Dynamic Modeling, Simulation and Exergy Analysis of an Innovative Hydronic Heating System

In this study, dynamic modeling and simulation of a decentralized hydronic heating system has been performed. The simulated space heating system is a model of an innovative heating system of an apartment with a boiler that supplies heat for eight radiators which are served by distribution pipes. Eight small pumps, located at the outlet of the radiators instead of a central circulation pump, work according to demand, and supply each radiator with hot water only when required. A PID controller regulates the rotational speed of the pumps and consequently the power of the radiators to maintain the room temperature at the set point. To evaluate the performance of such a heating system, a model of the entire energy chain from generation to distribution is needed. Therefore, in this work, detailed sub-models for the hydraulic system have been developed and coupled with the model of a building to make a general model for simulating the performance of the whole system. The analysis has been carried out by simulation of the system using the object-oriented programing language Modelica. Dymola, which is a multi-domain modeling and simulation tool, has been used as simulation environment. The Modelica Standard Library 3.2 and the Modelica libraries for building simulation such as BaseLib, Database, Building and HVAC components libraries have been applied to simulate the hydraulic and thermal behavior of the system. In the next step, the system has been analyzed form exergy point of view and the simulation results from the dynamic model have been presented in an exergetic framework.

Combined inhalational and intravenous anesthesia at surgeries in patients with gastrointestinal cancers

Aim. To define efficiency and safety of the combined inhalational and intravenous anesthesia (isoflurane + propofol) in patients operated due to gastrointestinal cancer. Methods. 163 patients who were operated due to gastric cancer (119 patients), cancer of the head of the pancreas (24 patients) and colon cancer (20 patients) were examined. Central circulation parameters, autonomic nervous system status, serum cortisol and glucose levels, bispectral index in patients who underwent inhalational or combined inhalational and intravenous anesthesia were compared. Results. There was no significant difference of the examined parameters in patients who underwent combined inhalational and intravenous anesthesia (isoflurane + propofol) compared to patients in whom only inhalational anesthesia with isoflurane was used. Combination was characterized by less change of the examined parameters compared to baseline levels and prolonged emergence from anesthesia. Conclusion. Combined anesthesia is quite safe and effective if used in oncosurgery.

Evaluation of Success Rate and Access Time for an Adult Sternal Intraosseous Device Deployed in the Prehospital Setting

Introduction: Access to the vascular system of the critically ill or injured adult patient is essential for resuscitation. Whether due to trauma or disease, vascular collapse may delay or preclude even experienced medical providers from obtaining standard intravenous (IV) access. Access to the highly vascular intramedullary space of long bones provides a direct link to central circulation. The sternum is a thin bone easily identified by external landmarks that contains well-vascularized marrow. The intraosseous (IO) route rapidly and reliably delivers fluids, blood products, and medications. Resuscitation fluids administered by IV or IO achieve similar transit times to central circulation. The FAST-1 Intraosseous Infusion System is the first FDA-approved mechanical sternal IO device. The objectives of this study were to: (1) determine the success rate of FAST-1 sternal IO device deployment in the prehospital setting; (2) compare the time of successful sternal IO device placement to published data regarding time to IV access; and (3) describe immediate complications of sternal IO use.Methods: All paramedics in the City of Portsmouth, Virginia were trained to correctly deploy the FAST-1 sternal IO device during a mandatory education session with the study investigators. The study subjects were critically ill or injured adult patients in cardiac arrest treated by paramedics during a one-year period. When a patient was identified as meeting study criteria, the paramedic initiated standard protocols; the FAST-1 sternal IO was substituted for the peripheral IV to establish vascular access. Time to deployment was measured and successful placement was defined as insertion of the needle, with subsequent aspiration and fluid flow without infiltration.Results: Over the one-year period, paramedics attempted 41 FAST-1 insertions in the pre-hospital setting. Thirty (73%) of these were placed successfully. The mean time to successful placement was 67 seconds for 28 attempts; three of the 31 insertions did not have times recorded by the paramedic. Paramedics listed the problems with FAST-1 insertion, including: (1) difficulty with adhesive after device placement (3 events); (2) failure of needles to retract and operator had to pull the device out of the skin (2 events); and (3) slow flow (1 event). Emergency department physicians noted two events of minor bleeding around the site of device placement.Conclusion: This is the first study to prospectively evaluate the prehospital use of the FAST-1 sternal IO as a first-line device to obtain vascular access in the critically ill or injured patient. The FAST-1 sternal IO device can be a valuable tool in the paramedic arsenal for the treatment of the critically ill or injured patient. The device may be of particular interest to specialty disaster teams that deploy in austere environments.