Instantaneous volume measurement system and method for non-invasively measuring liquid parameters

• US 5,421,208 A
• Filed: 05/19/1994
• Issued: 06/06/1995
• Est. Priority Date: 05/19/1994
• Status: Expired due to Term

• Current Assignee: Baxter International Inc.
• Original Assignee: Baxter International Inc.
• Inventors: Pawlak, Kenneth E., Packard, Warren J.
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): Artis, Jewel V.
• Application Number:
  US08/245,781
• Time in Patent Office: 383 Days
• Field of Search: 673/861, 673/861.39, 417/63, 417/43, 417/384, 417/395
• US Class Current: 73/861
• CPC Class Codes: A61M 5/16809 by repeated filling and emptying of an intermediate volume pressure infusion using positive displacement pumps A61M5/142
• CPC Class Codes: A61M 5/16886 for measuring fluid flow rate, i.e. flowmeters
• CPC Class Codes: G01F 1/00 Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow measuring a proportion of the volume flow G01F5/00
• CPC Class Codes: G01F 1/86 Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure

Abstract

A non-invasive technique and system is provided for measuring flow of liquid driven by a flexible diaphragm of a membrane pump (18). Flow, pressure and/or temperature of a gas, such as air, used to drive the pump (18) is continuously monitored. Instantaneous volume of liquid being pulled into or out of a chamber of the pump (18) can be calculated from measured values of the gas used to drive the pump (18). Sensors (10, 12 and/or 14) are used to measure values relating to the gas. The sensed parameters are concurrently monitored and continuously determine the amount of gas flowing to and from the diaphragm of the membrane pump (18) utilized to move liquid within a liquid pathway. The measurements may then be used to calculate the instantaneous flow rate of the liquid.

Claims

1. A system for monitoring a liquid driven by a pump and calculating a parameter related to the liquid, the system comprising:

providing a gas to drive the pump;

means for measuring flow and pressure of the gas used to drive the pump; and

means for calculating instantaneous flow rate of the liquid flowing into or out of the pump from the measured flow and pressure of the gas.

2. The system of claim 1 wherein the means for calculating further calculates instantaneous liquid volume from the instantaneous flow rate.

3. The system of claim 1 wherein the means for measuring measures temperature of the gas.

4. The system of claim 1 wherein the means for measuring non-invasively measures the at least one variable.

5. The system of claim 1 wherein the liquid driven by the pump flows into or out of a sterile disposable.

6. A system for measuring a liquid-related value of a liquid driven by a pump, the system comprising:

means for providing a gas to drive the pump;

first sensing means sensing flow of the gas driving the pump;

second sensing means sensing pressure of the gas driving the pump; and

calculating means determining instantaneous flow rate of the liquid flowing into or out of the pump from the sensed gas flow and the sensed pressure.

7. The system of claim 6 further comprising:

third sensing means for sensing temperature of the gas for driving the pump.

8. The system of claim 7 wherein the calculating means determines instantaneous flow rate from the sensed gas flow, the sensed pressure and the sensed temperature.

9. The system of claim 6 wherein the means for calculating determines instantaneous volume from the determined instantaneous flow rate of the liquid.

10. A method for non-invasively monitoring parameters of a liquid driven by a pump, the method comprising the steps of:

providing a gas to drive the pump;

measuring gas flow and gas pressure of the gas driving the pump; and

calculating instantaneous flow rate of the liquid flowing into or out of the pump based on the at least one measured value.

11. The method of claim 10 further comprising the step of:

measuring temperature of the gas driving the pump.

12. The method of claim 11 wherein the flow rate is calculated by using the measured temperature, gas flow and gas pressure.

13. The method of claim 10 further comprising the step of:

calculating instantaneous liquid volume from the instantaneous flow rate.

14. The method of claim 10 further comprising the step of:

pumping the liquid into or out of a sterile disposable.