# US 10,117,985 B2 · Determining a volume of medical fluid pumped into or out of a medical fluid cassette

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- Number: US 10,117,985 B2
- Document ID: US10117985B2
- Status: Granted
- Kind: B2
- Application number: 13/972,498
- Filed: 2013-08-21
- Published: 2015-02-26
- Granted: 2018-11-06
- Earliest claimed: 2013-08-21
- Assignees: Fresenius Medical Care Holdings, Inc.
- Applicants: Fresenius Medical Care Holdings, Inc.
- Inventors: Tri Ly; Jie Zhu; Kulwinder S. Plahey
- Web page: https://patentgrep.com/patent/US10117985B2

## CPC

- A61M 1/28: Peritoneal dialysis {; Other peritoneal treatment, e.g. oxygenation}
- A61M 1/1522: {the interface being evacuated interfaces to enhance contact}
- A61M 1/1524: {the interface providing means for actuating on functional elements of the cassette, e.g. plungers}
- A61M 1/154: {with sensing means or components thereof}
- A61M 1/155: {with treatment-fluid pumping means or components thereof}
- A61M 1/1561: {at least one cassette surface or portion thereof being flexible, e.g. the cassette having a rigid base portion with preformed channels and being covered with a foil}
- A61M 1/1565: {Details of valves}
- A61M 1/159: {specially adapted for peritoneal dialysis}
- A61M 1/281: {Instillation other than by gravity}
- A61M 1/288: {Priming (priming in extracorporeal blood circuits A61M1/3643)}
- G01F 22/00: Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for
- G01F 22/02: involving measurement of pressure
- A61M 2205/128: with incorporated valves
- A61M 2205/3379: Masses, volumes, levels of fluids in reservoirs, flow rates
- A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)}
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME

## Abstract

A method that includes pumping medical fluid out of or drawing medical fluid into a chamber of a medical fluid cassette, calculating a theoretical volume of fluid pumped out of or drawn into the chamber, and multiplying the theoretical volume of fluid pumped out of or drawn into the chamber by a correction factor to determine a corrected volume of fluid pumped out of or drawn into the chamber.

## Claims

### Claim 1

A method comprising:
(a) pumping a medical fluid out of or drawing a medical fluid into a chamber of a medical fluid cassette such that a pressure of the medical fluid in the medical fluid cassette causes a membrane of the medical fluid cassette to bulge around a perimeter of a piston head;
(b) calculating, by a processor, a theoretical volume of the medical fluid pumped out of or drawn into the chamber;
(c) measuring the pressure of the medical fluid within the medical fluid cassette or within a fluid line connected to the medical fluid cassette;
(d) selecting a correction factor based on the measured pressure, the correction factor corresponding to an amount of bulging of the membrane of the medical fluid cassette;
(e) multiplying, by the processor, the theoretical volume of the medical fluid pumped out of or drawn into the chamber by the correction factor to determine an adjustment volume; and
(f) determining a corrected volume of the medical fluid pumped out of or drawn into the chamber based on the adjustment volume.

### Claim 2 (depends on 1)

The method of claim 1, wherein the adjustment volume is added to the theoretical volume to determine the corrected volume.

### Claim 3 (depends on 1)

The method of claim 1, wherein the method comprises pumping the medical fluid out of the chamber of the medical fluid cassette by driving a piston against the membrane of the medical fluid cassette to decrease a volume of the chamber, calculating the theoretical volume of the medical fluid pumped out of the chamber, and multiplying the theoretical volume of the medical fluid pumped out of the chamber by the correction factor to determine the corrected volume of the medical fluid pumped out of the chamber.

### Claim 4 (depends on 1)

The method of claim 1, wherein the method comprises drawing the medical fluid into the chamber of the medical fluid cassette by retracting a piston to pull the membrane of the medical fluid cassette to increase a volume of the chamber, calculating the theoretical volume of the medical fluid drawn into the chamber, and multiplying the theoretical volume of the medical fluid drawn into the chamber by the correction factor to determine the corrected volume of the medical fluid drawn into the chamber.

### Claim 5 (depends on 1)

The method of claim 1, wherein calculating the theoretical volume of the medical fluid pumped out of or drawn into the chamber comprises determining a linear displacement of a piston.

### Claim 6 (depends on 1)

The method of claim 1, further comprising isolating the chamber prior to measuring the pressure.

### Claim 7 (depends on 6)

The method of claim 6, wherein isolating the chamber comprises closing valves adjacent first and second ports of the chamber.

### Claim 8 (depends on 6)

The method of claim 6, wherein the pressure is measured a period of time after isolating the chamber.

### Claim 9 (depends on 6)

The method of claim 6, wherein the chamber is isolated and the pressure is measured after drawing the medical fluid into the chamber.

### Claim 10 (depends on 6)

The method of claim 6, wherein the chamber is isolated and the pressure is measured after pumping the medical fluid out of the chamber.

### Claim 11 (depends on 1)

The method of claim 1, wherein the correction factor varies as a function of the measured pressure for measured pressures between a first pressure value and a second pressure value, the first pressure value being less than the second pressure value.

### Claim 12 (depends on 11)

The method of claim 11, wherein the correction factor is a first constant for all measured pressures that are less than or equal to the first pressure value and the correction factor is a second constant for all measured pressures that are greater than or equal to the second pressure value.

### Claim 13 (depends on 1)

The method of claim 1, wherein the correction factor has a first value if the measured pressure is less than or equal to a first pressure value and the correction factor has a second value if the measured pressure is greater than or equal to a second pressure value.

### Claim 14 (depends on 13)

The method of claim 13, wherein the correction factor has a third value if the measured pressure is greater than the first pressure value and less than the second pressure value.

### Claim 15 (depends on 13)

The method of claim 13, wherein the correction factor has the first value for all measured pressures less than or equal to the first pressure value, the first value being a constant.

### Claim 16 (depends on 13)

The method of claim 13, wherein the correction factor has the second value for all measured pressures greater than or equal to the second pressure value, the second value being a constant.

### Claim 17 (depends on 1)

The method of claim 1, wherein the medical fluid cassette is a peritoneal dialysis fluid cassette and the medical fluid is a dialysis fluid.

### Claim 18 (depends on 17)

The method of claim 17, wherein the dialysis fluid is pumped out of the chamber and delivered to a peritoneal cavity of a patient.

### Claim 19 (depends on 17)

The method of claim 17, wherein the dialysis fluid is drawn into the chamber from a peritoneal cavity of a patient.