Blood Distribution System Research Articles

A column generation approach for an inventory routing problem with fuzzy time windows

This paper proposes a novel approach towards inventory routing problems with fuzzy time windows considering customer satisfaction for arrival intervals. In the presented model, a multi-priority structure for visiting the customers is proposed. In this study, customers are divided into three categories according to their features. These features have different degrees of importance from the distributer’s perspective. The satisfaction level of customers plays an important role in the decision of the supplier to fulfill their demand in each period. Since the proposed model is characterized as a highly complex problem, a decomposition-based heuristic approach is developed to obtain a high-quality solution in reasonable computational time. Moreover, to properly calibrate the parameters of the developed algorithm and decrease the number of experiments, Taguchi experimental design technique is utilized to measure the efficiency of the parameter. Comparing the obtained results with previous studies indicates that the presented procedure outperforms similar heuristic-based solution techniques proposed in the relevant literature. Finally, the practical application of the proposed model is discussed by studying a real-world case study of a blood distribution system in Tehran.

A Blood Bank Network Design Problem with Integrated Facility Location, Inventory and Routing Decisions

We aim to design an effective supply chain network for a blood distribution system to satisfy the needs of hospitals in a certain region. In the analyzed current system, each hospital keeps a certain level of inventory, received at certain time periods by the shipments from a main blood bank. We propose an alternative system, in which some of the hospitals are selected as local blood banks (LBB) and all other hospitals will be assigned to an LBB. More frequent shipments will be made from LBBs to these hospitals, leading to lower inventory levels to be kept at each hospital. The inventories kept separately at the hospitals in the current system will be pooled at the selected LBBs in the proposed system. We develop a mixed integer nonlinear programming (MINLP) model to determine the optimal selection of LBBs, assignment of hospitals to LBBs, optimal inventory levels at each LBB and routing decisions among the facilities in order to minimize total system costs. We also propose a piecewise linear approximation method and a simulated annealing heuristic approach to find the solution of this problem. The proposed model and the solution techniques are applied on a real life case study for the blood distribution network in Istanbul. It is observed that significant improvements can be obtained by the proposed system when compared to the current design. Performances of the solution methods are also compared and a sensitivity analysis related to system parameters is presented via detailed numerical experiments.

Patterns of arterial vascularization in swine hearts

Abstract: This study aimed to characterize the patterns of arterial vascularization in swine hearts. Ninety swine hearts were submitted to the Spalteholz diaphanization technique in order to dissect the coronary arteries. Three types of arterial vascularization patterns were characterized through the behaviorof the rami circumflexus and interventricularis, namely: balanced, right and left types. The balanced pattern was the most frequently (42.2%); in this case, the rami circumflexus and interventricularis occupied their respective sulci. The right type (40%) was further categorized into three vascularization subtypes. In the first, ramus circumflexus dexter branched from the ramus interventricularis subsinuosus. In the second, the arteria coronaria dextra branched from ramus interventricularis subsinuosus and ramus circumflexus. In the third model, arteria coronaria sinister branched from ramus interventricularis paraconalis. The left type (17.7%) exhibited two subtypes. In the first, ramus interventricularis paraconalis ran through the entire corresponding sulcus and the ventral third of sulcus interventricularis subsinuosus, and ramus interventricularis subsinuosus occupied the dorsal and middle third of its respective sulcus. In the second, ramus interventricularis subsinuosus branched from arteria coronaria dextra and ran through the dorsal and medium thirds of its respective sulcus, and the ventral third was occupied by the collateral branch of ramus circumflexus sinister. Our results reinforce the thesis that the blood distribution system through the coronary artery in swine is similar to human, not only in qualitative but also by a quantitative comparison.

INTERACTIONS AND SYNCHRONIZATION IN THE CARDIOVASCULAR SYSTEM

There is strong evidence for couplings between the five oscillatory processes that characterize the human blood distribution system. In particular, mutual modulation and/or episodes of synchronization between the oscillations may be observed for a variety of different cardiovascular signals. Such phenomena can reveal information about the nature and strength of the couplings, which in turn reflect the state of the organism in sickness or in health. Earlier work on the inter-oscillator interactions is reviewed briefly, and some recent research on cardio-respiratory synchronization is considered in more detail. It is reported that, for rats, the directionality of the cardiorespiratory coupling reverses under anæsthesia. The interplay between synchronization and modulation is discussed and their coexistence in the cardiorespiratory interaction is illustrated.

Spatial Synchronization in the Human Cardiovascular System

Concepts developed for the synchronization analysis of noisy coupled nonlinear oscillators are used to study the spatial synchronization of oscillations in the blood distribution system. We reveal that the cardiac and respiratory oscillations observed at different sites of the system are strongly phase and frequency synchronized, while the spatial synchronization of oscillations that originate locally is weaker. The results obtained support the hypothesis that the entire cardiovascular system is characterised by the same dynamics. The human cardiovascular system distributes matter and energy to the cells and removes byproducts of their metabolism. The cells extract matter and energy from the blood which is pumped by the heart into the network of vessels. The lungs, where the blood becomes oxygenated, are also part of the cardiovascular network. The heart of a relaxed, healthy subject, pumps an amount equivalent to the total amount of blood in the body in approximately one minute. 1) Thus, in cardiovascular dynamics we consider the dynamics of blood distribution through the cardiovascular network on a time scale of around one minute. It can be characterised by the dynamics of the blood flow and the blood pressure in the system, and the activity of the lungs and heart pump. The function of the heart is manifested as electric potentials spread across the heart muscle, and as a mechanical pump that rhythmically expels the blood into the arterial network approximately once per second. However, the period of the heart cycle is not constant but, rather, varies in time. The frequency of respiration also varies, between 0.15 and 0.3 Hz. Consequently, the flow and the pressure change in an oscillatory fashion with time, and do so on several different time scales. The vessel walls are not stiff: their radii continually alter, thus giving rise to a variable resistance to flow. Three peripheral mechanisms are known to contribute to the resistance or compliance of the vessels: the intrinsic myogenic mechanism, based on continuous contraction and relaxation of smooth muscle cells; the neurogenic control provided by the autonomous nerve innervation of vessels; and endothelium mediated contraction and relaxation of the vessels. 2) - 4) Each of these processes manifests in an oscillatory manner, and their characteristic frequencies are around 0.1, 0.04 and 0.01 Hz, respectively. Arterial blood flow is characterised by high pressure and low resistance, and the heart frequency dominates in both the flow and pressure. Flow in veins is

Causes and Effects of Heterogeneous Perfusion in Tumors

A characteristic of solid tumors is their heterogeneous distribution of blood flow, with significant hypoxia and acidity in low-flow regions. We review effects of heterogeneous tumor perfusion are reviewed and propose a conceptual model for its cause. Hypoxicacidic regions are resistant to chemo- and radiotherapy and may stimulate progression to a more metastatic phenotype. In normal tissues, hypoxia and acidity induce angiogenesis, which is expected to improve perfusion. However, aggressive tumors can have high local microvessel density simultaneously with significant regions of hypoxia and acidosis. A possible explanation for this apparent contradiction is that the mechanisms regulating growth and adaptation of vascular networks are impaired. According to a recent theory for structural adaptation of vascular networks, four interrelated adaptive responses can work as a selfregulating system to produce a mature and efficient blood distribution system in normal tissues. It is proposed that heterogeneous perfusion in tumors may result from perturbation of this system. Angiogenesis may increase perfusion heterogeneity in tumors by increasing the disparity between parallel low- and highresistance flow pathways. This conceptual model provides a basis for future rational therapies. For example, it indicates that selective destruction of tumor vasculature may increase perfusion efficiency and improve therapeutic efficacy.

An evaluation of inventory and transportation policies of a regional blood distribution system

Blood is a valuable but perishable community resource. Regional blood centers coordinate the blood drawing and inventory policies of the hospital blood banks in a region for more efficient use of the resource. This study used a simulation model to analyze the costs and effects of several different operational policies for a regional blood center. Simulated experiments were carried out in four areas: (1) increasing the amount of blood available, (2) changing the number of delivery vehicles, (3) comparing two types of inventory consignment policies (shipping blood to hospitals with a recall privilege and frequent redistribution of blood amongst regional hospitals) to a direct-sale, no-redistribution policy, and (4) examining the effect of sending fresher blood supplies as inventories to hospitals with lower probabilities of transfusion. The results of the third experiment are presented in detail. It was found that periodic redistribution of the regional inventory yielded lower expiration rates and lower shortage rates. The results of the other three experiments are presented briefly.

The Long Island Blood Distribution System as a Prototype for Regional Blood Management

Each year over two million hospitalized Americans depend upon the timely availability of the right type of blood products at 6,000 hospital blood banks (HBB's) in the United States. If the right blood products are not available at the HBB when required, then medical complications or postponements of elective surgery can result which translates to extra days of hospitalization and expense. On the other hand, since most blood products may only be administered to a patient of the same blood type within 21 days of collection, overstocking at HBB's leads to low utilization, which increases costs and is wasteful of the scarce blood resource. The Long Island blood distribution system was set up as a prototype of a regional blood center and the hospital blood banks that it services collaborating to preplan regional blood flow. It maximizes blood availability and utilization according to a Programmed Blood Distribution System (PBDS) model and strategy that has been shown to be generally applicable. PBDS schedules blood deliveries according to statistical estimates of the needs of each HBB and monitors actual requirements to adjust deliveries when indicated by control chart techniques. In addition, it provides a daily forecasting of short-term shortages and surpluses for the next several days that results in controlled movement of blood to and from adjoining regions. Finally, the system is able to adjust the regional strategy so that availability is reduced uniformly at all HBB's during periods of seasonal, regional shortages. PBDS has drastically improved utilization and availability of blood on Long Island: wastage has been reduced by 80%, and delivery costs by 64%. This prototype is acting as a model for other regional blood centers in the United States and for other national blood services as a basis for planning and controlling blood flow in a geographic area. It usually replaces preexisting procedures where a regional blood center collects blood based upon gross estimates and reacts to requests for blood by individual HBB's on the basis of experience and on the currently prevailing inventory situation.

Computer-based regional blood distribution

This paper describes the regional blood distribution system used in Long Island, New York. A brief review of the theoretical model is given first. Then the operational system is discussed and the automation support is described. Finally, results are presented and evaluated.