Blood leak monitoring method and apparatus
A method for monitoring for leaks or disconnections in an extracorporeal blood circuit, comprising the steps of operating a blood pump to circulate blood through an extracorporeal blood circuit; opening a shunt connection between the arterial and venous blood flow portions; sensing the presence of air from any leaks or disconnections within the venous blood flow portion, and taking corrective action if the presence of air is noted. The shunt connection is typically periodically but only briefly opened, to check for leaks in the typically positive pressure portion of the venous set.
1 . The method of monitoring for leaks or disconnections in an extracorporeal blood circuit comprising a blood pump, an arterial blood flow portion operating at subatmospheric pressure and extending upstream from the pump to a first connection with the patient's vascular system, and a venous blood flow portion extending downstream from the pump to a second connection with the patient's vascular system, which method comprises:
operating said blood pump to circulate blood through said extracorporeal blood circuit; opening a shunt connection between the arterial and venous blood flow portions; sensing the presence of air from any leaks or disconnections within said venous blood flow portion; and taking corrective action if the presence of said air is noted.
2 . The method of claim 1 in which said shunt connection is briefly opened and closed on a repeated basis.
3 . The method of claim 1 in which said presence of air is sensed by a sensor located to sense for said air near to said second connection.
4 . The method of claim 2 in which said shunt connection is opened and closed using only a single unclamping/clamping action.
5 . The method of claim 1 in which said venous blood flow portion is clamped, as said shunt connection is opened, at a position to promote blood flow through said shunt connection from the venous blood flow portion downstream of said shunt connection to the arterial blood flow portion operating at subatmospheric pressure, to promote flow reversal in a section of said venous blood flow portion that connects with the patient's vascular system.
6 . The method of claim 1 in which said shunt connection is opened for no more than about one second at a time.
7 . The method of claim 6 in which said presence of air is sensed by a sensor located to sense for said air near to said second connection.
8 . The method of claim 7 in which said venous blood flow portion is clamped, as said shunt connection is opened, at a position to promote blood flow through said shunt connection from the venous blood flow portion to the arterial blood flow portion operating at subatmospheric pressure, to promote said flow reversal in a section of said venous blood flow portion that includes said second connection with the patient's vascular system.
9 . The method of claim 8 in which said arterial blood flow portion continues to convey blood through said first connection with the patient's vascular system and to convey said blood away from said patient, when said flow is being reversed in said venous blood flow portion, and also when said flow is normal in said venous blood flow portion.
10 . The method of claim 1 in which said arterial blood flow portion continues, by action of said blood pump, to convey blood through said first connection with the patient's vascular system and to convey said blood away from said patient, when said flow is being reversed in said venous blood flow portion, and also when said flow is normal in said venous blood flow portion.
11 . The method of claim 1 in which, by action of said blood pump, blood flows from said patient through the first connection with the patient's vascular system into the arterial blood flow portion and away from said patient when said shunt connection is open, and also when said shunt connection is closed but blood is circulating through said extracorporeal blood circuit.
12 . The method of claim 1 in which said shunt connection comprises a single flow path.
13 . An extracorporeal blood circulating device, which comprises:
a blood pump;
an arterial blood flow tube portion extending upstream from the pump to a first connector for connection with the patient's vascular system;
a venous blood flow tube portion extending downstream from the pump to a second connector for connection with the patient's vascular system;
a shunt connection permitting direct flow between the arterial and venous blood flow tube portions without passing through the blood pump;
a first valve controlling flow through said shunt connection; and
a first valve control unit.
14 . The blood circulating device of claim 13 , further comprising a second valve to block flow through a portion of said venous blood flow portion which is upstream in normal flow from said shunt connection, said control unit normally causing said second valve to be open when the first valve is closed, and the second valve to be closed when the first valve is open.
15 . The blood circulating device of claim 14 , in which the presence of air is sensed by a sensor located to sense for said air near to said second connector and to shut down said system when air is sensed.
16 . The blood circulating device of claim 14 , in which said first and second valves use only a single unclamping/clamping action.
17 . The blood circulating device of claim 14 , in which said shunt connection comprises a single flow path.
18 . The blood circulating device of claim 17 , in which said first and second valves use only a single unclamping/clamping action.
19 . The blood circulating device of claim 18 , further comprising an air sensor located near to said second connector
20 . The blood circulating device of claim 13 , in which the presence of air is sensed by a sensor located to sense for said air near to said second connector and to shut down said system when air is sensed.