Temperature monitoring for sleep disordered breathing

Abstract

Systems and methods for determining sleep disordered breathing parameters of a patient are disclosed, including receiving respiration information of the patient and temperature information of the patient, and determining sleep disordered breathing parameters of the patient using the received respiration information and temperature information of the patient.

Description

[0001] CLAIM OF PRIORITY

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 085,889, filed September 30, 2020, which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] The present invention relates generally to monitoring sleep disordered breathing, and more particularly but not exclusively to systems and methods for temperature monitoring of sleep disordered breathing. BACKGROUND

[0004] Ambulatory medical devices (AMDs) include implantable, wearable, external, or one or more other types of medical devices having sensors configured to sense a patient physiological signal. The detected physiological signal can be used to determine or monitor a patient status or condition. Frequent patient monitoring, such as using one or more AMDs, can enable early detection of deteriorating patient conditions or identification of patients or groups of patients at high risk of future adverse events, including hospitalization. Early detection of deteriorating patient conditions can prevent or reduce patient hospitalization. Identifying and safely managing the risk of patient condition deterioration can reduce patient hospitalization, the number or severity of medical interventions, and overall medical costs.

[0005] Sleep disordered breathing (SDB) describes a group of chronic conditions characterized by abnormalities or insufficiencies in breathing during sleep, ranging from snoring or partial cessation of breathing to sleep apnea, temporary cessation of breathing during sleep. Typical SDB symptoms include loud snoring or labored breathing during sleep, including short periods of no breathing followed by gasping or nasal discharge, night sweats or frequent use of the bathroom during sleep. SDB patients often suffer from daytime sleepiness and fatigue, poor concentration and memory, and reduced quality of life. In addition, SDB is a common but often undiagnosed comorbidity in heart failure (HF) patients or patients with cardiovascular disease. Once sleep apnea is confirmed, SDB itself is classified as a disease.

[0006] There are two main types of sleep apnea: obstructive sleep apnea (OSA) and central sleep apnea (CSA). OSA is complete or partial obstruction of the upper airway during sleep, usually occurring when the muscles at the back of the throat relax, causing the patient's airway to become completely or partially blocked, requiring the patient's chest muscles and diaphragm to work even harder to force air through the blocked airway. CSA is cessation of ventilation, usually repetitive, not due to airway obstruction, but due to a lack of ventilatory effort, i.e., the patient's brain fails to send appropriate signals to the respiratory muscles.

[0007] Other forms of SDB include hypopneas, which are characterized by abnormally shallow or slow breathing, and Cheyne-Stokes respiration, which is an abnormal breathing pattern that includes periods of gradually deepening followed by shallow periods, sometimes leading to temporary cessation. SUMMARY

[0008] Systems and methods for determining a sleep disordered breathing parameter of a patient are disclosed, including receiving respiration information of the patient and temperature information of the patient, and determining the sleep disordered breathing parameter of the patient using the received respiration information and temperature information of the patient.

[0009] A subject (e.g., system) of an example (e.g., "Example 1") can include means for receiving respiration information of a patient and temperature information of the patient, and means for determining a sleep disordered breathing parameter of the patient using the received respiration information and temperature information of the patient.

[0010] In Example 2, the subject of Example 1 can optionally be configured such that the means for receiving respiration information includes a signal receiver circuit configured to receive the respiration information of the patient and the temperature information of the patient, and the means for determining the sleep disordered breathing parameter includes an evaluation circuit configured to determine the sleep disordered breathing parameter of the patient using the received respiration information and the received temperature information of the patient.

[0011] In Example 3, the subject of any one or more of Examples 1-2 can optionally be configured such that the respiration information includes impedance information of the patient indicative of a tidal volume of the patient, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a decrease from a baseline respiration measure of the detected received impedance information via a detection window, the decrease being greater than a sleep disordered breathing threshold.

[0012] In Example 4, the subject matter of any one or more of Examples 1-3 can optionally be configured such that the temperature information comprises a temperature of an implantable housing of the medical device system that is indicative of a distal skin temperature of the patient, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a combination of the received impedance information via the detection window and the temperature of the implantable housing corresponding to the detection window.

[0013] In Example 5, the subject matter of any one or more of Examples 1-4 can optionally be configured such that the evaluation circuit is configured to determine the sleep disordered breathing parameter by using a detected reduction in the received impedance information indicative of a tidal volume of the patient that is greater than a sleep disordered breathing threshold and the temperature of the implantable housing that is greater than a temperature threshold, wherein the sleep disordered breathing parameter comprises an indication that a sleep disordered breathing event has occurred over the detection window, and the evaluation circuit is configured to determine a baseline tidal volume measure using a tidal volume measure determined for the patient over a baseline period that is longer than and precedes the detection window.

[0014] In Example 6, the subject matter of any one or more of Examples 1-5 can optionally be configured such that the detection window has a period between 5 and 15 seconds, and the baseline period is one minute or longer.

[0015] In Example 7, the subject matter of any one or more of Examples 1-6 can optionally be configured such that the evaluation circuit is configured to count a number of sleep disordered breathing events in a daily period.

[0016] In Example 8, the subject matter of any one or more of Examples 1-7 can optionally be configured such that the evaluation circuit is configured to adjust at least one of the sleep disordered breathing threshold or a length of the detection window using the received temperature information.

[0017] In Example 9, the subject matter of any one or more of Examples 1-8 can optionally be configured such that the evaluation circuit is configured to determine an initial sleep disordered breathing parameter for the patient using the received respiration information, and determine a confidence indication for the determined initial sleep disordered breathing parameter using the received temperature information.

[0018] In Example 10, the subject matter of any one or more of Examples 1-9 can optionally be configured such that the confidence indication comprises an indication of a high confidence and a low confidence, and the evaluation circuit is configured to determine the indication of the high confidence if the received temperature information corresponding to the determined initial sleep disordered breathing parameter is at or above a threshold, and determine the indication of the low confidence if the received temperature information corresponding to the determined initial sleep disordered breathing parameter is below the threshold.

[0019] In Example 11, the subject matter of any one or more of Examples 1-10 can optionally be configured to include an implantable medical device including a temperature sensor configured to sense temperature information and a respiration sensor configured to sense respiration information of the patient.

[0020] In Example 12, the subject matter of any one or more of Examples 1-11 can optionally be configured such that the respiration sensor includes an impedance sensor configured to sense an impedance of a chest of the patient and determine respiration information of the patient using changes in the sensed impedance associated with respiration of the patient, wherein the determined respiration information includes a determined tidal volume measure of the patient, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a reduction in the determined tidal volume measure of the patient from a baseline tidal volume measure via a detection window that is greater than a sleep disordered breathing threshold.

[0021] In Example 13, the subject matter of any one or more of Examples 1-12 can optionally be configured such that the temperature sensor is configured to sense a temperature of a housing of the implantable cardiac monitor and determine a distal skin temperature of the patient using the sensed temperature information, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a combination of the determined tidal volume measure of the patient via a detection window and the determined distal skin temperature of the patient corresponding to the detection window.

[0022] The subject matter (e.g., method) of an example (e.g., "Example 14") can include receiving, using a signal receiver circuit, respiration information of a patient and temperature information of the patient, and determining, using an evaluation circuit, a sleep disordered breathing parameter of the patient by using a combination of the received respiration information of the patient and the temperature information of the patient.

[0023] In Example 15, the subject matter of Example 14 can optionally be configured such that the respiration information includes impedance information of the patient indicative of a tidal volume of the patient, the temperature information includes a temperature of an implantable housing of a medical device system indicative of a distal skin temperature of the patient, and determining the sleep disordered breathing parameter of the patient includes using: (1) a reduction in the received impedance information from a baseline respiration measure via a detection window, wherein the reduction is greater than a sleep disordered breathing threshold, and (2) the temperature of the implantable housing corresponding to the detection window.

[0024] The subject matter (e.g., implantable cardiac monitor) of an example (e.g., "Example 16") can include a respiration sensor configured to sense respiration information of a patient, a temperature sensor configured to sense temperature information of the patient, and an evaluation circuit configured to determine a sleep disordered breathing parameter of the patient using the sensed respiration information of the patient and the sensed temperature information of the patient.

[0025] In Example 17, the subject matter of Example 16 can optionally be configured such that the respiration sensor includes an impedance sensor configured to sense an impedance of the patient's chest and use changes in the sensed impedance associated with the patient's respiration to determine the patient's respiration information, the determined respiration information including a determined tidal volume measure of the patient, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a reduction in the determined tidal volume measure of the patient via the detection window from a baseline tidal volume measure, where the reduction is greater than a sleep disordered breathing threshold.

[0026] In Example 18, the subject matter of any one or more of Examples 1-17 can optionally be configured such that the temperature sensor is configured to sense a temperature of a housing of the implantable cardiac monitor and use the sensed temperature information to determine a patient distal skin temperature, and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a combination of the determined tidal volume measure of the patient via the detection window and the determined patient distal skin temperature corresponding to the detection window.

[0027] In Example 19, the subject matter of any one or more of Examples 1-18 can optionally be configured such that the evaluation circuit is configured to determine the sleep disordered breathing parameter using a reduction in the determined tidal volume measure of the patient detected being greater than a sleep disordered breathing threshold and the determined patient distal skin temperature being greater than a temperature threshold, the sleep disordered breathing parameter including an indication that a sleep disordered breathing event has occurred over the detection window, and the evaluation circuit is configured to determine the baseline tidal volume measure using determined tidal volume measures of the patient over a baseline period longer than and preceding the detection window.

[0028] In Example 20, the subject matter of any one or more of Examples 1-19 can optionally be configured such that the detection window has a period between 5 and 15 seconds, and where the baseline period is one minute or longer.

[0029] In Example 21, the subject matter of any one or more of Examples 1-20 can optionally be configured such that the evaluation circuit is configured to count a number of sleep disordered breathing events over a daily period, and the evaluation circuit is configured to adjust at least one of the sleep disordered breathing threshold or a length of the detection window using the sensed temperature information.

[0030] In Example 22, the subject matter of any one or more of Examples 1-21 can optionally be configured such that the evaluation circuit is configured to determine the temperature threshold using a rate of change of the sensed temperature information.

[0031] In Example 23, the subject matter of any one or more of Examples 1-22 can optionally be configured such that the evaluation circuit is configured to: determine an initial sleep disordered breathing parameter of the patient using the sensed respiration information; and determine an indication of confidence of the determined initial sleep disordered breathing parameter using the sensed temperature information.

[0032] In Example 24, the subject matter of any one or more of Examples 1-23 can optionally be configured such that the indication of confidence includes an indication of high confidence and low confidence and the evaluation circuit is configured to: determine the indication of high confidence if the sensed temperature information corresponding to the determined initial sleep disordered breathing parameter is at or above a threshold value; and determine the indication of low confidence if the sensed temperature information corresponding to the determined initial sleep disordered breathing parameter is below the threshold value.

[0033] The subject matter (e.g., a medical device system) of Example (e.g., “Example 25”) can include: signal receiver circuitry configured to receive respiration information of a patient and temperature information of the patient; and evaluation circuitry configured to determine a sleep disordered breathing parameter of the patient using the received respiration information and the temperature information of the patient.

[0034] In Example 26, the subject matter of any one or more of Examples 1-25 can optionally be configured such that the respiration information includes impedance information of the patient indicative of a tidal volume of the patient and the evaluation circuit is configured to: determine the sleep disordered breathing parameter using a decrease in the detected received impedance information from a baseline respiration measure via a detection window, the decrease being greater than a sleep disordered breathing threshold.

[0035] In Example 27, the subject matter of any one or more of Examples 1-26 can optionally be configured such that the temperature information includes a temperature of an implanted housing of the medical device system indicative of a distal skin temperature of the patient and the evaluation circuit is configured to determine the sleep disordered breathing parameter using a combination of the received impedance information via the detection window and the temperature of the implanted housing corresponding to the detection window.

[0036] In Example 28, the subject matter of any one or more of Examples 1-27 can optionally be configured such that the evaluation circuit is configured to: determine the sleep disordered breathing parameter using a decrease in the detected received impedance information indicative of a tidal volume of the patient being greater than a sleep disordered breathing threshold and the temperature of the implanted housing being greater than a temperature threshold, the sleep disordered breathing parameter including an indication that a sleep disordered breathing event has occurred over the detection window, and the evaluation circuit is configured to: determine a baseline tidal volume measure using a tidal volume measure determined for the patient over a baseline period longer than and preceding the detection window.

[0037] In Example 29, the subject matter of any one or more of Examples 1-28 can optionally be configured such that the detection window has a period of between 5 and 15 seconds, the baseline period is one minute or longer, the evaluation circuit is configured to count a number of sleep disordered breathing events in the daily period, and the evaluation circuit is configured to adjust at least one of a sleep disordered breathing threshold or a length of the detection window using the received temperature information.

[0038] In Example 30, the subject matter of any one or more of Examples 1-29 can optionally be configured such that the evaluation circuit is configured to determine an initial sleep disordered breathing parameter of the patient using the received respiration information and determine an indication of confidence of the determined initial sleep disordered breathing parameter using the received temperature information.

[0039] In Example 31, the subject matter of any one or more of Examples 1-30 can optionally be configured such that the indication of confidence includes an indication of high confidence and low confidence and the evaluation circuit is configured to determine the indication of high confidence if the received temperature information corresponding to the determined initial sleep disordered breathing parameter is at or above a threshold value and determine the indication of low confidence if the received temperature information corresponding to the determined initial sleep disordered breathing parameter is below the threshold value.

[0040] The subject matter (e.g., method) of Example (e.g., "Example 32") can include receiving, using signal receiver circuitry, respiration information of a patient and temperature information of the patient, and determining, using evaluation circuitry, a sleep disordered breathing parameter of the patient by using a combination of the received respiration information and temperature information of the patient.

[0041] In Example 33, the subject matter of any one or more of Examples 1-32 can optionally be configured such that the respiration information includes impedance information of the patient indicative of a tidal volume of the patient, the temperature information includes a temperature of an implanted housing of the medical device system indicative of a distal skin temperature of the patient, and determining the sleep disordered breathing parameter of the patient includes using: (1) a decrease from a baseline respiration measure of the received impedance information via the detection window that is greater than a sleep disordered breathing threshold, and (2) a temperature of the implanted housing corresponding to the detection window.

[0042] In Example 34, the subject matter of any one or more of Examples 1-33 can optionally be configured such that determining the sleep disordered breathing parameter includes determining an indication that a sleep disordered breathing event has occurred over a detection window, the method including determining a baseline respiration measure using respiration information for the patient over a baseline period that is longer than and precedes the detection window, counting a number of sleep disordered breathing events for the patient in a daily period, and adjusting at least one of a sleep disordered breathing threshold or a length of the detection window using the received temperature information, wherein the detection window has a period between 5 and 15 seconds and the baseline period is one minute or longer.

[0043] In Example 35, the subject matter of any one or more of Examples 1-34 can optionally be configured such that determining the sleep disordered breathing parameter includes: determining an initial sleep disordered breathing parameter for the patient using the received respiration information; and determining an indication of a confidence in the determined initial sleep disordered breathing parameter using the received temperature information.

[0044] In Example 36, a subject matter (e.g., a system or device) can optionally combine any portion or combination of any portions of Examples 1-35 to include an "apparatus" for performing any portion of the functions or methods of any one or more of Examples 1-35, or at least one "non-transitory machine-readable medium" comprising instructions that, when executed by a machine, cause the machine to perform any portion of the functions or methods of any one or more of Examples 1-35

[0045] This Summary is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the disclosure. The detailed description is included to provide further information about the present patent application. Other aspects will become apparent to those skilled in the art upon consideration of the following detailed description and accompanying drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

[0046] The same numbers can be used in different drawings to depict the same or similar components. Numbers with different letter suffixes can represent different instances of the same components. The drawings have not necessarily been drawn to scale to illustrate the various embodiments discussed herein.

[0047] Figure 1 and Figure 2 An example relationship between aspects of a patient's circadian rhythm system is shown.

[0048] Figure 3 Example respiration information for a patient is shown.

[0049] Figure 4An example system is shown.

[0050] Figure 5 An example patient management system is shown.

[0051] Figure 6 and Figure 7 An example method of determining sleep disordered breathing (SDB) parameters for a patient is shown.

[0052] Figure 8 An example implantable medical device (IMD) is shown.

[0053] Figure 9 A block diagram of an example machine upon which any one or more of the techniques (e.g., methodologies) discussed herein can perform is shown. DETAILED DESCRIPTION

[0054] Sleep disordered breathing (SDB) is associated with several diseases that significantly impact morbidity and mortality. The sudden changes in oxygen flow associated with sleep apnea can place additional stress on the heart and nervous system. Obstructed sleep apnea (OSA) is clinically associated with arterial hypertension, can increase the risk of arrhythmias and stroke, and is very prevalent in patients with type 2 diabetes. SDB is a marker of coronary artery disease and is associated with negative patient outcomes. Heart failure (HF) patients with SDB have a worse prognosis and increased mortality. There is also a large overlap between SDB, HF, and atrial fibrillation (AF) patients.

[0055] Diagnosis of SDB relies heavily on accurate respiration sensing. An example scan algorithm for detecting SDB, such as apneas, looks for periods where the baseline tidal volume (TV) is reduced beyond certain thresholds (e.g., 10 seconds or more, etc.). For example, an AP scan algorithm can detect apnea / hypopnea events as a period of time (10 seconds or more) where the TV is reduced by more than 26% (e.g., TV threshold of 0.74, etc.). Other systems can further distinguish between apneas and hypopneas, and / or monitor snoring or other impediments or sleep disorders to aid in SDB diagnosis. In other examples, one or more other time periods (e.g., 5 to 15 seconds, etc.) or thresholds can be used, or in certain examples, in conjunction with other physiological information. For example, respiration information can be combined with patient activity information to detect SDB, such as described in commonly-assigned Lee et al., U.S. Patent Serial No. 7,469,697, entitled “Feedback System and Method for Sleep Disordered Breathing Therapy,” which is incorporated herein by reference in its entirety.

[0056] Once a cessation of respiration is identified, a stimulus can be delivered to interfere with the onset, such as a stimulation to the brain or one or more neural pathways, to muscle tissue of the airway, etc., to cause the patient to resume normal respiration, or one or more other notifications can be provided to the patient or a clinician or other caregiver associated with the patient.

[0057] Ambulatory medical devices (AMDs) can be divided into two different groups: (1) external or wearable medical devices; and (2) implantable medical devices (IMDs), such as implantable cardiac monitors (ICMs), etc. These differences can be significant in terms of power consumption, storage, communication, and patient compliance. Implantable medical devices can have access to different physiological information, require different levels of signal and noise processing, and require little or no patient compliance (they cannot be forgotten), but cannot be as easily replaced or charged as external or wearable medical devices. Furthermore, communication outside of the body can be more challenging than equivalent communication outside of the body. It is important to provide continuous monitoring when detecting brief intermittent physiological information throughout the day. For example, SDB onset can be as little as a few seconds, with a typical detection window in the range of 10 seconds out of 86,400 seconds in a day. Furthermore, it can be important to detect SDB onset during time periods or in locations that are not typically associated with nighttime sleep, such as during daytime naps, during travel, etc. Thus, there are significant differences between implantable and external medical devices.

[0058] AMDs, including ICMs (e.g., pacemakers, implantable cardiac defibrillators (ICDs), etc.), can include respiration sensors, such as impedance sensors configured to sense patient respiration for TV or minute volume (MV) measurements, e.g., using changes in impedance measurements, etc. However, dynamic respiration sensing can be challenging as artifacts associated with patient motion, body position changes, or other disturbances affect the accuracy of dynamic respiration sensing. For example, a certain amount of reduction in TV detected using an ICM is due to artifacts (e.g., motion artifacts, etc.) rather than a reduction in respiration. Accordingly, the inventors have recognized, among other things, a need for more reliable and accurate detection of patient respiration information in AMDs, such as ICMs, with respect to SDB events.

[0059] The inventors have recognized that SDB significantly impairs natural sleep-wake patterns and circadian system function. Unstable, fragmented sleep reduces the stability of the natural temperature rhythm. SDB patients typically exhibit higher daytime (wake) distal skin temperature (DST) and lower nighttime (sleep) DST than healthy patients. Patient DST is typically associated with the implant location for a conventional IMD or ICM housing (e.g., subcutaneously at an upper chest location of the patient, typically below the clavicle). Changes in patient core body temperature (CBT), patient temperature of internal organs such as the heart, are typically opposite to changes in patient DST. As used herein, daytime and nighttime are used to refer to patient wake and sleep periods, respectively, and not necessarily to refer to predetermined times of day (e.g., 10pm to 8am, etc.).

[0060] AMDs can include temperature sensors, such as thermistors or resistance-based temperature sensors, thermocouples, or one or more other electrical circuits configured to measure temperature information of the AMD or a patient associated with the AMD. In certain examples, a temperature sensor of an ICM or other IMD can be located inside a hermetically sealed housing of the implanted device, isolated or in direct contact with the housing, or in other examples, located outside the housing and having components in direct or close contact with body tissue. An ICM temperature sensor can accurately measure temperature, such as at the implant site (e.g., subcutaneously, etc.), with an accuracy of 0.1 °F, etc. Depending on the implant site, ICM temperature can reflect patient skin temperature when it is located at or near the outer surface of the patient, such as subcutaneously implanted at the patient’s chest, etc.

[0061] The inventors have further recognized that using measurements of patient temperature, such as patient DST, to monitor circadian rhythms can be used to increase the accuracy of dynamic respiration sensing for SDB detection relative to using AMD, such as single device ICM systems. Since many ICM systems include temperature sensors, incorporating measurements of patient temperature, such as patient DST measurements using a temperature sensor located on or within an ICM, with existing ICM respiration sensing can improve the accuracy of existing SDB detection, thereby improving the performance of existing devices without requiring additional sensors or data sources.

[0062] In certain examples, an ICM using one or more control or analysis circuits can be configured to use measured ICM temperature to estimate patient sleep state. In certain examples, a high ICM temperature relative to patient daily temperature variation can indicate that the patient is in a sleep state, while a low ICM temperature relative to patient daily temperature variation can indicate that the patient is in an awake state. In addition, ICM temperature measurements can be used to indicate patient sleep quality or patient health. Such determination of patient sleep state, quality, or patient health based on ICM temperature measurements can be used to increase the confidence of detected respiration changes (reductions in TV) to, such as avoid false detection of SDB when the patient is awake.

[0063] Accurate sleep detection using patient temperature information in a medical system can significantly improve SDB detection performance. In one example, traditional SDB detection using respiration information (e.g., 10 seconds with a TV threshold of 0.74) provides positive predictive value (PPV) and negative predictive value (NPV) of 0.882 and 0.769, respectively, while the addition of sleep detection using patient temperature information is able to increase the PPV and NPV to 0.941 and 0.846, respectively, which is a significant improvement.

[0064] Figure 1 and Figure 2 Example relationships 100, 200 between patient circadian system aspects are shown. Figure 1 An example relationship 100 between patient circadian system aspects is shown for a single daily period (12pm to 12pm), including relative changes in patient core body temperature (CBT) 101, sleep propensity 102, and melatonin level 103 shown relative to patient sleep period 104. Figure 2 An example relationship 200 between healthy patient distal skin temperature (DST) 201 and SDB patient DST 202 is shown for a single daily period (12pm to 12pm) relative to patient sleep period 204.

[0065] Patient body temperature regulation is strongly related to the sleep-wake cycle. Patient CBT 101 decreases before and during patient sleep period 104, while healthy patient DST 201 and SDB patient DST 202 increase before and during patient sleep period 204. The onset of patient sleep period 104, 204 tends to coincide with the maximum rate of decrease of patient CBT 101, the increase in melatonin levels 103, and the increase in healthy patient DST 201 and SDB patient DST 202. Sleep is difficult when distal skin areas (e.g., hands, feet, etc.) are cold. Warmer distal skin areas promote heat loss at the core and corresponding rapid sleep onset.

[0066] Figure 2 Absolute daily changes (increments) in healthy patient DST 201 as healthy DST changes 205 and SDB patient DST 202 as SDB DST changes 206 are shown. Healthy DST changes 205 are typically more pronounced (greater) than SDB DST changes 206. Healthy patients 201 typically exhibit lower daytime (wake) DST and higher nighttime (sleep) DST with greater rates of increase and decrease at the transition between sleep and wake periods and throughout the day. In certain examples, measures of patient DST, such as changes in absolute daily changes or rates of increase and decrease of daily patient DST, daily maximum temperatures, daily minimum temperatures, daily between-temperature variability, within- daily temperature variability, sleep time relative to wake time, etc., can be used to determine indications of SDB.

[0067] In certain examples, healthy patient DST 201 and SDB patient DST 202 above a temperature threshold 207 can indicate patient sleep period 204. Temperature threshold 207 can be determined using temperature information for the patient. In examples, temperature threshold 207 can be set to a temperature that is a preset level (e.g., percentage) about a previous daily temperature range, a measure of one or more previous days, etc. In other examples, temperature threshold 207 can be set using a rate of change of temperature information alone, or after a particular time of day, or based on clinician input or other parameters.

[0068] Not only can the DST change provide an indication of whether the patient is sleeping, but it can also provide an indication of sleep quality or patient health. While activity information can provide an indication of patient location and movement associated with whether the patient is in bed, the change in DST can indicate that the patient health condition is improving or declining independent of patient sleep time. Thus, patient temperature information can provide clinically valuable information beyond that received from typical activity or location sensors. Trends (increasing or decreasing) in daily changes in one or more measures of patient DST can indicate changing patient status, vitality, disease progression or recovery, treatment or treatment efficacy, etc. One or more deteriorating measures of patient DST can be an early indication of arrhythmia, stroke, HF, worsening disease state, etc. Thus, an indication using one or more measures of patient DST or patient deterioration can trigger additional modes, sensing, notifications, or alerts.

[0069] Figure 3 Example respiration information 300 for a patient is shown, including an impedance signal 301 proportional to the amount of air exhaled over an expiratory period 302 and the amount of air inhaled over an inspiratory period 303. The amount of air inhaled and exhaled over the respiration period is proportional to the tidal volume (TV) of the patient. The impedance signal 301 shows a period of normal respiration with intermittent sleep disordered breathing (SDB) episodes 304 having a period of reduced TV greater than a detection window (e.g., 10 seconds).

[0070] Figure 4 An example system 400, such as a medical device system, is shown. In an example, one or more aspects of the example system 400 can be components of, or communicatively coupled to, an ambulatory medical device (AMD), such as an implantable cardiac monitor (ICM). The AMD can be configured to monitor, detect, or treat various physiological conditions of the body, such as cardiac conditions associated with a reduced ability of the heart to sufficiently deliver blood to the body, including heart failure (HF), arrhythmia, hypertension, dyssynchrony, etc., or one or more other physiological conditions, such as sleep disordered breathing (SDB), etc., and, in certain examples, the AMD can be configured to provide electrical stimulation or one or more other therapies or treatments to the patient.

[0071] The system 400 can include a single AMD or multiple AMDs implanted in a patient or otherwise positioned on or about a patient to monitor patient physiological information of the patient using one or more sensors, such as the sensor 401. In examples, the sensor 401 can include one or more of a respiration sensor configured to receive respiration information (e.g., respiration rate, respiration volume (tidal volume), etc.), an acceleration sensor (e.g., accelerometer, microphone, etc.) configured to receive cardiac acceleration information (e.g., cardiac vibration information, pressure waveform information, heart sound information, endocardial acceleration information, acceleration information, activity information, posture information, etc.), an impedance sensor configured to receive impedance information (e.g., intrathoracic impedance sensor, transthoracic impedance sensor, etc.), a cardiac sensor configured to receive electrocardiogram information, an activity sensor configured to receive information regarding body movement (e.g., activity, steps, etc.), a posture sensor configured to receive posture or position information, a pressure sensor configured to receive pressure information, a plethysmography sensor (e.g., optical plethysmography sensor, etc.), a chemical sensor (e.g., electrolyte sensor, pH sensor, anion gap sensor, etc.), a temperature sensor, a cutaneous elasticity sensor, or one or more other sensors configured to receive physiological information of a patient.

[0072] The example system 400 can include a signal receiver circuit 402 and an evaluation circuit 403. The signal receiver circuit 402 can be configured to receive physiological information of a patient (or a group of patients) from one or more sensors 401. The evaluation circuit 403 can be configured to receive information from the signal receiver circuit 402 and determine one or more parameters (e.g., physiological parameters, stratification, etc.) or existing or changing patient conditions (e.g., indication of patient dehydration, respiratory condition, cardiac condition (e.g., HF, arrhythmia), SDB, etc.) using the received physiological information, such as described herein. The physiological information can include, among others, cardiac electrical information, impedance information, respiration information, heart sound information, activity information, posture information, temperature information, chemical information, or one or more other types of physiological information.

[0073] The evaluation circuit 403 can be configured to provide output to a user, such as to a display or one or more other user interfaces, including scores, trends, alerts, or other indications. In other examples, the evaluation circuit 403 can be configured to provide output to another circuit, machine, or process, such as a therapy circuit 404 (e.g., a cardiac resynchronization therapy (CRT) circuit, a chemotherapy circuit, etc.) or the like, to control, adjust, or stop therapy of a medical device, a drug delivery system, or the like, or to otherwise change one or more processes or functions of one or more other aspects of a medical device system, such as one or more CRT parameters, drug delivery, dose determination or recommendations, or the like. In one example, the therapy circuit 404 can include one or more of a stimulation control circuit, a cardiac stimulation circuit, a neural stimulation circuit, a dose determination or control circuit, or the like. In other examples, the therapy circuit 404 can be controlled by the evaluation circuit 403 or one or more other circuits, or the like.

[0074] The AMD can include a series of medical devices, including, for example, a traditional cardiac rhythm management (CRM) device, such as an implantable cardiac monitor (ICM), a pacemaker, a defibrillator, or a cardiac resynchronizer, including an implantable or subcutaneous device with a sealed housing configured to be implanted in a patient's chest. The CRM device can include one or more leads to position one or more electrodes or other sensors at different locations in or near the heart, such as in one or more of the atria or ventricles. Thus, the CRM device can include aspects that are subcutaneous, although proximate to a patient's distal skin, as well as aspects that are proximate to one or more organs of the patient, such as a lead or electrode. Separately from or in addition to the one or more electrodes or other sensors of the lead, the CRM device can include one or more electrodes or other sensors (e.g., pressure sensors, accelerometers, gyroscopes, microphones, etc.) powered by a power source in the CRM device. The one or more electrodes or other sensors of the lead, the CRM device, or a combination thereof, can be configured to detect physiological information from the patient, or to provide one or more therapies or stimuli to the patient.

[0075] An implantable device can additionally or solely include a leadless cardiac pacemaker (LCP), a small (e.g., smaller than a traditional implantable CRM device, in some examples having a volume of about 1 cc, etc.) stand-alone device including one or more sensors, circuits, or electrodes configured to monitor physiological information from the heart (e.g., heart rate, etc.), detect a physiological condition associated with the heart (e.g., tachycardia), or provide one or more therapies or stimuli to the heart without the complications of traditional lead or implantable CRM devices (e.g., required incision and pocket, complications associated with lead placement, breakage, or migration, etc.). In some examples, an LCP can have more limited power and processing capabilities than a traditional CRM device; however, multiple LCP devices can be implanted within or around the heart to detect physiological information from one or more chambers of the heart or provide one or more therapies or stimuli to one or more chambers of the heart. Multiple LCP devices can communicate among themselves or one or more other implantable or external devices.

[0076] Each additional sensor within or associated with an AMD or medical device system can increase system cost and complexity, decrease system reliability, or increase power consumption and decrease the useful life of the AMD. Thus, it can be beneficial to use a single sensor to determine multiple types of physiological information or to use a smaller number of sensors to measure a larger number of different types of physiological data. For example, it can be beneficial to detect atrial cardiac electrical information without a lead or electrode in or in contact with the atrium. Similarly, it can be beneficial to detect accurate respiratory phase information without directly measuring patient airflow.

[0077] Figure 5 An example patient management system 500 and portions of the environment in which the system 500 can operate are shown. The patient management system 500 can perform a series of activities, including remote patient monitoring and diagnosis of disease conditions. Such activities can be performed in the vicinity of a patient 501, such as in the patient's home or office, through a centralized server, such as in a hospital, clinic, or doctor's office, or through a remote workstation, such as a secure wireless mobile computing device.

[0078] The patient management system 500 can include one or more ambulatory medical devices (AMDs), an external system 505, and a communication link 511 that provides communication between the one or more AMDs and the external system 505. The one or more AMDs can include an implantable medical device (IMD) 502 (e.g., an implantable cardiac monitor (ICM), etc.), a wearable medical device 503, or one or more other implantable, leadless, subcutaneous, external, wearable, or AMD configured to monitor, sense, or detect information from a patient 501, determine physiological information about the patient 501, or provide one or more therapies to treat various conditions of the patient 501, such as one or more cardiac or non-cardiac conditions (e.g., dehydration, SDB, etc.).

[0079] In one example, the IMD 502 can include one or more conventional cardiac rhythm management (CRM) or implantable cardiac monitor (ICM) devices implanted in the patient’s chest, such as a pacemaker or defibrillator, having a lead system including one or more transvenous, subcutaneous, or non-invasive leads or catheters to position one or more electrodes or other sensors (e.g., a heart sound sensor) within, on, or around the patient’s 501 heart or one or more other locations in the patient’s chest, abdomen, or neck. In another example, the IMD 502 can include a monitor implanted subcutaneously in the patient’s 501 chest, for example, where the IMD 502 includes a housing containing circuitry, and in certain examples, one or more sensors, such as a temperature sensor, etc.

[0080] The IMD 502 can include evaluation circuitry configured to detect or determine certain physiological information of the patient 501, or determine one or more conditions, or provide information or alerts to a user, such as the patient 501 (e.g., a patient), a clinician, or one or more other caregivers or processes. The IMD 502 can alternatively or additionally be configured as a therapy device configured to treat one or more medical conditions of the patient 501. The therapy can be delivered to the patient 501 via the lead system and associated electrodes or using one or more other delivery mechanisms. The therapy can include delivery of one or more drugs to the patient 501 using the IMD 502 or one or more other AMDs. In some examples, the therapy can include CRT for correcting dyssynchrony and improving cardiac function in CHF patients. In other examples, the IMD 502 can include a drug delivery system, such as a drug infusion pump, to deliver a drug to the patient for managing arrhythmias or complications resulting from arrhythmias, hypertension, or one or more other physiological conditions. In other examples, the IMD 502 can include one or more electrodes configured to stimulate the nervous system of the patient or provide stimulation to muscles of the patient’s airway, etc.

[0081] The wearable medical device 503 can include one or more wearable or external medical sensors or devices (e.g., an automatic external defibrillator (AED), a Holter monitor, a patch-based device, a smartwatch, a smart accessory, a wrist- or finger-worn medical device such as a finger-based photoplethysmography sensor, etc.). The wearable medical device 503 can include an optical sensor configured to detect a PPG signal on a wrist, finger, or other location of the patient 501. In other examples, the wearable medical device 503 can include an acoustic sensor or accelerometer to detect acoustic information (e.g., heart sounds) or vibrations of blood flow, an impedance sensor to detect impedance changes associated with blood flow or volume changes, a temperature sensor to detect temperature changes associated with detecting blood flow, a laser Doppler vibrometer or other pressure, strain, or physical sensor to detect body changes associated with blood flow, etc.

[0082] The external system 505 can include a dedicated hardware / software system such as a programmer, a remote server-based patient management system, or alternatively a system defined primarily by software running on a standard personal computer. The external system 505 can manage the patient 501 through the IMD 502 or one or more other AMDs connected to the external system 505 via a communication link 511. In other examples, the IMD 502 can be connected to the wearable device 503 or the wearable device 502 can be connected to the external system 505 via the communication link 511. This can include, for example, programming the IMD 502 to perform one or more of acquiring physiological data, performing at least one self-diagnostic test (such as for device operational status), analyzing the physiological data to detect cardiac arrhythmias, or optionally delivering or adjusting therapy to the patient 501. In addition, the external system 505 can send information to or receive information from the IMD 502 or the wearable device 503 via the communication link 511. Examples of information can include real-time or stored physiological data from the patient 501, diagnostic data such as detecting a hydration status of the patient, inpatient therapy, a response to therapy delivered to the patient 501, or a device operational status of the IMD 502 or the wearable device 503 (e.g., battery status, lead impedance, etc.). The communication link 511 can be an inductive telemetry link, a capacitive telemetry link, or a radio frequency (RF) telemetry link, or wireless telemetry based on, for example, a “strong” Bluetooth or IEEE 802.11 wireless fidelity “Wi-Fi” interface standard. Other configurations and combinations of patient data source interfaces are also possible.

[0083] By way of example and not limitation, external systems 505 can include external devices 506 located in proximity to one or more AMDs, and remote devices 508 located at a location relatively remote from one or more AMDs to communicate with external devices 506 via a communication network 507. Examples of external devices 506 can include medical device programmers.

[0084] Remote devices 508 can be configured to evaluate collected patient or patient information and provide alert notifications, among other possible functions. In one example, remote devices 508 can include a centralized server that acts as a central hub for collected data storage and analysis. The server can be configured as a single, multi, or distributed computing and processing system. Remote devices 508 can receive data from multiple patients. The data can be collected by one or more AMDs and other data acquisition sensors or devices associated with patients 501. The server can include storage devices to store the data in a patient database. The server can include alert analyzer circuitry to evaluate the collected data to determine if a particular alert condition is met. Satisfaction of an alert condition can trigger the generation of an alert notification, such as provided by one or more human perceptible user interfaces. In some examples, alert conditions can alternatively or additionally be evaluated by one or more AMDs, such as IMDs. For example, alert notifications can include web page updates, phone or pager calls, emails, SMS, text or "instant" messages, as well as messages to patients and direct notifications to emergency services and clinicians. Other alert notifications are possible. The server can include alert prioritizer circuitry configured to prioritize alert notifications. For example, a similarity measure between physiological data associated with a detected medical event and physiological data associated with historical alerts can be used to prioritize alerts for detected medical events.

[0085] Remote devices 508 can additionally include one or more locally configured clients or remote clients securely connected to the server over communication network 507. Examples of clients can include personal desktops, laptops, mobile devices, or other computing devices. System users, such as clinicians or other qualified medical experts, can use the clients to securely access patient data stored in the database in the server and select and prioritize patients and alerts for healthcare provisioning. In addition to generating alert notifications, remote devices 508 including the server and interconnected clients can also execute follow-up protocols by sending follow-up requests to one or more AMDs, or by sending messages or other communications to patients 501 (e.g., patients), clinicians, or authorized third parties as compliance notifications.

[0086] The communication network 507 can provide wired or wireless interconnection. In one example, the communication network 507 can be based on a Transmission Control Protocol / Internet Protocol (TCP / IP) network communication specification, although other types or combinations of networking implementations are possible. Similarly, other network topologies and arrangements are possible.

[0087] One or more of the external devices 506 or remote devices 508 can output a detected medical event to a system user, such as a patient or clinician, or to a process including, for example, an instance of a computer program executable in a microprocessor. In one example, the process can include an automatic generation of a recommendation for anti-arrhythmic therapy, or a recommendation for further diagnostic testing or therapy. In one example, the external devices 506 or remote devices 508 can include a respective display unit for displaying physiological or functional signals, or an alert, alarm, emergency call, or other form of warning to signal detection of an arrhythmia. In some examples, the external system 505 can include an external data processor configured to analyze physiological or functional signals received by one or more AMDs and confirm or reject detection of an arrhythmia. Computationally intensive algorithms, such as machine learning algorithms, can be implemented in the external data processor to retrospectively process data to detect arrhythmias.

[0088] One or more of the AMDs or portions of the external system 505 can be implemented using hardware, software, firmware, or combinations thereof. One or more of the AMDs or portions of the external system 505 can be implemented using special-purpose circuitry that can be structured or configured to perform one or more functions, or can be implemented using general-purpose circuitry that can be programmed or otherwise configured to perform one or more functions. Such general-purpose circuitry can include a microprocessor or a portion thereof, a microcontroller or a portion thereof, or programmable logic circuitry, memory circuitry, network interfaces, and various components for interconnecting these components. For example, a “comparator” can include an electronic circuit comparator that can be structured to perform the specific function of a comparison between two signals, or the comparator can be implemented as a portion of general-purpose circuitry that can be driven by code instructing the portion of general-purpose circuitry to perform the comparison between two signals. A “sensor” can include an electronic circuit configured to receive information and provide an electronic output representative of such received information.

[0089] The patient management system 500 can include a therapy device 510, such as a respiratory therapy device (e.g., a continuous positive airway pressure device or a nebulizer device, etc.) or a drug delivery device configured to provide therapy or therapy information (e.g., dose information, etc.) to the patient 501, such as by using information from one or more AMDs. In other examples, one or more AMDs can be configured to provide therapy or therapy information to the patient 501. The therapy device 510 can be configured to send information to or receive information from one or more AMDs or external system 505 using a communication link 511. In one example, one or more AMDs, external device 506, or remote device 508 can be configured to control one or more parameters of the therapy device 510.

[0090] The external system 505 can allow for programming of one or more AMDs and can receive information about one or more signals acquired by one or more AMDs, such as can be received via the communication link 511. The external system 505 can include a local external IMD programmer. The external system 505 can include a remote patient management system, which can monitor patient status or adjust one or more therapies, such as from a remote location.

[0091] The assessment circuitry can be implemented at the external system 505, which can be configured to perform HF risk stratification, such as by using data extracted from one or more AMDs or data stored in memory within the external system 505. Portions of the HF risk stratification or other assessment circuitry based on chronic conditions of the patient can be distributed between one or more AMDs and the external system 505.

[0092] Figure 6 And Figure 7 Example methods 600, 700 of determining sleep disordered breathing (SDB) parameters for a patient are shown. At 601, respiratory information for a patient can be received, such as a measure or indication of tidal volume (TV) from a respiratory sensor (e.g., a chest impedance based respiratory sensor, etc.). In certain examples, a patient respiratory baseline can be determined using received respiratory information over a baseline period prior to a detection window. In examples, the baseline period can include a period of one minute or more. In other examples, the baseline period can be longer. In certain examples, the patient respiratory baseline can include a daily respiratory baseline, a short term respiratory baseline for a few days (e.g., 1-3 days, etc.) in the past of the patient, or a long term respiratory baseline for a few weeks (e.g., 1-3 weeks, etc.) in the past of the patient. In other examples, the patient respiratory baseline can be determined specifically for a detected or scheduled awake or sleep period (e.g., a short term overnight respiratory baseline, etc.).

[0093] At 602, temperature information for a patient can be received, such as a measure of temperature from a temperature sensor. In certain examples, a patient temperature profile can be determined, including one or more parameters indicative of the patient's thermoregulation throughout the day. The one or more parameters can include a daily temperature increment, a rate of temperature increase or decrease, or one or more parameters indicative of a change in the daily temperature increment or rate of temperature increase or decrease over time.

[0094] At 603, SDB parameters for the patient can be determined, such as by an evaluation circuit using one or more medical device components, such as an implantable cardiac monitor (ICM) or the like. In certain examples, the patient temperature information (e.g., ICM temperature) can be combined with or used to enhance SDB detection using patient respiration information, such as to reduce false SDB detections or more accurately classify borderline SDB detections or provide a confidence indication of an SDB determination. False positive SDB detections can occur during daytime or wake hours where a measure of respiration information is low (e.g., TV threshold of 0.74), such as due to noise, artifact, or the like. In certain examples, patient temperature information can be used to confirm or reject borderline SDB detections using respiration information (e.g., a reduction in patient respiration at or near an SDB threshold). In examples, SDB detection can be gated using temperature information, such that SDB detection does not occur during periods of low ICM temperature or distal skin temperature. In other examples, one or more SDB thresholds can be adjusted using temperature information. For example, SDB thresholds can be adjusted during periods of low ICM temperature (e.g., TV of 0.70-0.74 or lower).

[0095] In certain examples, a probability of the patient experiencing an SDB episode (p(SDB)) can be determined as a function of an SDB probability (p(SDB|TV)) determined using respiration information (e.g., a reduction in TV over a period of time relative to a baseline) and a sleep state probability (p(insleep|temp)) determined using temperature information (e.g., ICM temperature information for a period of time related to a thermoregulatory cycle) adjusted by one or more coefficients (e.g., A).

[0096] p(SDB) = p(SDB|TV) x A(p(insleep|temp)) (1)

[0097] In examples, SDB events can be detected when p(SDB) exceeds a threshold. In certain examples, a number of SDB events can be counted or determined, such as for a sleep session, or a determination of sleep quality can be determined using a number of periods (e.g., 10 second periods) with p(SDB) above a threshold, such as using an evaluation circuit. In certain examples, one or more detected SDB episodes can be used to trigger additional patient monitoring, change a mode in one or more implantable or ambulatory medical devices associated with a patient, such as increasing a number or resolution of physiological sensors, increasing a resolution or storage period of physiological information, triggering patient feedback, etc. In certain examples, one or more medical devices can reduce one or more sampling or storage parameters to reduce power consumption and increase device battery life if no indication of SDB is determined.

[0098] Figure 7 An example method 700 of augmenting a determined initial sleep disordered breathing (SDB) parameter of a patient is shown. At 701, respiration information of a patient can be received. At 702, an initial SDB parameter of the patient can be determined, such as by using an evaluation circuit of one or more medical device components and the received respiration information. At 703, temperature information of the patient can be received, such as a measure of temperature from a temperature sensor associated with a distal skin temperature (DST) of the patient. At 704, the initial SDB parameter can be augmented using the received temperature information.

[0099] In other examples, the received temperature information can be used to adjust respiration sensing of the patient, such as gating received respiration information for SDB detection or increasing or decreasing a sampling rate or type of detected respiration information to reduce power consumption for SDB detection during low patient DST or normal DST variation. For example, in certain examples, a lower power consumption than a tidal volume measurement can be used to detect a respiration rate. Thus, the temperature information can be used to switch between certain respiration sensing or turn on and off, such as to conserve power or avoid false positives. Further, a detection frequency or sampling rate can be adjusted to detect a higher resolution of respiration information or detect respiration information more frequently based on the received temperature information, such as to conserve power during low DST when the patient is less likely to be asleep, etc.

[0100] In examples, the initial SDB parameter can include a conventional SDB parameter determined using respiration information. The initial SDB parameter can be augmented, such as by using patient temperature information to provide a confidence indication of the initial SDB parameter or one or more SDB detections based on the respiration information. For example, a decrease in TV above a threshold at a high ICM temperature can be indicated as a high confidence SDB or apnea event, while a decrease in TV above a threshold at a low ICM temperature can be indicated as a low confidence SDB or apnea event.

[0101] In certain examples, SDB can perturb thermal regulation. Thus, in certain examples, temperature information alone, or changes in temperature information, can be used to determine an indication of SDB. For example, a deviation from a patient's long-term baseline can indicate a change in patient status. A decrease in daily patient temperature variation can indicate a higher likelihood of SDB or a negative change in patient status or sleep state. In other examples, a combination of respiration information and temperature information can be used to determine a probability measure of SDB (p(SDB)) during sleep periods and out-of-sleep periods, where sleep periods and out-of-sleep periods are determined using temperature information:

[0102] p(SDB) = p(SDB | in sleep) x p(in sleep) + p(SDB | out of sleep) (1 - p(in sleep)) (2)

[0103] In other examples, temperature information or changes in temperature information can be used to adjust one or more other SDB metrics, such as a TV threshold, a time window associated with a TV threshold (e.g., a 10 second window can be decreased by 1 or more seconds if received temperature information indicates that the patient is asleep; a 10 second window can be increased by 1 or more seconds if received temperature information indicates that the patient is awake), etc. In other examples, one or more other respiration measures can be used instead of or in addition to a TV threshold (e.g., a mid-term baseline (MTBL) of minute ventilation (MV) information, etc.).

[0104] Figure 8 An example IMD 800 is shown electrically coupled to the heart 805, such as by one or more leads, a first lead 835, a second lead 836, or a third lead 837 coupled to the IMD 800, such as through a lead port 815 (such as a first, second, or third lead port 816, 817, 818 in a header 802 of the IMD 800). In examples, the IMD 800 can include an antenna (such as in the header 802) configured to enable communication with external systems, such as the external system 605 shown. Figure 6 The external system 605 shown.

[0105] The IMD 800 can include an implantable medical device (IMD), such as an implantable cardiac monitor (ICM), a pacemaker, a defibrillator, a cardiac resynchronizer, or other subcutaneous IMD configured to be implanted in a subject's chest with one or more leads to position one or more electrodes or other sensors at different locations in or near the heart 805, such as in one or more of the atria or ventricles. Separately from or in addition to the one or more electrodes or other sensors of the leads, the IMD 800 can include one or more electrodes or other sensors (e.g., pressure sensors, accelerometers, gyroscopes, microphones, etc.) powered by a power source in the IMD 800. The one or more electrodes or other sensors of the leads, the IMD 800, or a combination thereof can be configured to detect physiological information from the patient or provide one or more therapies or stimuli to the patient.

[0106] The implantable device can additionally include a leadless cardiac pacemaker (LCP), a small (e.g., smaller than a traditional implantable device, in certain examples having a volume of about 1 cc, etc.) stand-alone device including one or more sensors, circuits, or electrodes configured to monitor physiological information from the heart (e.g., heart rate, etc.), detect physiological conditions associated with the heart (e.g., tachycardia), or provide one or more therapies or stimuli to the heart 805 without the complications of traditional leads or implantable devices (e.g., required incision and pocket, complications associated with lead placement, breakage, or migration, etc.). In certain examples, the LCP can have more limited power and processing capabilities than a traditional CRM device; however, multiple LCP devices can be implanted within or around the heart to detect physiological information from one or more chambers of the heart or provide one or more therapies or stimuli to one or more chambers of the heart. The multiple LCP devices can communicate among themselves or one or more other implantable or external devices.

[0107] The IMD 800 can include one or more monitoring or therapy devices, such as a subcutaneously implanted device, a wearable external device, a neurostimulator, a drug delivery device, a biological therapy device, or one or more other ambulatory medical devices. The IMD 800 can be coupled to or can be replaced by a monitoring medical device such as a bedside or other external monitor.

[0108] IMD 800 can include a hermetically sealed can (CAN) 801, which can house electronic circuitry that can sense physiological signals in heart 805 and that can deliver one or more therapeutic electrical pulses to a target area, such as in the heart, such as through one or more leads 108A-108C (e.g., first, second, and third leads 835, 836, 837). In certain examples, CRM system 800 can include only a single lead, such as second lead 836, or can include only two leads, such as first and second leads 835, 836.

[0109] The first lead 835 can include a proximal end that can be configured to connect to the IMD 800 and a distal end that can be configured to be placed at a target location such as the right atrium (RA) 831 of the heart 805. The first lead 835 can have a first pacing sensing electrode 841 that can be located at or near the distal end thereof, and a second pacing sensing electrode 842 that can be located at or near the electrode 841. The first and second pacing sensing electrodes 841 and 842 can be electrically connected to the IMD 800, such as via separate conductors in the first lead 835, such as to allow sensing of right atrial activity and optional delivery of atrial pacing pulses. The second lead 836 can be a defibrillation lead that can include a proximal end that can be connected to the IMD 800 and a distal end that can be placed at a target location such as the right ventricle (RV) 832 of the heart 805. The second lead 836 can have a first pacing sensing electrode 852 located at the distal end, a second pacing sensing electrode 853 that can be located proximate the first pacing sensing electrode 852, a first defibrillation coil electrode 854 that can be located proximate the second pacing sensing electrode 853, and a second defibrillation coil electrode 855 that can be located at a distance from the distal end, such as for superior vena cava (SVC) placement. The first, second, and third pacing sensing electrodes 852-855 can be electrically connected to the IMD 800, such as via separate conductors in the second lead 836. The first and second pacing sensing electrodes 852 and 853 can allow sensing of ventricular electrograms and can optionally allow delivery of one or more ventricular pacing pulses, and the first and second defibrillation coil electrodes 854 and 855 can allow delivery of one or more ventricular cardioversion / defibrillation pulses. In an example, the second lead 836 can include only three electrodes: the first, second, and third electrodes 852, 854, 855. The first and second electrodes 852 and 854 can be used for sensing or delivering one or more ventricular pacing pulses, and the first and second electrodes 854 and 855 can be used for delivering one or more ventricular cardioversion or defibrillation pulses. The third lead 837 can include a proximal end that can be connected to the IMD 800 and a distal end that can be configured to be placed at a target location in the left ventricle (LV) 834 of the heart 805. The third lead 837 can be implanted through the coronary sinus 833 and can be placed in a coronary vein over the LV so as to allow delivery of one or more pacing pulses to the LV. The third lead 837 can include a first electrode 861 that can be located at the distal end of the third lead 837, and a second electrode 862 that can be located proximate the first electrode 861. The first and second electrodes 861 and 862 can be electrically connected to the IMD 800, such as via separate conductors in the third lead 837, so as to allow sensing of LV electrograms and optionally allow delivery of one or more resynchronization pacing pulses from the LV.

[0110] IMD 800 can include electronic circuitry that can sense a physiologic signal. The physiologic signal can include an electrocardiogram or a signal representative of the mechanical function of heart 805. CAN 801 can be used as an electrode, such as for sensing or pulse delivery. For example, electrodes from one or more of the leads can be used with CAN 801, such as for unipolar sensing of an electrocardiogram or for delivery of one or more pacing pulses. Defibrillation electrodes from second lead 836 can be used with CAN 801, such as for delivery of one or more cardioversion / defibrillation pulses. In an example, IMD 800 can sense impedance between electrodes, such as between electrodes located on CAN 801 or one or more of the leads. IMD 800 can be configured to inject a current between a pair of electrodes, sense a resultant voltage between the same or a different pair of electrodes, and determine impedance using Ohm’s Law. The impedance can be sensed in a bipolar point configuration (where the same pair of electrodes can be used for current injection and voltage sensing), a tripolar point configuration (where a pair of electrodes for current injection and a pair of electrodes for voltage sensing can share a common electrode), or a quadripolar point configuration (where the electrodes for current injection can be different from the electrodes for voltage sensing). In an example, IMD 800 can be configured to inject a current between an electrode on second lead 836 and CAN 801, and sense a resultant voltage between the same electrode or between a different electrode on second lead 836 and CAN 801. The physiologic signal can be sensed from one or more physiologic sensors that can be integrated within IMD 800. IMD 800 can also be configured to sense a physiologic signal from one or more external physiologic sensors or one or more external electrodes that can be coupled to IMD 800. Examples of physiologic signals can include one or more of the following: heart rate, heart rate variability, intrathoracic impedance, intracardiac impedance, arterial pressure, pulmonary artery pressure, RV pressure, LV coronary artery pressure, coronary artery blood temperature, blood oxygen saturation, one or more heart sounds, physical activity or exertion level, physiologic response to activity, posture, respiration, body weight, or body temperature.

[0111] The arrangements and functions of these leads and electrodes are described by way of example and not by way of limitation. Other arrangements and uses of these leads and electrodes are possible depending on the needs of the patient and the capabilities of the implantable device.

[0112] An external system can allow for programming of IMD 800 and can receive information regarding one or more signals obtained by IMD 800, such as via a communication link using an antenna and telemetry circuitry. The external system can include a local external IMD programmer. The external system can include a remote patient management system, which can monitor patient status or adjust one or more therapies, such as from a remote location.

[0113] The communication link can provide for the transfer of data between the IMD 800 and an external system. Data transmitted can include, for example, real-time physiological data acquired by the IMD 800, physiological data acquired by the IMD 800 and stored therein, therapy history data, or data stored in the IMD 800 indicative of the operational status of the IMD, one or more programming instructions for the IMD 800, such as to configure the IMD 800 to perform one or more actions, including physiological data acquisition (such as using programmably specified sensing electrodes and configurations), device self-diagnostic testing, or delivery of one or more therapies.

[0114] Portions of the IMD 800 or external system can be implemented using hardware, software, or any combination of hardware and software. Portions of the IMD 800 or external system can be implemented using application specific circuitry that can be constructed or configured to perform one or more particular functions, or can be implemented using general purpose circuitry that can be programmed or otherwise configured to perform one or more particular functions. Such general purpose circuitry can include a microprocessor or a portion thereof, a microcontroller or a portion thereof, or programmable logic circuitry or a portion thereof. For example, a “comparator” can include an electronic circuit comparator that can be constructed to perform the specific function of comparing between two signals, or can include a comparator that can be implemented as a portion of general purpose circuitry that can be driven by code instructing the portion of general purpose circuitry to perform the comparison between two signals, among other examples. Although described with reference to the IMD 800, the CRM system 800 can include a subcutaneous medical device (e.g., a subcutaneous ICD, a subcutaneous diagnostic device), a wearable medical device (e.g., a patch-based sensing device), or other external medical device.

[0115] Figure 9 A block diagram of an example machine 900 is illustrated upon which any one or more of the techniques (e.g., methodologies) discussed herein can perform. Portions of the description can be applicable to a computing framework of one or more medical devices described herein (e.g., IMDs, external programmers, etc.). Moreover, as described herein with respect to medical device components, systems, or machines, this can entail regulatory compliance that general purpose computers, components, or machines can not possess.

[0116] As described herein, examples can include or can operate by logic or a number of components of machine 900 or a mechanism, electrical circuitry (e.g., processing circuitry, evaluation circuitry, etc.). Electrical circuitry is a physical, tangible entity that embodies a set of circuits that are implemented in a tangible entity of machine 900, including hardware (e.g., simple circuits, gates, logic, etc.). Electrical circuitry components can be flexible over time and present different

[0117] In alternative embodiments, machine 900 can operate as a standalone device or can be connected (e.g., networked) to other machines. In a networked deployment, machine 900 can operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, machine 900 can act as a peer machine in peer-to-peer (P2P) (or other distributed) network environment. Machine 900 can be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations.

[0118] The machine (e.g., computer system) 900 can include a hardware processor 902 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 904, a static memory (e.g., memory or storage for firmware, microcode, a basic- input-output (BIOS), a unified extensible firmware interface (UEFI), etc.) 906, and a mass storage 908, some or all of which can communicate with one another via an interlink (e.g., bus) 930. The machine 900 can further include a display unit 910, an alphanumeric input device 912 (e.g., a keyboard), and a user interface (UI) navigation device 914 (e.g., a mouse). In an example, the display unit 910, input device 912 and UI navigation device 914 can be a touch screen display. The machine 900 can additionally include a signal generation device 918 (e.g., a speaker), a network interface device 920, and one or more sensors 916, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The machine 900 can include an output controller 928, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).

[0119] The processor 902, the main memory 904, the static memory 906, or the mass storage 908 can be or include machine-readable media 922 on which is stored one or more sets of data structures or instructions 924 (e.g., software) embodying any one or more of the techniques or functions described herein. The instructions 924 can also reside, completely or at least partially, within the processor 902, the main memory 904, the static memory 906, or the mass storage 908 during execution thereof by the machine 900, the processor 902, the main memory 904, the static memory 906, or the mass storage 908. In an example, one or any combination of the hardware processor 902, the main memory 904, the static memory 906, or the mass storage 908 can constitute machine-readable media 922. While the machine-readable medium 922 is illustrated as a single medium, the term “machine-readable medium” can include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) configured to store the one or more instructions 924.

[0120] The term“machine-readable medium” can include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 900 and that cause the machine 900 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting machine-readable medium examples can include solid-state memories, optical media, magnetic media, and signals (e.g., radio frequency signals, other optical-based signals, audio- based signals, etc.). In one example, a non-transitory machine-readable medium includes a machine-readable medium with a plurality of particles having invariant (e.g., rest) mass, and thus is a composition of matter. Accordingly, a non-transitory machine-readable medium is a machine-readable medium that is not a transitory propagating signal. Specific examples of non-transitory machine-readable media can include nonvolatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read Only Memory (EPROM), Electrically Erasable Programmable Read Only Memory (EEPROM)) and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

[0121] The instructions 924 can further be transmitted or received over a communications network 926 using a transmission medium via the network interface device 920 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks can include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, a peer-to-peer (P2P) network, among others. In one example, the network interface device 920 can include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 926. In one example, the network interface device 920 can include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term“transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying the instructions for execution by the machine 900, and includes digital or analog communications signals or other intangible media to facilitate communication of such software. Transmission media can be tangible or intangible. The instructions 924 can further be transmitted or received over a communications network 926 using a transmission medium via the network interface device 920 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks can include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, a peer-to-peer (P2P) network, among others. In one example, the network interface device 920 can include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 926. In one example, the network interface device 920 can include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term“transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying the instructions for execution by the machine 900, and includes digital or analog communications signals or other intangible media to facilitate communication of such software. Transmission media can be tangible or intangible.

[0122] ​Various embodiments are illustrated in the above figures. One or more features from one or more of these embodiments can be combined to form other embodiments. The method examples described herein can be at least partially machine or computer-implemented. Some examples can include a computer- readable medium or machine-readable medium encoded with instructions operable to configure an electronic device or system to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level languages code, or the like. Such code can include computer readable instructions for performing various methods. The code can form portions of computer program products. Further, the code can be tangibly embodied in one or more volatile or non-volatile computer-readable media during execution.

[0123] The above detailed description is intended to illustrate, but not limit, the scope of the disclosure. Thus, the scope of the disclosure should be determined by reference to the appended claims, along with their full scope of equivalents.

Claims

1. A medical device system, comprising: A device for receiving patients' respiratory and temperature information; as well as A device for determining sleep apnea parameters of a patient using respiratory and temperature information received from the patient. The device for receiving respiratory information includes a signal receiver circuit configured to receive the patient's respiratory information and the patient's temperature information. The device for determining sleep apnea parameters includes an assessment circuit configured to determine the patient's sleep apnea parameters using received respiratory and temperature information. The respiratory information includes patient impedance information that indicates the patient's tidal volume. The evaluation circuit is configured to determine the sleep-disorder parameter from a decrease in a baseline breathing measure using received impedance information detected via a detection window, wherein the decrease is greater than a sleep-disorder threshold. The temperature information includes the temperature of the implantable housing of the medical device system, which indicates the distal skin temperature of the patient. The evaluation circuit is configured to determine the sleep apnea parameters using impedance information received via the detection window and a combination of this information and the temperature of the implantable housing corresponding to the detection window. The evaluation circuit is configured to adjust at least one of the sleep-disorder threshold or the length of the detection window using the received temperature information.

2. The medical device system according to claim 1, wherein, The evaluation circuit is configured to determine the sleep apnea parameters using a detected decrease in received impedance information indicating the patient's tidal volume that is greater than the sleep apnea threshold and a temperature of the implanted housing that is greater than a temperature threshold. The sleep apnea parameters include an indication that a sleep apnea event has occurred on the detection window, and The evaluation circuit is configured to determine a baseline tidal volume measurement using a tidal volume measurement determined by the patient during a baseline period longer than the detection window and prior to the detection window.

3. The medical device system according to claim 2, wherein, The detection window has a time period of 5 to 15 seconds. The baseline time period is one minute or longer.

4. The medical device system according to claim 2, wherein, The evaluation circuit is configured to count several sleep-disorder events during daily time periods.

5. The medical device system according to claim 1, wherein, The evaluation circuit is configured as follows: The received respiratory information is used to determine the patient's initial sleep apnea parameters; and The received temperature information is used to determine the confidence level indication of the initial sleep apnea parameters.

6. The medical device system according to claim 5, wherein, The confidence level indication includes high confidence and low confidence indications, and The evaluation circuit is configured as follows: If the received temperature information corresponding to the determined initial sleep apnea parameter is at or above a threshold, a high-confidence indication is determined; and If the received temperature information corresponding to the determined initial sleep apnea parameter is lower than the threshold, a low confidence indication is determined.

7. The medical device system according to any one of claims 1 to 6, comprising: An implantable medical device, including a temperature sensor configured to sense the temperature information; as well as A respiratory sensor configured to sense the patient's respiratory information.

8. The medical device system according to claim 7, wherein, The respiratory sensor includes an impedance sensor configured to sense the impedance of the patient's chest cavity and use changes in the sensed impedance associated with the patient's breathing to determine the patient's respiratory information. The determined respiratory information includes the determined tidal volume measurement of the patient, and The evaluation circuit is configured to determine the sleep apnea parameter by using a determined tidal volume measure of the patient detected via a detection window from a decrease in the baseline tidal volume measure, wherein the decrease is greater than a sleep apnea threshold.

9. The medical device system according to claim 8, wherein, The temperature sensor is configured to: sense the temperature of the housing of the implantable cardiac monitor and use the sensed temperature information to determine the patient's distal skin temperature, and The evaluation circuit is configured to determine the sleep apnea parameters using a combination of a determined tidal volume measurement of the patient via the detection window and a determined distal skin temperature of the patient corresponding to the detection window.

10. A method performed by a medical device system, comprising: The evaluation circuit uses a combination of the patient's respiratory and temperature information received by the signal receiver circuit to determine the patient's sleep apnea parameters. The respiratory information includes patient impedance information that indicates the patient's tidal volume. The temperature information includes the temperature of the implantable housing of the medical device system, which indicates the distal skin temperature of the patient, and The determination of the patient's sleep apnea parameters includes using: (1) a reduction in received impedance information detected via a detection window from a baseline respiratory measure, wherein the reduction is greater than a sleep apnea threshold, and (2) the temperature of the implanted housing corresponding to the detection window. The method further includes adjusting at least one of the sleep-disorder threshold or the length of the detection window using the received temperature information.

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