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Biomedical subjects

O Wigertz

Publications and source records attributed to O Wigertz.

At least 55 records · Page 3Linked to original sources
PubMed1989

Knowledge base design for decision support in respirator therapy.

A knowledge base is built for decision support applied to respirator therapy (the KUSIVAR project). The knowledge representation is object-oriented using frames to store multiple forms of knowledge: variable descriptions, transformation tables, rules and mathematical models. The system is data-driven, generating and displaying advice automatically triggered by changes in data from the respirator and the patient. The inferenceing mechanism is forward-chaining i.e. a rule is evaluated as soon as it's condition is satisfied. Temporal aspects of the reasoning are represented by a number of mechanisms, among others limited validity times for data, trend analysis and mathematical models. The knowledge base is organized according to disease groups and decision situation which simplifies knowledge acquisition and improves response times since it enables the system to focus on a limited set of rules in each situation. To test the feasibility of the system design a prototype has been built using Knowledge Engineering Environment (KEE) from Intellicorp on an Explorer workstation from Unisys. The production system, which is interfaced to a Siemens Elema Servo Ventilator 900C, is currently being implemented under the Microsoft Windows multitasking environment on a microcomputer based on an Intel 80386 processor.

Decision Support Techniques↗
PubMed1989

Teaching medical informatics to biomedical engineering students: experiences over 15 years.

The Departments of Biomedical Engineering and Medical Informatics at Linköping University in Sweden were established in 1972-1973. The main purpose was to develop and offer courses in medicine, biomedical engineering and medical informatics to students in electrical engineering and computer science, for a specialization in biomedical engineering and medical informatics. The courses total about 400 hours of scheduled study in the subjects of basic cell biology, basic medicine (terminology, anatomy, physiology), biomedical engineering and medical informatics. Laboratory applications of medical computing are mainly taught in biomedical engineering courses, whereas clinical information systems, knowledge based decision support and computer science aspects are included within the medical informatics courses.

Biomedical Engineering↗
PubMed1989

A knowledge-based system for data analysis and interpretation.

Traditionally, statistical packages are employed to derive or infer facts about a Universe of Discourse through data analysis and interpretation. It is analysis that serves to transform data into information. Statistical packages provide the users with relatively easy-to-use and powerful mechanics of data analysis, but up to now they do not provide much help with the design and strategies of the analysis. As such, there is a risk of misuse of these packages by statistically inexperienced users. We propose the use of knowledge-based interfaces to support this category of users in statistical evaluations. This paper discusses our experiences from the implementation of a knowledge-based system called MAXITAB. It provides guidance in the processes of data analysis and interpretation and has been programmed as an interface to the statistical package MINITAB.

Data Interpretation, Statistical↗
PubMed1989

The data dictionary--a controlled vocabulary for integrating clinical databases and medical knowledge bases.

The medical information systems of the future will probably include the entire medical record as well as a knowledge base, providing decision support for the physician during patient care. Data dictionaries will play an important role in integrating the medical knowledge bases with the clinical databases. This article presents an infological data model of such an integrated medical information system. Medical events, medical terms, and medical facts are the basic concepts that constitute the model. To allow the transfer of information and knowledge between systems, the data dictionary should be organized with regard to several common classification schemes of medical nomenclature.

Database Management Systems↗
PubMed1988

Computer simulation of cardiac pacing.

A mathematical model of the cardiac conduction system, including external pacemakers, has been developed. The heart is modeled as a network in which the impulse propagation is described by differential equations; several arrhythmia-generating mechanisms, such as modulated parasystole, reflection, macro and micro re-entry and block, can be simulated. Different kinds of pacemaker modes have been incorporated in the model, thus making it possible to simulate the interaction between the heart and the pacemaker. The model can be tuned by the user according to electrophysiological data so that pacemaker programs can be tested under different underlying conditions. During a simulation, the program generates ECG signals and pacemaker diagnostic diagrams. This model can be used for training and testing, and also as a support system when searching for the optimal pacing therapy for a particular patient.

Computer Simulation↗
PubMed1987

Computer simulation of cardiac arrhythmias.

A mathematical model of the cardiac conduction system has been developed. The mechanisms of cardiac arrhythmias are described mathematically, and the heart is modeled as a network, where each element is defined by a unique set of time parameters from the action potential. The mathematical description is separated from the network structure, thus making it possible to run the model with different network sizes. Simulated ECG curves are produced in each case. This model is especially suited for rhythm studies, and a variety of different cardiac arrhythmia mechanisms has been simulated such as reentry, reflection, modulated parasystole, and different kinds of block.

Action Potentials↗
PubMed1986

Ramp-function work test suitable for automatic computation.

Heart rate (HR) response to step-function and ramp-function (20 W/min) work tests was compared in 12 healthy subjects. For a given power output (P), HR was substantially lower in the ramp tests. The HR difference increased with power output and increasing difference in work time between the test types. The HR difference can be explained in terms of a drift component (which accounts for 1/3 of the difference) and a lag component (2/3). As a consequence of the HR differences, P for a given HR is higher in ramp tests. Work capacity expressed, for example as P170, can be determined in ramp tests, and the result can be translated to step-function P170. The precision in this translation is markedly improved if a steady-state period is incorporated into the ramp test.

Adolescent↗
PubMed1973

Cardiorespiratory and metabolic costs of continuous and intermittent exercise in man.

1. Cardiorespiratory and metabolic responses to paired patterns of continuous and intermittent exercise with the same average power output were studied in eight men. Heart rate, ventilation and pulmonary gas exchange were measured during the different patterns of exercise performed on a cycle ergometer. The recovery oxygen volume was measured over 30 min of loadless pedalling. Needle biopsy samples of the vastus lateralis muscle were taken before, during and after completion of the exercise for measurement of muscle metabolites.2. Heart rate, ventilation, oxygen intake, respiratory exchange ratio, and blood lactate concentration were generally higher with intermittent compared with continuous exercise as were the accumulated totals for heart beats, ventilation and oxygen intake. Muscle biopsy samples tended to have higher lactate and lower phosphocreatine contents in intermittent exercise. The lactate concentration in muscle and blood water was the same during loadless pedalling before exercise but was significantly higher in muscle than blood during exercise. This concentration gradient was larger in intermittent than in continuous exercise.3. Work efficiency, calculated from the total oxygen cost of work in excess of a loadless pedalling control, was significantly lower in intermittent exercise. The explanation is thought to be connected with the observation that when the work was performed at a high rate in short bursts a large part of the oxidative recovery took place after the contraction during the rest periods, whereas in the low intensity continuous exercise the oxygen was mainly utilized while the work was being performed. This indicates that for part of the time in the intermittent exercise the muscle was working under anaerobic conditions. Although the possibility exists that the efficiency of resynthesis of phosphagen may be reduced in this form of activity, it is more likely that the result described is due to the greater amount of lactate formed in the intermittent exercise.

Adenosine Triphosphate↗