Flow balancing devices, methods, and systems
The disclosed subject matter relates to extracorporeal blood processing or other processing of fluids. Volumetric fluid balance, a required element of many such processes, may be achieved with multiple pumps or other proportioning or balancing devices which are to some extent independent of each other. This need may arise in treatments that involve multiple fluids. Safe and secure mechanisms to ensure fluid balance in such systems are described.
1 . A method for controlling flow in a fluid circuit, comprising:
using an extracorporeal fluid treatment system that includes a controller, controlling a balancing component that balances flows to and from a patient to maintain, or restore, a patient's normal fluid balance by regulating speeds of multiple pumps;
attaching a replaceable disposable fluid circuit through which flows of fluid are balanced to the extracorporeal fluid treatment system;
attaching bags containing fluids to the replaceable disposable fluid circuit;
pumping a priming fluid through the replaceable disposable fluid circuit including pumping fluid through pumping tube segments thereof;
after completion of the pumping of the priming fluid, detecting pressures in portions of the replaceable disposable fluid circuit, with pressure sensors, caused by a hydrostatic head of the fluids in the bags attached to the replaceable disposable fluid circuit;
determining, over a time interval, a rate of change of said hydrostatic-head pressures; and
based on the determined rate of change of said hydrostatic-head pressures, generating a retry command or a fail command.
2 . The method of claim 1 , wherein the pressure sensors are located at respective inlets of said multiple pumps.
3 . The method of claim 1 , further comprising, during a blood treatment regulating speeds of the multiple pumps responsively to the pressures indicated by sa pressure sensors.
4 . The method of claim 1 , wherein the generating a retry or fail command is responsive to a difference in magnitudes of the pressures detected by the pressure sensors.
5 . The method of claim 1 , further comprising:
using each of the multiple pumps, generating a pressure between one of the pressure sensors and a control valve and detecting a pressure property indicating a closed state of the control valve or of at least one of the multiple pumps.
6 . The method of claim 5 , wherein
the generating the pressure includes cycling at least one of the multiple pumps.
7 . The method of claim 6 , wherein the at least one of the multiple pumps is a blood pump.
8 . The method of claim 7 , wherein the generating the pressure includes running one of the multiple pumps at a rate of 10-20 ml/min.
9 . The method of claim 1 , further comprising:
comparing the determined rate of change to first and second thresholds corresponding respectively to partial occlusion and full occlusion, and wherein a retry command is generated when the first threshold is exceeded and a fail command is generated when the second threshold is exceeded.
10 . The method of claim 9 , further comprising compensating the detected pressures for pressure sensor elevation differences prior to the comparing.
11 . The method of claim 9 , wherein, during the determining, pumps contributing to the detected pressures are halted so that the detected pressures are attributable exclusively to the hydrostatic head.
12 . The method of claim 9 , wherein the comparing includes comparing respective rates of change determined at plural inlet pressure sensors to detect an asymmetry indicative of a partially occluded bag line.
13 . The method of claim 1 , wherein when the fail command indicates an occlusion in a replacement-fluid inlet line, the controller stops both a fresh treatment fluid pump and a replacement fluid pump.
14 . The method of claim 1 , further comprising maintaining a retry count and escalating from a retry command to a fail command after a predefined number of retries.
15 . A system for controlling flow in a fluid circuit, comprising:
an extracorporeal fluid treatment system having a controller configured to command a balancing component that is configured to balance flows to and from a patient to maintain, or restore, a normal fluid balance of the patient by regulating speeds of two pumps of the balancing component;
a replaceable disposable fluid circuit attached to the extracorporeal fluid treatment system and connected to said two pumps and configured to convey fluids to be balanced;
a source of a priming fluid connected to the replaceable disposable fluid circuit and connected to a third pump that engages a pumping tube segment of the replaceable disposable fluid circuit; and
bags containing fluids attached to the fluid circuit, wherein
the controller is configured to pump the priming fluid through the replaceable disposable fluid circuit during a priming operation,
the controller is further configured to, after completion of the priming operation, detect pressures, with pressure sensors, in portions of the replaceable disposable fluid circuit caused by a hydrostatic head of the fluids in the bags,
the controller is further configured to determine, over a time interval, a rate of change of said hydrostatic-head pressures, and
the controller is further configured to generate a retry or fail command based on the determined rate of change of said hydrostatic-head pressures.
16 . The system of claim 15 , wherein the pressure sensors are located at respective inlets of said two pumps.
17 . The system of claim 15 , wherein the controller is configured to, during a blood treatment, regulate speeds of the two pumps responsively to pressures indicated by said pressure sensors.
18 . The system of claim 15 , wherein the controller is configured such that the retry or fail command is generated responsively to a difference in magnitudes of the pressures detected by the pressure sensors.
19 . The system of claim 18 , wherein generating a pressure between one of the pressure sensors and a control valve includes cycling a blood pump.
20 . The system of claim 15 , wherein
the controller is further configured to detect a pressure between at least one of the pumps and a control valve to identify an occlusion failure of the control valve or of the at least one of the pumps.