Oxygenator

Abstract

An oxygenator primarily for human blood has a stator with a cavity partly defined by a first substantially flat wall and a peripheral wall and has a rotor with a second substantially flat wall facing the first wall. On their facing sides both walls have supports highly permeable to gas. Both supports are covered by gas-permeable, hydrophobic membranes between them defining a passage for liquid extending from near the center of the cavity to near the peripheral wall. Gas is conducted through the supports and membranes on the stator and on the rotor. Blood is supplied through the stator to the cavity near the center thereof and, without an external pump, is impelled to flow through the passage and out an outlet in the peripheral wall, the membranes having irregularities or vanes acting as centrifugal impellers.

Description

In U.S. Pat. No. 3,674,440 for an "Oxygenator" issued to one of us (Kitrilakis) on July 4, 1972 there is disclosed in considerable detail an arrangement for transferring oxygen to blood. The device is substantially pressure balanced so far as blood inflow and outflow are concerned and in use requires the blood to be impelled through it by some sort of external pump. It has developed in practice that it would be highly desirable to afford a comparably effective and efficient oxygenator but which could function without the necessity of an external blood pump.

It is therefore an object of the invention to provide an oxygenator that contains within itself a way of circulating blood through it.

Another object of the invention is to provide an oxygenator having the attributes of the oxygenator in the mentioned patent but which does not require an external blood pump.

Another object of the invention is to provide a generally improved oxygenator.

Other objects, together with foregoing, are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is a cross-section on a diametrical plane through an oxygenator constructed pursuant to the invention;

FIG. 2 is a detailed cross-section to an enlarged scale through one of the wall, support and membrane assemblies; and

FIG. 3 is a cross-section, the plane of which is indicated by the line 3--3 of FIG. 2.

Reference is had to the above-identified patent for many details of construction of the present oxygenator since they are identical in many particulars. In the present instance the oxygenator includes a stator 4 forming a housing made up of a pair of cover plates 6 and 7 of generally similar construction and fastened together around their peripheries by spaced fasteners 8 and clamping between them a plurality of separate layers to form, in effect, a sandwich. The stator housing encloses an interior cavity defined largely by one side wall 9, a second side wall 11 and a peripheral wall 12 made up by the sandwich members.

Designed to operate within the stator is a rotor 16 having a shaft 17 provided with a pulley 18 or other means for connecting the rotor to a motor for turning the rotor on bearings 19 and 21 in the stator and for rotation about a central axis 22. The rotor includes not only an enlarged portion 23 of the shaft 17 but likewise includes a central disc 24 bounded by a rotor wall 26 on one side and by a rotor wall 27 on the other side.

As in the mentioned patent, most of the interior stator and rotor walls are covered by special devices for assisting in the oxygenation of the blood and for blood flow. On the wall 9, for example, there is a support wafer 28 typical of others in the device. This is a ruffled or corrugated sheet of material affording mechanical support yet being permeable in virtually all directions to gas, such as oxygen. As an alternate, the wafers can be mounds or ridges integral with the material of the rotor and stator. An appropriate support wafer 29 is disposed on the other stator wall 11. Comparable support wafers 31 and 32 are situated against the walls 26 and 27 of the rotor.

Each support wafer, however formed, is covered with a membrane, such as 33, having little ability to support itself but being supported in substantially a planar form by resting against the adjacent support wafer. The membrane is on the opposite side of the wafer from the adjacent rotor or stator wall. The membranes are highly permeable to gases but are not readily permeable to liquid which contacts the membrane. A comparable membrane 34 is arranged adjacent the wafer 29 while membranes 36 and 37 lie adjacent the wafers 31 and 32. Conveniently, some of these various parts are relatively thin layers which go to make up the sandwich referred to. In the instance of the rotor, the parts are secured together for conjoint rotation about the axis 22 by reason of a plurality of through bolts 38 passing through the various parts of the rotor and clamping them together.

In order to supply gas, such as oxygen, to the interior of the mechanism the stator is provided with a branched inlet opening 41. One portion of the opening connects with a duct 42 leading into proximity with the support wafer 28 so that gas in the duct 42 can travel into and through the wafer or around the axis and eventually can flow through any of a number of passages 43 formed in the stator. The passages 43 communicate with the wafer 29 so that there can be gas flow through all parts thereof. Escape of gas from the wafer 29 is through a passage 44 in the lower portion of the stator. Flow is from there to any suitable point of disposition.

The inlet opening 41 also is connected to a duct 46 leading into an annular chamber 47 between the stator and the rotor and confined by sealing rings 48 and 49. From the compartment 47 gas flow is through an opening 51 leading into an upper chamber 52 defined by the hollow interior of the drive shaft. The chamber 52 is isolated from a lower chamber 53, also formed in the drive shaft, by the solid intervening rotor disc 24.

Gas from the inlet 41 flows through the duct 46 into the confined chamber 47, thence through the opening 51 into the upper chamber 52. From thence the gas flows into and through all parts of the rotor wafer 31 on one side of the rotor plate 24 and then flows through any one of several openings 54 in the rotor disc to the wafer 32. The gas permeates throughout that wafer and then travels into the lower chamber 53 in the rotor for discharge to any suitable point.

Most of the gas which is supplied to the wafers diffuses through the adjacent membranes and into a passage 56 disposed between and defined by the outer surface of the rotor and the inner wall of the stator. The passage 56 is duplicated by a comparable passage 57 on the other side of the rotor, the two sides being connected by a peripheral passage 58 extending around the interior of the stator. Also, the passages 56 and 57 communicate with annular chambers 59 and 61 respectively extending around the rotor and within the stator. The chambers are confined between the packing ring 49 and a comparable packing ring 62.

Blood from a suitable source enters the stator through a passage 63 opening into the annular chamber 59. Blood in the chamber 59 can flow to the chamber 61 through any one of several openings 66 formed in each of the sandwich members making up the rotor. In addition, the stator periphery is provided with a discharge or outlet passage 67 opening to the passage 58. Blood flows into the annular chamber 59 and thence into the passage 56 and through the openings 66 into the passage 57 and then from such passages 56 and 57 through the outlet 67.

We have found that the membranes, such as 33, normally have sufficient superficial irregularities so that when the rotor is revolved about the axis 22, the irregularities act upon the blood in the passages 56 and 57 to exert a centrifugal force thereon. The force magnitude is great enough to induce blood to flow in through the entrance passage 63, through the passages 56 and 57 in a generally radial path and then out through the discharge opening 67 and into whatever connecting ducting may be secured thereto. Thus, blood is made to flow through the oxygenator without the necessity of utilizing an exterior circulating pump.

While the irregularities on the membranes are sufficient, as indicated, to induce flow by centrifugal action, it is sometimes the case that the flow needs to be accelerated or augmented. In such instance we provide a membrane 68 generally similar to the other membranes, such as 33 for example, as shown in FIG. 2. The membrane 68 has an integrally formed, special irregularity 69 in the form of an upstanding radial vane. Usually the membrane is of an elastomeric or plastic material that is readily molded so it is feasible to mold the radial vane 69 with the membrane. The vane 69 projects from the membrane into the adjacent passageway 56 or 57 and imparts an additional centrifugal acceleration to blood in the passageways. The result of the vanes is to augment the effect of the centrifugal force due to the rotating rotor and produces a very effective pumping of the blood, so that external pumps can be dispensed with.

The structure as described, particularly when the vanes are utilized, carries out all of the attributes of the earlier patented device as to the production of turbulent flow and the reduction in thickness of boundary layers in the blood. In fact, the transfer of oxygen to the blood in this structure has proved so efficient in practice that the oxygenator herein with a single rotor stage can accomplish substantially the same amount of oxygenation as the two-stage rotor shown in the patent and has the added attribute of dispensing with an external pump.

Claims

What is claimed is:

1. An oxygenator comprising a stator having a disc-like cavity defined by a pair of side walls and a peripheral wall; a shaft; means for journalling said shaft in said stator; a rotor on said shaft and having a rotor wall disposed in said cavity; first support means permeable to gas in substantially all directions and extending from said side walls; first membranes permeable to gas but not readily permeable to liquid in contact therewith and disposed against said support means on the side thereof opposite said side walls; second support means permeable to gas in substantially all directions and extending from said rotor wall on the side thereof toward said side wall; second membranes permeable to gas but not readily permeable to liquid in contact therewith and disposed against said second support means on the side thereof opposite said rotor wall and spaced from said first membranes to leave a passage therebetween extending from adjacent the center of said cavity to the periphery thereof; means in said stator for conducting gas into said stator, through said first support means and out of said stator; means in said rotor for conducting gas into said rotor, through said second support means and out of said rotor; inlet means in said stator for conducting liquid into said cavity and into said passage adjacent the center of said rotor; and outlet means in said peripheral wall for conducting liquid out of said cavity.

2. An oxygenator as in claim 1 including an irregularity on said second membranes effective to produce pumping of said liquid from said inlet means to said outlet means upon rotation of said rotor in said stator.

3. An oxygenator as in claim 2 in which said irregularity is a radial vane.