Abstract: A medical device system and associated method are used for monitoring tissue oxygenation. An optical sensor produces a signal corresponding to tissue light attenuation. A processor receives the optical sensor signal and computes a first measure of light attenuation at a first light wavelength and a second measure of light attenuation at a second light wavelength. In one embodiment, noise cancellation circuitry receives the first measure and the second measure and generates a guessed ratio of the first and second measures. Using the first measure, the second measure and the guessed ratio, the noise cancellation circuitry provides a peak output power when the guessed ratio corresponds to an actual ratio of the first and second measures.

Abstract: A medical device for monitoring a patient condition includes a first combination of a light source and a light detector to emit light into a volume of tissue, detect light scattered by the volume of tissue, and provide a first output signal corresponding to an intensity of the detected light. A control module is coupled to the light source to control the light source to emit light at least four spaced-apart light wavelengths, and a monitoring module is coupled to the light detector to receive the output signal, compute a measure of tissue oxygenation in response to the light detector output signal, and detect tissue hypoxia using the measure of tissue oxygenation.

Abstract: An implantable medical device (IMD) includes an electrode that forms a first snap-fit attachment area and an insulator that forms a through-hole, a second snap-fit attachment area and a third snap-fit attachment area. The second snap-fit attachment area mates with the first snap-fit attachment area of the electrode. The IMD further includes a body including an elongated conductive housing and a feedthrough wire extending therefrom. The body forms a fourth snap-fit attachment area on one end that mates with the third snap-fit attachment area of the insulator such that the feedthrough wire extends through the through-hole of the insulator. The housing encloses at least one of a battery, a sensor, and an electronic circuit. The insulator functions to electrically isolate the electrode from the housing of the body.

Abstract: An optical sensor for a medical device includes a fixed lens spacing between emit and receive modules to achieve target sensor sensitivity, while varying other sensor parameters in order to increase signal amplitude without increasing power demand. The size of at least one of emit and receive module lenses of an optical sensor, and the offset between the opto-electronic component and the respective lens of at least one of emit and receive modules is decreased to increase amplitude of the signal received by the receive module from the emit module.

Abstract: An implanted system includes at least two optical sensors implanted proximate to an artery of a patient such that one optical sensor is upstream of another optical sensor. Arterial pulses of the patient may be detected based on electrical signals from at least one of the optical sensors. In addition, electrical signals from the optical sensors may be used to minimize the effects of motion artifacts on the detection of arterial pulses. For example, a detected pulse may be determined to be a spurious pulse if the optical sensors indicate the occurrence of the pulse within a predetermined range of time. As another example, a first optical sensor signal may be shifted in time relative to a second optical sensor signal, and the signals may be correlated. An arterial pulse may be detected at a time at which a peak or trough amplitude value of the correlated signal is observed.

Abstract: An implantable medical device having an optical sensor selects the function of modular opto-electronic assemblies included in the optical sensor. Each assembly is provided with at least one light emitting device and at least one light detecting device. A device controller coupled to the optical sensor controls the function of each the assemblies. The controller executes a sensor performance test and selects at least one of the plurality of assemblies to operate as a light emitting assembly in response to a result of the performance test. The controller selects at least one other of the plurality of optical sensor assemblies to operate as a light detecting assembly in response to a result of the performance test.

Abstract: An implantable optical sensor and associated manufacturing method include a sensor housing having an inner surface and an outer surface and a window formed in the housing extending between the housing inner surface and the housing outer surface. An opto-electronic device enclosed within the housing and having a photonic surface is operatively positioned proximate the window for emitting light through the window or detecting light through the window. An optical coupling member is positioned between the opto-electronic device and the window for reducing light reflection at a surface within the implantable optical sensor.

Abstract: An implantable medical device system and associated method monitor changes in transimpedance in a body tissue due to changes in cardiac pulsatility. A first dipole is used to deliver a non-stimulating electrical current. The first dipole includes a first electrode and a second electrode adapted to be deployed along a first body location. A second dipole is used to measure a voltage resulting from the non-stimulating electrical current being conducted through a portion of a patient's body. The second dipole includes a third electrode and a fourth electrode different than the first electrode and the second electrode and adapted to be deployed along a second body location spaced apart from the first body location.

Abstract: This disclosure is directed to an implantable medical device having a communication dipole configured in accordance with the techniques described herein. In one example, the disclosure is directed to an implantable medical device comprising a housing that encloses at least a communication module, a first electrode of a communication dipole electrically coupled to the communication module and an electrically conductive fixation mechanism that is electrically coupled to a portion of the housing and wherein a portion of the fixation mechanism is configured to function as at least part of a second electrode of the communication dipole. The electrically conductive fixation mechanism includes a dielectric material that covers at least part of a surface of the fixation mechanism. The communication module is configured to transmit or receive a modulated signal between the first electrode and second electrode of the communication dipole.

Abstract: A first concentration of a chromophore corresponding to a measurement volume of an optical sensor is determined. A second concentration of the chromophore is obtained in the vicinity of the measurement volume corresponding to a change in at least one of a total concentration of the chromophore and a relative concentration of a first form of the chromophore to the total concentration of the chromophore in the measurement volume. Light remittance measurements including a first light wavelength and a second light wavelength are obtained corresponding to the first chromophore concentration and the second chromophore concentration. A coefficient for computing an index of a change in the chromophore concentration is computed using the difference between the first and second chromophore concentrations and the first and second light remittance measurements.

Abstract: Implantable systems and methods (e.g., using an implantable medical device) for measuring distance including a transmit/receive acoustic transducer implantable at a first location for transmitting and receiving acoustic signals, an echo acoustic transducer implantable at a second location for receiving the acoustic signal from the transmit/receive acoustic transducer and in response thereto transmitting a return echo signal to be received by the transmit/receive acoustic sensor, and a controller to control transmission of the acoustic signal from the transmit/receive acoustic transducer at a transmit time and determine a receive time corresponding to the time the transmit/receive acoustic transducer receives the return echo signal. The distance between the transmit/receive acoustic transducer and the echo acoustic transducer is determined as a function of the transmit time and the receive time.

Abstract: Implantable medical devices and methods include an optical sensor that includes at least two optical sensor portions. The light emitting devices of the optical sensor are distributed among the at least two optical sensor portions.

Abstract: Aspects of the present disclosure include a medical device system including an implantable medical device and an external device with three or more electrodes configured to contact a patient's skin. The external device either transmits or receives a test signal to or from the implantable medical device using a plurality of possible receive dipoles, where each possible receive dipole is formed by a pair of electrodes. A signal quality monitor, either at the implantable medical device or at the external device, measures a signal quality for the possible receive dipoles.

Abstract: A medical device for sensing cardiac events that includes a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor generates an ambient light measurement in response to ambient light detected by the detector, generates a plurality of light measurements in response to the emitted light detected by the detector, and adjusts the plurality of light measurements in response to the ambient light measurement.

Abstract: An implantable medical device system including an optical sensor monitors for the presence of overgrowth on the sensor by sensing light scattered by a measurement volume, the sensed light corresponding to a first wavelength, and deriving an overgrowth metric in response to the sensed light. The overgrowth metric is correlated to the presence of overgrowth on the sensor and is compared to a predetermined threshold. The presence of overgrowth on or near the sensor is detected in response to the overgrowth metric crossing the threshold.

Abstract: A medical device for sensing cardiac events that includes a plurality of electrodes sensing cardiac signals utilized to identify a cardiac event, a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor determines a plurality of light measurements in response to the emitted light detected by the detector, and generates a blood volume index in response to a light source of the plurality of light sources emitting light at an isobestic wavelength. The blood volume index is then utilized to verify the identifying of the cardiac event.

Abstract: An implantable medical device system and associated method monitor changes in transimpedance in a body tissue due to changes in cardiac pulsatility. A first dipole is used to deliver a non-stimulating electrical current. The first dipole includes a first electrode and a second electrode adapted to be deployed along a first body location. A second dipole is used to measure a voltage resulting from the non-stimulating electrical current being conducted through a portion of a patient's body. The second dipole includes a third electrode and a fourth electrode different than the first electrode and the second electrode and adapted to be deployed along a second body location spaced apart from the first body location.

Abstract: A medical device for sensing cardiac events that includes a plurality of electrodes sensing cardiac signals utilized to identify a cardiac event, a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor determines a plurality of light measurements in response to the emitted light detected by the detector, an isobestic blood volume index in response to determined light measurements of the plurality of light measurements from a first light source of the plurality of light sources emitting light at an isobestic wavelength, determines an oxygen index associated with light measurements of the plurality of light measurements from a light source of the plurality of light sources other than the first light source, and verifies the identifying of the cardiac event in response to the determined isobestic blood volume index and the determined oxygen index.

Abstract: A medical device system for sensing cardiac events that includes a plurality of electrodes sensing cardiac signals utilized to identify a cardiac event, a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor determines a plurality of light measurements in response to the emitted light detected by the detector, determines changes in perfusion in response to first changes in the plurality of light measurements in a direction indicative of a decrease in blood oxygenation and second changes in a direction indicative of a decrease in blood volume, and adjusts delivery of therapy by the device in response to the determined loss of perfusion.

Abstract: An optical sensor for a medical device includes a fixed lens spacing between emit and receive modules to achieve target sensor sensitivity, while varying other sensor parameters in order to increase signal amplitude without increasing power demand. An optical sensor connected to a housing of a medical device includes a circuit board, an opto-electronic component, a wall, a lens, and a ferrule. The circuit board is arranged within the housing. The opto-electronic component is mounted on a surface of the circuit board. The wall protrudes from the surface of the circuit board and surrounds the opto-electronic component. The lens is offset from the surface of the circuit board. The ferrule is connected to the housing, the lens and the wall. An inner surface of the wall mates with an outer surface of the ferrule.