Medtronic Physio-Control Manufacturing Corporation

Medtronic, Inc.

Medtronic Physio-Control Corp.

David W Van Ess

Dana Jon Olson

Joseph Leo Sullivan

Robert W Stadler

Gary DeBardi

Jeffrey David Wilkinson

Steven N Lu

Scott Owen Schweizer

Tyler R Hart

Tara N Ptak

The invention presents techniques for identifying signals detected by electrodes on the body of a patient as part of a reading of the patient's electrocardiogram. A signal processor digitally filters the signal from the body, resulting in an electrocardiogram signal and a signal that identifies the presence and timing of signals from a pacemaker in the body. Other signals, such as a signal that reflects the quality of the electrical connection of the electrode to the body, may also be obtained by digital filtering.

Electrocardiogram filter

An energy adjusting circuit for use with a defibrillator. The energy adjusting circuit reduces the defibrillation pulse energy that would otherwise be applied to the patient by the defibrillator. The energy adjusting circuit can be part of the defibrillator itself, or part of an adapter coupled to the output ports of a conventional defibrillator. In an adapter designed for pediatric defibrillation, the adapter may include paddles configured for use on babies and small children. The energy adjusting circuit may be formed entirely from passive components and may include a divider circuit with two resistors. The resistance of the two resistors is selected so as to absorb a predetermined percentage of the defibrillation pulse energy that would otherwise be applied to the patient. An isolation circuit may be further included to assist with the measurement of ECG signals through the electrodes. The components of the energy adjusting circuit can be selected so as to produce a defibrillation waveform that has a desired pulse width and tilt, both of which are approximately fixed over an expected range of patient impedances. The defibrillator may be configured to recognize the presence of the energy adjusting circuit, and to indicate to the user that the energy selection ranges have been adjusted accordingly.

Energy adjusting circuit for producing an ultra-low energy defibrillation waveform with fixed pulse width and fixed tilt

A signal measuring system for use with an Implantable Medical Device (IMD) is provided for measuring physiologic signals having a relatively large effective dynamic range. In one embodiment, the system includes a High-Pass Filter (HPF), an Analog-to-Digital Converter (ADC), a Decimation Filter (DF), and a Compensation Filter (CF). The HPF receives an input signal that includes both the baseline wander imposed on a physiological signal. According to one aspect of the invention, the HPF attenuates low frequency components of the input signal, including a portion of the frequency band within the desired output signal bandwidth. The ADC then oversamples the output signal of the HPF. The DF receives the output samples from the ADC and generates output samples at rate that is at least twice the maximum frequency of the desired output signal. The CF then amplifies the low frequency end of the DF output samples. The gain and cutoff frequency of the CF are selected to offset the HPF attenuation of those low frequency components of the input signal below the cutoff frequency of the HPF and above the minimum frequency of the desired output signal. In one embodiment, the DF and CF are implemented by a processing circuit executing programmed instructions. The processing circuit may be included within the IMD, or may be partially or fully implemented within a device that is external to the IMD.

Method and apparatus for increasing the low frequency dynamic range of a system for measuring physiological signals with an implantable medical device

An ECG signal measuring system uses low frequency compression/enhancement techniques combined with dither techniques to effectively increase the dynamic range while maintaining resolution. This aspect of the present invention is achieved without increasing the number of bits of the ADC. The system includes a HPF, an ADC, a decimation filter (DF), and a compensation filter (CF). The HPF receives an input signal (i.e., the bias current combined with ECG input signal) and attenuates the low frequency components of the input signal, including a portion of the frequency band within the desired ECG frequency band. The ADC oversamples the output signal of the HPF. The DF receives the output samples of the ADC and generates output samples at rate that is at least twice the maximum frequency of the desired ECG output signal. The CF amplifies the low frequency end of the DF output samples. The gain and cutoff frequency of the CF are set to offset the HPF's attenuation of those low frequency components of the input signal below the minimum frequency of the desired ECG output signal. System noise can be used as the dither. Consequently, the ECG output signal remains within the dynamic range of the system.

Method and apparatus for increasing the low frequency dynamic range of a digital ECG measuring system

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Arlington, WA, United States of America

David W Van Ess