Abstract: A system and method involve transceiving successive first and second synchronization signals defining endpoints of a frame. A digital signal is transceived by a modulating time interval between portions of the first and second synchronization signals. A first data pulse is transceived during the frame. A relative position in the frame of the first data pulse represents a first analog signal.

Abstract: A plethysmograph is described that includes a test chamber having an opening; a sealing member including an annular flexible seal to receive at least a part of the head of the test animal mounted across the opening whereby the animal breathes air outside the test chamber, while the animal's body is within the test chamber; and a restraining member attachable to the sealing member, the restraining member including a clamp positionable behind the test animal's head, to prevent the animal from withdrawing its head from the restraining member. The animal is positioned in the restraining member and the sealing member is attached to the restraining member before insertion of the animal and assembly into the test chamber, avoiding previous difficulties in simultaneously placing an animal into the chamber while inserting the animal's nose into the seal. The plethysmograph also eliminates the necessity for a plunger to prevent rearward movement of the animal.

Abstract: Inhalation measurement systems and methods enable, during inhalant exposure, substantially real-time respiratory measurements of a test subject using techniques that obtain measurements of respiration directly from that test subject, instead of from inhalation chamber parameter measurements. Direct test subject respiratory measurements may be, by way of example only, impedance measurements. These respiratory measurements taken directly from the test subject may be transmitted, wirelessly for example, for processing during the course of the test to a processing system to determine a cumulative volume of inhalant inspired by the test subject. From that, a cumulative amount of inhalant (or dose) inspired by the test subject may be determined during the course of the inhalation compound test.

Abstract: A medical device is disclosed for implantation on an epicardial surface of the heart. The device has a transmural member providing optimal electrode locations for various therapies. The hemodynamically optimal therapy is guided by sensed left ventricular pressure and electrical activity. The device may be used alone or with a companion implanted cardiac rhythm management device.

Abstract: In a method for determining a cardiac condition, a sensed physiologic signal for a period of time including multiple cardiac cycles is received. Using the received physiologic data, a heart beat frequency to be used as a reference frequency is determined. A plurality of harmonics of the received physiologic signal is extracted based on the reference frequency, wherein the harmonics correspond to a plurality of alternans frequencies. Amplitudes of at least some of the extracted harmonics are determined, and are used to determine an alternans indicator value.

Abstract: A medical device is disclosed for implantation on an epicardial surface of the heart. The device has a transmural member providing optimal electrode locations for various therapies. The hemodynamically optimal therapy is guided by sensed left ventricular pressure and electrical activity. The device may be used alone or with a companion implanted cardiac rhythm management device.

Abstract: Devices and methods for detecting inadequate tissue perfusion by measuring a parameter other than heart rate such as vascular blood pressure, intracardiac blood pressure, vascular blood flow or tissue perfusion, in addition to or as a substitute for heart rate. Such devices and methods improve the accuracy of determining when and to what degree therapy should be administered to treat inadequate tissue perfusion, such as pre-syncope, syncope, or orthostatic hypotension, particularly in the absence of abnormal cardiac function.

Abstract: Various different implementations of lead systems are disclosed for use with implantable stimulation systems. Generally, the lead systems incorporate, within an elongate lead body, one or more electrical conduits that connect to one or more distal electrodes, and a liquid-filled pressure transmission catheter lumen that extends proximally from a distal entry port. Use of the lead systems allows accurate pressure sensing at a location near where the electrodes are positioned. In addition, a defibrillator lead is disclosed having such features, and a system using that lead is capable of directly monitoring pressure within a heart chamber, and using that information to confirm the delivery of a defibrillation pulse.

Abstract: Methods and apparatus of the present invention provide viscoelastic barrier materials for use as barriers in devices such as pressure measurement catheters. Improved barrier materials sometimes include at least one barrier material precursor combined with an amount of a softener. In other embodiments, two barrier material precursor components are combined without a softener to provide a fully cross-linked barrier material having certain softness characteristics. In various embodiments, a softener may be dimethyl silicone oil and may be combined with a barrier material precursor in an amount of between about 25% and about 45% by weight, relative to the final barrier material. Once a viscoelastic barrier material is prepared, it may be placed in a pressure transmission catheter or similar device, for example by injecting the gel into a lumen of the catheter via a syringe.

Abstract: The disclosed embodiments present improved catheters with physiological sensors. In one embodiment, the catheter includes, generally, a pressure transducer/electronics assembly connected to a pressure transmission catheter. The pressure transmission catheter includes a hollow tube made from a low compliance material. The distal end of the hollow tube is filled with a gel-like material or plug which acts as a barrier between the catheter liquid and the target fluid. The hollow tube is partially filled with a low viscosity liquid and is in fluid communication with the gel-like material and the pressure transducer. The pressure of the target fluid is transmitted to the liquid in the hollow tube through the gel-like material and/or the wall of the distal tip and is fluidically transmitted to the pressure transducer. The pressure transmission catheter is capable of being inserted into a vessel lumen or inserted into a lumen of a therapeutic or diagnostic catheter for biomedical applications.

Abstract: A system and method involve transceiving successive first and second synchronization signals defining endpoints of a frame. A digital signal is transceived by a modulating time interval between portions of the first and second synchronization signals. A first data pulse is transceived during the frame. A relative position in the frame of the first data pulse represents a first analog signal.

Abstract: A strobed blood flow meter provides periodic measurements of blood flow velocity or volumetric blood flow over a cardiac cycle at reduced average power consumption, which is advantageous for reducing battery size, and extending device battery life, such as in an implantable application. Continuous wave Doppler, pulsed Doppler, laser Doppler, transit time, electromagnetic flow, and thermal dilution techniques are included. Strobing provides higher level excitation during active periods, which improves signal-to-noise ratio, and provides a low power standby mode during an idle time between active periods. The invention may be used for chronic or acute applications. Doppler or other signals may be telemetered from an implanted portion of the flow meter for further signal processing to extract velocity or volumetric flow. Alternatively, such signal processing is also implanted, such that the velocity signal can be telemetered to an remote monitor.

Abstract: A method for detecting a phase difference between first and second input signals is provided. The method includes modulating a duty cycle of first and second intermediate signals from a first duty cycle based on the phase difference between the first and second input signals. The method further includes creating a differential output signal based on the modulated duty cycles of the first and second intermediate signals that is related to the phase difference between the first and second input signals.

Abstract: A system and method obtains physiologic parameter information of an animal or human, such as respiratory rate, from a blood pressure signal from an implanted blood pressure sensor in the animal or human. Specifically, the blood pressure signal is externally signal processed to develop an amplitude versus time waveform. A sequence of selected blood pressure features derived from individual cardiac cycles of the amplitude versus time waveform over a selected time interval are extracted from the developed amplitude versus time waveform. A mathematical model is fitted to the extracted sequence of selected blood pressure features to yield a fitted mathematical model. The physiologic parameter information is computed from the fitted mathematical model.

Abstract: An implantable sensor device, such as a pressure monitor, is implanted in the left ventricle (LV), in other heart chambers, or elsewhere, from which it wirelessly communicates pressure information to a remote communication device. The sensor device can be implanted using a placement catheter, an endoscope, or a laparoscope. The device can be secured entirely within the LV or heart wall, such as by using a corkscrew, a helical anchor, a harpoon, a threaded member, a hook, a barb, a fastener, a suture, or a mesh or coating for receiving fibrous tissue growth. The implantable sensor device provides less invasive chronic measurements of left ventricular blood pressure or other physical parameters. The wireless communication techniques include radio-telemetry, inductive coupling, passive transponders, and using the body as a conductor (referred to as “intracorporeal conductive communication” or a “personal area network”).

Abstract: A method for detecting a phase difference is provided. The method includes selecting first and second input signals from a plurality of pairs of input signals. The method further includes modulating a duty cycle of first and second intermediate signals from a first duty cycle based on a phase difference between the first and second input signals. The method also includes creating a differential signal based on the modulated duty cycles of the first and second intermediate signals that is related to the phase difference between the first and second input signals.

Abstract: The present invention provides a method for improving the bio-compatibility of devices, especially medical devices which are invasively present within a patient's body and the improved medical device. The present invention particularly reduces the thrombogenicity of polyurethane materials in contact with the blood of a living patient. The method comprises providing a bio-compatible medical device having polymeric polyurethane components thereon, exposing the polyurethane components of the medical device to polar solvents for said polymeric components while the polar solvents are in the vapor phase, and allowing said vapor phase exposure to continue for a sufficient amount of time as to reduce at least some irregular or sharp features on the surface of the polymeric component.

Abstract: A system and method obtains physiologic parameter information of an animal or human, such as respiratory rate, from a blood pressure signal from an implanted blood pressure sensor in the animal or human. Specifically, the blood pressure signal is externally signal processed to develop an amplitude versus time waveform. A sequence of selected blood pressure features derived from individual cardiac cycles of the amplitude versus time waveform over a selected time interval are extracted from the developed amplitude versus time waveform. A mathematical model is fitted to the extracted sequence of selected blood pressure features to yield a fitted mathematical model. The physiologic parameter information is computed from the fitted mathematical model.

Abstract: An implantable sensor device, such as a pressure monitor, is implanted in the left ventricle (LV), in other heart chambers, or elsewhere, from which it wirelessly communicates pressure information to a remote communication device. The sensor device can be implanted using a placement catheter, an endoscope, or a laparoscope. The device can be secured entirely within the LV or heart wall, such as by using a corkscrew, a helical anchor, a harpoon, a threaded member, a hook, a barb, a fastener, a suture, or a mesh or coating for receiving fibrous tissue growth. The implantable sensor device provides less invasive chronic measurements of left ventricular blood pressure or other physical parameters. The wireless communication techniques include radio-telemetry, inductive coupling, passive transponders, and using the body as a conductor (referred to as “intracorporeal conductive communication” or a “personal area network”).

Abstract: A flow probe has been described which includes a sensor housing and a coupling member. The sensor housing with one or more sensors mated together with the coupling member form the flow probe. The sensor housing accepts a variety of different sized coupling members to form flow probes of different sizes. The sensor housing is adapted to house one or more transducers. Additionally, a version of the flow probe includes strategically located positioning elements for ease in placement and retrieval of the flow probe.