Non-invasive radio frequency medical fluid level and volume detection system and method

Patent metadata

Field	Value
Publication number	US-9907908-B2
Application number	US-201113253691-A
Country	US
Kind code	B2
Filing date	Oct 5, 2011
Priority date	Mar 8, 2011
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A medical fluid system includes a medical fluid pump; a container holding a fluid to be pumped by the medical fluid pump, the fluid at a first time having a first conductivity, the fluid at a second time having a second conductivity; and a radio frequency level sensor positioned in operable relation with the container, the radio frequency level sensor (i) configured to provide an output indicative of a level of the fluid in the container based upon sensing an impedance and (ii) connected to tuning circuitry that minimizes a reactance of the impedance such that the output is at least substantially independent of whether the fluid has the first conductivity or the second conductivity. The medical fluid system can determine the level of the fluid by measuring a resistance, the impedance, or a phase shift seen by the sensor.

First claim

The invention is claimed as follows:

1. A medical fluid system comprising:
a container holding a fluid, the fluid at a first time having a first conductivity, the fluid at a second time having a second conductivity; and
a radio frequency level sensor positioned in operable relation with the container, the radio frequency level sensor (i) configured to provide an output indicative of a level or a volume of the fluid in the container based upon sensing an impedance that varies with the level or the volume of the fluid in the container and (ii) connected to tuning circuitry including a plurality of components tuned to an operating frequency to minimize a reactance of the impedance at the operating frequency such that the output is at least substantially independent of whether the fluid has the first conductivity or the second conductivity.

2. The medical fluid system of claim 1 , which is a dialysis system, and wherein the container is (i) a dialysate supply container or (ii) a dialysate holding container in fluid communication with a supply of dialysate.

3. The medical fluid system of claim 1 , which is a dialysis system, the fluid being water at the first time and dialysate at the second time.

4. The medical fluid system of claim 1 , wherein the radio frequency level sensor is fixed to the container.

5. The medical fluid system of claim 1 , wherein the radio frequency level sensor is spaced apart from the container.

6. The medical fluid system of claim 1 , which is configured and arranged to mix different constituents of the fluid resulting in the first and second conductivities at the first and second times.

7. The medical fluid system of claim 1 , wherein the radio frequency level sensor includes a radio frequency signal emitting electrode spaced adjacent to a radio frequency signal receiving electrode.

8. The medical fluid system of claim 7 , wherein the emitting electrode and the receiving electrode are at least one of: (i) sized so as to form a characteristic impedance and (ii) sized the same.

9. The medical fluid system of claim 1 , which includes a processor operable with the level sensor, the sensor outputting a signal indicative of the impedance to the processor.

10. The medical fluid system of claim 9 , wherein the processor is configured to provide a radio frequency input to the sensor.

11. The medical fluid system of claim 9 , wherein the processor is configured to operate with stored data relating the signal or a variant thereof to one of (i) the level of the fluid in the container or (ii) the volume of the fluid in the container.

12. The medical fluid system of claim 1 , wherein each of the plurality of components is tuned during a calibration.

13. The medical fluid system of claim 1 , wherein the plurality of components includes at least one capacitor and at least one inductor.

14. The medical fluid system of claim 1 , wherein the reactance is driven to zero at the operating frequency by the tuning circuitry.

15. The medical fluid system of claim 1 , wherein the operating frequency is in a range from 1 GHz to 2 GHz.

16. The medical fluid system of claim 1 , wherein each component of the plurality of components has (i) a first respective value that drives the reactance to zero at a first operating frequency, and (ii) a second respective value that drives the reactance to zero at a second, different operating frequency.

17. The medical fluid system of claim 1 , which includes an oscillator configured to generate a radio frequency signal at the operating frequency.

18. A medical fluid system comprising:
a medical fluid pump;
a container in fluid communication with the medical fluid pump, the container at a first time holding a first fluid having a first conductivity, the container at a second time holding a second fluid having a second conductivity; and
a radio frequency level sensor positioned in operable relation with the container, the radio frequency level sensor (i) configured to provide an output indicative of a level or a volume of the first or second fluid in the container based upon sensing an impedance that varies with the level or the volume of the first or second fluid in the container and (ii) connected to tuning circuitry including a plurality of components tuned to an operating frequency to minimize a reactance of the impedance at the operating frequency such that the output is at least substantially independent of the first and second conductivities.

19. The medical fluid system of claim 18 , which is a dialysis system, the first fluid being water and the second fluid being dialysate.

20. The medical fluid system of claim 18 , which is an intravenous drug infusion system, the first fluid being a first drug and the second fluid being a second drug.

21. The medical fluid system of claim 18 , which is an intravenous drug infusion system, the first fluid being a first drug constituent and the second fluid being a second drug constituent.

22. The medical fluid system of claim 18 , which is a peritoneal dialysis system, the first fluid being a first peritoneal dialysate and the second fluid being a second peritoneal dialysate.

23. The medical fluid system of claim 18 , which is a peritoneal dialysis system, the first fluid being a first peritoneal dialysis fluid constituent and the second fluid being a second peritoneal dialysis constituent.

24. A medical fluid system comprising:
a medical fluid pump;
a container holding a fluid to be pumped by the medical fluid pump; and
a radio frequency sensor operable with the container, the sensor including an emitting electrode and a receiving electrode positioned such that a radio frequency transmission between the emitting electrode and the receiving electrode is affected by an amount of air in the container having a dielectric constant ∈ o and an amount of the fluid in the container having a dielectric constant ∈ d , the container at a first time holding a first fluid and at a second time holding a second fluid having a different conductivity than the first fluid, the first and second fluids having at least substantially the same dielectric constant ∈ d , the sensor outputting an impedance signal indicative of an equivalent dielectric constant E, which is indicative of a fluid level of the container, the equivalent dielectric constant E based on the dielectric constants ∈ o and ∈ d , and the sensor connected to tuning circuitry including a plurality of components tuned to an operating frequency to minimize a reactance of an impedance at the operating frequency such that the impedance signal is at least substantially independent of the conductivities of the first and second fluids.

25. The system of claim 24 , wherein the equivalent dielectric constant is

ɛ
=

ɛ
⁢

⁢
o

+

ɛ
⁢

⁢
d

2

.

Assignees

• Chen Ye
• Ding Yuanpang Samuel
• Muller Matthew
• Najdeni Gert
• Titus Joel
• Baxter Int
• Baxter Healthcare Sa

Inventors

• Chen Ye
• Ding Yuanpang Samuel
• Muller Matthew
• Najdeni Gert
• Titus Joel

Classifications

• G01F23/263

  by measuring variations in capacitance of capacitors · CPC title

• A61M1/28

  Peritoneal dialysis {; Other peritoneal treatment, e.g. oxygenation} · CPC title

• A61M1/1605

  Physical characteristics of the dialysate fluid · CPC title

• A61M5/1407

  Infusion of two or more substances · CPC title

• A61M2205/52

  with memories providing a history of measured variating parameters of apparatus or patient · CPC title