Optimisation of ultraclean air. The role of instrument preparation

The use of ultraclean air (UCA) in operating theatres reduces the infection rate after joint replacement but some cases of infection still occur. We investigated one possible source of contamination, namely the setting up of instruments in a conventional plenum-ventilated preparation room. We measured bacterial fallout using agar settle plates and compared instruments set up in the preparation room with those set up in the UCA theatre, assessed the effect of covering instruments after preparation and compared fallout during their preparation with total fallout throughout the operation. Our findings showed that covering the instruments reduced total bacterial fallout fourfold by reducing the exposure time, particularly during periods of increased activity and bacterial dispersal. Preparation in the UCA theatre and subsequent covering of the instruments reduced total fallout 28-fold. All measurable bacterial fallout occurred during the setting up and not during surgery.     

Influence of operating room surface contamination on surgical wounds: a prospective study

The influence of operating room contamination on wound infection rates in clean, clean-contaminated, contaminated, and septid procedures was studied by a prospective randomized study of 2,020 surgical wounds. Operating room surface contamination was assessed by the RODAC bacterial plate method. Control rooms uniformly received Wet-Vac cleaning between operations. Experimental rooms were not cleaned between consecutive clean operations, but were cleaned after contaminated operations. The difference in surface contamination between groups of experimental and control rooms was found to be significant at the P less than .05 level. Patients operated on in experimental and control rooms were followed up postoperatively to assess whether they experienced wound infection. No statistically significant differences in wound infection rates were found between experimental and control room operations as total groups, clean procedures, or operations of long duration.     

Theatre footwear: a health hazard?

Theatre footwear frequently appears to be contaminated with blood. We assessed objectively the nature and degree of contamination of theatre shoes after cleaning. Two hundred pairs of theatre shoes were randomly selected from three hospitals in South East Wales. Hospital 1 (H1), 100 pairs of shoes, Hospital 2 (H2), 40, Hospital 3 (H3), 60. They were examined for general appearance, the presence of bacterial pathogens and blood, using a leuchomalachite green assay. The majority of shoes were dirty, 63% in H1, 80% in H2, and 95% in H3. Six per cent of shoes in H1, 2.5% in H2 and 0% in H3 were contaminated with staphylococcus aureus. No shoes were contaminated with pseudomonas aeruginosa. Thirty six per cent of shoes in H1, 40% in H2 and 57% in H3 were contaminated with blood. In H1 it was possible to determine the grade of staff to whom the shoes belonged. Fifty eight per cent of consultant surgeons' shoes tested positive for blood, 50% of junior surgeons, 16% of operating department assistants and none of nurses' theatre shoes. The high level of blood contamination following cleaning may pose a potential HIV or hepatitis B risk to patients, manual shoe cleaner and surgeons. We have demonstrated that current shoe cleaning practices are ineffective. We propose methods that should eliminate this risk. Procedures will need to be defined.     

An audit of theatre scrubrooms in a district general hospital

While much has been written on surgical theatre design, little can be found on the design of theatre scrubrooms. An audit of theatres at a modern district general hospital (DGH) revealed that only one scrubroom had the minimum free floor space required and none complied with other baseline parameters. A survey of surgeons revealed that 60% had to re-scrub because their hands had desterilised through insufficient scrubroom space. The implications for hygiene hazards are clear. We review the literature and outline the basic dimensions which should be incorporated in the design of modern theatre scrubrooms.     

Extraperitoneal cyst of the right spermatic cord

Student placements in operating theatres are being discontinued in some hospitals. Here, the author explores the reasons for this and highlights what nursing students can achieve during a placement in theatre.     

Influence of local air suction on the density of air-borne bacteria during cementation of alloplasties

At joint replacement operations local air suction is used to reduce the air pollution from organic solvents in the operation theatre during insertion of cement and prosthesis. In order to find out whether the local suction in an ultraclean-air operation theatre with laminar airflow influenced the number of colony forming units (cfu) of bacterial in vicinity of the wound, one m3 of air was sampled 20 cm and one metre from the wound before, during and after use of local suction during insertion of cement and prosthesis using a Sartorius membrane filter sampler. There was no significant difference between the groups in the numbers of cfu of bacteria found. It is concluded that use of local air suction over the operative area while cementing hip prosthesis does not affect the number of bacteria in the vicinity of the operation.     

Ultraclean laminar airflow ORs

To minimize postoperative infections, ultraclean laminar airflow (LAF) units equipped with high-efficiency particulate air filters developed for electronic and aerospace technology have been adapted for ORs. Traditionally, the airflow was either vertical or horizontal and, to function properly, encompassed extra side walls inside the OR. Recently, new airstream technology has provided zoned down-flow units that provide an exponential airflow (i.e., resembling an upside-down trumpet mouth). The exponential airflow allows for omission of extra side walls, making them more versatile in clinical use. Each different type of LAF requires knowledge of airstream patterns and how OR team members need to dress and work to prevent contamination of the sterile air and the aseptic areas. This article discusses different LAF systems and related demands on OR clothing and behavior.     

Economic assessment of low flow anesthesia with analysis of the break-even point. Experience at an underutilized operating room

BACKGROUND: Many authors indicate the importance of economic saving obtained with the use of the inhalation rebreathing anaesthesia instead of non rebreathing anaesthesia, always referring to parameters which are the duration of anesthesia (1 hour) and the use of the operating theatre each year. It is presumed that the utilization of rebreathing system is at least a 1.000 hours/year. However it is not necessary that all the operating theatres employ 1.000 hours/year in rebreathing anesthesia. This method requires annual depreciation costs of the capital invested for the purchase of new adequate ventilators, to modificative those already existing and guarantee adequate monitoring and the maintenance of these equipment. The importance is stressed of individuating a method of economical evaluation comparing the effective savings obtained with the real utilization of rebreathing anesthesia for each operating theatre and the costs of purchasing and maintaining the equipment. From our point of view the break-even point analysis has demonstrated to be a consistent instrument for the evaluation of the real economic advantage of rebreathing system in each hospital. METHODS: It is suggested to utilize a conventional formula for the determination of the break even point, which means the minimal number of hours for year that justifies economically the adoption of rebreathing anaesthesia. RESULTS AND CONCLUSIONS: An example of this analysis has been applied for an operating theatre in the hospital of Morbegno, where the major utilization of regional anaesthesia leads to a reduced number hours/year of rebreathing anesthesia which remains anyhow economically advantageous.     

Designing an anaesthesia data management system for a medium size country hospital. A report of four years experiences

By the end of 1990 the anaesthesia department of the Offenburg hospital, a 500 bed hospital, started to install a data management system in the main operating theatres. In a first phase, 23 PCs were installed in 7 induction rooms and 7 theatres as well as in the 9-bed recovery-room. All PCs are connected via ethernet to a VAX-server. The main functions of the system may be summarized as follows: 1) On-line data acquisition from the patient monitor and from the anaesthesia machine (the ventilator); 2) Off-line data entry of other variables including drugs, fluids and postop. orders as well as demographic and administrative data; 3) Data transfer from induction room to theatre and from theatre to the recovery room; 4) Printout of an automatic anaesthesia record at the end of each case--a hand-written protocol no longer required; 5) Storage of data-files on the VAX-server with possibility of reviewing individual cases and also of performing all types of statistical analysis. The set-up of the whole system including 12 ICU beds and other workstations (total of 42 PC-stations) is described as well as hard- and software used. Problems encountered during installation of hardware and experiences during implementation of software are briefly discussed. A short overview is given concerning future development.     

The kidneys in aging]

In this study, we investigated indoor air quality and symptoms of respiratory illness in 264 nursing workers at 28 day-care centers in Taipei. Geometric mean concentrations of indoor and outdoor bacteria were 735 colony-forming units in air (CFU/m3) and 384 CFU/m3, respectively. In addition, geometric mean concentrations of indoor and outdoor fungi were 1,212 CFU/m3 and 1,032 CFU/m3, respectively. Aspergillus, Cladosporium, and Penicillium-microfungi that occurred most commonly-were found indoors and outdoors. Geometric mean concentrations of house dust mite allergens, Der p I and Der p V, were 58 ng/g dust and 14 ng/g dust, respectively. In addition, the observed high prevalence of dampness or mold problems in the day-care centers indicated that dampness was very common in this subtropical region. We found a significant relationship between dampness and work-related sick building syndrome in the day-care-center workers. Furthermore, concentrations of fungi were lower in the day-care centers equipped with air conditioners/air cleaners than in centers that lacked such equipment. Also, Aspergillus was associated strongly with work-related sick building syndrome in the day-care-center workers.     

Airborne fiber concentrations during splitting open and boxing bags of asbestos

Measured airborne concentrations of asbestos are often unavailable to assess different epidemiologic estimates of past personal exposure levels or concentrations near specific operations involving handling asbestos. The purpose of this study was to assess the potential use of a laboratory study in estimating exposure to asbestos in operations that ceased for many years. The asbestos transfer operations were simulated by splitting and boxing 4.5-kg paper bags of chrysotile asbestos in an enclosed chamber ventilated at 28.2 air changes per hour (ACH). Two recirculation fans achieved chamber air mixing. The airborne concentration of asbestos fibers was determined by sampling air through membrane filters at a rate of 10 l/min and by analysing fibers by phase contrast optical microscopy to determine 15-min average airborne concentrations. Samplers were located at four equidistant locations from the operation. Opening a maximum of seven bags in 15 min was associated with an asbestos-in-air concentration of less than 2 x 10(-6) fibers/m3 (f/m3) in splitting open and boxing and less than 0.85 x 10(-6) f/m3 in boxing of pre-split bags. The measured airborne asbestos concentration exhibited a linear trend with the number of bags opened per 15 min. The empirical results were utilised to model fiber concentrations for various ventilation rates. It was concluded that the distribution of the operation within the workday and the ventilation rate are the two most important variables in the determination of the estimated time-weighted average concentration. Splitting open and boxing 32 bags of asbestos over an 8-h period at a rate of 4 bags/h over an 8-h period results in a calculated time-weighted average exposure of about 1 x 10(-6) f/m3 in a work space with 20 ACH and approximately 7 x 10(-6) f/m3 in a work space with 2 ACH. Splitting open and boxing at a rate of 12 bags/h for 2 h and 45 min yielded calculated concentrations less than one-half of the above mentioned values. These results should serve as a useful benchmark for epidemiologists concerned with the magnitude of exposure in historically dusty industrial tasks.     

Role of platelet-activating factor in glucose uptake and utilization of different tissues

The particle transport characteristics of two ventilation configurations commonly used in hospital operating rooms (ORs), cross-flow and impinging-flow ventilation, were investigated. The computational fluid dynamics software FLUENT was used to simulate turbulent airflow with mixed convection in a three-dimensional, rectangular OR. Two OR personnel, a patient, OR spotlights, an anesthetics cart, and an operating table were represented in the room. Heat loads from the personnel, patient, and lights affected the airflow through buoyancy. Particles produced at the operation site with various sizes and initial conditions were tracked through the room. A stochastic model was used to include the random effects of turbulence on particle trajectories. Simulation results show that heat loads from the personnel, patient, and OR spotlights had an important effect on the airflow through natural convection. Particle trajectories were influenced greatly by the flow field structure, particle launch position, and turbulence in the flow, and somewhat by particle size. However, particle paths were insensitive to the launch velocity. Virtually identical trajectories were obtained for particles with launch velocities ranging from 0 to 1 m/sec in magnitude. Changes in ventilation configuration dramatically affected particle transport. The cross-flow ventilation configuration performed better, based on the criteria of removing particles from the breathing zone of room occupants. Proper flow field design and contaminant source placement can be used to control particle transport. Numerical simulations allow quick and inexpensive comparisons between room designs and provide details about airflow and contaminant transport.     

Steinert''s congenital myotonic dystrophy. Genetic aspects

The study of the air contamination was carried out in six fruit farms located in the region of Grójec and Warka. The measurements were carried out during the application of "Fastac 10EC" insecticide (alphamethrin) in fruit growing at work sites of tractor drivers operating the sprayers. The mean concentrations of alphamethrin at individual work sites were low and ranged between 0.001 and 0.0039 mg/m3 of the air. Due to the lack of maximum allowable concentration (MAC), the inhalation toxicity of alphamethrin of 320 mg/m3 (4-h), toxicity class of alphamethrin (III) and MAC of natural pyrethrum were considered. In this context the determined concentrations seem to be safe.     

Carbon monoxide and water vapor contamination of compressed breathing air for firefighters and divers

Compressed breathing air, used in self-contained breathing apparatus (SCBA) by firefighters and other categories of workers as well as by recreational and commercial divers, is prepared with the aid of high-pressure compressors operating in the range of 5000 psig. There have been reports of unexplained deaths of SCUBA divers and anecdotal accounts of decreased time to exhaustion in firefighters using SCBAs. Compressed breathing air has been found to contain elevated levels of carbon monoxide (CO) and water vapor that are consistent with carboxyhemoglobin (COHb) poisoning and freezing of the user's regulator on the breathing apparatus. The Coburn-Forster-Kane equation (CFK equation) was used to estimate COHb levels at rest and at maximum exercise when exposed to different levels of CO in contaminated breathing air. The results demonstrated that, at maximum exercise, the COHb ranged from 6.0 to 17% with the use of 1 to 4 SCBA cylinders contaminated by 250 ppm CO. Standard operating procedures have been developed at the Montreal Fire Department to minimize the risk of compressed breathing air contamination. Results of the quality analysis/quality control program indicate that implementation of these procedures has improved the quality of the compressed breathing air. Recommendations are made for improvement of the air testing procedures mandated by the Canadian CAN3 180.1-M85 Standard on Compressed Breathing Air and Systems.     

Nature and amount of aerial pollutants from livestock buildings

The air in animal housing contains gases, odours, dust particles and microorganisms which are discharged by way of the ventilation system into the environment. There is increasing concern within parts of the population that these compounds may affect the respiratory health of people living close to livestock enterprises. A brief survey is presented on airborne emissions from livestock buildings. About 136 gaseous compounds are analysed in animal house air of which only 22 are quantified. The most environment-related compounds are ammonia and methane. It is assumed that German animal husbandry emits up to 750,000 Mg ammonia per year. The concentrations of airborne microorganisms in livestock buildings are between some 100 and several 1000 per liter. Staphylococcae, streptococcae, colilike bacteria, fungi, moulds and yeasts are regularly found. The 24 h average concentrations of dust in animal barns vary considerably. In poultry houses the highest inhalable resp. respirable dust concentrations (up to 10 mg/m3 resp. 1.2 mg/m3) were found, followed by pig houses (5.5 mg/m3) and cattle barns (1.22 mg/m3 resp. 0.17 mg/m3). The concentrations of endotoxins in the airborne dust can range from 0.6 ng/m3 (cattle, respirable dust) to 860 ng/m3 (laying hens, inhalable dust). The presently discussed occupational health threshold at the workplace is around 5 ng/m3 (50 EU/m3). The emission rate for respirable dust from piggeries is at about 60 mg/h, from poultry houses nearly 300 mg/h and from cattle barns at 20 mg/h, related to 500 kg liveweight of the animals. Little is known about the distances these particles are transported through the air outside the animal buildings.     

Application of PAP-2 aluminum powder to produce powdered composite materials: The features of technology,structure, and physicomechanical properties of composites. Part I. Process approaches providing the formation of composite materials and applied procedures for determining their physicomechanical properties

Composites Al/Al₂O₃ (lamellar cermet matrix)–filler (discrete metallic fibers, duralumin chips, graphite particles, fused corundum grains, and technical alumina spherulites) are fabricated. To form the lamellar cermet matrix, industrially produced PAP-2 aluminum powder was used. This powder consists of scaled particles with stearin coating (the specific surface of the powder is 4.1322 m²/g, and its particle size varies from 0.03 to 10 μm). In order to form the composites, the following main process operations were used: heat treatment of the PAP-2 powder in air to burn out stearin from the particle surface and replace it with a passivating alumina film, mixing of the thus formed powder product with a filler, and compaction and reaction sintering of powder billets in the filtration burning mode in air. To fabricate the Al/Al₂O₃–C composite, a new approach based on the saponification chemical reaction of stearin is proposed. This reaction runs between stearin on the surface of aluminum particles and caustic soda, which is the product of hydrolysis of the diluted liquid glass introduced into initial powder. The reaction products (sodium stearate and glycerol) are decomposed during the subsequent heat treatment in air with the formation of a coke residue on the particle surface. The physicochemical properties of the composites were determined using standard and conventional procedures.     

基于Ventsim的深井线性热源对有效通风量的影响分析

随着矿产资源开采深度的日益增加,深井通风因其通风网络规模大、环境复杂等,面临着成本及能耗高的问题。考虑到深井高温环境具有大量且便利的热能,基于对深井温差能可利用性的理论分析,通过在回风井深部设置线性热源,运用Ventsim数值模拟的方法,研究了线性热源作用下温差能对矿井有效通风量的影响。结果表明：在矿井巷道干球温度处于25~48 ℃的范围内,线性热源的温度提升与矿井有效风量的提高呈正相关,且回风井内二者呈近似线性相关,但对于矿井底部风量基础值较小的水平巷道,回风井内线性热源对其有效风量的提升不明显;在线性热源作用下,不同的温度递增设置方案对于有效风量的提升也有一定影响,在线性热源温差范围相同的情况下,对温差间隔进行小幅度、多区间的合理设置,有利于提高温差能的利用率。     

Ventilation and hypoxic ventilatory responsiveness in Chinese-Tibetan residents at 3,658 m

When breathing ambient air at rest at 3,658 m altitude, Tibetan lifelong residents of 3,658 m ventilate as much as newcomers acclimatized to high altitude; they also ventilate more and have greater hypoxic ventilatory responses (HVRs) than do Han ("Chinese") long-term residents at 3,658 m. This suggests that Tibetan ancestry is advantageous in protecting resting ventilation levels during years of hypoxic exposure and is of interest in light of the permissive role of hypoventilation in the development of chronic mountain sickness, which is nearly absent among Tibetans. The existence of individuals with mixed Tibetan-Chinese ancestry (Han-Tibetans) residing at 3,658 m affords an opportunity to test this hypothesis. Eighteen men born in Lhasa, Tibet, China (3,658 m) to Tibetan mothers and Han fathers were compared with 27 Tibetan men and 30 Han men residing at 3,658 m who were previously studied. We used the same study procedures (minute ventilation was measured with a dry-gas flowmeter during room air breathing and hyperoxia and with a 13-liter spirometer-rebreathing system during the hypoxic and hypercapnic tests). During room air breathing at 3,658 m (inspired O2 pressure = 93 Torr), Han-Tibetans resembled Tibetans in ventilation (12.1 +/- 0.6 vs. 11.5+/- 0.5 l/min BTPS, respectively) but had HVR that were blunted (63 +/- 16 vs. 121 +/- 13, respectively, for HVR shape parameter A) and declined with increasing duration of high-altitude residence. During administered hyperoxia (inspired O2 pressure = 310 Torr) at 3,658 m, the paradoxical hyperventilation previously seen in Tibetan but not Han residents at 3,658 m (11.8 +/- 0.5 vs. 10.1 +/- 0.5 l/min BTPS) was absent in these Han-Tibetans (9.8 +/- 0.6 l/min BTPS). Thus, although longer duration of high-altitude residence appears to progressively blunt HVR among Han-Tibetans born and residing at 3, 658 m, their Tibetan ancestry appears protective in their maintenance of high resting ventilation levels despite diminished chemosensitivity.     

淮钢焦炉除尘系统改造实践

淮钢焦化厂捣固焦炉二合一地面站除尘系统,存在布袋压差阻力过大,除尘器本体着火烧仓,炉顶烟气干管、导烟车过烧等问题。通过增加3个单体燃烧室、1套不锈钢混风室及将卧式燃烧室改成立式等改造导烟车,增大炉顶干管通风量,重力除尘器改为冷却灭火器等,解决了除尘系统故障,除尘效果较好,装煤过程排放颗粒物质量浓度35.9～71.3mg/m3,出焦过程排放颗粒物质量浓度24.0～61.2mg/m3。     

Removal of Indoor Airborne Bacteria by Nano-Ag/TiO2 as Photocatalyst: Feasibility Study in Museum and Nursing Institutions

Deterioration of indoor air quality attributable to airborne bacterial consortia is a widespread environmental problem. The main objective of this study is to evaluate the feasibility of applying the syngetic effect of nano-Ag/TiO2 as a photocatalyst and UV light to enhance the disinfecting capability of full-scale bacterial restraining equipment on-site in the National Museum of Natural Science and a medical-nursing institute. The influence of initial counts of total airborne bacteria and volume of space on the efficiency of bacterial restraining have been studied. In the case of museum application, a higher initial total bacterial count leads to better bacterial restraining rates; Site A (initial total bacterial counts = 506??CFU/m3) has the best bacterial restraining rate (92%) as compared with Site B (69%, initial total bacterial counts = 158??CFU/m3) and Site C (80%, initial total bacterial counts = 338??CFU/m3) after 24 h of operation. Higher initial counts of total airborne bacteria lead to an increasing bacterial restraining rate. Approximately 92% (Site A) and 74% of restrained bacterial rate were observed in a museum and nursing institutions, respectively, under the similar initial total airborne bacterial counts (506, 598??CFU/m3). The results illustrate that changes in the volume of space do not have significant inhibitory effects on the efficiency. The proposed equipment can disinfect air to restrain bacteria effectively, as demonstrated on-site in museums and nursing institutions; the results will be valuable references for designing a full-scale commercialized device for large-scale applications in the future.