Congestive Volume Research Articles

Resource Allocation in Flow-Constrained Areas with Stochastic Termination Times

A stochastic air traffic flow management problem arises when airspace congestion is predicted, usually because of a weather disturbance, so that the number of flights passing through a volume of airspace must be reduced. In the United States, in such situations, the FAA identifies the congested volume of airspace and implements an airspace flow program to regulate traffic. An optimization model was formulated for the assignment of dispositions to flights whose preferred flight plans pass through the congestion. For each flight, the disposition can be either to depart as scheduled but via a secondary route that avoids the congestion or to use the originally intended route but to depart with a controlled departure time and accompanying ground delay. The capacity of the congested area may increase once the weather activity clears. The model is a two-stage stochastic program that represents the time of this capacity windfall as a random variable and determines expected costs given a second-stage decision, conditioning on that time. The goal is to minimize the expected cost over the entire distribution of possible capacity increase times.

A comment on W. Wei and M. Hansen’s benefit estimation in “An aggregate demand model for air passenger traffic in the hub-and-spoke network”

This comment analyzes the demand model and method used by W. Wei and M. Hansen for computing the benefits of an airport capacity extension. The log-linear specification and coefficients of the demand function imply that the airport extension’s positive effect on demand decreases with the volume of traffic and associated congestion. If this unlikely result is accepted, the surplus method used by Wei and Hansen underestimates the users’ investment benefit. The note argues that the marginal willingness to pay for a capacity extension should rather increase with congestion. If this is the case, the method used by Wei and Hansen could actually overestimates the benefit. A better specification would rather allow for a function concave to the origin in order to account for capacity constraints, and also set a maximum finite price. Above all, a fair evaluation of the users’ benefit should be based on a function which explicitly includes a variable, or function of variables, that permits an estimation of the users’ cost of congestion.

Graft Selection Algorithm Based on Congestion Volume for Adult Living Donor Liver Transplantation

A major concern in adult-to-adult living donor liver transplantation is the selection of graft type; that is, is it is better to use the right lobe with or without the middle hepatic vein (MHV)? This choice has a considerable impact on donor safety, vascular reconstruction and graft function in the recipient. To facilitate making an appropriate choice, on the basis of a preliminary study (n = 17), we herein propose a graft selection algorithm using three parameters: graft-to-recipient body weight ratio (GRWR), percentage remnant liver volume (%RLV) and estimated congestion ratio (ECR). The algorithm was evaluated with 50 consecutive cases with respect to postoperative liver function of donors and recipients and survival of recipients. Postoperative recovery was comparable between the two groups (p = NS). The overall cumulative 18-month survival rate was 86.7% for the 'with MHV graft group', and 76.1% for the gwithout MHV graft grouph (p = NS). For 41 cases (82%), graft types were chosen according to the algorithm, whereas the remaining 9 cases (18%) needed detailed discussion of donor, recipient and operative factors. In conclusion, we constructed a graft selection algorithm based on congestion volume, which will contribute to objective graft-type selection in adult-to-adult LDLT.

Hepatobiliary and pancreatic: Acute Budd–Chiari syndrome treated by systemic thrombolytic therapy

The Budd–Chiari syndrome is an uncommon disorder characterized by hepatic venous outflow obstruction at the level of hepatic venules, hepatic veins or the inferior vena cava. The mode of presentation is highly variable but the majority of patients present after weeks or months with hepatomegaly and ascites. Patients who present acutely (within days) also have hepatomegaly and ascites and, in addition, may have abdominal pain, jaundice and hepatic encephalopathy. The management of patients with the Budd–Chiari syndrome is influenced by the cause, anatomical considerations and the rate of progression of disease. For many patients, therapeutic options include portosystemic shunts and liver transplantation. Percutaneous transluminal balloon angioplasty can also be used for those patients with membranous obstruction of the inferior vena cava. In the acute Budd–Chiari syndrome, the role of thrombolytic therapy remains unclear but appeared to be helpful in the patient illustrated below. The 22-year-old woman was admitted to hospital with epigastric pain, nausea and vomiting. On examination, her abdomen was distended with ascites. Liver function tests were abnormal including a moderate elevation of alanine aminotransferase (755 u/L) and aspartate aminotransferase (525 u/L). A contrast-enhanced computed tomography (CT) scan of the abdomen (Fig. 1) showed extensive congestion of the liver with thrombosis of the inferior vena cava (arrow). The non-congested area is enhanced by contrast material. She also had thrombosis of the right trunk of the portal vein and the superior mesenteric vein. Liver volume studies revealed a total liver volume of 2125 mL with a congested volume of 1890 mL. Various tests of coagulation were within the reference range. She was treated with intravenous heparin (10 000 units/day) and urokinase (240 000 units/day). Ascites and pleural effusions resolved after 9 weeks and she was subsequently changed to anticoagulation with warfarin. A repeat CT scan after 14 weeks showed resolution of the thrombus in the inferior vena cava (arrow) and a marked reduction in the area of congestion (Fig. 2). However, there was persistent thrombosis of the right hepatic vein. Liver volume studies revealed a total volume of 1602 mL with a congested volume of 682 mL. She has been followed for 21 months and is currently asymptomatic with normal liver function tests. Contributed by

Validity of preoperative volumetric analysis of congestion volume in living donor liver transplantation using three-dimensional computed tomography

Reconstruction of middle hepatic vein (MHV) tributaries is controversial in right-lobe living donor liver transplantation (LDLT). This study aimed to evaluate the appropriateness of reconstructing MHV tributaries by volumetry using 3-dimensional computed tomography (3D-CT). Between November 2003 and January 2005, 42 donor livers (right-lobe graft, n = 25; left-lobe graft, n = 17) were evaluated using this software. The total congestion volume (CV) associated with the MHV tributaries and the inferior right hepatic vein (IRHV), and graft volume (GV) were calculated. In recipients with right-lobe grafts, CV/(right liver volume [RLV]) and (GV - CV)/(standard liver volume [SLV]) were compared between 2 groups: with reconstruction (n = 16) and without reconstruction (n = 9). To evaluate the influence of CV on the remnant right lobe in donors, total bilirubin was compared between 2 groups: high CV (CV > 20%, n = 13) or low CV (CV < or = 20%, n = 4). The mean CV/RLV ratio was 32.3 +/- 17.1% (V5, 15.2 +/- 9.9%; V8, 9.2 +/- 4.1%; and IRHV, 8.5 +/- 11.4%) and the maximum ratio was as high as 80.8%. The mean (GV - CV)/SLV ratio before reconstruction in patients with or without reconstruction resulted in 33.5 +/- 12.8% and 55.4 +/- 12.9%, respectively (P < 0.01). In donors, total bilirubin was significantly high in the high CV group on postoperative day 1 compared with the low CV group (P < 0.05). In conclusion, calculation of CV using 3D-CT software proved to be very useful. We concluded that this evaluation should be an integral part of procedure planning, especially for right-lobe LDLT.

Protective effect ofSpirulina against doxorubicin-induced cardiotoxicity

The generation of reactive oxygen species and mitochondrial dysfunction has been implicated in doxorubicin (DOX)-induced cardiotoxicity. The aim of the present study was to determine whether Spirulina, a blue-green algae, could serve as a cardioprotective agent during DOX treatment in a mouse model. Mice were treated with DOX (4 mg/kg bw, intraperitoneally), weekly, for 4 weeks. Spirulina was administered orally for 3 days twice daily, then for 7 weeks along with the four equal injections of DOX. Cardiotoxicity was assessed, at 3 weeks after the end of the DOX-treatment period, by mortality, volume of ascites, liver congestion, oxidative stress and ultrastructural changes of heart tissue. The DOX-treated animals showed higher mortality (53%) and more ascites. Myocardial damage, as assessed by ultrastructural changes, showed loss of myofibrils, cytoplasmic vacuolization and mitochondrial swelling. Myocardial superoxide dismutase and glutathione peroxidase activities were decreased and lipid peroxidation was increased. Pretreatment with Spirulina significantly protected the mice from DOX-induced cardiotoxic effects as evidenced from lower mortality (26%), less ascites, lower levels of lipid peroxidation, normalization of antioxidant enzymes and ultrastructural studies showing minimal damage to the heart. In vitro cytotoxic studies using ovarian cancer cells demonstrated that Spirulina did not compromise the anti-tumor activity of doxorubicin. These results suggest that Spirulina has a protective effect against cardiotoxicity induced by DOX and it may, therefore, improve the therapeutic index of DOX.

Nucleotide-mediated inhibition of alveolar fluid clearance in BALB/c mice after respiratory syncytial virus infection.

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in infants and children worldwide. Intranasal infection of BALB/c mice with RSV strain A2, but not ultraviolet-inactivated RSV, for 2 or 4 days reduced basal alveolar fluid clearance (AFC), a seminal function of bronchoalveolar epithelium, and caused loss of AFC sensitivity to amiloride inhibition. Reduced AFC was temporally associated with increased lung water content but was not a consequence of increased epithelial permeability or cell death. Reduced AFC was also not due to decreased transcription of epithelial Na+ channel subunit genes in lung tissue. RSV-mediated inhibition of AFC 2 days after infection was rapidly prevented by addition to the instillate of P2Y receptor antagonists (suramin and XAMR-0721) or enzymes that degrade UTP, but not those that degrade ATP. After UTP degradation, AFC returned to control levels but was no longer sensitive to amiloride. UTP at nanomolar concentrations recapitulated the AFC inhibitory effect of RSV in normal mice and mice infected with RSV for 6 days, indicating that normalization of AFC at this time point is a consequence of cessation of UTP release, rather than P2Y receptor desensitization. We conclude that RSV infection of the bronchoalveolar epithelium results in reduced AFC as a consequence of autocrine feedback inhibition mediated by UTP. These studies are the first to demonstrate AFC inhibition by an important pulmonary viral pathogen. Reduced AFC may result in formation of an increased volume of fluid mucus, airway congestion, and rhinorrhea, all features of severe RSV disease.

Empirical Analysis for Congestion Pricing Using Traffic Simulation

Many economical considerations between congestion and price have been done. The practical road pricing techniques have been discussed as well. In this study, a traffic simulation model is used to calculate congestion price on urban expressway. The average cost function is estimated from the observed data on Osaka-Sakai route in Hanshin Expressway. The standard value of congestion price is estimated as well. In addition, the influence of introduction of road pricing is counted as social surplus and reduction of congestion volume. These results would show that the road pricing works effectively on the urban expressway.

Clinical Course of Acute Maxillary Sinusitis Documented by Sequential MRI Scanning

A prospective study was designed to assess clinical and mucosal changes that occur during resolution of acute maxillary sinusitis. Thirteen previously healthy subjects with symptoms of acute sinusitis and radiographic opacification of at least one maxillary sinus were entered into the study and treated with amoxicillin/clavulinate potassium. Assessment of clinical symptoms, clinical examination, and magnetic resonance imaging (MRI) of the maxillary sinuses were performed at baseline and at days 3, 7, 10, 14, 21, 28 and 56 after initiation of therapy. The T2 values from the MRI scans were analyzed to approximate the more viscous and more fluid-like components of the maxillary sinus contents. After three days of antibiotic therapy, there was marked improvement in facial tenderness, thickness of nasal discharge, volume of nasal discharge, headache, and nasal congestion. Ten to 14 days of treatment were required, however, for improvement in nasal patency. MRI analysis of the volume percentage of air in the involved sinuses showed that by 10 days, only half of the opacification (fluid and thickened mucosa) had resolved. By 56 days, the sinuses were only about 80% aerated. This improvement was attributed mainly to resolution of the more fluid-like component. This study shows that: (1) tissue/fluid changes in sinusitis can be followed with MRI, and (2) although treatment of acute maxillary sinusitis generally results in clinical resolution of symptoms within one week, mucosal changes can persist for 8 weeks or more.