Correspondence - Evaluation of a basic point-of-care ultrasound course for residents in internal medicine.

Point-of-care ultrasound (POCUS) integrates imaging into the physical examination at the bedside. This offers the advantage of instant clinical information and has shown to speed up the diagnostic process, and to improve diagnostic accuracy and correct treatment.

The implementation of POCUS and POCUS training for residents: the Rijnstate approach.

Point-of-care ultrasound (POCUS) is gaining interest in intensive care medicine and good reviews and guidelines on POCUS are available. Unfortunately, how to implement POCUS and practical examples how to train staff and junior doctors is not well described in literature. We discuss the process of POCUS implementation, and a POCUS training program for residents prior to their intensive care rotation in a Dutch teaching hospital intensive care unit. The described four-day basic POCUS course consists of short tutorials and ample time for hands-on practice. Theoretical tests are taken shortly before, on the last day of the course, and after three months to assess learning retention. Practical tests are taken on the last day of the course and after three months. We stress the importance of POCUS for intensive care and hope that our experiences will help colleagues who also want to go forward with POCUS.

Keratinocytes and neutrophils are important sources of proinflammatory molecules in hidradenitis suppurativa.

BACKGROUND: The pathogenesis of the chronic inflammatory skin disease hidradenitis suppurativa (HS, also known as acne inversa) involves epidermal alterations such as psoriasiform epidermal hyperplasia and keratin plugging. Keratinocytes are an important source of proinflammatory molecules in inflammatory skin diseases and can be stimulated by interleukin (IL)-17(+) cells. OBJECTIVES: To explore the possible role of the epithelium in the pathogenesis of HS. METHODS: We performed immunohistochemical stainings and Western blot experiments to investigate the localization and expression of inflammation-associated molecules, including the cytokine IL-17, components of the inflammasome including caspase-1, and the endogenous danger-associated molecular pattern molecules S100A8 and S100A9 (calprotectin). To examine a possible effect of upregulated proinflammatory cytokines on the inflammatory infiltrate, differences in the cellular composition of perifollicular and deep dermal infiltrates were analysed. RESULTS: The number of IL-17(+) cells is increased in lesional and perilesional HS skin. The epidermis produces proinflammatory molecules and shows an upregulated expression of components of the NLRP3 inflammasome, activated caspase-1 and expression of S100A8/S100A9. Additionally, the course of the inflammatory process in HS involves influx of innate immune cells, particularly IL-17-expressing neutrophils. CONCLUSIONS: IL-17-producing cells are present in lesional and perilesional HS skin and may contribute to the initiation of inflammatory processes. Furthermore, the epidermis is a source of proinflammatory cytokines, shows inflammasome activation and expresses S100A8/S100A9, thereby possibly contributing to the propagation of inflammation. A massive influx of IL-17-expressing neutrophils is observed in the deep infiltrate.

Position and intensity of system (eigen) peaks in capillary zone electrophoresis.

The intensity of system (or eigen) peaks encountered in capillary zone electrophoresis (CZE) can be predicted by considering mass balances for each of the analyte constituents and each of the constituents in the background electrolyte (BGE). As a result of coherence, in each zone the proportions in which the constituent concentrations vary are fixed; they are determined by the composition of the BGE and the nature of the analyte constituent (if present) and described as eigenvectors of a transport matrix. Considering the effect of an injection, the mass balances for all constituents can be satisfied only via the intensity of each zone. This leads to an n-equations, n-unknowns problem, with the intensities as the unknowns and the mass balances as equations. The latter can be easily solved to obtain the intensities. of the zones, of analytes as well as of system peaks. In this work the approach has been applied to CZE systems with two co-ions in the BGE, and experimental results have been compared to the predictions obtained from the model. Agreement was seen to be reasonable, but the quantitative comparison often failed, probably due to experimental difficulties.

Mass transfer in rectangular chromatographic channels.

Rectangular channels are explored nowadays for use in chromatographic and electrophoretic separations, especially after the possibilities of micromachining have become available to separation scientist. Expressions for plate heights expected for such experiments with an infinite channel width has been given by Giddings, while Golay derived the effect of finite channel width for unretained components. However, it remains unclear how the classical equations for plate height for retained components should be modified when the effect of finite channel width is taken into account. Also, the application of electroosmotic propulsion of the mobile phase leads to a flow profile different from the Poiseuille-type profile assumed in the above treatments, and no equations seem to be available for this situation. In this work, these problems have been addressed by an approach involving numerical Fourier transforms. Expressions for the plate height contribution from mobile phase mass transfer as a function of characteristic length dc (the height of the channel, or the diameter for open cylindrical systems, OT), mean mobile phase velocity, um, diffusion coefficient Dm, retention factor, k', and width-to-height ratio, phi, can always be written as: H = dc2um/DmF(k', phi). For cylindrical open systems, F(k', phi) equals 1/96 (1 + 6k' + 11k'2)/(1 + k')2, the well-known Golay equation. In the present work, this is taken as a reference point; results are cast in the form F(k', n) = (A + Bk' + Ck'2)/(1 + k')2, where A, B and C replace the factors 1/96, 6/96 and 11/96 of the Golay equation. Values of A, B and C are reported for various values of phi. This is done for a selection from the large variety of conditions that can be imagined: Coating on one, two or four walls of the channel, non-uniform or uniform coating, pressure-driven (Poiseuille-type) or electro-osmotically-driven flow, surface charge on one, two of four walls, etc. It is found that the effect of finite channel width is large for unretained solutes (plate height for a wide channel is nearly eight times larger than that predicted when the finite channel width is ignored), whereas the plate height increase with retention is in many cases influenced only slightly.

Determination of the molecular mass distribution of synthetic polymers by size-exclusion electrochromatography.

The performance of size-exclusion electrochromatography (SEEC) for the mass distribution analysis of synthetic polymers was studied and compared to conventional, pressure-driven size-exclusion chromatography (SEC). Electroosmotic flow control, within-day, day-to-day and column-to-column repeatability were determined for SEEC with respect to retention and separation efficiency. It was shown that by using the retention ratio instead of the migration time, the precision of the mass distribution calculations is sufficiently high, and that similar distributions were obtained for a sample analyzed by pressure-driven SEC and by SEEC. Furthermore, hexafluoroisopropanol was demonstrated to be a new and potent solvent for SEEC. It was used for the separation of narrow polymethylmethacrylate standards and several commercially important polymers such as polycarbonate, polycaprolactam and poly(ethylene terephthalate), using UV detection in the deep UV region (195-230 nm).

Effects of pore flow on the separation efficiency in capillary electrochromatography with porous particles.

The effect of pore flow on the separation efficiency of capillary electrochromatography (CEC) has been studied using columns packed with particles with different pore sizes. A previously developed model was used to predict the (relative) pore flow velocity in these columns under various experimental conditions. Equations are derived describing the effect of pore flow on peak broadening in CEC. The theory has been compared with practice in the reversed-phase CEC separation of various polyaromatic hydrocarbons. It is shown, by theory and experimentally, that the mass-transfer resistance contribution to peak dispersion can be effectively eliminated when using porous particles with a high (> or =50 nm) average pore diameter. Moreover, at high pore-to-interstitial flow ratios the flow inhomogeneity contribution (the A term in the plate height equation) is also shown to decrease. Under optimal conditions, a reduced plate height of 0.3 for the nonretained compound could be obtained. It is argued that fully perfusive porous particles can be a more efficient separation medium in CEC than nonporous particles.

Size-exclusion electrochromatography with controlled pore flow.

In size-exclusion electrochromatography (SEEC) there exists an optimum in pore-to-interstitial flow ratio with respect to the resolution. Two methods for finding and controlling the optimal pore-to-interstitial flow ratio in SEEC have been studied: (i) varying the ionic strength of the mobile phase and (ii) the application of a hydrodynamic flow in addition to the electrco-driven flow. Both methodologies have been evaluated in terms of efficiency and applicability with columns packed with silica particles containing pores of either 10 or 50 nm in diameter, and with different ionic strength mobile phases. Using the first method with the 10-nm pore particles, the flow ratio could be adjusted within an appropriate range. However, with the wide-pore (50 nm) particles it appeared that the pore-to-interstitial flow ratio was too high at all conditions tested to obtain proper selectivity. In the second approach, the desired pore flow was generated by the electric field and the pore-to-interstitial flow ratio could then be adjusted by an applied pressure over the column. This method was applicable with both particle types studied. The application of a (low) voltage gradient in addition to a pressure-driven flow resulted in a sharply improved separation efficiency as a result of a strongly improved mass transfer due to intra-particle electroosmotic flow. When optimized, pressurized SEEC generates identical separation efficiencies for polystyrene standards as are obtained with pure SEEC, while the reduction in selectivity, in comparison to pressure-driven SEC, is kept minimal.

Modelling of the pore flow in capillary electrochromatography.

Pore flow in capillary electrochromatography (CEC) on porous silica particles has been investigated. To that end the migration behaviour of narrow polystyrene (PS) standards dissolved in di-methylformamide (DMF) with lithium chloride in 1 and 10 mmol/l concentration has been measured. These data have been compared to theoretical predictions. The latter were based on a model comprising cylindrical pores of varying diameter as measured experimentally by porosimetry, while the flow in each set of pores was calculated with the expression given by Rice and Whitehead. A reasonable to good agreement between experimental and predicted data was observed, provided it was assumed that pores of differing diameter occur in series. It was found that the flow in pores with a nominal size of 100 A can be considerable compared to the interstitial flow, especially at 10 mmol/l ionic strength. It is concluded that pore flow within porous particles in CEC, of great importance for improved efficiency in both interactive and exclusion type CEC, can be predicted fairly reliably by means of the Rice and Whitehead expression.