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PubMed1989

Mucus transport in a miniaturized simulated cough machine: effect of constriction and serous layer simulant.

The transport of mucus gel simulant (MGS) in a constricted simulated cough machine, using blood plasma as a serous layer simulant (SLS), was investigated. MGS was prepared from locust bean gum solutions crosslinked with varying amounts of added borate to produce gels of varying spinnability (filance). The model trachea was a plexiglass channel of rectangular cross-section with the plane bottom surface. The upper surface included a sinusoidal protrusion which provided a flow convergence with minimum gaps of 6, 4 and 2 mm. Experiments for mucus transport were conducted for these minimum gaps, as well as for the non-convergent case (12 mm gap). Miniaturization of sample quantity was achieved by keeping the MGS layer depth constant (0.5 or 1 mm) but reducing the zone of loading from 13.4 cm to 1 cm, thus reducing the sample requirement to as little as 0.2 ml. MGS transport was determined as the minimum displacement of a line of marker dye placed in the MGS layer at the point of minimum constriction gap. It was shown that in all cases (dry as well as with SLS), MGS transport increased as the minimum constriction gap between the plane and the convergent top surface decreased. This increase was further enhanced if an SLS of lesser viscosity was used. It was also found that the transport of MGS increased as the depth of MGS layer increased or as the filance decreased in both non-constricted and constricted cases. The relationship between MGS transport and filance was maintained even in the presence of an SLS layer.

Airway Obstruction↗
PubMed2006

Self-assessment of performance among surgical trainees during simulated procedures in a simulated operating theater.

BACKGROUND: The ability of surgeons to assess their own performance is essential for training and self-regulation. The latter is based on the premise that they recognize their weaknesses and seek remedial action accordingly. METHODS: Twenty-seven surgical trainees performed a simulated saphenofemoral high-tie on a synthetic model in a simulated operating theater. The performance assessment consisted of blinded rating of technical skills and a global rating of team skills by a human factors expert and a trained surgical research fellow. Subjects also were asked to assess their own performance using the same methods. Spearman's rho was used for data analysis. RESULTS: There was a strong correlation between the experts rating of technical skills and self-assessment (rho = .64). However, the correlation improved with increasing experience. It was .24 for junior trainees, .43 for those with intermediate experience, and .52 for senior trainees. There was a low correlation between the self-assessment and the expert scores for human factors skills (rho = .31). The correlation was higher for the 2 junior groups compared with the senior trainees. CONCLUSIONS: Unlike other studies on self-assessment, this study found that senior surgical trainees are accurate in their self-assessment of technical skills. However, this was not true in the case of human factors skills.

Clinical Competence↗
PubMed2002

Simulating proteins at constant pH: An approach combining molecular dynamics and Monte Carlo simulation.

For the structure and function of proteins, the pH of the solution is one of the determining parameters. Current molecular dynamics (MD) simulations account for the solution pH only in a limited way by keeping each titratable site in a chosen protonation state. We present an algorithm that generates trajectories at a Boltzmann distributed ensemble of protonation states by a combination of MD and Monte Carlo (MC) simulation. The algorithm is useful for pH-dependent structural studies and to investigate in detail the titration behavior of proteins. The method is tested on the acidic residues of the protein hen egg white lysozyme. It is shown that small structural changes may have a big effect on the pK(A) values of titratable residues.

Algorithms↗
PubMedDate not supplied

Simulation of micropopulations in epidemiology: tutorial. 3. Simulation model evaluation methods. A series of tutorials illustrated by coronary heart disease models.

This is the third in a series of tutorials concerning the simulation of micropopulation models to support epidemiological research. The series emphasizes techniques used in studies at the National Micropopulation Simulation Resource at the University of Minnesota. For pedagogic purposes, applications to coronary heart disease (CHD) models are used to illustrate the principles and methodologies employed. All of the models presented are implemented using available software. A variety of tests and techniques are used to evaluate these models. This tutorial presents some of those methods stressing the advantages and limitations of the tests rather than the formal definitions. To make the evaluation methods more understandable, some of the risk factors for CHD models are introduced. The interpretation of the evaluation depends critically on the goals of the modeling effort. The subset of evaluation methods presented includes investigations of the epidemiological, mathematical and statistical aspects of the models.

Computer Simulation↗
PubMed1993

A burn patient resuscitation therapy designed by computer simulation (BET). Part 1: Simulation studies.

This study presents an analysis of the fluid, electrolyte and colloid needs of burn patients during the shock phase. A digital simulation technique was used which had previously been validated and published in burned patients (Roa et al., 1988). After analysing the repercussions of both burns and various resuscitation procedures, a fluid therapy method (BET) has been designed using a burn patient simulator, which has been characterized by its effectiveness and minimal side-effects. The characteristics of the BET method are a low volume of infusion resuscitation solution (220 ml/h/m2 burned body surface area (BBSA)) and a rapid and large volume of colloidal substances (with colloid concentrations of 10, 7.5 and 5 g/100 ml during the first three 8 h periods of the first postburn day and 2.5 g/100 ml until the 40th h postburn).

Burns↗
PubMed1990

CT simulator: a new 3-D planning and simulating system for radiotherapy: Part 1. Description of system.

A real time CT-linked 3-D treatment planning system, called a CT simulator, has been developed. The basic system consists of a CT scanner, a multi-image display component, a treatment planning device with real time visual optimization, and a laser beam projecting component. All the components are connected on line. The system can be conveniently used for 3-D planning and simulation for radiation therapy within a reasonably short period of time.

Computer Simulation↗
PubMedDate not supplied

Validation of an MRI/PET landmark registration method using 3D simulated PET images and point simulations.

Three-dimensional (3D) simulated PET images generated from MRI were used to validate a multimodality registration technique based on the identification of internal anatomical landmarks. In addition, point-based simulations were compared with registration datasets acquired over 3 yr of routine use of the technique. Registration errors were found to range from 1.0 mm at the brain centre to 2.8 mm in each dimension at the brain surface.

Computer Simulation↗
PubMed2006

Simulators in training: defining the optimal role for various simulation models in the training environment.

Clearly, the potential applications for simulation training in endoscopy are vast. Endoscopy models may serve as a platform to introduce new skills, to maintain proficiency, or even to assess competency. As these applications are explored fully, the strengths and weaknesses of specific devices will dictate their roles. Educators must ensure that these roles are founded on reliable research but remain mindful that simulators are only tools to augment clinical training, with the goal of benefiting both student and patient, and are not a replacement for patient-based experience.

Animals↗
PubMed2006

Numerical modeling of simulated blood flow in idealized composite arterial coronary grafts: steady state simulations.

This paper presents a comparative study of simulated blood flow in different configurations of simplified composite arterial coronary grafts (CACGs). Even though the composite arterial grafting is increasingly used in cardiac surgery, it is still questionable whether or not the blood flow in such grafts can adequately meet the demands of the native myocardial circulation. A computational fluid dynamics (CFD) model was developed to conduct computer-based studies of simulated blood flow in four different geometric configurations of CACGs, corresponding to routinely used networks in cardiac surgery coronary grafts (T, Y, Pi and sequential). The flow was assumed three-dimensional, laminar and steady and the fluid as Newtonian, while the vessel walls were considered as inelastic and impermeable. It was concluded that local haemodynamics, practically described by velocity, pressure drop, wall shear stress (WSS) and flow rates, may be strongly influenced by the local geometry, especially at the anastomotic sites. The computations were made at mean flow rates of 37.5, 75 and 150ml/min. The side-branch outflow rates, computed for each bypass graft, showed noticeable differences. The results, which were found both qualitatively and quantitatively consistent with other studies, indicate that the Pi-graft exhibits significantly less uniform distribution of outflow rates than the other geometric configurations. Moreover, prominent variations in WSS and velocity distribution among the assessed CACGs were predicted, showing remarkable flow interactions among the arterial branches. The lowest shear stress regions were found on the lateral walls of bifurcations, which are predominantly susceptible to the occurrence of coronary artery disease (CAD). In contrast, the highest WSS were observed at the turn of the arterial branches.

Computer Simulation↗
PubMed2007

Preoperative simulation of postoperative iris-fixated phakic intraocular lens position and simulation of aging using high-resolution Scheimpflug imaging.

To increase postoperative safety after implantation of iris-fixated phakic intraocular lenses (pIOLs), optimal preoperative evaluation and patient selection is mandatory. We present a new software tool in a high-resolution Scheimpflug imaging device that precisely simulates the postoperative position of an iris-fixated pIOL and also simulates the effect of aging on the pIOL's position.

Adult↗
PubMed2004

Assessing simulated patients in an educational setting: the MaSP (Maastricht Assessment of Simulated Patients).

CONTEXT: For more than two decades the Medical School in Maastricht, the Netherlands, has used simulated patients (SPs) to provide students with opportunities to practise their skills in communication and physical examination. In this educational setting a student meets a SP in a videotaped session. Feedback by the SP to the student at the end of the session is considered an important educational feature. We found no instruments to assess individual SP performance during those sessions. OBJECTIVE: To develop a valid, reliable and feasible instrument to evaluate the performance of SPs. METHODS: The content of the instrument was validated through interviews with students, teachers and experts who are involved with SPs. They were asked to indicate key features of good SP performance. Based on the interviews, a written checklist was developed to measure individual SP performance. The instrument was evaluated in a regular SP session at the medical school, involving 152 students and their teachers. MAIN OUTCOMES: All interviewees considered the scale to be satisfactory and the instrument to be valid. The feasibility and reliability of the checklists were investigated using the data of 398 returned checklists. Cronbach's alpha was found to be 0.73. Generalizability analysis showed that 12 completed checklists were required to obtain a reliable assessment of one SP. CONCLUSIONS: The Maastricht Assessment of Simulated Patients (MaSP) appears to be a valid, reliable and feasible tool to assess the performance of SPs in an educational setting.

Attitude of Health Personnel↗
PubMed2003

Quality assurance for computed-tomography simulators and the computed-tomography-simulation process: report of the AAPM Radiation Therapy Committee Task Group No. 66.

This document presents recommendations of the American Association of Physicists in Medicine (AAPM) for quality assurance of computed-tomography- (CT) simulators and CT-simulation process. This report was prepared by Task Group No. 66 of the AAPM Radiation Therapy Committee. It was approved by the Radiation Therapy Committee and by the AAPM Science Council.

Computer Simulation↗
PubMed2001

Biomolecular simulations: recent developments in force fields, simulations of enzyme catalysis, protein-ligand, protein-protein, and protein-nucleic acid noncovalent interactions.

Computer modeling has been developed and widely applied in studying molecules of biological interest. The force field is the cornerstone of computer simulations, and many force fields have been developed and successfully applied in these simulations. Two interesting areas are (a) studying enzyme catalytic mechanisms using a combination of quantum mechanics and molecular mechanics, and (b) studying macromolecular dynamics and interactions using molecular dynamics (MD) and free energy (FE) calculation methods. Enzyme catalysis involves forming and breaking of covalent bonds and requires the use of quantum mechanics. Noncovalent interactions appear ubiquitously in biology, but here we confine ourselves to review only noncovalent interactions between protein and protein, protein and ligand, and protein and nucleic acids.

Catalysis↗
PubMed2000

[A simulated study of effects of simulated hypovolemia on cardiovascular response to orthostatic stress].

Objective. To study the effects of hypovolemia on cardiovascular response to orthostatic stress, and to investigate the role of hypovolemia in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness. Method. The effects of loss of blood volume had been incorporated in the sub-model of blood redistribution in the model developed for simulating the cardiovascular response to lower body negative pressure (LBNP). With the help of the model, we simulated the changes of heart rate (HR) and blood pressure (BP) during LBNP after 0-25% loss of blood volume. Result. When the amount of decrease of blood volume was less than 5% of the total blood volume, HR and BP could be maintained in normal range during LBNP through baroreflex regulation. When the amount of the decrease of blood volume was more than 15% of the total blood volume, HR and BP could be kept in normal range when the subject was supine and at rest. But BP fell sharply and the cardiovascular system almost collapsed during orthostatic exposure. Conclusion. Decrease of blood volume causes significant degradations of cardiovascular response to orthostatic stress.

Aerospace Medicine↗
PubMed1997

The Sophus anaesthesia simulator v. 2.0. A Windows 95 control-center of a full-scale simulator.

The Sophus group was founded in Denmark in 1992 with the aims of doing research into human error in anaesthesiology. Development of a simulation-environment was seen as one of the tools for research and training. This article describes the PC user interface of the SOPHUS anaesthesia simulator, SOPHUS v. 2.0 for Windows 95, and the script language, SASL v. 1.2. The script language provides possibilities of making scenarios, which develop in different directions according to the treatment of the patient by means of IF/THEN-statements, loops etc.

Anesthesiology↗
PubMed1992

Development of a diagnostic and therapeutic simulation system based on patient data and specialist's knowledge. I. Simulation of diagnostic process.

A new simulation system of diagnostic and therapeutic processes is developed. The aim is to train medical students for the practical use of their knowledge, utilizing patient data in a total hospital information system. The knowledge in the system is presented by the specialists for every case. In medical school there are many specialists in various fields. With their cooperation the system can grow up to a comprehensive CAI system for clinical education. The system is designed to work on the mainframe for easiness of development, maintenance and extensions of the system. The present framework has been applied to the simulation of diagnostic process. The usefulness of the present system has been confirmed by specialists and students.

Computer-Assisted Instruction↗
PubMed1979

A computer program for simulating a distributed metabolic system. Distribution volumes in a simulated organism.

A metabolite or hormone is distributed with non-uniform concentration throughout some volume within an intact organism. Various methods involving radioactive tracers are used to estimate the total mass of the metabolite and its volume of distribution. The calculations of mass and volume are based on very simple models, and cannot usually be validated by measurements on the real animal. Hence we have developed a computer program for simulating a metabolic system with convective and diffusive transport. The tracer experiments can be simulated by solving the differential equations for convective diffusion by finite element methods. Thus the total metabolic mass and distribution volume can be both 'measured' and calculated by all the standard techniques. In this way some mathematical methods currently in general use can be seen to be patently incorrect, and others quite acceptable. The concept of a metabolic doublet was introduced, by analogy with an electrical dipole.

Biological Transport↗
PubMed1993

Simulation of stochastic micropopulation models--I. The SUMMERS simulation shell.

A generic, abstract model and the simulation shell based on it, both called SUMMERS, are used as a framework for the implementation of stochastic micropopulation models; in these, each individual is followed separately while moving through a sequence of states. The shell supports groups of interacting members, individual characteristics and multiple simultaneous activities. Stochastic decisions may be made using Monte Carlo rules. Keywords control the simulations and the reports generated. A sensitivity analysis utility allows assessment of the dependency of outcomes on model features. Extensive use has been made of software engineering techniques. Specializations of SUMMERS are described in subsequent papers.

Data Collection↗