Automated control mechanisms and methods for controlling fluid flow in a hemodialysis apparatus
Automated control mechanisms and methods for controlling fluid flow in a hemodialysis apparatus are described. The methods can involve a controller receiving information from a pressure sensor in a control chamber of a reciprocating diaphragm-based blood pump and causing the application of a time-varying pressure waveform on a diaphragm of the blood pump during a fill-stroke of the blood pump. The controller can be configured and programmed to monitor a pressure variation in the control chamber measured by the pressure sensor and to compare the measured pressure variation to a pre-determined value. Based on such comparison, the controller can initiate a procedure to pause or stop a dialysate pump of the hemodialysis apparatus if the magnitude of the measured pressure variation deviates from the pre-determined value.
1. A method for controlling fluid flow in a hemodialysis apparatus comprising:
receiving, at a controller, fluid pressure information from a pressure sensor in fluid communication with a control chamber of a blood pump comprising a reciprocating diaphragm between a blood chamber and the control chamber;
causing, in response to control signals from the controller, a pneumatic valve to open and close to apply a time-varying pressure waveform on the diaphragm of the blood pump during a fill stroke of the blood pump, the pneumatic valve fluidly connecting the control chamber with a pressure source;
monitoring, by the controller, a pressure variation in the control chamber measured by the pressure sensor;
determining, by the controller, a blood flow metric based on a variation of a peak-to-peak pressure in the control chamber during the fill stroke; and
alerting, by the controller, a user based on the blood flow metric.
2. The method of claim 1 , wherein alerting the user includes alerting the user after the blood flow metric remains below a predetermined standard for a plurality of fill strokes.
3. The method of claim 1 , further comprising:
evaluating, by the controller, a measured pressure in the control chamber during time periods when an absolute value of fluid pressure in the control chamber is decreasing, and
pausing or stopping, by the controller, the dialysate pump based on the blood flow metric.
4. The method of claim 1 , further comprising pausing or stopping a dialysate pump when the blood flow metric drops below a predefined value.
5. The method of claim 4 , wherein determining the blood flow metric includes determining the blood flow metric after an initial delay period.
6. The method of claim 1 , wherein the time-varying pressure waveform is controlled by the pneumatic valve opening in a periodic fashion characterized by a frequency and duration of an open period.
7. The method of claim 1 , wherein a dialysate pump comprises a reciprocating diaphragm-based pump, and wherein alerting the user includes comparing the blood flow metric to a pre-determined value based on a pressure over a period of time generated by the blood pump that provides sufficient pressure in a blood compartment of a dialyzer to allow the dialysate pump to receive a full stroke-volume of fluid from the dialyzer.
8. The method of claim 2 , wherein alerting the user includes alerting the user, by the controller, after the blood flow metric remains below the predetermined standard for two fill strokes.
9. The method of claim 1 , wherein the controller alerts the user before the blood flow metric is low enough to require stopping a dialysate pump.
10. The method of claim 9 , wherein alerting the user includes alerting the user to provide an opportunity to correct a poor blood flow condition caused by a constricted blood tubing or a restriction in the fistula.
11. The method of claim 1 , wherein alerting the user includes alerting the user based on a comparison of the blood flow metric to an expected value or a value obtained previously.
12. The method of claim 1 , further comprising sending, by the controller, a blood flow metric value to a graphical user interface.
13. The method of claim 12 , wherein determining the blood flow metric includes regularly updating, by the controller, the displayed blood flow metric value.
14. The method of claim 12 , further comprising displaying by the graphical user interface the blood flow metric value as a numeral or a graphical indicator.
15. The method of claim 4 , further comprising restarting, by the controller, the dialysate pump after the blood flow metric is above a predetermined blood flow metric for a predetermined number of fill strokes.
16. A method for controlling fluid flow in a hemodialysis apparatus where a reciprocating diaphragm blood pump moves blood through a dialyzer and a dialysate pump moves dialysate through the dialyzer, the method comprising:
receiving, by a controller, fluid pressure information from a pressure sensor in fluid communication with a control chamber of a blood pump comprising a reciprocating diaphragm between a blood chamber and the control chamber;
causing, by the controller, a pneumatic valve to open and close to thereby apply time-varying pressure on the diaphragm of the blood pump during a fill stroke of the blood pump, the pneumatic valve fluidly connecting the control chamber with a pressure source;
monitoring, by the controller, a pressure variation in the control chamber measured by the pressure sensor;
determining, by the controller, a blood flow metric based on the pressure variation measured during the fill stroke;
alerting, by the controller, a user that blood flow is inadequate via a graphical user interface when the blood flow metric drops below a predetermined value; and
completing one or more blood pump fill strokes after alerting the user that blood flow is inadequate and before stopping the dialysate pump in response to the blood flow metric.
17. The method of claim 16 , further comprising:
stopping, by the controller, the dialysate pump and continuing to operate the blood pump after alerting the user that blood flow is inadequate.
18. The method of claim 17 , further comprising restarting, by the controller, the dialysate pump when the blood flow metric exceeds a second predetermined value.
19. The method of claim 18 , wherein restarting the dialysate pump includes restarting the dialysate pump when the blood flow metric exceeds the second predetermined value for more than one stroke of the blood pump diaphragm.
20. The method of claim 18 , wherein restarting the dialysate pump includes restarting the dialysate pump when the blood flow metric exceeds the second predetermined value for more than five strokes of the blood pump diaphragm.
21. The method of claim 16 , wherein determining the blood flow metric includes determining the blood flow metric after an initial delay period.
22. The method of claim 16 , wherein alerting the user includes alerting the user that blood flow is inadequate when the blood flow metric drops below the predetermined value for one stroke of the blood pump diaphragm.
23. The method of claim 16 , wherein alerting the user includes alerting the user that blood flow is inadequate when the blood flow metric drops below the predetermined value for two strokes of the blood pump diaphragm.
24. The method of claim 16 , wherein alerting the user includes alerting the user that blood flow is inadequate when the blood flow metric drops below the predetermined value for three strokes of the blood pump diaphragm.