Jerry H. Gold

An Inductively Coupled RF System for the Transmission of 1 kW of Power Through the Skin

In systems in which inductive coupling between a pancake-shaped coil on the surface of the body and a similar coil within the body is utilized for the transport of electromagnetic energy, the minimization of temperature rise in the tissue is intimately related to the achievement of minimum losses in the region of the implanted coil. A detailed theoretical analysis indicates the design considerations for achieving minimum losses in the vicinity of the implanted coil and predicts relevant internal losses of about one-half of 1 percent of the transported power. Experimental verification of theoretical expectations has involved an operating frequency of 428 kHz for the transmission of 1 kW of power between a simple water-cooled coil on the surface of the chest and a coil implanted in the chest wall of a dog. A maximum tissue temperature of 103.5° F was observed. Since 1-h operation per day at the 1-kW level would supply the anticipated energy requirements for a patient with an artificial heart, the system may find application in the charging of internal energy storage units of artificial heart systems.

Transthoracic Ventricular Defibrillation in the 100 kg Calf with Symmetrical One-Cycle Bidirectional Rectangular Wave Stimuli

From 2760 fibrillation-defibrillation episodes in 100 kg calves, the effectiveness of reversing ventricular fibrillation of 30 s duration with symmetrical one-cycle bidirectional rectangular-wave shocks was determined. Pulse widths of 0.5-64 ms, pulse amplitudes of 35,50,70,100, and 140 A, and delivered pulse energies in the 93-1567 J range were employed in a primary study involving 39 animals. Families of curves relating percent successful defibrillation and the time intervals required for the return ofventricular activity and of normal sinus rhythm in the postdefibrillation electrocardiograms to the parameters of the delivered shocks were derived. In an eight-calf supplementary study involving 91-110 kg animals, the effectiveness of 50 A, 10 ms bidirectional rectangular wave shocks and 70 A, 6 ms unidirectional rectangular wave shocks were stringently compared by interlacing fibrillation-defibrillation episodes involving 120 bidirectional and 120 unidirectional shocks. When combined with previously published data for unidirectional wave shocks in 100 kg calves, our data suggest that pulse amplitude and pulse width specifications are considerably broader for successful bidirectional rectangular wave shocks than for unidirectional rectangular wave shocks, and that appreciably higher first-shock successful defibrillation (96-99 percent) can be achieved with bidirectional waveforms

Ventricular defibrillation in the dog using implanted and partially implanted electrode systems.

Abstract Two totally implanted and two partially implanted electrode systems were studied in 2,100 fibrillation-defibrillation episodes in large anesthetized dogs. In one of the totally implanted systems, two metal disks, 7.6 cm in diameter, were implanted between the pectoralis major muscle and the rib cage, with the right electrode high on the chest and slightly to the right of midline and the left electrode over the apex of the heart. In the other totally implanted system, a unipolar catheter electrode positioned in the right atrium and superior vena cava was used together with a 7.6 cm disk electrode over the apex of the heart. In the partially implanted systems, a unipolar catheter electrode in the right atrium and superior vena cava was used together with either a 7.6 cm disk electrode or a 6.3 by 20.3 cm rectangular sheet electrode placed on the surface of the chest over the apex of the heart. Four types of unidirectional shocks were used in evaluating the twin disk system. Nine types of shocks were used with systems involving the catheter electrode. Derived curves indicate that the 90 percent level of successful defibrillation is achieved with 38 joules on the day of implantation and 54 joules 32 weeks after implantation for the twin disk system, 12 joules on the day of implantation and 19 joules 33 weeks after implantation for the catheter-internal disk system, 15 joules for the catheter-external disk system and 24 joules for the catheter-external sheet system.

Transthoracic Ventricular Defibrillation in the 100 kg Calf with Untruncated and Truncated Exponential Stimuli

The effectiveness in reversing ventricular fibrillation of 30 s duration of 50 untruncated and truncated exponential waveforms was studied in 6000 fibrillation-defibrillation episodes in 100 kg calves. The study employed waveforms which could be generated with nominal stored energy levels (in the basic capacitor-switch sense) of 220, 440, and 660 J and initial current levels of 50, 70, 100, 140, and 200 A. Fifty A waveforms having a time constant of decay of 10 ms were truncated at 15 and 30 A while those having time constants of 20 and 30 ms were truncated at 15, 30, and 45 A. Seventy A waveforms having time constants of 5, 10, and 15 ms were untruncated or truncated at 15, 30, and 45 A. One hundred A waveforms having time constants of 2.5, 5.0, and 7.5 ms were untruncated or truncated at 15, 30, and 45 A. One hundred forty A waveforms having time constants of 1.25, 2.50, and 3.75 ms were untruncated or truncated at 15, 30, and 45 A. Two hundred A waveforms having time constants of 0.63, 1.25, and 1.88 ms were untruncated or truncated at 45 A. We used 75 animals in the study.

Ultrahigh-energy hydrogen thyratron/SCR bidirectional waveform defibrillator

Presented here is a description of an ultrahigh-energy hydrogen thyratron/SCR bidirectional waveform research defibrillator having a sinusoidal voltage source for inducing fibrillation and three pulse generators for generating defibrillatory waveforms. The first pulse generator uses an 18 kJ capacitor bank at 0·8, 1·6 or 2·4 kV discharged through the chest by two series-connected silicon-controlled rectifiers (SCRs). Two other series-connected SCRs in parallel with the bank terminate the discharge. The second pulse generator uses an 18 kJ bank at 5, 10 or 15 kV. Ceramic-enveloped hydrogen thyratrons in series with the chest initiate the discharge, and in parallel with the bank terminate the discharge. The third pulse generator supplies a reverse-current pulse when used with either the first or second pulse generators to produce bidirectional waveforms. An 18 kJ bank at 2·5, 5 or 10 kV is discharged by an SCR chain in series with the chest. The discharge is terminated by an SCR chain in parallel with the bank. Symmetrical bidirectional rectangular, truncated exponential, and untruncated exponential waveforms are generated by the first and third pulse generators with their respective banks at 2·4 and 2·5 kV, the second and third pulse generators with their banks at 5 kV, or the second and third pulse generators with their banks at 10 kV. The full energy-storage capabilities of the capacitor banks can be used in the first two arrangements; usable energy storage in the third arrangement is limited to about 10 kJ per bank.

The relationship between the electric field in a semi-infinite conductive region and the power input to a circular coil on or above the surface.

The electric field induced in a semi-infinite isotropic homogeneous region by a time-varying current in a multi-turn circular coil positioned on or above the surface of the region is related to the power supplied to the coil. In this derivation, the electric field (normalised in terms of the conductivity of the region, the distance of the field point from the surface and the applied power) is expressed as a function of the ratios of the linear dimensions which characterise the geometry of the system to the distance of the field point from the surface and of a quantity which involves frequency, the Q factor of the coil, conductivity of the region, and the distance of the field point from the surface.SommaireLe champ électique dans une région homogène isotropique semi-illimitée induit par un courant de durée variable dans une bobine circulaire multitours située à la surface au dessus de la zone dépend de la puissance fournie à la bobine. Dans cette dérivation, le champ électrique (normalisé en termes de conductivité de la zone, de distance du lieu du champ de la surface et de la puissance imposée) est exprimé sous forme de fonction des rappots des dimensions linéaires qui caractérisent la géométrie du système, à la distance du point du champ de la surface et de la quantité comprenant la fréquence, du facteur Q de la bobine, de la conductivité de la zone et de la distance du point du champ de la surface.ZusammenfassungEs wird das elektrische Feld, das in einem halb unendlichen isotropischen, homogenen Bereich durch einen zeitabhängigen Strom in einer auf oder über der Bereichsfläche angebrachten runden Spule mit mehreren Wicklungen induziert, wird, zu der dieser Spule zugeführten Leistung in Bezug gesetzt.In dieser Ableitung wird das elektrische Feld (das hinsichtlich der Leitfähigkeit des Bereichs, des Abstands des Feldpunktes von der Oberfläche und der zugeführeten Leistung normalisiert ist) als eine Funktion der Verhältnisse der linearen Abmessungen ausgedrückt, die die Geometrie des Systems zur Entfernung des Feldpunktes von der Oberfläche und die Geometrie einer Menge bestimmen, in der Frequenz, der Q-Faktor der Spule, die Leitfähigkeit des Bereichs und der Abstand des Feldpunktes von der Oberfläche enthalten sind.

Localized DC Field Produced by Diode Implanted in Isotropic Homogeneous Medium and Exposed to Uniform RF Field

Minimally invasive selective stimulation of biological tissue within the body can be achieved by implanting a small rectifying diode and then applying an RF field by means of electrodes or a coil on or near the surface of the body. A theoretical analysis of a simplified model consisting of a cylindrically symmetrical unit implanted in an isotropic homogeneous medium of conductivity ?and permittivity ? and exposed to a uniform RF field relates the dc component of electrode current to the detailed geometry of the electrodes of the implanted unit and to the amplitude of the applied field.

Electrolytic Tank Solution of Electric Field Associated with Two Circular Disks on the Surface of an Isotropic Homogeneous Medium

The electric field associated with two disks on the surface of a semi-infinite isotropic homogeneous medium is found on a plane perpendicular to the disks and passing through their centers. To an accuracy which is primarily determined by the finite dimensions of the electrolytic tank, the solution is presented as families of curves. In this presentation, the magnitude of the electric field (normalized in terms of the distance of the field point from the surface, conductivity of the medium, and applied power) and the angular orientation of the field vector are plotted as functions of the ratios of the linear dimensions which characterize the geometry of the system to the distance of the field point from the surface.

Transthoracic defibrillation in 100-kg calves with sequentially applied pulses

The effectiveness of up to five 50-A, 4-ms rectangular pulses (each nominally 50% successful) followed, when required, by up to six 70-A, 6-ms pulses applied at 15-s intervals in reversing ventricular fibrillation in 100-kg calves was studied in 600 episodes in which 50-A, 6-ms; 70-A, 3-ms; 70-A, 6-ms; 70-A, 12-ms; or 100-A, 6-ms prefibrillation shocks had been delivered 5 s before the induction of fibrillation and in another 600 episodes in which the prefibrillation shock was omitted. We found that 1) there was a modest adverse influence of the prefibrillation shock upon the outcome of the 50-A, 4-ms portion of the sequential shock effort; 2) The 50-A, 4-ms shocks remained reasonably successful throughout the five-shock sequence; 3) when the prefibrillation shock was omitted, the time intervals for a return of a ventricular complex and normal sinus rhythm in the postdefibrillation electrocardiogram increased rapidly with the number of shocks required for defibrillation; and 4) if defibrillation was not achieved with the five-shock sequence, a single 70-A, 6-ms shock was about 94% successful and the sequence of up to six shocks was 100% successful.