The impact of canister geometry on chemical biological radiological and nuclear filter performance: A computational fluid dynamics analysis

Steady-state axisymmetric simulations using the Reynolds-Averaged Navier-Stokes equations have been carried out in order to optimize the performance of a Chemical, Biological, Radiological, and Nuclear (CBRN) canister filter for its use in a powered air-purifying respirator (PAPR). Alterations have been made to the shape of the canister, the spacing of the rear wall of the canister with regard to the carbon filter, and the bracketing between (i) the particulate filter and the carbon bed and (ii) the carbon bed and the canister wall. The pressure drops across the canister and the residence time distribution at the rear of the carbon bed have been analyzed in detail based on an extensive parametric analysis involving the aforementioned variations. It has been demonstrated that the non-uniform porosity profile of the carbon bed resulted in alternating regions of high and low velocity close to the canister wall, providing a possible route for breakthrough. Designs, which included a bracket at the rear of the carbon bed, blocked this route and consequently had a longer minimum mean residence time than those, which did not. It has also been shown that the spacing between the carbon bed and the canister rear wall had a large impact on both residence time and pressure drop. In cases where the carbon backed directly onto the canister rear wall flow in the axial direction from the outside wall toward the canister axis resulted in far greater pressure drop and a reduction in minimum mean residence time within the carbon bed.     

Four years' experience of a ROTEM®-guided algorithm for treatment of coagulopathy in obstetric haemorrhage

We report four years of observational data from a large UK hospital and tertiary referral unit, following the introduction of a rotational thromboelastometry-guided algorithm for treatment of coagulopathy in major obstetric haemorrhage. Fibrinogen concentrate was used to treat acquired hypofibrinogenaemia as defined by a FibTEM A5 value of < 7 mm, or 7–12 mm with ongoing or high risk of haemorrhage. Of 32,647 deliveries over 4 years, 893 (2.7%) women had an estimated blood loss ≥ 1500 ml. Two-hundred and three (23%) of these had a FibTEM A5 ≤ 12 mm and 110 received fibrinogen concentrate. We compared clinical outcomes and blood product use with 52 patients who met the same criteria, over a 12-month pre-intervention period during which shock packs were used. In the algorithm group, there was a significant reduction in the number of units (p < 0.0001) and total volume (p = 0.0007) of blood products transfused, with a reduction in transfusion-associated circulatory overload (p = 0.002). Women with placental abruption exhibited more severe coagulopathy and required higher doses of fibrinogen concentrate than women who bled due to other causes. Analysis of rotational thromboelastometry results demonstrated that coagulopathy is not observed in all women who suffer obstetric haemorrhage and cannot be predicted solely by blood loss. Therefore, formulaic treatment with blood products is not justified. When coagulopathy does occur, it appears to be multifactorial and can be severe. Point-of-care testing allows early identification and individualised treatment of coagulopathy. This is supported by the improved outcomes reported.     

Error rates in proficiency testing in Australia

ABSTRACT

Recent criticism of forensic science has focused on the fundamental aspects of the science, including the lack of supporting empirical studies, validation, accreditation, limitations and error rates. Proficiency tests are an essential component of accreditation and can be used to evaluate laboratory performance and identify systematic issues within components of the service provision. In 2016 we reported on the results of an analysis of 3176 CTS proficiency tests undertaken between 2005 and 2015 by Australian government service providers. The data analysed represented 43 unique CTS test types and covered 21 disciplines. Here we present further data from 2016 to 2017 and compare these results with those obtained from the previous study. These combined results further demonstrate that errors exist even though practitioners know they are examining proficiency tests and the tests undergo a review process. This study illustrates the need to continue to monitor trends in proficiency test results and also further highlights the need for well-designed, relevant, blind error rate studies to determine the approximate error rates for casework.