Portable device for monitoring electrocardiographic signals and indices of blood flow

Abstract

Embodiments of the present invention are directed to a physiological monitoring device which is configured to record signals that reflect blood flow and/or blood pressure, and which may also record ECG signals. In one embodiment, a portable monitoring device comprises a plurality of impedance electrodes configured to be coupled to a patient's body and to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body. At least a portion of the portable monitoring device is configured to be insertable subcutaneously into the patient's body.

1 - 36 . (canceled)  
   
   
       37 . A method of monitoring a patient, the method comprising: 
 coupling a plurality of impedance electrodes to a patient's body to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body which exhibits pulsation of blood corresponding to the local electrical impedance between the impedance electrodes; and    inserting at least a portion of a portable monitoring device including the impedance electrodes subcutaneously into the patient's body.    
   
   
       38 . The method of  claim 37  wherein the impedance electrodes are placed in proximity to a target region of the patient's body to be monitored.  
   
   
       39 . The method of  claim 38  wherein the impedance electrodes are placed within less than about 5 cm of the target region of the patient's body to be monitored.  
   
   
       40 . The method of  claim 37  wherein the impedance electrodes are applied to a muscle of the patient's body to be monitored.  
   
   
       41 . The method of  claim 37  further comprising positioning two of the impedance electrodes near an artery and spacing the impedance electrodes in a direction generally parallel to the artery.  
   
   
       42 . The method of  claim 37  further comprising positioning two of the impedance electrodes near an artery and spacing the impedance electrodes in a direction generally transverse across the artery.  
   
   
       43 . The method of  claim 37  further comprising measuring local tissue temperature of the patient's body.  
   
   
       44 . The method of  claim 43  further comprising monitoring the measured local tissue temperature for an abrupt local temperature change as potential indication of an acute change in local blood flow.  
   
   
       45 . The method of  claim 37  further comprising measuring ECG data of the patient.  
   
   
       46 . The method of  claim 45  further comprising: 
 correlating the measured ECG data of the patient with the measured local electrical impedance of the patient as a surrogate measurement of blood flow.    
   
   
       47 . The method of  claim 37  further comprising transferring information obtained by the impedance electrodes to an external device disposed outside the patient's body.  
   
   
       48 . The method of  claim 37  further comprising generating a warning based on the detected information.  
   
   
       49 . The method of  claim 37  further comprising storing physiological information obtained by detecting the local electrical impedance by the impedance electrodes.  
   
   
       50 . The method of  claim 49  wherein the physiological information is stored based on instructions delineating criteria for data to be stored.  
   
   
       51 . The method of  claim 49  wherein the physiological information is stored proximate to an event based on information detected by the impedance electrodes or patient-activated triggering.  
   
   
       52 . The method of  claim 37  further comprising coupling auxiliary leads to the impedance electrodes and positioning the auxiliary leads in a target location in the patient's body.  
   
   
       53 . The method of  claim 37  wherein the portion of the patient's body encompassed by the electrical field includes at least one of an artery, muscle, or tissue which exhibits pulsation of blood corresponding to the local electrical impedance between the impedance electrodes.  
   
   
       54 . The method of  claim 37  further comprising: 
 monitoring a change in the measured local impedance; and    obtaining a pulsatile blood volume change in the portion of the patient's body encompassed by the electrical field based on the change in the measured local impedance.    
   
   
       55 . The method of  claim 54  wherein the change in the pulsatile blood volume change in the portion of the patient's body encompassed by the electrical field is proportional to the change in the measured local impedance.  
   
   
       56 . A method of monitoring a patient, the method comprising: 
 coupling a plurality of impedance electrodes to a patient's body to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field;    monitoring a change in the measured local impedance; and    obtaining a pulsatile blood volume change in the portion of the patient's body encompassed by the electrical field based on the change in the measured local impedance.    
   
   
       57 . The method of  claim 56  wherein the impedance electrodes are placed within less than about 5 cm of a target region of the patient's body to be monitored.  
   
   
       58 . The method of  claim 57  wherein the impedance electrodes are placed within less than about 5 cm of an artery in the target region.  
   
   
       59 . A method of monitoring a patient, the method comprising: 
 coupling a plurality of impedance electrodes to a patient's body to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body;    measuring ECG data of the patient; and    correlating the measured ECG data of the patient with the measured local electrical impedance of the patient as a surrogate measurement of blood flow.    
   
   
       60 . The method of  claim 59  wherein the impedance electrodes are placed within less than about 5 cm of a target region of the patient's body to be monitored.  
   
   
       61 . The method of  claim 60  wherein the impedance electrodes are placed within less than about 5 cm of an artery in the target region.