Techniques for mitigating motion artifacts from implantable physiological sensors

Abstract

Disclosed techniques include monitoring a physiological characteristic of a patient with a sensor that is mounted to an inner wall of a thoracic cavity of the patient, and sending a signal based on the monitored physiological characteristic from the sensor to a remote device.

What is claimed is: 
     
         1 . A method comprising:
 monitoring a physiological characteristic of a patient with a sensor that is mounted to an inner wall of a thoracic cavity of the patient; and   sending a signal based on the monitored physiological characteristic from the sensor to a remote device.   
     
     
         2 . The method of  claim 1 , wherein the remote device is an implantable medical device implanted within the patient. 
     
     
         3 . The method of  claim 1 , wherein the sensor is mounted beneath the xyphoid process of the patient. 
     
     
         4 . The method of  claim 1 , wherein the sensor includes a sound sensing element that monitors the heart sounds of the patient. 
     
     
         5 . The method of  claim 1 , wherein the sensor includes an electrical sensing element that senses an ECG of the heart of the patient. 
     
     
         6 . The method of  claim 1 , wherein the sensor includes an electrical sensing element that senses an impedance of tissue and/or fluid of the patient. 
     
     
         7 . The method of  claim 1 , wherein the sensor includes an electrical sensing element that senses an impedance of a cardiac tissue and/or blood of the patient. 
     
     
         8 . The method of  claim 1 , wherein the sensor includes an optical sensing element for monitoring blood flow in a vasculature of the patient. 
     
     
         9 . The method of  claim 1 , wherein the sensor includes an optical sensing element for monitoring blood oxygenation in a vasculature of the patient. 
     
     
         10 . The method of  claim 1 , wherein the sensor includes two or more sensing elements selected from a group consisting of
 an accelerometer;   an optical sensing element   an electrical sensing element; and   a sound sensing element.   
     
     
         11 . A method comprising:
 monitoring sounds with a sound sensor that is mounted to an inner wall of a thoracic cavity of a patient; and   sending a sound signal based on the monitored sounds from the sound sensor to a controller of an implantable medical device implanted within the patient.   
     
     
         12 . The method of  claim 10 , wherein the monitored sounds include monitored heart sounds, the method further comprising generating at least one cardiac metric based on the monitored heart sounds. 
     
     
         13 . The method of  claim 11 , further comprising:
 monitoring posture of the patient with a posture sensor; and   analyzing the sound signal in combination with the monitored posture to generate at least one cardiac metric.   
     
     
         14 . The method of  claim 12 , further comprising:
 sensing a cardiac electrogram signal with the implantable medical device; and   analyzing the sound signal in combination with the cardiac electrogram signal to generate the at least one cardiac metric.   
     
     
         15 . The method of  claim 12 , wherein sensing the sound signal with the implantable medical device and analyzing the signal in combination with the monitored posture to generate the at least one cardiac metric includes generating one or more acoustic cardiographic metrics based on the heart sounds and the electrogram. 
     
     
         16 . The method of  claim 10 , wherein the implanted sound sensor is included in an integrated sensor assembly, wherein the integrated sensor assembly further includes at least one of a group consisting of:
 an accelerometer;   an ECG sensor;   an optical sensor;   a posture sensor; and   an impedance sensor.   
     
     
         17 . The method of  claim 10 , wherein the sound sensor is implanted on a patient tissue selected from a group consisting of:
 a sternum of the patient;   a rib cage of the patient; and   a xiphoid process of the patient.   
     
     
         18 . The method of  claim 10 , wherein the monitored sounds include monitored lung sounds, the method further comprising generating a respiration metric based on the monitored lung sounds. 
     
     
         19 . A method for implanting a sound sensor comprising:
 accessing a thoracic cavity of a patient;   controlling air pressure within a thoracic cavity of the patient via a vacuum to mitigate a risk of lung collapse during implantation of the sound sensor;   positioning the sound sensor within the thoracic cavity of the patient; and   securing the sound sensor to an inner wall of the thoracic cavity.   
     
     
         20 . The method of  claim 18 , wherein securing the sound sensor to the inner wall of the thoracic cavity comprises securing the sound sensor using at least one of a group consisting of:
 a suture;   a cement;   a glue; and   vacuum.   
     
     
         21 . The method for implanting of  claim 18 , wherein securing the sound sensor to the inner wall of the thoracic cavity comprises clamping the sound sensor to the inner wall of the thoracic cavity using a clamping tool by compressing the sound sensor and patient tissue forming the inner wall of the thoracic cavity between two levers of the clamping tool. 
     
     
         22 . The method of  claim 18 , further comprising:
 wherein accessing the thoracic cavity of the patient includes cutting tissue of the patient to form an incision adjacent to a target implant location for the sound sensor;   inserting a surgical tool into the incision to spread the cut tissue to provide access to the target implant location by creating an access space sufficiently wide to receive the sound sensor;   positioning the sound sensor proximate to the target implant location within the thoracic cavity via the access space;   securing the sound sensor to the target implant location within the thoracic cavity, wherein the target implant location is proximate at least one of a sternum, a rib cage, or a xiphoid process of the patient by at least one of a clamp, a cement, a glue, or a suture;   checking the sound sensor to verify proper function and operation with an implantable medical device once it is secured to the inner wall of the thoracic cavity;   retracting the surgical tool from the spread cut; and   suturing the cut tissue closed at the incision location.   
     
     
         23 . The method of  claim 21 , wherein the surgical tool comprises a clamping tool comprising:
 a first lever with; and   a second lever pivotally mounted to the first lever,   wherein securing the sound sensor to the inner wall of the thoracic cavity comprises clamping the sound sensor to the inner wall of the thoracic cavity using the clamping tool by compressing the sound sensor and patient tissue forming the inner wall of the thoracic cavity between the first and second levers of the clamping tool such that a distal end of the first lever presses on an exterior side of the patient while a distal end of the second lever presses on the sound sensor within the thoracic cavity.   
     
     
         24 . A system comprising:
 an implantable medical device; and   a sound sensor configured to mount to an inner wall of a thoracic cavity of a patient, wherein the sound sensor is further configured to send a sound signal based on sounds monitored from within the thoracic cavity to the implantable medical device;   wherein the implantable medical device is configured to receive the sound signal from the sound sensor and generate a physiological metric based on the received sound signal.   
     
     
         25 . The system of  claim 23 , wherein generating the physiological metric based on the received sound signal comprises generating a cardiac metric based on the received sound signal. 
     
     
         26 . The system of  claim 24 , wherein the sound sensor is included in an integrated sensor assembly that also includes a cardiac sensor configured to sense an electrocardiogram signal, wherein generating the cardiac metric based on the received sound signal includes generating the cardiac metric based on the received sound signal and the electrocardiogram signal. 
     
     
         27 . The system of  claim 23 , wherein the sound sensor is configured to send the sound signal to the implantable medical device via a telemetry connection. 
     
     
         28 . The system of  claim 23 , wherein the implantable medical device is configured to therapy via a signal generator to at least one of a right atrium, right ventricle or a left ventricle of the heart of the patient. 
     
     
         29 . The system of  claim 23 , wherein generating the physiological metric based on the received sound signal does not include filtering skeletal muscle motion artifacts from the sound signal.