System and method for diverting flow to facilitate measurement of system parameters

Abstract

A method facilitating the measurement of hemodynamic parameters by injection of an indicator in an indicator dilution technique using an extracorporeal circuit connected to a patient, includes reducing a pressure spike associated with the introduction of the indicator into the extracorporeal circuit. The method diverts blood flow during an indicator introduction and then returns the diverted blood back into the extracorporeal circuit after the introduction is completed.

1 . A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:
 (a) introducing, at a first site in an extracorporeal circuit, an indicator into the extracorporeal circuit, the extracorporeal circuit extending between an arterial connection with a patient and a venous connection with the patient;   (b) diverting, at a second site in the extracorporeal circuit, blood flow from the extracorporeal circuit;   (c) accumulating the diverted blood flow;   (d) ending introduction of the indictor;   (e) ending diverting blood flow from the extracorporeal circuit;   (f) returning the diverted blood flow into the extracorporeal circuit;   (g) measuring a change caused by introducing the indictor into the extracorporeal circuit; and   (h) calculating a hemodynamic parameter from the measured change.   
     
     
         2 . The method of  claim 1 , wherein the steps of introducing an indicator into the extracorporeal circuit and diverting blood flow from the extracorporeal circuit are concurrent. 
     
     
         3 . The method of  claim 1 , wherein the step of introducing an indicator into the extracorporeal circuit starts before the step of diverting blood flow from the extracorporeal circuit. 
     
     
         4 . The method of  claim 1 , wherein the step of diverting blood flow from the extracorporeal circuit starts before the step of introducing an indicator into the extracorporeal circuit. 
     
     
         5 . The method of  claim 1 , wherein the calculated hemodynamic parameter is one of cardiac output, central blood volume and lung water. 
     
     
         6 . The method of  claim 1 , wherein the second site is upstream of the first site. 
     
     
         7 . The method of  claim 6 , further comprising, after ending diverting blood flow from the extracorporeal circuit, the step of returning diverted blood flow back into the extracorporeal circuit at the second site. 
     
     
         8 . The method of  claim 1 , wherein the step of diverting blood flow includes redirecting at least a portion of the blood flow from the second site into a second conduit bypassing the first site. 
     
     
         9 . The method of  claim 8 , wherein the step of redirecting at least a portion of the blood flow includes one of (i) redirecting the blood flow to the venous connection and (ii) redirecting the blood flow to a third site in the extracorporeal circuit downstream of the first site. 
     
     
         10 . The method of  claim 1 , further comprising establishing a regulated blood flow in an extracorporeal circuit between the arterial connection and the venous connection. 
     
     
         11 . The method of  claim 10 , wherein the step of establishing a regulated blood flow comprises starting a pump attached to the extracorporeal circuit. 
     
     
         12 . The method of  claim 1 , wherein the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood flow from the extracorporeal circuit and releasing the diverted blood to the extracorporeal circuit are accomplished by using a pressure responsive side fluid line connected to the extracorporeal circuit upstream of the first site, the side fluid line accepts diverted blood flow from the extracorporeal circuit during the introducing step and releases diverted blood flow to the extracorporeal circuit when the introducing step ends. 
     
     
         13 . The method of  claim 1 , wherein the steps of diverting blood flow from the extracorporeal circuit, ending diverting of blood flow from the extracorporeal circuit and returning the diverted blood to the extracorporeal circuit are accomplished by using a pressure activated expansion reservoir. 
     
     
         14 . A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:
 (a) diverting, at a diverting site, a flow of blood from an extracorporeal circuit fluidly connecting an arterial connection with a patient and a venous connection with the patient during introduction of an indicator into the extracorporeal circuit at an indicator introduction site located downstream of the diverting site; and   (b) returning the diverted blood into the extracorporeal circuit after the introduction of the indicator has stopped.   
     
     
         15 . The method of  claim 14 , wherein the steps of diverting the flow of blood and returning the diverted blood includes providing the diverting site upstream of the indicator introduction site and a third site for returning the diverted blood downstream from the indicator introduction site. 
     
     
         16 . The method of  claim 14 , wherein the steps of diverting a flow of blood and returning the diverted blood includes diverting the blood flow into a fluid volume accumulating reservoir connected to the extracorporeal circuit upstream from the indicator introduction site during the introduction and returning the blood from the reservoir into the extracorporeal circuit after the introduction of the indicator ceases. 
     
     
         17 . The method of  claim 14 , further comprising the step of blocking flow in the extracorporeal circuit between the indicator introduction site and the diverting site during the introduction of the indicator. 
     
     
         18 . A method of managing blood flow in an extracorporeal circuit, the method comprising the steps of:
 (a) introducing an indicator into an extracorporeal circuit fluidly connecting an arterial connection with a patient and a venous connection with the patient; and   (b) reducing a pressure spike in the extracorporeal circuit associated with introducing the indicator into the extracorporeal circuit.   
     
     
         19 . The method of  claim 18 , wherein reducing the pressure spike includes diverting a flow of blood from the extracorporeal circuit during introduction of the indicator and returning the diverted blood into the extracorporeal circuit after the introduction of the indicator has stopped.