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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 21 (1983), S. 119-127 
    ISSN: 1741-0444
    Keywords: Compartmental models ; Control ; Least-squares fitting ; Muscle relaxants ; Parameter estimation ; Pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To implement a feedback control system to achieve satisfactory muscle relaxation during surgical procedures, a mathematical formalism, based on linear compartmental theory, is derived to model the input/output response between the dosage of a drug administered and its neuromuscular effect as measured by the train-of-four (T4) ratio twitch response. The effect (T4 ratio) is related directly to the dosage schedule, and no attempt is made to include the plasma concentration of the neuromuscular blocking drug in the formalism. The neuromuscular blocking data of 24 patients, in whom the muscle relaxant d-tubocurarine (curare) was used, were fitted using a nonlinear least-squares data fitting routine. The number of compartments necessary to fit the data for each patient was determined using the general linear test. In all but three cases a biexponential model was sufficient to fit the data. Simulation studies also show that a biexponential model gives satisfactory control even for those patients for whom a triexponential model was necessary to fit the data. Further simulation shows that because of interindividual variation the application of adaptive control techniques will be needed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 21 (1983), S. 710-717 
    ISSN: 1741-0444
    Keywords: Control ; Identification ; Least squares ; Muscle relaxants ; Simulation ; State estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A self-tuning algorithm is presented for the online control of muscle relaxation. Although some patient parameters were fixed at a mean value determined by offline analysis of patient data, certain parameters have been explicitly identified online. In addition the patient states are estimated and are used by a novel controller to bring an unrelaxed patient to some desired level of paralysis and maintain it. Simulations show that a twitch depression of 80% can be achieved in less than 20 min using d-tubocurarine without excessive overdosage.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 23 (1985), S. 547-555 
    ISSN: 1741-0444
    Keywords: Automatic control ; Data logging ; Drug pump ; Measurement ; Microcomputer ; Muscle relaxants ; Muscle response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The paper describes the design and performance of a microcomputer-based system to measure and control the level of muscle relaxation during surgical procedures. A measurement system feeds the twitch response to a train-of-four stimulation pulses into a microcomputer system. The microcomputer determines the level of muscle relaxation and then calculates, according to a specified control algorithm, the minimum amount of drug necessary to achieve adequate relaxation as rapidly as possible. The drug is administered automatically to the patient in the form of bolus injections by a motordriven syringe unit on instruction from the microcomputer. This controller system has been used in 42 clinical trials using d-tubocurarine and has proved to be capable of successfully controlling muscle relaxation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 23 (1985), S. 556-564 
    ISSN: 1741-0444
    Keywords: Control ; Least squares ; Muscle relaxants ; Neuromuscular blockade ; Parameter estimation ; Simulation ; State estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract An existing algorithm designed to control d-tubocurarine-induced muscle relaxation in humans has been evaluated in 38 clinical trials on patients undergoing upper and lower abdominal surgery. The data captured during these trials were used to perform offline analysis of the algorithm reported on here, by which the correct functioning of the algorthm was established and its efficacy rated. It is shown that, for practical purposes, the average controller performance is close to the theoretical limit which can be achieved for this drug. The use of online parameter estimation makes precise initialisation of the controller less critical than would be the case with a fixed control low. In the trials undertaken, an average time of 12 min was needed to reach the chosen set point and excessive overshoot was avoided in every case. With a setpoint for the single twitch response of 20 per cent of the control height, the average drug consumption for the first hour of operation was 0·38 mg kg−1.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1983), S. 596-600 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two chemical ionization mass spectrometric methods were developed for direct determination of deuterium in water in the range of 0.0-0.6% 2H2O. One of them utilizes the batch inlet system, methane as the reagent gas, and the peak matching device of a magnetic sector mass spectrometer. The second one utilizes the directly-coupled gas chromatograph of a quadrupole mass spectrometer and computer control for ion selection and data processing. In this method the water itself serves as the reagent gas. The deuterium concentration is calculated from the ratio of ion intensities at m/z 20 (2HH2O+) and m/z 19 (H3O+). We have used these methods to determine total body water in 350 human subjects, which entailed making 900 measurements over a period of four years. Comparisons were made in 200 subjects of our results with those obtained by the creatinine method. No significant differences were found.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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