Effects of emissions from different type of residential heating upon cyclic guanosine monophosphate (cGMP) in blood platelets of residents.

We hypothesized that different types of residential heating would be associated with different levels of indoor carbon monoxide (CO) and further that this might result in a differential in the concentration of cyclic 3':5' guanosine monophosphate (cGMP) in blood platelets in exposed residents. Individuals, who were recruited from homes using different fuel for heating, donated a venous blood sample in the winter and in the summer. In the winter the median blood platelet cGMP value for the group using liquid propane gas (LPG) was 65% higher than for the group using piped natural gas for heating (p <0.001). Also in the group using LPG, the median concentration of cGMP in the winter was 39% higher than the summer median (p < 0.003). The mean indoor concentrations of CO were measured over a period of 1 week during the winter and were <1 ppm. We conclude that observed differences were associated with emissions from different types of heating but that CO exposure alone is too low to explain these.

Effects on patients with asthma of eradicating visible indoor mould: a randomised controlled trial.

BACKGROUND: It is not clear whether associations between respiratory symptoms and indoor mould are causal. A randomised controlled trial was conducted to see whether asthma improves when indoor mould is removed. METHODS: Houses of patients with asthma were randomly allocated into two groups. In one group, indoor mould was removed, fungicide was applied and a fan was installed in the loft. In the control group, intervention was delayed for 12 months. Questionnaires were administered and peak expiratory flow rate was measured at baseline, 6 months and 12 months. RESULTS: Eighty-one houses were allocated to the intervention group and 83 to the control group; 95 participants in 68 intervention houses and 87 in 63 control houses supplied follow-up information. Peak expiratory flow rate variability declined in both groups, with no significant differences between them. At 6 months, significantly more of the intervention group showed a net improvement in wheeze affecting activities (difference between groups 25%, 95% CI 3% to 47%; p = 0.028), perceived improvement of breathing (52%, 95% CI 30% to 74%; p<0.0001) and perceived reduction in medication (59%, 95% CI 35% to 81%; p<0.0001). By 12 months the intervention group showed significantly greater reductions than the controls in preventer and reliever use, and more improvement in rhinitis (24%, 95% CI 9% to 39%; p = 0.001) and rhinoconjunctivitis (20%, 95% CI 5% to 36%; p = 0.009). CONCLUSIONS: Although there was no objective evidence of benefit, symptoms of asthma and rhinitis improved and medication use declined following removal of indoor mould. It is unlikely that this was entirely a placebo effect.

Occupational exposure of midwives to nitrous oxide on delivery suites.

AIMS: To compare environmental and biological monitoring of midwives for nitrous oxide in a delivery suite environment. METHODS: Environmental samples were taken over a period of four hours using passive diffusion tubes. Urine measurements were taken at the start of the shift and after four hours. RESULTS: Environmental levels exceeded the legal occupational exposure standards for nitrous oxide (100 ppm over an 8 hour time weighted average) in 35 of 46 midwife shifts monitored. There was a high correlation between personal environmental concentrations and biological uptake of nitrous oxide for those midwives with no body burden of nitrous oxide at the start of a shift, but not for others. CONCLUSIONS: Greater engineering control measures are needed to reduce daily exposure to midwives to below the occupational exposure standard. Further investigation of the toxicokinetics of nitrous oxide is needed.

Biological monitoring of midwives' exposure to N(2)O using the Bio-VOC breath sampler.

The use of exhaled breath as a biological monitoring tool is still not widely used. Although there are now commercially available kits, there are limited data on biological guidance values for all but a few substances for breath monitoring. The study investigated the possibility of using an indirect breath sampler to measure the levels of nitrous oxide in the exhaled breath of midwives at a midpoint during their shift. Levels of nitrous oxide in the exhaled breath were measured at (0-727 ppm) with a mean level of 64 ppm. The correlation between the established personal environmental monitoring and exhaled breath monitoring was generally poor as was the correlation between duration of nitrous oxide exposure and levels in the exhaled breath. Clearly the use of exhaled breath as a tool for biological monitoring is more appropriate than other invasive procedures. The breath sampler used has been a readily acceptable tool for occupational hygiene monitoring in a busy hospital ward.

Environmental monitoring of nitrous oxide during dental anaesthesia.

AIM: The study was carried out to see if levels of nitrous oxide in dental theatres and community dental clinics were being controlled in accordance with the Control of Substances Hazardous to Health Regulations. SETTING: A multi-centre study looked at exposure levels in a dental teaching hospital and two community dental clinics in the South Wales area between 1997 and 1998. METHODS: A MIRAN infra-red spectrophotometer was used to measure static levels of nitrous oxide during general anaesthesia and conscious sedation. NIOSH method 6600 was used to collect personal samples of the individual administering the anaesthetic. RESULTS: The results showed compliance with the regulations when averaged out over an 8 hour time weighted average. However, over short periods of time peak concentrations of up to 1190 ppm were observed through static sampling, and up to 734 ppm through personal sampling. CONCLUSIONS: The results highlighted the need to provide adequate control measures such as anaesthetic gas scavenging, to reduce occupational exposure to dental staff in dental operating theatres and community dental clinics, therefore providing a safe working environment.

Staff exposure to anaesthetic gases in theatre and non theatre areas.

Environmental monitoring of anaesthetic gases was carried out in theatre areas in eight hospitals as well as in Delivery suites, radiology, radiotherapy and Dental suites. High staff exposures occurred in nontheatre areas although exposures in theatres were generally satisfactory. Environmental control measures are required where staff exposures exceed legal standards.

An environmental survey of compliance with Occupational Exposure Standards (OES) for anaesthetic gases.

Environmental monitoring of nitrous oxide and volatile agents was carried out between August 1996 and October 1997 within operating theatre areas in eight hospitals within the Bro Taf Health Authority. Static monitoring and personal sampling were undertaken to assess compliance with the Occupational Exposure Standards introduced in January 1996 by the Health and Safety Executive for anaesthetic agents. The monitoring concentrated on nitrous oxide with the results showing that compliance was being achieved. Limited monitoring was carried out of the volatile agents, which again were well below the Occupational Exposure Limits. Monitoring was also carried out in nontheatre areas in which anaesthetic agents were used. The results show that many of these locations, such as delivery suites and radiology units, have inadequate ventilation and no anaesthetic gas scavenging, both of which combined to produce levels that exceeded the standards.

Should radiologists image and report sacroiliac joints in patients referred for examination of the lumbar spine?

It is routine to image the sacroiliac joints (SIJs) in patients referred for radiographic examination of the lumbar spine but there were only two consistent with ankylosing spondylitis in a review of 392 radiographic reports of lumbar spine examinations. A more sensible policy would be to only image and report on the SIJs if the clinical history were indicative of ankylosing spondylosis.

Parametric release for EtO sterilization.

The use of microwave spectroscopy as a process-control monitor to measure ethylene oxide (EtO) is an exciting breakthrough in EtO sterilization. Technologies employed until now have lacked the specificity or long-term stability to measure EtO, but microwave spectrometers now in EtO facilities have shown consistent and accurate results. This article explains the technology.

Compliance with guidelines for choice of radiographic projections: a multicentre study.

A study of compliance with guidelines for choice of radiographic projections was carried out in each of six centres. The study concerned 5851 examinations undertaken by 116 radiographers under the supervision of 29 consultant radiologists. The results showed good compliance between centres for examination of the chest (range 81-93%), abdomen (range 73-100%), thoracic spine (range 82-96%), pelvis/hip (range 78-99%) but not for examination of cervical spine (range 0-85%), paranasal sinus (range 0-100%) and lumbar spine (range 52-84%). The reasons given for these wide variations are discussed and estimates are given for the potential reductions in exposure to the UK population consequent upon national implementation of guidelines such as these.

Sterilisation of implantable devices.

The pathogenesis and rates of infection associated with the use of a wide variety of implantable devices are described. The multi-factorial nature of post-operative periprosthetic infection is outlined and the role of sterilisation of devices is explained. The resistance of bacterial spores is highlighted as a problem and a full description is given of the processes of sterilisation by heat, steam, ethylene oxide, low temperature steam and formaldehyde, ionising radiation and liquid glutaraldehyde. Sterility assurance and validation are discussed in the context of biological indicators and physical/chemical indicators. Adverse effects upon the material composition of devices and problems of process control are listed. Finally, possible optimisations of the ethylene oxide process and their potential significance to the field of sterilisation of implants is explored.

Computerized model for accurate determination of ethylene oxide diffusion in sterilized medical supplies.

A computerized numerical model is described which is shown to be more generally applicable than analytical methods in the determination of ethylene oxide diffusion in polymeric material. Diffusion coefficients of ethylene oxide in poly(vinyl chloride) were determined from the rates of desorption both for conventional aeration with warm air and for microwave-assisted desorption and found to be concentration dependent. The model takes account of device geometry and concentration dependence of diffusion coefficient and its predictions are in agreement with experimental results for desorption. The model is also used to simulate the whole sterilization process with a view to a planned diminution of EO residuals after sterilization.

Enhancement of the kinetics of the aeration of ethylene oxide sterilized polymers using microwave radiation.

Ethylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i.e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i.e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (c) dependent and the relationship which best describes this dependence was D(c) alpha ln c. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost-effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equipment.

Microwave desorption: a combined sterilizer/aerator for the accelerated elimination of ethylene oxide residues from sterilized supplies.

Ethylene oxide gas is widely used in medical and related facilities for low-temperature sterilization of surgical devices. Evidence of its toxicity and, in particular, its mutagenicity and carcinogenicity provide sufficient reasons for caution in its use and for minimizing exposure. Little advancement has been made in the removal of ethylene oxide residuals from plastics into which the gas is heavily absorbed during sterilization, despite the fact that the gas has been used for 20 years or more. This article describes a novel process (PCT Application/GB85/00509) in which microwave irradiation of ethylene oxide-sterilized materials is utilized to enhance the rate at which the gas is desorbed. The experimental apparatus is described, and an explanation of the effect of microwaves on the energy of activation for diffusion is given. Data are presented in support of the authors' claim of a 400% improvement in the efficiency of the new process over conventional aeration procedures. The advantages and economy of an integrated sterilizer/microwave-enhanced desorber are discussed in the context of the implications that arise from the current regulatory debate.

Variation in repeat rates between 18 radiology departments.

A comprehensive analysis of repeat rates has been obtained from an observational study of radiological practice in diagnostic X-ray departments throughout Wales. Interdepartmental and intradepartmental repeat rates are investigated for chest, abdomen, pelvis, sinus, lumbar spine, cervical spine and intravenous pyelographic examinations. The confounding effects upon observed repeat rates of trainee practitioners and automatic exposure control devices are also considered. The overall proportions of total film cost and patient exposure attributable to repeat radiographs are estimated to be 10% and 14% respectively.