Abstract: Techniques are provided for tracking patient respiration based upon intracardiac electrogram signals or other electrical cardiac signals. Briefly, respiration patterns are detected by integrating cardiac electrical signals corresponding to individual paced cardiac cycles. The integrals may be obtained between consecutive pairs of ventricular pacing pulses or between consecutive pairs of atrial pacing pulses. In either case, cyclical changes in the integrals of the individual cardiac cycles are tracked. The cyclical changes are representative of respiration. Once respiration patterns have been identified, episodes of abnormal respiration, such as apnea, hyperpnea, nocturnal asthma, or the like, may be detected and therapy automatically delivered.

Abstract: Techniques are provided for detecting the onset of an episode of apnea/hypopnea substantially in real-time. A moving threshold is generated based on recent respiration cycles and differences are accumulated between amplitudes of new respiration cycles and the moving threshold. Apnea/hypopnea is then detected based upon a comparison of the accumulated differences against a fixed threshold. The technique exploits the fact that many episodes of hypopnea begin with a sharp drop in respiration and many episodes of apnea are preceded by a sharp drop in respiration. By accumulating differences between new respiration amplitudes and a short term moving average, any sharp drop in respiration is thereby promptly detected. In many cases, by the time the amplitudes of individual respiration cycles drop to levels directly indicative of apnea/hypopnea, the episode of apnea/hypopnea will have already been detected based upon the sudden sharp drop in respiration amplitude and therapy will have already been initiated.

Abstract: Improved methods and devices perform respiratory control of a person due to conditions such as sleep apnea. According to one embodiment, a respiratory control method includes delivering stimulation signals according to one or more stimulation parameters to phrenic nerves of a person. The person's chest activity is monitored, e.g., by sensing signals in a chamber of the person's heart, to determine the person's respiratory cycle. The stimulation cycle and respiratory cycle are compared. In response, the one or more stimulation parameters are adjusted. In subsequent stimulation cycle(s), the method delivers the stimulation signals according to the adjusted stimulation parameters. This feedback mechanism may continue until respiratory control is captured.

Abstract: Techniques are provided for controlling therapy delivered in response to Cheyne-Stokes Respiration (CSR) or other forms of periodic breathing in an effort to reduce the likelihood of unnecessary therapy directed toward preventing sleep interruption. Following each burst of respiration during CSR, a prediction is made as to whether the amount of respiration achieved during the burst will be sufficient to sustain the patient through a period of apnea until the next respiration burst. If not, aggressive therapy, such as aggressive diaphragmatic pacing, is delivered to improve respiration and prevent the imminent sleep interruption. If, however, the amount of respiration achieved during the burst appears to be sufficient to sustain the patient until the next respiration burst, then relatively mild therapy is instead delivered.

Abstract: In one implementation, a method is provided for detecting heart failure which includes retrieving a three-dimensional posture template corresponding to a normal evoked response. The method further includes capturing an intracardiac electrogram of an evoked response and detecting a three-dimensional posture corresponding with the intracardiac electrogram. The detected three-dimensional posture and the three-dimensional posture template are compared. The captured intracardiac electrogram is used for heart failure trend analysis if the comparison of the detected three-dimensional posture and the three-dimensional posture template indicates a same posture.

Abstract: A diagnostic gauge for cardiac health is described. Multiple parameters pertaining to a patent's cardiac health are distilled to a single diagnostic vector having an angle and a magnitude. The diagnostic vector is plotted on a Cartesian graph to form a visual gauge that provides a general assessment of the patient's cardiac health given the underlying parameters. This allows care providers to diagnose more quickly a patient's cardiac health through observation of the gauge without having to review all of the measured parameters. Additionally, the diagnostic gauge can be used to screen for those patient's with conditions that require more immediate attention. A trend of the diagnostic vectors can also be developed and plotted to reveal changes in the patient's cardiac health over time.

Abstract: Diagnosing a patient's cardiac health through the use of parameter change analysis involves a system that includes an implantable cardiac device to sense a parameter related to a patient's heart. The system further includes a parameter change detection sub-system configured to derive a trend of the parameter over time and to detect changes to the trend. The trend and detected changes can then be used to diagnose changes in the patient's cardiac health. Results of the diagnosis are stored and presented to a care physician.

Abstract: An implantable cardiac stimulation device treats apnea with either phrenic nerve stimulation pulses or cardiac stimulation pulses. The device includes an apnea detector that detects apnea of a patient, a blood oxygen saturation monitor that measures a blood oxygen saturation level of the patient responsive to detection of apnea, and a tiered therapy circuit that provides phrenic nerve stimulation pulses if the measured blood oxygen saturation level is within a first range and cardiac stimulation pulses if the measured blood oxygen saturation level is within a second range. The cardiac stimulation pulses are preferably provided in a DAO pacing mode.

Abstract: An exemplary method includes delivering stimulation according to one or more stimulation parameters to cause contraction of the diaphragm, monitoring chest activity related to respiration and, in response to the monitoring, adjusting one or more of the one or more stimulation parameters during contraction of the diaphragm and continuing the delivering. Various other exemplary methods, devices, systems, etc., are also disclosed.

Abstract: An exemplary method includes determining a parameter related to CO2 concentration in a patient's blood, as well as determining a parameter related to respiration of the patient. The parameters are then processed to diagnose a cardiac condition based at least in part on the parameters.

Abstract: An implantable medical device which has a sensor that provides a waveform to an energy accumulator, such as a capacitor. The waveform is representative of electrical activity from a nerve. The implantable medical device further includes a threshold detector which provides a discrete output signal when the energy in the signal energy accumulator exceeds a threshold. The signal energy accumulator can be periodically discharged and then recharged during the time period that electrical activity is being sensed from the nerve thereby generating a number of discrete output signals each time the recharged energy accumulator exceeds the threshold. The frequency and number of pulsed outputs is indicative of the sensed electrical activity.

Abstract: An implantable cardiac device is programmed to differentiate between central sleep apnea and obstructive sleep apnea. The implantable cardiac device utilizes a respiration-related parameter (e.g., respiration rate, tidal volume, and minute ventilation) to determine whether the patient is experiencing an episode of sleep apnea. When sleep apnea is detected, the implantable cardiac device examines the intracardiac electrogram (IEGM) to classify the apnea as either central sleep apnea or obstructive sleep apnea. The cardiac device may be further configured to administer different therapies depending upon the classification of sleep apnea.

Abstract: An implantable cardiac stimulation device comprises a physiologic sensor and one or more pulse generators. The physiologic sensor is capable of sensing a physiologic parameter. The pulse generators can generate cardiac pacing pulses with a timing based on the physiologic parameter. The timed cardiac pacing pulses can prevent a sleep apnea condition. In one example, a cardiac stimulation device has a physiologic sensor and can be configured to pace a patient's heart according to a rest mode of operation. The cardiac stimulation device uses measurements from the physiologic sensor to prevent and treat sleep apnea using a revised rest mode of operation. The revised rest mode operates under a presumption that sleep apnea is primary to a reduced heart rate, rather than secondary, so that pacing at a rate higher than the natural cardiac rate during sleep will prevent sleep apnea.

Abstract: Techniques are provided for detecting the circadian state of a patient using an implantable medical device based on selected blood carbon dioxide (CO2) parameters. In one example, the implantable device tracks changes in end tidal CO2 (etCO2) levels and changes in maximum variations of pCO2 levels per breathing cycle (?cycleCO2) over the course of the day and determines the circadian state based thereon. It has been found that average etCO2 levels are generally highest and average ?cycleCO2 levels are generally lowest while a patient is asleep and opposite while a patient is awake. Hence, by tracking changes in average etCO2 and ?cycleCO2 levels over the course of the day, circadian states can be detected. Minute ventilation and activity levels are used to assist in the determination of the circadian state. Additional techniques are directed to detecting the stage of sleep.

Abstract: An implantable cardiac device having an impedance monitor has an impedance monitoring control. The impedance monitor includes a pulse generator that applies a current between a pair of implanted electrodes and an impedance measuring circuit that measures impedance across the implanted electrodes and provides an impedance signal during a present time that the pulse generator applies the current between the pair of implanted electrodes. The impedance monitoring control processes the impedance signal to provide impedance monitoring characteristic results and compares the results to preset standards. A control circuit varies the operating parameters of the impedance monitor responsive to the comparison of the impedance monitoring characteristic results to the present standards.

Abstract: Techniques are provided for detecting non-obstructive forms of apnea within a patient using an implantable medical system based on changes in blood pressure. The implantable system monitors for any substantially uniform decease in diastolic blood pressure over a series of heartbeats. If the uniform decease is sustained from beat to beat over a sufficient period of time, typically only ten seconds, non-obstructive apnea is deemed to have commenced and appropriate therapy may then be delivered. Preferably, however, therapy is only delivered if the episode of apnea is corroborated based on thoracic impedance signals, accelerometer signals or the like. In this manner, an episode of non-obstructive apnea can be promptly and reliably detected, thus allowing for prompt delivery of therapy.

Abstract: Techniques are provided for detecting and tracking heart failure based on heart rate, rest rate and activity levels. Briefly, histograms are generated based on rest-rate adjusted heart rate values and corresponding activity level values. Heart failure is then detected and tracked based on an analysis of the histogram. In one example, so long as the activity level of the patient exceeds some minimum threshold, the ratio of adjusted heart rate to activity level is periodically calculated and resulting values are stored in a histogram. Each day, the histogram is compared against a previous histogram to detect any overall trend. For example, the centroid of the histogram can be calculated each day with any changes in the centroid values used to track progression of heart failure.

Abstract: Time-varying spatial signals are detected by accelerometers mounted within the patient. The signals, representative of the actual 3-D trajectory of the patient, are compared with information representative of expected trajectories retrieved from memory to identify a current patient posture, which may be either a dynamic posture such as walking or running or a change in posture such as rising from a seated position to a standing position. In this manner, a change in posture of the patient is identified based upon a full 3-D trajectory, rather than merely the orientation of the patient at the beginning and the end of the change in posture. In an example described herein, the implantable device stores information representative of expected 3-D trajectories in the form of pre-calculated comparison matrices derived from orthonormal kernels employing Laguerre functions or Lagrange functions.

Abstract: Time-varying spatial signals are detected by accelerometers mounted within the patient. The signals, representative of the actual 3-D trajectory of the patient, are compared with information representative of expected trajectories retrieved from memory to identify a current patient posture, which may be either a dynamic posture such as walking or running or a change in posture such as rising from a seated position to a standing position. In this manner, a change in posture of the patient is identified based upon a full 3-D trajectory, rather than merely the orientation of the patient at the beginning and the end of the change in posture. In an example described herein, the implantable device stores information representative of expected 3-D trajectories in the form of pre-calculated comparison matrices derived from orthonormal kernels employing Laguerre functions or Lagrange functions.

Abstract: Techniques are provided for distinguishing Cheyne-Stokes Respiration (CSR) caused by central sleep apnea (CSA) from CSR caused by congestive heart failure (CHF) and for evaluating the severity of CHF, if present, based up CSR. A time period associated with the CSR is determined based upon separate evaluation of apnea and hyperpnea periods during CSR and then the time period is compared against a time-varying discrimination threshold derived from integrated thoracic impedance signals. If the time period exceeds the threshold, the CSR of the patient is caused by CHF; otherwise, the CSR is caused by CSA. Thereafter, the course of therapy delivered to the patient is controlled based upon the type of CSR. In addition, if the CSR is caused by CHF, the time period associated with CSR is employed to determine the severity of CHF—with longer time periods being associated with more severe CHF.