Blood Treatment Filter Design to Trap Entrained Gas in a Blood Circuit
A configuration of a blood microtubular filter/dializer used in many kinds of renal replacement therapy systems can provide highly a effective mechanism for removing air from the blood circuit of such systems. In embodiments, for example, the invention takes advantage of the slow flow rate that usually occurs where blood exits the microtubules into a header area of the filter to provide a settling area.
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One of the problems with fluid circuits in blood treatment systems is entrained air (bubbles) in treatment fluids, infusate, or blood. Treatment systems normally have air detectors to prevent air from being injected into a patient, either because a venous line carrying blood back to the patient contains air or because an infusate line, such as the replacement fluid line of a hemofiltration system, contains air. It is desirable for the air detectors to be made sufficiently sensitive to prevent the rare instances of long trains of air bubbles being injected into a patient. But sensitivity high enough to prevent long thin trains of bubbles may be high enough to alarm very small amounts of air which pose no risk. In other words, sensitive air detectors alarm on a lot of fall positives if they protect against all possible risks.
A prior art approach has been to remove as much air from a protected fluid circuit as possible. Putting air traps in fluid circuits, particularly blood lines, has drawbacks. Air-settling chambers necessarily involve stagnant flow, which creates a risk of forming clots (e.g., for blood) or sedimentation or other concentration of entrained material (e.g. medication).
The inventive embodiments provide various other features and advantages in addition to or in lieu of those discussed above and below. Many of these features and advantages are apparent from the description below with reference to the following drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
The orientation of the filter 100 with respect to the pull of gravity is shown with the understanding that gravity is assumed to pull down with respect to the profile orientation of the drawing page. If any air is entrained in the blood, it may settle in pockets 151 and 153 in the arterial 160 and venous 155 head spaces as indicated by air/liquid interfaces 152 and 150. The flow of blood through the arterial 160 and venous 155 head spaces is extremely slow due to the very small cross-sectional areas of the filter fibers in the bundle 132. As a result, the arterial 160 and venous 155 head spaces are an idea place for air to settle out. With the indicated orientation, with blood outlet 124 pointing down and away from the pocket 151. Since the blood moves at a very slow rate in the arterial 160 and venous 155 head spaces, there is little risk of reentrainment and air settles out very effectively.
Air trapped in pocket 153 may travel through filter fibers in bundle 132 up to venous head space 155 and accumulate in pocket 151. Since the pocket 153 is located near the top of the arterial head space 160, air will tend to travel up a few of the fibers closest to the top and collect in the pocket 151 without mixing in with blood. This keeps the vast majority of fibers filled with blood.
Note that besides using the multi-way valve and bag 365 to draw air from the header of a filter and inject medicaments into the filter header, the same devices may be used in connection with an air trap or drip chamber. Referring to
Referring to
The filter fiber membrane bundle 420 may be inserted such that the fibers 415 extend beyond the end 407 of the tube 405 as indicated at 445. Referring now to
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A tension band 757 may be used to ensure a good seal and provide a final shape to the one-piece cap 725 if made of a somewhat compliant resin to allow it to be removed from an injection mold despite the recess defined by the dialysate manifold 740. Alternatively, the one-piece cap 725 may have a discontinuous dialysate manifold that allows it to be created without requiring the cap to yield, the cap could be machined rather than molded, or the cap could be made of two molded pieces that are assembled into a single cap. Many variations are possible.
It will be understood that while the invention has been described above in conjunction with a few exemplary embodiments, the description and examples are intended to illustrate and not limit the scope of the invention. That which is described herein with respect to the exemplary embodiments can be applied to the measurement of many different formation characteristics. Thus, the scope of the invention should only be limited by the following claims.
Claims
1. A blood treatment apparatus, comprising:
- a blood purifier including microtubular filter membranes in a bundle with one end of said bundle terminating in a first manifold at a lower end of said blood purifier and a second end of said bundle terminating in a second manifold, blood flowing in an upward direction through said filter media during use;
- said purifier having first and second header chambers forming respective passages where flow divides and coalesces in said first and second manifolds, respectively;
- said second header having an outlet where a coalesced flow from said second manifold flows out of said second header;
- said purifier being of generally cylindrical construction with a longitudinal axis parallel to said microtubular membranes;
- a holder configured to hold said purifier in a preferred orientation in which said longitudinal axis forms an angle with respect to a direction of gravitation force and with said outlet at a position remote from a highest point of said second header resulting from said orientation, whereby any gas bubbles in blood in said second header tend to rise and be trapped at said highest point and not flow out said outlet;
- said holder and a body of said purifier having mechanical features that prevent engagement of said purifier in said holder unless said purifier is in said preferred orientation with respect to said holder, thereby ensuring said purifier is used in said preferred orientation;
- said holder being fixedly mountable on a blood processing machine or some other base of reference in a fixed orientation.
2. An apparatus as in claim 1, wherein said holder is fixedly mounted on a blood processing machine.
3. A blood treatment apparatus, comprising:
- a blood purifier including filter media into which blood comes in contact during use;
- said purifier having a header chamber where multiple flows of blood combine at a position where blood exits a portion of said blood purifier, said header chamber having at least one outlet;
- a holder configured to support said purifier in a position and orientation such that air can accumulate in said header chamber in a position remote from said outlet whereby said header chamber is enabled to remove air from blood.
4. Apparatus as in claim 3, wherein said blood purifier includes microtubular blood purifier fibers and is attached to a fluid circuit and forms a part of a disposable set.
5. Apparatus as in claim 3, wherein said holder and said purifier are configured to permit said purifier to be attached in only one orientation, whereby a preferred orientation of said purifier is ensured.
6. Apparatus as in claim 3, wherein said holder is fixedly attachable to a blood treatment machine.
7. Apparatus as in claim 3, wherein said blood purifier has a longitudinal axis and said holder is configured to support said blood purifier with said longitudinal axis at an angle with respect to the vertical, as defined with respect to the force of gravity.
8. A blood treatment apparatus, comprising:
- a blood dialyzer or hemofilter processing element including filter media into which blood comes in contact during use;
- said processing element having a chamber at an exit of a treatment portion thereof where blood flow velocity drops to a low rate, said chamber having at least one outlet;
- a holder attachable to a blood treatment machine and configurable to support said processing element in a position and orientation such that air can accumulate in said header chamber in a position remote from said outlet whereby said header chamber is enabled to remove air from blood.
9. Apparatus as in claim 8, wherein said processing element is attached to a fluid circuit and forms a part of a disposable set.
10. Apparatus as in claim 8, wherein said processing element is attached to a fluid circuit and forms a part of a disposable set, said fluid circuit having a support with said holder thereattached such that when said fluid circuit is connected to said blood treatment machine, said processing element is so positioned oriented.
11. Apparatus as in claim 8, wherein said blood purifier has a longitudinal axis and said holder is configured to support said blood purifier with said longitudinal axis at an angle with respect to the vertical, as defined with respect to the force of gravity.
12. Apparatus as in claim 8, wherein said holder and said processing element are configured to permit said processing element to be attached in only one orientation, whereby a preferred orientation of said processing element is ensured.
13. A blood treatment apparatus, comprising
- a blood treatment device that includes a tubular media fiber bundle;
- a header having a header space connecting as a manifold outlets of said tubular media such that blood flowing therethrough coalesces into a single flow in said header that exits through an outlet of said header;
- said header having a blood outlet;
- a holder configured to support said blood treatment device in one position and orientation with respect thereto;
- said holder being configurable to connect to a blood treatment machine such that said blood treatment device is oriented with respect to said blood treatment machine;
- said header being shaped permit air to collect therein in a location above outlet, whereby gases coming out of solution in said tubular media collect in the slow moving header space and are not reentrained in an exiting blood flow.
14. Apparatus as in claim 13, wherein said blood treatment device has a longitudinal axis and said holder, when said fluid circuit is connected to said blood treatment machine is configured to support said blood treatment device with said longitudinal axis at an angle with respect to the vertical, as defined with respect to the force of gravity.
Type: Application
Filed: Oct 27, 2005
Publication Date: May 4, 2006
Applicant: NXSTAGE MEDICAL, INC. (LAWRENCE, MA)
Inventor: James BRUGGER (Newburyport, MA)
Application Number: 11/163,702
International Classification: B01D 63/04 (20060101);