Some aspects of the generation of evoked otoacoustic emissions (EOAEs) are discussed. This signal is generated within the periphery of the auditory organ and is shown to contain responses from localized regions of the...
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Some aspects of the generation of evoked otoacoustic emissions (EOAEs) are discussed. This signal is generated within the periphery of the auditory organ and is shown to contain responses from localized regions of the cochlea. From deconvolution of the responses from normal hearing subjects it appears that EOAEs are linearly related to the input stimulus, for acoustic impulses (clicks) and sinusoidal bursts, within the same ear. Short-time Fourier analysis is shown to reveal the composite time structure of these signals: the dominant frequency content and post-stimulus times are discussed.
To extract main aspects of the coupling between a ventricle and its arterial load simple analog models may be used: the input impedance of the arterial systems may be modelled by resistors, compliance and inductance i...
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To extract main aspects of the coupling between a ventricle and its arterial load simple analog models may be used: the input impedance of the arterial systems may be modelled by resistors, compliance and inductance in advanced or simple lumped 3 or 4 component models;the heart, since the instantaneous pressures of the different compartments essentially depend on their instantaneous volumes, may be modelled by time-varying capacitors. The components may be connected by uni-directional valves at the appropriate sites and the whole system programmed and solved by computer. Heart models incorporating ventricular interaction across the septal wall indicate that energy produced in the right ventricular free wall is partly transferred to the left ventricle.
Self-tuning control has been used for obtaining blood pressure regulation in over 100 patients undergoing various types of surgery. The generalized minimum-variance approach of D.W. Clarke and P.J. Gawthrop, with recu...
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Self-tuning control has been used for obtaining blood pressure regulation in over 100 patients undergoing various types of surgery. The generalized minimum-variance approach of D.W. Clarke and P.J. Gawthrop, with recursive least-squares type estimation of controller parameters was used. A simple introduction to the control method is given. Some topics concerning parameter estimation are discussed. Some suggestions for improved adaptivity and robust controller design are given. Practical details of the method of implementation and the results obtained from extensive clinical trails are given.
Medical diagnosis can be modelled in terms of the classical notions of abduction, deduction and induction. Abduction is making a preliminary guess that allows to establish a set of plausible diagnostic hypotheses, fol...
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Medical diagnosis can be modelled in terms of the classical notions of abduction, deduction and induction. Abduction is making a preliminary guess that allows to establish a set of plausible diagnostic hypotheses, followed by deduction for exploring their consequences and by induction for testing them with available patient data. Such a description of diagnostic reasoning at a knowledge level helps the construction of an expert systems by fashioning the adopted expert system building tool to reflect the structure of the problem rather than force the problem to the tool. To this aim reasoning strategies need to be represented abstractly, separately from medical facts and relations, so making the design more transparent and explainable. This paper describes how an already developed system, ANEMIA, able to provide a rather good diagnostic performance, has been re-implemented taking into account the above mentioned design criteria.
Various typical wave shapes of the radial artery pulse accumulated from experience have been artificially classified in graphical spectra which are used as initial training samples to train a microcomputer in establis...
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Various typical wave shapes of the radial artery pulse accumulated from experience have been artificially classified in graphical spectra which are used as initial training samples to train a microcomputer in establishing basic structural classes by modelling identification. A feature space of the classes is then created. A discriminant function is also automatically generated to form decision bounds for the pulse recognition. Self-learning approach has been employed for recreating the new decision bounds or re-designing the basic structural classes to approach the precise pulse recognition. A microcomputer-based real-time method for analysing and recognizing the pulse waves in radial artery is now presented, and it has been tested and will be applied to the diagnosis for the traditional chinese medical services.
This paper describes a closed-loop computer based system for the controlled infusion of the inotrope/vasopressor drug dopamine in seriously ill patients suffering from hypotension. The system has been developed in the...
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This paper describes a closed-loop computer based system for the controlled infusion of the inotrope/vasopressor drug dopamine in seriously ill patients suffering from hypotension. The system has been developed in the Intensive Care Unit of the Royal Melbourne Hospital in association with the Department of Electrical and Electronic Engineering, University of Melbourne. The system uses a model reference adaptive control strategy to handle variations in sensitivity. control decisions are based on a 'wait and see' policy and control steps are determined using a lookup table based on manual control protocols. This approach was used to facilitate the introduction of the new technology in a ward where the nursing staff had had no previous experience in the use of the computer systems.
Patient driven continuous arteriovenous haemofiltration is emerging as a useful technology for the management of acute renal failure and for fluid overload in the oligo-anuric patient. The isotonic fluid loss provides...
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Patient driven continuous arteriovenous haemofiltration is emerging as a useful technology for the management of acute renal failure and for fluid overload in the oligo-anuric patient. The isotonic fluid loss provides convective rather than diffusive clearance of metabolic wastes with gains in cardiovascular stability. The requirement for isotonic fluid replacement is demanding. This paper explores a new technique of control of fluid replacement. The conventional isovolaemic replacement (primary control) is modulated by a secondary control based on quasi-continuous measurement of a mean systematic filling pressure analogue. Haemofiltration forms a useful basis for the exploration of this technique which has promise as a generalised basis for automatic volume control in critically ill patients.
The influence of the sequence of cardiac contractions on cardiac performance criteria like stroke volume or pressure amplitude was examined in patients with atrial fibrillation. For comparison the behavior of an in vi...
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The influence of the sequence of cardiac contractions on cardiac performance criteria like stroke volume or pressure amplitude was examined in patients with atrial fibrillation. For comparison the behavior of an in vitro system of guinea pig papillary muscle was studied during pseudorandom sequence electric stimulation. For the analysis methods of correlation and regression analysis and, particularly, methods of time series analysis were used. We found that in patients as well as in the isolated papillary muscle preparation properties of 4 to 6 preceding contractions have an effect on the succeeding contraction.
In this work a linear time-varying model has been developed for studying glucose kinetics in non-steady state during glucose clamp studies. Tracer and tracee dynamics are described with a two input-two output model wi...
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In this work a linear time-varying model has been developed for studying glucose kinetics in non-steady state during glucose clamp studies. Tracer and tracee dynamics are described with a two input-two output model with two compartments. Glucose production is modeled as a parametrized function of time. Parameters have been estimated by least squares using data from dog experiments. The adequacy of the model is extensively discussed, and the reliability of classical analyses is comparatively evaluated.
In contrast to 'weightless' radioactive tracers, stable isotope tracers have non-negligible mass, are naturally present in the system and the measured variable is a ratio of two isotopic species. These feature...
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In contrast to 'weightless' radioactive tracers, stable isotope tracers have non-negligible mass, are naturally present in the system and the measured variable is a ratio of two isotopic species. These features have to be explicitely taken into account when kinetic isotopic tracer data are analyzed. We focus here on compartmental models for the interpretation of stable isotope tracer data. Assumptions and modeling techniques are discussed for the general nonlinear, the linearized and the linear case.
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