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Comparative study of the safety and efficacy of liquid and dry monopolar electrocoagulation in experimental canine bleeding ulcers using computerized energy monitoring.

The drawbacks of monopolar electrocoagulation in the control of gastrointestinal bleeding include tissue adherence, unpredictable energy deposition, and a high incidence of tissue damage. Introduction of a conductive interfacial film of liquid between the monopolar electrode and the bleeding point during electrocoagulation may overcome these drawbacks. A prospective, controlled study was undertaken to evaluate the efficacy and safety of a monopolar electrode in liquid and dry modes when used to coagulate experimental canine bleeding ulcers. All experiments were done in open fashion via a gastrotomy with hand-held electrodes. An analog computer, which could be connected between a standard electrosurgical generator and the electrode, was designed and built to monitor and control the energy delivered to the tissue. Both liquid and dry electrodes were highly effective in stopping bleeding. The liquid electrode was found to be superior to the dry electrode in that tissue adherence was eliminated and energy deposition was more predictable, varying less with angle of incidence. The liquid electrode caused less macroscopic serosal damage and less full-thickness histologic damage if the total energy or number of pulses was limited; however, both caused microscopic full-thickness damage in one-half of the experimental ulcers treated, although no perforations occurred.

Animals↗

[Control system for the Sinus artificial heart].

The control system, type "Sinus", for an artificial heart is proposed. The use of servomechanisms in this system allows one to obtain pressure pneumopulses of any required form. The form of pneumopulses can be determined either by an external source, e. g. and analog computer, or by a built-in generator forming an electric control signal having one of three possible forms. The structural diagram of the type "Sinus" system and its brief technical specifications are given.

Animals↗

Evaluation of three dosage-prediction methods for initial in-hospital stabilization of warfarin therapy.

Three dosage-prediction methods for initial in-hospital stabilization of warfarin therapy were evaluated. Adult inpatients who had received warfarin sodium 10 mg daily for less than three days were eligible for the study. After receiving their third warfarin dose, patients were randomly assigned to have their warfarin dosages adjusted using one of three dosage-prediction methods: by analog computer (n = 31), linear regression (n = 22), or empiric dosing by the physician (n = 34). A prothrombin time (PT) ratio (patient PT divided by control PT) between 1.3 and 2.5 was considered to be in the therapeutic range. For patients who achieved a stable PT ratio (defined as a PT ratio between 1.3 and 2.5 that varied by less than 0.05 on two consecutive days or by less than 0.1 on three consecutive days without a dosage change) before discharge, the number of days (time to stabilization) from administration of the first warfarin dose to achievement of the warfarin dosage that produced a stable PT ratio (stabilization dosage) was compared. A total of 54 patients met the study criteria for a stable PT ratio before hospital discharge (analog computer, n = 20; linear regression, n = 15; empiric dosing, n = 19). The mean times to stabilization were 6.8 days in the analog-computer group, 7.3 days in the linear-regression group, and 8.4 days in the empiric-dosing group; these times were not significantly different. All 20 stabilized patients in the analog-computer group achieved a stable PT ratio by the fourth dosage prediction.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

A kinesiologic electromyography system for the computer-controlled analog and digital recording and processing of muscle action potentials of walking subjects.

A computer-controlled electromyography (EMG) System has been developed for the kinesiologic examination of orthopedic patients. A major objective in the design of the system was its convenient operation in the daily clinical routine. The EMG signals are transduced by specially constructed electrode-preamplifier units and filtered and further amplified in a cable distribution box fixed to the subject's belt or back. The amplified signals are transmitted to the stationary signal conditioning, display, and recording units by an easily tractable trailing cable guided in a ceiling rail. The test gait sequence is performed on a level walkway 14 m in length. A functional partition into periodically recurring gait is achieved either by foot-floor contact sensors or by optional goniometric measurements in the lower extremity. Patient safety is provided by an opto-coupling interface. The EMG signals are displayed on specially constructed large screen oscilloscopes for convenient real-time monitoring by the examiner. An analog recording is carried out by a multi-channel strip chart recorder. The digital recording and processing of the EMG signals and the control of the analog recording unit are implemented by an on-line system. This paper describes the main constructional features of the system and its components, discusses the basic problems involved in the digital recording and processing of EMG signals, and gives an outline of the digital processing mode employed so far in our electromyographical examination of orthopedic patients with various gait disorders.

Action Potentials↗

Movement of cholesterol in vitro in rat blood and quantitation of the exchange of free cholesterol between plasma and erythrocytes.

After administration of [4-(14)C]cholesterol to rats, blood was obtained and incubated for 6 hr or less. Incubation resulted in a net loss of erythrocyte cholesterol and, simultaneously, in an increase of esterified cholesterol in plasma and alpha-lipoproteins. Erythrocyte labile cholesterol was shown to be the sole precursor of esterified cholesterol. However, the relation between loss and esterification was not absolute. Loss of erythrocyte cholesterol could be inhibited without affecting esterification and vice versa. A catenary turnover model is proposed, which links in vivo erythrocyte labile cholesterol and plasma esterified cholesterol. Free cholesterol also exchanged between erythrocytes and lipoproteins. The topological model, as tested by analog computer, appears to be a bicompartmental system governed by nonconstant exchange fluxes. They are exponential functions of time and vary from 0.065 to 0.020 mg/hr/g of blood. The fitting of the curves obtained by analog computer analysis to the experimental curves requires esterification as described above. Variation of the exchange fluxes would be the consequence of lipoprotein structural alterations. If this is true, the initial value of the measured flux in vitro is identical with the in vivo value, and the turnover time of erythrocyte cholesterol is 9.2 hr. Initial exchange flux is not dependent on plasma cholesterol level or on the age of the rats, but it is temperature dependent. Addition of amphotericin B to the plasma does not modify exchange fluxes, but erythrocyte cholesterol loss is increased.

Amphotericin B↗

Quantitative radiocardiography in patients with patent ductus arteriosus.

Analytical models of the analog computer simulation method of radiocardiogram (RCG) were revised to obtain quantitative hemodynamic evaluations in patent ductus arteriosus (PDA). The theoretical and technical aspects are herein outlined, and the effects of clinical application discussed. Twenty-six patients with a left-to-right PDA shunt were studied by the revised RCG models, and the results were compared with oxymetric or echocardiographic data. Between RCG and oxymetry, the systemic blood flow (SBF) findings agreed well (r = 0.91), but in oxymetry, the pulmonary blood flow (PBF) findings were generally seen greater than in RCG (r = 0.81), and the oxymetric shunts appeared larger than in RCG (r = 0.75). This is because oxymetry cannot avoid the direct effects of the uneven partition of shunt flow to the lungs, whereas RCG can, in addition, measure the mean PBFs and SBFs. RCG may thus be said to be superior to oxymetry in assessing PDA shunts. Furthermore, RCG can estimate the mean left and right heart volumes (LHV and RHV) at the same time; the RCG LHV was found to correspond to the echocardiographic left ventricular end-diastolic volume (LVEDV) (r = 0.89). Moreover, the obtained relation between the RHV/LHV (Y) and the shunt ratio (X) proved to be the same that calculated theoretically (Y = -X + 1.0) in uncomplicated patients. Patients not presenting this relation may be assumed to suffer some condition complicating the PDA. In effect, the analog computer simulation method of RCG is a unique non-invasive means of obtaining quantitative analyses in PDA and in other congenital shunt diseases as well.

Adolescent↗

[Method for the continuous measurement of the phase relation between heart beat and respiration (author's transl)].

A simple method for the continuous analysis of the phase relation between heart beat and respiration is described. By means of an analog computer the timing of the R wave of the ECG within the respiratory cycle is graphically displayed. In contrast to other investigations, the onset of the inspiration is used as starting signal. The results obtained with the analog computer were completed by a digital computer program, which allowed in addition to calculate histograms of the events. In order to evaluate our method we used an analog model of two coupled oscillators. Responses obtained at different coupling characteristics were compared with measurements in four subjects. The results indicate a mutual interaction between heart action and respiration as cause of the coupling of these two systems.

Computers↗

Impaired oral reading in two atypical dyslexics: a comparison with a computational lexical-analogy model.

A computational model of reading was developed based upon the notion that the structural relationship between orthography and phonology is of greater importance than the dimension of semantics for the reading aloud of single words. Degradation of this model successfully simulated the reading performance of two patients with atypical acquired dyslexia. The first patient CAV, studied and described in the literature by Warrington in 1981, presented with unusual concrete word dyslexia, i.e., he had a category-specific reading deficit for concrete words compared with abstract words. The second patient BG is a phonological dyslexic who, although displaying a strong concreteness effect (concrete words read better than abstract words), was able to read functors individually perfectly well, a pattern that is rarely if ever seen. The computational model was used to generate a set of words for which it was predicted that BG would show no concreteness effect. The results of BG's reading of these words were consistent with this prediction, thereby providing greater support for the validity of the model. It is concluded that a computational approach that attempts not only to reproduce the core symptoms of the major varieties of acquired dyslexia but also to simulate clinical data from specific patients has much to contribute to the understanding of cognitive deficits and to the design of effective rehabilitation strategies.

Adult↗

Design of an actively controlled snow ski release binding.

A new electronic ski binding has been designed which may better protect skiers from lower extremity injuries. A four-step procedure for developing binding release criteria aimed at preventing specific injuries is outlined. Using simplified biomechanical models, the release criteria for tibia fracture in both torsion and flexion are derived. A binding design which embodies the derived release criteria is described. The binding consists of three subsystems: 1) a dynamometer, 2) an analog computer controller, and 3) an electromechanical release mechanism. The strain gage dynamometer directly measures torsion and bending moments between the boot and ski. An analog computer controlled processes dynamometer signals. Dual release mode capability is achieved by parallel solution of differential equations which model the leg in both medial-lateral rotation and flexion. When the model solution reaches a critical value, the controller actuates the release mechanism. The release mechanism incorporates a unique closed circuit hydraulic system which rigidly locks the boot to the ski until release. Laboratory tests on a prototype confirm that the computer-controlled binding prevents inadvertent release under noninjurious high-magnitude, short-duration loads but releases before quasi-static loads reach injurious levels.

Athletic Injuries↗

Some relations between action potential and resting potential of the lobster giant axon.

Experiments were performed to determine the quantitative relation existing between action potential and resting potential of the lobster giant axon. Resting potential changes were induced by either increasing the external potassium concentration or by reducing the external calcium concentration. For either treatment the action potential amplitude is proportional to the logarithm of the resting potential minus a constant. This constant is equivalent to the minimum resting potential at which a propagated spike is possible, and is larger for depolarization in low calcium than in high potassium. Thus the change in action potential per unit change in resting potential is greater in low external calcium than in high external potassium. Analog computer solutions to the Hodgkin-Huxley equations for squid axon membrane potentials show that, if the initial conditions are properly specified, the action potential is proportional to the logarithm of the potassium potential minus a constant. The experimental results and the analog computations suggest that reducing external calcium produces changes in the invertebrate axon that cannot be accounted for solely on the basis of alterations in the potassium potential.

Action Potentials↗

[Computerization and robotics in medical practice].

The article gives the outlines of all principles used in computing included the non-electrical and analog computers and the artifical intelligence followed by citing examples as well. The principles and medical utilization of virtual reality are also mentioned. There are discussed: surgical planning, image guided surgery, robotic surgery, telepresence and telesurgery, and telemedicine implemented partially via Internet.

Computer Communication Networks↗