CA2470150A1 - Selective organ hypothermia method and apparatus - Google Patents
Selective organ hypothermia method and apparatus Download PDFInfo
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- CA2470150A1 CA2470150A1 CA002470150A CA2470150A CA2470150A1 CA 2470150 A1 CA2470150 A1 CA 2470150A1 CA 002470150 A CA002470150 A CA 002470150A CA 2470150 A CA2470150 A CA 2470150A CA 2470150 A1 CA2470150 A1 CA 2470150A1
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- Prior art keywords
- heat transfer
- working fluid
- catheter
- transfer element
- supply conduit
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/02—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques
- A61B2018/0212—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques using an instrument inserted into a body lumen, e.g. catheter
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/02—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by cooling, e.g. cryogenic techniques
- A61B2018/0231—Characteristics of handpieces or probes
- A61B2018/0262—Characteristics of handpieces or probes using a circulating cryogenic fluid
Abstract
The present invention is a method, and apparatus for performing hypothermia of a selected body organ without significant effect on surrounding organs or other tissue. A
flexible catheter (10) is inserted through the vascular system of a patient to place the distal tip (26) of the catheter in an artery feeding the selected organ. A compressed refrigerant is pumped through the catheter to an expansion element (22) near the distal tip of the catheter, where the refrigerant vaporizes, and expands to cool a flexible heat transfer clement (24) in the distal tip of the catheter. The heat transfer element cools the blood flowing through the artery to cool the selected organ, distal to the tip of the catheter
flexible catheter (10) is inserted through the vascular system of a patient to place the distal tip (26) of the catheter in an artery feeding the selected organ. A compressed refrigerant is pumped through the catheter to an expansion element (22) near the distal tip of the catheter, where the refrigerant vaporizes, and expands to cool a flexible heat transfer clement (24) in the distal tip of the catheter. The heat transfer element cools the blood flowing through the artery to cool the selected organ, distal to the tip of the catheter
Description
TITIrE OF 'FI-IE IN'JEhITIOIrI
Selective Organ Hypothermia l~iethod rind Apparatus This is a divisional of Canadian Patent Application 2,318,084 filed January 21, I 999.
EACIt~iItOI_TNO OF THE INVEN'I"ION
s Field ~f the Invention - The current invention relates to selective cooling, or hypothermia, of an organ, such as the brain, by cooling the blood flowing into the ~rgan. This cooling can protect the tissue from injury caused by anoxia or trauma.
Eackground Information - Organs of the human body, such as the brain, kidney, and heart, are maintained at a constant temperature of approximately 37° C.
Cooling of organs below 35° C is known to provide cellular protection from anoxic damage caused by a disruption of blood supply, or by traiuxta. Cof~ling can also reduce swelling associated with these injuries.
Hypothermia is currently utilized in mediciine and is sometimes performed t~
pr~tect the brain from injury. Cooling of the brain is generally acdcoplished through ~ s whole body cooling to create a condition of total body hypothermia in the range of 20°
to 30° C. This cooling is accomplished by immersing the patient in ice, by using cooling blankets, or by cooling the blood flowing externally through a .
cardiopulmonary bypass machine. TJ. S. Pat. No. 3,425,419 to I)ato and Z.J. S.
Pate No.
5,486,208 to Csinsburg disclose catheters for cooling the blood to create total body 2o hypothermia However, they rely ora circulating a c~ld fluid to produce cooling. This is unsuitable for selective organ hypothermia, because cooli:r~g of tt~e entire catheter by the cold fluid on its way to the organ would ultimately result in non-selective, or total body, cooling.
Total body. hypothermia to provide organ protection has a number of 2s drawbacks. First, it creates cardiovascular problems, such as cardiac arrhythmias, reduced cardiac output, and increased systemic vascular eesistanee. These side e~'ects can result in organ damage. These side effects are believed, to be c~~used reflexively in response to the reduction in core body temperature. Seconst, total body hypothermia is difficult to administer. Irr~nersing a patient in ice water clearly has its associated 3a problems. Placement ors cardiopulmonary bypass requires surgical intervention and specialists.to operate the machine, and it is associated with a number of complications including bleeding and volume overload. Third, the tine required to reduce the body CA 02470150 2004-07-02 _. .
ENO 49137226 P~'r'11C3S99/fl1275 temperature and the organ temperature is prolonged. l~inimi2ing the ti~tae between injury and the onset of cooling has been shown to produce better clinical outeomes.
Some physicians have in~rnersed the patient's head in ice to pmvide brain cooling. There are also cooling helmets, or head gear, to perform the same.
This 5 approach suffers frogn the problems of slow cool down and poor temperature control due to the temperature gradient that must be established externally to internally. It has also been shown fleet complications associated with total body cooling, such as arrhythmia and decreased cardiac output, can also be caused by cooling of the face and head only.
to Selective organ hypothermia has been studied by Schwartz, et, at.
'lJtilizing baboons, blood was circulated and cooled externally #~°oans the body via the femoral artery and returned to the body through the carotid artery. "This study showed that the brain could be selectively cooled to temperatures of 20° ~ without reducing the temperature of the entire body. Subsequently, cardiovascular complications associated IS total body hypothermia did not occur. However, external circulation of the blood for cooling is not a practical approach for the treatment of humans. The risks of infection, bleeding, and fluid imbalance are great. Also, at least two arterial vessels must be punctured and can..°zulated. Further, percutaneous cannulation of the caroeid artery is very difficult and potentially fatal, due to the associated arterial wall trauma. Also, 2a this method could not be used to cool organs such as the kidneys, where the renal arteries cannot be directly cannulated pereutaneously.
Selective organ hypothermia has also been attempted by perfusing the organ with a cold solution, such as saline or perflourocarbons. This is cozncnonly done to protect the heart during heart surgery and is refexred to as cardioplegia.
This procedure ~s has a number of drawbaclCS, including limited time of administration due to excessive volume accumulation, cost and inconvenience of maintaining the perfiasate, and lack of effectiveness due to temperature dilution from the blood. Temperature dilution by the blood is a particular problem in high blood flow organs such as the brain.
For cardioplegia, the blood flow to the heart is minimized, and thei°efore this effect is 30 minimized.
lntravascular, selective organ hypothermia, created by ~.,ooling the blood flowing into the organ, is the ideal method. First, because only the target organ is ,.
Wt's 99137226 P~'TlUS99/0~2'75 cooled, complications associated with total body hy';pothermia are avoided.
Second, because the blood is cooled intravasculariy, or in situ, problems associated with external circulation of'blood are eliminated. Third, only a single puncture and arterial vessel cannulation is required, and it can be performed at an easily accessible artery s such as the femoral, subclavian, or brachial. Fourth, cold perfusate solutions are not required, thus eliminating problems with excessive fluid accumulation. This also eliminates the time, cost, and handling issues associated with providing and maintaining cold per~usate solution. Fifth, rapid ccsoling can be achieved.
Sixth, precise temperature contxol is possible.
o Previous inventors have disclosed the circulation of a cold fluid to produce total body hypotherm$a, by placing a probe into a rna~or vessel of the body.
This approach is entirely unfeasible when considering selective organ hypothermia, as will be demonstrated belo~~.
The important factor related to catheter development for selective organ 15 hypothermia is the small size of the typical feeding artery, and the need to prevent a significant reduction in blood flow when the catheter is placed in the artery.
h significant reduction it blood flow would result in ischemic organ damage.
While the diameter of the mayor ~~essels of the body, such as the vane cave and aorta, are as large as I 5 to 20 mm., the diameter of the feeding artery of an organ is typically only 4.0 to 20 8.0 mm. Thus, a catheter residing in one of these arteries cannot be much larger than 2.0 to 3.0 mm. in outside diameter. It is not practical, to con:.~aruct a selective organ hypothermia catheter of this small size using the circulation of cold water or other fluid. Using the brain as an example, this point will be illustrated.
The brain typically has a blood flow rate of approximately 500 to 7~0 cc/min.
2s Two carotid arteries feed this blood supply to the brain. The internal carotid is a small diameter artery that branches off of the common carotid near the angle of the jaw. To cool the brain, it is important to place some of the cooling portion of the catheter into the internal carotid artery, so as to mimimize cooling of the face via the external carotid, since face cooling can result in complications, as discussed above.
It would 3o be desirable to cool the blood in this artery down to 32°C, to achieve the desired cooling of the brain. T~ cool the blood in this artery by a SC° drop, from 37°C down to 32°C, requires between 100 and 150 watts ofrefrigeration po~~rer.
Selective Organ Hypothermia l~iethod rind Apparatus This is a divisional of Canadian Patent Application 2,318,084 filed January 21, I 999.
EACIt~iItOI_TNO OF THE INVEN'I"ION
s Field ~f the Invention - The current invention relates to selective cooling, or hypothermia, of an organ, such as the brain, by cooling the blood flowing into the ~rgan. This cooling can protect the tissue from injury caused by anoxia or trauma.
Eackground Information - Organs of the human body, such as the brain, kidney, and heart, are maintained at a constant temperature of approximately 37° C.
Cooling of organs below 35° C is known to provide cellular protection from anoxic damage caused by a disruption of blood supply, or by traiuxta. Cof~ling can also reduce swelling associated with these injuries.
Hypothermia is currently utilized in mediciine and is sometimes performed t~
pr~tect the brain from injury. Cooling of the brain is generally acdcoplished through ~ s whole body cooling to create a condition of total body hypothermia in the range of 20°
to 30° C. This cooling is accomplished by immersing the patient in ice, by using cooling blankets, or by cooling the blood flowing externally through a .
cardiopulmonary bypass machine. TJ. S. Pat. No. 3,425,419 to I)ato and Z.J. S.
Pate No.
5,486,208 to Csinsburg disclose catheters for cooling the blood to create total body 2o hypothermia However, they rely ora circulating a c~ld fluid to produce cooling. This is unsuitable for selective organ hypothermia, because cooli:r~g of tt~e entire catheter by the cold fluid on its way to the organ would ultimately result in non-selective, or total body, cooling.
Total body. hypothermia to provide organ protection has a number of 2s drawbacks. First, it creates cardiovascular problems, such as cardiac arrhythmias, reduced cardiac output, and increased systemic vascular eesistanee. These side e~'ects can result in organ damage. These side effects are believed, to be c~~used reflexively in response to the reduction in core body temperature. Seconst, total body hypothermia is difficult to administer. Irr~nersing a patient in ice water clearly has its associated 3a problems. Placement ors cardiopulmonary bypass requires surgical intervention and specialists.to operate the machine, and it is associated with a number of complications including bleeding and volume overload. Third, the tine required to reduce the body CA 02470150 2004-07-02 _. .
ENO 49137226 P~'r'11C3S99/fl1275 temperature and the organ temperature is prolonged. l~inimi2ing the ti~tae between injury and the onset of cooling has been shown to produce better clinical outeomes.
Some physicians have in~rnersed the patient's head in ice to pmvide brain cooling. There are also cooling helmets, or head gear, to perform the same.
This 5 approach suffers frogn the problems of slow cool down and poor temperature control due to the temperature gradient that must be established externally to internally. It has also been shown fleet complications associated with total body cooling, such as arrhythmia and decreased cardiac output, can also be caused by cooling of the face and head only.
to Selective organ hypothermia has been studied by Schwartz, et, at.
'lJtilizing baboons, blood was circulated and cooled externally #~°oans the body via the femoral artery and returned to the body through the carotid artery. "This study showed that the brain could be selectively cooled to temperatures of 20° ~ without reducing the temperature of the entire body. Subsequently, cardiovascular complications associated IS total body hypothermia did not occur. However, external circulation of the blood for cooling is not a practical approach for the treatment of humans. The risks of infection, bleeding, and fluid imbalance are great. Also, at least two arterial vessels must be punctured and can..°zulated. Further, percutaneous cannulation of the caroeid artery is very difficult and potentially fatal, due to the associated arterial wall trauma. Also, 2a this method could not be used to cool organs such as the kidneys, where the renal arteries cannot be directly cannulated pereutaneously.
Selective organ hypothermia has also been attempted by perfusing the organ with a cold solution, such as saline or perflourocarbons. This is cozncnonly done to protect the heart during heart surgery and is refexred to as cardioplegia.
This procedure ~s has a number of drawbaclCS, including limited time of administration due to excessive volume accumulation, cost and inconvenience of maintaining the perfiasate, and lack of effectiveness due to temperature dilution from the blood. Temperature dilution by the blood is a particular problem in high blood flow organs such as the brain.
For cardioplegia, the blood flow to the heart is minimized, and thei°efore this effect is 30 minimized.
lntravascular, selective organ hypothermia, created by ~.,ooling the blood flowing into the organ, is the ideal method. First, because only the target organ is ,.
Wt's 99137226 P~'TlUS99/0~2'75 cooled, complications associated with total body hy';pothermia are avoided.
Second, because the blood is cooled intravasculariy, or in situ, problems associated with external circulation of'blood are eliminated. Third, only a single puncture and arterial vessel cannulation is required, and it can be performed at an easily accessible artery s such as the femoral, subclavian, or brachial. Fourth, cold perfusate solutions are not required, thus eliminating problems with excessive fluid accumulation. This also eliminates the time, cost, and handling issues associated with providing and maintaining cold per~usate solution. Fifth, rapid ccsoling can be achieved.
Sixth, precise temperature contxol is possible.
o Previous inventors have disclosed the circulation of a cold fluid to produce total body hypotherm$a, by placing a probe into a rna~or vessel of the body.
This approach is entirely unfeasible when considering selective organ hypothermia, as will be demonstrated belo~~.
The important factor related to catheter development for selective organ 15 hypothermia is the small size of the typical feeding artery, and the need to prevent a significant reduction in blood flow when the catheter is placed in the artery.
h significant reduction it blood flow would result in ischemic organ damage.
While the diameter of the mayor ~~essels of the body, such as the vane cave and aorta, are as large as I 5 to 20 mm., the diameter of the feeding artery of an organ is typically only 4.0 to 20 8.0 mm. Thus, a catheter residing in one of these arteries cannot be much larger than 2.0 to 3.0 mm. in outside diameter. It is not practical, to con:.~aruct a selective organ hypothermia catheter of this small size using the circulation of cold water or other fluid. Using the brain as an example, this point will be illustrated.
The brain typically has a blood flow rate of approximately 500 to 7~0 cc/min.
2s Two carotid arteries feed this blood supply to the brain. The internal carotid is a small diameter artery that branches off of the common carotid near the angle of the jaw. To cool the brain, it is important to place some of the cooling portion of the catheter into the internal carotid artery, so as to mimimize cooling of the face via the external carotid, since face cooling can result in complications, as discussed above.
It would 3o be desirable to cool the blood in this artery down to 32°C, to achieve the desired cooling of the brain. T~ cool the blood in this artery by a SC° drop, from 37°C down to 32°C, requires between 100 and 150 watts ofrefrigeration po~~rer.
w0 99/37226 PC'T/tJS99/U1275 In order to reach the internal carotid artery from a femoral insertion point, an overall catheter length of approximately 100 cm. would be required. To avoid undue blockage of the blood flow, the outside diameter of the catheter can not exceed approximately 2 mm. Assuming a coaxial construction, this limitation in diameter 5 would dictate an internal supply tube of about 0.70 nlan. diameter, with return flow being between the internal tube and the external tube.
A catheter based on the circulation of water or saline operates on the principle of transferring heat frogs the blood to raise the temperature of the water.
Rather than absorbing heat by boiling at a constant temperature like a freon, water must warm up ~ o to absorb heat and produce cooling. f~Iater flowing at the rate ~~f 5.0 gramslsec, at an initial temperature of 0°C and warming up to 5°C, can absorb 100 watts of heat. Thus, the outer surface of the heat transfer element could onl~r '~ maintained at 5°C, instead of 0°C. This will require the heat transfer element to have a surface area of approximately 1225 °n2. If a catheter of approximately 2.0 mm. diameter is 1 s assumed, the length of the heat transfer element would have to be approximately 20 cm.
In actuality, because of the overall length of the catheter, the water would undoubtedly warrra up before it reached the heat transfer element, and provision of 0°C water at the heat transfer element would be impossible. Circulating a cold liquid 2o would cause cooling along the catheter body and could result ire nonrspecific or total body hypothermia. Furthermore, to achieve this heat transfer rate, 5 gratnslsec of water flow are required. To circulate water through a 100 cm. long, 0.70 mm.
diameter supply tube at this rate produces a pressure dr~~p of more than 3000 psi. This pressure exceeds the safety levels of many flexible medical g~°ade plastic catheters.
25 Further, it is doubtful whether a water pump that can .generate these pressures and flow rates can be placed in an operating room.
~I~IEF SUMMARY ~F THE 1NVT"lrlTI~N
The selective organ cooling achieved by the present invention is accomplished 30 by placing a cooling catheter into the feeding artery of the organ. The cooling catheter is based on the vaporization and expansion of a compressed and condensed refrigerant, such as freon. In the catheter, a shaft or t~ody section would carry the W~ 89/37226 3'CT/tJS9910127s liquid refrigerant to a distal heat transfer element where vaporization, expansion, and cooling would occur. Cooling of the catheter tip to temperatures above minus ~°C
results in cooling of the blood flowing into the organs located distally of the catheter tip, and subsequent cooling of the target organ. For example, the catheter could be placed into the internal carotid artery, to cool the brain. The ;size and location of this artery places significant demands on the size and flexibility of the catheter.
Specifically, the outside diameter of the catheter must be minimized, so that the catheter can fit into the artery without compromising blood flow. Art appropriate catheter for this application would have a flexible body of l0 to 100 cm. in length and t0 2.0 to 3.0 mm. in outside diameter.
It is important for the catheter to be flexible in order to successfully navigate the arterial path, and this is especially true of the dish end of the catheter. So, the distal end of the catheter must have a flexible heat transfer element, which is corr'posed of a material which conducts heat better than the remainder of the catheter.
The catheter body material could be nylon or f~A?C;, and the heat transfer element could be madc from nitinol, which would have approximately 70 to I00 times the thermal conductivity of the catheter body material, and whir>h is also superelastic.
Nitinol could also be treated to undergo a transition to another shape, such as a coil, once it is placed in the proper artery. Certain tip shapes =~.ould improve heat transfer as well as allow the long tip to reside in arteries of shorter length.
The heat transfer element would require sufficiaent surface area to absorb 100 to i 50 watts of heat. This could be accomplished with a 2 mm, diameter heat transfer tube, 15 to 18 cm, in length, with a surfacx temperature of 0°C. Fins can be added to increase the surface area, or to maintain the desired surfhce area while shortening the 2s length.
The cooling would be provided by the vaporization anal expansion of a: liquid refrigerant, such as a freon, across an expansion element, such ~a a capillary tube. For example, freon 1112 boiling at 1 atmosphere and a flow rate of between 0.11 and O.18 liter/sec could provide between approximately 100 grad I50 watts of refrigeration power. Utilizing a liquid refrigerant allows the cooling to be focused at floe heat transfer element, thereby eliminating cooling along tire catheter body.
Utilizing boiling heat transfer to the expanded fluid also lowers the fluid flow rate requirement to remove the n oust of beat fronn the b! This ~ iru the required small diameter of the catheter would have higher ~ drops at higher ilo~nr rates:
The catheter dvould be bunt in a coaxiaD c~nstruction with a 0.70 nam. leaner would be connected to the !ow pressure side of the cozaa r.
Thus, in a broad aspect9 the invention provides an apparatus for causing hypothermia in at least a portion o~° a mammal, said apparatus comprising: a source of working fiuid~ a flexible elongated catheters said catheter having a flexible tubular outer catheter body; a flexible tubular inner working fluid supply conduit located within said outer catheter body, a proximal end of said inner working fluid supply conduit being connected in fluid flor~~ communication with ?6927-17D
an outlet of said source of working fluid; a working fluid return path within said outer catheter body a proximal end of said working fluid return path being connected in fluid flow communication with an inlet of saint soixrce of working fluid; a flexible elongated, hollow, heat transfer element mounted to said distal end of said outer catheter body; and a chamber defined within said hollow heat transfer element, said chamber being connected in fluid flow communication with an outlet of said working fluid supply conduit, said chamber being connected in fluid flow coimxnurr.ication with a distal end of said working fluid return path wa.thin said outer catheter bodyo 'Ihe novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters _refer to similar parts, and in which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Figure 1 is a schematic, partially in section, showing a. first embodiment of the flexib~.e catheter according to the present invention.
6a r r.
F n ~ ~ , ./~"..
CVO 99t37a26 ~'~TIiJS99lOd275 Figure 2 is a perspective view of a second etrabodirraent of the distal tip of the catheter of the present invention, after uansforntation;
Figure 3 is a section view of a third embodiment of the distal tip of the catheter of the present invention, after expansion of the heat transfer element;
Figure 4 is a partial section view ofa fourth etrtboditxtent of the distal tip of the catheter of the present invention, after transformation;
Figure 5 is an elevation view of a fifth embodiment of the distal tip of the catheter of the present invention, before transformation., Figure 6 is an elevation view of the embodiment shown in Figure 5, after t o transformation to a double helix;
Figure 7 is an elevation view of the emboditrtent shown in Figure 5, after transformation to a loops:d coil;
Figure 8 is an elevation view of a sixth embodiment of the distal tip of the catheter of the present invention, showing longitudinal fins on the heat transfer i 5 element;
Figure 9 is an end view of the embodiment shown in Figure 8;
Figure 10 is an elevation view of a seventh embodiment of the distal tip of the catheter of the present invention, showing annular fins on the heat transfer element;
and 2o Figure 1 l is an end view of the embodiment shove in Figure 10.
DETAIarED I~ESCFtIPTION OF THE IN'JENT.ION
As shown in Figure 1, the apparatus of the present invention includes a flexible catheter assembly 10, fed by a refrigeration coanpressor unit 12, which can z5 include a condenser. The compressor unit 12 has an outlet 14 and an inlet 16. The catheter assembly 10 has an outer flexible catheter body 18, which can be made of braided P13AX or other suitable catheter material. The catheter body 18 must be flexible, to enable passage through the vascular system of the patient to the feeding artery of the selected organ. The inner lumen 19 of the catheter body 18 serves as ehe 30 return flow path for the expanded refrigerant. The catheter assetr~bly 10 also has an inner flexible refrigerant supply conduit 2b, which can be made of nylon, polyimide, nitinol, or other suitable catheter material. The length anal diarne~ter of the catheter w~ 99137226 PC'I'lUS99/Ofi275 body 18 and refrigerant supply conduit 20 are designed for the size and location of the artery in which the apparatus will be used. For use in tlxe internal carotid artery to achieve hypothermia of the brain, the catheter body 18 and refrigerant supply conduit 20 will have a length of approximately 'JO to 100 centimeters. The catheter body 18 for this application will have an outside diameter of approximately 2.5 millimeters and an inside diameter of approximately 2.0 millimeters, and the refrigerant supply conduit will have an outside diameter of approximately 1.0 rraillimeter and an inside diameter of approximately 0.7~ millimeter. A supply conduit 20 of this diameter will have a refrigerant pressure drop of only approximately 0.042 atmospheres per centimeters. The return flow path through a catheter body 1 ~3 of this diameter will have a refrigerant pressure drop of only approximately 0.064 atmospheres per centimeters.
The compressor outlet I4 is attached in fluid flow comi:nunication, by known means, to a proximal end of the refrigerant supply c.oraduit '20 disposed coaxially t 5 within said catheter body 18. The distal end of the refrigerant supply conduit 20 is attached to an expansion element, which in this embodiment is a capillary tube having a lenght of approximately i 5 to 2~ centimeters. '1°he capillary tube 22 can be made of polyimide or nitinol, or other suitahle material, and it can be a separate element attached to the supply conduit 20, or it can be an integral portion of the 20 supply conduit 20. For the internal carotid artery application, the capillary tube 22 will have an outside diameter of approximately 0.6 millgrraeter arad an inside diameter of approximately 0.25 millimeter. The expansion element, such as the capillary tube 22, has an outlet wtthan a Chamber Of a flexible heat transfer element such as the hollow flexible tube 24. The tube 24 shown in this embodiment is flexible but 25 essentially straight in its unflexed state. The heat transfer element must be flexible, to enable passage through the vascular system of the patient o the i:eeding artery of the selected organ. For the internal carotid application the i'Iexible tube 24 will have a tength of approximately 1 S eentameters, an outside diameter of approximately 1.9 millimeters and an inside diameter of approximately l..S millimeters. The heat 3o transfer element also includcs a plug 26 in the distal end of the flexible tube 24. The plug 26 can be epoxy potting material, plastic, or a metal such as stainless steel or W~ 9913'7226 hCTNS99/Ot275 gold. A tapered transition of epoxy potting material can be provided between the catheter body 18 and the flexible tube 24.
A refrigerant, such as freon, is compressed, condensed, and pumped through the refrigerant supply conduit 20 to the expansion elemaent, or capillary tube, 22. The 5 refrigerant vaporizes and expands into the interior chamber of the heat transfer element, such as the flexible tube 24, thereby cooling the heat transfer element 24.
Blood in the feeding artery flows around the heal transfer element 24, thereby being cooled. The blood then continues to flow distally into the selected organ, thereby cooling the organ.
to A second embodiment of the heat transfer element is shown in Figure 2. This embodiment can be constructed of a tubular material such as nitinol, which has a temperature dependent shape memory. The heat transfer element 28 can be originally shaped like the flexible tube 24 shown in Figure I, at room tempea°ature, but trained to take on the coiled tubular shape shown in Figure 2 at a lower temperature.
This t 5 allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubular shape, similar to the flexible tube 24. Then, when the heat transfer element is at the desired location in the feeding artery, such as the internal carotid artery, refrigerant .flow is commenced.
As the expanding refrigerant, such as a 50/50 mixture of pentafluoroethane and l,I,l 2o trifluoroethane or a SOI~O mixture of difluoromethane and per~tafluoroethane, cools tine heat transfer element down, the heat transfer elemeaat takes on the shape of the heat transfer coil 28 shown in Figure 2. This enhances the heat transfer capacity, while limiting the length of the heat transfer element.
A third embodiment of the expansion element and the heat transfer element is 25 shown in Figure 3. This eanbodiment of the expansion eierrtent is an orifice 30, shown at the distal end of the refrigerant supply conduit 20. The outlet of the orifice 30 discharges into an expansion chamber 32. In tnis embodiment, the heat transfer element is a plurality of hollow tubes 34 leading from ties expansion chamber 32 to the refrigerant return lumen 19 of the catheter body 18. 'Chis embodiment of the heat 3o transfer element 34 can be constrtacted of a tubular material such as nitinol, which has a temperature dependent shape memory, or some other tubular material having a permanent bias toward a curved shape. The heat transfer element tubes 34 can be w~ 99137226 PC:TlUS99/01275 essentially straight, originally, at room temperature, but trained to take on the outwardly flexed "basket" shape shown in Figure 3 at a lower temperature.
'this allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubes. Then, when the heat transfer s element 34 is at the desired location in the feeding artc;ry, suct°~
as the internal carotid artery, refrigerant flow is commenced. As the expanding refrigerant cools the heat transfer element 34 down, the heat transfer element takes on the basket shape shown in Figure 3. This enhances the heat transfer capacity, while limiting the length of the heat transfer element.
A fourth errrbodiment of the heat transfer elemene is shown in Figure 4. This embodiment can be constructed of a material such as nitinol. The heat transfer element 36 can be originally shaped as a long loop extending from the distal end of the catheter body 1 g, at room temperature, but trained to take on the coiled tubular shape shown in Figure 4 at a tower temperature, with, the heat transfer element 36 t 5 coiled around the capillary cube 22. 'This allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubular loop shape. Then, when the heat transfer element 36 is at the desired location in the feeding artery, such as the internal carotid artery, refrigerant flow is commenced. A.s the expanding refrigerant cools the :heat transfer element 2o down, the heat transfer element takes on the shape of the coil 35 shown in Figure 4.
This enhances the heat transfer capacity, while limiting the length of the heat transfer element 36. Figure 4 further illustrates that a thermocouple 3& can be incorporated into the catheter body I li for temperature sensing purpos~a.
Yet a fifth embodiment of the heat transfer element is shown in Figures 5, 6, 2s and 7. In this embodiment, an expansion element, such as a capillary tube or oaifice, is incorporated within the distal end of the 6;atheter body I$. This embodiment of the heat transfer element can be constructed of a rraaterial such as nitirtol. The heat transfer element is originally shaped as_a long Loop 40 extending from the distal end of the catheter body 1 g, at roorrt temperature. The long loon 40 has two sides 42, 44, 3o which are substantially straight but flexible at morn temperatzare. The sides 42, 44 of the long loop 40 can be trained to take on the double helical shape shown in Figure 6 at a lower temperature, with the two sides 42, 44 of the heat transfer element 40 coiled ~_,-W~ 99137226 PCTJtJS99/OI275 around each other. Alternatively, the sides 42, 44 of the long loop 40 can be trained to take on the looped coil shape shown in Figure 7 at a lower temperature, with each of the two sides 42, 44 of the heat transfer element 40 coiled independently.
Either of these shapes allows easy insertion of the catheter assembly 10 through the vascular s system of the patient, with the essentially straight but flexible tubular loop shape.
Then, when the heat transfer element 40 is at the desirc;d location in the feeding artery, such as the internal carotid artery, refrigerant flow is commenced. As the expanding refrigerant cools the heat transfer element down, the heat transfer element 40 takes on the double helical shape shown in Figure 6 or the looped coil shape shown in Figure 7.
to Both of these configurations enhance the heat transfer capacity, while limiting the length of the heat transfer element 40.
As shown in figures 8 through 11, the heat transfer element 24 can have external fins 46, 48 attached thereto, such as by welding or brazing, to promote heat transfer. Use of such fins allows the use of a shorter heat trftnsfer element without ~ 5 reducing the heat transfer surface area, or increases the heat transfer surface area for a given length. In Figures 8 and 9, a plurality of longitudinal fins 46 are attached to the heat transfer element 24. The heat transfer element 24 in such an embodiment can have a diameter of approximately I .0 millimeter, while each of the fins 46 can have a width of approximately 0.5 millimeter and a thiclrness of approximately 0.12 20 millimeter. This will give the heat transfer element an overall diameter of approximately 2.0 millimeters, still allowing the cathebter to be inserted into the internal carotid artery.
in Figures 10 and I1, a plurality of annular fins 4g are attached to the heat transfer element 24. "The heat transfer element 24 in such an embodiment can have a 25 diameter of approximately 1.0 millimeter, while each of the 4g can have a width of approximately 0.5 millimeter and a thickness of approximately 0.12 millimeter.
This will give the heat transfer element an overall diameter of approximately 2.0 millimeters, still allowing the catheter to be inserted into the internal carotid artery.
3o While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the ob,~ects and providing the advantages her~.inbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred W~ 99/37226 PC°d'/US99It~t275 embodiments of the invention and that no limitations are intended other than as described in the appended claims.
A catheter based on the circulation of water or saline operates on the principle of transferring heat frogs the blood to raise the temperature of the water.
Rather than absorbing heat by boiling at a constant temperature like a freon, water must warm up ~ o to absorb heat and produce cooling. f~Iater flowing at the rate ~~f 5.0 gramslsec, at an initial temperature of 0°C and warming up to 5°C, can absorb 100 watts of heat. Thus, the outer surface of the heat transfer element could onl~r '~ maintained at 5°C, instead of 0°C. This will require the heat transfer element to have a surface area of approximately 1225 °n2. If a catheter of approximately 2.0 mm. diameter is 1 s assumed, the length of the heat transfer element would have to be approximately 20 cm.
In actuality, because of the overall length of the catheter, the water would undoubtedly warrra up before it reached the heat transfer element, and provision of 0°C water at the heat transfer element would be impossible. Circulating a cold liquid 2o would cause cooling along the catheter body and could result ire nonrspecific or total body hypothermia. Furthermore, to achieve this heat transfer rate, 5 gratnslsec of water flow are required. To circulate water through a 100 cm. long, 0.70 mm.
diameter supply tube at this rate produces a pressure dr~~p of more than 3000 psi. This pressure exceeds the safety levels of many flexible medical g~°ade plastic catheters.
25 Further, it is doubtful whether a water pump that can .generate these pressures and flow rates can be placed in an operating room.
~I~IEF SUMMARY ~F THE 1NVT"lrlTI~N
The selective organ cooling achieved by the present invention is accomplished 30 by placing a cooling catheter into the feeding artery of the organ. The cooling catheter is based on the vaporization and expansion of a compressed and condensed refrigerant, such as freon. In the catheter, a shaft or t~ody section would carry the W~ 89/37226 3'CT/tJS9910127s liquid refrigerant to a distal heat transfer element where vaporization, expansion, and cooling would occur. Cooling of the catheter tip to temperatures above minus ~°C
results in cooling of the blood flowing into the organs located distally of the catheter tip, and subsequent cooling of the target organ. For example, the catheter could be placed into the internal carotid artery, to cool the brain. The ;size and location of this artery places significant demands on the size and flexibility of the catheter.
Specifically, the outside diameter of the catheter must be minimized, so that the catheter can fit into the artery without compromising blood flow. Art appropriate catheter for this application would have a flexible body of l0 to 100 cm. in length and t0 2.0 to 3.0 mm. in outside diameter.
It is important for the catheter to be flexible in order to successfully navigate the arterial path, and this is especially true of the dish end of the catheter. So, the distal end of the catheter must have a flexible heat transfer element, which is corr'posed of a material which conducts heat better than the remainder of the catheter.
The catheter body material could be nylon or f~A?C;, and the heat transfer element could be madc from nitinol, which would have approximately 70 to I00 times the thermal conductivity of the catheter body material, and whir>h is also superelastic.
Nitinol could also be treated to undergo a transition to another shape, such as a coil, once it is placed in the proper artery. Certain tip shapes =~.ould improve heat transfer as well as allow the long tip to reside in arteries of shorter length.
The heat transfer element would require sufficiaent surface area to absorb 100 to i 50 watts of heat. This could be accomplished with a 2 mm, diameter heat transfer tube, 15 to 18 cm, in length, with a surfacx temperature of 0°C. Fins can be added to increase the surface area, or to maintain the desired surfhce area while shortening the 2s length.
The cooling would be provided by the vaporization anal expansion of a: liquid refrigerant, such as a freon, across an expansion element, such ~a a capillary tube. For example, freon 1112 boiling at 1 atmosphere and a flow rate of between 0.11 and O.18 liter/sec could provide between approximately 100 grad I50 watts of refrigeration power. Utilizing a liquid refrigerant allows the cooling to be focused at floe heat transfer element, thereby eliminating cooling along tire catheter body.
Utilizing boiling heat transfer to the expanded fluid also lowers the fluid flow rate requirement to remove the n oust of beat fronn the b! This ~ iru the required small diameter of the catheter would have higher ~ drops at higher ilo~nr rates:
The catheter dvould be bunt in a coaxiaD c~nstruction with a 0.70 nam. leaner would be connected to the !ow pressure side of the cozaa r.
Thus, in a broad aspect9 the invention provides an apparatus for causing hypothermia in at least a portion o~° a mammal, said apparatus comprising: a source of working fiuid~ a flexible elongated catheters said catheter having a flexible tubular outer catheter body; a flexible tubular inner working fluid supply conduit located within said outer catheter body, a proximal end of said inner working fluid supply conduit being connected in fluid flor~~ communication with ?6927-17D
an outlet of said source of working fluid; a working fluid return path within said outer catheter body a proximal end of said working fluid return path being connected in fluid flow communication with an inlet of saint soixrce of working fluid; a flexible elongated, hollow, heat transfer element mounted to said distal end of said outer catheter body; and a chamber defined within said hollow heat transfer element, said chamber being connected in fluid flow communication with an outlet of said working fluid supply conduit, said chamber being connected in fluid flow coimxnurr.ication with a distal end of said working fluid return path wa.thin said outer catheter bodyo 'Ihe novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters _refer to similar parts, and in which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Figure 1 is a schematic, partially in section, showing a. first embodiment of the flexib~.e catheter according to the present invention.
6a r r.
F n ~ ~ , ./~"..
CVO 99t37a26 ~'~TIiJS99lOd275 Figure 2 is a perspective view of a second etrabodirraent of the distal tip of the catheter of the present invention, after uansforntation;
Figure 3 is a section view of a third embodiment of the distal tip of the catheter of the present invention, after expansion of the heat transfer element;
Figure 4 is a partial section view ofa fourth etrtboditxtent of the distal tip of the catheter of the present invention, after transformation;
Figure 5 is an elevation view of a fifth embodiment of the distal tip of the catheter of the present invention, before transformation., Figure 6 is an elevation view of the embodiment shown in Figure 5, after t o transformation to a double helix;
Figure 7 is an elevation view of the emboditrtent shown in Figure 5, after transformation to a loops:d coil;
Figure 8 is an elevation view of a sixth embodiment of the distal tip of the catheter of the present invention, showing longitudinal fins on the heat transfer i 5 element;
Figure 9 is an end view of the embodiment shown in Figure 8;
Figure 10 is an elevation view of a seventh embodiment of the distal tip of the catheter of the present invention, showing annular fins on the heat transfer element;
and 2o Figure 1 l is an end view of the embodiment shove in Figure 10.
DETAIarED I~ESCFtIPTION OF THE IN'JENT.ION
As shown in Figure 1, the apparatus of the present invention includes a flexible catheter assembly 10, fed by a refrigeration coanpressor unit 12, which can z5 include a condenser. The compressor unit 12 has an outlet 14 and an inlet 16. The catheter assembly 10 has an outer flexible catheter body 18, which can be made of braided P13AX or other suitable catheter material. The catheter body 18 must be flexible, to enable passage through the vascular system of the patient to the feeding artery of the selected organ. The inner lumen 19 of the catheter body 18 serves as ehe 30 return flow path for the expanded refrigerant. The catheter assetr~bly 10 also has an inner flexible refrigerant supply conduit 2b, which can be made of nylon, polyimide, nitinol, or other suitable catheter material. The length anal diarne~ter of the catheter w~ 99137226 PC'I'lUS99/Ofi275 body 18 and refrigerant supply conduit 20 are designed for the size and location of the artery in which the apparatus will be used. For use in tlxe internal carotid artery to achieve hypothermia of the brain, the catheter body 18 and refrigerant supply conduit 20 will have a length of approximately 'JO to 100 centimeters. The catheter body 18 for this application will have an outside diameter of approximately 2.5 millimeters and an inside diameter of approximately 2.0 millimeters, and the refrigerant supply conduit will have an outside diameter of approximately 1.0 rraillimeter and an inside diameter of approximately 0.7~ millimeter. A supply conduit 20 of this diameter will have a refrigerant pressure drop of only approximately 0.042 atmospheres per centimeters. The return flow path through a catheter body 1 ~3 of this diameter will have a refrigerant pressure drop of only approximately 0.064 atmospheres per centimeters.
The compressor outlet I4 is attached in fluid flow comi:nunication, by known means, to a proximal end of the refrigerant supply c.oraduit '20 disposed coaxially t 5 within said catheter body 18. The distal end of the refrigerant supply conduit 20 is attached to an expansion element, which in this embodiment is a capillary tube having a lenght of approximately i 5 to 2~ centimeters. '1°he capillary tube 22 can be made of polyimide or nitinol, or other suitahle material, and it can be a separate element attached to the supply conduit 20, or it can be an integral portion of the 20 supply conduit 20. For the internal carotid artery application, the capillary tube 22 will have an outside diameter of approximately 0.6 millgrraeter arad an inside diameter of approximately 0.25 millimeter. The expansion element, such as the capillary tube 22, has an outlet wtthan a Chamber Of a flexible heat transfer element such as the hollow flexible tube 24. The tube 24 shown in this embodiment is flexible but 25 essentially straight in its unflexed state. The heat transfer element must be flexible, to enable passage through the vascular system of the patient o the i:eeding artery of the selected organ. For the internal carotid application the i'Iexible tube 24 will have a tength of approximately 1 S eentameters, an outside diameter of approximately 1.9 millimeters and an inside diameter of approximately l..S millimeters. The heat 3o transfer element also includcs a plug 26 in the distal end of the flexible tube 24. The plug 26 can be epoxy potting material, plastic, or a metal such as stainless steel or W~ 9913'7226 hCTNS99/Ot275 gold. A tapered transition of epoxy potting material can be provided between the catheter body 18 and the flexible tube 24.
A refrigerant, such as freon, is compressed, condensed, and pumped through the refrigerant supply conduit 20 to the expansion elemaent, or capillary tube, 22. The 5 refrigerant vaporizes and expands into the interior chamber of the heat transfer element, such as the flexible tube 24, thereby cooling the heat transfer element 24.
Blood in the feeding artery flows around the heal transfer element 24, thereby being cooled. The blood then continues to flow distally into the selected organ, thereby cooling the organ.
to A second embodiment of the heat transfer element is shown in Figure 2. This embodiment can be constructed of a tubular material such as nitinol, which has a temperature dependent shape memory. The heat transfer element 28 can be originally shaped like the flexible tube 24 shown in Figure I, at room tempea°ature, but trained to take on the coiled tubular shape shown in Figure 2 at a lower temperature.
This t 5 allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubular shape, similar to the flexible tube 24. Then, when the heat transfer element is at the desired location in the feeding artery, such as the internal carotid artery, refrigerant .flow is commenced.
As the expanding refrigerant, such as a 50/50 mixture of pentafluoroethane and l,I,l 2o trifluoroethane or a SOI~O mixture of difluoromethane and per~tafluoroethane, cools tine heat transfer element down, the heat transfer elemeaat takes on the shape of the heat transfer coil 28 shown in Figure 2. This enhances the heat transfer capacity, while limiting the length of the heat transfer element.
A third embodiment of the expansion element and the heat transfer element is 25 shown in Figure 3. This eanbodiment of the expansion eierrtent is an orifice 30, shown at the distal end of the refrigerant supply conduit 20. The outlet of the orifice 30 discharges into an expansion chamber 32. In tnis embodiment, the heat transfer element is a plurality of hollow tubes 34 leading from ties expansion chamber 32 to the refrigerant return lumen 19 of the catheter body 18. 'Chis embodiment of the heat 3o transfer element 34 can be constrtacted of a tubular material such as nitinol, which has a temperature dependent shape memory, or some other tubular material having a permanent bias toward a curved shape. The heat transfer element tubes 34 can be w~ 99137226 PC:TlUS99/01275 essentially straight, originally, at room temperature, but trained to take on the outwardly flexed "basket" shape shown in Figure 3 at a lower temperature.
'this allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubes. Then, when the heat transfer s element 34 is at the desired location in the feeding artc;ry, suct°~
as the internal carotid artery, refrigerant flow is commenced. As the expanding refrigerant cools the heat transfer element 34 down, the heat transfer element takes on the basket shape shown in Figure 3. This enhances the heat transfer capacity, while limiting the length of the heat transfer element.
A fourth errrbodiment of the heat transfer elemene is shown in Figure 4. This embodiment can be constructed of a material such as nitinol. The heat transfer element 36 can be originally shaped as a long loop extending from the distal end of the catheter body 1 g, at room temperature, but trained to take on the coiled tubular shape shown in Figure 4 at a tower temperature, with, the heat transfer element 36 t 5 coiled around the capillary cube 22. 'This allows easier insertion of the catheter assembly 10 through the vascular system of the patient, with the essentially straight but flexible tubular loop shape. Then, when the heat transfer element 36 is at the desired location in the feeding artery, such as the internal carotid artery, refrigerant flow is commenced. A.s the expanding refrigerant cools the :heat transfer element 2o down, the heat transfer element takes on the shape of the coil 35 shown in Figure 4.
This enhances the heat transfer capacity, while limiting the length of the heat transfer element 36. Figure 4 further illustrates that a thermocouple 3& can be incorporated into the catheter body I li for temperature sensing purpos~a.
Yet a fifth embodiment of the heat transfer element is shown in Figures 5, 6, 2s and 7. In this embodiment, an expansion element, such as a capillary tube or oaifice, is incorporated within the distal end of the 6;atheter body I$. This embodiment of the heat transfer element can be constructed of a rraaterial such as nitirtol. The heat transfer element is originally shaped as_a long Loop 40 extending from the distal end of the catheter body 1 g, at roorrt temperature. The long loon 40 has two sides 42, 44, 3o which are substantially straight but flexible at morn temperatzare. The sides 42, 44 of the long loop 40 can be trained to take on the double helical shape shown in Figure 6 at a lower temperature, with the two sides 42, 44 of the heat transfer element 40 coiled ~_,-W~ 99137226 PCTJtJS99/OI275 around each other. Alternatively, the sides 42, 44 of the long loop 40 can be trained to take on the looped coil shape shown in Figure 7 at a lower temperature, with each of the two sides 42, 44 of the heat transfer element 40 coiled independently.
Either of these shapes allows easy insertion of the catheter assembly 10 through the vascular s system of the patient, with the essentially straight but flexible tubular loop shape.
Then, when the heat transfer element 40 is at the desirc;d location in the feeding artery, such as the internal carotid artery, refrigerant flow is commenced. As the expanding refrigerant cools the heat transfer element down, the heat transfer element 40 takes on the double helical shape shown in Figure 6 or the looped coil shape shown in Figure 7.
to Both of these configurations enhance the heat transfer capacity, while limiting the length of the heat transfer element 40.
As shown in figures 8 through 11, the heat transfer element 24 can have external fins 46, 48 attached thereto, such as by welding or brazing, to promote heat transfer. Use of such fins allows the use of a shorter heat trftnsfer element without ~ 5 reducing the heat transfer surface area, or increases the heat transfer surface area for a given length. In Figures 8 and 9, a plurality of longitudinal fins 46 are attached to the heat transfer element 24. The heat transfer element 24 in such an embodiment can have a diameter of approximately I .0 millimeter, while each of the fins 46 can have a width of approximately 0.5 millimeter and a thiclrness of approximately 0.12 20 millimeter. This will give the heat transfer element an overall diameter of approximately 2.0 millimeters, still allowing the cathebter to be inserted into the internal carotid artery.
in Figures 10 and I1, a plurality of annular fins 4g are attached to the heat transfer element 24. "The heat transfer element 24 in such an embodiment can have a 25 diameter of approximately 1.0 millimeter, while each of the 4g can have a width of approximately 0.5 millimeter and a thickness of approximately 0.12 millimeter.
This will give the heat transfer element an overall diameter of approximately 2.0 millimeters, still allowing the catheter to be inserted into the internal carotid artery.
3o While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the ob,~ects and providing the advantages her~.inbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred W~ 99/37226 PC°d'/US99It~t275 embodiments of the invention and that no limitations are intended other than as described in the appended claims.
Claims (8)
1. An apparatus for causing hypothermia in at least a portion of a mammal, said apparatus comprising:
a source of working fluid;
a flexible elongated catheter, said catheter having a flexible tubular outer catheter body;
a flexible tubular inner working fluid supply conduit located within said outer catheter body, a proximal end of said inner working fluid supply conduit being connected in fluid flow communication with an outlet of said source of working fluid;
a working fluid return path within said outer catheter body, a proximal end of said working fluid return path being connected in fluid flow communication with an inlet of said source of working fluid;
a flexible elongated, hollow, heat transfer element mounted to said distal end of said outer catheter body; and a chamber defined within said follow heat transfer element, said chamber being connected in fluid flow communication with an outlet of said working fluid supply conduit, said chamber being connected in fluid flow communication with a distal end of said working fluid return path within said outer catheter body.
a source of working fluid;
a flexible elongated catheter, said catheter having a flexible tubular outer catheter body;
a flexible tubular inner working fluid supply conduit located within said outer catheter body, a proximal end of said inner working fluid supply conduit being connected in fluid flow communication with an outlet of said source of working fluid;
a working fluid return path within said outer catheter body, a proximal end of said working fluid return path being connected in fluid flow communication with an inlet of said source of working fluid;
a flexible elongated, hollow, heat transfer element mounted to said distal end of said outer catheter body; and a chamber defined within said follow heat transfer element, said chamber being connected in fluid flow communication with an outlet of said working fluid supply conduit, said chamber being connected in fluid flow communication with a distal end of said working fluid return path within said outer catheter body.
2. An apparatus as recited in claim 1, wherein:
said working fluid supply conduit is substantially coaxial with said catheter body; and said working fluid return path surrounds said working fluid supply conduit.
said working fluid supply conduit is substantially coaxial with said catheter body; and said working fluid return path surrounds said working fluid supply conduit.
3. An apparatus as recited in claim 2, wherein said heat transfer element comprises a hollow tube of material conducive to heat transfer.
4. An apparatus as recited in claim 3, further comprising at least one fin of heat conducive material attached to said hollow tubular heat transfer element.
5. An apparatus as recited in claim 4, wherein said at least one fin comprises a longitudinal fin.
6. An apparatus as recited in claim 4, wherein said at least one fin comprises an annular fin.
7. An apparatus as recited in claim 1, wherein said heat transfer element comprises a plurality of hollow tubes leading from said working fluid supply conduit to said working fluid return path in said catheter body, said hollow tubes being outwardly expandable.
8. An apparatus as recited in claim 1, wherein said heat transfer element comprises a hollow tube coiled around said working fluid supply conduit.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/012,287 | 1998-01-23 | ||
| US09/012,287 US6051019A (en) | 1998-01-23 | 1998-01-23 | Selective organ hypothermia method and apparatus |
| CA002318084A CA2318084C (en) | 1998-01-23 | 1999-01-21 | Selective organ hypothermia method and apparatus |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002318084A Division CA2318084C (en) | 1998-01-23 | 1999-01-21 | Selective organ hypothermia method and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2470150A1 true CA2470150A1 (en) | 1999-07-29 |
Family
ID=32772528
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002470150A Abandoned CA2470150A1 (en) | 1998-01-23 | 1999-01-21 | Selective organ hypothermia method and apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2470150A1 (en) |
-
1999
- 1999-01-21 CA CA002470150A patent/CA2470150A1/en not_active Abandoned
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