Abstract: This disclosure is directed to the synchronization of clocks of a secondary implantable medical device (IMD) to a clock of a primary IMD. The secondary IMD includes a communications clock. The communications clock may be synchronized based on at least one received communications pulse. The secondary IMD further includes a general purpose clock different than the communications clock. The general purpose clock may be synchronized based on at least one received power pulse. The communications clock may also be synchronized based on the at least one received power pulse.

Abstract: An implantable medical device includes a hermetically sealed housing and a first light emitting diode (LED) enclosed within the housing configured to detect light corresponding to a selected light wavelength. A conductive element extends from the LED for carrying a current signal corresponding to the light detected by the LED, the intensity of the detected light being correlated to a change in a physiological condition in a body fluid volume or a tissue volume proximate the LED.

Abstract: A pressure sensing system provides signals representative of a magnitude of pressure at a selected site. A sensor module includes a first transducer producing a first signal having an associated first response to pressure and strain applied to the sensor module and a second transducer producing a second signal having an associated second response to pressure and strain applied to the sensor module. A calculated pressure, a bending pressure error and a bend-compensated pressure are computed in response to the first signal and the second signal.

Abstract: An implantable medical sensor system provides signals representative of a magnitude of moment fraction applied to a sensor module at a selected site. A sensor module includes a first transducer producing a first signal having an associated first response to pressure and strain applied to the sensor module and a second transducer producing a second signal having an associated second response to pressure and strain applied to the sensor module. A moment fraction is computed in response to the first signal and the second signal. In various embodiments, the moment fraction is used to guide positioning of the sensor module, indicate a need for repositioning the sensor module, report loading of the sensor module during normal operation for use as sensor design information and in setting sensor calibration ranges.

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: 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: Various techniques are described for periodically performing a calibration routine to calibrate a low-power system clock within an implantable medical device (IMD) based on a high accuracy reference clock also included in the IMD. The system clock is powered continuously, and the reference clock is only powered on during the calibration routine. The techniques include determining a clock error of the system clock based on a difference between frequencies of the system clock and the reference clock over a fixed number of clock cycles, and adjusting a trim value of the system clock to compensate for the clock error. Calibrating the system clock with a delta-sigma loop, for example, reduces the clock error over time. This allows accurate adjustment of the system clock to compensate for errors due to trim resolution, circuit noise and temperature.

Abstract: This disclosure relates to fault tolerant instantiations of a cardiac therapy delivery device such as an implantable cardiac stimulator (e.g., an implantable pulse generator, IPG, and/or an implantable cardioverter-defibrillator, ICD) coupled to an implantable physiologic sensor (IPS). According to the disclosure delivery of cardiac pacing and/or cardioversion-defibrillator therapy delivery can cause errors in output signals from an IPS. Resolution of such errors involves selectively energizing (or disconnecting the output signal from) the IPS during pacing and/or defibrillation therapy delivery. Programmable signal “blanking” in lieu of or in addition to the foregoing also improves the integrity of the output signal (i.e., continuously energize the IPS and ignore parts of the output signal). An ICD having a transient weakness in an insulated conductor used for the IPS signal can likewise have the IPS de-energized and/or blank the IPS output signal during high voltage therapy delivery.

Abstract: This disclosure is directed to the synchronization of clocks of a secondary implantable medical device (IMD) to a clock of a primary IMD. The secondary IMD includes a communications clock. The communications clock may be synchronized based on at least one received communications pulse. The secondary IMD further includes a general purpose clock different than the communications clock. The general purpose clock may be synchronized based on at least one received power pulse. The communications clock may also be synchronized based on the at least one received power pulse.

Abstract: A radiation-based timer for use in an implantable medical device (IMD) includes a radiation source and a radiation detection circuit. The radiation source emits radiation particles during a process referred to as radioactive decay. The radiation detection circuit detects the radiation particles emitted during the decay process and tracks the number of radiation particles detected. When the number of radiation particles detected reaches a threshold value, a timer signal is generated. In this manner, the radiation-based timer generates a timer signal as a function of the radioactive decay of the radiation source. The timer signal may be used by one or more components of the IMD for any of a number of functions, including as a wakeup trigger for a communications and/or a sensor event.

Abstract: An implantable pressure sensor, which may be incorporated within an implantable medical electrical lead, includes an insulative sidewall, which contains a gap capacitor and an integrated circuit. The insulative sidewall of the pressure sensor includes a pressure sensitive diaphragm portion, and the gap capacitor includes a first electrode plate, which is attached to an interior surface of the diaphragm portion of the sidewall, and a second electrode plate, which is spaced apart from the first electrode plate and coupled to the integrated circuit, which is coupled, through the sidewall, to a supply contact and a ground contact. A conductive layer extends over one of the interior surface of the diaphragm portion of the sidewall and an exterior surface of the diaphragm portion; and the conductive layer is coupled to the ground contact to either shield or ground the first electrode plate.

Abstract: A radiation-based timer for use in an implantable medical device (IMD) includes a radiation source and a radiation detection circuit. The radiation source emits radiation particles during a process referred to as radioactive decay. The radiation detection circuit detects the radiation particles emitted during the decay process and tracks the number of radiation particles detected. When the number of radiation particles detected reaches a threshold value, a timer signal is generated. In this manner, the radiation-based timer generates a timer signal as a function of the radioactive decay of the radiation source. The timer signal may be used by one or more components of the IMD for any of a number of functions, including as a wakeup trigger for a communications and/or a sensor event.

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.

Abstract: An implantable pressure sensor, which may be incorporated within an implantable medical electrical lead, includes an insulative sidewall, which contains a gap capacitor and an integrated circuit. The insulative sidewall of the pressure sensor includes a pressure sensitive diaphragm portion, and the gap capacitor includes a first electrode plate, which is attached to an interior surface of the diaphragm portion of the sidewall, and a second electrode plate, which is spaced apart from the first electrode plate and coupled to the integrated circuit, which is coupled, through the sidewall, to a supply contact and a ground contact. A conductive layer extends over one of the interior surface of the diaphragm portion of the sidewall and an exterior surface of the diaphragm portion; and the conductive layer is coupled to the ground contact to either shield or ground the first electrode plate.

Abstract: A reflectance-type optical sensor includes one or more photodiodes formed in a semiconductor substrate. A well having sidewalls and a bottom is formed in the top surface of the substrate, and a reflective layer is formed on the sidewalls and bottom. A light-emitting diode (LED) is mounted in the well, so that light emitted laterally and rearwardly from the LED strikes the sidewalls or bottom and is redirected in a direction generally perpendicular to the top surface of the substrate. The optical sensor can be fabricated using microelectromechanical systems (MEMS) fabrication techniques.

Abstract: An implantable pressure sensor, which may be incorporated within an implantable medical electrical lead, includes an insulative sidewall, which contains a gap capacitor and an integrated circuit. The insulative sidewall of the pressure sensor includes a pressure sensitive diaphragm portion, and the gap capacitor includes a first electrode plate, which is attached to an interior surface of the diaphragm portion of the sidewall, and a second electrode plate, which is spaced apart from the first electrode plate and coupled to the integrated circuit, which is coupled, through the sidewall, to a supply contact and a ground contact. A conductive layer extends over one of the interior surface of the diaphragm portion of the sidewall and an exterior surface of the diaphragm portion; and the conductive layer is coupled to the ground contact to either shield or ground the first electrode plate.

Abstract: An implantable medical device includes a hermetically sealed housing and a first light emitting diode (LED) enclosed within the housing configured to detect light corresponding to a selected light wavelength. A conductive element extends from the LED for carrying a current signal corresponding to the light detected by the LED, the intensity of the detected light being correlated to a change in a physiological condition in a body fluid volume or a tissue volume proximate the LED.

Abstract: A system and method are provided for estimating blood oxygen saturation independent of optical sensor encapsulation due to placement in blood, where the blood includes a blood flow characteristic of: a relatively low, a stasis, a stagnant value. The method includes determining tissue overgrowth correction factor that includes optical properties of the tissue that cause scattering of the emitted light to a detector and relative amplitudes of the emitted light wavelengths. A corrected time interval measured for infrared light is based on an infrared signal and a corrected time interval for red light is determined by subtracting red light signal due to presence of tissue overgrowth. The red light signal due to tissue overgrowth is proportional to total infrared signal less nominal infrared signal. Oxygen saturation is estimated based on standard calibration factors and the ratio of the corrected infrared time interval and the corrected red time interval.

Abstract: A system and method are provided for accurately estimating blood oxygen saturation independent of tissue encapsulation of the optical sensor. The method includes determining a tissue overgrowth correction factor that accounts for the optical properties of the tissue that cause scattering of the emitted light to a light detector and the relative amplitudes of the emitted light wavelengths. A corrected time interval measured for infrared light is based on an infrared signal returned from fluid with no tissue overgrowth. A corrected time interval for red light is determined by subtracting a red light signal attributed to the presence of tissue overgrowth. The amount of red light signal attributed to the presence of tissue overgrowth is proportional to the total infrared signal less the nominal infrared signal. Oxygen saturation is estimated based on standard calibration factors and the ratio of the corrected infrared time interval and the corrected red time interval.

Abstract: A system and method are provided for accurately estimating blood oxygen saturation independent of tissue encapsulation of the optical sensor. The method includes determining a tissue overgrowth correction factor that accounts for the optical properties of the tissue that cause scattering of the emitted light to a light detector and the relative amplitudes of the emitted light wavelengths. A corrected time interval measured for infrared light is based on an infrared signal returned from fluid with no tissue overgrowth. A corrected time interval for red light is determined by subtracting a red light signal attributed to the presence of tissue overgrowth. The amount of red light signal attributed to the presence of tissue overgrowth is proportional to the total infrared signal less the nominal infrared signal. Oxygen saturation is estimated based on standard calibration factors and the ratio of the corrected infrared time interval and the corrected red time interval.