System and methods for wireless body fluid monitoring

Abstract

An adherent device to monitor a tissue hydration of a patient comprises an adhesive patch to adhere to a skin of the patient. At least four electrodes are connected to the patch and capable of electrically coupling to the patient. Impedance circuitry is coupled to the at least four electrodes to measure a tissue resistance of the patient, where the circuitry is configured to determine the tissue hydration in response to tissue resistance. The circuitry may comprise a processor system and the tissue resistance may correspond to a change in patient body fluid. The impedance circuitry is configured to measure the hydration signal using at least one low measurement frequency, which may be in the range of 0 to 10 kHz. Multiple measurement frequencies may be used and the hydration signal may include a tissue reactance measurement.

1 - 39 . (canceled) 
     
     
         40 . An adherent device to monitor a patient, the device comprising:
 an adhesive patch to adhere to a skin of the patient;   at least two electrodes connected to the patch and capable of electrically coupling to the patient; and   circuitry coupled to the at least two electrodes to measure a tissue resistance of the patient at a plurality of frequencies greater than zero, wherein the circuitry is configured to detect a low frequency droop in the tissue resistance and to, when low frequency droop is detected, temporarily suspend data collection or disregard some collected data based at least in part on the fact that the low frequency droop has been detected.   
     
     
         41 . The adherent device of  claim 40 , wherein the circuitry comprises a processor system configured to determine a tissue hydration of the patient in response to the tissue resistance. 
     
     
         42 . The adherent device of  claim 41 , wherein the circuitry is further configured to determine the tissue hydration based on a tissue resistance measured at a single frequency. 
     
     
         43 . The adherent device of  claim 40 , wherein the circuitry is further configured to measure a tissue reactance of the patient. 
     
     
         44 . The adherent device of  claim 40 , wherein the circuitry is configured to measure the tissue resistance using at least one low measurement frequency. 
     
     
         45 . The adherent device of  claim 44 , wherein the at least one low measurement frequency is in the range of 5 to 15 kHz. 
     
     
         46 . The adherent device of  claim 44 , wherein the at least one low measurement frequency comprises multiple measurement frequencies. 
     
     
         47 . The adherent device of  claim 40 , wherein the at least two electrodes comprise two force electrodes and two sense electrodes. 
     
     
         48 . The adherent device of  claim 47 , wherein the circuitry measures tissue impedance, and wherein the circuitry is configured to:
 determine an amount of extracellular edema from the tissue impedance; and   calculate and report a patient risk of an adverse cardiac event based on the amount of extracellular edema.   
     
     
         49 . A method of monitoring a patient, the method comprising:
 adhering an adhesive patch to a skin of the patient to couple at least two electrodes to the skin of the patient to form a skin-electrode interface;   measuring a tissue resistance of the patient at a plurality of frequencies greater than zero with impedance circuitry coupled to the at least two electrodes;   detecting a low frequency droop in the tissue resistance measurement; and   temporarily suspending data collection or disregarding some collected data based at least in part on the fact that the low frequency droop has been detected.   
     
     
         50 . The method of  claim 49 , further comprising determining a hydration of the patient using the tissue resistance measurement. 
     
     
         51 . The method of  claim 50 , wherein the hydration of the patient is determined from a measurement of the tissue resistance at a single low measurement frequency less than 10 kHz. 
     
     
         52 . The method of  claim 49 , further comprising measuring a tissue reactance of the patient. 
     
     
         53 . The method of  claim 52 , further comprising determining a quality of the skin-electrode coupling from the tissue reactance measurement. 
     
     
         54 . The method of  claim 53 , further comprising identifying a poor skin-electrode coupling when the tissue reactance is greater than a threshold of about 10Ω. 
     
     
         55 . The method of  claim 49 , further comprising identifying an irregular skin-electrode coupling when the tissue resistance droop exceeds a threshold of 10% of a nominal value. 
     
     
         56 . The method of  claim 49 , further comprising:
 measuring a tissue reactance of the patient;   determining a hydration signal of the patient with impedance circuitry coupled to the at least two electrodes, wherein the hydration signal comprises the tissue resistance measurement and the tissue reactance measurement;   determining an amount of extracellular edema using the tissue resistance measurement; and   determining a quality of skin-electrode coupling using the tissue reactance measurement and without using the tissue resistance measurement.   
     
     
         57 . The method of  claim 56 , further comprising indicating a replacement status of the adhesive patch based on the quality of the skin-electrode coupling. 
     
     
         58 . An adherent device to monitor a patient, the device comprising:
 an adhesive patch to adhere to a skin of the patient;   at least two electrodes connected to the patch and capable of electrically coupling to the patient to form a skin-electrode interface; and   circuitry coupled to the at least two electrodes to measure an electrocardiogram signal of the patient, wherein the circuitry is configured to measure a characteristic of the electrocardiogram signal and, on the basis of the measured characteristic, determine a quality of the skin-electrode interface.   
     
     
         59 . The adherent device of  claim 58 , wherein the measured characteristic of the electrocardiogram signal includes a noise of the electrocardiogram signal, and wherein the circuitry is configured to determine a quality of the skin-electrode interface based at least in part on the noise of the electrocardiogram signal. 
     
     
         60 . The adherent device of  claim 58 , wherein the measured characteristic of the electrocardiogram signal includes a signal-to-noise ratio of the electrocardiogram signal, and wherein the circuitry is configured to determine a quality of the skin-electrode interface based at least in part on the signal-to-noise ratio of the electrocardiogram signal. 
     
     
         61 . A method of monitoring a patient, the method comprising:
 adhering an adhesive patch to a skin of the patient to couple at least two electrodes to the skin of the patient to form a skin-electrode interface;   measuring an electrocardiogram signal of the patient with electrocardiogram circuitry coupled to the at least two electrodes; and   determining a quality of the skin-electrode interface based on a characteristic of the electrocardiogram signal.   
     
     
         62 . The method of  claim 61 , wherein the characteristic of the electrocardiogram signal includes a noise of the electrocardiogram signal, and wherein determining a quality of the skin-electrode interface based on a characteristic of the electrocardiogram signal comprises determining a quality of the skin-electrode interface based at least in part on the noise of the electrocardiogram signal. 
     
     
         63 . The method of  claim 61 , wherein the characteristic of the electrocardiogram signal includes a signal-to-noise ratio of the electrocardiogram signal, and wherein determining a quality of the skin-electrode interface based on a characteristic of the electrocardiogram signal comprises determining a quality of the skin-electrode interface based at least in part on the signal-to-noise ratio of the electrocardiogram signal.