Blood filter

• US 4,572,724 A
• Filed: 04/12/1984
• Issued: 02/25/1986
• Est. Priority Date: 04/12/1984
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: Pall Corporation (Danaher Corporation)
• Inventors: Matkovich, Vlado I., Rosenberg, David J.
• Primary Examiner(s): Hart, Charles
• Application Number:
  US06/599,585
• Time in Patent Office: 684 Days
• Field of Search: 55/159, 55/185, 55/186, 55/187, 55/318, 55/204, 55/178, 128/DIG. 3, 210/321.4, 210/436, 210/472, 210/927, 210/512.1, 604/4, 604/5, 604/122, 604/126
• US Class Current: 96/6
• CPC Class Codes: A61M 1/325 Surfactant coating; Improving wettability
• CPC Class Codes: A61M 1/3627 Degassing devices; Buffer reservoirs; Drip chambers; Blood filters
• CPC Class Codes: A61M 1/3643 Priming, rinsing before or after use
• CPC Class Codes: A61M 2205/7536 allowing gas passage, but preventing liquid passage, e.g. liquophobic, hydrophobic, water-repellent membranes
• CPC Class Codes: A61M 2206/16 Rotating swirling helical flow, e.g. by tangential inflows
• CPC Class Codes: Y10S 128/03 Heart-lung

Abstract

A blood filter such as may be used in a cordiopulmonary bypass system includes a housing having upper and lower chambers with a cylindrical filter element disposed in the lower chamber. The inlet to the housing is in the upper chamber, which is upstream of the lower chamber, and the outlet is through the lower chamber and communicates with the interior of the filter element. Thus, blood enters the upper chamber and flows to the lower chamber where it passes through the filter element from the outer side to the interior to remove microemboli such as gas bubbles, fat emboli and agglomerates, the filtered blood exiting through the outlet. In order to remove a substantial amount of the gas in the blood, and particularly gross bubbles, upstream of the filter element, the upper chamber is cylindrical and the inlet directs the blood tangentially to flow around the periphery of the chamber. An annular baffle extending around a major portion of the chamber maintains the peripheral flow which produces a centrifugal action causing the blood to flow at the wall of the chamber and the gas to separate and move to the central portion where it is vented through a hydrophobic membrane covering the central portion of the top wall of the chamber. Blood from the periphery of the upper chamber flows down to the lower chamber through a sponge ring which removes additional gas bubbles by causing the latter to coalesce into larger bubbles which move radially inwardly of the ring and rise to the upper chamber where they also are vented through the membrane. Any gas bubbles which remain in the blood and which are larger than the acceptable size are blocked by the filter element. The bubbles at the filter element eventually coalesce into larger bubbles which break away from the filter element and rise to the upper chamber where they are vented through the membrane.

Claims

1. Apparatus for separating gas from blood before the blood passes through a filter, said apparatus comprising a housing defining a cylindrical chamber having top and bottom walls and a cylindrical side wall, said bottom wall having an annular opening extending generally around the periphery of said chamber and adapted to communicate with a filter, an annular baffle disposed in said chamber concentrically with said side wall and depending from said top wall to define an annular channel overlying said opening, an inlet communicating with said channel through said side wall and disposed to direct blood into the channel tangentially of the side wall whereby the blood flows in a generally circular path in the channel and generally downwardly out of said chamber through said opening, said circular flow producing a centrifugal action which causes the blood to flow at the outer periphery of said channel while gas entrained in the blood separates and moves inwardly, said baffle having an opening at a point where the baffle has defined a substantial part of a circle beginning near said inlet to permit the gas to enter the center portion of the chamber inside the baffle only after the blood has travelled a substantially full circle, at least one vent opening in the center portion of said top wall to permit gas in the center portion of said chamber to escape from the housing, and a hydrophobic membrane in said top wall covering said vent opening and extending over a substantial part of said center portion of said chamber to permit the automatic flow of gas but not blood out through said vent opening.

2. Apparatus as defined in claim 1 including a plurality of vanes depending from said top wall beneath said membrane to impede the circular flow of the gas in said center portion of said chamber and facilitate the flow of gas through the membrane.

3. Apparatus as defined in claim 2 in which said vanes extend generally radially from the center of said chamber toward said baffle and are generally equally spaced angularly around the chamber.

4. The apparatus of claim 1 which further comprises an annulus of sponge material including means for breaking the film between adjacent bubbles, said sponge material being disposed generally beneath said annular channel whereby at least some of the blood flowing in said annular chamber contacts said sponge material as the blood flows around said annular channel.

5. The apparatus of claim 4 wherein said baffle and sponge are arranged to assure at least some of the blood passes through the sponge in flowing generally downwardly out of said chamber.

6. A blood filter having, in combination, a housing having top, bottom and side walls and defining upper and lower chambers, at least said upper chamber being cylindrical, a cylindrical filter element disposed in said lower chamber and having a hollow interior, an outlet formed in said housing and communicating with the interior of said filter element, the outer surface of said filter element being spaced from the side wall of said housing to define an annular space surrounding the filter element, means closing the top of said filter element whereby blood from said upper chamber enters said annular space and flows through the filter element from the outside to the interior and out through said outlet, an inlet communicating with said upper chamber through the side wall of said housing and disposed to direct the blood generally tangentially of the upper chamber, an annular baffle disposed in said upper chamber concentrically with said side wall and depending from said top wall to define an annular channel for guiding blood which enters said upper chamber along a generally circular path at the periphery of the upper chamber, said circular flow producing a centrifugal action which causes the blood to flow to the periphery of the upper chamber and then to said annular space while gas entrained in the blood separates and moves inwardly, said baffle having an opening at a point where the baffle has defined a substantial part of a circle beginning near said inlet to permit the gas to enter to the center portion of the upper chamber inside the baffle only after the blood has travelled a substantially full circle, at least one vent opening in the center portion of said top wall to permit the gas in the center portion of said chamber to escape from said housing, and a hydrophobic membrane in said top wall covering said vent opening and extending substantially over said center portion of said upper chamber to permit the automatic flow of gas but not blood out through said vent opening.

7. A blood filter as defined in claim 6 including a plurality of vanes depending from said top wall beneath said membrane to impede the circular flow of the gas in said center portion of said upper chamber and facilitate the flow of gas through the membrane.

8. A blood filter as defined in claim 7 in which said vanes extend generally radially from the center of said upper chamber toward said baffle and are generally equally spaced around the chamber.

9. A blood filter as defined in claim 8 including a ring encircling and rigid with the outer ends of said vanes, said ring being rigidly secured to said top wall and said membrane being clamped between the ring and the top wall.

10. The apparatus of claim 6 which further comprises an annulus of sponge material including means for breaking the film between adjacent bubbles, said sponge material being disposed generally beneath said annular channel whereby at least some of the blood flowing in said annular chamber contacts said sponge material as the blood flows around said annular channel.

11. The apparatus of claim 10 wherein the baffle and sponge are arranged to assure at least some of the blood passes through the sponge in flowing generally downwardly out of said chamber.

12. Apparatus for separating gas from blood, said apparatus comprising, a housing defining a first cylindrical chamber having top and bottom walls and a cylindrical side wall, said bottom wall having an annular opening extending around the periphery of said chamber, an annular baffle disposed in said chamber concentrically with said side wall to define an annular channel overlying said opening, an inlet communicating with said channel through said side wall and disposed to direct blood into the channel tangentially of the side wall whereby the blood flows in a generally circular path in the channel and then out of said chamber through said opening, said circular flow producing a centrifugal action which causes the blood to flow at the outer periphery of said channel while gas entrained in the blood separates and moves inwardly, said baffle having an opening to permit the gas to enter the center portion of the chamber inside the baffle, venting means in the center portion of said top wall to permit gas in the center portion of said chamber to escape from the housing, a hydrophobic membrane in said top wall covering said venting means and extending substantially over said center portion of said chamber to permit the flow of gas out through said venting means, said housing defining a second cylindrical chamber coaxial with and disposed beneath said first chamber, a cylindrical filter element disposed in said second chamber coaxially therewith and having a hollow interior, an outlet formed in said housing and communicating with the interior of said filter element, the outer surface of said filter element being spaced from the outside of said second chamber to define an annular space alined and communicating with said annular channel, an annulus of sponge material disposed in the upper end portion of said annular space and extending around the periphery of said second chamber whereby blood flows from the channel through the sponge annulus to said space and hence to said filter element, said sponge annulus including means for causing gas bubbles in the blood to coalesce and form larger gas bubbles as the blood flows through said sponge annulus, and a ring holding said sponge annulus radially spaced outwardly from said filter element to define an annular passage whereby said larger gas bubbles exit said sponge annulus and move through said passage to said center portion of said first chamber where they are vented through said membrane.

13. Apparatus as defined in claim 12 in which said ring is perforated whereby blood and said larger bubbles flow out of said sponge annulus through the perforations in the ring and into said annular passage.

14. A blood filter having, in combination, a housing having top, bottom and side walls and defining upper and lower cylindrical chambers, a cylindrical filter element disposed in said lower chamber and having a hollow interior, an outlet formed in said bottom wall and communicating with the interior of said filter element, the outer surface of said filter element being spaced from the side wall of said housing to define an annular space surrounding the filter element, means closing the top of said filter element whereby blood from said upper chamber enters said annular space and flows through the filter element from the outside to the interior and out through said outlet, an annulus of sponge material disposed in the upper end of said annular space and extending around the periphery of said housing, means in said upper chamber for directing blood to said sponge annulus whereby the blood flows through the latter to said annular space, said sponge annulus including means for causing gas bubbles in the blood to coalesce and form larger gas bubbles as the blood flows through said sponge annulus, means forming an annular passage between said sponge annulus and said filter element whereby said large gas bubbles exit the sponge annulus and move through said annular passage to said upper chamber, and means permitting gas in said upper chamber to be vented to atmosphere.

15. A blood filter as defined in claim 14 which said means for forming said annular passage is a ring encircling said filter element and radially spaced from the latter whereby the ring and the filter element define the annular passage and said sponge annulus is disposed between the ring and the side wall of said housing.

16. A blood filter as defined in claim 15 in which said ring is perforated whereby blood and said larger gas bubbles flow out of said sponge annulus through the perforations in the ring and into said annular passage.

17. A blood filter as defined in claim 16 in which said means for causing the blood to coalesce is a compound of silicone and silica with the silicone capturing smaller gas bubbles in said sponge annulus and said silica causing the film between adjacent bubbles to break and form larger bubbles.