Abstract: A cardiopulmonary resuscitation (CPR) compression force indicator includes circuitry (20, 26, 28, 30) for monitoring a patient's transthoracic impedance while the patient is being given CPR and generating a corresponding impedance signal, circuitry (32, 34, 36) for processing the impedance signal to provide an ongoing measurement of cardiac hemodynamic output, a microprocessor (24) for determining if the measurement falls outside pre-set limits, and indicator(s) (38) for indicating such determination externally to the person giving the CPR.

Abstract: An H-bridge switching circuit for an automated external defibrillator comprises an SCR (D8) in one of the high legs of the circuit and a control means (D1-D7) associated with the SCR which is operative to switch the SCR on automatically in response to a voltage change across the SCR corresponding to the switching device in the diagonally opposite leg of the H-bridge turning on. The control means comprises a capacitor (D1) and the voltage on the capacitor changes when the diagonally opposite switching device turns on, the change in capacitor voltage lagging the change in voltage across the SCR and the SCR being turned on when the difference between the capacitor voltage and the voltage across the SCR exceeds a predetermined threshold.

Abstract: A cardiopulmonary resuscitation (CPR) compression force indicator comprises means (20, 26,? 28, 30) for monitoring a patient's transthoracic impedance while the patient is being given CPR and generating a corresponding impedance signal, means (32, 34, 36) for processing the impedance signal to provide an ongoing measurement of cardiac haeraodynamic output, means (24) for determining if the measurement falls outside pre-set limits, and means (38) for indicating such determination externally to the person giving the CPR.

Abstract: A single-use battery-powered external defibrillator comprises a sealed defibrillator housing 10 containing a battery-powered defibrillator circuit and a pair of defibrillator electrodes 14 permanently attached by leads 22 to the circuit within the housing.

Abstract: An H-bridge switching circuit for an automated external defibrillator comprises an SCR (D8) in one of the high legs of the circuit and a control means (D1-D7) associated with the SCR which is operative to switch the SCR on automatically in response to a voltage change across the SCR corresponding to the switching device in the diagonally opposite leg of the H-bridge turning on. The control means comprises a capacitor (D1) and the voltage on the capacitor changes when the diagonally opposite switching device turns on, the change in capacitor voltage lagging the change in voltage across the SCR and the SCR being turned on when the difference between the capacitor voltage and the voltage across the SCR exceeds a predetermined threshold.