Abstract: Methods and apparatus for digital demodulation of signals obtained in the measurement of electrical bioimpedance or bioadmittance of an object. One example comprises: generating an excitation signal of known frequency content; applying the excitation signal to the object; sensing a response signal of the object; sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase; correlating, for each frequency fAC of the excitation signal applied, digitized samples of the response signal, with discrete values representing the excitation signal; calculating, using the correlated signals for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC); providing, over time, a set of digital bioimpedance waveforms Z(fAC,t)); separating the base bioimpedance Z0(fAC), from the waveforms; and separating the changes of bioimpedance ?Z(fAC,t), from the waveforms.

Abstract: An overvoltage protection device protects an electronic medical device in the event of a transient overvoltage on one or more patient lines of the device. A current limiting device is placed in series in a patient line between electronic components of the medical device and a patient interface. A biasing voltage generating device has at least one biasing element located in a line extending off the patient line and at least one additional circuit element connected in series with the biasing element. The biasing voltage generating device is configured to apply a predetermined biasing voltage to the current limiting device via the biasing element in response to a transient overvoltage on the patient line, whereby the current limiting device is switched off and limits current flow through the patient line.

Abstract: Methods and apparatus for digital demodulation of signals obtained in the measurement of electrical bioimpedance or bioadmittance of an object. One example comprises: generating an excitation signal of known frequency content; applying the excitation signal to the object; sensing a response signal of the object; sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase; correlating, for each frequency fAC of the excitation signal applied, digitized samples of the response signal, with discrete values representing the excitation signal; calculating, using the correlated signals for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC); providing, over time, a set of digital bioimpedance waveforms Z(fAC,t)); separating the base bioimpedance Z0(fAC), from the waveforms; and separating the changes of bioimpedance ?Z(fAC,t), from the waveforms.

Abstract: A shock probability determination system and method provides an output of probabilities for different types of shock based on input of selected patient demographic parameters and current clinical parameter values as well as normal ranges for each clinical parameter based on patient demographic data. The probability of different types of shock is determined based on comparison of current clinical parameter values of selected patient hemodynamic parameters to a normal range for each hemodynamic parameter. In one aspect, probabilities of cardiogenic shock, hypovolemic shock, septic shock, and anaphylactic shock are determined. In another aspect, a fluid status indicator is determined based on real-time probability of hypovolemic shock.

Abstract: An electrical pulse generator system such as a cardiac pacemaker or defibrillator system includes an impedance measuring device which measures the impedance across pacemaker leads, a display device, and a controller which controls the display device to display at least the measured impedance upon each stimulation pulse, or an image showing the relationship between a first applied electrical signal, measured impedance, and a resulting electrical signal which varies according to Ohm's Law. The system may include a short circuit detector and a pulse amplitude control module which switches between normal mode and safe mode operation based on short circuit detection, with different maximum stimulation pulse amplitudes in the normal and safe modes.

Abstract: In order to reliably determine the left-ventricular ejection time TLVE of a heart of a subject, at least two different measuring methods are employed. This includes in any case the derivation of a first waveform related to thoracic electrical bioimpedance or bioadmittance. A second waveform can be determined by using pulse oximetry, Doppler velocimetry, measurement of arterial blood pressure and measurement of peripheral electrical bioimpedance or bioadmittance. Depending on signal quality, the results obtained by each method are weighted and then averaged. The weighted average for left-ventricular ejection time is used as an input variable for cardiovascular monitoring methods, which determine objective measurements of cardiovascular function and performance. Such measurements include, but are not limited to, left ventricular ejection fraction, stroke volume, cardiac output, systolic time ratio, and indices of ventricular contractility.

Abstract: For cardiac rhythm management, a combination of cardiac pacing and a noninvasive heart monitoring is proposed for the determination of a set of programmable pacing parameters hemodynamically beneficial to the patient. The apparatus incorporates a cardiac pacemaker and a thoracic electrical bioimpedance (TEB) heart monitor. This combination allows the creation of a closed-loop system that obtains pacing parameter settings providing hemodynamically beneficial pacing therapy to the patient as determined by measuring and recording of stroke volume (SV), cardiac output (CO), and other indices of ventricular performance by the heart monitor during an optimization cycle automatically employing different permutations of values of pacing parameters such as atrioventricular delays, inter-atrial delay, inter-ventricular delay, or heart rate, that are sequentially programmed to the pacemaker.

Abstract: In order to reliably determine the left-ventricular ejection time TLVE of a heart of a subject, at least two different measuring methods are employed. This includes in any case the derivation of a first waveform related to thoracic electrical bioimpedance or bioadmittance. A second waveform can be determined by using pulse oximetry, Doppler velocimetry, measurement of arterial blood pressure and measurement of peripheral electrical bioimpedance or bioadmittance. Depending on signal quality, the results obtained by each method are weighted and then averaged. The weighted average for left-ventricular ejection time is used as an input variable for cardiovascular monitoring methods, which determine objective measurements of cardiovascular function and performance. Such measurements include, but are not limited to, left ventricular ejection fraction, stroke volume, cardiac output, systolic time ratio, and indices of ventricular contractility.

Abstract: In order to reliably determine the left-ventricular ejection time TLVE of a heart of a subject, at least two different measuring methods are employed. This includes in any case the derivation of a first waveform related to thoracic electrical bioimpedance or bioadmittance. A second waveform can be determined by using pulse oximetry, Doppler velocimetry, measurement of arterial blood pressure and measurement of peripheral electrical bioimpedance or bioadmittance. Depending on signal quality, the results obtained by each method are weighted and then averaged. The weighted average for left-ventricular ejection time is used as an input variable for cardiovascular monitoring methods, which determine objective measurements of cardiovascular function and performance. Such measurements include, but are not limited to, left ventricular ejection fraction, stroke volume, cardiac output, systolic time ratio, and indices of ventricular contractility.

Abstract: Doppler Velocimetry is a widely used method for estimating stroke volume (SV). The accuracy and reliability of its measurement however, is dependant on a) the correct assessment of the aortic valve cross-sectional area (CSA), and b) the maximal systolic velocity integral (SVI). The invention avoids the conventional assessment of aortic valve CSA by using a calibration method: a reference stroke volume SVREF is determined by a method different from Doppler velocimetry, e.g. by thoracic electrical bioimpedance (TEB), or thoracic electrical bioadmittance, measured via surface thorax electrodes (transthoracic approach) or via electrodes located directly on an esophageal catheter/probe (esophageal approach). In the latter case, if esophageal Doppler velocimetry is used, the same catheter can be used for the placement of the electrodes and for an ultrasound transducer.

Abstract: The invention relates to an apparatus and a method for determining an approximate value for the stroke volume and the cardiac output of a person's heart. The apparatus and method employ a measured electrical impedance, or admittance, of a part of a person's body, namely, the thorax. This part of a person's body is chosen because its electrical impedance, or admittance, changes with time as a consequence of the periodic beating of the heart. Accordingly, the measured electrical admittance or impedance can provide information about the performance of the heart as a pump.

Abstract: The invention relates to an apparatus and a method for determining an approximate value for the stroke volume and the cardiac output of a person's heart. The apparatus and method employ a measured electrical impedance, or admittance, of a part of a person's body, namely, the thorax. This part of a person's body is chosen because its electrical impedance, or admittance, changes with time as a consequence of the periodic beating of the heart. Accordingly, the measured electrical admittance or impedance can provide information about the performance of the heart as a pump.