Measurement of susceptibility to diabetic foot ulcers

Abstract

The present disclosure provides apparatuses and methods for measuring capacitance as an indication of susceptibility to the formation of a diabetic foot ulcer.

We claim: 
     
         1 . An apparatus for assessing susceptibility of tissue to formation of a diabetic foot ulcer (DFU), said apparatus comprising:
 a plurality of electrodes embedded on a substrate, wherein a pair of said electrodes is capable of forming a capacitive sensor configured to measure a first capacitance of a pre-selected first region of tissue on a first foot proximate to said capacitive sensor, wherein said measured first capacitance corresponds to a level of extracellular fluid (ECF) at said pre-selected first region of tissue on said first foot, and wherein said pre-selected first region of tissue is selected from the group consisting of a calcaneal pad and a metatarsal pad,   a drive circuit electronically coupled to said electrodes,   a processor electronically coupled to said drive circuit, and   a non-transitory computer-readable medium electronically coupled to said processor and comprising instructions stored thereon that, when executed on said processor, perform the steps of: 
 receiving information regarding said measured first capacitance from said drive circuit, 
 comparing said measured first capacitance to a first DFU reference value, wherein said first DFU reference value is a measurement of a second capacitance of a pre-selected second region of tissue on a second foot that is bisymmetric to said pre-selected first region of foot tissue with respect to a centerline of the body, 
 receiving information regarding said first DFU reference value from said drive circuit, 
 determining a difference between said measured first capacitance and said first DFU reference value, and 
 providing a first notification if the difference is greater than a first predetermined threshold. 
   
     
     
         2 . (canceled) 
     
     
         3 . (canceled) 
     
     
         4 . The apparatus of  claim 1 , wherein said first DFU reference value is determined from measurements of said second capacitance at said pre-selected second region of tissue on said second foot at one or more times prior to the most recent measurement of said first capacitance. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . The apparatus of  claim 1 , wherein said pre-selected second region of tissue on said second foot is known to be healthy. 
     
     
         8 . The apparatus of  claim 1 , wherein said second capacitance is measured at approximately the same time as said first capacitance. 
     
     
         9 . The apparatus of  claim 1 , the apparatus further comprising one or more temperature sensors that are configured to measure a first temperature of said pre-selected first region of tissue on said first foot and are coupled to said processor, wherein:
 said instructions further comprise the steps of: 
 receiving information regarding said measured temperature from said one or more temperature sensors, and 
 comparing said measured temperature to a second DFU reference value, and 
 providing a second notification if said measured first capacitance differs from said first DFU reference value by an amount greater than said predetermined first threshold and said measured temperature differs from said second DFU reference value by an amount greater than a predetermined second threshold. 
   
     
     
         10 . The apparatus of  claim 1 , the apparatus further comprising one or more optical sensors configured to image an underside of said first foot or said second foot of a patient while said patient is standing on said substrate. 
     
     
         11 - 30 . (canceled) 
     
     
         31 . The apparatus of  claim 1 , the apparatus further comprising:
 at least two stimulus electrodes disposed on the substrate such that a portion of a current passing between a pair of the stimulus electrodes will pass through a portion of said preselected first region of tissue; and   an external controller electrically connected to said at least two stimulus electrodes and configured to provide a therapeutic stimulus to said preselected first region of tissue.   
     
     
         32 . The integrated apparatus of  claim 31 , wherein said external controller is further configured to control said two electrodes to detect conductive contact with the patient’s skin during a sensing phase and to apply said therapeutic stimulus to the patient during a therapeutic phase.