Theoretical and experimental approaches of liquid entry pressure determination in membrane distillation processes

Membrane distillation (MD) is a thermally driven separation process that employs a hydrophobic membrane as a barrier for the liquid phase, allowing only vapor phase to pass through the membrane pores. Wetting of membrane pores by liquid streams (i.e. the loss of hydrophobic characteristics of membranes) is a crucial issue in MD treatment. This paper is organized into two parts. The first part provides an overview of the theoretical background of wetting phenomenon and guides the reader through the experimental techniques presented in the literature for determining liquid entry pressure (LEP) of MD membranes. In the second part, we provide experimentally measured data on LEP values of some commercially available hollow-fiber and flat-sheet membranes tested in our lab using different MD configurations. The LEP[subscript w] value of the MD 020 CP 2N hollow-fiber membrane (Microdyn-Nadir GmbH, Wiesbaden, Germany) made of PP is found to be 0.97 bar using direct-contact membrane distillation (DCMD) configuration. The LEP[subscript w] value of the DuraporeTM GVPH flat sheet membrane (Merck Millipore Inc., Billerica, USA) made of PVDF is found to be 2.37±0.025 bar using static measurement technique and 1.90 bar using vacuum MD configuration. We also show that wetted membranes can be successfully regenerated by soaking them in ethanol and removing ethanol with evaporation at elevated temperatures. A novel concept of regeneration procedures applying vacuum have developed and have been proved to be effective for the tested flat sheet modules, however, failed on recovering the hydrophobic characteristics of the PP membrane in the hollow-fiber module

Concentration of 'Oblachinska' sour cherry juice using osmotic distillation

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Effects of pH, lactate, hematocrit and potassium level on the accuracy of continuous glucose monitoring (CGM) in pediatric intensive care unit

BACKGROUND: Continuous glucose monitoring (CGM) originally was developed for diabetic patients and it may be a useful tool for monitoring glucose changes in pediatric intensive care unit (PICU). Its use is, however, limited by the lack of sufficient data on its reliability at insufficient peripheral perfusion. We aimed to correlate the accuracy of CGM with laboratory markers relevant to disturbed tissue perfusion. PATIENTS AND METHODS: In 38 pediatric patients (age range, 0–18 years) requiring intensive care we tested the effect of pH, lactate, hematocrit and serum potassium on the difference between CGM and meter glucose measurements. Guardian® (Medtronic®) CGM results were compared to GEM 3000 (Instrumentation laboratory®) and point-of-care measurements. The clinical accuracy of CGM was evaluated by Clarke Error Grid -, Bland-Altman analysis and Pearson’s correlation. We used Friedman test for statistical analysis (statistical significance was established as a p < 0.05). RESULTS: CGM values exhibited a considerable variability without any correlation with the examined laboratory parameters. Clarke, Bland-Altman analysis and Pearson’s correlation coefficient demonstrated a good clinical accuracy of CGM (zone A and B = 96%; the mean difference between reference and CGM glucose was 1,3 mg/dL, 48 from the 780 calibration pairs overrunning the 2 standard deviation; Pearson’s correlation coefficient: 0.83). CONCLUSIONS: The accuracy of CGM measurements is independent of laboratory parameters relevant to tissue hypoperfusion. CGM may prove a reliable tool for continuous monitoring of glucose changes in PICUs, not much influenced by tissue perfusion, but still not appropriate for being the base for clinical decisions

Az ICON elektromos kardiometrián alapuló nem invazív hemodinamikai monitor használata a klinikumban

Absztrakt: A kritikus állapotú betegek kezelésében elengedhetetlen fontosságú a hemodinamikai monitorozás. Az utóbbi években az intenzív osztályos ellátás a technika fejlődésének köszönhetően ezen a területen is egyre inkább a nem invazív irányt követi. A néhány évtizeddel ezelőtt rutinszerűen bevezetett invazív hemodinamikai monitorozás használata a gyermek intenzív, valamint egyre több helyen a felnőtt intenzív ellátásban is csökkenő tendenciát mutat. A nem invazív monitorozás elterjedésének oka a biztonságossága, szövődménymentessége mellett a költséghatékonysága is. Összefoglalónk témája az elektromos kardiometrián (electric cardiometry) alapuló ICON® betegmonitor ismertetése, amely egy újonnan kifejlesztett nem invazív, hemodinamikai paramétereket mérő és regisztráló eszköz. Klinikai alkalmazhatósága kiterjed a csecsemő-, gyermek- és felnőttosztályos gyakorlatra is. Az ICON® elektromos kardiometriai monitor működési elve egyszerű: az aortában a vér vezetőképessége az idő függvényében változást mutat, az aortabillentyű nyitása előtt a vörösvérsejtek random elhelyezkedést mutatnak, míg kamrai kontrakció hatására párhuzamos irányultságot vesznek fel. Négy elektróda felhelyezését követően az eszköz a két állapot közti vezetőképesség-változást rögzíti, majd a kapott értékekből a perctérfogatot és a verőtérfogatot méri, valamint más cardiovascularis paramétereket (például szisztémás vascularis rezisztencia) számol a mellkasi elektromos bioimpedancia szívciklushoz kapcsolódó változásainak követésével. Az ICON® legfontosabb előnyei az azonnali és folyamatos mérési lehetőség, illetve a nem invazivitásból fakadó alacsony szövődményráta. Az ICON® új, ígéretes hemodinamikai eszköz az intenzív terápia területén. A nem invazív, valós idejű mérési módszerrel szinte azonnal felmérhető a betegek hemodinamikai statusa, így az optimális terápia indítása késlekedés nélkül elkezdhető. A pontosabb klinikai indikációk meghatározásához további kutatások folyamatban vannak. Orv Hetil. 2018; 159(44): 1775–1781. | Abstract: Establishment of a proper hemodynamic monitoring system in order to achieve optimal care among critically ill patients is fundamental. In contrast to invasive patient-checking systems, which were introduced decades ago and used in both adult and pediatric intensive care, the non-invasive methods have become more popular in recent years due to technical advancements in intensive care and patient monitoring. This increase in popularity can be attributed to the higher degree of safety and reduced complication rates as well as to its being more economical. Our summary focuses on the ICON® patient monitoring system. This newly engineered, non-invasive tool is based on electrical cardiometry, and uses hemodynamic parameters in both neonatal and pediatric care as well as in adults. The operating principle is simple: the conductivity of the blood in the aorta shows time-dependent changes. Prior to the opening of the aortic valve, the orientation of the red blood cells (RBCs) is random, and it is not until the contraction of the aorta that the RBCs and the opening of the aortic valve achieve a parallel position. The tool senses the conductivity between four placed electrodes, and measures the stroke volume (SV) and cardiac output (CO), before calculating other additional parameters (eg.: systemic vascular resistance) by tracing the variation of bioimpedance according to changes in the heart cycle. The most important advantages of ICON® are the measurements that are made available immediately as well as continuously, and the low complication rate that originates from its non-invasive operation. ICON® is a new, promising hemodynamic device in the tool belt of intensive care. Due to the nature of the device, it is possible to evaluate the status of the patient on a continuous basis, allowing for optimal care. To identify the more accurate clinical indications further measures will be necessary. Orv Hetil. 2018; 159(44): 1775–1781