A system comprising: an extracorporeal circuit comprising: a flow port for returning blood from the extracorporeal circuit to a vasculature at a region of a body; and an injector member comprising a distal tip; a controlled flow partitioning system comprising: a first pressure sensor disposed proximate to the distal tip of the at least one injector member; a second pressure sensor disposed at an outer surface of the at least one injector member, at a predetermined separation proximal from the distal tip; an injection flow rate source coupled to the injection member to control the flow rate of fluid from the distal tip to a predetermined flow rate pattern; and a console (802, 905) comprising at least one processing unit programmed to: receive data indicative of measurements of pressure using the first pressure sensor and the second pressure sensor over a time interval T with the flow of blood injected at the distal tip at the predetermined flow rate pattern; and compute at least one of a proximal exterior conductance or a distal exterior conductance at the distal tip of the at least one injector member using data indicative of the measurements of pressure and the predetermined flow rate pattern. an extracorporeal circuit comprising: a flow port for returning blood from the extracorporeal circuit to a vasculature at a region of a body; and an injector member comprising a distal tip; a flow port for returning blood from the extracorporeal circuit to a vasculature at a region of a body; and an injector member comprising a distal tip; a controlled flow partitioning system comprising: a first pressure sensor disposed proximate to the distal tip of the at least one injector member; a second pressure sensor disposed at an outer surface of the at least one injector member, at a predetermined separation proximal from the distal tip; an injection flow rate source coupled to the injection member to control the flow rate of fluid from the distal tip to a predetermined flow rate pattern; and a console (802, 905) comprising at least one processing unit programmed to: receive data indicative of measurements of pressure using the first pressure sensor and the second pressure sensor over a time interval T with the flow of blood injected at the distal tip at the predetermined flow rate pattern; and compute at least one of a proximal exterior conductance or a distal exterior conductance at the distal tip of the at least one injector member using data indicative of the measurements of pressure and the predetermined flow rate pattern. a first pressure sensor disposed proximate to the distal tip of the at least one injector member; a second pressure sensor disposed at an outer surface of the at least one injector member, at a predetermined separation proximal from the distal tip; an injection flow rate source coupled to the injection member to control the flow rate of fluid from the distal tip to a predetermined flow rate pattern; and a console (802, 905) comprising at least one processing unit programmed to: receive data indicative of measurements of pressure using the first pressure sensor and the second pressure sensor over a time interval T with the flow of blood injected at the distal tip at the predetermined flow rate pattern; and compute at least one of a proximal exterior conductance or a distal exterior conductance at the distal tip of the at least one injector member using data indicative of the measurements of pressure and the predetermined flow rate pattern. receive data indicative of measurements of pressure using the first pressure sensor and the second pressure sensor over a time interval T with the flow of blood injected at the distal tip at the predetermined flow rate pattern; and compute at least one of a proximal exterior conductance or a distal exterior conductance at the distal tip of the at least one injector member using data indicative of the measurements of pressure and the predetermined flow rate pattern.