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At least 19 recordsLinked to original sources
PubMed1976

Radiographic aspects of permanent cardiac pacemakers.

Radiographic findings in patients with permanent cardiac pacemakers are described, and recent advances in pulse generator and lead design are presented. Emphasis is placed on those findings which are related to (a) complications of cardiac pacing, (b) radiographic configurations of new energy sources and lead/electrode systems, and (c) a new system of pulse generator identification.

Bioelectric Energy Sources↗
PubMed1976

Rechargeable silver-modified mercuric oxide-zinc cell for cardiac pacemakers.

Tests were conducted on rechargeable mercury-zinc pacemaker batteries under simulated and actual biologic conditions, using a variety of discharge rates and charging schedules. In tests on 96 cells at a 6.4 milliampere (ma) discharge, recharging once every 15 months of simulated pacing at a 25 microampere (mua) drain, the earliest cell failure occurred after an equivalent of 50 years of pacing. The mean pacing equivalent for all 96 cells was more than 140 years. In 6.4 ma discharge tests on 24 cells, recharging once every 8 days of simulated pacing, only 1 cell in 24 failed after an equivalent of more than 500 years of pacing (actual time 2 years). In tests on 13 cells pacing at a 200 mua drain without recharging, the simulated mean duration of pacing before total discharge was 4.8 years. Seven other cells at a 200 mua drain with periodic recharging continue to function normally after more than 7 years of actual time, simulating 56 years of pacing at a 25 mua drain. Cardiac pacemakers using the rechargeable mercury-zinc cell have been implanted in animals for more than 2 1/2 years and in patients for more than 1 year with all units continuing to function satisfactorily. It has been demonstrated unequivocally that a rechargeable mercury-zinc pacemaker will function continuously for more than 4 years without recharging and that periodic recharging will extend pacing life far beyond that predicted for lithium and nuclear primary power sources.

Animals↗
PubMed1991

Estimates of neuronal current distributions.

The main purpose of measurements of the magnetic field produced by cerebral electrical activity is to locate this activity or to determine its distribution in the brain. In this paper, methods to locate or otherwise characterize source currents in the brain are briefly discussed. It is emphasized that the optimal source estimation method depends crucially on the availability of prior information and on the questions one wants to resolve with the measurements.

Bioelectric Energy Sources↗
PubMed1991

Multipole expansions in the representation of current sources.

After obtaining the measured magnetic field or its components in the form of an isofield map one has to decide which approximation to use in solving the inverse problem. A single current dipole as an equivalent current source is often used. It will be shown when this approximation fails and one possible way to improve the equivalent source description. The expansion of current multipoles is discussed up to the second order. The localization of an equivalent current source in this case is considered. The application of this type of expansion is analysed and discussed.

Bioelectric Energy Sources↗
PubMed1978

[Recent progress in energy sources and in technology of electronic circuits (author's transl)].

Since 1957, when the first implantable pacemaker was developed, the performances of cardiac pacemakers have enormously improved. The paper describes the recent progress in the field of energy sources, technology and circuit solutions. The improvements achieved up to now have extended the mean life-time of an implantable pacemaker from about 30 months up to more than 6 years, while some pacemakers with programming capabilities are available and pacemakers with self-adapting capabilities to the individual hemodynamic needs are in the stage of advanced development.

Bioelectric Energy Sources↗
PubMed1977

An implantable electromagnetic sound source for speech production.

Our goal is to provide laryngectomized cancer patients with a method of speech rehabilitation as an alternative to esophageal speech when required. With the cooperation of otolaryngologists, biomedical engineers, and speech therapists, an implantable electromagnetic sound source for voice production has been produced. It is biocompatible, durable, and functional in animal experimentation. A small, carefully selected clinical trial will soon begin.

Animals↗
PubMed1978

Current status of pacemaker power sources.

After years during which pacers of very similar design and capabilities were provided by a small number of manufactures, many different lithium, halogen, rechargeable, and nuclear power sources are now available. The variety of chemistries, methods of construction, and sealing techniques used in the batteries of the different manufacturers is almost unlimited. This has made it necessary for physicians who implant and follow pacer to acquire a general knowledge of the field if they are to make an informed choice of pacemaker power source for implantation and if they are to manage recalls with a minimum of patient and physician trauma. More experience is required before it can be definitely determined which of the new pacer power sources will prove superior, but when coupled with well-designed, hermetically sealed pulse generators, all are capable of providing continuous pacing for at least 5 years and the 10-year pacemaker is now a probability.

Animals↗
PubMed1975

Runaway pacemaker in seven patients: a persisting problem.

Runaway pacemaker has been encountered in 7 patients during the past 7 years at the Texas Heart Institute. In this series, 4 patients with fixed-rate pacemakers experienced pacemaker arrhythmias because of battery depletion, and 3 had arrhythmias because of component failure. Battery deterioration was heralded by an increase in cardiac rate. Ventricular tachycardia, rapidly followed by ventricular fibrillation, occurred in 2 patients. Prompt surgical exteriorization of the failing pulse generator and connection to an external pacemaker resulted in prompt recovery in all patients. Elective generator change should be performed routinely after 24 to 30 months unless reliable serial observations of ventricular rates can be attained. This at least will reduce the lethal complications attributed to battery exhaustion. Increasing developments in the design of generators and sources of power, as well as data from pacemaker clinic follow-up and telephone pulse transmittal, are expected to decrease the frequency of this complication.

Adult↗
PubMed1991

Mathematical aspects of source modeling.

This paper reviews the properties of the major source models which are used in the analysis of observed bioelectric signals in general, and of evoked potentials in particular. The interpretation of such models demands the solution of an associated inverse problem. Emphasis is laid on the possibility of imposing such constraints on the model which render stable inverse solutions and yet allow a physiological interpretation. The nature of this paper is tutorial.

Bioelectric Energy Sources↗
PubMed1991

Cortical responses to changes in auditory stimuli. Magnetoencephalographic studies.

Any infrequent change ("deviant") in the parameters of a repetitive auditory stimulus ("standard") elicits both in electro- and magnetoencephalogram a specific "mismatch response". Identical infrequent stimuli do not elicit it; the presence of standards is necessary. Magnetic measurements have shown that the mismatch response has its neural source at the supratemporal auditory cortex. This source is about 10 mm anterior to the source of the N100m deflection, suggesting that these two waves are generated at different cytoarchitectonic areas. It is suggested here that the mismatch response reflects the activity in "change detectors", whereas activity in auditory feature maps underlies the N100m deflection. A model is proposed where the activity from feature maps converges on change detectors; the presence of a mismatch response is suggested to indicate that feature maps have been previously activated.

Acoustic Stimulation↗
PubMed1977

A focus for biophysical research in energy problems.

There is widespread agreement that solar energy is the most promising long-range energy source. However, contemporary technology for bulk energy storage is so primitive that full use of the inevitably erratic solar energy flux is severely limited. Biological systems have perfected methods of storing solar energy for later use in periods of darkness, and it is argued in this symposium presentation that there are many frontiers in biophysics related to the solar energy storage problem. Moreover, the conceivable biological storage systems span a wide range of technology, with appropriate applications in societies of widely varying degrees of industrial development. Use of biological systems to produce hydrogen from solar energy may be among the most versatile of these applications. The entire problem of bioconversion of solar energy presents an excellent example of how the needs for basic scientific understanding and application engineering can be very tightly interwoven.

Bacteria↗
PubMedDate not supplied

A new skeletal muscle linear-pull energy convertor as a power source for prosthetic circulatory support devices [corrected].

Previous studies show that stimulated skeletal muscle wrapped around the heart or a blood pumping pouch can provide partial circulatory assistance. However, skeletal muscle is accustomed to pulling in direct tension, and power obtained from using the muscle in wraparound configurations is very inefficient. Therefore we have developed a new skeletal muscle-powered, linear-pull energy convertor for powering a wide range of implanted devices, including circulatory support blood pumps such as counterpulsation devices or complete prosthetic ventricles. This energy convertor system is powered by a skeletal muscle such as the latissimus dorsi, which is stimulated with a pulse generator. With the muscle left intact and in situ as much as possible, its insertion at the humerus is removed and reattached to a small-cylinder hydraulic energy convertor that is firmly attached to the ribs. Mechanical force in direct tension from the muscle is converted to high-pressure, low displacement; hydraulic energy (at approximately 200 psi). The output of this hydraulic energy convertor is connected by a small-diameter tube to a hydraulic actuator to drive the pusher plate of an implantable ventricular assist device located in the thoracic cavity or abdomen or another suitable blood pump. Preliminary in vitro tests from an engineering model of the Thoratec muscle-powered ventricular assist device show flow outputs of 5.2 L/min at a mean arterial pressure of 99 mm Hg. The muscle-powered ventricular assist device is a specific application designed to provide completely implantable circulatory support as an alternative to heart transplantation. It will enable patients to experience a quality of life free from batteries and the electrical power-conditioning hardware required with electromechanical systems.

Bioelectric Energy Sources↗