Thoracic size-selective sampling of fibres: performance of four types of thoracic sampler in laboratory tests.

The counting of fibres on membrane filters could be facilitated by using size-selective samplers to exclude coarse particulate and fibres that impede fibre counting. Furthermore, the use of thoracic size selection would also remove the present requirement to discriminate fibres by diameter during counting. However, before thoracic samplers become acceptable for sampling fibres, their performance with fibres needs to be determined. This study examines the performance of four thoracic samplers: the GK2.69 cyclone, a Modified SIMPEDS cyclone, the CATHIA sampler (inertial separation) and the IOM thoracic sampler (porous foam pre-selector). The uniformity of sample deposit on the filter samples, which is important when counts are taken on random fields, was examined with two sizes of spherical particles (1 and 10 microm) and a glass fibre aerosol with fibres spanning the aerodynamic size range of the thoracic convention. Counts by optical microscopy examined fields on a set scanning pattern. Hotspots of deposition were detected for one of the thoracic samplers (Modified SIMPEDS with the 10 microm particles and the fibres). These hotspots were attributed to the inertial flow pattern near the port from the cyclone pre-separator. For the other three thoracic samplers, the distribution was similar to that on a cowled sampler, the current standard sampler for fibres. Aerodynamic selection was examined by comparing fibre concentration on thoracic samples with those measured on semi-isokinetic samples, using fibre size (and hence calculated aerodynamic diameter) and number data obtained by scanning electron microscope evaluation in four laboratories. The size-selection characteristics of three thoracic samplers (GK2.69, Modified SIMPEDS and CATHIA) appeared very similar to the thoracic convention; there was a slight oversampling (relative to the convention) for d(ae) < 7 microm, but that would not be disadvantageous for comparability with the cowled sampler. Only the IOM thoracic sampler tended to undersample the fibres relative to the thoracic convention. With the data divided into four classes based on fibre length, the size-selection characteristics appeared to be unaffected by fibre length for GK2.69, Modified SIMPEDS and CATHIA. Only the IOM thoracic sampler (with the foam selector) showed slightly lower selection for longer length classes of fibres. These results indicate that the tested samplers follow the thoracic sampling convention for fibres, and may be used to improve the quality and reliability of samples that are taken when there is likely to be significant background dust.

A collaborative European study of personal inhalable aerosol sampler performance.

Following the adoption of new international sampling conventions for inhalable, thoracic and respirable aerosol fractions, a working group of Comité Européen de Normalisation (CEN) drafted a standard for the performance of workplace aerosol sampling instruments. The present study was set up to verify the experimental, statistical and mathematical procedures recommended in the draft performance standard and to check that they could be applied to inhalable aerosol samplers. This was achieved by applying the tests to eight types of personal inhalable aerosol sampler commonly used for workplace monitoring throughout Europe. The study led to recommendations for revising the CEN draft standard, in order to simplify the tests and reduce their cost. However, some further work will be needed to develop simpler test facilities and methods. Several of the samplers tested were found to perform adequately with respect to the inhalable sampling convention, at least over a limited range of typical workplace conditions. In general the samplers were found to perform best in low external wind speeds, which are the test conditions thought to be closest to those normally found in indoor workplaces. The practical implementation of the CEN aerosol sampling conventions requires decisions on which sampling instruments to use, estimation of the likely impact that changing sampling methods could have on apparent exposures, and adjustment where necessary of exposure limit values. The sampler performance data obtained in this project were affected by large experimental errors, but are nevertheless a useful input to decisions on how to incorporate the CEN inhalable sampling convention into regulation, guidance and occupational hygiene practice.

Efficiency and cost-effectiveness of advanced EMS in West Germany.

A model study was performed by an economist in Lower Frankonia (a mostly rural area of West Germany with several urban centers) to examine the efficiency and cost-effectiveness of the emergency medical service that included prehospital physician presence. To perform this examination about $3.5 million were spent to improve organization and communication within the local emergency medical service, to purchase additional equipment and further emergency vehicles, and to install prehospital emergency physician service. The median response time was lowered to 6 minutes. This report surveys whether these reforms and extra fundings were beneficial and cost-efficient.

Digital cine angiographic evaluation of pulmonary blood flow velocity in ventricular septal defect.

Forty-one routine right ventricular cineangiograms of children with ventricular septal defect (VSD) were evaluated with a digital image processing system. The purpose was to extract from the cineangiogram functional images that would provide information about pulmonary blood flow in these patients. The time delay of the contrast bolus between the main pulmonary artery and peripheral lung fields was measured and called "arrival time." By measuring the arrival time in three different points of each lung (apex, horizontal, basis), it was possible to express the mean arrival time for both lungs in a single figure. A group of patients without heart disease showed an arrival time of 1.3 +/- 0.3 seconds. In VSD with increased pulmonary blood flow from the left to right shunt, the arrival time decreased to 0.76 +/- 0.2 seconds. An increase in pulmonary vascular resistance with reduced L-R shunt led to an increased arrival time of 1.4 +/- 0.4 seconds.