Abstract: A method for gathering event data using a data gathering instrument having an instrument clock and an instrument data storage medium, the method comprising the steps of: gathering event data using the data gathering instrument; storing the event data in an instrument data storage medium; using an instrument clock to associate time information with the event data; storing the associated time information in the instrument data storage medium; separating the instrument data storage medium from the data gathering instrument; separating the instrument clock from the data gathering instrument; and storing in a main data storage medium the event data and the time information stored in the instrument data storage medium. The invention also includes a data gathering system practicing this method, the data gathering instrument itself, and removable instrument clock and memory modules, preferably disposed together in a housing such as a PCMCIA format card.

Abstract: A method for gathering event data using a data gathering instrument having an instrument clock and an instrument data storage medium, the method comprising the steps of: gathering event data using the data gathering instrument; storing the event data in an instrument data storage medium; using an instrument clock to associate time information with the event data; storing the associated time information in the instrument data storage medium; separating the instrument data storage medium from the data gathering instrument; separating the instrument clock from the data gathering instrument; and storing in a main data storage medium the event data and the time information stored in the instrument data storage medium. The invention also includes a data gathering system practicing this method, the data gathering instrument itself, and removable instrument clock and memory modules, preferably disposed together in a housing such as a PCMCIA format card.

Abstract: The present invention is an apparatus and method for detecting differential mode signals in an environment where differential mode signals co-exist, and might be corrupted by, common mode signals. The most basic apparatus of the present invention essentially comprises first and second input leads through which both differential mode and common mode signals are input; a first amplifier block having a gain that is substantially one; and at least an inverting node and a non-inverting node connected to the first and second input leads. The output of the amplifier block is fed back to the input of the non-inverting node of the amplifier block in a manner to increase differential mode impedance while maintaining a low common mode impedance. Various embodiments of the basic presently claimed circuitry provides for additional methods of monitoring the level of common-mode signal introduced to the apparatus and other fault detection functions.

Abstract: The present invention is an apparatus and method for detecting differential mode signals in an environment where differential mode signals co-exist, and might be corrupted by, common mode signals. The most basic apparatus of the present invention essentially comprises first and second input leads through which both differential mode and common mode signals are input; a first amplifier block having a gain that is substantially one; and at least an inverting node and a non-inverting node connected to the first and second input leads. The output of the amplifier block is fed back to the input of the non-inverting node of the amplifier block in a manner to increase differential mode impedance while maintaining a low common mode impedance. Various embodiments of the basic presently claimed circuitry provides for additional methods of monitoring the level of common-mode signal introduced to the apparatus and other fault detection functions.

Abstract: This invention provides an external defibrillator and defibrillation method that automatically compensates for patient-to-patient impedance differences in the delivery of electrotherapeutic pulses for defibrillation and cardioversion. In a preferred embodiment, the defibrillator has an energy source that may be discharged through electrodes on the patient to provide a biphasic voltage or current pulse. In one aspect of the invention, the first and second phase duration and initial first phase amplitude are predetermined values. In a second aspect of the invention, the duration of the first phase of the pulse may be extended if the amplitude of the first phase of the pulse fails to fall to a threshold value by the end of the predetermined first phase duration, as might occur with a high impedance patient.

Abstract: An electrotherapy method and apparatus for delivering a multiphasic waveform from an energy source to a patient. The preferred embodiment of the method comprises the steps of charging the energy source to an initial level; discharging the energy source across the electrodes to deliver electrical energy to the patient in a multiphasic waveform; monitoring a patient-dependent electrical parameter during the discharging step; shaping the waveform of the delivered electrical energy based on a value of the monitored electrical parameter, wherein the relative duration of the phases of the multiphasic waveform is dependent on the value of the monitored electrical parameter.

Abstract: This invention provides an external defibrillator and defibrillation method that automatically compensates for patient-to-patient impedance differences in the delivery of electrotherapeutic pulses for defibrillation and cardioversion. In a preferred embodiment, the defibrillator has an energy source that may be discharged through electrodes on the patient to provide a biphasic voltage or current pulse. In one aspect of the invention, the first and second phase duration and initial first phase amplitude are predetermined values. In a second aspect of the invention, the duration of the first phase of the pulse may be extended if the amplitude of the first phase of the pulse fails to fall to a threshold value by the end of the predetermined first phase duration, as might occur with a high impedance patient.

Abstract: This invention provides an external defibrillator and defibrillation method that automatically compensates for patient-to-patient impedance differences in the delivery of electrotherapeutic pulses for defibrillation and cardioversion. In a preferred embodiment, the defibrillator has an energy source that may be discharged through electrodes on the patient to provide a biphasic voltage or current pulse. In one aspect of the invention, the first and second phase duration and initial first phase amplitude are predetermined values. In a second aspect of the invention, the duration of the first phase of the pulse may be extended if the amplitude of the first phase of the pulse fails to fall to a threshold value by the end of the predetermined first phase duration, as might occur with a high impedance patient.

Abstract: A defibrillator patient connection system is disclosed for automatically identifying to a defibrillator system the type of pads or paddles assembly connected to the system for conveying electrical energy to shock a patient. Each of the available pads or paddles assemblies is identified by a corresponding analog voltage level provided to the base unit through a corresponding cable assembly. The identification voltage is sensed by an A/D converter in the defibrillator base unit. The identification voltage is provided to the base unit on a charge-done signal line which otherwise is asserted by the base unit to controllably actuate a charge-done indicator light in an external paddles assembly. The disclosed methods and apparatus thus maintain a simple defibrillator/cable assembly interface and require no additional signal lines for implementing automatic identification.

Abstract: A method for gathering event data using a data gathering instrument having an instrument clock and an instrument data storage medium, the method comprising the steps of: gathering event data using the data gathering instrument; storing the event data in an instrument data storage medium; using an instrument clock to associate time information with the event data; storing the associated time information in the instrument data storage medium; separating the instrument data storage medium from the data gathering instrument; separating the instrument clock from the data gathering instrument; and storing in a main data storage medium the event data and the time information stored in the instrument data storage medium. The invention also includes a data gathering system practicing this method, the data gathering instrument itself, and removable instrument clock and memory modules, preferably disposed together in a housing such as a PCMCIA format card.

Abstract: A defibrillator patient connection system is disclosed for automatically identifying to a defibrillator system the type of pads or paddles assembly connected to the system for conveying electrical energy to shock a patient. Each of the available pads or paddles assemblies is identified by a corresponding analog voltage level provided to the base unit through a corresponding cable assembly. The identification voltage is sensed by an A/D converter in the defibrillator base unit. The identification voltage is provided to the base unit on a charge-done signal line which otherwise is asserted by the base unit to controllably actuate a charge-done indicator light in an external paddles assembly. The disclosed methods and apparatus thus maintain a simple defibrillator/cable assembly interface and require no additional signal lines for implementing automatic identification.

Abstract: Adaptive clock generator including a master clock. A control means detects the current operating mode and, in response, provides a corresponding integer output N. A programmable pulse generator provides an output clock signal comprising a "high" pulse having a predetermined width followed by a "low" pulse having a width of N master clock periods. A dithered clock signal may be provided when the control means provides an integer output N selected from a set of integer values. Preferably, N is selected in a random or pseudo-random manner.

Abstract: A defibfillator has a self healing storage capacitor connected in parallel with a safety resistor, and a microcontroller. Upon receipt of a calibration request, the microcontroller charges the capacitor to a charging voltage greater than a starting voltage, then discharges the capacitor through the safety resistor. As the capacitor is discharging, the microcontroller continuously measures the voltage across the capacitor. When the microcontroller detects that the voltage across the capacitor is less than or equal to a starting voltage, a timer in the microcontroller is started. When the microcontroller detects that the voltage across the capacitor is less than or equal to an ending voltage, the timer in the microcontroller is stopped. The microcontroller then determines an elapsed time between the time the timer was started and stopped. The microcontroller then calculates a capacitance value of the capacitor based on the starting voltage, the ending voltage, and the elapsed time.

Abstract: A defibrillator/monitor architecture is disclosed with a defibrillator-only mode of operation to provide for shocking a patient notwithstanding failure of the monitor subsystem. The defibrillator/monitor subsystem is partitioned into a defibrillator subsystem and a monitor subsystem. The defibrillator subsystem includes the patient charging circuits and other components necessary to carry out basic defibrillation. The monitor subsystem includes an ECG front-end, CRT display, data recorder and other features. In normal operation, the defibrillator subsystem relies on periodic ECG data ready interrupts from the monitor subsystem for system timing. In the event that the ECG interrupts do not arrive within a predetermined time limit, the monitor subsystem is presumed dead and the defibrillator subsystem switches to defibrillator-only mode of operation, in which system timing is provided by a local standby timer.

Abstract: A portable data acquisition unit which features a sample order register which sets addresses in a multiplexer unit allowing one out of many electrical signals connected to the multiplexer to pass through at one time. The selected electrical signal is a sample which is transmitted to an A-to-D converter so that a digital signal is generated and passed to a communications port and then to a remote host device. A clock pulse increments the next address in the sample order list to the multiplexer to establish the next signal sample to be transmitted to the host device. At the host device, the original electrical signals may be reconstituted. For example, the electrical signals may be physiological signals derived from transducers associated with an EKG. The host device may be a remote EKG apparatus.

Abstract: A cardiograph has a remote front end which is connected to a host via a cable. The front end includes a clock and an analog-to-digital converter. The converter periodically holds and samples patient ECG signals. Each conversion takes place within the same fixed length of time. A clock signal is transmitted to the host on one of the conductors in the cable while digital words, each of which represents a sampled value of the ECG signal, are serially transmitted on another conductor in the cable. The clock signal synchronizes ac voltages applied to several power supplies with the sampling rate of the converter so that the ECG signal is sampled at the same phase of each ac voltage applied to the power supplies. The sampling thus occurs at the same phase, and thus the same amplitude, of each periodic noise cycle induced by the power supply electromagnetic fields. The periodic noise is thus removed from the sampled signal while a dc offset equal to the amplitude of the periodic noise at the sampling phase is added.

Abstract: An input keyboard arrangement is provided for microcomputers, computer terminals, and other devices for processing alphanumeric information. The keyboard arrangement facilitates entry of information by non-typists, increases keying accuracy, enables use of the three strongest fingers for depressing keys, and minimizes the time needed to master the keyboard. The keyboard is arranged in a vertical layout with a pair of enter keys, and elongate shift and space bars located around the perimeter of the key arrangement. Each letter of the alphabet is represented by an individidual key and the alphabetic keys are arranged in alphabetical order in nine rows with three keys per row so as to facilitate human information processing. Specifically, the keys of the first row are arranged, sinistrally, as c-b-a or, dextrally, as a-b-c, the second row f-e-d or d-e-f, and so on, with the pattern continuing to the ninth row which contains the keys "z-y" or "y-z.