Heat transfer from the stagnation area of a heated cylinder at Re(D) = 140,000 affected by free-stream turbulence

This is the post-print version of the final paper published in International Journal of Heat and Mass Transfer. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.The effect of free-stream grid-turbulence on the flow around and heat transfer from the stagnation region of a circular cylinder was studied using direct numerical simulations (DNS). Simulations with and without free-stream fluctuations were carried out at a Reynolds number of Re(D) = 140,000 (based on the inflow velocity and the cylinder diameter D), which is in the higher subcritical range. A splitter plate was introduced behind the cylinder to counteract the formation of a vortex street. To resolve the flow up to 746.5 million grid points were employed. Compared to the fully laminar simulation, the addition of Tu = 30% grid turbulence at the inflow plane was found to lead to an increase in heat transfer at the stagnation line of the cylinder of 66%. A very good agreement was obtained with the correlations of Dullenkopf and Mayle [K. Dullenkopf, R. Mayle, The effects of incident turbulence and moving wakes on laminar heat transfer in gas turbines, ASME J. Turbomach. 116 (1994) 23–28; K. Dullenkopf, R. Mayle, An account of free-stream-turbulence length scale on laminar heat transfer, ASME J. Turbomach. 117 (1995) 401–406].The German Research Foundatio

Fluid leakage past tracheal tube cuffs: evaluation of the new Microcuff endotracheal tube

Objective: This study compared the recently introduced Microcuff endotracheal tube HVLP ICU featuring an ultrathin (7-µm) polyurethane cuff membrane with endotracheal tubes from different manufacturers regarding fluid leakage past the tube cuff. Design: In vitro setup. Measurements and results: The following endotracheal tubes (ID 7.5mm) were compared: Mallinckrodt HiLo, Microcuff HVLP ICU, Portex Profile Soft Seal, Rüsch Super Safety Clear, and Sheridan CF. A vertical PVC trachea model (ID 20mm) was intubated, and cuffs were inflated to 10, 15, 20, 25, 30, and 60cmH2O. Colored water (5ml) was added to the top of the cuff. The amount of leaked fluid past the tube cuff within 5, 10, and 60min was recorded. Experiments were performed four times using two examples of each tube brand. Fluid leakage past tube cuffs occurred in all conventional endotracheal tubes at cuff pressures from 10 to 60cmH2O. In the Microcuff tube cuff pressure fluid leakage was observed within 10min only at 10cmH2O. Results with the Microcuff tube were significantly better than all other tube brands at cuff pressures of 10-30cmH2O. Conclusions: Within the acceptable upper limit for tracheal cuff pressure (25-30cmH2O) the Microcuff endotracheal tube was the only one of the tested tubes to prevent fluid leakage in our in vitro setup. In vivo studies are required to confirm these finding

Appropriate placement of intubation depth marks in a new cuffed paediatric tracheal tube

Background. The aim of this study was to evaluate the appropriateness of intubation depth marks on the new Microcuff paediatric tracheal tube. Methods. With local Institutional Ethics Committee approval and informed parental consent, we included patients from birth (weighing ≥3 kg) to 16 yr who were undergoing general anaesthesia requiring orotracheal intubation. Tracheal intubation was performed using direct laryngoscopy, the intubation depth mark was placed between the vocal cords, and the tube was taped to the lateral corner of the mouth. The distance between the tube tip and the tracheal carina was assessed by flexible bronchoscopy with the patients in supine, and their head in neutral positions. Tube sizes were selected according to the formula: internal diameter (ID; mm)=(age/4)+3.5 in children ≥2 yr. In full-term newborns (≥3 kg) to less than 1 yr ID 3.0 mm tubes were used and in children from 1 to less than 2 yr ID 3.5 mm tubes were used. Endoscopic examination was performed in 50 size ID 3.0 mm tubes, and in 25 tubes of each tube size from ID 3.5 to 7.0 mm. Tracheal length and percentage of the trachea to which the tube tip was advanced were calculated. Results. 250 patients were studied (105 girls, 145 boys). The distance from the tube tip to the carina ranged from 1.4 cm in a 2-month-old infant (ID 3.0 mm) to 7.7 cm in a 14-yr-old boy (ID 7.0 mm). Mean tube insertion into the trachea was 53.2% (6.3) of tracheal length with a minimum of 40% and a maximum of 67.6%. Conclusions. The insertion depth marks of the new Microcuff paediatric tracheal tube allow adequate placing of the tracheal tube with a cuff-free subglottic zone and without the risk for endobronchial intubation in children from birth to adolescenc

Shortcomings of cuffed paediatric tracheal tubes†

Background. The goal of this investigation was to evaluate adequacy of the design of readily available paediatric cuffed tracheal tubes (CPTT). Methods. In 15 series of cuffed (11) and uncuffed (four) paediatric tracheal tubes (ID: 2.5-7.0 mm) from four different manufacturers the following dimensions were measured: outer diameter of the tube, position and largest diameter of the tube cuff inflated at 20 cm H2O and position of depth markings and compared with age‐related dimensions. Results. Outer diameters for tubes with similar IDs varied markedly between manufacturers and between cuffed and uncuffed tracheal tubes from the same manufacturer. Cuff diameters at 20 cm H2O cuff pressure and cross‐sectional cuff area at 20 cm H2O cuff pressure did not always cover maximal internal age‐related tracheal diameters and cross‐sectional areas. Placing the tube tip in the mid‐trachea, the cuffs of cuffed tubes with ID 3.0, 4.0, or 5.0 mm would become positioned within the larynx. If the cuffs were placed 1 cm below the cricoid level, many of the tube tips would be dangerously deep within the trachea. Only five of the 11 cuffed tubes had a depth marking. In many of these tubes the distances from depth marking to tube tip were greater than the age‐related minimal tracheal length. Conclusion. Most cuffed paediatric tracheal tubes are poorly designed, in particular the smaller sizes. A better design of cuffed tubes with a short high‐volume, low‐pressure cuff, cuff‐free subglottic space and adequately placed depth markings are urgently needed. Br J Anaesth 2004; 92: 78-8

Accuracy of Continuous Central Venous Oxygen Saturation Monitoring in Patients Undergoing Cardiac Surgery

Objective: Continuous assessment of central venous oxygen saturation (ScevoxO2) with the CeVOX device (Pulsion Medical Systems, Munich, Germany) was evaluated against central venous oxygen saturation (ScvO2) determined by co-oximetry. Methods: In 20 cardiac surgical patients, a CeVOX fiberoptic probe was introduced into a standard central venous catheter placed in the right internal jugular vein and advanced 2-3cm beyond the catheter tip. After invivo calibration of the probe, ScevoxO2, ScvO2, mixed venous oxygen saturation (SmvO2) haemoglobin (Hb), body temperature, heart rate, central venous and mean arterial pressure, and cardiac index were assessed simultaneously at 30min intervals during surgery and at 60min intervals during recovery in the intensive care unit. Agreement between ScevoxO2, and ScvO2 was determined by Bland-Altman analysis. Simple regression analysis was used to assess the correlation of ScevoxO2, and ScvO2 to Hb, body temperature and haemodynamic parameters. Results: Values of ScevoxO2 and ScvO2 (84 data pairs during surgery and 106 in the intensive care unit) ranged between 45-89% and 43-90%, respectively. Mean bias and limits of agreement of ScevoxO2 and ScvO2 were -0.9 (−7.9/+6.1)% during surgery and −1.2 (−10.5/+8.1)% in the intensive care unit. In 37.9% of all measured data pairs, the difference between ScevoxO2 and ScvO2 was beyond clinically acceptable limits (≥1 s.d.). Mean bias was significantly influenced by cardiac index. Sensitivity and specificity of ScevoxO2 to detect substantial (≥1 s.d.) changes in ScvO2 were 89 and 82%, respectively. Conclusions: In adult patients during and after cardiac surgery, the current version of the CeVOX device might not be the tool to replace ScvO2 determined by co-oxymetry, although sensitivity and specificity of ScevoxO2 to predict substantial changes in ScvO2 were acceptabl

Dívida pública federal : análise da relação DLSP/PIB, da composição e da maturidade e os impactos na sustentabilidade no período 2003-2015

O objetivo da presente monografia visa a analisar a evolução da DLSP/PIB, da gestão do Tesouro nacional na mudança da composição da dívida pública e da consequente alteração na estrutura de vencimentos ocorridas de 2003 a 2015. O indicador Dívida Líquida do Setor Público DLSP/PIB diminuiu ou estabilizou no período do governo Lula (2003-2010) devido à preservação da política do tripé econômico, que tem como objetivos a meta de inflação, câmbio flutuante e o superávit primário, apresentado uma trajetória crescente nos últimos anos do governo Dilma (2010-2015) em função do que se denominou “nova matriz macroeconômica”. No que tange à composição da dívida pública, o Tesouro Nacional adotou a estratégia de desenvolver os mercados de título prefixado e de índice de preço em detrimento dos títulos indexados à taxa de juros e ao câmbio e esta alteração contribuiu para o aumento do prazo médio da dívida pública e para a diminuição do percentual vincendo em 12 meses. Com base na pesquisa realizada, os indicadores estudados foram benéficos para a sustentabilidade da dívida pública: queda da relação DLSP/PIB de 54,3% do PIB em 2003 para 36,2% em 2015, diminuição dos títulos indexados à taxa de juros e ao câmbio em detrimento dos títulos indexados à inflação e prefixados, aumento do prazo médio e diminuição do percentual vincendo em 12 meses da dívida pública.This monograph have the objetive of to analyze the evolution of DLSP/PIB of Brazilian National Treasury management in changing the composition of public debt and the consequent change occurred during 2003 to 2015. The DLSP/PIB indicator decreased or stabilized in the Lula government (2003-2010) due to the preservation of the economic tripod policy, which aims to inflation targeting, floating exchange rate and the primary surplus, and presented a growing trend in recent years of the Dilma government (2010-2015), depending on what is called "new macroeconomic matrix". Regarding the composition of public debt, the Brazilian National Treasury adopted a strategy to develop the fixed rate bond markets and price index at the expense of bonds indexed to interest rates and the exchange rate and this change contributed to the increase in medium-term public debt and the decrease in the percentage due in 12 months. Based on research conducted, the indicators studied were beneficial to the sustainability of public debt: fall DLSP/PIB ratio of 54.3% of PIB in 2003 to 36.2% in 2015, decrease in securities linked to interest rates and the exchange rate at the expense of inflation-linked bonds and fixed-rate, increased medium term and decrease the percentage due in 12 months of public debt

Intubation depth markings allow an improved positioning of endotracheal tubes in children

Objectives: To evaluate the position of the new Microcuff® pediatric tracheal tube, based upon intubation depth markings. Methods: With Institutional Ethics Committee approval and informed parental consent, we included patients from birth (≥ 3 kg) to 16 yr undergoing interventional cardiac catheterization requiring general anesthesia with oro-tracheal intubation. The intubation depth mark of the tracheal tube was placed between the vocal cords by direct laryngoscopy. The distance between tube tip and tracheal carina was measured from routinely taken cardiac catheterization posterior-anteriorx-ray computer images with the patient supine and the head in a neutral position. Evaluation was performed for 20 tubes size 3.0 mm internal diameter (ID) and for ten tubes of each size from 3.5 to 7.0 mm ID. Results: 100 patients were studied (47 girls; 53 boys). Tracheal tube tip advancement into the trachea ranged from 40.6% to 68.6% (median 51.4%). The shortest distance from tube tip to the tracheal carina was 15.7 mm using a 3.0 mm ID tube. Using a standard formula for tube insertion in children aged ≥ two years [12 cm + (age/2)], in one patient the tube tip would have been below the carina and in seven patients the tube cuffs would have been placed within the larynx. Conclusion: The intubation depth markings of the new Microcuff® pediatric tracheal tube allow safe placement of the tracheal tube with a cuff-free laryngeal zone without the risk for endobronchial intubation. Placement using the intubation depth markings was superior to predicted insertion using a standard formul

Clinical evaluation of cuff and tube tip position in a newly designed paediatric preformed oral cuffed tracheal tube

Background. To assess the adequacy of the position of the tracheal tube cuff and tracheal tube tip in the recently introduced preformed oral Microcuff paediatric endotracheal tube (PET) using the manufacturers recommendations for Microcuff tracheal tube size selection. Methods. With Hospital Ethics Committee approval and informed parental consent, the tracheas of children from birth to adolescence were orally intubated with the preformed oral Microcuff PET. First, the position of the tracheal tube's intubation depth mark in relation to the vocal cords was assessed. Second, the distance ‘tracheal tube tip-to-carina' was endoscopically measured with the patient supine and the head in a neutral position and the tube placed with the centre mark at the lower incisors or alveolar ridge. Results. A total of 166 children aged from 0.1 to 16.4 yr (median 5.9 yr) were studied. In five patients the intubation depth mark was above (5 mm each), in 22 patients at the level of and in the remaining 139 patients below the vocal cords. No endobronchial intubation occurred. In four patients the distance ‘tracheal tube tip-to-carina' was smaller than the safety margin to prevent endobronchial intubation during head-neck flexion. Conclusion. The new oral preformed cuffed tracheal tubes allow safe placement in almost all patients when inserted according to the tube bend. The critically low tube tip and the high cuff positions in a few tubes when placed according to the tube bend requires clinical alertnes

Tracheal tube-tip displacement in children during head-neck movement—a radiological assessment

Background. Aims of this study were to assess the maximum displacement of tracheal tube tip during head-neck movement in children, and to evaluate the appropriateness of the intubation depth marks on the Microcuff Paediatric Endotracheal Tube regarding the risk of inadvertent extubation and endobronchial intubation. Methods. We studied children, aged from birth to adolescence, undergoing cardiac catheterization. The patients' tracheas were orally intubated and the tracheal tubes positioned with the intubation depth mark at the level of the vocal cords. The tracheal tube tip-to-carina distances were fluoroscopically assessed with the patient supine and the head-neck in 30° flexion, 0° neutral position and 30° extension. Results. One hundred children aged between 0.02 and 16.4 yr (median 5.1 yr) were studied. Maximum tracheal tube-tip displacement after head-neck 30° extension and 30° flexion demonstrated a linear relationship to age [maximal upward tube movement (mm)=0 0.71×age (yr)+9.9 (R2=0.893); maximal downward tube movement (mm)=0.83×age (yr)+9.3 (R2=0.949)]. Maximal tracheal tube-tip downward displacement because of head-neck flexion was more pronounced than upward displacement because of head-neck extension. Conclusions. The intubation depth marks were appropriate to avoid inadvertent tracheal extubation and endobronchial intubation during head-neck movement in all patients. However, during head-neck extension the tracheal tube cuff may become positioned in the subglottic region and should be re-adjusted when the patient remains in this position for a longer tim