68 results about "Thoracic impedance" patented technology

A portable thoracic impedance monitor for monitoring thoracic fluid levels, an electrode array assembly having a single linear electrode array lead with first, second, third, and fourth electrodes arranged sequentially and axially along the linear electrode array lead, and a method of use of the thoracic impedance monitor. A measurement of the user's thoracic impedance is obtained by connecting the second electrode to the user's body at the junction of the clavicles, superior to the sternum, the third electrode to the user's body at the xyphiod-sternal junction, and the first and fourth electrodes to the user's body substantially along a centerline of the user's sternum respectively at a first pre-determined distance above the second electrode and a second predetermined distance below the third electrode, followed by initiating operation of the monitor.

A fluid status monitoring system for use in implantable cardiac stimulation or monitoring devices is provided for monitoring changes in thoracic fluid content. A fluid status monitor includes excitation pulse generating and control circuitry, and voltage and current measurement and control circuitry for performing a series of cardiac-gated, intra-thoracic impedance measurements. The cardiac-gated measurements are filtered or time-averaged to provide a fluid status impedance value, with respiratory noise removed. Based on comparative analysis of the fluid status impedance value, a clinically relevant trend in fluid status may be tentatively diagnosed and a fluid status response provided. Cross-check intra-thoracic impedance measurements performed using the same or a different excitation pathway and a different measurement pathway than the primary intra-thoracic impedance measurement configuration may be used to verify a tentative diagnosis.

A method of diagnosing pulmonary congestion is provided. At least one decrease in a trans-thoracic impedance value from a baseline trans-thoracic impedance value is sensed. At least one increase in a heart rate value from a baseline heart rate value is also sensed. Pulmonary congestion is diagnosed if the decrease in the trans-thoracic impedance value corresponding to the increase in the heart rate does not increase after a predetermined interval. Systems and programs incorporating the method are also provided.

This patent document discusses, among other things, systems, devices, and methods for enhancing detection of pulmonary edema using, in addition to thoracic impedance, one or a combination of: physiologic information about a subject, at least one statistical parameter, a user-programmable detection level, at least one parameter associated with a previous pulmonary edema event, and patient symptom information about the subject. In one example, a (base) thoracic impedance threshold is modified to an adjusted thoracic impedance threshold. The adjusted thoracic impedance threshold provides an increased sensitivity of pulmonary edema detection as compared to the base thoracic impedance threshold. In another example, an alert is provided to a subject, a caregiver, or other user based on a pulmonary edema indication determined by the present systems, devices, and methods. In a further example, a therapy (provided to the subject) is adjusted or initiated in response to the pulmonary edema indication.

A system includes an implantable medical device that includes a trans-thoracic impedance measurement circuit providing a trans-thoracic impedance signal of a subject. A controller is coupled to the trans-thoracic impedance circuit. The controller extracts a respiration signal from the trans-thoracic impedance signal, measures a breathing volume of the subject using the amplitude of the respiration signal and a breathing volume calibration factor, computes an adjusted breathing volume calibration factor using a reference baseline value of the trans-thoracic impedance and a measured baseline value of the trans-thoracic impedance, and computes a calibrated breathing volume using the adjusted breathing volume calibration factor.

This patent document discusses, among other things, systems, devices, and methods for enhancing detection of pulmonary edema using, in addition to thoracic impedance, one or a combination of: physiologic information about a subject, at least one statistical parameter, a user-programmable detection level, at least one parameter associated with a previous pulmonary edema event, and patient symptom information about the subject. In one example, a (base) thoracic impedance threshold is modified to an adjusted thoracic impedance threshold. The adjusted thoracic impedance threshold provides an increased sensitivity of pulmonary edema detection as compared to the base thoracic impedance threshold. In another example, an alert is provided to a subject, a caregiver, or other user based on a pulmonary edema indication determined by the present systems, devices, and methods. In a further example, a therapy (provided to the subject) is adjusted or initiated in response to the pulmonary edema indication.

This document discusses, among other things, systems and methods that detect hypotension based on a measurement of thoracic impedance. It also provides an alert, a logging, or a therapy to treat the hypotension. Examples of anti-hypotension therapies include, among other things, pacing therapy, neural stimulation therapy, drug infusion therapy, or gene therapy.

A system and method are described for automatically detecting diaphragmatic stimulation (DS) based on evoked response signals, electrogram data and/or thoracic impedance measurements. In addition, several optional modalities are described to circumvent this problem and alleviate symptoms related to DS while preserving LV pacing.

An active implantable medical device comprising circuits for measuring trans-thoracic impedance and delivering an impedance signal varying with respiratory activity of a patient. A signal representative of the respiratory activity of the patient is delivered starting from the impedance signal, and circuits for diagnosing respiratory disorder analyze variations of the respiratory signal on a plurality of successive cycles to detect there a profile of predetermined variation in relation to a given respiratory disorder. The device also includes circuits for automatically controlling respiratory cycles with artifacts, able to identify in the impedance signal a jump of static impedance, and/or to identify in a respiratory cycle or in a sequence of respiratory cycles a predetermined singularity representative of a cycle with artifact.

Techniques are provided for detecting pulmonary edema based on a comparison of impedance-based respiratory patterns and impedance-based cardiac patterns, i.e. patterns derived from thoracic impedance signals. In one example, a numerical ratio is calculated between average peak-to-peak amplitudes of the respiratory patterns and average peak-to-peak amplitudes of the cardiac patterns. Pulmonary edema is detected if the amplitude ratio falls below a pulmonary edema detection threshold. Techniques are also provided for controlling operation of an impedance-based reduced respiration detector, i.e. a detector which seeks to detect apnea, hypopnea, or the like, based on analysis of respiratory patterns derived from a thoracic impedance signal. If the numerical ratio falls below a minimum reliability threshold, then the reduced respiration detector is deactivated because episodes of reduced respiration cannot then reliably be derived from an analysis of respiration patterns obtained from the thoracic impedance signals.

An automatic external defibrillator (AED) with a discrete sensing pulse for use in configuring a therapeutic biphasic waveform. The sensing pulse is used to determine a patient-specific parameter (e.g., thoracic impedance) prior to delivery of the therapy waveform. The defibrillator adjusts the therapy waveform, based on the patient-specific parameter, prior to delivery to the patient.

The invention relates to a high-performance lung function detecting system and method based on thoracic impedance measurement. The high-performance lung function detecting system comprises a microcontroller, an upper computer, an exciting circuit, a signal conditioning and data collection circuit, an electrode buffer unit and a special electrode array, wherein the exciting circuit generates an exciting current under control of the microcontroller, and the exciting current is obtained by converting a differential voltage signal and acts on the special electrode array through the electrode buffer unit; the signal conditioning and data collection circuit collects an exciting current signal and a response voltage signal through the electrode buffer unit; the microcontroller demodulates the exciting current signal and the response voltage signal, calculates the amplitude and phase of thoracic impedance and uploads the amplitude and phase of the thoracic impedance to the upper computer; andthe upper computer obtains the assessment result of lung functions of a detected object according to the amplitude and phase of the thoracic impedance. Compared with the prior art, the high-performance lung function detecting system and method have the advantages of easy implementation, low system cost, high detection sensitivity, fast and convenient measurement and the like, and the detecting experience of a doctor and a patient can be effectively improved.

The invention discloses a method and an auxiliary device of determining cardiopulmonary resuscitation quality parameters during the process of cardiopulmonary resuscitation. The auxiliary device comprises an incentive module, a signal collection module and a signal processing module. The incentive module is used for exerting an incentive signal on a target object. The signal collection module is used for collecting a responding signal produced by the target object to the incentive signal. The signal processing module is used for analyzing and collecting the responding signal to obtain a direct current component and an alternating current component of the signal processing module, and is used for analyzing and calculating the cardiopulmonary resuscitation quality parameters of the target object according to the direct current component and the alternating current component. According to the method and the device of determining the cardiopulmonary resuscitation quality parameters during the process of cardiopulmonary resuscitation, the incentive signal is exerted on the target object, the responding signal produced by the target object thoracic impedance when responding to the incentive signal is detected, analysis and calculation are carried out according to the responding signal, so that the parameters related to the cardiopulmonary resuscitation quality is obtained. Therefore, the whole quality of the cardiopulmonary resuscitation can be known in real time and cardiopulmonary resuscitation measure can be adjusted in time according to the parameters to achieve the perfect cardiopulmonary resuscitation effect.

In a method and an implantable medical device for assessing a degree of pulmonary edema of a patient, at least two specific body patients of the patent are detected and at least one impedance sensing session is initiated to sense trans-thoracic impedance signals from the patient when the patient is in one of the at least two specific positions. Impedance values are obtained from the impedance signals, and a relation between respective impedance values at the at least two positions is determined. This relation is then used as a metric of pulmonary edema to assess the degree of pulmonary edema, and is provided as an output.

Techniques are provided for monitoring thoracic fluid levels based on thoracic impedance (Z_T) and cardiogenic impedance (Z_C). In one example, the implantable device tracks the maximum time rate of change in cardiogenic impedance (i.e. max(dZ_C/dt)) to detect trends toward hypervolemic or hypovolemic states within the patient based on changes in heart contractility. The detection of these trends in combination with trends in thoracic impedance allows for a determination of whether the thoracic cavity of the patient is generally “too wet” or “too dry,” and thus allows for the titration of diuretics to avoid such extremes. In particular, a decrease in thoracic impedance (Z_T) in combination with a decrease in max (dZ_C/dt) is indicative of the thorax being “too wet” (i.e. a fluid overload). Conversely, an increase in thoracic impedance (Z_T) in combination with a decrease in max (dZ_C/dt) is indicative of the thorax being “too dry” (i.e. a fluid underload).

A method is presented for evaluating whether an episode of sleep apnea is occurring in a patient suffering from chronic sleep apnea disorder, for delivery of appropriate therapy. The method, performed by an implantable device, includes sensing the patient's EKG signal and using electrical energy generated by the heart to power subsequent signal processing. This signal is applied as the sole input to a differential signal processing circuit for passage through both a high impedance path and a substantially lower impedance path and amplification of the difference in magnitude between the resulting two signals, to determine changes in the patient's thoracic impedance. Based on such changes, the presence or absence of patient ventilation is detected, to enable an assessment of whether an episode of sleep apnea is occurring. An actual episode of sleep apnea is deemed to have occurred if lack of ventilation exceeds a predetermined interval of time between otherwise regular respiratory cycles. If sleep apnea is indicated, the appropriate therapy is delivered by the device to induce ventilation and halt the apnea episode.