Measurement of fluid volume of a blood oxygenator in an extracorporeal circuit

A method of monitoring a blood volume of an oxygenator in an extracorporeal circuit, the method comprising:

• (a) introducing, at an introduction location, a temperature change to passing blood in the extracorporeal circuit, the temperature change corresponding to a temperature in a heating/cooling system thermally coupled to the extracorporeal circuit;
• (b) sensing passage of the introduced temperature change in the extracorporeal circuit downstream of the oxygenator;
• (c) determining a time parameter derived from travel of the introduced temperature change from the introducing location to the sensor;
• and
• (d) determining the blood volume of the oxygenator based on a blood flow rate in the extracorporeal circuit and the time parameter.

A method of monitoring a blood volume of an oxygenator in an extracorporeal circuit, the method comprising:

• (a) introducing, from gas delivery system coupled to the extracorporeal circuit, a change in a gas property of blood flowing in the extracorporeal circuit;
• (b) sensing in the extracorporeal circuit downstream of the oxygenator passage of the changed gas property in the blood;
• and
• (c) calculating the blood volume of the oxygenator based on a blood flow rate in the extracorporeal circuit and a time parameter derived from travel of the changed gas property from the introduction to the sensor.

A method of dynamically monitoring an oxygenator blood volume in an extracorporeal circuit, the method comprising:

• (a) determining at a first time, a first relative oxygenator blood volume corresponding to a first flow rate in the extracorporeal circuit and a first time parameter derived from a sensed passage by an outflow sensor of a first indicator through the oxygenator;
• (b) determining at a second time, a second relative oxygenator blood volume corresponding to a second flow rate in the extracorporeal circuit and a second time parameter derived from a sensed passage by the outflow sensor of a second indicator through oxygenator;
• and
• (c) comparing the first relative oxygenator blood volume and the second relative oxygenator blood volume to assess a change in oxygenator blood volume.

A method of monitoring a blood volume of an oxygenator in an extracorporeal circuit, the method comprising:

• (a) determining a flow rate in the extracorporeal circuit;
• (b) injecting an indicator into the extracorporeal circuit;
• (c) sensing a time of occurrence of the injection of the indicator in the extracorporeal circuit;
• (d) determining a time parameter at least partly derived from a dilution curve corresponding to the injected indicator;
• and
• (e) determining the blood volume of the oxygenator based on the determined time parameter and the determined flow rate in the extracorporeal circuit.