The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Kerem Pekkan - One of the best experts on this subject based on the ideXlab platform.
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hemodynamics of patient specific aorta Pulmonary Shunt configurations
Journal of Biomechanics, 2017Co-Authors: Senol Piskin, Firat H Altin, Okan Yildiz, Ihsan Bakir, Kerem PekkanAbstract:Optimal hemodynamics in aorta-Pulmonary Shunt reconstruction is essential for improved post-operative recovery of the newborn congenital heart disease patient. However, prior to in vivo execution, the prediction of post-operative hemodynamics is extremely challenging due to the interplay of multiple confounding physiological factors. It is hypothesized that the post-operative performance of the surgical Shunt can be predicted through computational blood flow simulations that consider patient size, Shunt configuration, cardiac output and the complex three-dimensional disease anatomy. Utilizing only the routine patient-specific pre-surgery clinical data sets, we demonstrated an intelligent decision-making process for a real patient having Pulmonary artery atresia and ventricular septal defect. For this patient, a total of 12 customized candidate Shunt configurations are contemplated and reconstructed virtually using a sketch-based computer-aided anatomical editing tool. Candidate Shunt configurations are evaluated based on the parameters that are computed from the flow simulations, which include 3D flow complexity, outlet flow splits, Shunt patency, coronary perfusion and energy loss. Our results showed that the modified Blalock-Taussig (mBT) Shunt has 12% higher right Pulmonary artery (RPA) and 40% lower left Pulmonary artery (LPA) flow compared to the central Shunt configuration. Also, the RPA flow regime is distinct from the LPA, creating an uneven flow split at the Pulmonary arteries. For all three Shunt sizes, right mBT innominate and central configurations cause higher Pulmonary artery (PA) flow and lower coronary artery pressure than right and left mBT subclavian configurations. While there is a trade-off between energy loss, flow split and coronary artery pressure, overall, the mBT Shunts provide sufficient PA perfusion with higher coronary artery pressures and could be preferred for similar patients having PA overflow risk. Central Shunts would be preferred otherwise particularly for cases with very low PA overflow risk.
Gareth J Jones - One of the best experts on this subject based on the ideXlab platform.
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evaluation of a computer program for non invasive determination of Pulmonary Shunt and ventilation perfusion mismatch
Journal of Clinical Monitoring and Computing, 2014Co-Authors: G G Lockwood, Nick Fung, Gareth J JonesAbstract:We describe a three-compartment model (Shunt and two perfused compartments) to analyse the relationship between inspired oxygen (FIO2) and arterial oxygen saturation (SaO2) in terms of Pulmonary Shunt and ventilation-perfusion ratio (VA/Q). The program was tested using 24 exact datasets, each with six pairs of FIO2 and SaO2 data points with known VA/Q and Shunt, generated by a complex calculator of gas exchange. Additional datasets were created by adding noise and rounding the exact sets, and by reducing the number of data points per dataset. The importance of the oxyhaemoglobin dissociation curve and the arterio-venous difference in oxygen content (avDO2) were also tested. Analysis using the three compartment model was more accurate than the two compartment model and less affected by data degradation. The absolute error in Shunt estimation was never more than 2.2 % for the exact and rounded datasets, but the error in VA/Q estimation was −29 to 19 % of the true value (10th–90th centiles). The characteristics of the well-ventilated compartment were not determined accurately. At extremes of cardiac output, an assumed value of avDO2 resulted in significant errors. It is probably advantageous to correct for foetal haemoglobin in neonatal datasets. Analysis of FIO2 versus SaO2 datasets using a three compartment model provides accurate estimates of Shunt and VA/Q when arterio-venous difference in oxygen content is known. The estimates may have value as objective measures of gas exchange, and as a visual guide for oxygen therapy.
Steen Andreassen - One of the best experts on this subject based on the ideXlab platform.
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Quantitative Assessment of Pulmonary Shunt and Ventilation-Perfusion Mismatch without a Blood Sample
2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2007Co-Authors: Bram W. Smith, Stephen E. Rees, Dan S. Karbing, Soren Kjaergaard, Steen AndreassenAbstract:The automated lung parameter estimator (ALPE) system for quantitatively assessing Pulmonary gas exchange in clinical practice has been shown to be useful for diagnosing lung dysfunction and monitoring treatment. However, the method requires at least one blood sample, which is routine in intensive care, but not readily available in many other hospital departments. This study investigates the feasibility of using default blood gas data and pulse oximetry to determine gas exchange parameters non-invasively. It was found that values of Shunt and V/Q mismatch estimated using only non-invasively measured data, correlated well with the same values found using more accurate, multiple invasive, methods. This method greatly improves the feasibility of using the ALPE method for diagnosing and monitoring patients outside the intensive care department.
Göran Hedenstierna - One of the best experts on this subject based on the ideXlab platform.
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Pulmonary Shunt is independent of decrease in cardiac output during unsupported spontaneous breathing in the pig.
Anesthesiology, 2013Co-Authors: Laszlo Vimlati, Anders Larsson, Göran Hedenstierna, Michael Lichtwarck-aschoffAbstract:Background: During mechanical ventilation (MV), Pulmonary Shunt is cardiac output (CO) dependent; however, whether this relationship is valid during unsupported spontaneous breathing (SB) is unknow ...
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Haemodynamic stability and Pulmonary Shunt during spontaneous breathing and mechanical ventilation in porcine lung collapse.
Acta Anaesthesiologica Scandinavica, 2012Co-Authors: Laszlo Vimlati, Anders Larsson, Göran Hedenstierna, Michael Lichtwarck-aschoffAbstract:BackgroundWe investigated the haemodynamic stability of a novel porcine model of lung collapse induced by negative pressure application (NPA). A secondary aim was to study whether Pulmonary Shunt c ...
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During spontaneous breathing cardiac output lacks major effect on Pulmonary Shunting in porcine lungs with partial collapse
Critical Care, 2012Co-Authors: Laszlo Vimlati, Anders Larsson, Göran Hedenstierna, Michael Lichtwarck-aschoffAbstract:Spontaneous breathing (SB) improves oxygenation compared to mechanical ventilation (MV), and does so even without recruit-ing atelectasis [1,2]. Since it cannot be excluded that cardiac output (CO) impacts on Pulmonary Shunt, we investigated whether Pulmonary Shunt correlates with CO in a porcine model of lung collapse.
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spontaneous breathing reduces Pulmonary Shunt independent of hypoxic vasoconstriction in the lung collapse model
2012Co-Authors: Laszlo Vimlati, Anders Larsson, Göran Hedenstierna, M LichtwarckaschoffAbstract:Background: Compared with mechanical ventilation (MV), spontaneous breathing (SB) improves oxygenation even without recruiting atelectatic lung areas, probably by redistributing perfusion to well v ...
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Atelectasis Formation During Anesthesia: Causes and Measures to Prevent It
Journal of Clinical Monitoring and Computing, 2000Co-Authors: Göran Hedenstierna, Hans U. RothenAbstract:Pulmonary gas exchange is regularly impaired during general anaesthesia with mechanical ventilation. This results in decreased oxygenation of blood. A major cause is collapse of lung tissue (atelectasis), which can be demonstrated by computed tomography but not by conventional chest x-ray. Collapsed lung tissue is present in 90% of all subjects, both during spontaneous breathing and after muscle paralysis, and whether intravenous or inhalational anaesthetics are used. There is a correlation between the amount of atelectasis and Pulmonary Shunt. Shunt does not increase with age. In obese patients, larger atelectatic areas are present than in lean ones. Finally, patients with chronic obstructive lung disease may show less or even no atelectasis. There are different procedures that can be used in order to prevent atelectasis or to reopen collapsed lung tissue. The application of positive end-expiratory pressure (PEEP) has been tested in several studies. On the average, arterial oxygenation does not improve markedly, and atelectasis may persist. Further, reopened lung units re-collapse rapidly after discontinuation of PEEP. Inflation of the lungs to an airway pressure of 40 cm H_2O, maintained for 7–8 seconds (recruitment or “vital capacity” manoeuvre), re-expands all previously collapsed lung tissue. During induction of anaesthesia, the use of a gas mixture, that includes a poorly absorbed gas such as nitrogen, may prevent the early formation of atelectasis. During ongoing anaesthesia, Pulmonary collapse reappears slowly if a low fraction of oxygen in nitrogen is used for the ventilation of the lungs after a previous VC-manoeuvre. On the other hand, ventilation of the lungs with pure oxygen results in a rapid reappearance of atelectasis. Thus, ventilation during anaesthesia should be done if possible with a moderate fraction of inspired oxygen (FIO_2, e.g. 0.3–0.4). Alternatively, if the lungs are ventilated with a high inspiratory fraction of oxygen, the use of PEEP may be considered. In summary, atelectasis is present in most humans during anaesthesia and is a major cause of impaired oxygenation. Avoiding high fractions of oxygen in inspired gas during induction and maintenance of anaesthesia may prevent formation of atelectasis. Finally, intermittent “vital capacity”-manoeuvres together with PEEP reduces the amount of atelectasis and Pulmonary Shunt.
Shinichi Ohtsuki - One of the best experts on this subject based on the ideXlab platform.
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right ventricle Pulmonary artery Shunt in first stage palliation of hypoplastic left heart syndrome
The Journal of Thoracic and Cardiovascular Surgery, 2003Co-Authors: Shunji Sano, Kozo Ishino, Masaaki Kawada, Sadahiko Arai, Shingo Kasahara, Tomohiro Asai, Zenichi Masuda, Mamoru Takeuchi, Shinichi OhtsukiAbstract:Abstract Objective Pulmonary overcirculation through a systemic-Pulmonary Shunt has been one of the major causes of early death after the Norwood procedure. To avoid this lethal complication, we constructed a right ventricle–Pulmonary Shunt in first-stage palliation of hypoplastic left heart syndrome. Methods Between February 1998 and February 2002, 19 consecutive infants, aged 6 to 57 days (median, 9 days) and weighing 1.6 to 3.9 kg (median, 3.0 kg), underwent a modified Norwood operation with the right ventricle–Pulmonary artery Shunt. The procedure included aortic reconstruction by direct anastomosis of the proximal main Pulmonary artery and a nonvalved polytetrafluoroethylene Shunt between a small right ventriculotomy and a distal stump of the main Pulmonary artery. The size of the Shunt used was 4 mm in 5 patients and 5 mm in 14. Results All patients were managed without any particular manipulation to control Pulmonary vascular resistance. There were 17 survivors (89%), including 3 patients weighing less than 2 kg. Two late deaths occurred due to obstruction of the right ventricle–Pulmonary artery Shunt. Thirteen patients underwent a stage II Glenn procedure after a mean interval of 6 months, with 2 hospital deaths. To date, a stage III Fontan procedure has been completed in 4 patients. Overall survival was 62% (13/19). Right ventricular fractional shortening at the last follow-up (3-48 months after stage I) ranged from 26% to 43% (n = 13, mean, 33%). Conclusion Without delicate postoperative management to control Pulmonary vascular resistance, the modified Norwood procedure using the right ventricle–Pulmonary Shunt provides a stable systemic circulation as well as adequate Pulmonary blood flow. This novel operation may be particularly beneficial to low-birth-weight infants with hypoplastic left heart syndrome.
