System and method for active bypass dialysis access disconnection detection

Abstract

A dialysis system comprising: a blood circuit including a blood pump, a dialyzer, and an air removal apparatus; an arterial line of the blood circuit extending from the blood pump to an arterial access needle; a venous line of the blood circuit extending from the air removal apparatus to a venous access needle; arterial and venous conductive connections placed along the arterial and venous lines, respectively; a first electrical potential source configured to apply a first electrical potential between (i) the arterial and venous conductive connections and (ii) the arterial and venous access needles; and a second electrical potential source configured to apply a second electrical potential between (a) the arterial and venous conductive connections and (b) one of the blood pump, dialyzer or air removal device.

The invention is claimed as follows: 
     
         1 . A dialysis system comprising:
 a blood circuit including a blood pump, a dialyzer, and an air removal apparatus;   an arterial line of the blood circuit extending from the blood pump to an arterial access needle;   a venous line of the blood circuit extending from the air removal apparatus to a venous access needle;   arterial and venous conductive connections placed along the arterial and venous lines, respectively;   a first electrical potential source configured to apply a first electrical potential between (i) the arterial and venous conductive connections and (ii) the arterial and venous access needles; and   a second electrical potential source configured to apply a second electrical potential between (a) the arterial and venous conductive connections and (b) one of the blood pump, dialyzer or air removal device.   
     
     
         2 . The dialysis system of  claim 1 , wherein the second electrical potential is applied between the arterial conductive connection and the blood pump. 
     
     
         3 . The dialysis system of  claim 1 , wherein the second electrical potential is applied between the arterial conductive connection and a third conductive connection placed along the blood circuit. 
     
     
         4 . The dialysis system of  claim 3 , wherein the third conductive connection is located along the arterial line between the arterial conductive connection and the blood pump. 
     
     
         5 . The dialysis system of  claim 1 , wherein the second electrical potential is applied between the venous conductive connection and the air removal apparatus. 
     
     
         6 . The dialysis system of  claim 1 , wherein the second electrical potential is applied between the venous conductive connection and a third conductive connection placed along the blood circuit. 
     
     
         7 . The dialysis system of  claim 6 , wherein the third conductive connection is located along the venous line between the venous conductive connection and the air removal apparatus. 
     
     
         8 . The dialysis system of  claim 1 , which is configured such that the second electrical potential at least substantially matches the first electrical potential. 
     
     
         9 . The dialysis system of  claim 1 , which includes electronics configured to measure the first electrical potential and a controller programmed to at least substantially match the second electrical potential to the measured first electrical potential. 
     
     
         10 . The dialysis system of  claim 1 , which includes a controller configured to determine a needle disconnection upon a threshold change in a signal produced by the first electrical potential. 
     
     
         11 . The dialysis system of  claim 1 , wherein the second electrical potential causes a signal produced by the first electrical potential to bypass at least one of the blood pump, dialyzer or air removal apparatus. 
     
     
         12 . A dialysis system comprising:
 a blood circuit including a dialyzer, a blood pump, an arterial line and a venous line;   arterial and venous conductive connections placed along the arterial and venous lines between the dialyzer/blood pump and the distal ends of the arterial and venous lines, respectively;   a first electrical potential source configured to apply a first electrical potential between (i) the arterial and venous conductive connections and (ii) the distal ends of the arterial and venous lines; and   a second electrical potential source configured to apply a second electrical potential between (a) the dialyzer/blood pump and (b) the arterial and venous conductive connections.   
     
     
         13 . The dialysis system of  claim 12 , wherein the second electrical potential at least substantially matches the first electrical potential, causing a signal produced by the first electrical potential to bypass at least one of the dialyzer or the blood pump. 
     
     
         14 . The dialysis system of  claim 12 , which includes a controller programmed to determine a needle access disconnection upon a sufficient change in a sensed signal produced by the first electrical potential. 
     
     
         15 . An access disconnection method for a machine employing a blood circuit, the blood circuit having a machine segment and a patient access segment, the method comprising:
 injecting an electrical signal into the blood circuit between the machine segment and the patient access segment;   attempting to cause the electrical signal to flow through only the patient access segment and to bypass the machine segment; and   measuring the signal in the patient access segment and determining that an access disconnection event has occurred upon a threshold change in the measured signal.   
     
     
         16 . The access disconnection method of  claim 15 , wherein attempting to cause the electrical signal to bypass the machine segment includes applying a potential to the blood circuit at a location between the signal in the patient access segment and a machine operating component of the machine segment of the blood circuit. 
     
     
         17 . The access disconnection method of  claim 16 , wherein applying the potential includes applying a potential that is at least substantially equal to a potential applied to cause the signal. 
     
     
         18 . The access disconnection method of  claim 15 , the signal applied via first and second conductive connections to the blood circuit, and wherein attempting to cause the electrical signal to bypass the machine segment includes applying a potential to the blood circuit at a location between one of the first and second conductive connections and a machine operating component of the machine segment of the blood circuit. 
     
     
         19 . The access disconnection method of  claim 18 , which includes applying the potential to one of the first and second conductive connections and a third conductive connection located between the one of the first and second connections and the machine operating component. 
     
     
         20 . The access disconnection method of  claim 15 , wherein attempting to cause the electrical signal to bypass the machine segment includes, in addition to the signal, applying a potential to the blood circuit downstream of the blood pump. 
     
     
         21 . The access disconnection method of  claim 15 , which includes taking into account an impedance associated with the vascular access in determining the threshold change in the measured signal by which the access disconnection is determined.