WO1993002722A1

WO1993002722A1 - Cardioplegia heat exchanger

Info

Publication number: WO1993002722A1
Application number: PCT/US1992/004138
Authority: WO
Inventors: Jeanne S. Pierson
Original assignee: Wiles, Terry, L.
Priority date: 1991-08-06
Filing date: 1992-05-15
Publication date: 1993-02-18
Also published as: AU2156692A

Abstract

A heat exchanger for medical use, in particular a cardioplegia heat exchanger is disclosed. In one embodiment, this heat exchanger comprises a heat transfer element (14) having a closed first end (54) and a substantially opposing second end (56) and being provided with at least one helical corrugation (42) extending between the first and second ends; an outer member (12) surrounding the at least one corrugation and together with the heat transfer element defining a first, helical flow path, the outer member having inlet and outlet apertures (28, 30) located adjacent opposite ends of the heat transfer partially; and an inner member (74) located at least partially within the heat transfer element and together with the heat transfer element defining a second helical flow path intermeshing with the first helical flow path, the inner member having inlet and outlet apertures located adjacent opposite ends of the heat transfer element.

Description

CARDIOPLEGIA HEAT EXCHANGER BACKGROUND OF THE INVENTION

The present invention relates generally to heat exchangers for medical purposes. More particularly, the invention relates to heat exchangers useful with support systems for cardiovascular surgery, for example, for cooling 5the heart during open heart surgery. Still more particularly, the invention relates to cardioplegia heat exchangers.

During open heart surgery, the blood of the patient is typically bypassed to an extracorporeal support system which substitutes for the pumping function of the heart and the lOoxygenation function of the lungs. During bypass, it is important that the heart not suffer from a deficiency of oxygen in the muscle tissue, commonly referred to as "ischemia". Avoidance of ischemia is generally accomplished by cooling the heart to a temperature which significantly

ISreduces its need for oxygen. This technique is known as "cardioplegia". Cooling of the heart is typically accomplished by introduction of a chilled fluid, which may be a synthetic cardioplegia solution, blood or a blood-based formulation. Use of blood or a blood-based formulation is

20believed to be advantageous, in that such compositions have enhanced carrying oxygen capability. Cooling of the cardioplegia composition has generally been accomplished by means of a heat exchanger which allows for cooling of the composition without compromising its sterility.

25 Cardioplegia delivery systems are illustrated in Carpenter et al U.S. Patent No. 4,416,280 and Wells et al U.S. Patent No. 4,512,163. The cardioplegia heat exchangers illustrated therein take the form of one or more metal tubes, located within an outer chamber. The cardioplegia composition 0is passed either through the tubes or through the chamber, with the coolant composition passed through the other of the tubes or he chamber. One commercially marketed cardioplegia heat exchanger is illustrated in Noda U.S. Patent No.

sui ΠTUTE SHEET 4,653,577. In this heat exchanger, a V-shaped metal tube having helical corrugations is located within a closely fitting plastic housing. Coolant travels through the smooth walled interior of the tube and the cardioplegia composition Spasses through the space between the corrugated tube and the plastic housing. Because of the closely fitting nature of the plastic housing, the cardioplegia composition follows a generally helical path defined by the corrugations of the tube. 0 Other heat exchangers used during cardiovascular surgery are found in the area of membrane and bubble oxygenators. Examples of such heat exchanges are illustrated in Kurata U.S. Patent No. 4,047,563; Servas et al U.S. Patent No. 4,559,999; Lewin U.S. Patent No. 4,065,254; Lee et al U.S. Patent No. 4,622,140; and Leonard et al U.S. Patent No. 4,735,775. SUMMARY OF THE INVENTION

The present invention provides heat exchangers of simple construction and high efficiency. This simplicity of construction renders the present heat exchangers relatively inexpensive to produce, which is a significant advantage in those applications in which the exchangers are intended to be manufactured as a one use disposable unit or as a unit intended to be used only a few times. In addition, the present heat exchangers are preferably structured to reduce the risks of harmful leaks and/or coolant contamination of the cardioplegia composition with the medium, for example, water, being used to cool the cardioplegia composition.

In one broad aspect, the present invention is directed to heat exchangers for medical use which comprise a heat transfer element, an outer member and an inner member. The heat transfer element, preferably comprising a medically acceptable metal, has a closed first end and a substantially opposing second end. The heat transfer element is provided with at least one helical corrugation which extends between the first and second ends of a heat transfer element. The outer member.

SUBSTITUTESHEET preferably comprising a transparent material, surrounds the corrugation or corrugations of the heat transfer element. This outer member, together with the heat transfer element, in particular the corrugation or corrugations of the heat 5transfer element, define a first helical flow path. The outer element also includes inlet and outlet apertures or orifices located adjacent opposite ends of the heat transfer element through which flowable material may enter and exit the first helical flow path, respectively. The inner element is located lOat least partially within the heat transfer element. This inner member, together with the heat transfer element, in particular the corrugation or corrugations of the heat transfer element, defines a second helical flow path which intermeshes with the first helical flow path. The inner lδmember includes inlet and outlet apertures or orifices located adjacent opposite ends of the heat transfer element through which flowable material may enter and exit the second helical flow path, respectively.

In this arrangement, a first flowable material, for

20example, a cardioplegia composition, flows in the first helical flow path. A second flowable material, for example, water or other coolant medium, flows through the second helical flow path. Heat is exchanged across the heat transfer element as the materials flow in the helical flow paths. 5 The outer member and heat transfer element preferably define an internal chamber which preferably extends above the inlet aperture of the outer member and functions as a bubble chamber. The use of a bubble chamber minimizes the amount of gaseous material which is contained in the material, for 0example, a cardioplegia composition, flowing through the first helical flow path. A vent is preferably provided in fluid communication with the internal chamber so that gaseous

SUBSTITUTESHEET material can be removed from the internal chamber. The vent and portion of the internal chamber defined by the outer member are preferably formed as parts of a single piece outer member.

5 Preferably, the inlet and outlet apertures of the inner and outer members are situated so that the general direction of the flow through the first helical flow path is opposite the general direction of flow through the second helical flow path. In this manner, counter current heat exchange is lOprovided which enhances the heat exchange efficiency of the present system.

In a particularly useful embodiment, the present heat exchangers further comprise a first seal element located in contact with both the outer member and the heat transfer lδelement. This first seal element, preferably comprising an O- ring, is adapted to prevent liquid from the inlet aperture of the outer member from exiting the first helical flow path other than through the outlet aperture of the outer member. The first seal element is preferably positioned so that any 0fluid from the first helical flow path which flows past it is directed outside the heat exchanger. The present heat exchangers may include a second seal element located in contact with both the inner member and the heat transfer element. This second seal element, preferably comprising an 50-ring, is adapted to prevent fluid from the inlet aperture of the inner member from exiting the second helical flow path other than through the outlet aperture of the inner member. The second seal element is preferably positioned so that any fluid from the second helical flow path which flows past the 0second seal element is directed outside the heat exchanger. The first and second seal elements are more preferably used together and effectively prevent cross contamination of the flowable materials in the first and second helical flow paths. Even if one or both of the seal elements fail, the 5material which escapes either of the helical flow paths is

SUBSTITUTESHEET preferably removed from the heat exchanger rather than contaminating the material in the other of the flow paths. This is a substantial advantage and acts to maintain the integrity of the materials, in particular the cardioplegia δcomposition, being processed.

The present heat exchangers may include one or more ports or other locations through or at which one or more parameters of the flowable materials in the exchangers can be determined. For example, a pressure port may be located at or near the lOdownstream terminus of the first helical flow path through which the pressure of the flowable material at or near the downstream terminus of the first helical flow path can be determined. Also, a temperature port may be provided at or near the downstream terminus of the first helical flow path lδthrough which the temperature of the fluid at or near the downstream terminus of the first helical flow path can be determined.

The heat exchangers preferably further comprise an inlet in fluid communication with the inlet aperture of the inner

20member to provide a path for material to flow through prior to being introduced into the second helical flow path. An outlet is preferably included and is in fluid communication with the outlet aperture of the inner member and provides a path for material to flow through after passing through the outlet 5aperture of the inner member.

These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like 0reference numerals.

Brief Description of the Drawings

Fig. 1 is a bottom front view, in perspective, of one embodiment of the heat exchanger of the present invention.

Fig. 2 is a plan view of the bottom side of the 5embodiment shown in Fig. 1.

E SHEET Fig. 3 is a cross sectional view taken generally along line 3-3 of Fig. 2.

Fig. 4 is cross-sectional a view taken generally along line 4-4 of Fig. 2. 5 Fig. 5 is a partial cross-sectional view taken generally along line 5-5 of Fig.2. Detailed Description of the Drawings

Referring now to the drawings, a cardioplegia heat exchanger, shown generally at 10, includes a transparent outer cover 12, a metal heat transfer 14, an inner component 16, and a plug 18.

Transparent outer cover 12 includes a sidewall 18 in the general shape of a truncated right cylindrical cone, a first end wall 20 and an opposing open end 22. Transparent outer cover 12 may be considered a housing for heat exchanger 10. 5Transparent outer cover 12 includes an inlet opening 24 and an outlet opening 26. Inlet opening 24 is defined by an inlet port 28 which is located near the first end 20 of outer cover 12. Outlet opening 26 is defined by outlet port 30 which is located near second end 22. Outer cover 12 also includes a lOtemperature port 30 and a pressure port 32. The temperature port 30 is configured so that a conventional temperature sensor, such as a thermocouple, a thermistor, a thermometer or the like, can be inserted therein to determine the temperature of the flowable material in the space adjacent the inner 5surface 34 of outer cover 12 near the second end 22 of the outer cover. Pressure port 32 is structured so that a conventional pressure sensing device, such as a probe of a pressure transducer or the like, can be inserted therein to determine the pressure of the flowable material in contact 0with the inner wall 34 of outer cover 12 near the second end 22 of outer cover. A solid barrier is maintained between the

SUBSTITUTESHEET temperature and pressure sensors in the temperature and pressure ports 30 and 32, respectively, and the flowable material in contact with inner surface 34 so that the sterility of such flowable material can be maintained. 5 In addition, outer cover 12 is structured to define a portion of an interior chamber 36 and includes a gas port 38 which defines a gas vent 40. Internal chamber 36 is located near the first end 20 of outer cover 12 and, in fact, is partially defined by first end 20.

10 The portion 37 of transparent outer cover 12 adjacent open end 22 includes a series of four (4) segments 39 which have a degree of flexibility. Plug 18 is structured to be snap fitted into transparent outer cover 12 and to be held in place in the outer cover by the cooperative action of the segments

1539.

Although transparent outer cover 12 can be assembled from a plurality of components, it is preferred that the outer transparent cover be made as a single, integral unit. For example, the transparent outer cover 12 may be molded, or

20otherwise shaped, from a transparent polymeric material, such as polycarbonates or acrylics.

In any event, the transparent outer cover 12 is constructed of a medically acceptable material. By "medically acceptable" is meant that the material in question is such as

25to have no undue detrimental effect on the flowable material to which it is exposed and on the medical patient who is exposed to such flowable material.

The metal heat transfer element 14 includes a series of five separate helical corrugations identified as 42, 44, 46,

3048 and 50. For clarity of description, these corrugations will hereinafter be referred to as corrugations 42. Corrugations 42 are provided in the sidewall 52 of metal heat transfer element 14 and extend between a first closed end 54 and a second open end 56 of the metal heat transfer element.

35The corrugations 42 do not extend to either first end 54 or

SUBSTITUTESHEET second end 56. The general shape of sidewall 52 of heat transfer element 14 is a truncated cone and is sized so as to fit into outer cover 12 so that portions of the outer surface 53 of sidewall 52 are in contact with inner surface 34 of the 5outer cover. This intermittent contact between outer surface 53 and inner surface 34 together with corrugations 42 forms a first fluid flow path which is in fluid communication with inlet opening 24 and outlet opening 26 of outer cover 12. This first flow path, shown generally at 60, is helical in lOconfiguration. Heat transfer element 14 is made of a medically acceptable metal, such as surgical grade stainless steel.

Heat transfer element 14 is preferably fabricated without seams or welds. Such construction provides for reduced risks 5of flowable material leaks, and in addition, maintains the integrity and sterility of the first fluid flow path 60. Heat transfer element 14 can be produced using conventional metal forming techniques to provide the desired corrugations 42. For example, the corrugations can be formed using a lathe or 0hydroforming employing water pressure. In one embodiment, heat transfer element 14 is made of aluminum which is anodized to reduce or inhibit oxidation.

Inner component 16 includes a side wall 63 which has a general configuration in the shape of a truncated cone. Inner 5component 16 is configured to fit within metal heat transfer element 14 so that portions of the inner surface 64 of sidewall 52 come in contact with the outer surface 65 of the side wall 63 of inner component 16. This intermittent contact between inner surface 64 and outer surface 65, together with 0the corrugations produce a second fluid flow path shown generally at 62, which is helical in configuration and intermeshes with first helical flow path 60.

Inner component 16 includes a first end 66 and an opposing second end 68. Sidewall 63 includes an inlet 5aperture 70 which provides a path for flowable material, for

SUBSTITUTESHEET example, liquid water, to enter second fluid flow path 62. The flowable material which passes through inlet aperture 70 is able to reach all parts of second fluid path 62. The first end 66 of inner component 14 includes an outlet aperture 72 Sthrough which the flowable material from second fluid flow path 62 exits. Inner component 14 includes a wall 74 which extends inwardly from the first end 66 and divides the interior space defined by first end 66, sidewall 63 and second end 68 of the inner component 16 into an inlet lumen 75 and an lOoutlet lumen 76.

A series of three projections 78 extend outwardly from the first end 66 of inner component 16 (only one of such projections 78 are shown) . Such projections 78 are spaced equidistantly about the first end of the inner component 16

15and act to maintain a space 80 between the first end of the inner component 16 and the closed first end 54 of heat transfer element 14. This allows for the flow of flowable material from the second fluid path 62 into and through outlet aperture 72. 0 Plug 18 includes a fluid inlet 80 and a fluid outlet 82. Fluid inlet 80 provides a passage through which flowable material passes prior to passing through inlet aperture 70 and second fluid flow path 62. Fluid inlet 80 empties into first lumen 75. Fluid outlet 82 is in fluid communication with 5second lumen 76 and provides a path through which flowable material from outlet aperture 72 flows to exit heat exchanger 10. A first 0-ring element 84 is positioned in contact with transparent outer cover 12, metal heat transfer element 14 and plug 18 and acts to seal first fluid flow path 60 so 0that no liquid passes from first fluid flow path 60 out of heat exchanger 10 other than through outlet opening 26.

A second 0-ring element 86 is positioned in contact with heat transfer element 14, inner component 16 and plug 18 and acts to seal second fluid flow path 62 and prevent any fluid

SUBSTITUTESHEET from escaping heat exchanger 10 from the second fluid flow path other than through outlet aperture 72 and fluid outlet 82.

Both first 0-ring element 84 and second O-ring element 86 5are positioned so that in the event that any fluid which passes either of these seal elements is directed to the atmosphere rather than into the other of the helical flow paths. In this manner, the risks of contaminating the flowable materials in either of the fluid flow paths, and lOparticularly the flowable material in the first helical flow path 60, are reduced. These seal elements are best described with reference to Fig. 5. Any fluid which passes by either first O-ring element 84 or second O-ring element 86 enters fluid space 90, which extends completely around heat exchanger 1510. Two vent holes 92 in plug 18 are in fluid communication with fluid space and provide passageways for any fluid in fluid space 90 to exit heat exchanger 10 and be vented to the atmosphere.

Each of the inlet port 28, the outlet port 30 and the gas 0port 38 of heat exchanger 10 may be fitted with conventional fittings to provide for material flow to and from the heat exchanger 10 so that the heat exchanger can act as an effective part of an overall medical treatment, e.g., cardioplegia, system. 5 Transparent outer cover 12 includes an outwardly extending ridge 94 which can function as a support for heat exchanger 10. That is, ridge 94 can be mechanically secured to a stationary object so as to secure heat exchanger 10 in place. Outer cover 12 is transparent so that one can visually 0monitor the flow of the flowable material, e.g., cardioplegia composition, through the first fluid flow path 60.

Heat exchanger 10 may be assembled in the following manner. With all the component parts available, the heat metal transfer element 14 is placed inside the outer cover 12 5so that the closed end 54 extends toward the internal chamber

SUBSTITUTESHEET 36. Next, the inner component 16 is placed within the space defined by heat transfer element 14. The first and second O- ring elements 84 and 86 are appropriately placed on plug 18, which is then fitted into the open end of the partially δcompleted assembly and, using segments 39, snapped and held in place. Such snapping mechanism has been found to provide structural integrity to heat exchanger 10. Thus, there is no need for the use of adhesives or other procedures, e.g., sonic welding and the like, to assemble the present system. This lOsimple heat exchanger construction and assembly procedure are important advantages of the present invention.

Heat exchanger 10 functions as follows. The assembled heat exchanger 10 is appropriately connected to water inlet and drain lines, cardioplegia composition inlet and outlet

151ines and vent lines. Also, a temperature sensing device is provided in temperature port 30 and a pressure sensing device is provided in pressure port 32. At this point, the heat exchanger 10 is ready to be used.

Water is provided through fluid inlet 80 and passes

20through inlet aperture 70 into the second fluid flow path 62 and exits through outlet aperture 72 into second lumen 76 and then exits heat exchanger 10 through fluid outlet 82. Cardioplegia composition enters through inlet opening 24 and passes into and through first fluid flow path 60 and exits 5heat exchanger 10 through outlet opening 26. Gaseous material which may be included in the cardioplegia composition is separated from the composition in internal chamber 36 and exits heat exchanger 10 through gas vent 40. As the water flows through second fluid flow path 62 and the cardioplegia 0composition flows through first fluid flow path 60, heat is transferred from the cardioplegia composition to the water which reduces the temperature of the cardioplegia composition, which is used downstream from the heat exchanger 10. The flow

SUBSTITUTESHEET rates and/or the temperature of the water in the second fluid flow path 62 can be controlled so as to provide the desired outlet temperature of the cardioplegia composition from first fluid flow path 60. 5 If desired or necessary, a conventional liquid crystal temperature indicating label can be included in or near the first fluid flow path 60 at or near the terminus the first fluid low path so as to provide an indication of the temperature of the cardioplegia composition leaving heat 0exchanger 10.

Heat exchanger 10 is sized and configured to be capable of providing 1000 ml. per minute of cooled cardioplegia composition for treating a medical patient. At a cardioplegia composition flow rate of 500 ml. per minute, the cardioplegia composition pressure drop across heat exchanger 10 is about 100 mm Hg. With coolant water being supplied at 2°C and inlet temperature of the cardioplegia composition at 25°C, the heat exchanger 10 can provide cardioplegia composition at the rate of 1000 ml. per minute and having a temperature of 14°C. The simple construction of heat exchanger 10 provides substantial manufacturing and cost benefits without compromising heat exchange efficiency or effectiveness. The present corrugations very effectively provide the necessary heat exchange surface area with very low priming volume. The present heat exchanger provides the desired heat exchange while reducing the risks of leaks, loss of sterility or contamination of the cardioplegia composition with the coolant.

While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

SUBSTITUTESHEET

Claims

WHAT IS CLAIMED IS;

1. A heat exchanger for medical use comprising: a heat transfer element having a closed first end and a substantially opposing second end and being provided with at least one helical corrugation extending between said first and 5second ends; an outer member surrounding said at least one corrugation and together with said heat transfer element defining a first, helical flow path, said outer member having inlet and outlet apertures located adjacent opposite ends of lOsaid heat transfer element; and an inner member located at least partially within said heat transfer element and together with said heat transfer element defining a second helical flow path intermeshing with said first helical flow path, said inner 15member having inlet and outlet apertures located adjacent opposite ends of said heat transfer element.

2. The heat exchanger of claim 1 wherein said outer member includes an end adjacent said closed first end of said heat transfer element and defines an internal chamber which extends above said outlet aperture of said outer member and

5functions as a bubble trap.

3. The heat exchanger of claim 2 which further comprises a vent in fluid communication with said internal chamber and through which gaseous material exits said internal chamber.

4. The head exchanger of claim 1 wherein said heat transfer element comprises a medically acceptable metal.

SUBSTITUTESHEET

5. The heat exchanger of claim 1 wherein said outer member comprises a transparent material whereby flow of fluid through said space between said outer member and said heat transfer element may be monitored visually.

6. The heat exchanger of claim 1 wherein said at least one corrugation is located spaced apart from said closed first end and said second end of said heat transfer element.

7. The heat exchanger of claim 1 which further comprises a first seal element located in contact with both said outer member and said heat transfer element, said first seal element adapted to prevent liquid from said inlet

Saperture of said outer member from exiting said first helical flow path other than through said outlet aperture of said outer member.

8. The heat exchanger of claim 7 wherein said first seal element is positioned so that any fluid from said first helical flow path which flows past said first seal element is directed outside said heat exchanger.

9. The heat exchanger of claim 1 which further comprises a second seal element located in contact with both said inner member and said heat transfer element, said second seal element adapted to prevent fluid from said inlet aperture of said inner member from exiting said second helical flow path other than through said outlet apertures of said inner member.

10. The heat exchanger of claim 9 wherein said second seal element is positioned so that any fluid from said second helical flow path which flows past said second seal element is directed outside said heat exchanger.

SUBSTITUTESHEET

11. The heat exchanger of claim 7 which further comprises a second seal element located in contact with both said inner member and said heat transfer element, said second seal element adapted to prevent fluid from said inlet aperture

5of said inner member from exiting said second helical fluid flow path other than through said outlet aperture of said inner member.

12. The heat exchange of claim 11 wherein each of said first and second seal elements comprises an 0-ring.

13. The heat exchanger of claim 1 wherein said inlet and outlet apertures of said inner and outer members are situated so that the general direction of flow through said first helical flow path is opposite to the general direction of flow

5through said second helical flow path.

14. The heat exchanger of claim 1 wherein said outlet aperture of said inner member is located in one end of said inner member.

15. The heat exchanger of claim 14 wherein said one end of said inner member in which is located said outlet aperture is otherwise closed.

16. The heat exchanger of claim 1 which further comprises at least one of the following: a pressure port located at or near the downstream terminus of said second helical flow path through which the pressure of the fluid at

5or near the downstream terminus of said second helical flow path can be determined; and a temperature port located at or near the downstream terminus of said second helical flow path through which the temperature of the fluid at or near the downstream terminus of said second helical flow path can be lOdetermined.

SUBSTITUTESHEET

17. The heat exchanger of claim 1 which further comprises an inlet in fluid communication with said inlet aperture of said inner member to provide a path for fluid to pass through prior to being introduced into said second Shelical flow path; and an outlet in fluid communication with said outlet aperture of said inner member to provide a path for fluid to pass through after passing through said outlet aperture of said inner member.

18. The heat exchanger of claim 1 wherein said at least one helical corrugation is in contact with both said outer member and said inner member.

19. The heat exchanger of claim 1 wherein said heat transfer element includes a sidewall in the general shape of a truncated cone.

20. The heat exchanger of claim 1 wherein said heat transfer element is free of welds and seams.

21. A blood cardioplegia heat exchanger comprising: a metal heat transfer element having a closed first end and a substantially opposing second end and being provided with at least one helical corrugation extending between said Sfirst and second ends; a transparent outer member surrounding said at least one corrugation and together with said metal heat transfer element defining a first helical flow path adapted for the flow of blood or a blood-based fluid therethrough, said lOtransparent outer member having inlet and outlet apertures located at or near opposite ends of said metal heat transfer element and adapted to provide fluid entrance to and egress from, respectively, said first helical flow path;

SUBSTITUTESHEET an inner member located at least partially within said metal heat transfer element and together with said heat transfer element defining a second helical flow path intermeshing with said first helical flow path, said inner δmember having inlet and outlet apertures located at or near opposite ends of said metal heat transfer element; a first seal element located in contact with both said transparent outer member and said metal heat transfer element, said first seal element adapted to prevent liquid lOfrom said inlet aperture of said transparent outer member exiting said first helical flow path other than through said outlet aperture of said transparent outer member; and a second seal element located in contact with both said inner member and said metal heat transfer element, said 15second seal element adapted to prevent fluid from said inlet aperture of said inner member from exiting said second helical flow path other than through said inlet and said outlet aperture of said inner member.

22. The heat exchanger of claim 21 wherein said at least one helical corrugation is in contact with both said transparent outer member and said inner member.

23. The heat exchanger of claim 21 wherein said metal heat transfer element includes a sidewall in the general shape of a truncated cone.

SUBSTITUTESHEET