Sensing for health management

Abstract

In some examples, determining the health state includes using an implantable medical device configured for subcutaneous implantation and including at least one optical sensor. The processing circuit system of the system including the device can determine a current tissue oxygen saturation value for the patient based on a first signal received from the at least one optical sensor, and determine a current pulse oxygen saturation value based on a second signal received from the at least one optical sensor. The processing circuit system can further compare the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding baseline values, determine the patient's corresponding heart failure state and lung state based on the comparison, and determine the patient's health state based on these states.

Description

Technical Field

[0001] The present disclosure relates generally to medical device systems and, more particularly, to medical device systems configured to monitor patient parameters. Background Art

[0002] Certain types of implantable medical devices (IMDs) can be used to monitor one or more physiological parameters of a patient, such as those associated with heart or lung function. Such an IMD may include a sensor that detects signals associated with such physiological parameters (e.g., tissue impedance or oxygen level), or may be part of a system that includes such a sensor. Values ​​determined based on such signals can be used to help detect changes in a medical condition, assess the efficacy of a treatment, or generally assess patient health.

[0003] An implantable device that monitors a physiological parameter related to a patient's medical condition can evaluate a value associated with the physiological parameter, such as to determine whether the value exceeds a threshold or has changed. Exceeding a threshold or changing a value can indicate that a treatment being administered to the patient is not effectively managing the patient's medical condition. Summary of the invention

[0004] In general, the present disclosure relates to techniques for determining the health status of a patient, such as a patient diagnosed with a heart failure condition. Such techniques may include performing assessments associated with various aspects of the patient's cardiac function, pulmonary function, and blood function, and determining the patient's medical profile based on the results of the assessment. Such a medical profile may indicate the patient's heart failure state, pulmonary state, and anemia state (e.g., whether the patient's heart, lung, and blood function are stable or deteriorating), and may help guide treatment selection. Additionally, such an overview may enable a differential diagnosis between two or more of a cardiac condition, a pulmonary condition, and anemia, particularly where these conditions may present similar symptoms.

[0005] After presenting acute heart failure symptoms (such as shortness of breath or dyspnea) at a medical institution, the patient may be initially diagnosed with a heart failure condition. When evaluating the heart failure condition of such patients, clinicians can perform assessments associated with various aspects of the patient's cardiac function (such as preload, afterload, and vascular resistance) by observing alternative parameters. For example, in order to evaluate preload (a measure of the heart's filling capacity), clinicians can observe signs of congestion in the patient, such as peripheral edema, jugular vein distension, peritoneal effusion, or other. In order to evaluate afterload (a measure of cardiac contractility and output), clinicians can observe signs of peripheral insufficiency of perfusion in the patient, such as cold sweats on the extremities, oliguria, confusion, and dizziness. Blood pressure measurements can be used or vascular resistance can be estimated by observing signs of vasoconstriction in the patient (such as numbness and tingling in the extremities). Based on the combined results of these assessments, clinicians can identify the patient's hemodynamic profile (e.g., congestion + adequate perfusion + vasoconstriction), which can represent the type of the patient's heart failure condition.

[0006] In some examples, clinicians can also assess the patient's lung function and blood function to assess the patient's lung disease or anemia, which in some cases may co-morbid with heart failure and may present similar symptoms, such as shortness of breath (dyspnea) or fatigue. In order to assess the patient's lung disease, clinicians can perform assessments associated with various aspects of the patient's lung function (such as arterial oxygenation). For example, clinicians can assess arterial oxygenation by observing the patient's hypoxia surrogate parameter, which can be characterized by cyanosis, shortness of breath, or low pulse oxygen saturation as measured by a pulse oximeter applied to the patient's periphery. In order to assess the patient's anemia, clinicians can perform assessments associated with various aspects of the patient's blood function (such as hemoglobin concentration). In some examples, clinicians can assess hemoglobin concentration by observing the patient's fatigue, weakness, or dizziness surrogate parameters or by observing the results of laboratory blood tests.

[0007] Based on the combined results of these assessments, the clinician can identify the patient's health status (e.g., positive for congestive heart failure and negative for lung disease and anemia) and prescribe treatment based on the patient's health status. For example, such treatment may include medication to compensate for the loss of heart function caused by the patient's heart failure condition. Thereafter, the patient can be discharged from the medical facility with instructions to continue prescribed treatments and schedule regular clinician visits.

[0008] However, due to one or more reasons, one or more of the patient's medical conditions (which may be in a chronic but stable compensated state when adequately managed by treatment) may become unstable and acutely decompensated, i.e., no longer adequately managed by treatment between clinician visits. For example, the progressive nature of heart disease may cause the patient to experience worsening congestion between visits, which may be due to physiological cardiac remodeling and changes in cardiac function that occur in the progression of heart failure. In some examples, the effects of changes in cardiac function associated with progressive heart failure may lead to changes in pulmonary function and / or hematological function. Such changes may be cyclical in nature, such that changes in pulmonary function and / or hematological function caused by worsening cardiac function may in turn cause further worsening of cardiac function.

[0009] For example, the development or worsening of congestion in a patient with a heart failure condition can reduce the ability of the lungs to supply oxygen to the patient's arterial blood, which in turn can lead to tissue hypoperfusion. In some such cases, the patient's body may attempt to compensate for tissue hypoperfusion by increasing vasoconstriction, which in turn can increase congestion, leading to a cycle of worsening heart and lung function. Additionally or alternatively, the development or worsening of congestion and the resulting increase in vasoconstriction can increase the strain on the kidneys, which can lead to the development of renal failure, which in turn can lead to the development of anemia. In some such cases, the patient's body may attempt to compensate for anemia by increasing heart rate, which can increase the strain on the heart, leading to a cycle of worsening heart and blood function.

[0010] In any of these cases, the patient may develop symptoms and acutely decompensate between visits. In some examples, this acute decompensation may lead to hospitalization or other adverse medical events. However, while the patient is receiving treatment for his or her symptoms in a medical facility, the cycle of physiological deterioration may have led to further progression of the patient's heart failure condition or the development of additional medical conditions (such as lung disease or chronic anemia). This effect of decompensation may lead to a decrease in the patient's quality of life or other undesirable clinical outcomes.

[0011] In addition, the evaluation and treatment of patients with acute decompensation of symptoms can be complicated because changes in different physiological functions can each lead to the same symptoms. For example, symptoms of shortness of breath may be caused by any one or more of changes in cardiac function, changes in lung function, or changes in blood function (i.e., anemia). Therefore, it may be desirable to distinguish between shortness of breath caused by worsening anemia and reduced oxygen carrying capacity caused by a decrease in hematocrit, shortness of breath caused by fluid overload (i.e., congestion), and shortness of breath caused by respiratory failure (e.g., chronic obstructive pulmonary disease (COPD)), as each condition can lead to an increased need for oxygen and shortness of breath.

[0012] Continuous monitoring of physiological functions associated with patient conditions (e.g., heart, lungs, and blood) can enable early detection of changes in these physiological functions before they lead to symptoms, acute decompensation, and / or the progression or development of one or more medical conditions. In the case where the patient is still symptomatic, this continuous monitoring can enable identification of the physiological functions whose changes cause symptoms. Therefore, the patient's clinical outcome will benefit from a method of monitoring the patient's cardiac, pulmonary, and blood functions between clinician visits, which in turn can enable prediction of the progression of the disease state and the likelihood that hospitalization may occur, or early identification of the cause of the symptoms. In response to this information, the patient's treatment can be adjusted (e.g., by modifying the drug regimen), which can help reduce the likelihood of acute decompensation, hospitalization, or other medical condition development in the patient.

[0013] However, the assessment of parameters related to cardiac function, pulmonary function, and hematologic function (such as, the assessment of the patient's heart failure status) based on observations of surrogate parameters of congestion (i.e., hypervolemia), peripheral perfusion, and vascular resistance may be limited to a clinical or hospital setting. For example, such an assessment may require medical expertise that is not available to the patient in a non-clinical setting. Therefore, one or more medical devices (such as, the subcutaneous implantable medical devices described herein) may be used to perform a method of updating a patient's hemodynamic profile between clinician visits.

[0014] Therefore, the technology described herein may include automatic detection and monitoring of parameters associated with cardiac function, pulmonary function, and blood function, which can be measured by one or more medical devices that may be subcutaneously implantable and, in some cases, leadless. As with the clinician's assessment, certain values ​​of such parameters may indicate one or more of heart failure, lung disease, and / or anemia. In addition, the technology described herein may advantageously distinguish the potential causes of a given parameter change, thereby distinguishing between, for example, peripheral perfusion changes caused by heart failure conditions and peripheral perfusion changes caused by lung disease. That is, such a technology may identify the potential primary (or differentiated) causes of symptoms that may be caused by one or more of a variety of medical conditions. Therefore, this three-part assessment of the patient's physiological function, when combined together, can provide a reliable indication of the patient's health status, which may be useful in predicting the likelihood of acute decompensation of the patient relative to one or more specific medical conditions and in actively modifying the patient's treatment. Because the methods described herein are intended to be performed between clinician visits by one or more devices of the system, such methods may use electrodes, optical sensors, and / or other sensors to monitor certain parameters of the patient's physiological function, in place of external signs observed by clinicians.

[0015] For example, some of the methods described herein include determining pulse oxygen saturation (SpO2) values ​​and / or tissue oxygen saturation (StO2) values, which provide an alternative to cardiac output and / or peripheral perfusion, and which in turn can be associated with the patient's heart failure state and / or pulmonary state. For example, SpO2 can indicate arterial oxygenation, and therefore indicate pulmonary function, while StO2 can indicate venous and arterial oxygenation, and therefore indicate cardiac function and pulmonary function. When SpO2 is relatively normal or unchanged, StO2 can provide an alternative to cardiac output or otherwise indicate cardiac function. In some examples, these values ​​can be determined by one or more devices from a more central (e.g., subcutaneous and chest) location, rather than assessing arterial oxygen saturation via observation (e.g., visual observation) and / or pulse oxygen saturation (SpO2) at the periphery.

[0016] Instead of assessing a patient's anemic state by quantifying the patient's hemoglobin concentration via observation (e.g., visual observation) and / or via laboratory testing, some of the methods described herein include determining the patient's tissue hemoglobin index (THI) using a subcutaneously implanted device. In some examples, methods using the devices described herein may include monitoring one or more additional parameters associated with cardiac and / or pulmonary function, such as congestion (e.g., based on tissue impedance values ​​(Z)), heart rate, and / or heart rate variability, which may enable such methods to distinguish heart failure conditions from pulmonary diseases, and to distinguish different types of heart failure conditions.

[0017] One or more of the current values ​​of StO2, SpO2 and THI and the comparison of the corresponding baseline values ​​can be used to determine the corresponding one of the patient's heart failure state, lung state and anemia state. The combination of heart failure state, lung state and anemia state can be used to determine the health state, which can indicate whether one or more of the patient's medical conditions are stable or in progress. In some of the technologies described herein, a subcutaneous implantable device can determine the patient's health state and transmit the health state to a remote computer or other devices outside the patient's body. In some cases, the patient's health state can indicate whether any of the patient's tissue oxygen saturation, blood oxygen saturation, or hemoglobin concentration is insufficient, and can further indicate the possibility of acute decompensation or hospitalization of the patient based on one or more of these states, or can indicate that specific symptoms are caused by the patient's heart, lungs or blood specific potential conditions. The remote computer can then transmit instructions for medical intervention (e.g., instructions for changing a drug regimen) to a user device used by a patient or a caregiver. In this way, the diagnosis and / or treatment of a patient's condition, such as heart failure, lung disease, and / or anemia, can be modified as needed between clinical visits, which can help avoid adverse medical events, such as recurrence of symptoms or hospitalization.

[0018] In one example, a method for determining a patient's health state using an implantable medical device configured for subcutaneous implantation outside a chest cavity of the patient, the implantable medical device including at least one optical sensor, the method including performing the following by a processing circuit system of a medical device system including the implantable medical device: determining a current tissue oxygen saturation value of the patient based on a first signal received from the at least one optical sensor; determining a current pulse oxygen saturation value of the patient based on a second signal received from the at least one optical sensor; comparing the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​in a baseline tissue oxygen saturation value and a baseline pulse oxygen saturation value; determining a heart failure state of the patient based at least on a comparison of the current tissue oxygen saturation value with the baseline tissue oxygen saturation value; determining a pulmonary state of the patient based at least on a comparison of the current pulse oxygen saturation value of the patient with the baseline pulse oxygen saturation value; and determining a health state of the patient based on the heart failure state and the pulmonary state of the patient.

[0019] In another example, a system for determining a health status of a patient using an implantable medical device configured for subcutaneous implantation outside of a chest cavity of the patient includes: the implantable medical device, the implantable medical device including at least one optical sensor;

[0020] A processing circuit system configured to: determine a current tissue oxygen saturation value of a patient based on a first signal received from at least one optical sensor; determine a current pulse oxygen saturation value of the patient based on a second signal received from the at least one optical sensor; compare the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​in a baseline tissue oxygen saturation value and a baseline pulse oxygen saturation value; determine a heart failure state of the patient based at least on the comparison of the current tissue oxygen saturation value with the baseline tissue oxygen saturation value; determine a pulmonary state of the patient based at least on the comparison of the current pulse oxygen saturation value of the patient with the baseline pulse oxygen saturation value; and determine a health state of the patient based on the heart failure state and the pulmonary state of the patient.

[0021] In another example, a system for determining a health status of a patient using an implantable medical device configured for subcutaneous implantation outside a chest cavity of the patient, the system comprising: the implantable medical device comprising at least one optical sensor; and a processing circuit system configured to: determine a current tissue oxygen saturation value of the patient based on a first signal received from the at least one optical sensor; determine a current pulse oxygen saturation value of the patient based on a second signal received from the at least one optical sensor; determine a current tissue hemoglobin index value of the patient based on a third signal received from the at least one optical sensor; determine whether a difference between a current tissue oxygen saturation value and a baseline tissue oxygen saturation value satisfies a tissue oxygen saturation threshold associated with a change in cardiac function of the patient; determine whether a difference between a current pulse oxygen saturation value and a baseline pulse oxygen saturation value satisfies a pulse oxygen saturation threshold associated with a change in pulmonary function of the patient a pulse oxygen saturation value of the patient and a baseline pulse oxygen saturation value; and determining whether a difference between a current tissue hemoglobin index value and a baseline tissue hemoglobin index value satisfies a tissue hemoglobin index threshold associated with a change in the patient's red blood cell count; determining a heart failure state of the patient based at least on a comparison of the current tissue oxygen saturation value with the baseline tissue oxygen saturation value; determining a pulmonary state of the patient based at least on a comparison of the current pulse oxygen saturation value of the patient and a baseline pulse oxygen saturation value; determining an anemia state of the patient based at least on a comparison of the current tissue hemoglobin index value with the baseline tissue hemoglobin index value; determining a health state of the patient based on a combination of the heart failure state, the pulmonary state, and the anemia state; and transmitting the health state of the patient to a remote computer, wherein the remote computer includes a processing circuit system configured to perform the following: receiving the health state of the patient transmitted by the processing circuit system of the implantable medical device; and transmitting instructions for medical intervention to a user device.

[0022] In another example, a system for determining a health state of a patient includes: means for determining a current tissue oxygen saturation value of the patient based on a first signal received from at least one optical sensor; means for determining a current pulse oxygen saturation value of the patient based on a second signal received from the at least one optical sensor; means for comparing the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​of a baseline tissue oxygen saturation value and a baseline pulse oxygen saturation value; means for determining a heart failure state of the patient based at least on a comparison of the current tissue oxygen saturation value with the baseline tissue oxygen saturation value; means for determining a pulmonary state of the patient based at least on a comparison of the current pulse oxygen saturation value of the patient with the baseline pulse oxygen saturation value; and means for determining a health state of the patient based on a combination of the heart failure state and the pulmonary state of the patient.

[0023] In another example, a non-transitory computer-readable medium stores instructions for causing a processing circuit system to perform a method for determining a health state of a patient using an implantable medical device configured for subcutaneous implantation outside a chest cavity of the patient, the implantable medical device comprising at least one optical sensor, the method comprising: determining a current tissue oxygen saturation value of the patient based on a first signal received from the at least one optical sensor; determining a current pulse oxygen saturation value of the patient based on a second signal received from the at least one optical sensor; comparing the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​in a baseline tissue oxygen saturation value and a baseline pulse oxygen saturation value; determining a heart failure state of the patient based at least on a comparison of the current tissue oxygen saturation value with the baseline tissue oxygen saturation value; determining a pulmonary state of the patient based at least on a comparison of the current pulse oxygen saturation value of the patient with the baseline pulse oxygen saturation value; and determining a health state of the patient based on a combination of the heart failure state of the patient and the pulmonary state.

[0024] The present disclosure is intended to provide an overview of the subject matter described in the present disclosure. It is not intended to provide an exclusive or exhaustive explanation of the devices and methods described in detail in the following drawings and descriptions. The details of one or more aspects of the present disclosure are set forth in the following attached drawings and descriptions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will become apparent from the description and drawings, and from the claims.

[0026] Figure 1 A conceptual diagram illustrating an example of a medical device system including a leadless implantable medical device and an external device in conjunction with a patient;

[0027] Figure 2 It is shown Figure 1 A conceptual diagram of an example configuration of a leadless implantable medical device of a medical device system;

[0028] Figure 3 It is shown Figure 1 A functional block diagram of another perspective of an example configuration of a leadless implantable medical device;

[0029] Figure 4A and Figure 4B is shown to be basically similar to Figure 1 Block diagram of other exemplary leadless implantable medical devices of the implantable medical device;

[0030] Figure 5 is shown including an external device (such as a server), and coupled to Figure 1 Leadless implantable medical devices and Figure 1 A block diagram of an example system of one or more computing devices of an external device;

[0031] Figure 6 is a flow chart illustrating an example technique for determining a patient's health status and transmitting the health status to a remote computer, wherein determining the patient's health status is performed by determining the patient's heart failure status, pulmonary status, and anemia status based on comparisons of current tissue oxygen saturation values, pulse oxygen saturation values, and tissue hemoglobin index values ​​with corresponding baseline values;

[0032] Figure 7 is shown for determining Figure 6 A flowchart of an example technique for determining a baseline value or current value of tissue oxygen saturation, pulse oxygen saturation, and tissue hemoglobin index;

[0033] Figure 8 is a flow chart illustrating an example technique for determining a current diagnostic score and determining an updated health status of a patient based on a comparison of the current diagnostic score to a baseline diagnostic score.

[0034] Fig. 9 is shown for remote computers based on Figure 1 A flowchart of an example technique for determining instructions for medical intervention based on a patient's health status received by a leadless implantable medical device and transmitting the instructions to a user interface;

[0035] Fig.10 is a flow chart illustrating an example technique for determining changes in a patient's lung function and / or heart function based on trends in the patient's pulse oxygen saturation values, heart rate values, and heart rate variability values;

[0036] Fig.11 is a flow chart illustrating an example technique for determining changes in a patient's lung function and / or heart function based on trends in the patient's tissue oxygen saturation values ​​and tissue impedance values; and

[0037] Fig.12 is a flow chart illustrating an example technique for determining a type of heart failure condition in a patient based on current values ​​of the patient's tissue oxygen saturation and tissue impedance. DETAILED DESCRIPTION

[0038] In general, the present disclosure describes example techniques related to determining a patient's health status based on physiological parameters associated with cardiac function, pulmonary function, and blood function, and in some cases determining a differential diagnosis between the heart, lungs, and anemia based on the parameters, as, for example, the cause of one or more symptoms. The subcutaneous IMD used in some of the example techniques can be configured for placement beneath the skin of the patient's torso, such as between the skin and the pectoral muscles. The processing circuitry of the subcutaneous IMD can determine the patient's current StO2 value, SpO2 value, and THI value based on signals detected by one or more optical sensors of the subcutaneous IMD. In some examples, the IMD can be leadless, and the optical sensors can be integrated with and / or connected to the housing of the IMD.

[0039] The processing circuit system can then compare the current StO2 value, SpO2 value and THI value with the corresponding baseline values, which can be stored in the memory of the IMD. Based on the difference between the current value and the baseline value, the processing circuit system can determine the patient's heart failure state, lung state and anemia state, and determine the patient's current health state based on one or more of the patient's heart failure state, lung state and anemia state. For example, the processing circuit system can determine that one or more of the patient's heart function, lung function and blood function has changed, and transmit this determination to the remote computer as part of the patient's health state. In some examples, the difference between the current value and the baseline value can be given different weights, such as, depending on the result of the state determination. It is further conceivable that in some examples, the remote computer can transmit instructions for medical intervention to the user device based on the health state. Although the technology for determining the patient's health state is described herein as being based on heart failure state, lung state and anemia state, such technology can be used to determine the patient's health state based on other states related to other physiological functions of the patient. Additionally, although this document is primarily described in the context of considering each of cardiac function, pulmonary function, and blood function, some examples may include considering any one or more functions, for example, cardiac function and pulmonary function without considering blood function.

[0040] Some other techniques can be used to monitor one or more aspects of the cardiac function of a patient (such as a patient with a heart failure condition). Such other techniques may include measuring transthoracic impedance to assess congestion, or measuring pulse transit time (PTT) to assess vasoconstriction. However, such other techniques may not be able to provide a reliable assessment of the patient's health status based on the monitoring of multiple physiological functions, and a reliable assessment of the patient's health status can be obtained by a combined assessment of the patient's heart function, lung function and blood function by monitoring StO2, SpO2, and THI according to the technology described herein. Therefore, such other techniques may not be very useful for patients with one or more interrelated medical conditions, and the progress of these interrelated medical conditions may lead to changes in additional physiological functions and / or lead to the development of additional medical conditions. In addition, such other techniques may be limited in distinguishing between different types of heart failure conditions characterized by different hemodynamic profiles and having different treatment requirements. Because the hemodynamic profile of a heart failure patient may change with the progress of the patient's heart failure condition, such other techniques may not be able to identify the progress of the patient's heart failure condition. Therefore, monitoring tissue impedance and / or PTT alone may not be sufficient to assess a patient's health status, to differentiate between possible causes of specific symptoms that may be due to changes in one or more of the patient's cardiac, pulmonary, and hematological functions, and likewise may not be sufficient for identifying appropriate treatment options.

[0041] Other techniques for monitoring one or more of cardiac function, pulmonary function, and blood function may be invasive, prone to lack of accuracy, and / or cumbersome for long-term monitoring. For example, some methods for monitoring cardiac function may include sensing transthoracic impedance values ​​or generating an electrogram (ECG) using signals obtained from electrodes on leads placed in the chest cavity (such as, in the heart). Such electrode placement is significantly more invasive than subcutaneous placement and may be associated with a greater risk of complications during or after implantation. Some methods for monitoring pulmonary function may include: measuring arterial blood oxygenation via arterial blood-gas sampling or SpO2 measurement using an in vitro sensor located on the periphery of the patient. However, arterial blood-gas sampling is invasive and painful for the patient, and in vitro SpO2 sensors may be affected by motion artifacts and are too cumbersome to monitor for a long time. Similarly, methods for measuring blood hemoglobin concentration are invasive and rely on laboratory analysis of blood samples. Furthermore, while some other methods for monitoring physiological function (eg, cardiac function) may include generating an alert if a measurement meets a threshold, such methods are limited in that they do not include providing instructions to the patient for medical intervention based on these alerts.

[0042] In certain example techniques described herein, a patient's heart failure state, lung state, and anemia state can be determined using a subcutaneous implantable device configured to measure all three of StO2, SpO2, and THI from a single location near the patient's pectoral muscles. Such measurements can be repeated at predetermined intervals (such as every hour or every day). The device can then: determine the patient's heart failure state, lung state, and anemia state based on the current and baseline values ​​of StO2, SpO2, and THI, determine the corresponding health state, and transmit the health state to a remote computer via wireless communication, which can then transmit instructions for medical intervention to a user device (e.g., a smartphone or tablet computer located with the patient or caregiver). In some cases, the health state can include a differential diagnosis between the heart, lungs, and anemia, for example, as the cause of one or more symptoms experienced by the patient. Therefore, in some cases, the technology described herein can advantageously provide a reliable and accurate assessment of the patient's health state on a regular basis, and can enable modifications to the patient's treatment between clinician visits, which in turn can provide improved clinical results.

[0043] Figure 1 An example medical device system 2 environment according to certain example apparatus and methods described herein is shown in conjunction with a patient 4 and a heart 6. The example techniques may be used with an implantable medical device (IMD) 10, which may be leadless and communicate wirelessly with an external device 12, such as a Figure 1 In some examples, IMD 10 can be coupled to one or more leads. In some examples, IMD 10 can be implanted outside the chest of patient 4 (e.g., in Figure 1 The IMD 10 may be located near the sternum, near or just below the level of the heart 6. In some examples, the IMD 10 may be in the form of a Reveal LINQ TM External device 12 may be a computing device configured for use in an environment such as a home, clinic, or hospital, and may be further configured to communicate with IMD 10 via wireless telemetry. For example, external device 12 may be coupled to a remote patient monitoring system, such as the EM-1000, available from Medtronic plc of Dublin, Ireland. In some examples, external device 12 may include a programmer, an external monitor, or a consumer device such as a smart phone or tablet.

[0044] IMD 10 may include one or more optical sensors that collectively detect signals that enable the processing circuitry of IMD 10 to determine current values ​​of subcutaneous StO2, SpO2, and THI of patient 4, and based on these values, determine the heart failure state, lung state, and anemia state of patient 4. For example, the one or more optical sensors may be configured to detect signals indicative of StO2 values, SpO2 values, and THI values ​​of tissue surrounding IMD 10. The processing circuitry of IMD 10 may use the current StO2 values, SpO2 values, and THI values ​​of tissue surrounding the IMD to determine a corresponding state among the heart failure state, lung state, and anemia state of patient 4.

[0045] For example, the processing circuit system of IMD 10 can compare the current StO2 value, SpO2 value and THI value with the corresponding baseline value stored in the memory of IMD10 to determine the difference between the current StO2 value, SpO2 value and THI value and the corresponding baseline value. If the difference between the current value and one or more of the corresponding baseline values ​​meets the threshold, the processing circuit system of IMD 10 can determine that one or more of the heart failure state, lung state or anemia state of the patient 4 has changed relative to the time when the baseline value is established. In some instances, the difference between the current value and the corresponding baseline value of StO2, SpO2 and THI corresponds to the change of the heart failure state, lung state and anemia state in a 1:1 relationship, respectively. In other examples, one or more of the differences between the current value and the corresponding baseline value of StO2, SpO2 and THI can correspond to multiple changes in the changes of the heart failure state, lung state and anemia state. For example, the difference between the current value and the corresponding baseline value of StO2 can correspond to changes in both the heart failure state and the lung state.

[0046] In some examples, the IMD 10 may further include a plurality of electrodes. The plurality of electrodes may be configured to detect signals that enable the processing circuit system of the IMD 10 to determine the current values ​​of additional parameters associated with the cardiac function and / or pulmonary function of the patient 4. As described above, the parameter StO2 may be associated with cardiac function and pulmonary function because the StO2 value is based on both venous oxygen saturation (SvO2), which is a measure of cardiac function, and arterial oxygen saturation (SaO2), which is a measure of pulmonary function. Therefore, a method including identifying changes in the cardiac function and pulmonary function of the patient 4 to determine the effects of both the cardiac function and pulmonary function of the patient 4 on the current StO2 value may be advantageous. In some examples, SaO2 or SpO2 may indicate whether a change in the StO2 value is associated with a change in cardiac function or a change in pulmonary function. Since SpO2 can be used as an approximation of SaO2, measurements of SaO2 or SpO2 may be used in such examples.

[0047] In some examples, the plurality of electrodes of the IMD 10 may be configured to detect a signal indicating a current Z value of tissue surrounding the IMD 10. For example, the processing circuit system of the IMD 10 may cause one or more of the plurality of electrodes to generate a current that flows through the tissue of the patient 4 to reach another one or more of the plurality of electrodes. The processing circuit system of the IMD 10 may then measure a voltage drop across such electrodes and determine the current Z value based on the current value and the voltage drop value. In such examples, it may not be necessary to determine a current SaO2 value or SpO2 value or a current SvO2 value in order to distinguish changes in the cardiac function of the patient 4 from changes in the pulmonary function of the patient 4. In other examples, the processing circuit system of the IMD 10 may be configured to identify changes in the pulmonary function of the patient 4 by determining whether the difference between the current SaO2 value or SpO2 value and the corresponding baseline SaO2 value or SpO2 value meets a threshold, rather than by cross-referencing the parameter StO2 with the parameter Z.

[0048] As follows about Fig.11 As discussed, the processing circuitry of IMD 10 may use the current Z value to determine the congestion state of patient 4, which may be considered an aspect of the heart failure state of patient 4, by determining whether the difference between the current Z value and the baseline Z value satisfies a threshold. The processing circuitry of IMD 10 may then cross-reference the congestion state of patient 4 (i.e., congested or not congested) and the result of the determination of whether the difference between the current StO2 value and the baseline StO2 value of patient 4 satisfies the StO2 threshold. Depending on the result of the cross-reference, the processing circuitry of IMD 10 may determine the effect of the congestion state and the pulmonary state of patient 4 on the current StO2 value, thereby distinguishing between the cardiac function and the pulmonary function of patient 4.

[0049] In some examples, a method including identifying a change in cardiac function of patient 4 may include using a Z value and a StO2 value to determine a type of heart failure condition of patient 4. In such an example, processing circuitry of IMD 10 may cross-reference a determination of whether a difference between a current Z value and a baseline Z value satisfies a threshold and a determination of whether a difference between a current StO2 value and a baseline StO2 value of patient 4 satisfies a StO2 threshold. Fig.12 As discussed, the processing circuitry of IMD 10 may characterize the hyperemia state and the perfusion state of the heart failure condition of patient 4 based on a cross-reference. That is, the processing circuitry of IMD 10 may determine that the hyperemia state of the heart failure condition of patient 4 is "wet" or "dry" (i.e., hyperemia or non-hyperemia), or "warm" or "cold" (well perfused or inadequately perfused).

[0050] In some examples, the processing circuit system of IMD 10 can be configured to distinguish whether the change in the blood function of patient 4 is accompanied by a change in the cardiac function and / or pulmonary function of patient 4. For example, the processing circuit system of IMD 10 can cross-reference the following items: whether the difference between the current value of THI and StO2 and the corresponding baseline value of THI and StO2 meets the determination result of THI and / or StO2 threshold, and whether the difference between one or more of the current values ​​of Z and SpO2 / SaO2 and the corresponding baseline value of Z and SpO2 / SaO2 meets the determination of Z and / or SpO2 / SaO2 threshold. The processing circuit system of IMD 10 can determine one or both of the congestion state or the pulmonary state of patient 4, and the anemia state based on the cross-reference. For example, the processing circuit system of IMD 10 can determine whether the anemia condition of patient 4 is accompanied by a heart failure condition (e.g., a congestive heart failure condition) and / or a lung disease. In some such examples, determining that patient 4's anemia condition is accompanied by a heart failure condition and / or a pulmonary condition may indicate a higher likelihood of acute decompensation or hospitalization compared to examples in which processing circuitry of IMD 10 determines that patient 4's anemia condition is not accompanied by a heart failure condition and / or a pulmonary condition.

[0051] In yet other examples, the processing circuitry of IMD 10 may be configured to distinguish changes in the cardiac function of patient 4 from changes in the pulmonary function of patient 4 by monitoring one or more other parameters associated with the pulmonary function of patient 4. For example, IMD 10 may include one or more accelerometers configured to generate signals that may be associated with one or more aspects of the respiratory cycle of patient 4, such as the frequency and / or amplitude of the respiratory cycle, and / or associated with one or more respiratory abnormalities (e.g., coughs or rales) of the pulmonary function of patient 4. Additionally or alternatively, IMD 10 may include one or more acoustic sensors configured to generate signals that may be associated with one or more aspects of the respiratory cycle of patient 4, such as sounds or vibrations associated with the respiratory cycle and / or respiratory abnormalities of patient 4, and / or IMD 10 may identify one or more aspects of the respiratory cycle in the Z (impedance) signal.

[0052] In any such other examples, the processing circuit system of IMD 10 may receive one or more signals related to the lung function of patient 4 from one or more accelerometers or acoustic sensors, and determine a current value of one or more aspects of the lung function of patient 4. The processing circuit system of IMD 10 may then determine the respiratory state of patient 4 based on the difference between the current value of the one or more aspects of the lung function of patient 4 and the corresponding baseline value of the one or more aspects of the lung function of patient 4. The processing circuit system of IMD 10 may then cross-reference the following items: the respiratory state of patient 4 (i.e., normal or abnormal), and the determination result of whether the difference between the current StO2 value and the baseline StO2 value of patient 4 meets the StO2 threshold. Depending on the result of the cross-reference, the processing circuit system of IMD 10 can determine the impact of the respiratory state of patient 4 on the current StO2 value, thereby distinguishing between the cardiac function and the pulmonary function of patient 4.

[0053] Additionally or alternatively, the plurality of electrodes may be configured to detect an ECG signal that may be indicative of a heart rate and / or heart rate variability value of the patient 4. As described above, the parameter StO2 may be associated with both cardiac function and pulmonary function. Furthermore, since the parameter SpO2 may be used as an approximation of SaO2, the parameter SpO2 may also be associated with both cardiac function and pulmonary function, although primarily with pulmonary function. Therefore, while monitoring both StO2 and SpO2 may be used to differentiate between problems with cardiac function or problems with pulmonary function, it may be advantageous for the methods described herein to include monitoring one or more additional parameters of cardiac function and / or pulmonary function in order to differentiate the effects of each of the cardiac function and pulmonary function of the patient 4 on the current SpO2 value. Such additional parameters may include HR and HRV, each of which may be associated with cardiac function. For example, as described below with respect to Fig.10 As further discussed, an increase in HR and / or a decrease in HRV may indicate worsening cardiac function. In such examples, it may not be necessary to determine a current StO2 value or a current SvO2 value in order to distinguish changes in cardiac function of patient 4 from changes in pulmonary function of patient 4. In other examples, the processing circuitry of IMD 10 may be configured to distinguish changes in cardiac function of patient 4 from changes in pulmonary function of patient 4 by cross-referencing parameters SpO2 and StO2, rather than by cross-referencing one or both of parameters HR and HRV with parameter SpO2.

[0054] In some examples, the plurality of electrodes of IMD 10 may be configured to detect ECG signals that may indicate a current heart rate (HR) value and / or a current heart rate variability (HRV) value of patient 4. Fig.10As discussed, the processing circuit system of IMD 10 may then compare one or both of the current HR value and HRV value with the corresponding baseline value to determine whether the difference between the current HR value and / or HRV value satisfies the corresponding threshold value. The processing circuit system of IMD 10 may then cross-reference the following items: the result of this determination, and the result of the determination of whether the difference between the current SpO2 value and the baseline SpO2 value of patient 4 satisfies the SpO2 threshold value. Depending on the result of the cross-reference, the processing circuit system of IMD 10 may determine the relative impact of the heart failure state and the lung state of patient 4 on the current SpO2 value, thereby further distinguishing the heart function and lung function of patient 4. In some examples, in the case where patient 4 may suffer from non-congestive heart failure, it may be particularly useful to use HR values ​​and HRV values ​​to distinguish the heart function and lung function of patient 4 by considering the impact of SvO2 on StO2 (and in some cases, the impact on SpO2) regardless of the congestive state of patient 4. In any such examples, the processing circuitry of IMD 10 can determine the current arrhythmia state of patient 4 based on the ECG signals (e.g., the presence or absence of atrial fibrillation and the ventricular rate during atrial fibrillation), which is indicative of cardiac function and may also help enable the processing circuitry of IMD 10 to distinguish whether changes in monitored parameters are attributable to cardiac function and pulmonary function of patient 4.

[0055] Whether any difference between the current values ​​of StO2, SpO2, THI, Z, HR and HRV and the corresponding reference values ​​exceeds a threshold, IMD 10 can determine the patient's health state according to a combination of heart failure state, lung state and anemia state, and wirelessly transmit the heart failure state of patient 4 to the external device 12. The health state may include a diagnostic score of patient 4, which may be associated with the possibility that patient 4 will decompensate and require hospitalization within a certain period of time. In some examples, the health state may include a differential diagnosis between heart failure conditions, lung diseases and anemia that patient 4 may suffer from (e.g., as one or more causes of one or more symptoms experienced by the patient). IMD 10 can transmit the health state of patient 4 to the external device 12 at a predetermined interval (such as, daily, weekly, or at any other desired time period). Additionally or alternatively, IMD 10 can determine the health state of patient 4 as needed when receiving input from patient 4 or a caregiver (such as, indicating that patient 4 is experiencing one or more specific symptoms).

[0056] Although in some examples, the health status of patient 4 can be based on the difference between the current value and the corresponding baseline value of each of StO2, SpO2, THI, Z, HR, HRV, or other parameters, for clarity, the examples herein may be described with respect to StO2, SpO2, and THI. However, in any such examples, the method of determining the health status of patient 4 can include the values ​​of Z, HR, HRV, or other parameters in any combination suitable for patient 4.

[0057] In some examples, the intervals at which the IMD 10 determines the health state of the patient 4 are the same as the intervals at which the IMD 10 transmits the health state to the external device 12. In other examples, the IMD 10 may determine the health state of the patient 4 more frequently than the IMD 10 transmits the health state to the external device 12. By determining the health state more frequently than transmitting the health state, the accuracy of the technique for determining the health state may be improved by eliminating outlier measurements of StO2, SpO2, and THI. For example, the IMD 10 may determine that the difference between the current StO2, SpO2, and THI of the patient 4 and the corresponding baseline meets the threshold only when a certain number or proportion of previous results meet or exceed the threshold. In other examples, a single event in which the current value meets or exceeds the threshold may be sufficient for the IMD 10 to determine that one or more of the corresponding heart failure state, lung state, or anemia state has changed, and therefore determine that the health state of the patient 4 has changed. In some examples, the clinician may configure the sensitivity of IMD 10 to certain types of values ​​that exceed thresholds upon or after implantation of IMD 10, based on factors such as the individual condition of Patient 4. As discussed below, the clinician may configure several aspects of the operation of IMD 10 to help achieve improved monitoring and clinical outcomes for individual patients, such as Patient 4.

[0058] Implantation of IMD 10 Figure 1At or after the subcutaneous position shown, the clinician can configure one or more aspects of the IMD 10. In some examples, the clinician can use routine assessments to establish baseline values ​​for StO2, SpO2, and THI. For example, the clinician can use a co-oximeter measurement to draw arterial and venous blood to assess tissue perfusion, apply a pulse oximeter to the patient's periphery to estimate arterial blood oxygenation, and view laboratory results of blood analysis to estimate tissue hemoglobin index. In addition, the clinician can complete a standard examination and assessment of the patient 4 to assess one or more other aspects of cardiac function, pulmonary function, and / or blood function. For example, the clinician can identify whether there is congestion by observing the patient's edema, and to what extent. The clinician can then use an application on a tablet or other smart device to enter the baseline values ​​of StO2, SpO2, and THI of the patient 4 determined empirically and the corresponding baseline heart failure state, pulmonary state, and anemia state into the memory of the IMD 10.

[0059] In other examples, instead of using the above-mentioned conventional assessment to determine the baseline values ​​of StO2, SpO2, and THI, the clinician can perform a standard examination and assessment on patient 4 to determine the heart failure state, lung state, and anemia state of patient 4. Based on the results of this assessment, and optionally based on other data corresponding to patient 4, the clinician can select baseline values ​​of StO2, SpO2, and THI for patient 4. A list or table of such values ​​can be presented by an application on a clinician tablet or other smart device, or can be accessible from a centralized database. Once the clinician selects appropriate baseline values ​​for patient 4, he or she can use the application to store these values ​​in IMD 10.

[0060] In yet other examples, IMD 10 may be configured to perform a learning phase after implantation in patient 4, in which IMD 10 determines baseline values ​​of StO2, SpO2, and THI for patient 4 based on values ​​collected by IMD 10 over a period of time and stores these values ​​in a memory of IMD 10. For example, IMD 10 may measure StO2, SpO2, and THI relatively frequently (e.g., several times per hour or per day) for a period of time (e.g., a week or more) to determine baseline values ​​during a period when patient 4's condition is stable and not decompensating.

[0061] Because heart failure illness, lung disease and anemia are progressive diseases, their progress may be interrelated, so the values ​​of the baseline, threshold and event identifier associated with patient 4 can also be regularly updated. For example, IMD 10 can be performed monthly, quarterly, annually, or when any other appropriate period expires, a new learning phase is performed. The new learning phase can generate new values ​​associated with one or more of the baseline, threshold and evidence level based on the heart failure state of the update of patient 4. In other examples, the clinician can program IMD 10 to update such values ​​as needed, such as after the health event experienced by patient 4, which may affect the applicability of these values ​​to one or more aspects of the health state of patient 4.

[0062] In some examples, the IMD 10 may determine a baseline value based on an average of StO2 values, SpO2 values, and THI values ​​collected during a training period. In other examples, the IMD 10 may reject outliers collected during training before determining a baseline value, although the IMD may use other methods of determining a baseline value based on the collected values. In some examples where the IMD 10 uses a training period to determine a baseline value, the clinician may also perform standard examinations and assessments of the patient's 4 heart failure status, lung status, and anemia status, and store these values ​​in the IMD 10.

[0063] In addition to determining baseline values ​​of StO2, SpO2, and THI for patient 4, IMD 10 or a clinician may also determine thresholds for StO2, SpO2, and THI for patient 4 and store the thresholds in a memory of IMD 10. In some examples, the threshold may indicate a value of a difference between a current value of one of StO2, SpO2, and THI and a corresponding baseline value, indicating that one or more of the heart failure state, lung state, or anemia state of patient 4 may have changed. For example, IMD 10's determination of the heart failure state of patient 4 may be based at least in part on whether the difference between the current StO2 value and the corresponding baseline value satisfies the threshold.

[0064] The IMD 10 may determine a threshold for each of many different baseline values ​​for each of StO2, SpO2, and THI, such as during a training period of the IMD 10. In some examples, the IMD 10 may automatically associate a specific threshold with a specific baseline value of one of StO2, SpO2, and THI of the patient 4. In other examples, the IMD 10 may determine a threshold for one of StO2, SpO2, and THI based in part on the values ​​of other baselines determined for the patient 4. For example, if the baseline StO2 value of the patient 4 indicates that the patient 4 has insufficient tissue perfusion, the IMD 10 may select a lower threshold for SpO2 than if the baseline StO2 value does not indicate that the patient 4 has insufficient tissue perfusion. In this way, such a threshold determination may take into account a physiological parameter (e.g., StO2) that may be associated with more than one physiological function (e.g., cardiac function and pulmonary function). In this way, the health status determination of the IMD 10 may be more sensitive to patients at high overall risk of acute decompensation, such as patients with multiple medical conditions or patients for whom acute decompensation may have greater health consequences. In other examples, the clinician may choose to program IMD 10 to apply a relatively higher or lower threshold than the threshold selected by processing circuitry of IMD 10 based on other considerations known to the clinician.

[0065] Regardless of whether the thresholds of StO2, SpO2, and THI are determined by the processing circuit system of IMD 10 or by a clinician during the training period, such thresholds can be updated one or more times after the implantation of IMD 10. For example, the thresholds can be updated after the patient 4 experiences an acute decompensation or hospitalization event, which can indicate that one or more parameters of the patient's 4 heart failure condition, lung disease, or anemia have developed or otherwise changed. Alternatively, the thresholds can be updated when a time period expires (e.g., weekly, monthly, or annually after the implantation of IMD 10). This updating of the thresholds can be automatically performed by the processing circuit system of IMD 10, or manually performed by a clinician. In any such example, the updated thresholds can be determined based on the trend of one or more of the current values ​​of StO2, SpO2, and THI during the previous time period. In this way, the thresholds used in the technology described herein can be modified as needed to take into account changes in the health status of the patient 4.

[0066] In addition to determining whether the difference between any current value of StO2, SpO2, and THI and the corresponding baseline value exceeds one or more threshold values, IMD 10 can also determine the diagnostic score of patient 4 based on the current values ​​of StO2, SpO2, and THI. The diagnostic score can be a value (e.g., a numerical value) associated with the probability that patient 4 will decompensate and / or require hospitalization within a certain period of time, regardless of whether the difference between any current value of StO2, SpO2, and THI and the corresponding baseline value exceeds one or more threshold values. In some examples, if one or more such differences exceed the threshold value, the diagnostic score of patient 4 can be further increased.

[0067] IMD 10 can determine the diagnostic score of patient 4 at least in part based on the value of the level of evidence, and the value of the level of evidence can be associated with the values ​​of various parameters of one or more medical conditions (such as, heart failure conditions, lung diseases and anemia). In some examples, the level of evidence can be determined based on the assessment of one or more patient populations suffering from one or more such conditions. The diagnostic score can include one or more values ​​associated with one or more levels of evidence, wherein each level of evidence is associated with the value of the parameter of a specific medical condition. For example, the assessment of the patient population can classify the parameters of heart failure (e.g., congestion and hypoperfusion) as occurring at different severity levels. Each severity level of each parameter can be characterized as a "level of evidence" associated with a numerical value, and the patient results (e.g., previous patient population data) of each level of evidence can be recorded. According to the patient's results, the numerical values ​​associated with the level of evidence can be weighted to reflect its predictive value to the patient's results.

[0068] IMD 10 may determine a diagnostic score associated with one or more of the heart failure state, lung state, or anemia state of patient 4 based on a combination of evidence levels associated with the current values ​​of StO2, SpO2, and THI of patient 4. For example, the diagnostic score may be based on an integration of previous population data (e.g., data associated with the level of evidence) with patient 4-specific measurements (e.g., the current values ​​of StO2, SpO2, or THI of patient 4), such as by using other methods of Bayesian statistics or machine learning. In some examples, the diagnostic score based on the combination of the level of evidence may indicate the likelihood of a change in each of the corresponding parameters of the medical condition associated with the level of evidence experienced by patient 4. For example, the level of evidence associated with the current value of StO2 may indicate that the likelihood of a change in the heart failure state (which may be associated with a change in cardiac function) experienced by patient 4 during the previous time period on which the diagnostic score is based is X%. Similarly, the level of evidence associated with the current value of SpO2 or THI may indicate that the patient 4 has experienced a change in the corresponding state of the pulmonary state or anemia state during the previous time period (which may be associated with a change in pulmonary function or blood function, respectively) with a probability of Y% or Z%. In some examples, the diagnostic score can be adjusted upward or downward based on how much the difference between the current value of the patient 4 and the corresponding baseline value exceeds the associated threshold. In addition, the clinician can manually modify the weights assigned by the IMD 10 to the level of evidence for different measured parameters based on the individual condition or medical history of the patient 4. For example, the clinician can manually modify one or more of the weights assigned by the IMD 10 based on events in the medical history of the patient 4, such as, hospitalization due to heart failure, medication changes, history of systolic or diastolic heart failure, hypertension, respiratory disease (e.g., COPD), diabetes, atrial fibrillation, renal failure, one or more blood diseases (e.g., anemia), one or more sleep disorders (e.g., sleep apnea), etc. In any such examples, the levels of evidence associated with the parameters StO2, SpO2, and THI may be stored in the memory of IMD 10.

[0069] In some examples, as described above, the diagnostic score can be a baseline diagnostic score associated with one or more of the heart failure state, lung state, or anemia state of patient 4. Since heart failure conditions, lung disease, and anemia can be progressive diseases, IMD 10 can periodically determine the health state of patient 4 at regular intervals. In some examples, IMD 10 can determine an updated health state of patient 4 by iteratively performing the above method. In other examples, the updated health state of patient 4 determined by IMD 10 can be based at least in part on the determination of the current diagnostic score of patient 4 and the comparison of the current diagnostic score with a previously determined diagnostic score of patient 4 (e.g., a baseline diagnostic score). In some examples, the updated health state can include an updated diagnosis of one or more of heart failure conditions, lung disease, and anemia, such as diagnosing that the heart failure condition of patient 4 has progressed from a first type of heart failure condition to a second type of heart failure condition.

[0070] In such an example, IMD 10 can determine the current diagnostic score of patient 4 by combining weighted values ​​associated with the current values ​​of StO2, SpO2, and THI of patient 4. For example, IMD 10 can determine the difference between the current value of each of StO2, SpO2, and THI and the corresponding baseline value of patient 4. IMD 10 can then determine a weighted value for each of the differences between the current value and the corresponding baseline value. In some examples, IMD 10 can assign weights to the difference based on factors such as the medical history of patient 4, which can include one or more of the medical history events described in the example of one or more examples of manual modification of weights by clinicians above. For example, patient 4 may have a history of anemia, which may indicate that patient 4 is prone to anemia in the future. Alternatively, population-based data may indicate that patients with the same or similar baseline values ​​as patient 4 may be particularly likely to become anemic. In some examples, the weight assigned to the difference by IMD 10 may have a negative value, such as if the medical history of patient 4 or population-based data indicates that patient 4 is unlikely to become anemic. IMD 10 may then combine weighted values ​​of the differences between the current values ​​and the baseline values ​​to arrive at a current diagnostic score for patient 4 .

[0071] In some examples, IMD 10 may compare the current diagnostic score to a baseline diagnostic score for patient 4, where the baseline diagnostic score may be determined during a previous iteration of the method by which IMD 10 determines the health state of patient 4. IMD 10 may then determine an updated health state for patient 4 based on the comparison of the baseline diagnostic score to the current diagnostic score, and transmit the updated health state parameters to a remote computer (e.g., external device 12). External device 12 or another remote computer may then transmit instructions for medical intervention (e.g., a change in a medication regimen, or instructions to schedule a clinician visit or seek medical assistance) to an interface of a user device located with the patient.

[0072] In some examples, the baseline diagnostic score of patient 4 may be updated in a manner substantially similar to that described above with respect to thresholds. For example, the baseline diagnostic score of patient 4 may be updated after patient 4 experiences an acute decompensation or hospitalization event, which may indicate that one or more parameters of the medical condition of patient 4 have progressed or otherwise changed. Alternatively, the baseline diagnostic score of patient 4 may be updated upon expiration of a time period (e.g., weekly, monthly, or annually after implantation of IMD 10). Such updates to the baseline diagnostic score of patient 4 may be performed automatically by the processing circuitry of IMD 10 or manually by a clinician.

[0073] In some examples, the medical device system 2 may further include an implantable pressure sensing device, which includes one or more pressure sensors and can be used to monitor cardiovascular pressure of the patient 4, such as pulmonary artery (PA) pressure. Increased tissue fluid volume can be subsequently associated with increased PA or other increased blood pressure and pulmonary congestion. During the progression of acute heart failure decompensation, pulmonary congestion may interfere with oxygen exchange and cause arterial oxygen saturation to decrease. Therefore, the technology for determining the health state of the patient 4 may include monitoring PA pressure or another blood pressure to provide additional parameters, and the medical device system 2 can monitor the cardiac function and pulmonary function of the patient 4 through this additional parameter. In such an example, the implantable pressure sensing device can be implanted in the pulmonary artery or other parts of the vascular system of the patient 4. The pressure sensing device may include: a processing circuit system, which is configured to receive signals from one or more pressure sensors and determine the current PA pressure value or other current blood pressure value of the patient 4; and a communication circuit system, which is configured to transmit the current PA pressure value or other current blood pressure value of the patient 4 to the IMD 10 and / or the external device 12. As with other parameters of the physiological function of patient 4, the processing circuitry of IMD 10 may compare the current blood pressure value to a baseline blood pressure value, for example by comparing the current PA pressure value to a baseline PA pressure value. The processing circuitry of IMD 10 may then determine whether the difference between the current PA pressure value or other pressure value and the corresponding baseline value exceeds a threshold value and include such determination in determining whether the cardiac function and / or pulmonary function of patient 4 has changed and / or in determining a diagnostic score for patient 4.

[0074] As described above, the operating parameters of IMD 10 can be easily customized to meet the needs of patient 4, such as by setting the values ​​of baseline, threshold and evidence level based on the individual attributes of patient 4. The degree and ease of the customizability of IMD 10 can provide many benefits. For example, IMD 10 reflects the customizability of the heart failure symptoms of patient 4. This helps to ensure that appropriate drug therapy is prescribed for patient 4, thereby reducing the possibility of human error when prescribing treatment. In addition, in the example that IMD10 selects one or more of the baseline value, threshold or evidence level value for patient 4, the burden of clinician time can be reduced, which can reduce the time required for outpatient visits and promote effective treatment. In addition, as described above, IMD 10 realizes that the heart failure treatment, lung treatment and / or anemia treatment of patient 4 are modified between clinician visits, which can help avoid acute decompensation, and thus lead to better clinical results, such as improving the quality of life of patient 4 or reducing medical expenses.

[0075] The external device 12 can be used to program commands or operating parameters into the IMD 10 for controlling the functions of the IMD 10 (e.g., when configured as a programmer for the IMD 10). In some examples, the external device 12 can be used to query the IMD 10 to retrieve data, including device operating data and physiological data accumulated in the IMD memory. Such inquiries can occur automatically according to a schedule, or can occur in response to a remote or local user command. Programmers, external monitors, and consumer devices are examples of external devices 12 that can be used to query the IMD 10. Examples of communication technologies used by the IMD 10 and the external device 12 include radio frequency (RF) telemetry, which can be an RF link established via Bluetooth, WiFi, or a medical implant communication service (MISC). In some examples, the external device 12 may include a user interface configured to allow a clinician to interact remotely with the IMD 10.

[0076] Medical device system 2 is an example of a medical device system configured to monitor the health status of patient 4, diagnose the cause of the symptoms experienced by patient 4 by distinguishing heart failure conditions, lung diseases, and anemia from each other, and facilitate updates to patient 4, such as for heart failure conditions, lung diseases, and / or anemia, as needed between clinician visits. The techniques described herein can be performed by the processing circuitry of a device of medical device system 2 (such as the processing circuitry of IMD 10). Additionally or alternatively, the techniques described herein can be performed in whole or in part by the processing circuitry of an external device 12 and / or by the processing circuitry of one or more other implanted or external devices or servers not shown. Examples of one or more other implanted or external devices may include a transvenous, subcutaneous, or extravascular pacemaker or implantable cardioverter defibrillator (ICD), a blood analyzer, an external monitor, or a drug pump. The communication circuitry of each of the devices of medical device system 2 allows these devices to communicate with each other. In addition, although the optical sensors and electrodes are described herein as being positioned on the housing of the IMD 10, in other examples, such optical sensors and / or electrodes may be positioned on the housing of another device (such as a transvenous, subcutaneous, or extravascular pacemaker or ICD) implanted inside or outside the patient 4, or coupled to such a device via one or more leads. For example, in the case where the patient 4 has an implanted pacemaker or ICD, the techniques described herein may include sensing signals using electrodes on the pacemaker or ICD for determining StO2 or other parameters. In such examples, electrodes or one or more optical sensors for detecting signals associated with SpO2 and THI may be positioned on one or more external monitoring devices (e.g., wearable monitors). In such examples, one or more of the pacemaker / ICD and one or more external monitoring devices may include: a processing circuit system configured to receive signals from electrodes or optical sensors on the corresponding device; and / or a communication circuit system configured to transmit signals from electrodes or optical sensors to another device (e.g., external device 12) or a server.

[0077] Figure 2-4B Shows Figure 1 Various aspects and example arrangements of the IMD 10. For example, Figure 2 An example physical configuration of IMD 10 is conceptually illustrated. Figure 3 is a block diagram illustrating an example functional configuration of IMD 10 . Figure 4A and Figure 4B Additional views of example physical and functional configurations of IMD 10 are shown. It should be understood that the following descriptions of Figure 2-4BAny of the described examples of IMD 10 may be used to implement the techniques described herein for determining health status and distinguishing between a heart failure condition, lung disease, and anemia as causes of symptoms experienced by patient 4 .

[0078] Figure 2 It is shown Figure 1 A conceptual diagram of an example configuration of an IMD 10. Figure 2 In the example shown, IMD 10 may include a leadless subcutaneous implantable monitoring device having housing 14, light emitter 15, proximal light detector 16A, and distal light detector 16B. Housing 14 may further include first major surface 18, second major surface 20, proximal end 22, and distal end 24. In some examples, IMD 10 may include one or more additional light emitters and / or light detectors (not shown) that may be positioned on one or both of major surfaces 18, 20 of IMD 10. Housing 14 encloses the electronic circuitry within IMD 10 and protects the circuitry contained therein from fluids such as bodily fluids.

[0079] exist Figure 2 In the example shown, IMD 10 is defined by a length L, a width W, and a thickness or depth D. In this example, IMD 10 is in the form of an elongated rectangular prism, wherein length L is significantly greater than width W, and wherein width W is greater than depth D. However, other configurations of IMD 10 are contemplated, such as, for example, wherein the relative proportions of length L, width W, and depth D are greater than or equal to 100 mm. Figure 2 In one example, the geometry of IMD 10 (e.g., width W greater than depth D) can be selected to allow IMD 10 to be inserted under the patient's skin using minimally invasive surgery and maintained in a desired orientation during insertion. In addition, IMD 10 can include radial asymmetry (e.g., rectangular) along the longitudinal axis of IMD 10, which can help maintain the device in a desired orientation after implantation.

[0080] In general, the length L of IMD 10 may be approximately 20-30 mm, approximately 40-60 mm, or approximately 45-60 mm. In some examples, the width W of major surface 18 may be in the range of approximately 3-10 mm, and may be any single width or range of widths between approximately 3-10 mm. In some examples, the depth D of IMD 10 may be in the range of approximately 2–9 mm. In other examples, the depth D of IMD 10 may be in the range of approximately 2-5 mm, and may be any single depth or range of depths within approximately 2-9 mm. In any such examples, IMD 10 is compact enough to be implanted in the subcutaneous space of patient 4, in the pectoralis region.

[0081] An IMD 10 according to an example of the present disclosure may have a geometry and size designed for ease of implantation and patient comfort. An example of an IMD 10 described in the present disclosure may have a 3 cubic centimeter (cm 3 ) or smaller, 1.5cm 3 or smaller volume, or any volume therebetween. Figure 2 In the example shown in , the proximal end 22 and the distal end 24 are rounded to reduce discomfort and irritation to surrounding tissue once implanted under the skin of the patient 4. In some examples, the configuration of the IMD 10 (including instruments and methods for inserting the IMD 10) is described, for example, in U.S. Patent Publication No. 2014 / 0276928, which is incorporated herein by reference in its entirety. In some examples, the configuration of the IMD 10 is described, for example, in U.S. Patent Publication No. 2016 / 0310031, which is incorporated herein by reference in its entirety.

[0082] exist Figure 2 In the example shown, when IMD 10 is inserted into patient 4, first major surface 18 of IMD 10 faces the skin, while second major surface 20 faces inwardly toward the muscles of patient 4. Thus, first major surface 18 and second major surface 20 may face in a direction along the sagittal axis of patient 4 (see Figure 1 ), and because of the size of IMD 10, this orientation can be maintained after implantation.

[0083] exist Figure 2 In the example shown, the proximal end 22 of the IMD 10 includes a head end assembly 32 having one or more of an integrated antenna 26, an anti-displacement protrusion 34, and a suture hole 36. The integrated antenna 26 is positioned on the same major surface (e.g., the first major surface 18) as the light emitter 15 and can be an integral part of the head end assembly 32. In other examples, the integrated antenna 26 can be formed on a major surface opposite to the light emitter 15, or in yet other examples, can be incorporated into the housing 14 of the IMD 10. The antenna 26 can be configured to transmit or receive electromagnetic signals for communication. For example, the antenna 26 can be configured to transmit signals to or receive signals from a programmer via inductive coupling, electromagnetic coupling, tissue conduction, near field communication (NFC), radio frequency identification (RFID), Bluetooth, WiFi, or other proprietary or non-proprietary wireless telemetry communication schemes. Antenna 26 may be coupled to communication circuitry of IMD 10, which may drive antenna 26 to transmit signals to external device 12, and may transmit signals received from external device 12 to processing circuitry of IMD 10 via the communication circuitry.

[0084] IMD 10 may include several features for maintaining IMD 10 in place once IMD 10 is implanted subcutaneously in patient 4. For example, Figure 2 As shown, housing 14 may include an anti-displacement protrusion 34 positioned proximal to integrated antenna 26. Anti-displacement protrusion 34 may include a plurality of ridges or protrusions extending away from first major surface 18 and may help prevent longitudinal movement of IMD 10 after implantation in patient 4. In other examples, anti-displacement protrusion 34 may be positioned on a major surface opposite proximal electrode 38A and / or integrated antenna 26. In addition, in Figure 2 In the example shown in FIG, head end assembly 32 includes suture holes 36 that provide another way to secure IMD 10 to the patient to prevent movement after insertion. In the example shown, suture holes 36 are positioned adjacent to proximal electrode 38A. In some examples, head end assembly 32 may include a molded head end assembly made of a polymeric or plastic material that may be integrated into or separate from the main portion of IMD 10.

[0085] exist Figure 2 In the example shown, the proximal light detector 16A can be positioned at a distance S from the light emitter 15, and the distal light detector 16B can be positioned at a distance S+N from the light emitter 15. In other examples, the IMD 10 may include only one of the light detectors 16A, 16B, or may include additional light emitters and / or additional light detectors. Together, the light emitter 15 and the light detectors 16A, 16B may include an optical sensor that can be used in the techniques described herein to determine the StO2, SpO2, and THI values ​​of the patient 4. Although the light emitter 15 and the light detectors 16A, 16B are described herein as being positioned on the housing 14 of the IMD 10, in other examples, the light emitter 15 and one or more of the light detectors 16A, 16B may be positioned in the housing of another type of IMD (such as a transvenous, subcutaneous, or extravascular pacemaker or ICD) within the patient 4, or connected to such a device via a lead. Light emitter 15 includes a light source, such as an LED, that can emit light of one or more wavelengths within the visible and / or near infrared (NIR) spectrum. For example, light emitter 15 can emit light of one or more wavelengths of approximately 680 nanometers (nm), 720 nm, 760 nm, 800 nm, or any other suitable wavelength. As discussed in further detail below, the one or more wavelengths of light emitted by light emitter 15 can be used by the processing circuitry of IMD 10 to determine StO2, SpO2, and THI.

[0086] like Figure 2As shown, light emitter 15 can be positioned on head end assembly 32, although in other examples, one or both of light detectors 16A, 16B can be additionally or alternatively positioned on head end assembly 32. In some examples, light emitter 15 can be positioned on a middle portion of IMD 10, such as midway between proximal end 22 and distal end 24. Although light emitter 15 and light detectors 16A, 16B are shown as being positioned on first major surface 18, light emitter 15 and light detectors 16A, 16B can alternatively be positioned on second major surface 20. In some examples, the IMD can be implanted such that when IMD 10 is implanted, light emitter 15 and light detectors 16A, 16B face inward toward the muscles of patient 4, which can help minimize interference from background light outside the body of patient 4. Light detectors 16A, 16B can include glass or sapphire windows (such as those described below with respect to Figure 4B ), or may be positioned beneath a portion of housing 14 of IMD 10 that is made of glass or sapphire, or is otherwise transparent or translucent.

[0087] During the technique for determining the StO2 value of the patient 4, the light emitter 15 can emit light to a target site of the patient 4. The target site may generally include blood within a blood vessel in the interstitial space surrounding the IMD 10 (when the IMD 10 is implanted in the patient 4). The light emitter 15 can emit light directionally, because, such as when the light emitter 15 is disposed on a side of the IMD 10 that includes the first major surface 18, the light emitter can direct the signal to that side of the IMD 10. The target site may include subcutaneous tissue adjacent to the IMD 10 in the patient 4. In one example, the light emitter 15 can deliver a 180 degree light signal, such as 180 degrees along a dimension parallel to the longitudinal axis of the IMD 10. In some examples, the light signal may be a cloud of light directed generally inward, toward the muscle tissue and away from the skin of the patient 4. In some examples, the light signal may take a mean free path, because once the light signal is emitted from the light emitter 15, the light signal may be non-directional.

[0088] The technology for determining the StO2 value can be based on the optical properties of the tissue perfused with blood, which varies according to the relative amount of oxidized and deoxygenated hemoglobin in the microcirculation of the tissue. These optical properties are at least partially due to the different light absorption spectra of oxidized and deoxygenated hemoglobin. Therefore, the oxygen saturation level of the patient's tissue can affect the amount of light absorbed by the blood in the tissue adjacent to the IMD 10 and the amount of light reflected by the tissue. In some cases, the technology for determining StO2 may include distinguishing between the SvO2 and SaO2 components of StO2. For example, the light transmitter 15 can be configured to emit light at the following wavelengths: enabling the processing circuit system of the IMD 10 to determine the current SvO2 and / or SaO2 values ​​based on the current StO2 value. Such a determination can provide information related to the balance or imbalance of oxygen supply and demand in the tissue of the patient 4, thereby reflecting the venous oxygen reserve (i.e., the oxygen remaining after being extracted by the tissue and vital organs). Because SvO2 is a measure of cardiac function, processing circuitry of IMD 10 may use this information to determine the relative impact of cardiac function on the current StO2 value, which may increase confidence in the heart failure state determined by IMD 10 .

[0089] In some example techniques for determining StO2, the light emitter 15 may emit multiple wavelengths of visible light (VIS) and / or NIR light simultaneously or sequentially. Such wavelengths may include approximately 680nm, 720nm, 760nm, and 800nm, or any other suitable wavelength. In some example techniques, the light emitter 15 may emit light of wavelengths as follows: one or more wavelengths capable of shallow penetration into tissue (i.e., tissue relatively close to the IMD 10), and one or more wavelengths capable of deeper penetration into tissue (i.e., tissue further away from the IMD 10). In such examples, the use of wavelengths capable of penetrating tissue to different depths may enable the elimination of measurement errors that may be caused by factors such as fibrous tissue encapsulation that may form around the IMD 10 after implantation. For example, the use of wavelengths capable of penetrating tissue to different depths may enable the isolation of deeper tissue. In such an example, the processing circuitry of IMD 10 can subtract the signal associated with the shallow penetration wavelength received from photodetectors 16A, 16B from the signal associated with the deep penetration wavelength to produce a net measurement of the deeper tissue. In some examples, using wavelengths that can penetrate tissue to different depths can also enable the identification and subtraction of the effects of common-mode errors that affect the signals corresponding to both the shallow penetration wavelength and the deep penetration wavelength. For example, by taking two measurements of two different tissue volumes and determining the difference between the two corresponding signals, the processing circuitry of IMD 10 identifies and reduces the effects of common-mode errors associated with the difference between the two signals, such as tissue formation, adhesions, or tissue content changes.

[0090] Light emitter 15 may include a single photodiode capable of emitting light within a wavelength range suitable for determining StO2. In other examples, light emitter 15 may include multiple photodiodes capable of emitting light within multiple wavelength ranges. Light detectors 16A, 16B may each receive light reflected by tissue from light emitter 15 and generate an electrical signal indicating the intensity of light detected by light detectors 16A, 16B. The processing circuit system of IMD 10 may then evaluate the electrical signals from light detectors 16A, 16B to determine the StO2 value of patient 4. In an example where light emitter 15 simultaneously emits light of multiple wavelengths, the processing circuit system of IMD 10 may evaluate the signals from light detectors 16A, 16B by filtering the signals into different wavelengths corresponding to those wavelengths emitted by light emitter 15. For example, the processing circuitry of IMD 10 may execute a continuous wave near infrared algorithm for measuring light received by photodetectors 16A, 16B using a single depth attenuation at 680, 720, 760, and 800 nm and converting the light received by photodetectors 16A, 16B into two wavelengths at 720 nm (2D 720 ) and 760nm(2D760 ) is used to estimate the local hemoglobin oxygen saturation (StO2) in the tissue, which can reduce the effects of light scattering, chromophores with constant absorption, baseline / instrument drift, and motion artifacts on the determined StO2 value.

[0091] In some examples, the difference between the electrical signals generated by photodetectors 16A, 16B can enhance the accuracy of the StO2 value determined by IMD 10. For example, because tissue absorbs some of the light emitted by light emitter 15, the intensity of the light reflected by the tissue decays as the distance (and tissue volume) between light emitter 15 and photodetectors 16A, 16B increases. Therefore, because photodetector 16B is farther from light emitter 15 (distance S+N) than photodetector 16A is from light emitter 15 (distance S), the intensity of the light detected by photodetector 16B should be less than the intensity of the light detected by photodetector 16A. Since detectors 16A, 16B are very close to each other, the difference between the intensity of the light detected by detector 16A and the intensity of the light detected by detector 16B should be attributed only to the difference in distance from light emitter 15. In some examples, the processing circuit system of IMD 10 can use the difference between the electrical signals generated by photodetectors 16A, 16B in addition to the electrical signals themselves when determining the StO2 value of patient 4.

[0092] Light emitter 15 may also emit light into a target site on patient 4 during the technique for determining an SpO2 value for patient 4 that may be used as an approximation of SaO2. As with the target site for determining an StO2 value for patient 4 described above, the target site for determining SpO2 may generally include blood within blood vessels in the interstitial space surrounding IMD 10 (when IMD 10 is implanted in patient 4). The technique for determining an SpO2 value for patient 4 may include using one or more of the components of IMD 10 used in the technique for determining an StO2 value for patient 4, although the wavelength of light emitted by light emitter 15 for determining the SpO2 value may be different from the wavelength used for determining the StO2 value.

[0093] For example, a technique for determining SpO2 may include using light emitter 15 to emit light of one or more VIS wavelengths (e.g., approximately 600 nm) and one or more NIR wavelengths (e.g., approximately 850-940 nm). In some such examples, the processing circuitry of IMD 10 may control light emitter 15 to sequentially emit light of one or more VIS wavelengths and one or more NIR wavelengths for a duration such as 10-30 seconds. Photodetectors 16A, 16B may each receive light reflected by tissue from light emitter 15 and generate an electrical signal indicating the intensity of light detected by photodetectors 16A, 16B. The processing circuitry of IMD 10 may then process the signals generated by photodetectors 16A, 16B during the entire or partial duration. The combination of VIS wavelengths and NIR wavelengths may help the processing circuitry of IMD 10 distinguish oxygenated hemoglobin from deoxygenated hemoglobin in the blood of patient 4, because oxygenated hemoglobin absorbs NIR light more than VIS light, while deoxygenated hemoglobin absorbs VIS light more than NIR light. By comparing the amount of VIS light detected by photodetectors 16A, 16B to the amount of NIR light detected by photodetectors 16A, 16B, the processing circuitry of IMD 10 can determine the relative amounts of oxidized and deoxygenated hemoglobin in the blood of patient 4. For example, if the amount of oxidized hemoglobin in the blood of patient 4 decreases, the amount of VIS light detected by photodetectors 16A, 16B increases, and the amount of NIR light detected by photodetectors 16A, 16B decreases. Similarly, if the amount of oxidized hemoglobin in the blood of patient 4 increases, the amount of VIS light detected by photodetectors 16A, 16B decreases, and the amount of NIR light detected by photodetectors 16A, 16B increases.

[0094] To determine the proportion of oxygenated hemoglobin attributable to pulsating blood volume, and therefore determine SpO2, the processing circuitry of IMD 10 may also determine the amount of fluctuations in light absorption that occur during the cardiac cycle of patient 4. Because light absorption increases during systole as blood volume increases and decreases during diastole as blood volume decreases, the processing circuitry of IMD 10 may determine the fluctuations in light absorption that occur during the cardiac cycle of patient 4, attributing the value of the fluctuations to pulsating (i.e., arterial) blood. The processing circuitry of IMD 10 may then determine the SpO2 value for patient 4 based on a combination of the proportion of oxygenated hemoglobin in patient 4's blood and the value of the fluctuations in light absorption that occur during the cardiac cycle of patient 4.

[0095] For example, processing circuitry of IMD 10 may evaluate signals received from photodetectors 16A, 16B to determine an SpO2 value (e.g., “signal,” or ratio “R”) for patient 4 by determining a ratio of light absorption at a VIS wavelength (e.g., approximately 600 nm) to light absorption at a NIR wavelength (e.g., approximately 850 nm) according to the following equation:

[0096]

[0097] Among them (AC / DC) 600 is the ratio of light absorption by arterial blood to light absorption by other substances (e.g., venous blood or other tissues) at an example VIS wavelength of 600 nm, and (AC / DC) 850 is the ratio of light absorption by arterial blood to light absorption by other substances at an example NIR wavelength of 850 nm. Because SpO2 can be an approximation of SaO2, determining the ratio of light absorption by arterial blood to light absorption by other substances at VIS and NIR wavelengths can enable processing circuitry of IMD 10 to determine an SpO2 value.

[0098] During the technique for determining the THI value of the patient 4, the light emitter 15 may emit light to a target site of the patient 4. As with the target sites for determining the StO2 and SpO2 values ​​of the patient 4 described above, the target site for determining the THI may generally include the interstitial space around the IMD 10 (when the IMD 10 is implanted in the patient 4). The technique for determining the THI value of the patient 4 may include using one or more of the techniques and components of the IMD 10 described above with respect to the technique for determining the StO2 or SpO2 values ​​of the patient 4, although in some examples, the wavelength of the light emitted by the light emitter 15 for determining the THI value may be different from the wavelength used to determine the StO2 and SpO2 values. In some other examples, such a technique may include further processing of the signals used in the technique for determining the StO2 and SpO2. For example, the technique for determining the THI may include using the light emitter 15 to emit light of one or more (e.g., each) NIR wavelengths of approximately 680 nm, 720 nm, 760 nm, and 800 nm to measure the THI value of the tissue volume of the patient 4. In some examples, the emitted wavelengths may be used to determine a StO2 value for a tissue volume of patient 4, and the processing circuitry of IMD 10 may then determine a THI value corresponding to the tissue volume based on the StO2 value. In some examples, the processing circuitry of IMD 10 may determine the THI value according to the following equation:

[0099]

[0100] Among them, MSO2 is the linear slope coefficient value, 2D 720 is a second derivative attenuation measurement centered at 720 nm, and PSF is a probe scaling factor that can be used to obtain a common THI scaling between different optical probe spacings or optical path lengths. As with the techniques for determining StO2 and SpO2 values, the techniques for determining THI values ​​(including using the light emitter 15 to emit light at more than one NIR wavelength) can advantageously provide enhanced detection of hemoglobin chromophores in tissue while reducing the effects of confounding factors such as optical coupling, heterogeneity, scaling, changes in tissue composition, and / or detection of other chromophores that may be present in the tissue (e.g., myoglobin).

[0101] In an example where the method of determining the health state of the patient 4 includes determining one or more of a current HR value, a current HRV value, or a current Z value of the patient 4, the IMD 10 may include a proximal electrode 38A and a distal electrode 38B. As shown in the illustrated example, the proximal electrode 38A may be positioned on the head end assembly 32, and the distal electrode 38B may be formed by an uninsulated distal portion of the conductive shell 14. The proximal electrode 38A and the distal electrode 38B may be positioned near the proximal end 22 and the distal end 24 of the IMD 10, respectively, so that the spacing between the proximal electrode 38A and the distal electrode 38B is in the range of about 30-55 mm, about 35-55 mm, or about 40-55 mm, or more generally in the range of about 25-60 mm. In some examples, the IMD 10 may also include one or more additional electrodes 38C, 38D positioned on one or both of the major surfaces 18, 20 of the IMD 10. In any such examples, the electrical feedthroughs may provide electrical connection of the electrodes 38A- 38D and antenna 26 to circuitry within the housing 14 .

[0102] exist Figure 2 In the example shown, proximal electrode 38A is proximal to proximal end 22 and distal electrode 38B is proximal to distal end 24 of IMD 10. In this example, distal electrode 38B is not limited to a flat, outwardly facing surface, but may extend in a three-dimensional curved configuration from first major surface 18, around circular edge 28 or end surface 30, and onto second major surface 20. As shown, proximal electrode 38A is positioned on first major surface 18 and is substantially flat and outwardly facing. However, in other examples not shown here, both proximal electrode 38A and distal electrode 38B may be similarly Figure 2 The proximal electrode 38A shown may be constructed similarly, or both may be constructed similarly. Figure 238B shown. Any of electrodes 38A-38D may be made of a biocompatible conductive material. For example, any of electrodes 38A-38B may be formed of any of stainless steel, titanium, platinum, iridium, or alloys thereof. Additionally, the electrodes of IMD 10 may be coated with materials such as titanium nitride or fractal titanium nitride, but other suitable materials and coatings may be used for these electrodes.

[0103] When the IMD 10 is implanted subcutaneously in the patient 4, the proximal electrode 38A and the distal electrode 38B can be used to sense the cardiac EGM signal (e.g., ECG signal). In the technology described herein, the processing circuit system of the IMD 10 can determine the HR and / or HRV value based on the cardiac ECG signal. In some examples, the processing circuit system of the IMD 10 can also determine whether the cardiac ECG signal of the patient 4 indicates an arrhythmia (e.g., the presence or absence of atrial fibrillation and the ventricular rate during atrial fibrillation) or other abnormality, and the processing circuit system of the IMD 10 can determine the arrhythmia or other abnormality when determining whether the cardiac function of the patient 4 has changed. The cardiac ECG signal can be stored in the memory of the IMD 10, and data derived from the cardiac ECG signal can be transmitted to another medical device, such as the external device 12, via the integrated antenna 26.

[0104] In some examples, one or both of electrodes 38A and 38B may also be used to detect a subcutaneous impedance value Z for assessing the congestion state of patient 4, and / or may be used by the communication circuit system of IMD 10 for TCC communication with external device 12. For example, the processing circuit system of IMD 10 may determine the Z value of patient 4 based on the signals received from electrodes 38A, 38B. The processing circuit system of IMD 10 may generate one of the current or voltage signals, deliver the signal via electrodes 38A, 38B, and measure the other resulting current or voltage. Thus, the processing circuit system of IMD 10 may determine an impedance signal based on the delivered current or voltage and the measured voltage or current. In some examples, a decreasing trend in the Z value over time may indicate an increased likelihood of fluid overload and hospitalization for heart failure due to pulmonary congestion.

[0105] In some cases, it may be advantageous to use a separate electrode pair for determining the current HR / HRV and Z value of patient 4. For example, in addition to electrodes 38A, 38B or in place of electrodes 38A, 38B, electrodes 38C and 38D may be used to detect subcutaneous impedance value Z. In other examples, electrodes 38A, 38B may be used to detect Z, while electrodes 38C, 38D may be used for ECG sensing. Using a separate electrode pair for ECG sensing impedance measurement can help reduce the possibility that the signal generated to determine the Z value may interfere with the signal sensed by the electrode pair used for ECG sensing. In addition, using separate electrode pairs to determine the current Z value and HR / HRV value of patient 4 can better adapt one or more aspects (e.g., size or spacing) of electrodes 38A-38D to the assigned function of each electrode.

[0106] In some examples, the IMD 10 may include one or more additional sensors, such as one or more accelerometers (not shown). Such accelerometers may be 3D accelerometers configured to generate signals indicative of one or more types of motion of the patient, such as overall body motion of the patient (e.g., activity), patient posture, motion associated with the beating of the heart, or coughing, rales, or other respiratory abnormalities. In some examples, one or more of such accelerometers may be used in conjunction with the light emitter 15 and light detectors 16A, 16B to determine a ballistocardiogram (i.e., a measure of motion corresponding to the ejection of blood during heart contraction), which may be used by the processing circuitry of the IMD 10 to determine a Z value in lieu of or in addition to using an ECG signal from a pair of electrodes 38A-38D. Additionally or alternatively, one or more of the parameters monitored by the IMD 10 (i.e., StO2, SpO2, THI, Z, HR, or HRV) may fluctuate in response to changes in one or more of such types of motion. For example, an increase in HR may sometimes be attributed to an increase in patient activity (e.g., exercise, or other physical activity compared to inactivity) or to a change in the patient's posture, and not necessarily to a change in cardiac function caused by the progression of heart failure. Therefore, in some methods of determining the health state of patient 4, it may be advantageous to consider such fluctuations when determining whether a change in a parameter (such as HR) that exceeds a threshold indicates a change in the corresponding physiological function.

[0107] In such an example, the processing circuit system of IMD 10 may receive one or more signals from one or more accelerometers of IMD 10 and determine the value of one or more patient activity parameters (such as, overall body movement). In this example, the processing circuit system of IMD 10 may cross-reference the determined patient activity value with the value of one or more other parameters (such as HR value). If the patient activity value meets the threshold, the processing circuit system of IMD 10 may determine that the change of the current HR value relative to the baseline HR value does not indicate a change in the cardiac function of patient 4, otherwise the change of the current HR value relative to the baseline HR value may indicate a change in cardiac function. In this instance, the processing circuit system of patient 4 may designate the HR value as an outlier and not use it to determine the health status of patient 4. In some examples, the processing circuit system of IMD 10 may cross-reference the determined activity or posture value with a different scaling factor to be applied to the StO2, SpO2, THI, Z, HR or HRV value before comparing it with the threshold or with a different threshold (the different threshold is used to compare with the StO2, SpO2, THI, Z, HR or HRV value). Although the processing circuitry of IMD 10 is described above as being configured to receive signals from one or more accelerometers, light emitters 15, light detectors 16A, 16B, and / or electrodes 38A-38D of IMD 10 and determine values ​​of one or more parameters of patient 4 based on these signals, any steps described herein as being performed by the processing circuitry of IMD 10 may be performed by the processing circuitry of one or more devices. For example, the processing circuitry of external device 12 or any other suitable implantable or external device or server may be configured to receive signals from one or more accelerometers, light emitters 15, light detectors 16A, 16B, and / or electrodes 38A-38D of IMD 10 via the communication circuitry of IMD 10.

[0108] Figure 3 It is shown Figure 1 and Figure 210. In the example shown, IMD 10 includes processing circuitry 50, sensing circuitry 52, communication circuitry 54, memory 56, switch circuitry 58, sensor 62, timing / control circuitry 64 (one or more of which may be disposed within housing 14 of IMD 10 in addition to previously described electrodes 38A-38D), and light emitter 15. In some examples, memory 56 includes computer-readable instructions that, when executed by processing circuitry 50, cause IMD 10 and processing circuitry 50 to perform various functions attributed to IMD 10 and processing circuitry 50 herein. Memory 56 may include any volatile, nonvolatile, magnetic, optical, or electrical medium, such as random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other digital medium.

[0109] Processing circuit system 50 may include fixed function circuit system and / or programmable processing circuit system. Processing circuit system 50 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or an equivalent discrete or analog logic circuit system. In some examples, processing circuit system 50 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuit systems. The functions of processing circuit system 50 attributed to this article may be implemented as software, firmware, hardware, or any combination thereof.

[0110] The timing / control circuit system 64 may be embodied as hardware, firmware, software, or any combination thereof. In some examples, the timing / control circuit system 64 may include a dedicated hardware circuit (such as an ASIC) separated from other processing circuit system 50 components (such as a microprocessor) or a software module executed by a component (e.g., a microprocessor or an ASIC) of the processing circuit system 50. The timing / control circuit system 64 may monitor the passage of time to determine when the monitoring period has passed, and help control the IMD 10 to measure the current values ​​of StO2, SpO2, and THI of the patient 4. The timing / control circuit system 64 may also control the IMD 10 to transmit the heart failure status of the patient 4 to the external device 12 at the end of the corresponding interval.

[0111] In some examples, the timing / control circuit system 64 can be configured to associate the current values ​​of StO2, SpO2, and THI (and / or the current values ​​of Z, HR, or HRV) with a particular time of day (such as daytime or nighttime) so that the processing circuit system 50 can take into account the circadian rhythm of the patient 4 when determining the heart failure state, lung state, and / or anemia state of the patient 4. For example, the HR value of the patient 4 can generally decrease when the patient 4 is asleep (e.g., nighttime) and increase when the patient 4 is awake (e.g., daytime). Therefore, the IMD 10 can be configured to use different (e.g., lower) baseline values ​​and / or thresholds for specific parameters (such as HR) when the patient 4 is likely to be asleep than when the patient 4 is likely to be awake. In some examples where the IMD 10 includes one or more accelerometers, the processing circuit system 50 can cross-reference the time of day indicated by the timing and control circuit with the accelerometer data, such as to confirm whether the patient 4 is asleep or awake (as predicted based on the time of day). In this way, timing / control circuitry 64 may enhance the ability of IMD 10 to accurately determine the health status of patient 4 .

[0112] In addition to the sensed physiological parameters of the patient 4 (e.g., determined values ​​of StO2, SpO2, and THI), the memory 56 may also store one or more time intervals for timing the measurements of StO2, SpO2, and THI by the processing circuit system 50 in the stored measurements / intervals 68. For example, the intervals 68 stored by the memory 56 may instruct the processing circuit system 50 to measure the current values ​​of StO2, SpO2, and THI of the patient 4 every hour, several times a day, every day, or at any other suitable interval. The stored measurements / intervals 68 may also include intervals at which the processing circuit system may be configured to transmit the heart failure state of the patient 4 to the external device 12, such as every day, every week, or at any other suitable interval. In some examples, the processing circuit system 50 may select intervals for measuring StO2, SpO2, and THI or for transmitting the heart failure state of the patient 4 from the stored measurements / intervals 68. In other examples, the clinician may select interval values ​​according to the needs of the patient 4 , such as by using an application on a tablet or other smart device, which in some examples may be the external device 12 .

[0113] like Figure 3As shown, the memory 56 may also include one or more tables 70 for storing baseline values, threshold values, and evidence level values. As described above, in some examples, the processing circuit system 50 of the IMD 10 may be configured to determine baseline values ​​of StO2, SpO2, and THI during the learning phase of the IMD 10, which may then be stored in the table 70. In addition, the table 70 may include pre-programmed baseline values ​​that the clinician may select for the patient 4 during the setup of the IMD 10, or baseline values ​​that the clinician may manually enter based on the clinician's assessment of the patient 4. The processing circuit system 50 may also be configured to determine a threshold value for the deviation of the current value of StO2, SpO2, and THI from the baseline value, and store the threshold value in the table 70. In some examples, the processing circuit system 50 may determine such a threshold value based at least in part on the baseline value selected for the patient 4. In addition to the baseline value, the table 70 may also include a threshold value that the clinician may select for the patient 4 during the setup of the IMD 10, or a threshold value that the clinician may manually enter based on the clinician's assessment of the patient 4. Table 70 may also include values ​​for the level of evidence that may be associated with certain values ​​of StO2, SpO2, and THI used by processing circuit system 50 to determine a diagnostic score for patient 4. As described above, the health state may include a diagnostic score for patient 4, which in some examples may be a composite diagnostic score based on a combination of values ​​for the level of evidence associated with one or more current values ​​of StO2, SpO2, and THI for patient 4.

[0114] Sensing circuitry 52 and communication circuitry 54 may be selectively coupled to electrodes 38A-38D via switch circuitry 58, as controlled by processing circuitry 50. Sensing circuitry 52 may monitor signals from electrodes 38A-38D to monitor electrical activity of the heart (e.g., to generate an ECG for HR / HRV determination) or subcutaneous tissue impedance Z (e.g., as a measure of hyperemia). Sensing circuitry 52 may also monitor signals from sensor 62, which may include photodetectors 16A, 16B and any other photodetectors or accelerometers that may be positioned on IMD 10. In some examples, sensing circuitry 52 may include one or more filters and amplifiers for filtering and amplifying signals received from one or more of electrodes 38A-38D and / or photodetectors 16A, 16B.

[0115] In some examples, processing circuit system 50 may also include a rectifier, a filter and / or an amplifier, a sense amplifier, a comparator and / or an analog-to-digital converter. Upon receiving signals from electrodes 38A-38D and light detectors 16A, 16B via sensing circuit system 52, processing circuit system 50 may determine a current value of each of StO2, SpO2, and THI for patient 4. The processing circuit system may then compare the current values ​​of StO2, SpO2, and THI with the baseline levels stored in table 70 and determine whether the difference between the current value and the corresponding baseline level exceeds the corresponding threshold value stored in table 70.

[0116] The threshold values ​​stored in the table 70 may be associated with changes in certain parameters of the health state of the patient 4. For example, a threshold value corresponding to one or more of the StO2, Z, HR, or HRV values ​​may be associated with a change in the heart failure state of the patient 4, while a threshold value corresponding to the SpO2 value may be associated with a change in the lung state of the patient 4, and a threshold value corresponding to the THI value may be associated with a change in the anemia state of the patient 4. In some examples, the processing circuit system 50 may identify a level of evidence value associated with the current values ​​of StO2, SpO2, and THI of the patient 4, and determine a diagnostic score associated with the combination of the levels of evidence. The processing circuit system 50 may store the determined current value, the associated level of evidence, and the diagnostic score in the stored measurement / interval 68 of the memory 56 together with an indication of the date and time of the measurement. At the same time or thereafter, the processing circuit system 50 may transmit the diagnostic score and / or one or more other indicators of the health state of the patient 4 to the external device 12 via the communication circuit system 54.

[0117] Communication circuitry 54 may include any suitable hardware, firmware, software, or any combination thereof, for communicating with another device, such as external device 12 or another IMD or sensor, such as a pressure sensing device. Under the control of processing circuitry 50, communication circuitry 54 may receive downlink telemetry from external device 12 or another device via an internal or external antenna (e.g., antenna 26), and send uplink telemetry to external device 12 or another device. In some examples, communication circuitry 54 may communicate with external device 12. Additionally, processing circuitry 50 may communicate with external device 12 via an external device, such as external device 12, and a computer network, such as a Medtronic® EMBODIMENT developed by Medtronic plc of Dublin, Ireland. Network) to communicate with networked computing devices.

[0118] A clinician or other user may retrieve data from IMD 10 using external device 12 or by using another local or networked computing device configured to communicate with processing circuitry 50 via communication circuitry 54. The clinician may also use external device 12 or another local or networked computing device to program parameters of IMD 10. In some examples, the clinician may select a baseline value, threshold value, time of day, or number of measurements to be completed in a period (e.g., a day) for StO2, SpO2, and THI measurements, and may program a level of evidence to be associated with the parameters StO2, SpO2, and THI.

[0119] The various components of IMD 10 may be coupled to a power source, which may include a rechargeable or non-rechargeable battery located within housing 14 of IMD 10. Non-rechargeable batteries may be selected to last for several years, while rechargeable batteries may be charged inductively from an external device, for example, on a daily or weekly basis.

[0120] Figure 4A and Figure 4B Two additional example IMDs are shown that may be used with Figure 1-3 The IMD 10 is substantially similar, but may include one or more additional features. Figure 4A and Figure 4B Components may not necessarily be drawn to scale but may be exaggerated to show details. Figure 4A is a block diagram of a top view of an example configuration of IMD 10A. Figure 4B is a block diagram of a side view of an example IMD 10B, which may include insulating layers as described below.

[0121] Figure 4A It shows that it can be Figure 1 A conceptual diagram of another example IMD 10A is substantially similar to IMD 10. Figure 1-3 In addition to the components shown in Figure 4A The example of IMD 10 shown in FIG. 1 may also include a main body portion 72 and an attachment plate 74. Attachment plate 74 may be configured to mechanically couple head end 32 to main body portion 72 of IMD 10A. Main body portion 72 of IMD 10A may be configured to receive Figure 3 One or more of the internal components of IMD 10 are shown, such as one or more of processing circuitry 50, sensing circuitry 52, communication circuitry 54, memory 56, switching circuitry 58, internal components of sensor 62, and timing / control circuitry 64. In some examples, body portion 72 may be formed of one or more of titanium, ceramic, or any other suitable biocompatible material.

[0122] Figure 4B is shown to include Figure 1 A conceptual diagram of another example IMD 10B having substantially similar components to IMD 10 is shown. Figure 1-3 In addition to the components shown in Figure 4B The example of the IMD 10B shown in FIG. 1 may also include a wafer-scale insulating cover 76 that can help isolate electrical signals from being transmitted between the electrodes 38A-38D and / or the photodetectors 16A, 16B on the housing 14B and the processing circuit system 50. In some examples, the insulating cover 76 can be positioned above the open housing 14 to form a housing for the components of the IMD 10B. One or more components of the IMD 10B (e.g., antenna 26, light emitter 15, photodetectors 16A, 16B, processing circuit system 50, sensing circuit system 52, communication circuit system 54, switch circuit system 58, and / or timing / control circuit system 64) can be formed on the bottom side of the insulating cover 76, such as by using flip-chip technology. The insulating cover 76 can be flipped onto the housing 14B. When flipped and placed on the housing 14B, the components of the IMD 10B formed on the bottom side of the insulating cover 76 can be positioned in a gap 78 defined by the housing 14B.

[0123] Insulating cover 76 can be configured to not interfere with the operation of IMD 10B. For example, one or more of electrodes 38A-38D can be formed or placed on or above the top of insulating cover 76 and electrically connected to switch circuitry 58 via one or more through holes (not shown) formed through insulating cover 76. In addition, to enable the IMD to determine the values ​​of StO2, SpO2, and THI, at least a portion of insulating cover 76 can be transparent to NIR or visible light wavelengths emitted by light emitter 15 and detected by light detectors 16A, 16B, which in some examples can be positioned on the bottom side of insulating cover 76, as described above.

[0124] In some examples, light emitter 15 may include a filter between light emitter 15 and insulating cover 76 that may limit the spectrum of emitted light to a narrow band. Similarly, light detectors 16A, 16B may include a filter between light detectors 16A, 16B and insulating cover 76 so that light detectors 16A, 16B detect light from a narrow spectrum, typically at a longer wavelength than the emission spectrum. Other optical elements that may be included in IMD 10B may include index matching layers, anti-reflection coatings, or optical barriers that may be configured to block light emitted laterally by light emitter 15 from reaching light detector 40.

[0125] The insulating cover 76 can be formed of sapphire (i.e., corundum), glass, parylene, and / or any other suitable insulating material. Sapphire can have a transmittance greater than 80% for wavelengths in the range of about 300nm to about 4000nm, and can have a relatively flat profile. In the case of variation, different transmissions at different wavelengths can be compensated, such as by using a ratiometric method. In some examples, the insulating cover 76 can have a thickness of about 300 microns to about 600 microns. The housing 14B can be formed of titanium or any other suitable material (e.g., a biocompatible material) and can have a thickness of about 200 microns to about 500 microns. These materials and dimensions are examples only, and other materials and other thicknesses are possible for the device of the present disclosure.

[0126] Figure 5 is a functional block diagram illustrating an example system including access point 90, network 92, external computing devices such as server 94, and one or more other computing devices 100A-100N that may be coupled to IMD 10, external device 12, and external device 12 via network 92. In this example, IMD 10 may use telemetry circuitry to communicate with external device 12 via a first wireless connection and with access point 90 via a second wireless connection. Figure 5 In the example of FIG. 8 , access point 90 , external device 12 , server 94 , and computing devices 100A- 100N are interconnected and can communicate with each other via network 92 .

[0127] The access point 90 may include a device that is connected to the network 92 via any of a variety of connections, such as a telephone dial-up, a digital subscriber line (DSL), or a cable modem connection. In other examples, the access point 90 may be coupled to the network 92 via different forms of connections, including wired or wireless connections. In some examples, the access point 90 may be a user device that may be co-located with the patient, such as a tablet computer or a smartphone. As discussed above, the IMD 10 may be configured to transmit data, such as current values ​​and heart failure status, to the external device 12. In addition, the access point 90 may query the IMD 10, such as periodically or in response to a command from the patient or the network 92, in order to retrieve current values ​​or heart failure status determined by the processing circuit system 50 of the IMD 10, or other operational or patient data from the IMD 10. The access point 90 may then transmit the retrieved data to the server 94 via the network 92.

[0128] In some cases, server 94 may be configured to provide a secure storage location for data that has been collected from IMD 10 and / or external device 12. In some cases, server 94 may compile the data in a web page or other file for viewing by a trained professional (such as a clinician) via computing devices 100A-100N. Common network technologies and functions may be utilized to implement Figure 5 One or more aspects of the system shown, the general network technology and functionality may be similar to that developed by Medtronic plc of Dublin, Ireland. Network technologies and capabilities provided by the network.

[0129] In some examples, one or more of the computing devices 100A-100N (e.g., device 100A) may be a tablet or other smart device located with a clinician, through which the clinician may program, receive alerts from, and / or query the IMD 10. For example, the clinician may access the StO2, SpO2, and THI measurements of patient 4 through device 100A, such as when patient 4 is between clinic visits, to check the health status of patient 4 as needed. In some examples, the clinician may enter instructions for medical intervention for patient 4 into an application in device 100A, such as based on the heart failure status of patient 4 determined by IMD 10, or based on other patient data known to the clinician. Device 100A may then transmit the instructions for medical intervention to another computing device (e.g., device 100B) of the computing devices 100A-100N located with patient 4 or a caregiver of patient 4. For example, such instructions for medical intervention may include instructions for changing drug dosage, timing or selection, instructions for arranging visits to clinicians, or instructions for seeking medical assistance. In another example, device 100B may generate an alarm to patient 4 based on the health status of patient 4 determined by IMD 10, which may enable patient 4 to actively seek medical assistance before receiving instructions for medical intervention. In some examples, the alarm generated by device 100B may include an updated diagnosis of one or more of heart failure illness, lung disease and anemia, such as diagnosing that the heart failure illness of patient 4 has progressed from a first type of heart failure illness to a second type of heart failure illness. In this way, patient 4 may be authorized to take action as needed to address his or her health status, which may help improve the clinical outcome of patient 4.

[0130] Figure 6-122 is a flowchart illustrating various techniques for determining a patient's health status based on a comparison of the patient's current StO2 value, SpO2 value, and THI value with corresponding baseline values ​​according to an example of the present disclosure. As described herein, one or more components of system 2 may be used to employ Figure 6-12 The technology shown, one or more of which has been referenced above Figure 1-5 Although described as being performed by IMD 10, the processing circuitry and memory of other devices in the medical device system may be performed in whole or in part. Figure 6-12 For example, although for clarity, the processing circuitry 50 of the IMD is described as performing Figure 6-9 In most of the example techniques shown in , but in other examples, one or more devices (e.g., external device 12 or other external device or server) or a clinician may perform one or more steps attributed below to processing circuitry 50 of IMD 10.

[0131] Figure 6 1 is a flow chart illustrating an example technique for determining a health status of patient 4 based on a comparison of current tissue oxygen saturation values, impedance values, and pulse transit time values ​​(i.e., StO2, SpO2, and THI) of patient 4 by processing circuitry 50 of IMD 10 with corresponding baseline values ​​stored in table 70 of memory 56, and transmitting the health status to external device 12. Figure 6 In the example of , IMD 10 may determine a baseline StO2 value, SpO2 value, and THI value for patient 4 (step 110). For example, such baseline StO2 value, SpO2 value, and THI value may represent baseline first, second, and third optical signals received by processing circuit system 50 of IMD 10 from at least one optical sensor (such as, one or more of optical detectors 16A, 16B). In some examples, as described above with respect to Figure 1 As discussed, IMD 10 may determine the baseline value during a learning phase of IMD 10 after IMD 10 is implanted in patient 4. Such a learning phase may occur after implantation of IMD 10, when the heart failure condition of patient 4 is stabilized (eg, compensated).

[0132] During the learning phase, the IMD 10 can periodically determine the current values ​​of StO2, SpO2, and THI of the patient 4 based on the signals received from one or more of the electrodes 38A-38D, the light emitter 15, and the light detectors 16A, 16B, and store these values ​​in the stored measurements / intervals 68. The IMD 10 can then analyze the collected values ​​of StO2, SpO2, and THI to determine the baseline value of the patient 4 (step 110). In some examples, the IMD 10 can reject any outliers of StO2, SpO2, and THI and average the remaining measured values, but other data analysis methods can be used to determine the baseline value based on the collected values. In other examples, the clinician can determine the baseline value of the patient 4 by selecting the baseline value stored in the table 70 of the IMD 10, which can be used as part of the start-up phase of the treatment after the IMD 10 is implanted in the patient 4. In some examples, the IMD 10 can also determine the threshold value of each of the baseline StO2, SpO2, and THI values ​​of the patient 4. For example, processing circuit system 50 may determine a threshold value for patient 4 by selecting a threshold value from table 70 based on the determined baseline value for patient 4. In other examples, a clinician may select a threshold value for patient 4, which the IMD then associates with the baseline values ​​of StO2, SpO2, and THI for patient 4 in table 70.

[0133] After IMD 10 determines baseline values ​​and / or threshold values ​​for StO2, SpO2, and THI for patient 4, such as at the end of a learning phase of IMD 10, IMD 10 may begin determining current values ​​for StO2, SpO2, and THI for patient 4 (step 112). For example, processing circuitry 50 of IMD 10 may receive signals from one or more of electrodes 38A-38D, light emitters 15, and light detectors 16A, 16B and determine current values ​​for StO2, SpO2, and THI based on these signals, as described above with reference to FIG. Figure 1-3 Next, processing circuit system 50 of IMD 10 may compare the current StO2 value, SpO2 value, and THI value of patient 4 with the corresponding baseline values ​​of patient 4 stored in table 70, and determine the difference between each of the current values ​​of StO2, SpO2, and THI and the corresponding baseline value (step 114). In some examples, processing circuit system 50 may also determine whether the difference between one or more of the current values ​​and the corresponding baseline value meets a threshold.

[0134] Based on the difference between the current value and the baseline value determined at step 114 and / or the determination of whether one or more of the differences exceed a threshold, the processing circuit system 50 determines the corresponding heart failure state, lung state, and anemia state of the patient 4 (step 116). The processing circuit system 50 then determines the health state of the patient 4 based on the combination of the heart failure state, lung state, and anemia state (step 118). In some examples, the threshold value may be an absolute value of a percentage of the baseline value. For example, if the baseline value of StO2 = X, the threshold value of StO2 may be X ± 0.2X. In other examples, one or more of StO2, SpO2, and THI may be associated with multiple thresholds corresponding to different percentages of the baseline value, which may take into account the difference in importance between values ​​exceeding one or more baseline values ​​and values ​​less than the baseline value. For example, if the baseline value of StO2 = X, the threshold value of StO2 may be X + 0.2X and X – 0.1X, where the importance of the value of StO2 less than X is relatively higher than the value of StO2 greater than X. In any such examples, the threshold value may be based on a deviation from a corresponding baseline value, such as a standard deviation or any other suitable statistical function.

[0135] IMD 10 can repeat steps 112-118 to periodically determine the updated health status of patient 4, such as daily, weekly, monthly, or any other suitable period. In some examples, the health status of patient 4 may include a diagnostic score that indicates the possibility that patient 4 may need hospitalization within a certain period of time based on changes in one or more of the cardiac function, pulmonary function, or blood function of patient 4. For example, processing circuit system 50 can determine the diagnostic score of patient 4 based on a combination of values ​​of one or more evidence levels associated with the current values ​​of StO2, SpO2, and THI. Typically, the evidence level associated with more severe tissue perfusion deficiency (as indicated by relatively low StO2), arterial perfusion deficiency (as indicated by relatively low SpO2), and tissue hemoglobin index deficiency (as indicated by relatively low THI) can be compared to the evidence level associated with the less severe parameters of the corresponding ones in heart failure, lung disease, and anemia, and has a higher value. Thus, a higher diagnostic score, compared to a lower diagnostic score, may indicate that Patient 4 is at a higher risk for acute decompensation and / or hospitalization or other adverse medical event over a certain time period, or that particular symptoms are caused by a particular underlying condition of Patient 4's heart, lungs, or blood.

[0136] In some examples, the diagnostic score may also include an indication of which of Patient 4's heart failure condition, lung disease, or anemia is most likely to cause Patient 4 to require hospitalization over a period of time, and / or which of Patient 4's underlying conditions of the heart, lungs, or blood is most likely to cause a particular symptom. For example, the diagnostic score may indicate that there is a 70% chance that the shortness of breath experienced by Patient 4 is caused by a heart failure condition, a 20% chance that it is caused by lung disease, and a 10% chance that it is caused by anemia. In such an example, the processing circuit system 50 therefore determines that the heart failure condition is the most likely cause of the shortness of breath experienced by Patient 4, and may include this determination in the diagnostic score. In some examples, the processing circuit system 50 may include the following in the diagnostic score: Figure 1 described) or integration of prior data specific to patient 4 with current measurements specific to patient 4 (e.g., current values ​​of StO2, SpO2, or THI for patient 4), such as by using Bayesian statistics or other machine learning methods, to determine the likelihood that each of heart failure condition, lung disease, and anemia is the cause of patient 4's symptoms.

[0137] Reference below Figure 8 Determination of the health status of patient 4 based on the diagnostic score by processing circuitry 50 is further described. Regardless of whether the health status of patient 4 determined by processing circuitry 50 includes the diagnostic score, processing circuitry transmits the health status of patient 4 to a remote computer, such as external device 12 (step 120).

[0138] Figure 7 is used to determine the reference Figure 6 Flowchart of an example technique for determining baseline or current values ​​of tissue oxygen saturation, pulse oxygen saturation, and tissue hemoglobin index as described above. To determine a current value of StO2 for patient 4, processing circuitry 50 of IMD 10 may monitor the first optical signal. For example, processing circuitry 50 of IMD 10 may cause optical emitter 15 to emit NIR light of one or more wavelengths suitable for StO2 determination, such as described above with respect to Figure 2The wavelength described. The photodetectors 16A, 16B can each receive light reflected by the tissue from the light emitter 15, and generate an electrical signal indicating the intensity of the light detected by the photodetectors 16A, 16B. The processing circuit system of the IMD 10 can then evaluate the electrical signals from the photodetectors 16A, 16B to determine the StO2 value of the patient 4 (step 122). The StO2 value determined at step 122 can be used as the current value StO2 of the patient 4, which is a measure of the tissue oxygen saturation of the patient 4 and is related to the heart failure state of the patient 4. For example, a relatively low StO2 value may indicate that the amount of deoxyhemoglobin subcutaneous tissue near the IMD 10 is relatively high. Therefore, if the current value of StO2 is relatively low and / or lower than the previously measured value of StO2, the patient 4 may be experiencing a decrease in tissue oxygen saturation, which can be reflected in the diagnostic score determined by the processing circuit system 50.

[0139] To determine the current value of SpO2 for patient 4, processing circuitry 50 of IMD 10 may monitor the second optical signal. For example, processing circuitry 50 may cause optical emitter 15 to emit NIR light of one or more wavelengths suitable for SpO2 determination, such as described above with respect to Figure 2 The wavelength described. The photodetectors 16A, 16B can each receive light reflected by the tissue from the light emitter 15, and generate an electrical signal indicating the intensity of the light detected by the photodetectors 16A, 16B. The processing circuit system of the IMD 10 can then evaluate the electrical signals from the photodetectors 16A, 16B to determine the SpO2 value of the patient 4 (step 124). The SpO2 value determined at step 124 can be used as the current value SpO2 of the patient 4, which is a measure of the pulse oxygen saturation of the patient 4 (e.g., an approximation of the arterial oxygen saturation of the patient 4) and is related to the patient's pulmonary state. For example, a relatively low SpO2 value may indicate that the amount of oxygenated blood in the artery near the IMD 10 is relatively low. Therefore, if the current value of SpO2 is relatively low and / or lower than the previously measured value of SpO2, the patient 4 may be experiencing a decrease in pulse oxygen saturation, which can be reflected in the diagnostic score determined by the processing circuit system 50.

[0140] To determine the current value of THI for patient 4, processing circuitry 50 of IMD 10 may monitor the third optical signal. For example, processing circuitry 50 may cause optical emitter 15 to emit NIR light of one or more wavelengths suitable for THI determination, such as described above with respect to Figure 2The wavelength described. The photodetectors 16A, 16B can each receive light reflected by the tissue from the light emitter 15, and generate an electrical signal indicating the intensity of the light detected by the photodetectors 16A, 16B. The processing circuit system of the IMD 10 can then evaluate the electrical signals from the photodetectors 16A, 16B to determine the THI value of the patient 4 (step 126). The THI value determined at step 126 can be used as the current value THI of the patient 4, which is a measure of the tissue hemoglobin index of the patient 4 and is related to the anemic state of the patient 4. For example, a relatively low THI value may indicate that the concentration of hemoglobin in the tissue near the IMD 10 is relatively low relative to the tissue volume. Therefore, if the current value of THI is relatively low and / or lower than the previously measured value of THI, the patient 4 may be experiencing a decrease in the tissue hemoglobin index, which can be reflected in the diagnostic score determined by the processing circuit system 50.

[0141] In some examples, the current value of one or more of StO2, SpO2 and THI may exhibit random variability. In order to address this variability, the comparison of the current diagnostic score and the baseline diagnostic score performed by the processing circuit system 50 may include curve fitting and trend analysis. For example, if the processing circuit system 50 measures the values ​​of StO2, SpO2 and THI several times a day, the processing circuit system can accumulate these values ​​over a period of time (e.g., within several days or several weeks) and fit the cumulative value of each of StO2, SpO2 and THI to the corresponding trend line. The processing circuit system 50 can then use the trend line to project the corresponding current value of StO2, SpO2 and THI. In this way, the processing circuit system 50 can consider random fluctuations when determining the current values ​​of StO2, SpO2 and THI as described above, which can improve the accuracy of the current values ​​of StO2, SpO2 and THI reflecting the heart failure state, lung state and anemia state of the patient 4.

[0142] Figure 8 is a flow chart illustrating an example technique for determining a current diagnostic score for patient 4 by processing circuitry 50 of IMD 10, and determining an updated health state of patient 4 based on a comparison of the current diagnostic score with a baseline diagnostic score. Comparison of patient 4's current diagnostic score with patient 4's baseline diagnostic score may provide additional information regarding changes in patient 4's health state, and may further inform monitoring and treatment decisions and improve clinical outcomes. In some examples, the current diagnostic score may be determined based on a weighted value of the difference between patient 4's current values ​​(StO2, SpO2, and THI) and corresponding baseline values. For example, processing circuitry 50 may determine the difference between the current value of each of StO2, SpO2, and THI and the corresponding baseline value of patient 4, such as with respect to Figure 6Processing circuit system 50 may then determine a weighted value for each of the differences between the current value and the corresponding baseline value. Specifically, processing circuit system 50 determines a weighted value for the difference between the current StO2 and the baseline StO2 of patient 4 (step 130), a weighted value for the difference between the current SpO2 and the baseline SpO2 of patient 4 (step 132), and a weighted value for the difference between the current THI and the baseline THI of patient 4 (step 134).

[0143] In some examples, the weight assigned by processing circuitry 50 to the difference may be based on factors such as the medical history of patient 4. Figure 1 As discussed, the processing circuit system 50 of the IMD 10 can assign such weights based on events in the medical history of the patient 4, such as hospitalization for heart failure, medication changes, history of systolic or diastolic heart failure, hypertension, respiratory disease (e.g., COPD), diabetes, atrial fibrillation, renal failure, one or more blood diseases (e.g., anemia), one or more sleep disorders (e.g., sleep apnea), etc. For example, the patient 4 may have a history of anemia, which may indicate that the patient 4 is particularly likely to become anemic in the future. Alternatively, population-based data may indicate that patients with the same or similar baseline values ​​as the patient 4 may be particularly likely to become anemic (or develop insufficient tissue oxygen saturation or pulse oxygen saturation). In this case, the processing circuit system 50 may assign an increased weight to the difference between the current THI and the baseline THI, thereby making the diagnostic score of the patient 4 more sensitive to fluctuations in the THI value of the patient 4. Similarly, the weight assigned to the difference by the processing circuitry may have a negative value, such as if patient 4's medical history or population-based data indicates that patient 4 is unlikely to become anemic (or develop tissue oxygen desaturation or pulse oxygen desaturation).

[0144] The processing circuit system 50 may then combine weighted values ​​of the differences between the current values ​​and the baseline values ​​to determine a current diagnostic score for patient 4 (step 136), and then compare the current diagnostic score to the baseline diagnostic score (step 138). The baseline diagnostic score may be a diagnostic score previously determined by the processing circuit system 50 based on values ​​of one or more levels of evidence associated with the baseline value for patient 4. For example, the baseline diagnostic score may represent the risk of hospitalization for patient 4 when patient 4 is compensated (such as when patient 4's heart failure state, pulmonary state, and anemia state are stable). The processing circuit 50 may then determine an updated health state for patient 4 based on a comparison of the baseline diagnostic score to the current diagnostic score (step 140). As in Figure 6As in the method of , the processing circuit system 50 can transmit the updated health status to a remote computer, such as the external device 12. The external device 12 or another remote computer can then transmit instructions for medical intervention (e.g., changes in a medication regimen, or instructions to schedule a clinician visit or seek medical assistance) to an interface of a user device located with the patient 4.

[0145] In some cases, this method of determining the health state of patient 4 can advantageously provide context for the current diagnostic score determined for patient 4 by considering the extent to which the current diagnostic score deviates from the baseline diagnostic score. For example, a relatively large difference between the baseline diagnostic score and the current diagnostic score may indicate that the deterioration of one or more aspects of patient 4's condition is more significant than a relatively small difference, even when the previous diagnostic scores remain equal. In examples where the difference between the baseline diagnostic score and the current diagnostic score is relatively large (e.g., meets a threshold), the external device 12 may transmit instructions for more aggressive medical intervention to the user device compared to examples where the difference is smaller. In other examples, patient 4 may be added to a database of patients, particularly those at risk, who may be more closely monitored by a clinician or one or more devices described herein. In any such example, treatment may be further customized to the specific needs of patient 4 based on the extent to which the health state of patient 4 changes over time.

[0146] Fig. 9 is a flow chart illustrating an example technique for external device 12 to determine instructions for a medical intervention based on the health status of patient 4 received from IMD 10 and to transmit the instructions to a user interface. Fig. 9 The method shown may be combined with the methods described herein for determining health status by IMD 10 (such as Figure 6 and Figure 8 In the example shown, external device 12 is configured to receive a health status of patient 4 from IMD 10, which can be transmitted to processing circuitry of external device 12 via communication circuitry 54 and antenna 26 of IMD 10 (step 150).

[0147] In some examples, upon receiving the health status of patient 4 from IMD 10, and before determining instructions for medical intervention for patient 4, external device 12 may transmit one or more queries to the user device. For example, external device 12 may ask patient 4 or a caregiver to answer questions about recent or current activities or symptoms of patient 4, such as whether patient 4 has recently exercised, taken medication, or experienced symptoms. In addition, if IMD 10 has not yet transmitted the current values ​​to external device 12, external device 12 may ask IMD 10 for the current values ​​of StO2, SpO2, and THI of patient 4. Based on the heart failure state, lung state, and anemia state of patient 4, and optionally based on the answers to the queries and / or the current values ​​of patient 4, external device 12 may then determine instructions for medical intervention for patient 4 (step 152).

[0148] The external device 12 can determine instructions for multiple medical interventions for the patient 4. For example, the external device 12 can determine instructions for each of the heart failure state, lung state, and anemia state of the patient 4. For example, based on the heart failure state of the patient 4, the external device 12 can determine instructions for modifying (e.g., starting, stopping, increasing, or decreasing) the dosage of one or more drugs (such as diuretics, nitrates, beta-blockers, ivabradine, or inotropes). In some examples, the instructions for the medical intervention of the patient 4 can take into account the presence of arrhythmias, as indicated by the ECG signal of the patient 4 detected by the IMD 10. For example, the instructions determined by the external device 12 in the presence of arrhythmias can include instructions for the patient 4 to avoid taking certain medications, instructing the patient 4 to go to a medical institution, or can suggest starting CRT or changing CRT parameters. In addition, in some examples, the processing circuit system of the IMD 10 can ignore changes in Z values, StO2 values, HR values, or HRV values ​​that occur during arrhythmias. Based on the pulmonary status of patient 4, external device 12 may determine instructions for modifying the dosage of one or more bronchodilators, steroids, diuretics, or other suitable medications. Based on the anemic status of patient 4, external device 12 may determine instructions for modifying the dosage of one or more medications (such as erythropoiesis-stimulating agents, dietary supplements) or instructions for seeking treatment at a medical facility (e.g., seeking a blood transfusion).

[0149] In some examples, the external device 12 can determine instructions for medical intervention independently of the clinician input, such as by selecting a treatment option associated with the current values ​​of StO2, SpO2 and THI of the patient 4 stored in the memory of the external device 12 or in a central database. In other examples, the clinician can determine instructions for medical intervention on a substantially identical basis and input the instructions to the external device 12. The external device 12 can then transmit the instructions to the interface of the user device with the patient 4 (step 154). In some examples, the external device 12 can transmit a follow-up query to the patient 4 or a caregiver via the user device after transmitting the instructions. These queries may include: questions related to the patient 4's understanding of the transmitted instructions, whether the patient 4 has complied with the instructed medical intervention, and / or whether the patient 4 is experiencing symptoms. The external device 12 can store the patient 4's response in the memory of the external device 12 or in a centralized database. The clinician can view the response and, after any changes to the patient 4's treatment for one or more of heart failure, lung disease or anemia, remotely follow up the patient 4 as needed. In this way, the techniques and systems described herein can advantageously enable patient 4 to receive personalized, frequently updated therapy at a lower cost than a comparable number of clinician visits. Additionally, these techniques and systems can help reduce cardiac remodeling that can result from acute decompensation episodes, which in turn can help minimize the progression of patient 4's heart failure condition.

[0150] Figure 10-12 is a flow chart illustrating an example technique for cross-referencing current values ​​of two or more parameters that may each be associated with cardiac function and pulmonary function of patient 4 . Fig.10 and Fig.11 The output of the illustrated technique indicates whether a change has occurred in the cardiac and / or pulmonary function of the patient 4, and Fig.12 The output of the illustrated technique indicates the type of heart failure condition of patient 4. In some examples, one or more of IMD 10, external device 12, or a clinician may use the patient's 4 health status and one or more current values ​​in conjunction with the patient's 4 health status. Figure 10-12 , to diagnose patient 4 by differentiating heart failure symptoms from lung disease, and to determine instructions for medical intervention for patient 4. However, for clarity, the following description is from the perspective of IMD 10. Figure 10-12 , wherein the processing circuit system 50 may be configured to perform Figure 10-12 Decision shown.

[0151] Fig.10is a flow chart illustrating an example technique for determining whether one or both of the lung function and the heart function of the patient 4 has changed based on a comparison of the current SpO2 value and HR value and / or HRV value of the patient 4 with the corresponding baseline values ​​and thresholds. In some examples, Fig.10 The illustrated techniques may enable a differential diagnosis between cardiac disease and pulmonary disease, such as by identifying one or both of a heart failure condition and a pulmonary disease as the cause of symptoms (e.g., shortness of breath) experienced by patient 4 that may be associated with one or both of the heart failure condition and the pulmonary disease. As described above, the SpO2 value may be an approximation of the SaO2 associated with pulmonary function. However, the SaO2 value may be affected by the congestion state of patient 4. For example, an increase in congestion may be caused by progression of heart failure, but may result in a decrease in the SaO2 value (and therefore a decrease in the SpO2 value). Therefore, it may be desirable to distinguish between the effects of pulmonary function on the SpO2 value and the effects of cardiac function on the SpO2 value, such as by cross-referencing the current SpO2 value of patient 4 with the current HR value and HRV value of patient 4. The HR value and the HRV value may be more closely associated with cardiac function than with pulmonary function. Therefore, by cross-referencing the SpO2 value with the HR value and / or the HRV value, the processing circuit system 50 of the IMD 10 may assess both the cardiac function and the pulmonary function of the patient 4, thereby providing a diagnostic guide for the patient 4. Figure 6 The determined heart failure state and lung state of patient 4 shown in provide added confidence. In addition, HR and / or HRV can provide additional information related to the cardiac function of patient 4, which the processing circuit system 50 of IMD 10 can use in the technique for determining the heart failure state of patient 4.

[0152] exist Fig.10 At the top of the flowchart of , the processing circuit system 50 of the IMD 10 determines the current SpO2 value of the patient 4 (step 160). Next, the processing circuit system 50 compares the current SpO2 value of the patient 4 with the corresponding baseline value, and determines whether the change in the current SpO2 value relative to the baseline value meets the threshold value (step 162). Regardless of whether the processing circuit system 50 determines that the change in the current SpO2 value relative to the baseline value meets the threshold value, the processing circuit system 50 determines the current HR value and HRV value of the patient 4 based on the ECG signal of the patient 4 (step 164, step 166). The processing circuit system 50 of the IMD 10 then compares the current values ​​of HR and HRV with the corresponding baseline values, and determines whether the difference between one or both of the current values ​​of HR and HRV and the baseline value meets the corresponding threshold value (step 168, step 170).

[0153] If the processing circuit system 50 determines that the difference between the current value of SpO2 and the corresponding baseline value meets the threshold, and the difference between one or both of the current values ​​of HR and HRV and the baseline value meets the corresponding threshold, the processing circuit system determines that both the cardiac function and the pulmonary function of the patient 4 have changed (step 172). In some such examples, the processing circuit system 50 may also determine the relative contribution of the heart failure condition and the pulmonary disease in causing the symptoms experienced by the patient 4. For example, if the change in pulmonary function is substantially greater than the change in cardiac function, the processing circuit system 50 may determine that the pulmonary disease is the primary cause of the symptoms, and / or may determine the relative contribution of the heart failure condition and the pulmonary disease in causing the symptoms. If the processing circuit system 50 determines that the difference between the current value of SpO2 and the corresponding baseline value meets the threshold, but the difference between the current value of HR and HRV and the corresponding baseline value does not meet the corresponding threshold, the processing circuit system determines that the pulmonary function of the patient 4 has changed (step 174). If processing circuit system 50 determines that the difference between the current value of SpO2 and the corresponding baseline value does not meet the threshold, but the difference between one or both of the current values ​​of HR and HRV and the corresponding baseline value does meet the corresponding threshold, then processing circuit system determines that the cardiac function of patient 4 has changed (step 176). If processing circuit system 50 determines that the difference between both the current value of SpO2 and the corresponding baseline value does not meet the threshold, and one or both of the differences between the current value of HR and HRV and the baseline value does not meet the corresponding threshold, then processing circuit system determines that both the cardiac function and the pulmonary function of patient 4 have not changed (step 178). Processing circuit system 50 then transmits an indication of the change or stability of the cardiac function and pulmonary function of patient 4 to external device 12 (step 180), which may include information transmitted in determining the health status of patient 4 and / or in determining medical intervention for patient 4 based on considerations similar to those described above. In some such examples, the health status of patient 4 may include a diagnostic indication, such as an indication that patient 4 suffers from one or both of a heart failure condition and a lung disease, an indication that such condition(s) have progressed, or an indication that the symptoms experienced by patient 4 are caused by one or both of the heart failure condition and / or the lung disease. In examples where both the heart and lung functions of patient 4 have changed, the health status may also include an indication of the relative contributions of the heart failure condition and the lung disease in causing the symptoms. In other examples, a clinician may make a differentiated diagnosis related to the heart and lung diseases of patient 4 based on the health status of patient 4.

[0154] Fig.11 is a flow chart illustrating another example technique for determining whether one or both of the lung function and the heart function of the patient 4 has changed based on a comparison of the current StO2 value and the Z value of the patient 4 with the corresponding baseline value and the threshold value. In some examples, Fig.11 The illustrated techniques may enable a differential diagnosis between cardiac disease and pulmonary disease, such as by identifying one or both of a heart failure condition and a pulmonary disease as the cause of a symptom (e.g., shortness of breath) experienced by patient 4 that may be associated with one or both of the heart failure condition and the pulmonary disease. As described above, the StO2 value indicates both SvO2 and SaO2, and SaO2 may be associated with both cardiac function and pulmonary function. However, the Z value may be more closely associated with cardiac function than with pulmonary function. Therefore, by cross-referencing the current StO2 value with the current Z value, the processing circuit system 50 of the IMD 10 may assess both cardiac function and pulmonary function of the patient 4, thereby providing a differential diagnosis between the heart failure condition and the pulmonary disease. Figure 6 The determined heart failure state and lung state of patient 4 shown in provide added confidence. In addition, the current Z value can provide additional information about the cardiac function of patient 4, which the processing circuit system 50 of IMD 10 can use in the technique for determining the heart failure state of patient 4.

[0155] exist Fig.11 At the top of the flowchart of , the processing circuit system 50 of the IMD 10 determines the current StO2 value of the patient 4 (step 190). Next, the processing circuit system 50 compares the current StO2 value of the patient 4 with the corresponding baseline value and determines whether the change in the current StO2 value relative to the baseline value meets the threshold (step 192). Regardless of whether the processing circuit system 50 determines that the change in the current StO2 value relative to the baseline value meets the threshold, the processing circuit system 50 determines the current Z value of the patient 4 based on the signals received from the two or more electrodes 38A-38D (steps 194, 196). The processing circuit system 50 of the IMD 10 then compares the current Z value with the corresponding baseline value and determines whether the difference between the current Z value and the baseline value meets the corresponding threshold (steps 198, 200).

[0156] If the processing circuit system 50 determines that the difference between the current StO2 value and the corresponding baseline value meets the threshold and the difference between the current Z value and the corresponding baseline value meets the threshold, the processing circuit system determines that both the cardiac function and the pulmonary function of the patient 4 have changed (step 202). In some such examples, the processing circuit system 50 may also determine the relative contribution of the heart failure condition and the pulmonary disease in causing the symptoms experienced by the patient 4. For example, if the change in pulmonary function is substantially greater than the change in cardiac function, the processing circuit system 50 may determine that the pulmonary disease is the main cause of the symptoms, and / or may determine the relative contribution of the heart failure condition and the pulmonary disease in causing the symptoms. If the processing circuit system 50 determines that the difference between the current StO2 value and the corresponding baseline value meets the threshold, but the difference between the current Z value and the corresponding baseline value does not meet the threshold, the processing circuit system determines that the pulmonary function of the patient 4 has changed (step 204). If the processing circuit system 50 determines that the difference between the current StO2 value and the corresponding baseline value does not meet the threshold, but the difference between the current Z value and the corresponding baseline value meets the threshold, the processing circuit system determines that the cardiac function of the patient 4 has changed (step 206). If the processing circuit system 50 determines that the difference between the current StO2 value and the corresponding baseline value does not meet the threshold and the difference between the current Z value and the corresponding baseline value does not meet the threshold, the processing circuit system determines that both the cardiac function and the pulmonary function of the patient 4 have not changed (step 208). The processing circuit system 50 then transmits an indication of the change or stability of the cardiac function and the pulmonary function of the patient 4 to the external device 12 (step 210), which may include information transmitted when determining the health state of the patient 4 and / or determining medical intervention for the patient 4 based on considerations similar to those described above. In some such examples, the health state of the patient 4 may include a diagnostic indication, such as an indication that the patient 4 suffers from one or both of a heart failure condition and a lung disease, an indication that such condition(s) have progressed, or an indication that the symptoms experienced by the patient 4 are caused by one or both of the heart failure condition and / or the lung disease. In an example where both the cardiac function and the lung function of the patient 4 have changed, the health state may also include an indication of the relative contribution of the heart failure condition and the lung disease in causing the symptom. In other examples, the clinician may make a differentiated diagnosis related to patient 4's heart disease and lung disease based on patient 4's health status.

[0157] Fig.12 4 is a flow chart illustrating a technique for determining the type of heart failure condition of patient 4 by distinguishing the type of heart failure condition based on a comparison of the current StO2 value and Z value of patient 4 with the corresponding baseline value and threshold. In some examples, when processing circuit system 50 has determined that the anemia state of patient 4 indicates that patient 4 is anemic, a Fig.12 However, Fig.12 The techniques shown can be performed in other situations, such as when Fig.10 or Fig.11 When one of the techniques in indicates that the cardiac function of patient 4 has changed. In some examples, the heart failure condition can be classified based on the tissue perfusion state and congestion state of patient 4. Determining the type of heart failure condition of patient 4 can enable external device 12 to determine appropriate medical intervention for patient 4, and can indicate that the heart failure condition of patient 4 has progressed from one type to another. In some examples, processing circuit system 50 can send a Fig.12 The different types of heart failure conditions shown are assigned different values, such that the diagnostic score for patient 4 may be based in part on which type of heart failure condition patient 4 may have.

[0158] exist Fig.12 At the top of the flowchart of , the processing circuit system 50 of the IMD 10 determines that the difference between the current THI value of the patient 4 and the corresponding baseline value meets the corresponding threshold value (step 220). Next, the processing circuit system 50 determines the current StO2 value of the patient 4, and determines whether the current StO2 value meets the threshold value (step 222). If the processing circuit system 50 determines that the current StO2 value does not meet the threshold value, the processing circuit system 50 determines that the patient 4 has "cold" heart failure, which indicates that the patient 4 has insufficient tissue perfusion (step 224). If the processing circuit system 50 determines that the current StO2 value meets the threshold value, the processing circuit system 50 determines that the patient 4 has "warm" heart failure, which indicates that the patient 4 has sufficient tissue perfusion (226). Regardless of whether the patient 4 has "cold" heart failure or "warm" heart failure, the processing circuit system 50 determines the current Z value of the patient 4 (steps 228, step 230). The processing circuit system 50 of the IMD 10 then determines whether the current Z value meets the threshold value (steps 228, step 230).

[0159] In the event that the processing circuit system 50 determines that the patient 4 has "cold" heart failure and the current Z value is less than the threshold, the processing circuit system determines that the patient 4 has "cold and wet" heart failure (step 232), where the "wet" designation indicates that the patient is congested. In the event that the processing circuit system 50 determines that the patient 4 has "cold" heart failure and the current Z value is not less than the threshold, the processing circuit system determines that the patient 4 has "cold and dry" heart failure (234), where the "dry" designation indicates that the patient is not congested. In the event that the processing circuit system 50 determines that the patient 4 has "warm" heart failure and the current Z value is not less than the threshold, the processing circuit system determines that the patient 4 suffers from "warm and dry" heart failure (step 236). In the event that the processing circuit system 50 determines that the patient 4 has "warm" heart failure and the current Z value is less than the threshold, the processing circuit system determines that the patient 4 suffers from "warm and wet" heart failure (step 238). The processing circuit system 50 then transmits an indication of the change or stability of the cardiac function and pulmonary function of the patient 4 to the external device 12 (step 240), which indication may include information transmitted when determining the health state of the patient 4 and / or when determining a medical intervention for the patient 4. In some such examples, the health state of the patient 4 may include a diagnostic indication, such as an indication that the patient 4 has a specific current type of heart failure condition and / or an indication that the heart failure condition of the patient 4 has progressed from a previous type to a current type. In other examples, the clinician can make a differential diagnosis related to the current type and / or progression of the heart failure condition of the patient 4 based on the health state of the patient 4.

[0160] In some examples, some of the medical interventions that the external device 12 can recommend based on one state of the patient 4 can be affected by another state of the patient 4. For example, some medical interventions for a heart failure condition can be affected by the lung state of the patient 4. Therefore, when determining which medical interventions to order for the patient 4, the external device 12 can consider all three of the heart state, lung state, and anemia state of the patient 4. In this way, the methods and systems described herein can provide reliable treatment for one or more of heart failure conditions, lung disease, and / or anemia by considering multiple parameters of the patient's 4 heart function, lung function, and blood function.

[0161] Although processing circuitry 50 of IMD 10 and processing circuitry of external device 12 are described above as being configured to perform Figure 6-1210, but any step of the techniques described herein may be performed by the processing circuit system of another of the IMD 10 or the external device 12, or by one or more other devices. For example, the processing circuit system of the external device 12 or any other suitable implantable or external device or server may be configured to perform one or more of the steps described as being performed by the processing circuit system 50 of the IMD 10. In other examples, the processing circuit system 50 of the IMD 10 or any other suitable implantable or external device or server may be configured to perform one or more of the steps described as being performed by the processing circuit system of the external device 12. Such other implantable devices or external devices may include, for example, an implantable pacemaker or ICD, an external monitoring device, or any other suitable device. In addition, although the optical sensor and electrodes are described herein as being positioned on the housing of the IMD 10, in other examples, such optical sensors and / or electrodes may be positioned on the housing of another device (such as a transvenous, subcutaneous, or extravascular pacemaker or ICD) implanted in or outside the patient 4, or coupled to such a device via one or more leads.

[0162] Various aspects of the technology may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combination of such components implemented in a programmer (such as a physician or patient programmer, electrical stimulator, or other device). The term "processor" or "processing circuitry" may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry or any other equivalent circuitry.

[0163] In one or more examples, the functions described in the present disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, these functions may be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium forming a tangible non-transient medium. Instructions may be executed by one or more processors (such as, one or more DSPs, ASICs, FPGAs, general-purpose microprocessors, or other equivalent integrated or discrete logic circuit systems). Therefore, the term "processor" or "processing circuit" as used herein may refer to any one or more of the aforementioned structures or any other structures suitable for implementing the technology described herein.

[0164] In addition, in some aspects, the functions described herein may be provided in dedicated hardware and / or software modules. Depicting different features as modules or units is intended to emphasize different functional aspects, and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. Instead, the functions associated with one or more modules or units may be performed by separate hardware or software components, or may be integrated in common or separate hardware or software components. In addition, these techniques may be fully implemented in one or more circuits or logic elements. The technology of the present disclosure may be implemented in a variety of broad equipment or devices, including an IMD, an external programmer, a combination of an IMD and an external programmer, an integrated circuit (IC) or a group of ICs and / or discrete circuit systems residing in the IMD and / or in the external programmer.

[0165] Various aspects of the disclosure have been described. These and other aspects are within the scope of the following claims.

Claims

1. A system for determining a health status of a patient using an implantable medical device, wherein the implantable medical device is configured to be implanted subcutaneously in the chest cavity of the patient, the system comprising: The implantable medical device comprises at least one optical sensor; as well as processing circuitry configured to: determining a current tissue oxygen saturation value of the patient based on a first signal received from the at least one optical sensor; determining a current pulse oximetry value of the patient based on a second signal received from the at least one optical sensor; comparing the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​of a baseline tissue oxygen saturation value and a baseline pulse oxygen saturation value; determining a heart failure status of the patient based at least on a comparison of the current tissue oxygen saturation value and the baseline tissue oxygen saturation value; determining a pulmonary status of the patient based at least on a comparison of the current pulse oxygen saturation value of the patient with the baseline pulse oxygen saturation value; and determining the health status of the patient based on a combination of the heart failure status and the lung status of the patient, Wherein, in order to determine the heart failure state of the patient and determine the pulmonary state of the patient, the processing circuit system is further configured to perform at least one of the following operations: Based on determining whether the change in the current pulse oxygen saturation value relative to the baseline pulse oxygen saturation value meets a threshold, and comparing the current heart rate value with the baseline heart rate value and comparing the current heart rate variability value with the baseline heart rate variability value, determining whether the patient's lung function has changed and whether the patient's heart function has changed, and correspondingly generating an indication of the change or stability of the patient's lung and heart function; as well as Based on the determination of whether the change of the current tissue oxygen saturation value relative to the baseline tissue oxygen saturation value meets the threshold, and comparing the current tissue impedance value with the baseline tissue impedance value, it is determined whether the patient's lung function has changed and whether the patient's cardiac function has changed, and an indication of the change or stability of the patient's lung and cardiac function is generated accordingly.

2. The system according to claim 1, characterized in that The processing circuitry is configured to compare the current tissue oxygen saturation value and the current pulse oxygen saturation value with corresponding values ​​of the baseline tissue oxygen saturation value and the baseline pulse oxygen saturation value by at least: determining whether a difference between the current tissue oxygen saturation value and the baseline tissue oxygen saturation value satisfies a tissue oxygen saturation threshold value associated with a change in cardiac function of the patient; as well as A determination is made as to whether a difference between the current pulse oximetry value and the baseline pulse oximetry value satisfies a pulse oximetry threshold value associated with a change in lung function of the patient.

3. The system according to any one of claims 1 to 2, characterized in that: The medical device further comprises a plurality of electrodes, and wherein the processing circuitry is configured to determine the heart failure state of the patient and the pulmonary state of the patient by at least: determining a current tissue impedance value of the patient based on subcutaneous tissue impedance signals received from at least two electrodes of the plurality of electrodes; comparing the current tissue impedance value to a baseline tissue impedance value; and The patient's hyperemia state is determined by determining whether a difference between the current tissue impedance value and the baseline tissue impedance value satisfies a tissue impedance threshold.

4. The system according to claim 3, characterized in that The processing circuitry is further configured to: determining a current tissue hemoglobin index value of the patient based on a third signal received from the at least one optical sensor; comparing the current tissue hemoglobin index value to the baseline tissue hemoglobin index value by at least determining whether a difference between the current tissue hemoglobin index value and the baseline tissue hemoglobin index value satisfies a tissue hemoglobin index threshold value associated with a change in red blood cell count of the patient; as well as determining an anemic state of the patient based at least on a comparison of the current tissue hemoglobin index value with the baseline tissue hemoglobin index value, Wherein the processing circuit system is configured to determine the health status of the patient at least by determining the health status of the patient based on the anemia status of the patient.

5. The system according to claim 4, characterized in that The anemic state of the patient includes an indication that the patient is anemic, and wherein the processing circuitry is further configured to: determining whether a difference between the current tissue oxygen saturation value and the baseline tissue oxygen saturation value satisfies a tissue oxygen saturation threshold value associated with a change in cardiac function of the patient; and Based on the difference between the current tissue oxygen saturation value and the baseline tissue oxygen saturation value and the congestive state of the patient, a type of heart failure condition of the patient is determined.

6. The system according to any one of claims 1 to 2, characterized in that: The medical device further comprises a plurality of electrodes, and wherein the processing circuitry is configured to determine the heart failure state of the patient and the pulmonary state of the patient by at least: determining a current heart rate and a current heart rate variability value of the patient based on electrocardiogram signals received from at least two electrodes of the plurality of electrodes; comparing the current heart rate and the current heart rate variability value to corresponding ones of a baseline heart rate and a baseline heart rate variability value; and Determine whether at least one of the difference between the current heart rate and the baseline heart rate or the difference between the current heart rate variability value and the baseline heart rate variability value satisfies a corresponding at least one of a heart rate threshold or a heart rate variability threshold associated with a change in cardiac function of the patient.

7. The system according to any one of claims 1 to 2, characterized in that: further comprising an implantable pressure sensing device configured for implantation in a pulmonary artery of the patient and configured to determine a current pulmonary artery pressure value of the patient and transmit the pulmonary artery pressure to the implantable medical device, wherein the processing circuit system is further configured to: comparing the current pulmonary artery pressure to a baseline pulmonary artery pressure; and The heart failure state of the patient is determined based on a comparison of the current pulmonary artery pressure value and the baseline pulmonary artery pressure value.

8. The system according to any one of claims 1 to 2, characterized in that: The processing circuitry is further configured to: transmitting the health status of the patient to a remote computer; receiving from the remote computer instructions for a medical intervention based on the health status of the patient; and The instructions for the medical intervention are transmitted to a user interface.

9. The system according to claim 8, characterized in that The instructions for the medical intervention include at least one of a change in medication selection, a change in medication dosage, an instruction to schedule a visit with a clinician, or an instruction for the patient to seek medical attention.

10. The system according to any one of claims 1 to 2, characterized in that: The processing circuit system is configured to determine the health state of the patient based on a combination of the heart failure state and the lung state by determining a diagnostic score based at least on a combination of the heart failure state and the lung state, wherein the diagnostic score is associated with a likelihood that the patient will experience an adverse medical event.

11. The system according to any one of claims 1 to 2, characterized in that: The processing circuit system is configured to determine the health state of the patient based on a combination of the patient's heart failure state and the pulmonary state by at least determining whether a cause of a symptom experienced by the patient is associated with the patient's heart failure state or the pulmonary state.

12. The system according to any one of claims 1 to 2, characterized in that: The processing circuitry is configured to: determine the heart failure state of the patient by determining a heart failure score based at least on a comparison of the current tissue oxygen saturation value and the baseline tissue oxygen saturation value; and determining the pulmonary state of the patient by determining a lung fraction based at least on a comparison of the current pulse oximetry value of the patient with the baseline pulse oximetry value, and wherein the processing circuitry is further configured to: comparing the heart failure score to the lung score; and A determination is made based on the comparison whether a cause of symptoms experienced by the patient is associated with the patient's heart failure score or the lung score.

13. The system of claim 12, wherein: The heart failure score comprises a likelihood that the symptoms experienced by the patient are at least partially caused by a heart failure condition, and the lung score comprises a likelihood that the symptoms experienced by the patient are at least partially caused by a lung disease.

14. The system according to any one of claims 1 to 2, characterized in that: The implantable medical device includes a housing configured for subcutaneous implantation within the chest cavity, and wherein the at least one optical sensor is positioned on the housing.

15. The system according to any one of claims 1 to 2, characterized in that: The implantable medical device includes the processing circuitry.

16. The system according to any one of claims 1 to 2, characterized in that: The implantable medical device includes a leadless implantable medical device.

17. A non-volatile computer-readable medium storing instructions for causing a processing circuit system to perform operations defined in any one of claims 1-16 for determining a health status of a patient using an implantable medical device constructed to be implanted subcutaneously outside the patient's chest cavity.

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