Air Bleeding Research Articles

<b>Dry ripened mortar with quarry waste and rubber powder from unserviceable tires

Stone-quarry fines have been evaluated in mortar and concrete, but have presented drying shrinkage and consequently higher incidence of cracks than those with natural sand. This study compared the dry ripened mortar in two types of aggregates added of 8% rubber powder. It was used quicklime, artificial and natural sand in volumetric proportions of 1:6. Mixtures were oven-dried, received the cement, establishing the volumetric proportion of 1: 1.5:9. Inplastic state, we evaluated aspects such as consistence, air content, water retention and bleeding; whereas compressive strength, static deformation modulus and water absorption by capillarity was determined in hardened state. Cracking aspects were evaluated in substrate. As a result, the mortar with artificial sand showed higher increases in compressive strength, capillarity rate and cracking, and greater reductions in air content and bleeding. As for the rubber powder, exhibited a greater reduction in the cracking rate and capillarity was found.

Peculiarities of modeling the work process in a low-pressure compressor of a gas turbine plant

The problem of weight decrease is crucial for modern gas turbine engines. Application of supersonicand transonic compressors is one of the ways of solving this problem. This allows reaching a higher pressureratio at each stage than while using subsonic compressors and thus reducing the number of stages required toproduce the desired value of pressure ratio. In compressors of this kind the flow is slowed down due to a systemof shockwaves in the supersonic part and due to the flow deflection in the diffuser channels formed by the rotorblades and guide vanes in the subsonic part. The design of new compressors and modernization of old ones isinextricably connected with the usage of computational fluid dynamics methods at the present stage of engineconstruction development. The necessity of simulating a shockwave system imposes high demands on the constructionof a computational mesh. In particular, the choice of the method of parameter passing between the domainsof rotating blades and those of fixed guide vanes is an urgent task. It is shown in the paper that the use ofdifferent methods of averaging and parameter passing between domains can make a significant difference incompressor design characteristics (for example, a three-stage low-pressure compressor). Three methods of passingparameters between the domains that are used in the software package NUMECA/Fine Turbo are analyzed.The calculated compressor characteristics are compared with the experimental data at different rotation frequenciesof the rotor. The data obtained show the adequacy of the numerical model of the work process in the compressorunder investigation. Typically, air bleeding for various needs takes place in compressors. Compressorperformance changes when the air enters it, which should be considered in the calculations. It is shown in theexample of the compressor tested that the inclusion of air bleeding results in quantitative and qualitative changesin the compressor performance. Among other things, parameters like pressure ratio and dynamic stability marginare changed, which may lead to inconsistent operation of the compressor as part of the engine. Thus, a conclusionabout the necessity of taking into account the simulation of air bleeding in the calculation of supersoniccompressors is made. The results obtained make it possible to expand the understanding of the working processof supersonic and transonic compressors and can be used later in the creation of numerical computational modelsof compressors of this type.

Mach Number Effect on The Heat Transfer Mechanism of Aircraft Anti-Icing Systems

The primary means of preventing ice formation on wings and engine inlets for modern commercial transport aircraft is by extracting hot air from the compressor and blowing it on the inside surface of the leading edge through small holes drilled in the so-called piccolo tube system. A critical aspect in the design of such system is the prediction of heat transfer impinging jets from the piccolo tube. The correct evaluation of the heat transfer rate in such devices is of great interest to optimize both the anti-icing performance and the hot air bleeding from the high-pressure compressor. A review of the literature reveals that there are some experimental and numerical studies that developed correlations for the average Nusselt number. However, most of the research was performed using a single jet or a group of jets impinging on a flat slat, which is different from the jet impingement on concave surfaces, as the inside surface of a wing. Therefore, the objective of the present work is to perform a parametric study of the impingement jet flow on concave surfaces employing CFD tool. The main goal is determine the effect of the Mach number on this heat transfer process

Evaluation of a robot-assisted video-assisted thoracoscopic surgery programme

At present, there is increasing interest in surgical procedures using a robot-assisted device. The aim of this study was to investigate whether robot-assisted video-assisted thoracoscopic surgery (VATS) was more effective than conventional VATS. A total of 64 VATS lobectomies in Papworth Hospital (Cambridge, UK) were included in the study. In 34 cases the lobectomies were performed using conventional VATS (CV group), while in the remaining 30 cases the lobectomies were performed using robot-assisted VATS (Robotic group). In the robot-assisted VATS, FreeHand®, a thoracoscopic camera controller produced by Freehand 2010 Ltd. (Eastleigh, UK), was used. The duration of the thoracoscopic surgery in the Robotic group was 145.50±10.43 min, whereas in the CV group the duration was 162.79±9.40 min. The surgery duration in the Robotic group was 10.62% shorter than that in the CV group (P<0.05). The rates of bleeding, pulmonary infection, arrhythmia and prolonged air leak (≥5 days) in the Robotic group were 0, 3.33, 26.67 and 13.33%, respectively, while the corresponding rates in the CV group were 2.94, 5.88, 20.59 and 17.65%, respectively. No significant differences were identified in the postoperative complication rates between the two groups (P≥0.05). There was no perioperative mortality in the study. Compared with conventional VATS, FreeHand-assisted VATS provides a similar rate of postoperative complications and a reduced surgery duration, and may be beneficial for the recovery of the patients following VATS.

Testicular Biopsy in Psittacine Birds (Psittaciformes): Impact of Endoscopy and Biopsy on Health, Testicular Morphology, and Sperm Parameters

Histologic examination of a testicular biopsy sample may be required to evaluate the reproductive status of male psittacine birds. The purpose of this study was to evaluate the viability of testicular sampling from live birds by assessing the impact on the birds' health, testicular integrity, and sperm quality. Testicular biopsy samples were obtained by endoscopy 4 times during 12 months from 9 cockatiels (Nymphicus hollandicus) and 7 rose-ringed parakeets (Psittacula krameri). Only 2 of 16 birds showed testicular cicatrization or divided testicular tissue after a single endoscopy. Further complications, such as damage to the air sacs or bleeding, predominantly occurred in subsequent endoscopies. In both species, endoscopy and testicular biopsy caused only minor or transient effects on sperm production and sperm quality. These results support that a single testicular biopsy is a viable method for evaluating the reproductive status of male psittacine birds.

EComment. Pulmonary segmentectomies: should we follow segmental veins or deflation/inflation lines?

We read with interest the well-written study of Tane et al. about the usefulness of 320-multidetector row for preoperative three-dimensional (3D) pulmonary vasculature assessment for candidates for pulmonary segmentectomies [1]. Puzzlingly, quite similar studies have been simultaneously published by other Japanese groups [2, 3]. We would like to add some considerations. Importantly, this paper highlights the preoperative utility of identifying the intersegmental vein to decide whether the segmentectomy is feasible or not. However, it would be interesting to understand if the 3D software is now able to clearly depict and differentiate pulmonary veins from arteries (e.g. by colour-coding these vessels differently), thus facilitating the assessment of tumoural vein invasion. Furthermore, it is unclear if the software can truly facilitate the identification of the intersegmental pulmonary vein as compared to axial computed tomography images. A second comment concerns the surgical technique: if a primary tumour is less than 2 cm in diameter, is it really important to assess pulmonary vasculature precisely? In fact, we think that it could be safe and sufficient (and probably easier) to identify the lines of inflation and deflation to divide lung parenchyma while performing a pulmonary segmentectomy. According to Schuchert and colleagues this approach could decrease the risk of bleeding and prolonged postoperative air leaks [4]. Maybe a well designed randomized controlled trial would be able to clarify these open issues. Conflict of interest: none declared.

Method of calculating GTE gas-thermodynamic parameters with blade row description of an axial multistage compressor

A method of calculating the operating performance of a turboshaft gas turbine engine for steady- state conditions has been developed based on a mathematical model with a row- after- row presentation of a multistage axial compressor. This method as opposed to the existing ones makes it possible to determine gas turbine engine gas-thermodynamic parameters at different ratings taking into account such factors as air bleeding and blow off directly from the air-gas channel, the variation of geometrical parameters of compressor blade rows and meridian bypasses and changes in the programme of regulating variable stator vanes. The results of investigating the thermodynamic parameters of the main units, their elements and performance characteristics of a turboshaft gas turbine engine are presented for a wide range of rotor speeds (throttle performance). Comparisons between the computational results and the experimental data are made, their agreement is shown to be satisfactory.

Numerical analysis of a swept wing hot air ice protection system

A tight-coupling heat transfer method is proposed in this paper for the analysis of the performance of the hot air ice protection system. The Eulerian method is used for the calculation of the local collection efficiency. The external heat transfer coefficient was computed using the boundary layer integrated method. The thermal conductivity within the wing skin and the internal heat transfer between the hot air flow and the skin were computed using the computational fluid dynamic method. At the same time, the external heat flux boundary condition and the surface temperature were updated automatically by user-defined function to drive the iteration of the tight-coupling heat transfer calculation. The surface temperature results in dry air condition are compared with flight test data and show agreement. The maximum temperature difference between the simulation and the test is 11.5 K. In addition, the method proposed in this paper is applied to the wing hot air ice protection system of a real aircraft in icing conditions. It is found that the surface temperature ranges from 3 to 30 ℃ under certain flight and icing conditions. Larger droplet diameter or larger liquid water content leads to more runback water which changes the surface temperature not much when the parameters of the bleeding air are the same.

Vascular Access for Intensive Maintenance Hemodialysis: A Systematic Review for a Canadian Society of Nephrology Clinical Practice Guideline

Practices in vascular access management with intensive hemodialysis may differ from those used in conventional hemodialysis. We conducted a systematic review to inform clinical practice guidelines for the provision of intensive hemodialysis. Adult patients receiving maintenance (>3 months) intensive hemodialysis (frequent [≥5 hemodialysis treatments per week] and/or long [>5.5 hours per hemodialysis treatment]). We searched EMBASE and MEDLINE (1990-2011) for randomized and observational studies. We also searched conference proceedings (2007-2011). (1) Central venous catheter (CVC) versus arteriovenous (AV) access, (2) buttonhole versus rope-ladder cannulation, (3) topical antimicrobial cream versus none in buttonhole cannulation, and (4) closed connector devices among CVC users. Access-related infection, survival, hospitalization, patency, access survival, intervention rates, and quality of life. We included 23, 7, and 5 reports describing effectiveness by access type, buttonhole cannulation, and closed connector device, respectively. No study directly compared CVC with AV access. On average, bacteremia and local infection rates were higher with CVC compared with AV access. Access intervention rates were higher with more frequent hemodialysis, but access survival did not differ. Buttonhole cannulation was associated with bacteremia rates similar to those seen with CVCs in some series. Topical mupirocin seemed to attenuate this effect. No direct comparisons of closed connector devices versus standard luer-locking devices were found. Low rates of actual or averted (near misses) air embolism and bleeding were reported with closed connector devices. Overall, evidence quality was very low. Limited direct comparisons addressing main review questions, small sample sizes, selective outcome reporting, publication bias, and residual confounding were major factors. This review highlights several differences in the management of vascular access in conventional and intensive hemodialysis populations. We identify a need for standardization of vascular access outcome reporting and a number of priorities for future research.

일차계 모델을 이용한 고분자전해질 연료전지 스택의 CO Poisoning 및 Air Bleeding 효과 분석

상업용 막전극접합체를 사용하여 제작한 고분자전해질 연료전지의 CO poisoning 및 air bleeding 효과가 스택의 셀전압 성능에 미치는 영향을 분석하였다. 실험을 통해 확보한 동적 응답 데이터에 일차 미분방정식으로 표현되는 일차계 모델을 적용하여 정상상태 이득과 시간상수를 계산하는 방법으로 스택 셀전압의 응답 특성을 정량화하였다. 연료전지 개질기로부터 공급되는 개질 가스에 포함된 CO 농도가 1 ppm 증가할 때마다 셀전압은 1.3~1.6 mV 저하되고, CO 농도의 변화폭이 클수록 정상상태에 도달하기까지 걸리는 시간이 점점 짧아지는 것으로 분석되었다. CO poisoning에 의해 저하된 스택 성능을 회복시키기 위해 air bleeding을 수행할 경우, 주입하는 공기의 농도를 증가시킬수록 셀전압 상승폭(정상상태 이득)이 커지고 회복시간(시간상수)은 짧아지나, 1% 수준의 air bleeding만으로도 CO poisoning이 일어나기 전 셀전압의 87%~96%를 1~30 min 이내에 회복시킬 수 있는 것으로 분석되었다. We analyze the effects of CO poisoning and air bleeding on the performance of a PEM (polymer electrolyte membrane) fuel cell stack fabricated using commercial MEA (membrane electrode assembly). Dynamic response data from the experiments on the performance of a stack are identified by obtaining steady-state gains and time-constants of the first-order system model expressed as a first-order differential equation. It is found that the cell voltage of the stack decreases by 1.3-1.6 mV as the CO concentration rises by 1 ppm. The time elapsed to reach a new steady state after a change in the CO concentration is shortened as the magnitude of the change in the CO concentration increases. In general, the steady-state gain becomes bigger and the time-constant gets smaller with increasing the air concentration (air-bleeding level) in the reformate gas to restore the cell voltage. However, it is possible to recover 87%-96% of the original cell voltages, which are measured with free of CO, within 1-30 min by introducing the bleed air as much as 1% of the reformate gas into the stack.

Comprehensive study of an air bleeding technique on the performance of a proton-exchange membrane fuel cell subjected to CO poisoning

CO poisoning is a major issue for proton-exchange membrane fuel cells (PEMFCs) when reformate gas is used as a fuel, especially at low temperatures (<80 °C). The performance of a PEMFC is investigated when subject to CO poisoning under different operation conditions and a simplified model is hereby proposed. It is found that even when the a CO-tolerant material like platinum–ruthenium (Pt–Ru) is used as the anode catalyst, the cell loses approximately 40% of its current density within 40 min with hydrogen fuel containing 25 ppm CO. By applying 5% air bleeding, the cell output current can be restored to 90% within 10 min, even at high CO concentrations (200 ppm). However, excessive air bleeding (>10% air) also reduces the cell output power. Based on impedance measurements, CO poisoning can strongly increase the charge transfer resistance without affecting the cell internal resistance. The stability test for 300 h using 200 ppm CO and 5% air bleeding shows that the cell power output can remain stable with the overall degradation less than 2%. From the viewpoints of system design and operation, air bleeding offers a stable power output and allows for a simpler, smaller, and cheaper reformer.

Minimally invasive vacuum-assisted closure therapy in the management of complex pleural empyema

The pool of potential candidates for pleural empyema is expanding. In a previous technical report, we tested the feasibility of the minimally invasive insertion of a vacuum-assisted closure (Mini-VAC) system without the insertion of an open-window thoracostomy (OWT). In this study, we describe a consecutive case series of complex pleural empyemas that were managed by this Mini-VAC therapy. In this retrospective study, we investigated 6 patients with multimorbidity (Karnofsky index ≤ 50%) who were consecutively treated with Mini-VAC for a primary, postoperative or recurrent pleural empyema between January 2011 and February 2012. Local control of the infection and control of sepsis were satisfactory in all 6 of the patients treated by Mini-VAC therapy. The suction used did not create any air leaks or bleeding from the lung or mediastinal structures. Mini-VAC therapy allowed a reduction of the empyema cavity and improved the re-expansion of the residual lung. Mini-VAC therapy resulted in a rapid eradication of the empyema. The chest wall was closed in all patients during the first hospital stay. All patients left the hospital in good health (Karnofsky index >70%) and with a non-infected pleural cavity at a mean of 22 ± 11 days after Mini-VAC installation. Pleural empyema was not detected in any of the 6 patients at the 3-month follow-up appointment. The Mini-VAC procedure with the abdication of an OWT offers a rapid treatment for complex pleural empyema with minimal surgical effort and the opportunity for a primary closure of the empyema cavity.

The effect of firing biogas on the performance and operating characteristics of simple and recuperative cycle gas turbine combined heat and power systems

We investigated the influence of firing biogas on the performance and operating characteristics of gas turbines. Combined heat and power systems based on two different gas turbines (simple and recuperative cycle engines) in a similar power class were simulated. A full off-design analysis was performed to predict the variations in operations due to firing biogas instead of natural gas. A wide range of biogas compositions differing in CH4 content was simulated. Without consideration of operating restrictions on the compressor and turbine, using biogas was predicted to augment the power output in both engines. Power output increased as CH4 content decreased. The main reason is the increase in turbine power due to increased fuel flow. Gas turbine efficiency increased with decreasing CH4 content in the simple cycle engine, but decreased in the recuperative cycle engine. Net efficiency including the fuel compression power consumption decreased with decreasing CH4 content even in the simple cycle engine. The heat recovery also increased by firing biogas. However, the increased turbine flow was accompanied by a surge margin reduction of the compressor and overheating of the turbine blade. These two problems were more severe in simple cycle gas turbines and as the ambient temperature increased. The turbine blade temperature and the compressor surge margin could be recovered to the reference values by either under-firing or compressor air bleeding, which are effective for blade temperature control and surge margin control, respectively. However, satisfaction of both restrictions by a single modulation caused excessive power and efficiency losses. An optimal combination between under-firing and air bleeding would minimize the performance penalty.

High frequency oscillatory ventilation as the most appropriate treatment for life threatening thoracic trauma

Acute respiratory failure is common in trauma patients and can be a threat to life in severe thoracic injury. We represent a case of severe respiratory failure after blunt thoracic injury with uncontrollable bleeding and massive air leak which was successfully managed with high frequency oscillatory ventilation. In our opinion high frequency oscillatory ventilation represent a safe and effective treatment of life threatening acute respiratory failure in trauma patients.

Complex pleural empyema can be safely treated with vacuum-assisted closure

ObjectiveFor patients with postoperative pleural empyema, open window thoracostomy (OWT) is often necessary to prevent sepsis. Vacuum-assisted closure (VAC) is a well-known therapeutic option in wound treatment. The efficacy and safety of intrathoracal VAC therapy, especially in patients with pleural empyema with bronchial stump insufficiency or remain lung, has not yet been investigated.MethodsBetween October 2009 and July 2010, eight consecutive patients (mean age of 66.1 years) with multimorbidity received an OWT with VAC for the treatment of postoperative or recurrent pleural empyema. Two of them had a bronchial stump insufficiency (BPF).ResultsVAC therapy ensured local control of the empyema and control of sepsis. The continuous suction up to 125 mm Hg cleaned the wound and thoracic cavity and supported the rapid healing. Additionally, installation of a stable vacuum was possible in the two patients with BPF. The smaller bronchus stump fistula closed spontaneously due to the VAC therapy, but the larger remained open.The direct contact of the VAC sponge did not create any air leak or bleeding from the lung or the mediastinal structures. The VAC therapy allowed a better re-expansion of remaining lung.One patient died in the late postoperative period (day 47 p.o.) of multiorgan failure. In three cases, VAC therapy was continued in an outpatient service, and in four patients, the OWT was treated with conventional wound care. After a mean time of three months, the chest wall was closed in five of seven cases. However, two patients rejected the closure of the OWT. After a follow-up at 7.7 months, neither recurrent pleural empyema nor BPF was observed.ConclusionVAC therapy was effective and safe in the treatment of complicated pleural empyema. The presence of smaller bronchial stump fistula and of residual lung tissue are not a contraindication for VAC therapy.

A novel cardioport for beating-heart, image-guided intracardiac surgery

Intracardiac beating-heart procedures require the introduction and exchange of complex instruments and devices. To prevent potential complications such as air embolism and bleeding, a universal cardioport was designed and tested. The design consists of a port body and a series of interchangeable sleeves. The port uses a fluid purging system to remove air from the instrument before insertion into the heart, and a valve system minimizes blood loss during instrument changes. The cardioport was tested exvivo and invivo in pigs (n=5). Beating-heart procedures, such as septal defect closure and mitral valve repair, were modeled. Exvivo trials (n=150) were performed, and no air emboli were introduced using the port. In comparison, air emboli were detected in 40% to 85% of the cases without the use of the port-based purging system. Port operation revealed excellent ergonomics and minimal blood loss. A novel cardioport system designed to prevent air entry and blood loss from transcardiac instrument introduction was shown to be an enabling platform for intracardiac beating-heart surgery. The port system improves safety and facilitates further development of complex instruments and devices for transcardiac beating-heart surgery.

Invited Commentary

Invited Commentary

Feasibility and safety of postoperative management without chest tube placement after thoracoscopic wedge resection of the lung

The aim of the present study was to assess the feasibility and safety of several improved criteria to avoid chest tube placement after thoracoscopic wedge resection of the lung. From 2000 to 2009, 333 patients who underwent thoracoscopic wedge resections of the lung were reviewed. The patients were classified into two groups: (1) the no chest tube group (NCT), consisting of 132 patients in whom chest tubes were not placed because no air leakage or bleeding during intraoperative alternative sealing test was confirmed, and (2) the chest tube placement (CTP) group, consisting of 201 patients in whom chest tubes were placed because the criteria for the nonplacement of a chest tube were not met. The clinical data and postoperative morbidity were assessed between the two groups. The number of specimens (1.3 vs 1.5) and the endostapler cartridges used (2.5 vs 3.3), and the duration of the postoperative hospital stay (4.6 vs 6.7 days) in the NCT group were significantly lower than in the CTP group. One patient from the NCT group required chest tube insertion due to the development of late pneumothorax. However, no significant differences were found between the two groups. Our improved criteria are therefore considered to positively contribute to a safe and definite clinical decision regarding postoperative patient management.

Effect of Ankaferd Blood Stopper on air leakage in the lung and prevention of bleeding: an experimental study

BackgroundAir leakage and hemorrhage are important causes of morbidity and mortality in operations and traumas of the lung. Ankaferd Blood Stopper is a herbal product used for stopping hemorrhage. In our study, we investigated the efficacy of Ankaferd Blood Stopper in the prevention of air leakage in the lung and bleeding.MethodsA total of twenty-one Wistar-Albino rats weighing 240 ± 20 grams were used in our study. An equal amount of injury was created in all groups by performing left thoracotomies. No interventions were made on tissue injury in the first group, and suturing was performed in the second group, and Ankaferd was applied in the third group. Air leakage and duration of bleeding were recorded in all groups.ResultsA statistically significant difference was found between the three groups in terms of air leakage time (p = 0,0001) and bleeding time (p = 0,0001). While a significant effect of Ankaferd was detected in terms of air leakage compared to standard surgery (p = 0,017), no difference was found in terms of bleeding time.ConclusionsAnkaferd Blood Stopper ceases the air leakage in the lung parenchyma significantly and effectively. No significant difference is seen compared to the standard surgery group, although it ceases bleeding significantly.

Human Fibrinogen/Thrombin-Coated Collagen Patch to Control Intraoperative Severe Pulmonary Hemorrhage and Air Leakage After Correction of a Ruptured Thoracic Aortic Aneurysm

Lung erosion represents a dreadful complication in patients affected by thoracic aortic aneurysms. Intraoperative occurrence of severe bleeding and extensive air leakage from the pulmonary erosion is usually quite particularly dangerous and challenging because of fragile lung tissue to be repaired, hypo-coagulative state, and the need for full mechanical ventilation. We report the case of a patient who had uncontrollable pulmonary bleeding and marked air leakage from an aortic aneurysm-induced lung erosion and laceration, which were effectively treated with a hemostatic patch (Tachosil, Nycomed, Linz, Austria) after unsuccessful conventional surgical approaches.