METHOD AND APPARATUS FOR AN EXTRACORPOREAL CONTROL OF BLOOD GLUCOSE
A method for controlling the blood glucose level of a patient and periodically calibrating the glucose sensor using a calibration solution. The method controls the level of blood glucose in a patient through an extracorporeal blood circuit by: withdrawing blood from a vascular system in the patient to the extracorporeal circuit; removing ultrafiltrate from the withdrawn blood in the circuit; determining a level of glucose present in the blood based on the removed ultrafiltrate; infusing at least a portion of the removed ultrafiltrate and the withdrawn blood into the vascular system, and infusing insulin into the patient based on the determined level of glucose.
1 . A method for controlling a level of blood glucose in a patient using an extracorporeal blood circuit, said method comprising:
a. withdrawing blood from a vascular system in the patient to the extracorporeal circuit;
b. removing ultrafiltrate from the withdrawn blood in the circuit and passing the ultrafiltrate through an ultrafiltration passage;
c. determining a level of glucose present in the blood using a glucose sensor monitoring ultrafiltrate flowing through an ultrafiltration passage;
d. infusing insulin into the vascular system to control the blood glucose, wherein a rate of insulin infused is based on the determined level of glucose;
e. introducing a calibration solution into the ultrafiltrate passage; and
f. calibrating the glucose sensor based on a measurement made by the sensor of the calibration solution flowing through the ultrafiltrate passage.
2 . A method as in claim 1 where a rate of infusion is adjusted based on a current level of glucose and a prior level of glucose.
3 . A method as in claim 1 wherein at least a portion of the removed ultrafiltrate is infused into the vascular system.
4 . A method as in claim 3 wherein the portion of the removed ultrafiltrate is returned to the withdrawn blood upstream of a filter removing the ultrafiltrate.
5 . A method as in claim 1 further comprising introducing the calibration solution into the ultrafiltrate flow passage in a flow direction in the ultrafiltrate passage opposite to a flow direction of the ultrafiltrate in the ultrafiltrate passage.
6 . A method as in claim 1 further comprising introducing the calibration solution from the ultrafiltrate passage into the withdrawn blood and upstream of a filter removing the ultrafiltrate.
7 . A method as in claim 1 further comprising removing the calibration solution from the ultrafiltrate passage without introducing the calibration solution into the withdrawn blood.
8 . A method as in claim 1 wherein the insulin is infused into the patient by first introducing the insulin into the withdrawn blood in the circuit.
9 . A method as in claim 1 wherein an amount of calibration solution introduced into the ultrafiltrate passage is less than a volume of the ultrafiltrate passage.
10 . A method as in claim 9 wherein the amount of calibration solution introduced into the ultrafiltrate passage is removed from the circuit without being introduced into the vascular system.
11 . A method as in claim 1 further comprising blocking introduction of the calibration solution into the ultrafiltrate passage while ultrafiltrate is being removed from a filter in the circuit.
12 . A method as in claim 11 further comprising of placing a spring loaded one way valve in the calibration solution line to block the calibration solution during removal of ultrafiltrate.
13 . A method as in claim 1 wherein the infusion of the removed ultrafiltrate to the vascular system is interrupted while the calibration solution is introduced into the ultrafiltrate passage.
14 . A method as in claim 1 further comprising preventing withdrawal of blood through a blood return passage in the circuit during introduction of the calibration solution in the ultrafiltrate passage.
15 . A method as in claim 1 wherein the removal of ultrafiltrate and the introduction of the calibration solution is performed with a peristaltic pump acting on the ultrafiltrate passage, wherein the pump operates in opposite rotational direction to pump the ultrafiltrate and the calibration solution.
16 . A method of claim 1 , wherein calibrating the glucose sensor is based on a measurement made by the glucose sensor of the calibration solution flowing through the ultrafiltrate passage.
17 . A method of claim 1 further comprising measuring the calibration solution with a reference glucose sensor and calibrating the glucose sensor based on the measurement made by the reference glucose sensor of the calibration solution during a calibration sequence.
18 . A method of claim 17 wherein the glucose sensor measures a level of glucose present in the blood during the calibration sequence.
19 . A method as in claim 1 , wherein the step of introducing a calibration solution into the ultrafiltrate passage comprises introducing a calibration solution into the ultrafiltrate passage in a flow direction in the ultrafiltrate passage opposite to a flow direction of the ultrafiltrate in the ultrafiltrate passage.
20 . A method as in claim 1 , wherein wherein the removal of ultrafiltrate and the introduction of the calibration solution is performed with a peristaltic pump acting on the ultrafiltrate passage, wherein the pump operates in opposite rotational directions to pump the ultrafiltrate and the calibration solution.