Absolute blood volume estimation device and method

A dialysis machine for estimating absolute blood volume, the dialysis machine comprising:

• an injector to inject a predetermined volume of dilution indicator liquid into a blood stream of a patient;
• a receiver to obtain, from a sensor, a series of measurements of hemoconcentration of at least one blood characteristic of the patient over a time period, the series of measurements including a hemoconcentration at a dilution test time during the time period, and the series of measurements of hemoconcentration based on blood volume compared to the predetermined volume of dilution indicator liquid;
• memory including instructions, which when executed by a processor, cause the processor to:
• estimate parameters to generate a physiological model corresponding to the time period, the parameters estimated based on the series of measurements, and the parameters including the hemoconcentration at the dilution test time, a volume of a first compartment and a volume of a second compartment at the dilution test time and at a dilution injection time of the time period, the physiological model being specific to the patient and the time period;
• and
• determine an absolute blood volume of the patient at a specified time using the physiological model and the series of measurements of hemoconcentration;
• and
• a display portion to display the absolute blood volume.