A trapezoidal waveshape, which is known to be the best waveshape for defibrillating the heart, is produced by charging a capacitor, and by starting to discharge it through a silicon controlled rectifier to the load, namely, the body of the patient. Subsequently, a second SCR is used to short circuit the first SCR and load circuit to effect termination of the trapezoidal waveshape rapidly, i.e., effectively dumping the remainder of the charge.
An antitachycardia device, either implanted or external, which delivers a fixed pulse width truncated exponential waveform defibrillation shock and automatically adjusts the pulse duration based upon the impedance measured or calculated following a delivered shock. The apparatus operates by measuring or calculating the high voltage system impedance, selecting a pulse width for that impedance value and using a pulse width derived from the selected pulse width for the next defibrillation shock.
A portable, automatic external defibrillator, comprising a plurality of capacitors; a capacitor charging circuit; connections from the capacitors to a patient body; and a plurality of semiconductor switches arranged to connect the capacitors to the charging circuit and to the patient body. At least one leakage shunting switch is included to prevent leakage currents from being conducted to the patient.
A defibrillator is disclosed which regulates the magnitude of a current pulse delivered to a patient in accordance with a selected value of current and which quickly terminates the current pulse when the measured energy delivered to the patient equals a selected value. Current regulation is accomplished by circuitry which compares current actually flowing through the patient with the selected value and which utilizes the results of such comparison to sequentially discharge a plurality of capacitors serially coupled to the patient electrodes. Further circuity multiplies the current through the patient by the voltage measured across the patient to determine power with the resulting signal being integrated relative to time to indicate delivered energy. When the delivered energy equals the selected value of energy, the electrodes are shunted by circuitry which terminates the current pulse to the patient and which discharges all capacitors not already discharged.
A portable, automatic external defibrillator, comprising a plurality of capacitors; a capacitor charging circuit; connections from the capacitors to a patient body; and a plurality of semiconductor switches arranged to connect the capacitors to the charging circuit and to the patient body.
A portable, automatic external defibrillator, comprising a plurality of capacitors; a capacitor charging circuit; connections from the capacitors to a patient body; and a plurality of semiconductor switches arranged to connect the capacitors to the charging circuit and to the patient body.
