Medical fluid air bubble detection apparatus and method

1. A medical fluid air detection apparatus comprising:

an emitter;

a receiver;

a housing configured to hold at least a portion of a medical fluid conduit between the emitter and the receiver; and

wherein the medical fluid conduit includes a narrowed inner diameter at the medical fluid conduit portion that forces flow of medical fluid through the narrowed diameter, the narrowed diameter configured to enhance the ability of the emitter and the receiver to detect air bubbles having a diameter of less than one millimeter, the conduit at the portion including an obstruction that increases a wall thickness of the conduit to produce the narrowed inner diameter.

2. The medical fluid air detection apparatus of claim 1 , wherein the obstruction is press-fit or interference fit within the medical fluid conduit.

3. The medical fluid air detection apparatus of claim 1 , wherein the medical fluid conduit is a tube, the obstruction wedged into the tube at the portion of the medical fluid conduit.

4. The medical fluid air detection apparatus of claim 1 , wherein the obstruction includes an inner diameter that is at least 50 percent less than an inner diameter of the medical fluid conduit.

5. The medical fluid air detection apparatus of claim 1 , wherein the obstruction has a cross-sectional area that consumes at least 75 percent of a cross-sectional area of the portion of the medical fluid conduit.

6. The medical fluid air detection apparatus of claim 1 , wherein the emitter and receiver operate acoustically.

7. The medical fluid air detection apparatus of claim 1 , wherein the housing is one of: (i) configured to be attached to a dialysis instrument; (ii) a housing of a dialysis instrument; and (iii) a stand-alone housing.

8. The medical fluid air detection apparatus of claim 1 , wherein the housing includes a retainer that grasps the medical fluid conduit.

9. The medical fluid air detection apparatus of claim 1 , wherein the portion of the medical fluid conduit includes at least one end configured to seal to a flexible tube.

10. The medical fluid air detection apparatus of claim 1 , wherein the portion of the medical fluid conduit is a portion of a medical fluid pumping cassette, the conduit a to-patient conduit extending from the pumping cassette.

11. The medical fluid air detection apparatus of claim 1 , wherein the conduit is a first conduit, the emitter and receiver are a first emitter and a first receiver, and which includes a second conduit, second emitter and second receiver, the second conduit including a narrowed inner diameter configured to force medical fluid to flow through the narrowed inner diameter at a portion of the conduit operating with the second emitter and the second receiver.

12. The medical fluid air detection apparatus of claim 11 , wherein the first conduit is a medical fluid supply conduit and the second conduit is a to-patient conduit.

13. A medical fluid air detection apparatus comprising:

an air detection sensor;

a medical fluid conduit including a narrowed inner diameter configured to (i) force medical fluid to flow through the narrowed inner diameter at a portion of the conduit operating with the sensor, and (ii) enhance the ability of the sensor to detect air bubbles having a diameter of less than one millimeter;

an internal obstruction located at the portion of the narrowed diameter, and increasing a wall thickness of the conduit to produce the narrowed inner diameter, the obstruction including an inner diameter that is at least 50 percent less than an inner diameter of the medical fluid conduit.

14. The medical fluid air detection apparatus of claim 13 , wherein at least one of: (i) the sensor is an acoustical sensor; (ii) the sensor includes an emitter and a receiver; and (iii) the apparatus includes a housing configured to hold the medical fluid conduit adjacent to the sensor.

15. The medical fluid air detection apparatus of claim 13 , wherein the internal obstruction is press-fit or interference fit within the medical fluid conduit.

16. A medical fluid air separation method comprising:

forcing a medical fluid to flow within a narrowed portion of a medical fluid conduit;

detecting air bubbles within the medical fluid flowing through the narrowed portion, the narrowed portion enhancing the ability of the sensor to detect air bubbles having a diameter of less than one millimeter within the medical fluid flowing through the narrowed portion; and

contacting an internal surface of the medical fluid conduit with a smaller diameter conduit to increase a wall thickness of the medical fluid conduit and to create the narrowed portion, the smaller diameter conduit being at least 50 percent less than an inner diameter of the medical fluid conduit.

17. The medical fluid air separation method of claim 16 , wherein the internal surface of the medical fluid conduit is a tubing surface or a cassette fluid path surface.

18. The medical fluid air separation method of claim 16 , which includes press-fitting or interference fitting the smaller diameter conduit within the medical fluid conduit to create the narrowed portion.

19. A medical fluid air detection apparatus comprising:

an emitter;

a receiver;

a housing configured to hold at least a portion of a medical fluid conduit between the emitter and the receiver, the portion of the medical fluid conduit is a medical fluid conduit residing within a medical fluid pumping cassette, the housing a housing of a dialysis instrument configured to accept the cassette; and

wherein the medical fluid conduit includes a narrowed inner diameter at the medical fluid conduit portion that forces flow of medical fluid through the narrowed diameter, the narrowed inner diameter configured to enhance operation of the emitter and the receiver, the conduit at the portion including an internal obstruction press-fit or interference fit into the conduit that increases a wall thickness of the conduit to produce the narrowed inner diameter.