MXPA00010725A - Low prime membrane oxygenator with integrated heat exchanger/reservoir - Google Patents

Abstract

A low prime membrane oxygenator (150) and an integrated heat exchanger/reservoir (24, 40) for use alone or in combination in an extracorporeal blood circuit. The oxygenator has a simple, five-part construction including a housing (152) defining an annular oxygenation chamber (168) within which a plurality of hollow fibers (160) are arranged in an annular bundle with flow spaces therebetween.A blood inlet port and manifold deliver blood through a plurality of evenly circumferentially spaced inlet apertures to the oxygenation chamber, and blood flows generally axially through the elongated annular chamber to a plurality of evenly circumferentially spaced outlet apertures. Specific geometric ratios, a particular hollow fiber architecture, and the absence of a heat exchange function, all combine to reduce the prime volume required by the oxygenator. The reservoir (24, 40) includes heat exchange coils (88) in an annular chamber (86) providing efficient heat transfer with low prime volume.

Description

LOW PREPARATION VOLUME MEMBRANE OXYGENER WITH INTEGRATED DEPOSIT / HEAT EXCHANGER Field of the Invention The present invention relates generally to extracorporeal fluid circuits and, more particularly, to a compact membrane oxygenator and combined heat exchanger / reservoir used alone or in conjunction to reduce the volume of preparation or priming of a blood circuit.

Background of the Invention Cardiopulmonary bypass surgery (CPB) requires an infusion system, or extracorporeal oxygenation circuit, to maintain an adequate supply of oxygen in the patient's blood during surgery. A venous return cannula inserted into one of the veins that leads directly to the heart receives "used" blood for renewal through the perfusion system. Blood flows out of the patient into an extracorporeal fluid circuit that has a duct (typically a clear flexible tube) into a venous reservoir that also Ref.124510 can receive fluid from the suckers for cardiotomy. Commonly, one or more suckers extract excess fluid from the thoracic cavity during the operation and divert the fluid, which may contain bits of bone or other particulate materials, to the top of the reservoir. Typically, a centrifugal or roller pump drives the blood, for example, from the cardiotope / venous reservoir through a blood oxygenator and back to the patient. The pump assumes the task of pumping the heart and perfuses the patient's circulatory system. The oxygenator directs a flow of blood through a semipermeable membrane or a plurality of semipermeable fibers to transfer oxygen to, and carbon dioxide from, the blood. The oxygenator often incorporates a heat exchange system to regulate the extracorporeal blood temperature, called a "closed" system. Before reaching the patient, the blood can pass through a system of verification of temperature control and along a duct through an arterial filter and bubble detector, before reaching an arterial cannula placed in a main artery of the patient. The various components such as the reservoir, the oxygenator and the arterial filter require a minimum volume of blood to start circulation. All of the components taken together require a volume of "preparation or priming" of the blood defined as that volume of blood outside the patient, or extracorporeal. The term "priming or priming volume" can also be used to specify the volumetric capacity of each extracorporeal component in the system. There are several performance measurements of the oxygenators. Important considerations include gas transfer capabilities, priming volume, blood compatibility, sterility, assembly, and maintenance. Effective oxygenators provide sufficient gas transfer with minimum pressure drop and fatigue volume. In addition, the flow capacity through the oxygenator must be sufficient for the particular patient. Frequently, there is a trade-off in one or more of these operating characteristics to obtain a low priming volume or a high flow rate, for example. The need for a large fattening volume in an extracorporeal fluid circuit is contrary to the best interest of the patient who is undergoing surgery and has the need for the maximum possible amount of oxygenated blood completely. This is especially true for younger adults, children, and pediatric or pediatric patients. Therefore, a significant amount of research and development has been directed towards the reduction of the fattening volume within the CPB systems. An area in which such volume reduction can be achieved, is to reduce the volume of individual components, such as the reservoir, or the oxygenator of the blood. However, there are limits to how small these components can be made, such as the need for adequate transfer of oxygen to the blood, which depends in part on a sufficient interfacial area of the blood / membrane. Most of the development in recent years has been towards reducing the priming volume of the oxygenators while maintaining adequate capacities of flow velocity and gas transfer. Unfortunately, this is not a goal that can be easily achieved, and many of the smaller priming volume oxygenators have such a low flow velocity that they are only useful for neonatal or infant patients, or exhibit some other operating disadvantage. In contrast, many oxygenators which otherwise function properly, require a larger fattening volume. For example, most of the commercial membrane oxygenators most widely used in the market for adult patients have fattening volumes of between 0.3 and 0.6 liters. Given the limited supply of the patient's blood, any reduction in the volume of priming in the oxygenator or other components of the extracorporeal circuit greatly improves the chances of a positive surgery and rapid recovery. Despite the foregoing advances in extracorporeal circuit technology, there is an ever-present need for a reduced fattening volume CPB system.

Brief Description of the Invention The present invention provides an improved, low fattening body extracorporeal system including a low fattening volume oxygenator and a combined low heat volume heat exchanger / reservoir. The dimensions of the oxygenator are optimized so that, in conjunction with a particularly preferred hollow fiber architecture, a reduction in the priming volume results from currently available models as well as superior operation. Two sizes of oxygenator are described which have the ability to meet the needs of all patient weight ranges, from the smallest neonatal babies to the large adults. Oxygenators share certain dimensions and preferred elements, and essentially justify the difference in height. The combined heat exchanger / reservoir makes use of a one-step guided heat exchanger configuration that disengages the heat exchange efficiency of the reservoir blood level. In one embodiment, the low priming volume oxygenator comprises a rigid housing defining an annular oxygenation chamber having a first axial end and a second axial end. A plurality of hollow, elongated semipermeable fibers are arranged in an annular bundle or bundle in the oxygen chamber and secured at both axial ends with an encapsulation compound. The bundle or bundle substantially fills the oxygenation chamber with the fibers arranged to provide spaces for blood flow therebetween, and the opposite ends of the fibers are open to an upper space for the gas formed in the housing outside the chamber. oxygenation chamber. A central blood inlet opening is provided in communication with a blood distribution space adjacent an axial end of the oxygenation chamber. A plurality of blood inlets in the housing are formed around the annular oxygenation chamber in communication with the blood distribution space, while a plurality of blood outlets in the housing are formed around the oxygenation chamber annular on the opposite axial end-to the entrances of the blood. In an oxygenator mode suitable for adults, the oxygenator has a priming volume of between 130 and 180 ml and a ratio of the oxygen transfer rate to the fattening volume of at least about 0.34 bpm / min, at a flow rate of approximately 7 lpm. In a suitable oxygenator mode for neonates / infants, the oxygenator has a priming volume of between about 56 ml and 80 ml and an oxygen transfer rate of about 62.5 ml / min / lpm at a flow rate of about 2 lpm. The blood oxygenator of the present invention desirably has a simplified construction with a rigid housing consisting essentially of five parts, including: an inner core having a radial bottom wall and a cylindrical wall, a concentric outer cylindrical wall around the cylindrical wall of the inner core defining an annular oxygenation chamber therebetween having a first axial end and a second axial end, a pair of end caps connected to opposite ends of the outer cylindrical wall, and an inlet cover for the blood secured to the inner core. The inlet cap has a central blood inlet opening in communication with a blood distribution space adjacent an axial end of the oxygenation chamber and formed between the inner lid and the lower wall of the inner core. A plurality of inlets for blood in the inner core are formed around the blood distribution space in communication with the annular oxygenation chamber. The oxygenator includes a plurality of semipermeable fibers, hollow, elongated, in an annular bundle or bundle in the oxygenation chamber and secured at both axial ends with an encapsulation compound. The opposite ends of the fibers are open towards an upper space for the gas formed inside the end caps outside the oxygenation chamber. The bundle or bundle substantially fills the oxygenation chamber with the fibers having spaces for blood flow therebetween. A plurality of outlets for the blood in the outer cylindrical wall are formed around the annular oxygenation chamber on the axial end opposite the inlets for the blood generally causing an axial flow of blood through the oxygenation chamber and between the hollow fibers. The five parts of the oxygenator are either snapped together with 0-ring seals, or are bonded with adhesive or UV welding. The present invention also takes on body in an extracorporeal system, comprising a blood reservoir / combined exchanger and a hollow fiber oxygenator. The reservoir has heat exchange elements located in a separate heat exchange chamber and an outlet for blood. The oxygenator includes an inlet for the blood connected to the blood outlet of the blood reservoir / heat exchanger, and a rigid housing defining an annular oxygenation chamber having a cross-sectional area normal to its axis of between about 24 and 28 square centimeters. The oxygenation chamber has a first axial end and a second axial end, and the housing includes a central blood entry opening, in communication with a space for blood distribution adjacent an axial end of the oxygenation chamber . A plurality of blood inlets in the housing are formed around the annular oxygenation chamber in communication with the blood distribution space, while a plurality of the blood outlets in the housing are formed around the blood chamber. annular oxygenation on the axial end opposite the blood inlets. Finally, a plurality of hollow, elongated, semipermeable fibers are arranged or distributed in an annular bundle or bundle in the oxygenation chamber and secured at both axial ends with an encapsulation compound. The opposite ends of the fibers are open to an upper space for the gas formed in the housing external to the oxygenation chamber. The fibers that have an aggregate volume that is between 0.5 and 0.6 of the volume in the oxygenation chamber between the encapsulation compound at both axial ends. A combined blood / heat exchanger reservoir including a housing capped by a cover jointly defines an internal reservoir chamber, an inlet for venous blood in the cover, a heat exchanger within the chamber including a plurality of heat exchange elements, and an outlet for blood in a lower portion of the reservoir chamber. The heat exchange chamber is defined by guides that closely surround the heat exchange elements and extend down from a location in an upper portion of the reservoir chamber. The heat exchange chamber has an upper entrance open to the inlet for the venous blood and a lower outlet open to the reservoir chamber so that the blood from the venous blood inlet must flow through the exchange chamber of the venous blood. heat before it reaches the storage chamber. Preferably, the guides are concentric tubes defining an annular heat exchange chamber that terminates at an elevation of approximately 1/4 of the distance from the bottom of the reservoir chamber. The additional objects and advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of a currently preferred embodiment of the invention.

Brief Description of the Drawings Figure 1 is a schematic diagram of an extracorporeal circuit including the elements of the present invention; Figure 2 is a cross-sectional view of a heat exchanger / reservoir for use in extracorporeal circuits of adults; Figure 3 is a cross-sectional view of a low fattening volume oxygenator for use in adult extracorporeal circuits; Figure 3a is an exploded sectional view of the oxygenator of Figure 3; Figure 4 is a cross-sectional view of a heat exchanger / reservoir for use in the extracorporeal circuits of infants / infants; Figure 5 is a cross-sectional view of a low fattening volume oxygenator for use in the extracorporeal circuits of infants / infants; Figure 5a is an exploded sectional view of the oxygenator of Figure 5; Figure 6a is a schematic perspective view of a step in assembling an exemplary hollow fiber bundle or bundle; Figure 6b is a schematic perspective view of a step in assembling another exemplary hollow fiber bundle or bundle; and Figure 7 is a cross-sectional view of the low fattening volume oxygenator of Figure 3 showing several of the key dimensions.

Description of the Preferred Modalities Figure 1 shows an example of an infusion system 20 using the elements of the present invention that include a venous line 22 leading from a patient to a venous inlet of a reservoir / heat exchanger 24. The reservoir 24 can also include cardiotomy entries, and the combined venous and cardiotomy fluid is filtered and heat treated before exiting through a lower outlet to a second conduit 26. The conduit 26 leads to an inlet of a blood pump 28, such as a centrifugal pump as shown, typically controlled by a controller (not shown). The outlet of the pump leads to a third conduit 30 which is connected to an inlet of a low fattening volume oxygenator 32. The blood is perfused with the oxygen within the oxygenator 32 and passed therefrom through a fourth. conduit 34 to an arterial filter 36. Oxygenated blood continues through arterial filter 36 to an arterial return line 38 that terminates in an arterial cannula (not shown) in the patient. Other components, such as the bubble detector 39, can be provided on the return line 38, as is well known in the art.

Tank / Heat Exchanger for Adult Figure 2 is a cross-sectional view through an exemplary heat exchanger / reservoir 40, sized for use in an adult extracorporeal circuit. The heat exchanger / reservoir 40 comprises a lower housing 42 covered by a cover 44. The housing 42 comprises a cylindrical outer wall 46 tapered outwards and upwards slightly and a floor 48 of the tank which, together with the cover 44, defines internally a reservoir chamber 52. The reservoir / heat exchanger 40 can be adapted in the conventional ways to be secured in a location adjacent to an operating table. An elongated conical central spacer 56 extends upwardly from the floor 48 of the reservoir in proximity to the cover 44. The central spacer 56 is preferably concentrically positioned within the outer wall 46 to define an internal boundary of the chamber 52 of the deposit. The chamber 52 of the reservoir thus comprises a generally annular, long space defined within the housing 42. The cover 44 includes an external projection 58 surrounding the upper projection of the external wall 46. An O-ring 60 provides a seal between the housing 42 and cover 44. Inwardly of projection 58, cover 44 includes a first turret 62 projecting upwards, a second smaller turret 64 formed above the first turret. The second turret 64 has a central opening in an upper wall for receiving a venous inlet adapter 66. The adapter 66 extends upward and branches outward into a venous inlet opening 68, and an upper sampling opening 70. A The third opening can be provided in the adapter 66 for receiving a temperature probe of the inlet blood 72. The adapter 66 of the venous inlet extends downward toward a space created within the upper turret 64 and joined on the lower side by a conical flow guide 74. A filter 76 for removing bubbles, annular, is provided within the space in the upper turret 64.

One or more cardiotomy 78 inlets may also be provided in the side wall of the upper turret 64. The reservoir 40 may be adapted for gravity, venous, conventional drainage, wherein a vent for the gas 79 in the cover 44 remains open In this mode, the chamber 52 is not sealed from the external atmosphere. More recently, advances in minimally invasive surgical techniques have dictated the use of smaller and smaller venous cannulas, and a negative pressure on the venous return line can be advantageous. In this mode, a vacuum source can be connected to the chamber 52 to help suck the venous blood from the patient, such as by securing a vacuum line (not shown) to the gas vent 79. This seals the chamber 52 of the external atmosphere and creates an internal negative pressure. A plurality of inlets 80 for the heat exchange chamber are provided between the outer edges of the flow guide 74 and an inner corner formed between the first and second turrets 62, 64. The inlets 80 may be of a regular series of openings , or slots, or may be formed by an annular space surrounding the flow guide 74 interrupted by rungs connecting the flow guide with the cover 44. A guide or wall 82 of the internal heat exchange chamber, generally cylindrical, extends downward from the flow guide 74 to the reservoir chamber 52. The internal heat exchange guide 82 is spaced concentrically about the central spacer 56. An external, generally cylindrical, heat exchange guide 84 is downwardly dependent. from a first turret 62 to concentrically surround the internal heat exchange guide 82, and defines an annular heat exchange chamber 86, between themselves. A plurality of heat exchange coils or elements 88 that internally define one or more flow paths are helically positioned in the annular heat exchange chamber 86. Preferably, an input conductor 90 of the single heat exchanger, in cooperation with a Exit heat exchange duct (not shown), supplies a flow of the heat transfer medium into the coils 88. In the preferred embodiment, the means for heat transfer is water, although other means are contemplated. The annular heat exchange chamber 86 defined between the guides 82, 84 extends downwardly from the cover 44 a substantial distance towards the floor of the reservoir 48. In a preferred embodiment, the guides 82, 84 terminate at an exchange exit of heat 92 which is located above the floor of the tank 48 a distance of about 1/4 part of the total height of the chamber 52 of the tank. This relative distance can be modified depending on the total volume of the chamber 52 of the reservoir, and its radial dimensions. A large defoaming element 100 closely surrounds the external heat exchange guide 84. The defoaming element 100 continues radially downward, below the annular heat exchange chamber 86 in contact with the central spacer 56. The defoaming element 100 may be of a variety of constructions, but is preferably a polymeric mesh treated with a defoaming substance. . A support sleeve 102 surrounds and contains the defoaming element 100. The support sleeve 102 is desirably fixed rigidly to the upper part of the cover 44, and in the lower part to the central spacer 56, or to the floor of the tank 48. The support sleeve 102 may take a variety of forms, but is preferably a plastic element having a grid-like or other perforated configuration. A short media or external polyester filter 104 surrounds the support sleeve 102 and contains a non-woven filter 106 around the lower end thereof. The nonwoven filter 106 has a cup shape and extends upwardly of the outlet 92 for heat exchange. The floor 48 of the reservoir defines a peripheral flow channel 110 which undergoes gradual transitions to a well or deep drainage cavity 112 on a circumferential side. A number of openings are formed in the housing adjacent the drainage well or cavity 112. Especially, a lower sampling opening 114, a hemoglobin concentration line 116, and an opening for the exit of blood 118, all communicate through the openings with the drainage well or cavity 112. A fourth opening can receive a lower blood temperature probe 120.

Operation of the Tank / Heat Exchanger for an Adult In operation, venous blood is introduced to the heat exchanger / reservoir 40 through the venous inlet opening 68. The venous blood travels down through the adapter 66 and radially outwardly through the filter 76 to remove the bubbles as indicated by the flow arrows 130. The fluid aspirated through the cardiotomy lines is introduced to the cardiotomy 78 inlets and passes through the filter 76 to remove the bubbles as indicated by the flow arrows 132. this way, the venous inlet blood is not mixed with the cardiotomy fluid that passes through the filter 76 to remove the bubbles. The cardiotomy fluid and venous blood pass down through the inlets 80 of the heat exchange chamber to the annular heat exchange chamber 86. The blood then flows by gravity (or under the influence of a slight vacuum, if venous drainage aided by a vacuum is desirable) through the heat exchange coils 88 in a single pass, as indicated by the flow arrows 134. The blood treated with heating leaves the heat exchange chamber 86. to the reservoir chamber 52 through the heat exchange outlet 92. After passing through the heat exchange chamber 86, the blood continues down and out through the element 100 to remove the foam, the support sleeve 102, non-woven filter 106, and polyester filter 104, towards the space between the polyester filter and the outer wall 46. The blood level under the heat exchange chamber 86 and the short half 104 may reach or exceed that of the heat exchange outlet 92, but desirably does not exceed the upper edge of the nonwoven filter 106 to ensure proper filtration. The blood then continues through the flow channel 110 into the drainage cavity or well 112, and out through the exit opening 118. An advantage of the present reservoir / heat exchanger 40 is the provision of an exchange chamber. of heat 86 separated inside the tank. With such an arrangement, the ratio of the surface area of the heat exchange coils 88 to the volume of the blood in the heat exchange chamber 86 is maximized, and the blood is guided through each coil. The operation of the heat exchanger does not therefore depend on the level of the blood inside the tank. As will be appreciated by those skilled in the art, separate heat exchange chambers within the reservoir other than the annular column embodiment shown may be equally effective since the solution is the decoupling of the heat exchange efficiency. of the blood level of the deposit. In addition, heat transfer elements other than the coils shown, such as fins or straight tubes, may be used.

Low Fatigue Volume Oxygenator for Adult As seen in Figure 1, a blood pump 28 drives blood from the opening 118 to an oxygenator 32 of the blood. Although the previously described heat exchanger / reservoir 40 may be coupled with a variety of oxygenators, a particularly preferred oxygenator 150 is observed in Figures 3 and 3a. Oxygenator 150 is a low fattening membrane membrane oxygenator having a single blood inlet and outlet, and an inlet and outlet for the single gas. As seen in an exploded manner in Figure 3a, the main components of the oxygenator 150 comprise a central cylindrical housing 152, an upper lid 154 on an axial end of the housing, and a lower lid 156 and a blood inlet cap 158 on an opposite axial end of the housing. The housing 152 is preferably cylindrical, but it can be of other shapes, and it is placed concentrically around an axis (not shown). The components of the housing 152, the top cover 154, the bottom cover 156, and the inlet cap of the blood 158, are preferably molded from biocompatible, plastic materials. Biocompatible coatings, such as Duaflo® available from Baxter Healthcare Corporation, may be provided on the plastic components of the oxygenator 150 to reduce blood interactions. A primary advantage of the oxygenator 150 is the small number of parts. In addition to those mentioned above, the only other components of the oxygenator 150 are a plurality of hollow semipermeable fibers 160 (shown partially in chamber 168) that extend generally axially within the housing 152, and the encapsulation regions 170, 172 in both ends of the fibers and the housing. The respective components, except hollow fibers 160, are easily molded and fixed together using a variety of means. For example, casing parts may be provided with interference flanges or fasteners in conjunction with a sealing mechanism, such as 0-rings, to enable snap-fitting. Alternatively, the parts may be permanently joined together, such as with a biocompatible adhesive, or, more preferably, with an ultraviolet (UV) weld. The specific structural attributes of the low fattening volume oxygenator 150 will now be described in greater detail. The central housing 152 comprises an outer wall 164 positioned concentrically around an internal wall 166. An elongated annular oxygenation chamber 168 is defined between the inner surface of the outer wall 164 and the external surface of the inner wall 166. The hollow fibers 160 they generally extend axially within the oxygenation chamber 168 and are rigidly secured within the chamber between an upper encapsulation region 170, and a lower encapsulation region 172. The encapsulation regions 170 and 172 delimit the chamber of encapsulation 170. oxygenation 168 at each axial end. As is well known in the art, the hollow fibers 160 are placed and secured with the encapsulation material at both ends, such material is then cut perpendicularly to the axis to expose the open ends of each individual fiber. The encapsulated bundle or bundle of the fibers 160 is then sealed in place in a level manner with both ends of the housing 152. The housing 152 further includes a transversely extending lower wall 174, and is preferably molded integrally with the internal wall 166. at a distance from the lower end of the housing. The top cap 154 comprises an upper wall 180 having a peripheral side wall 182 attached thereto. As seen in Figure 3, the top cap 154 fits over the upper end of the housing 152 so that the casing portions of the side wall 182 and the outer wall 164 are in exact correspondence. More specifically, an internal projection 184 on the top cover 154 contacts a step 186 at the upper end of the outer wall 164. In addition, a portion of the side wall 182 extends around a small projection 188, and a skirt 190 extends downwardly around and in contact with, a large projection 192. With reference to Figure 3, an output manifold for blood is defined within the top cap 154 and outside the housing 152. More specifically, the side wall 182 defines a small annular space 200 adjacent to the small projection 188. The small projection 188 and the annular space 200 extend substantially around the periphery of the housing 152. The skirt 190 comprises a bulged portion. outwardly on one side of side wall 182 and define a larger space 202. Smallest space 200 and largest space 202 are in fluid communication to define the blood outlet manifold surrounding a plurality of outlets 204 of the oxygenation chamber. A recirculation opening 206 extends radially outward from the side wall 182 at a location diametrically opposite the large space 202 and a blood outlet opening 208 extending radially outwardly from the skirt 190. An aperture 210 can be provided in the top cap 154 for receiving a temperature probe 212 for measuring the temperature of the blood within the large space 202. The top wall 180 of the top cap 154 is shaped to define an upper space 220 for the gas, annular, adjacent to the upper encapsulation region 170 and sealed from the blood exit manifold. An inlet aperture 222 for the gas, in the center of the top cap 154, opens toward a large, central gas manifold, limited by the inner wall 166, the lower wall 174, and the top cap 154. The open ends of the hollow fibers 160 adjacent to the upper space 220 for the gas, are in fluid communication with this chamber for the gas.

Still referring to Figure 3a, the lower lid 156 comprises a lower wall 230, an inner skirt 232, and an outer skirt 234. The inner wall 166 of the housing 152 includes a lower cylindrical portion 236 below the bottom wall 174. A number of circumferential grooves or openings define the inlets 238 of the oxygenation chamber between this lower portion 236 and the lower wall 174. Although not shown, the lower portion 236 is integrally molded desirably with the inner wall 166 and the lower wall. 174 to define an inner core of the housing 152. The lower cover 156 fits over the lower end of the housing 152 with the inner skirt 232 in sealed contact with the lower portion 236, and the outer skirt 234 surrounding and being in sealed contact with the external wall 164. The lower wall 230 of the lower lid 156 is spaced from the lower encapsulation region 172 to define a annular lower manifold 239 (Figure 3) in fluid communication with the open ends of the hollow fibers 160 secured within the lower encapsulation region 172. An exit aperture 240 for the gas is also in fluid communication with the manifold 239 that extends downwards from the lower wall 230 on one side thereof.

The cover 158 for the blood inlet comprises a circular projection 242 radially positioned and an opening 244 for the blood inlet, axial. The projection 242 fits closely within the inner surface of the lower portion 236 of the inner wall 166 and is secured thereto. The projection 242 is thus spaced from the lower wall 174 to define a space 246 for the distribution of blood therebetween, with the inlets 238 of the chamber desirably evenly distributed around the circumference of the dispensing space. The oxygenator 150 for the adult preferably has a fattening volume of between 130-180 ml.

Operation of the Low Fatigue Volume Oxygenator for an Adult With reference to Figure 3, the respective gas and blood flows through the oxygenator 150 are shown. The blood is introduced through the lower inlet opening 244, central, and is evenly distributed radially to the out in all directions in space 246. The blood passes out through the inlets 238 of the chamber, into the oxygenation chamber 168. As noted by the non-linear blood flow arrows 250, the blood passes up through the chamber 168 in the spaces formed between the hollow fibers 160. In a preferred embodiment, the hollow fibers 160 are arranged or distributed in sequenced layers of fiber mats, with the fibers in adjacent mats that are helically angled from related way to each other. In a first example, the angle of the fibers in each mat is in the same helical direction, whereas in a second example, the angle of the fibers in the adjacent mats is in the opposite helical direction. In the first example, the blood passes between the fibers in a generally helical path through the oxygenation chamber 168, whereas in the latter example, the blood passes between the fibers in a zigzag fashion from one end of the chamber 168 until the other. Various configurations of the hollow fiber architectures are available for use with the low priming volume oxygenator, such as for example in PCT Publication No. WO 97/08933, which is expressly incorporated herein by reference. Exemplary hollow fiber architectures are shown and described in greater detail with respect to Figures 6a and 6b. Blood flows through chamber 168 as shown by arrows 250 from inlets 238 to exits 204. As mentioned above, inlets 238 and outlets 204 are provided substantially around the full circumference of housing 152 to assist to ensure uniform distribution of blood flow within the chamber 168. Because of the circular arrangement of the inputs 238 and the outputs 204, blood flows substantially axially into the chamber 168 once the hollow fibers 160 have been passed. The now oxygenated blood fills the annular region defined by the spaces 200 and 202 and is available for exit through the opening. of recirculation 206 and / or the exit opening of the blood 208. The gas flows to the oxygenator 150 through the inlet opening 222 and into the region in communication with the upper space 220 for the gas. As mentioned, the hollow fibers 160 are open at the upper end of the upper encapsulation region 170 and the gas flows into the hollow fibers and continues through the lumens of the fiber to the lower manifold 239. The inlet gas is preferably pure or quasi-pure oxygen which moves outwardly permeating through the semipermeable tubular wall of each individual hollow fiber 160 into the blood which is passing in an opposite direction, thereby raising the partial pressure of the oxygen in the blood . The impulse for the migration of the gas molecules through the walls of the tubular fibers is a differential partial pressure of each respective gas. The carbon dioxide moves through permeation acia in from the blood, towards each lumen of the individual fiber, thus reducing the partial pressure of the carbon dioxide in the blood. The end result is that the blood absorbs oxygen and expels carbon dioxide into the gas stream. The gas leaves the open ends of the hollow fibers 160 towards the lower manifold 239 and is expelled through the outlet opening 240 of the gas.

Tank / Heat Exchanger for a Neonate / Infant Figure 4 is a cross-sectional view through an exemplary heat exchanger / reservoir 340, sized for use in an extracorporeal neonatal / infant circuit. The reservoir 340 is similar in many respects to the reservoir 40 for the adult described above, and as such, the like elements are numbered in parallel in the range of 300 and 400 and will not be described in more detail. The heat exchanger / reservoir 340 comprises a lower housing 342 surmounted by a cover 344.

The housing 342 comprises a cylindrical outer wall 346 tapered outwardly and slightly upward and a floor 348 of the reservoir which, together with the cover 344, internally defines a reservoir chamber 352. A ring at 0 360 provides a seal between the housing 342 and cover 344. Conventional mounting means may be provided to secure the heat reservoir / exchanger 340 at a location adjacent to an operating table. In contrast to the reservoir 40 for the adult described above, the reservoir 340 for the neonate / infant does not include a central conical spacer, and the reservoir chamber 352 thus comprises a generally cylindrical volume defined within the housing 342. As above, the cover 344 includes a first turret 362 projecting upwards, and a second smaller turret 364 formed above the first turret. The second turret 364 has a central opening in an upper wall to receive an upwardly extending venous inlet adapter 366 and branches outwardly into a venous inlet opening 368, and a superior sampling opening 370. A third opening can be provided in the adapter 366 to receive a temperature probe 372 for the incoming blood. The adapter 366 for the venous inlet extends downward toward a space created within the upper turret 364 and joined on the lower side by a conical flow guide 374. A filter 376 for removing the annular bubbles is provided within the space in the upper turret 364. One or more cardiotomy 378 entries may also be provided in the side wall of the upper turret 364. The reservoir 340 may be adapted for conventional venous gravity drainage in which a 379 ventilation for the gas in the cover 344 is open so that chamber 352 is not sealed from the external atmosphere. Alternatively, a vacuum line (not shown) can be attached to the vent for the gas 379 which seals the chamber 352 of the external atmosphere and creates a negative pressure internally to help draw the venous blood from the patient. A plurality of heat exchange inputs 380 are provided between the outer edges of the flow guide 374 and an inner corner formed between the first and second turrets 362, 364. As in the initial embodiment, the 380 entries can be a regular series of openings, or slots, or may be formed by an annular space surrounding the flow guide 374 interrupted by rungs connecting the flow guide with the cover 344.

A wall or guide 382 of the internal, generally cylindrical, heat exchange chamber extends downwardly from the flow guide 374 within the reservoir chamber 352. The internal heat exchange guide 382 is spaced concentrically within the wall external 346. An external heat exchange guide 384, generally cylindrical, is downwardly dependent on the first turret 362 to encircle the heat exchange guide 382 and defines an annular heat exchange chamber 386 therebetween. A plurality of heat exchange elements or coils 388 defining one or more routes for fluid flow are helically placed in the annular heat exchange chamber 386. Preferably, a conduit 390 of the inlet for the single heat exchange, in cooperation with the external heat exchange conduit (not shown), supplies a flow of the heat transfer medium to the inner part of the coils 388. The annular heat exchange 386 defined between the guides 383, 384 extends downwardly from the cover 344 a substantial distance to the floor of the reservoir 348. In a preferred embodiment, the guides 382, 384 terminate at an outlet for heat exchange 392 which is located above the floor of the reservoir 348 at a distance of about 1/4 of the total height of the reservoir chamber 352. Again, this relative distance can be modified depending on the total volume of the reservoir chamber 352, and its Radial dimensions, and it may be different from the configuration of reservoir 40 for the adult. The reservoir 340 for the infant / infant includes a series of concentric filters surrounding the heat exchange chamber 386 as previously described. Thus, the reservoir 340 preferably includes a large foam removal filter 400, surrounded by a support sleeve 402, with a short stocking of external polyester 404 and a non-woven filter 406 around the lower end thereof. The nonwoven filter 406 extends above the height of the outlet 392 for heat exchange proportionally higher in the infant / neonate reservoir 340 than in the adult reservoir 40. The reservoir floor 348 defines a flow channel 410 that provides a gradual transition from the floor to a well or deep drain cavity 412. A number of openings can be formed in the housing adjacent the drainage well or cavity 412, although only one exit opening for the blood 418 is shown.

Operation of the Tank / Heat Exchanger for the Infant / Infant The operation of the reservoir 340 for the infant / infant is as described above with respect to reservoir 40 for the adult, with the venous blood being introduced through the venous inlet opening 368 and exiting through the lower outlet 418. As previously, the venous entry blood is not mixed with the cardiotomy fluid that passes through the filter 376 to remove the bubbles. Within chamber 352, the cardiotomy fluid and venous flow pass down through the heat exchange inlets 380 into the annular heat exchange chamber 386. The blood then flows by gravity onto the exchange coils heat 388 in a single pass, as indicated by the flow arrows 434, and exits towards the reservoir chamber 352 through the outlet 392 for heat exchange. After passing through the heat exchanger, the blood continues down and out through the foam removal element 400, the support sleeve 402, a non-woven filter 406, and the polyester filter 404, into the space between the polyester filter and the outer wall 346. The increased height of the upper edge of the nonwoven filter 406 is necessary to prevent overflow and ensure proper filtration of the blood because of the smaller volume, and thus a blood level more variable in the reservoir chamber 352. After being filtered, the blood then continues through the flow channel 410 and into the drain cavity or well 412.

Oxygenator of low fattening volume for infant / infant As seen in Figure 1, a blood pump 28 drives blood from the outlet opening 418 of the reservoir to an oxygenator 32 of the blood. Although the reservoir / heat exchanger 340 previously described can be coupled with a variety of oxygenators, a particularly preferred oxygenator 450, suitable for use with neonates or infants, is observed in Figures 5 and 5a. Oxygenator 450 is similar in many respects to the adult oxygenator 150 described above, and as such, like elements are numbered in parallel in the range of 400 and 500 and will not be described in more detail. As seen in an exploded manner in Figure 5a, the main components of the oxygenator 450 comprise a central cylindrical housing 452, an upper cover 454 on an axial end of the housing, and a lower cover 456 and a cover 458 for the entry of blood on an opposite axial end of the housing. The housing 452 is preferably cylindrical, but may be of other shapes, and is arranged concentrically-about an axis (not shown). The components of the housing 452, the top cover 454, the bottom cover 456, and the cover 458 for the entry of the blood, are preferably made of biocompatible, molded plastic materials. Biocompatible coatings, such as Duraflo® available from Baxter Healthcare Corporation, may be provided on the plastic components of the oxygenator 450 to reduce interactions with the blood. As in the previous embodiment, the oxygenator 450 has a very small number of parts for ease of manufacture and assembly. In addition to those mentioned above, the only other components of the oxygenator 450 are a plurality of hollow semipermeable fibers 460 which extend generally axially within the housing 452, and encapsulation regions at both ends of the fibers and the housing. The respective components, except hollow fibers 460, are easily molded and fixed together using a variety of means. For example, as described above, a pressurized assembly, biocompatible adhesive, or, more preferably, ultraviolet (UV) welding, can be used. The central housing 452 comprises an outer wall 464 positioned concentrically about an inner wall 466. An elongated annular oxygenation chamber 468 is defined between the internal surface of the outer wall 464 and the external surface of the inner wall 466. The hollow fibers 460 they generally extend axially within the oxygenation chamber 468 and are fixed or rigidly secured within the chamber between an upper encapsulation region 470, and a lower encapsulation region 472. The housing 452 further includes a bottom wall 474 extending through the inner wall 466 and spaced from the lower end of the housing. The top cover 454 comprises an upper wall 480 having a peripheral side wall 482 attached thereto. As seen in Figure 5a, the top cap 454 fits over the upper end of the housing 452 so that an internal projection 484 on the top cap 454 contacts a step 486 at the top end of the outer wall 464. In addition , a portion of the side wall 482 extends around a small projection 488, and a skirt 490 extends downwardly around and in contact with a large projection 492. As in the first embodiment, and with reference to Figure 5, an output manifold for the blood is defined within the upper cover 454 and outside the housing 452. More specifically, the side wall 482 is shaped to define a small annular space 500 between a plurality of outlets 504 of the oxygenation chamber and a recirculation opening 506. A skirt 490 comprises a portion bulging outwardly on one side of side wall 482 and defining a larger space 502 between outputs 504 of the chamber. Oxygenation line and an outlet opening 508 for the blood, which extends radially outward from the skirt 490. The smaller space 500 and the larger space 502 are in fluid communication to define the manifold for the outflow of the blood surrounding the outlets of oxygenation chamber 504. An opening may be provided in upper lid 454 to receive a temperature probe 512 for measuring the temperature of blood within large space 502. Upper wall 480 of upper lid 454 is shaped to define a top space for the annular gas 520, adjacent to the upper encapsulation region 470 and sealed from the blood exit manifold. An opening 522 for the gas inlet in the center of the upper lid 454 opens to a large, central, manifold, limited by the inner wall 466, the lower wall 474, and the top wall 454. The open ends of the hollow fibers 460 adjacent to the upper space 520 for the gas, are in fluid communication with this gas chamber. Still with reference to Figure 5a, a number of circumferential grooves or openings in the inner wall 466 define the inlets 538 of the oxygenation chamber. The lower cover 456 fits over the lower end of the housing 452 with an inner skirt 532 in sealed contact with the lower portion of the inner wall, and an outer skirt 534 that surrounds and is in sealed contact with the outer wall 464. The cover lower 456 is spaced from the lower encapsulation region 472 to define a lower annular manifold 539 (FIG. 5) in fluid communication with the open ends of the hollow fibers 460 secured within the lower encapsulation region 472. An exit aperture 540 for the gas in fluid communication with the manifold 539 extends downward from the bottom cover 456 on one side thereof. The inlet cap 458 for the blood comprises a circular projection 542 radially positioned and an opening 544 for the blood inlet, axial. The projection 542 fits snugly within the lower portion of the inner wall 466 and is secured thereto. The projection 542 is thus spaced from the bottom wall 474 defining a space 546 for the distribution of blood therebetween, with the inlets 538 of the chamber desirably uniformly distributed around the circumference of the dispensing space. The oxygenator 450 for the infant / neonate preferably has a fattening volume of between 56-80 ml.

Operation of the Low Fatigue Volume Oxygenator for a Infant / Infant With reference to Figure 5, the respective blood and gas flows through the oxygenator 450 are displayed. The blood is introduced through the lower inlet opening 544 and is evenly distributed radially outwardly in all of them. the directions in the space 546. The blood passes out through the entrances 538 of the chamber to the oxygenation chamber 468. As seen by the blood flow arrows 550, non-linear, the blood passes upwards to through chamber 468 in the spaces formed between hollow fibers 460. Blood flows substantially axially through chamber 468 as shown by arrows 550 from inlets 538 to exits 504 and is evenly distributed therein. by the circular arrangement of the entrances and exits. The gas flows to the oxygenator 450 through the inlet opening 522 and into the region in communication with the upper space 520 for the gas. Oxygen is permeated outwardly through the semipermeable tubular wall of each individual hollow fiber 460 into the blood that is passing in the opposite direction, while the carbon dioxide is moved by inward permeation from the blood within the blood. each lumen of the individual fiber. The gas leaves the open ends of the hollow fibers 460 towards the lower manifold 539 and is exited through the outlet opening 540 for the gas.

Architecture of the Hollow Fibers Of course, there are a number of different configurations of hollow fibers that can be used with the present oxygenators, but a particular preferred arrangement of the laminated sheets of the fibers produces optimum performance. With reference to Figures 6a and 6b, two exemplary embodiments of the stratified sheets of the fibers are shown. Both of these embodiments show layers of fibers that are wound-spirally around a cylindrical core 600, which is removed after the bundle or bundle of annular fibers is assembled or assembled. Alternatively, the hollow fiber layers can be spirally wound around the inner wall 166 or 466 of one of the two oxygenators, prior to mounting the outer wall thereon. However, for reasons of manufacturing efficiency, a separate core is used to wind the layers of the fibers, which are then removed and assembled separately with the other parts of the oxygenator. Those skilled in the art will recognize that various manufacturing methods are possible. In Figure 6a, a first layer 602 and a second layer 604 are wound around the core 600. Both the first and second layers 602, 604 comprise a plurality of hollow fibers joined together in a parallel spaced network or arrangement with monofilaments. , or another similar file. A first plurality of fibers 606 in the first layer 602 are arranged at an angle with respect to the axis of the core, while a second plurality of fibers 608 in the second layer 604 are arranged at a different angle. The angles that both the first and second pluralities of fibers 606, 608 make with the shaft are in the same rotary direction, and are preferably less than 45 °. In addition, the angles of the two plurality of fibers are desirably within 15 ° to each other, more desirably about 9 °, as shown. When the entire bundle or bundle of fibers has been wound and assembled in the oxygenator, the layers are wound spirally, while the individual fibers are wound helically. In the embodiment of Figure 6a, the flow of blood through the oxygenation chamber will follow a non-linear path between the alternatively angulated fibers, and will generally be helically guided around the annular space. By contrast, the embodiment of Figure 6b includes a first layer of fibers 610 and a second layer of fibers 612, wherein a first embodiment of the fibers 614 and a second plurality of the fibers 616 are angled in the opposite rotational direction around the core 600 Again, the angles that both the first and the second pluralities of fibers 614, 616 form with the shaft are preferably less than 45 °, and desirably the angle comprised between them is about 90 °. This arrangement induces a non-linear and generally axial flow of the blood between the alternatively angulated fibers. In both embodiments of the fiber shown in Figures 6a and 6b, the two fiber layers are desirably joined together in a mat prior to the spiral winding thereof around the core. That is, the two joined layers comprise a mat which is then spirally wound in the core. This mat is preferably well assembled before assembly of the oxygenator, which facilitates the automation and rapid manufacture of this oxygenator. A suitable source of such glass fibers is Akzo Nobel N.V. from Arnhem, the Netherlands, although other sources are available.

Extracorporal Low Fat Volume Circuit The present invention provides improvements over the previous extracorporeal circuits because it has a very low priming volume and a high oxygenation operation. The very low priming volume allows the use of a single size of oxygenation for a much larger range of patient weights, which is not possible with oxygenators currently on the market that have an equivalent oxygenation capacity. Therefore, the two oxygenator sizes shown here are sufficient to cover a range of patients from neonates to adults weighing more than 140 kg (300 pounds). More specifically, the oxygenator 450 for the infant / infant shown and described with respect to Figures 5 and 5a is designed for use in extracorporeal circuits for patients ranging from neonates to patients weighing approximately 20 kg (44 pounds) . The oxygenator 150 for the adult in Figures 3 and 3a is designed for use in extracorporeal circuits for patients ranging in weight from approximately 20 kg (44 pounds) to approximately 140 kg (308 pounds). A number of factors contribute to making the oxygenator of the present invention superior to those currently available. Some of these factors include the removal of the heat exchanger from the incorporation into the oxygenator to the reservoir, the particular geometry of the oxygenator, and a hollow fiber architecture which is particularly well suited for internal function and the design complement of the specific oxygenation chamber. The advantages of removing the heat exchanger from the oxygenator have been described above. In A ~ = the total area of the inputs 238 of the oxygenation chamber A5 = the total area of the outputs 204 of the oxygenation chamber A «= the cross-sectional area of the blood inlet and outlet connectors A = the external, effective, aggregate surface area of the hollow fibers in the oxygenation chamber.

From the above dimensions, a number of volumes can be calculated as follows: Vi = the volume between the internal and external walls without the encapsulation regions 170, 172 V2 = the volume between the inner and outer walls without the encapsulation regions, and outside the hollow fibers V3 = the volume occupied by the aggregated fibers without the encapsulation regions followed a detailed description of the particular geometry of the improved oxygenator is provided. With reference to Figure 7, the low fattening volume oxygenator 150 for the adult described previously with reference to Figures 3 and 3a is shown with several indicated key dimensions. The oxygenation chamber 168 is defined between the external diameter Dx of the internal wall 166 and the internal diameter D2 of the external wall 164. H indicates the common length of both the external wall 164 and the internal wall 166, while the length between the two encapsulation regions 170 and 172 is indicated as h. Therefore, the oxygenation chamber 168, 468 has a height h. A number of cross-sectional areas derived from the axial and radial dimensions are defined as follows, with the first three being taken normal to the axis of the cylindrical walls.

Ai = the annular area of the oxygenation chamber A2 = the aggregate area within the hollow fibers A3 = the area of blood flow within the oxygenation chamber 168 (ie, to the area outside the hollow fibers) V = the volume occupied by the aggregated fibers between the encapsulation regions V5 = the priming volume of the upper lid 154 V6 = the volume of fattening of the distribution space 246 for the blood i = the volume between the internal and external walls and the encapsulation regions v2 = the volume between the internal and external walls and the encapsulation regions, and outside the hollow fibers (static priming volume) A number of mathematical relationships can be established between these geometries: Ai = A2 + A3 = u / 4 (D2Z - D! Z) Vi = Ai x H = V2 + V3 i = Ai xh = v2 + V The preferred relationships between the geometric parameters for the low fattening oxygenator 150 for the adult described with respect to Figures 3 and 3a are as follows (it should be noted that the corresponding units can be found in the Table II, and any necessary conversions are implicit in the RESULTS column).

TABLE I It will also be understood that the preferred ranges given in Table I (and the other tables here) are specific to the metric units used in the example, but are translatable to other units with the appropriate calculations which could be evident for those with experience in the technique. For example, the first calculation of Ai could have a different result if the inches were the units; as in the following calculation with the preferred dimensions: Di = 85 mm = 3.35 inches D2 = 62 mm = 2.44 inches Ai = (D22 - Di2) xp / 4 = 4.14 inches Therefore, the intervals given above must be converted to the appropriate units, but represent the optimal geometric relationships which assure a relatively high oxygen transfer rate and blood flow in an oxygenator with a low priming volume. An important parameter represented in Table I is the ratio of the volume of the aggregated fibers (V4) to the volume between the internal and external walls (vi). That is, how much space does the fiber occupy within the blood chamber, or, on the contrary, how much space is allowed for the flow of blood? This ratio (V4 / v?) In relation to the absolute difference in volumes (v3. - V) is a reason for the improved functioning of the present oxygenator. The following table shows a range of exemplary values as well as a preferred value particularly of the above parameters for the low fattening volume oxygenator 150 for an adult.

TABLE II Similar considerations for the low fattening volume oxygenator for an adult are shared by the low 450 'fattening volume oxygenator for infant / infant described with respect to Figures 5 and 5a. The preferred relationships between the geometrical parameters are modified for this smaller size oxygenator as follows (again, the corresponding units can be found in Table IV, and any necessary conversions are implicit in the RESULTS column): TABLE III The following table shows a range of exemplary values and a preferred value particularly for the various parameters in the fattening volume oxygenator under 450 for an infant / neonate: TABLE IV A comparison of the present oxygenator for adult 150 with oxygenators of similar capacity is given in the following Table: ts > OR TABLE V COMPARISON OF FUNCTIONING OF MEMBRANE OXYGENERS FOR ADULTS H.H From this graph it is readily apparent that the present oxygenator 150 for an adult provides a great advantage over competition in one of the key aspects of a successful oxygenator, its priming volume or preparation. The low fattening volume of 170 ml is almost 100 ml lower than the next smallest, and almost 400 ml lower than the largest in this group. Additionally, oxygenator 150 has the lowest effective effective hollow fiber surface area and works acceptably in all other categories compared to the competition. The reduction in the surface area of the hollow fiber results in a lower cost for the oxygenator. Importantly, the oxygenator 150 has a transfer rate of 02 of about 57.5 ml / min / lpm at a blood flow rate of about 7 lpm. This means that the oxygenator 150 transfers an oxygen volume of more than one third of its blood fattening volume in one minute, at a flow rate of 7 lpm (which is typical for adult patients). The ratio of the oxygen transfer rate (at the prescribed flow rate) to the fattening volume is approximately 0.34 (57.5 / 170) bpm / min. The closest competitor has one such ratio of approximately 0.22 (56.9 / 260) bpm / min. A comparison chart similar to one given above for the 450 infant oxygenator / infant is provided below.

TABA VI COMPARISON OF FUNCTIONING OF THE MEMBRANE OXYGENERS FOR NEONATO / INFANTE 1 ~? Again, the priming volume of the 450 oxygenator for an infant / neonate is the lowest in its class, in company with that of Dideco Liliput, which also has a 60 ml priming volume. The Dideco oxygenator, however, has a maximum blood flow of only 0.8 bpm, and therefore is only suitable for use with neonatal patients. In contrast, the present oxygenator 450 has a blood flow of up to 2.0 lpm, and is suitable for use with both infant and neonate patients. Importantly, the oxygenator 450 has a transfer rate of 02 of about 62.5 ml / min / lpm at a blood flow rate of about 2 lpm. This means that the oxygenator 450 transfers an oxygen volume of the same magnitude as its blood fattening volume in one minute, at a flow rate of 2 lpm (which is typical for infants). The ratio of the oxygen transfer rate (at the prescribed flow rate) to the fattening volume is approximately 1.04 bpm / min. In addition, the 450 infant oxygenator / infant is comparable to all other categories, although it has a slightly larger effective surface area of the hollow fibers, and therefore requires more fibers, which is a small price to pay for the reduction in volume of the fattening.

Advantages of the Heat Exchanger In addition to providing a low priming volume oxygenator, the present invention obtains several advantages by moving the heat exchange function from the oxygenator to the reservoir. First, the heat exchanger is highly efficient. Tables V and VI also illustrate the operating factor of the present heat exchanger placed in the tank compared to the operating factor of the heat exchangers in the heat exchangers of the prior art. The operating factor is a measure of the temperature change of the respective fluids passing through the heat exchanger (here, typically blood and water), and is calculated as follows: P. F. = (Tb, output ~ Tb, input) / (Tw, antead - Tb, input) ßn don eb, enrada - Blood entry temperature Tb, salia - Blood output temperature T * r, «ntrd - Temperature Water input As can be seen, the operating factor of the heat exchanger of the present invention is comparable to those of the prior art. This results from the specific arrangement of the heat exchanger inside the tank. Although there have been deposits in the prior art that incorporate coils for heat exchange, they have been what can be called flooded chamber deposits with relatively inefficient heat exchange capabilities. With flooded chamber deposits, the operation of the heat exchanger is a function of the level of blood in it. The present heat exchangers / deposits shown and described above utilize a separate heat exchange chamber within the reservoir chamber to provide a single pass of the blood through the coils for heat exchange. That is, the blood is introduced into the reservoir chamber at an upper end and is guided through the annular heat exchange chamber and through all of the coils. Therefore, heat transfer is carried out in a fairly confined region and a maximum volume of blood is in and around the coils for heat exchange all the time, so that the heat transfer between the they are done more efficiently.

Perhaps more importantly, the operation of the heat exchanger is not a function of the level of blood in the reservoir. A disadvantage of locating the heat exchanger in the oxygenation chamber, in a so-called closed system, is that the blood is subject to some additional stress. By locating the heat exchanger in the reservoir, as in the present invention, the mechanical stress on the blood is reduced. That is, the blood passes through the heat exchanger by gravity (or under a slight vacuum) in a progression of natural drainage instead of being forced once the tubes or fins of heat exchange have been passed with the pressure of the fluid generated by a pump. Of course, the blood leaving the reservoir is then driven through the oxygenator and back to the patient using a pump, but the separation of the stages of heat exchange and elevation of the pressure in the extracorporeal system helps to reduce the damage to the blood. In other words, the blood is not subjected to mechanical stresses inside the chamber for heat exchange. Finally, the arrangement of the heat exchanger inside the reservoir also reduces the fattening volume of the complete extracorporeal circuit. In contrast to the flooded chamber deposits, blood is introduced into the reservoir chamber at an upper end and falls by gravity through the annular heat exchange chamber and through the coils before it is filtered and flows into the chamber. lower portion of the reservoir chamber. Accordingly, the previously unused volume within the reservoir chamber is now used by the heat exchanger. It is understood that the examples and embodiments described herein and shown in the drawings represent only the currently preferred embodiments of the invention, and are not intended to exhaustively describe in all possible detail the embodiments in which the invention can take a physical form. . Actually, modifications and additions to such modalities can be varied without departing from the spirit and scope of the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following

Claims (40)

1. A low priming or priming volume oxygenator, characterized in that it comprises: a rigid housing defining an annular oxygenation chamber having a first axial end and a second axial end; a plurality of hollow, elongated semipermeable fibers, arranged in an annular bundle or bundle in the oxygenation chamber and secured at both axial ends with an encapsulation compound, the opposite ends of the fibers are open to an upper space for the gas formed in the housing outside the oxygenation chamber, the bundle or bundle substantially fills the oxygenation chamber with the fibers having spaces for blood flow therebetween; a central inlet opening in communication with a space for the distribution of blood adjacent an axial end of the oxygenation chamber; a plurality of blood inlets in the housing, formed around the annular oxygenation chamber in communication with the space for blood distribution; a plurality of blood outlets in the housing formed around the annular oxygenation chamber on the axial end opposite the blood inlets; and wherein the oxygenator has a fattening volume of between 130 and 180 ml and an oxygen transfer rate ratio with respect to the fattening volume of at least about 0.34 lpm / min, at a flow rate of about 7 lpm .

2. The oxygenator according to claim 1, characterized in that the rigid housing consists essentially of five molded plastic parts, an inner core, an outer wall, an upper lid, a lower lid, and an inlet opening for the blood.

3. The oxygenator according to claim 2, characterized in that the parts of the rigid housing are press fit together.

4. The oxygenator according to claim 2, characterized in that the parts of the rigid housing are joined together.

5. The oxygenator according to claim 4, characterized in that the parts of the rigid housing are soldered by UV rays.

6. The oxygenator according to claim 2, characterized in that the inner core includes an inner wall spaced concentrically from the outer wall, the inner wall and the outer wall both are tubular and together define an annular oxygenation chamber therebetween, the chamber of oxygenation has a cross-sectional area normal to its axis of between approximately 24 and 28 square centimeters.

7. The oxygenator according to claim 6, characterized in that the inner wall and the outer wall have a sufficient axial length to ensure that a volume in the oxygenation chamber between the encapsulation compound at both axial ends is between about 320 and 360 ml.

8. The oxygenator according to claim 7, characterized in that the ring bundle comprises alternate layers of fiber mats, each layer of the fiber mat having a plurality of parallel fibers coupled, aligned so that the fibers extend helically around the oxygenation chamber.

9. The oxygenator according to claim 8, characterized in that the fibers in the adjacent layers of the fiber mats extend helically in different rotational directions.

10. The oxygenator according to claim 7, characterized in that the fibers in the annular bundle or bundle have an aggregate volume which is between 0.5 and 0.6 of the volume in the oxygenation chamber between the encapsulation compound at both axial ends.

11. A low fattening volume oxygenator, characterized in that it comprises: a rigid housing defining an annular oxygenation chamber having a first axial end and a second axial end; a plurality of hollow semi-permeable fibers, elongated, arranged or distributed in an annular bundle or bundle in the oxygenation chamber and secured at both axial ends with an encapsulation compound, the opposite ends of the fibers are open to an upper gas space formed in the housing external to the oxygenation chamber, the bundle or bundle substantially fills the oxygenation chamber with the fibers having spaces for blood flow therebetween; an inlet opening for blood, central, in communication with a space for the distribution of blood adjacent an axial end of the oxygenation chamber; a plurality of blood inlets in the housing, formed around the annular oxygenation chamber in communication with the space for blood distribution; a plurality of outlets for the blood in the housing formed around the annular oxygenation chamber on the axial end opposite the blood inlets; and wherein the oxygenator has a fattening volume of between about 56 ml and 80 ml and a flow capacity of about 2 lpm.

12. The oxygenator according to claim 11, characterized in that the rigid housing consists essentially of five molded parts of plastic, an inner core, an outer wall, an upper lid, a lower lid, and an inlet opening for the blood.

13. The oxygenator according to claim 12, characterized in that the parts of the rigid housing are press-fitted together.

14. The oxygenator according to claim 12, characterized in that the parts of the rigid housing are joined together.

15. The oxygenator according to claim 14, characterized in that the parts of the rigid housing are soldered by UV rays.

16. The oxygenator according to claim 12, characterized in that the inner core includes an inner wall spaced concentrically from the outer wall, the inner wall and the outer wall are both tubular and jointly define the annular oxygenation chamber therebetween, the chamber oxygenation has a cross-sectional area normal to its axis of between approximately 24 and 28 square centimeters.

17. The oxygenator according to claim 16, characterized in that the inner wall and the outer wall have a common axial length sufficient to ensure that a volume in the oxygenation chamber between the encapsulation compound at both axial ends is between approximately 200 and 240 ml .

18. The oxygenator according to claim 17, characterized in that the annular bundle comprises alternate layers of fiber mat, each layer of the fiber mat having a plurality of parallel fibers coupled, aligned so that the fibers extend helically around the fibers. the oxygenation chamber.

19. The oxygenator according to claim 18, characterized in that the fibers in the adjacent layers of the fiber mats extend helically in different rotational directions.

20. The oxygenator according to claim 17, characterized in that the fibers in the annular bundle or bundle have an aggregate volume which is between 0.5 and 0.6 of the volume in the oxygenation chamber between the encapsulation compound at both axial ends.

21. An oxygenator for blood of simplified construction, characterized in that it comprises: a rigid housing consisting essentially of five parts: an internal core having a radial bottom wall and a cylindrical wall; an outer cylindrical wall, concentric about the cylindrical wall of the inner core defining an annular oxygenation chamber therebetween, having a first axial end and a second axial end; a pair of end caps connected to opposite ends of the outer cylindrical wall; and an inlet cap for blood fixed or secured to the inner core, the inlet cap has a central blood inlet opening in communication with a space for blood distribution adjacent an axial end of the blood chamber. oxygenation and formed between the inner lid and the lower wall of the inner core, a plurality of inlets for blood in the inner core formed around the space for blood distribution in communication with the annular oxygenation chamber; a plurality of hollow, elongated semipermeable fibers, arranged or distributed in an annular bundle or bundle in the oxygenation chamber and fixed or secured - at both axial ends with an encapsulation compound, the opposite ends of the fibers are open to a space upper for the gas formed within the end caps outside the oxygenation chamber, the bundle or bundle substantially fills the oxygenation chamber with the fibers having spaces for blood flow therebetween; and a plurality of outlets for blood in the outer cylindrical wall formed around the annular oxygenation chamber on the axial end opposite the blood inlets, causing a generally axial flow of blood through the oxygenation chamber and between the hollow fibers.

22. The oxygenator according to claim 21, characterized in that the parts of the rigid housing are press-fitted together.

23. The oxygenator according to claim 21, characterized in that the parts of the rigid housing are joined together.

24. The oxygenator according to claim 23, characterized in that the rigid housing parts are welded by UV rays.

25. The oxygenator according to claim 21, characterized in that the fibers in the annular bundle or bundle comprise alternate layers of fiber mat, each layer of fiber mat having a plurality of parallel fibers coupled aligned so that the fibers extend helically around of the oxygenation chamber.

26. The oxygenator according to claim 25, characterized in that the fibers in the adjacent layers of the fiber mats extend helically in different rotational directions.

27. An extracorporeal system, characterized in that it comprises a combined blood / heat exchanger reservoir, having the heat exchange elements located in a separate heat exchange chamber, defined within the blood reservoir, and an outlet for the blood; a hollow fiber oxygenator having an inlet for blood connected to the blood outlet of the blood reservoir / heat exchanger, the oxygenator has a rigid housing defining an annular oxygenation chamber having a normal cross-sectional area to its axis between approximately 24 and 28 square centimeters and a first axial end and a second axial end; a central blood inlet opening in communication with a blood distribution space adjacent an axial end of the oxygenation chamber; a plurality of blood entrances in the housing formed around the annular oxygenation chamber in communication with the space for blood distribution; a plurality of blood outlets in the housing, formed around the annular oxygenation chamber on the axial end opposite the blood inlets; and a plurality of hollow, elongated semipermeable fibers, arranged or distributed in an annular bundle or bundle in the oxygenation chamber and fixed or secured at both axial ends with an encapsulation compound, the opposite ends of the fibers are open to a space For the gas formed in the housing outside the oxygenation chamber, the fibers have an aggregate volume which is between 0.5 and 0.6 of the volume in the oxygenation chamber between the encapsulation compound at both axial ends.

28. The system according to claim 27, characterized in that the heat exchange chamber houses a plurality of heat exchange elements and is defined by the guides extending down from a location in an upper portion of the storage chamber, the heat exchange chamber has an upper entrance open to an inlet for the venous blood and a lower entrance open towards the reservoir chamber so that the blood from the venous blood inlet must flow through the exchange chamber of the venous blood. heat before reaching the storage chamber.

29. The system according to claim 28, characterized in that the guides defining the heat exchange chamber are concentric tubular elements so that the heat exchange chamber is annular.

30. The system according to claim 29, characterized in that the elements for heat exchange comprise hollow tubes wound inside the annular heat exchange chamber.

31. The system according to claim 28, characterized in that the heat exchange chamber extends down a distance of about 3/4 of the height of the reservoir chamber.

32. The system according to claim 31, characterized in that it also includes a filter element placed between the outlet of the heat exchange chamber and the blood outlet, the filter element surrounding the heat exchange chamber and having a upper edge above the elevation, above the outlet of the chamber for heat exchange.

33. A reservoir for the blood / combined heat exchanger, characterized in that it comprises: a housing covered by a cover which jointly define an internal reservoir chamber; an entrance for the venous blood in the cover; a heat exchanger within the chamber that includes a plurality of elements for heat exchange; a chamber for the exchange of heat defined by the guides that closely surround the heat exchange elements and extend downwards from a location in an upper portion of the reservoir chamber, the chamber for heat exchange has an inlet upper open to the venous blood inlet and a lower outlet open to the reservoir chamber so that blood from the venous blood inlet must flow through the chamber for heat exchange before reaching the reservoir chamber; and an outlet for blood in a lower portion of the reservoir chamber.

34. The apparatus according to claim 33, characterized in that the guides defining the heat exchange chamber are concentric tubular elements so that the heat exchange chamber is annular.

35. The apparatus according to claim 34, characterized in that the heat exchange elements comprise hollow tubes wound inside the annular heat exchange chamber.

36. The apparatus according to claim 33, characterized in that the heat exchange chamber extends down a distance of approximately 3/4 parts the height of the chamber of the tank.

37. The apparatus according to claim 36, characterized in that it also includes a filter element placed between the outlet of the heat exchange chamber and the outlet of the tank chamber, the filter element surrounds the heat exchange chamber and has an edge top of the elevation, above the outlet of the heat exchange chamber.

38. The apparatus according to claim 37, characterized in that the filter element comprises a non-woven filter.

39. The apparatus according to claim 33, characterized in that it also includes a defoaming element placed inside the cover between the venous blood inlet and the chamber inlet for heat exchange, and at least one inlet for the cardiotomy fluid on the cover placed so that the cardiotomy fluid and the venous blood both pass through the defoaming element and into the entrance of the heat exchange chamber.

40. The apparatus according to claim 33, characterized in that it also includes a temperature sensor mounted on the cover to detect the temperature of the venous blood of the inlet, and a second temperature sensor mounted on the housing to detect the temperature of the inlet. the blood from the exit of the deposit chamber. SUMMARY OF THE INVENTION A membrane oxygenator of low priming volume (150) and an integrated heat exchanger / reservoir (24, 40) for use alone or in combination in an extracorporeal blood circuit. The oxygenator has a five-part, simple construction, which includes a housing (152) defining an annular oxygenation chamber (168) within which a plurality of hollow fibers (160) are arranged in an annular bundle or bundle with spaces for the flow between them. An inlet opening for blood and a manifold for supplying blood through a plurality of uniformly spaced inlet apertures to the oxygenation chamber, and the blood flows generally axially through the elongated annular chamber to a plurality of circumferentially spaced outlet openings in a uniform manner. The specific geometric relationships, a particular hollow fiber architecture, and the absence of a heat exchange function, all combine to reduce the volume of priming required by the oxygenator. The reservoir (24, 40) includes heat exchange coils (88) in an annular chamber that provide an efficient heat transfer function with a low priming volume requirement.