Fluid flow monitoring method and system

• US 4,743,228 A
• Filed: 08/18/1986
• Issued: 05/10/1988
• Est. Priority Date: 08/18/1986
• Status: Expired due to Term

• Current Assignee: ALARIS Medical Systems, Inc. (Becton, Dickinson & Co)
• Original Assignee: Ivax Corporation (Teva Pharmaceutical Industries, Ltd.)
• Inventors: Butterfield, Robert D.
• Primary Examiner(s): Coven, Edward M.
• Application Number:
  US06/897,618
• Time in Patent Office: 631 Days
• Field of Search: 604/50, 604/65, 604/66, 604/67, 604/118, 604/244, 604/245
• US Class Current: 604/505
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse

Abstract

The invention is directed to a fluid flow monitoring method and system for parenteral fluid delivery systems for use in situations, such as with sedentary patients, when wide pressure variations are not expected. The resistance of the fluid delivery system is determined from the ratio of pressure differences at high and low fluid flow rates to differences in the high and low fluid flow rates. The resistance is used to develop a pressure limit from the sum of the pressure at low fluid flow rates and the product of the resistance and the high fluid flow rate. The pressure limit is compared with the pressure monitored and if the pressure monitored exceeds the calculated pressure limit, an alarm is actuated to warn medical personnel of an occlusion or other fluid flow fault. Additionally, if the noise level (pressure) excess predetermined limits during the periods of low and high fluid flow, the pressure monitoring is terminated.

Claims

1. A system for monitoring the pressure of parenteral fluid in a fluid delivery system which includes a pump, tubing for transmitting pumped fluid to a cannula adapted to be inserted into a patient'"'"'s blood vessel, the pressure monitoring system comprising:

(a) means to control the rate of fluid flow through the delivery system to the patient at a predetermined low flow rate (F_Low) and at a predetermined high flow rate (F_Hi);

(b) means to sense the fluid pressure within the fluid delivery system;

(c) means to determine the difference in fluid pressure within the fluid delivery system during periods of the predetermined low flow rate and during period of the predetermined high flow rate;

(d) means to determine the difference between the predetermined high flow rate and the predetermined low flow rate;

(e) means to determine the resistance (R) of the fluid delivery system to fluid flow therethrough from the ratio of the fluid pressure difference to the fluid flow rate difference;

(f) means to calculate a pressure limit (P_Lim) from the product of resistance (R) and the high flow rate (F_Hi);

(g) means to compare the fluid pressure sensed within the fluid delivery system during a monitoring period with the calculated pressure limit (P_Lim); and

(h) means to generate an alarm signal when the pressure sensed exceeds the calculated pressure limit.

2. The monitoring system of claim 1 including means to control the low fluid flow rate at essentially zero.

3. The monitoring system of claim 2 including means to determine pressure variations in the fluid delivery system when the fluid flow rate therethrough is at essentially zero.

4. The monitoring system of claim 1 wherein the means to calculate the pressure limit (P_Lim) from the product of the resistance and the high flow rate adds a constant K thereto.

5. The monitoring system of claim 4 wherein the constant K includes the fluid pressure (P_Low) during the predetermined low flow rate.

6. The monitoring system of claim 5 including means to detect the peak-to-peak values of pressure (P_pp) during the predetermined low flow rate.

7. The monitoring system of claim 6 wherein the constant K is the sum of P_Low and the peak-to-peak values of pressure during periods of low flow rate and a fixed offset constant.

8. The monitoring system of claim 1 wherein the means to determine resistance (R) and to calculate the automatic pressure limit (P_Lim) is a microprocessor.

9. The monitoring system of claim 1 including means to determine fluid pressure variations.

10. The monitoring system of claim 9 including means to terminate the pressure monitoring system when the pressure variations exceed predetermined limits.

11. The monitoring system of claim 9 including means to terminate the operation of the monitoring system if the fluid pressure variations exceed predetermined limits for a predetermined time period or for a predetermined volume of fluid.

12. A method for monitoring the pressure of parenteral fluid in a fluid delivery system which includes a pump, tubing for transmitting pumped fluid to a cannula adapted to be inserted into a patient'"'"'s blood vessel, the method of monitoring the pressure comprising:

(a) controlling the rate of fluid through the delivery system to the patient at a predetermined low flow rate (F_Low) and at a predetermined high flow rate (F_Hi);

(b) sensing the fluid pressure within the fluid delivery system;

(c) determining the difference in fluid pressure within the fluid delivery system during the predetermined low flow rate and during the predetermined high flow rate;

(d) determining the difference between predetermined the high flow rate and the predetermined low flow rate;

(e) determining the resistance (R) of the fluid delivery system to fluid flow therethrough from the ratio of the pressure difference to the fluid flow rate difference;

(f) calculating the pressure limit (P_Lim) from the product of the resistance (R) and the high flow rate (F_Hi);

(g) comparing the fluid pressure (P_Hi) sensed within the fluid delivery system during a monitoring period with the calculated pressure limit (P_Lim); and

(h) generating an alarm signal when the pressure sensed exceeds the calculated pressure limit.

13. The pressure monitoring method of claim 12 wherein the low fluid flow rate is at essentially zero flow.

14. The pressure monitoring method of claim 12 wherein the pressure limit (P_Lim) is calculated from the produce of the resistance K and the high flow rate and the sum thereof.

15. The pressure monitoring method of claim 14 wherein the constant K includes a factor representing the fluid pressure (P_Low) during low flow rate.

16. The pressure monitoring method of claim 14 including detecting the peak-to-peak value of pressure (P_pp) during periods of low flow rate.

17. The pressure monitoring method of claim 16 wherein the constant K is the sum of the flow rate (P_Low) and the peak-to-peak value of pressure (P_pp) during periods of flow rate.

18. The pressure monitoring method of claim 13 including determining pressure variations in the fluid delivery system.

19. The pressure monitoring method of claim 18 wherein the pressure variations detected are compared with a predetermined limit therefor.

20. The pressure monitoring method of claim 19 including terminating the pressure monitoring method when the pressure variations detected exceed the predetermined limits.

21. The pressure monitoring method of claim 19 including terminating the operation of the monitoring method if the fluid pressure variations exceed predetermined limits for a predetermined time period or for a predetermined volume of fluid flow.