Effect of Impeller Design and Spacing on Gas Exchange in a Percutaneous Respiratory Assist Catheter

Providing partial respiratory assistance by removing carbon dioxide (CO₂) can improve clinical outcomes in patients suffering from acute exacerbations of chronic obstructive pulmonary disease and acute respiratory distress syndrome. An intravenous respiratory assist device with a small (25 Fr) insertion diameter eliminates the complexity and potential complications associated with external blood circuitry and can be inserted by nonspecialized surgeons. The impeller percutaneous respiratory assist catheter (IPRAC) is a highly efficient CO₂ removal device for percutaneous insertion to the vena cava via the right jugular or right femoral vein that utilizes an array of impellers rotating within a hollow‐fiber membrane bundle to enhance gas exchange. The objective of this study was to evaluate the effects of new impeller designs and impeller spacing on gas exchange in the IPRAC using computational fluid dynamics (CFD) and in vitro deionized water gas exchange testing. A CFD gas exchange and flow model was developed to guide a progressive impeller design process. Six impeller blade geometries were designed and tested in vitro in an IPRAC device with 2‐ or 10‐mm axial spacing and varying numbers of blades (2–5). The maximum CO₂ removal efficiency (exchange per unit surface area) achieved was 573 ± 8 mL/min/m² (40.1 mL/min absolute). The gas exchange rate was found to be largely independent of blade design and number of blades for the impellers tested but increased significantly (5–10%) with reduced axial spacing allowing for additional shaft impellers (23 vs. 14). CFD gas exchange predictions were within 2–13% of experimental values and accurately predicted the relative improvement with impellers at 2‐ versus 10‐mm axial spacing. The ability of CFD simulation to accurately forecast the effects of influential design parameters suggests it can be used to identify impeller traits that profoundly affect facilitated gas exchange.     

Establishing the Relationship between Cutting Speed and Output Parameters in Belt Grinding on Steels,Aluminum and Nickel Alloys: Development of Recommendations

This paper presents the research results of one of the main technological parameters of belt grinding, i.e., the cutting speed while machining corrosion- and heat-resistant, structural carbon and structural alloy steels, aluminum, and heat-resistant nickel alloys. Experimental and analytical methods are used to establish the dependence of the output parameters of surface belt grinding on the cutting speed and tool characteristics. An analytical model, considering the physical and mechanical properties of the grinding belt (strength depending on the base and bond; the thermal conductivity; the type of grinding operation) and the machined material, is created to determine the belt grinding speed. The output parameters, such as the arithmetic mean of the surface roughness (Ra) and the material removal rate (MRR) during the belt grinding of steels, heat-resistant and light alloys, have been studied. Based on the empirical dependencies of the belt grinding parameters, the model was developed for the selection and setting of the cutting speed of belt grinding for the aforementioned alloys, taking into account the type of operation, the type of the machined material, and the main characteristics of the sanding belt.     

Revealing the WEDM Process Parameters for the Machining of Pure and Heat-Treated Titanium (Ti-6Al-4V) Alloy

Ti-6Al-4V is an alloy that has a high strength-to-weight ratio. It is known as an alpha-beta titanium alloy with excellent corrosion resistance. This alloy has a wide range of applications, e.g., in the aerospace and biomedical industries. Examples of alpha stabilizers are aluminum, oxygen, nitrogen, and carbon, which are added to titanium. Examples of beta stabilizers are titanium–iron, titanium–chromium, and titanium–manganese. Despite the exceptional properties, the processing of this titanium alloy is challenging when using conventional methods as it is quite a hard and tough material. Nonconventional methods are required to create intricate and complex geometries, which are difficult with the traditional methods. The present study focused on machining Ti-6Al-4V using wire electrical discharge machining (WEDM) and conducting numerous experiments to establish the machining parameters. The optimal setting of the machining parameters was predicted using a multiresponse optimization technique. Experiments were planned using the response surface methodology (RSM) technique and analysis of variance (ANOVA) was used to determine the significance and contribution of the input parameters to changes in the output characteristics (cutting speed and surface roughness). The cutting speed obtained during the processing of the annealed titanium alloy using WEDM was quite large as compared to the cutting speed obtained in the case of processing the pure, quenched, and hardened titanium alloys using WEDM. The maximum cutting speed obtained while processing the annealed titanium alloy was 1.75 mm/min.     

Comparison of Physicochemical Properties of Fly Ash Precursor,Na-P1(C) Zeolite–Carbon Composite and Na-P1 Zeolite—Adsorption Affinity to Divalent Pb and Zn Cations

Considering the growing needs of environmental remediation, new effective solutions should be sought. Therefore, the adsorbed amounts of heavy metal ions, such as lead(II) and zinc(II), on the surface of high-carbon fly ash (HiC FA), zeolite-–carbon composite (Na-P1(C)) and pure zeolite (Na-P1), were investigated. The applied solids were characterized using the following techniques: XRD, SEM-EDS, TEM, porosimetry, SLS, electrophoresis and potentiometric titration. The heavy metal concentration in the probes was determined by applying ICP-OES spectroscopy. Adsorption/desorption and electrokinetic measurements were performed in the systems containing one or two adsorbates. The obtained results indicated that Pb(II) ions are adsorbed in larger amounts on the investigated solid surface due to the molecular sieving effect. The largest adsorption capacity relative to lead(II) ions was observed for pure Na-P1 zeolite (407 mg/g). The simultaneous presence of Pb(II) + Zn(II) mixed adsorbates minimally affects the amount of adsorbed Pb(II) ions and causes a significant decrease of Zn(II) ion adsorption (in comparison with analogous systems containing single adsorbates). It was also shown that all solids can be efficiently regenerated using hydrochloric acid. Thus, the selected pure zeolite can be successfully applied in soil remediation or other purifying technologies as an effective Pb(II) adsorbent.     

Preparation and Characterization of Nanoparticle-Doped Polymer Inclusion Membranes. Application to the Removal of Arsenate and Phosphate from Waters

Nanoparticle-doped polymer inclusion membranes (NP-PIMs) have been prepared and characterized as new materials for the removal of arsenate and phosphate from waters. PIMs are made of a polymer, cellulose triacetate (CTA), and an extractant, which interacts with the compound of interest. We have used the ionic liquid (IL) trioctylmethylammonium chloride (Aliquat 336) as the extractant and have investigated how the addition of nanoparticles can modify membrane properties. To this end, inorganic nanoparticles, such as ferrite (Fe₃O₄), SiO₂ and TiO₂, and multiwalled carbon nanotubes (MWCNTs), were blended with the polymer/extractant mixture. Scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and contact angle measurements have been used to characterize the material. Moreover, PIM stability was checked by measuring the mass loss during the experiments. Since Aliquat 336 acts as an anion exchanger, the NP-PIMs have been explored in two different applications: (i) as sorbent materials for the extraction of arsenate and phosphate anions; (ii) as an organic phase for the separation of arsenate and phosphate in a three-phase system. The presence of oleate-coated ferrite NP in the PIM formulation represents an improvement in the efficiency of NP-PIMs used as sorbents; nevertheless, a decrease in the transport efficiency for arsenate but not for phosphate was obtained. The ease with which the NP-PIMs are prepared suggests good potential for future applications in the treatment of polluted water. Future work will address three main aspects: firstly, the implementation of the Fe₃O₄-PIMs for the removal of As(V) in real water containing complex matrices; secondly, the study of phosphate recovery with other cell designs that allow large volumes of contaminated water to be treated; and thirdly, the investigation of the role of MWCNTs in PIM stability.     

不同麻醉下经皮椎间孔镜髓核摘除术治疗腰椎间盘突出症的疗效观察

目的探讨和分析不同麻醉下经皮椎间孔镜髓核摘除术在腰椎间盘突出症(LDH)患者中的临床应用价值。方法选取2016年1月-2017年12月该院所收治的110例LDH患者作为临床研究对象,采用随机数字表法将入选研究对象随机分为观察组56例和对照组54例,两组患者均行经皮椎间孔镜髓核摘除术治疗,研究组给予腰硬联合麻醉方案,对照组则给予气管插管全麻方案,并分别对两组患者的蒙特利尔认知评估量表(MoCA)、简易精神状态检查量表(MMSE)、视觉模拟评分(VAS)、Oswestry功能障碍指数问卷表(ODI)及临床治疗情况进行比较和分析。结果观察组术后MoCA评分(28.25±3.94)分和MMSE评分(29.72±4.08)分明显高于对照组,差异均有统计学意义(P 0.05);术后VAS评分(2.97±0.40)分和ODI指数(20.54±3.16)%明显低于对照组,差异均有统计学意义(P 0.05);术后临床治疗效果达到优的比率66.07%(37/56),以及总的优良率94.64%(53/56)明显高于对照组,差异有统计学意义(P 0.05)。结论腰硬联合麻醉下经皮椎间孔镜髓核摘除术对LDH患者认知功能的改善、疼痛症状的缓解和临床治疗效果的提升均有积极的现实意义。     

Barium peritonitis

A case of generalized peritonitis, secondary to a perforation of the rectosigmoid colon during barium-enema roentgenography, is presented. The patient required immediate surgical intervention with the prime importance of the treatment being removal of as much of the contaminating materials as possible. This was done successfully with irrigation and wiping, using urokinase solution. Peritoneal lavage with urokinase solution was also carried out in the early postoperative period. Fluid replacement with careful monitoring of fluid and electrolyte balance is essential before, during, and after the surgical procedure. Adequate antibiotic therapy and careful respiratory and nutritional support are also important.     

Reoperation following open reduction and plate fixation of displaced mid-shaft clavicle fractures

Background

Operative fixation of displaced, mid-shaft clavicle fractures has become an increasingly common practice. With this emerging trend, data describing patient outcomes with longer follow-up are necessary.

Patients and Methods

We retrospectively reviewed the medical records of subjects treated with plate fixation for displaced mid-shaft clavicle fractures from 2003 to 2009 at a Level I trauma hospital. All subjects were greater than 12 months post-index surgery. Treatment involved ORIF with either a low-contact dynamic compression plate (LCDC) or a contoured plate (pre-contoured or pelvic reconstruction plate). Our primary outcome was reoperation for any indication.

Results

143 subjects were included. The mean age was 36 ± 14 years and the mean time to reoperation or chart review was 33 months. Contoured plates were used in 64% of cases and LCDC plates were used in the remaining subjects. Twenty-nine subjects (20%) underwent reoperation: 23.5% of subjects treated with LCDC plates and 18.5% of subjects treated with contoured plates (p = 0.52). Indications for reoperation included implant irritation (n = 25), implant failure (n = 2), and non-union (n = 2). There was near statistically significant association with reoperation and female gender (p = 0.05) but no association between reoperation and age (p = 0.14), fracture class (p = 0.53), plate type (p = 0.49), or plate location (p = 0.93). The mean QuickDASH score for the population surveyed was 8.8 (5.5–12.1; 95% CI) with near statistically significant and clinically relevant difference between those considering reoperation and those not 22.3 (8.6–36.0; 95% CI) versus 6.7 (3.6–9.8; 95% CI).

Conclusions

This study represents a large series of displaced clavicle fractures treated with open reduction and plate fixation. Reoperation following plate fixation is relatively common, but primarily due to implant irritation. No difference in reoperation rates between plate types or location could be detected in our current sample size. Also, excellent functional outcomes continue to be observed several years after clavicle fracture fixation.