Fluid flow resistance monitoring system

• US 6,213,972 B1
• Filed: 09/04/1998
• Issued: 04/10/2001
• Est. Priority Date: 09/13/1994
• Status: Expired due to Term

• Current Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Original Assignee: ALARIS Medical Systems, Inc. (Becton, Dickinson & Co)
• Inventors: Farquhar, Allen, Butterfield, Robert D.
• Primary Examiner(s): MENDEZ, MANUEL A
• Application Number:
  US09/148,456
• Time in Patent Office: 949 Days
• Field of Search: 604/65-67, 604/30-35, 604/500, 604/131, 604/153, 604/246, 128/DIG. 12, 128/13
• US Class Current: 604/67
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse

Abstract

Flow parameters in a fluid delivery assembly are determined by monitoring pressure responses and processing those responses along with information regarding the fluid flow. In one aspect, a processor controls the pump to pump flow quantities in accordance with a pseudorandom code. Portions of the resulting pressure signal sensed are then decoded in accordance with the pseudorandom code. An estimate of the equilibrium pressure is generated from the decoded pressure values, while a summation of the pressure samples is generated from the undecoded pressure signals. The resistance to fluid flow of the system is determined from the estimated equilibrium pressure and pressure summation. For low flow rates, a processor controls the pump to pump fluid in a series of fluid boluses, with each fluid bolus delivered in the beginning of a separate timeslot. The equilibrium pressure is measured at the end of each timeslot, and a summation of the pressure samples is generated from the pressure signals. For high flow rates, the pump is controlled to vary the flow rate and the change in pressure is divided by the change in flow to directly determine the resistance. A resistance display continuously displays the resistance of the system. The pseudorandom coding and decoding can be used to filter out pressure-response crosstalk caused by multiple fluid infusion segments feeding into a common line.

Claims

1. A system for monitoring at least one flow parameter in a fluid delivery assembly in which a flow control device acts on a fluid conduit to control the flow of fluid through the conduit, the system comprising:

a pressure sensor coupled to the conduit for providing pressure signals in response to the pressure sensed in the conduit; and

a processor that controls the flow control device to cause flow in accordance with a pseudorandom pattern, receives the pressure signals, and processes those pressure signals to determine a flow parameter.

2. A method for determining at least one flow parameter in a fluid delivery assembly in which a flow control device acts on a fluid conduit to control the flow of fluid through the conduit, the method comprising the steps of:

(a) providing a pseudorandom pattern,

(b) controlling the flow control device to cause flow in accordance with the pseudorandom pattern;

(c) monitoring the pressure in the conduit and generating pressure signals in response to the monitored pressure;

(d) processing the pressure signals to determine a flow parameter.

3. The system of claim 1, wherein the processor includes a pseudorandom binary sequence encoder, and the pseudorandom pattern is a pseudorandom binary sequence code.

4. The system of claim 1, wherein the flow parameter is fluid resistance.

5. The system of claim 1, further comprising:

an alarm, wherein the processor is configured to determine if the determined flow parameter is unsatisfactory and to activate the alarm if the determined flow parameter is unsatisfactory.

6. The system of claim 1, wherein the processor is configured to determine if the monitored pressure exceeds a pressure threshold, and to activate the alarm if the monitored pressure exceeds the pressure threshold.

7. The system of claim 6, wherein the processor is configured to determine an average monitored pressure and to determine if the average monitored pressure exceeds a pressure threshold, and to activate the alarm if the average monitored pressure exceeds the pressure threshold.

8. The method of claim 2, wherein the step of processing the pressure signals to determine a flow parameter includes processing the pressure signals to determine flow resistance.

9. The method of claim 2, including the further step of:

(e) displaying an indicia of the value of the selected flow parameter.

10. The method of claim 9, wherein the step of displaying an indicia of the selected flow parameter includes providing a numerical readout of the selected flow parameter.

11. The method of claim 2, including the further steps of:

(f) determining if the determined flow parameter is unsatisfactory, and

(g) activating an alarm if the determined flow parameter is unsatisfactory.

12. The method of claim 11, including the further steps of:

(h) determining if the monitored pressure exceeds a pressure threshold, and

(i) activating the alarm if the monitored pressure exceeds the pressure threshold.

13. The method of claim 12, wherein the step of determining if the monitored pressure exceeds the threshold includes the step of determining an average of recent monitored pressures, and comparing the average pressure to the threshold.

14. The method of claim 2, comprising the further step of:

(j) selecting a flow rate;

wherein the step of controlling the flow control device to cause flow in accordance with the pseudorandom pattern includes controlling the flow control device to cause flow at the selected flow rate.

15. The method of claim 2, comprising the further step of:

(k) processing the pressure signals to determine an estimated equilibrium pressure.