: Analysis of variance and Tukey's method for multiple comparisons indicated that the dust/mist/fume respirator and the HEPA respirator collected M. chelonae with significantly greater efficiency than did either the surgical mask or the dust/mist respirator. Even the least efficient mask tested, however, had a filter efficiency of more than 97% against particles averaging less than 1 micron in aerodynamic diameter.

Cross-sectional epidemiological study of respiratory disease in turkey farmers.

This study was a cross-sectional epidemiological investigation of respiratory disease in farmers involved in the turkey growing industry. Pulmonary function tests and health history questionnaires were administered to a total of 95 turkey farmers throughout Minnesota. Respiratory symptoms were greatest during the winter months when exposure to environmental agents was highest. Prevalence of symptoms was higher for smokers, personnel who worked in hen barns, and for persons who had worked in the turkey growing industry for more than 10 years. Pulmonary function was found to decrease during the work day. Also, pulmonary function was lowest for personnel working in hen bars, and for persons who had been employed in the industry for more than 10 years. These data support the association between respiratory disease and exposure to the environment in confinement farm buildings.

Significant factors in the disinfection and sterilization of flexible endoscopes.

BACKGROUND: Many nosocomial infection outbreaks have been linked to improper disinfection of the flexible endoscopes used in hospitals and clinics. The objective of this study was to evaluate the efficacy of scope disinfection with glutaraldehyde and hydrogen peroxide in manual and mechanical protocols. METHODS: Bacillus subtilis and Pseudomonas cepacia were the test organisms. Each channel in two different endoscopes was seeded and evaluated separately. Residual chemical germicide levels in the channels and in the work environment were also measured. RESULTS: Parametric analyses were carried out on log transformations of number of colony-forming units recovered. Repeated measures analysis demonstrated that both the type of disinfectant and the method of washing were significant factors for disinfection. CONCLUSIONS: Hydrogen peroxide proved to be more efficacious than glutaraldehyde for killing or removing B. subtilis in a 10-minute contact period. Automatic disinfection was more efficacious than manual disinfection for killing or removing B. subtilis in a 10-minute contact period. The channel being disinfected also proved to be a significant factor, with carbon dioxide and elevator channels the most difficult to disinfect consistently.

Fluorimetric Detection of a Bacillus stearothermophilus Spore-Bound Enzyme, alpha-d-Glucosidase, for Rapid Indication of Flash Sterilization Failure.

A biological indicator based on fluorimetric detection within 60 min of a Bacillus stearothermophilus spore-bound enzyme, alpha-d-glucosidase, has been developed. Results indicate that the enzyme survived slightly longer than spores observed after 24 h of incubation. The new system shows promise for evaluating flash sterilization cycles within 60 min compared with conventional 24-h systems.

Vapor-phase hydrogen peroxide as a surface decontaminant and sterilant.

The feasibility of utilizing vapor-phase hydrogen peroxide (VPHP) as a surface decontaminant and sterilant was evaluated in a centrifuge application. The prototype VPHP decontamination system, retrofitted into a Beckman L8-M ultracentrifuge, was designed to vaporize a 30% (wt/wt) solution of aqueous hydrogen peroxide continuously injecting and withdrawing VPHP in a deep-vacuum flow-through system. VPHP cycles of 4, 8, 16, and 32 min were examined for cidal activity against spores of Bacillus subtilis subsp. globigii and Bacillus stearothermophilus. Spore inocula (approximately 10(6)/coupon) were dried onto 0.5-in. (1.27-cm)-square stainless-steel coupons, and coupons were suspended in the centrifuge chamber, the space between the refrigeration can and the barrier ring (inner gap), and the space between the barrier ring and the vacuum ring (outer gap). At a chamber temperature of 4 degrees C, B. subtilis subsp. globigii spores were inactivated within 8 min, while inactivation of spores located in the outer gap at 27 degrees C required 32 min. The elevated temperature and high surface area/volume ratios in the outer gap may serve to decompose the gas more rapidly, thus reducing cidal efficacy. Of the two test spores, B. stearothermophilus was more resistant to VPHP. Nonetheless, VPHP was shown to possess significant sporicidal capability. For practical decontamination applications of the type described, VPHP shows promise as an effective and safer alternative to currently used ethylene oxide or formaldehyde vapors.

Laboratory-acquired infections and injuries in clinical laboratories: a 1986 survey.

A mail survey of all 54 US State and Territorial Public Health Laboratories and the 165 Hospital Clinical Laboratories in Minnesota was carried out, soliciting information on laboratory-acquired infections and injuries for calendar year 1986. The aggregate infection incidence rates were 3.5/1,000 full-time equivalent (FTE) workers for hospital laboratories and 1.43/1,000 for public health laboratories. Injury rates were 21.2/100 FTE workers for hospital laboratories and 7.21/100 for public health labs.

Microbiological evaluation of wet and dry floor sanitization systems in hospital patient rooms.

A new system for sanitizing floors in hospital patient rooms has been developed. The method consists of dry dusting with a cotton-blend, chemically treated (10% by dry mop weight) dust mop. This method was compared with a conventional cleaning protocol consisting of an initial predusting with the same nongermicidal chemical (3% by dry mop weight) followed by wet mopping with a fresh solution of a quaternary ammonium disinfectant-detergent. Each of six rooms was sampled by using RODAC plates (Becton Dickinson Labware, Oxnard, Calif.) on 10 consecutive days for each of the two methods. The study was initially performed during the summer and then repeated during the winter. Results imply that there is no significant difference between the new dry method (81.9% CFU reduction) and the conventional method (83.1% CFU reduction). Furthermore, the initial dry dusting step in the conventional method accounted for virtually all of the reduction by that method. Thus, wet mopping with a germicidal chemical produced no additional significant reduction of natural microbial populations on environmental surfaces beyond that achieved by dry dusting with dust-suppressant chemicals.

Rapid assay for in situ identification of coagulase-positive staphylococci recovered by membrane filtration from swimming pool water.

A rapid, in situ thermonuclease test that identifies colonies of Staphylococcus aureus among staphylococci isolated from swimming pool water by membrane filtration recovery on various selective and differential media is described.