Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-08-02
2001-09-11
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S105000, C604S113000, C606S027000
Reexamination Certificate
active
06287326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a catheter that effects heat transfer using a coiled hollow tube at the catheter's distal end.
2. Description of the Related Art
In warm blooded creatures, temperature regulation is one of the most important functions of the body. Despite the known importance of properly maintaining body temperature, scientists have discovered certain beneficial effects of artificially inducing a hypothermic state. For instance, cooling the body can help regulate vital functions during surgery by lowering the metabolism. With stroke, trauma, and other conditions, hypothermia is believed to reduce the permeability of the blood/brain barrier. Also, induced hypothermia is believed to inhibit the release of damaging neurotransmitters, inhibit calcium mediated effects, inhibit brain edema, and lower intra cranial pressure. Regardless of the particular mechanism, the present invention understands that fevers degrade the outcomes for patients suffering from brain trauma or stroke, and moreover that hypothermia improves the outcomes for such patients.
Hypothermia may be induced locally or systemically. With local hypothermia, physicians focus their cooling efforts on a particular organ, limb, anatomical system, or other region of the body. With systemic hypothermia, body temperature is lowered without particular attention to any body part.
Under one technique for inducing systemic hypothermia, physicians cool the patient's entire body by packing it in ice. Although this technique has been used with some success, some physicians may find it cumbersome, and particularly time consuming. Also, it is difficult to precisely control body temperature with ice packing. As a result, the patient's body temperature overshoots and undershoots the optimal temperature, requiring physicians to add or remove ice. Furthermore, there is some danger of injuring the skin, which is necessarily cooled more than any other body part.
In another approach to systemic hypothermia, the patient is covered with a cooling blanket, such as an inflatable air-or water-filled cushion. Physicians control the patient's temperature by regulating the temperature of the inflation medium. Nonetheless, some delay is still inherent, first for a cooling element to change the temperature of the cooling medium, and then for the temperature adjusted cooling medium to cool the desired body part. This delay is even longer if the targeted body part is an internal organ, since the most effective cooling is only applied to the skin, and takes some time to successively cool deeper and deeper layers within the body.
The present invention recognizes that a better approach to inducing hypothermia is by circulating a cooling fluid through a cooling catheter placed inside a patient's body. The catheter may be inserted into veins, arteries, cavities, or other internal regions of the body. The present assignee has pioneered a number of different cooling catheters and techniques in this area. Several different examples are shown in U.S. application Ser. No. 09/133,813, entitled “Indwelling Heat Exchange Catheter and Method of Using Same,” filed on Aug. 13, 1998. Further examples are illustrated in U.S. application Ser. No. 09/294,080 entitled “Catheter With Multiple Heating/Cooling Fibers Employing Fiber Spreading Features,” filed on Apr. 19, 1999 in the names of Blair D. Walker et al. The foregoing applications are hereby incorporated into the present application by reference. These applications depict many catheters, including some where the tip region includes multiple hollow fibers. The fibers carry a coolant that is circulated through the catheter. The thin walls and substantial surface area of the fibers efficiently transfer heat from surrounding body fluids/tissue to the coolant, thereby cooling the patient.
Advantageously, cooling catheters are convenient to use, and enable doctors to accurately control the temperature of a targeted region. The present invention provides one such catheter.
SUMMARY OF THE INVENTION
Broadly, the present invention concerns a catheter with a sealed multi-lumen heat transfer extension designed to internally circulate a coolant, and thereby cool tissue or fluid surrounding the catheter. The heat transfer extension comprises a tube having a distally positioned region that forms a coil about the tube's longitudinal axis. This tube has multiple lumens that longitudinally span the tube, including one or more supply lumens and one or more return lumens. In one arrangement, the lumens include a centrally disposed return lumen surrounded by a number of parallel supply lumens, where the supply lumens are cross-sectionally arranged in a circle around the return lumen. A distal fluid exchange reservoir resides at the tube's tip, for the purpose of redirecting fluid from the supply lumens to the return lumen. In one embodiment, the heat transfer extension is permanently shaped to provide the desired coil shape. In a different embodiment, heat transfer extension may include shape memory structure causing the heat transfer extension to vary its shape according to temperature. Namely, the tube assumes a coiled shape under predetermined shape-active temperatures, and it assumes a flexible shape under other predetermined shape-relaxed temperatures. As examples, the shape memory structure may comprise a shaping wire longitudinally running through the extension, or shape memory material built into the extension. The catheter also includes supply and return lines to provide coolant to the heat transfer extension, and remove coolant returning therefrom. To interface the supply/return lines with the supply/return lumens, the invention may employ a fluid transfer housing.
Accordingly, in one embodiment, the invention may be implemented to provide an apparatus such as a catheter with a multi-lumen heat transfer extension having a distal region that has a coiled shape under some or all conditions. In another embodiment, the invention may be implemented to provide methods of manufacturing or utilizing such a catheter.
The invention affords its users with a number of distinct advantages. First, the invention provides significant heat exchange because of the heat transfer extension's substantial surface area. Due to the coiled configuration of the heat transfer extension, the catheter includes a substantial surface area that easily fits into a small region inside the patient. Additionally, the catheter of this invention minimizes the creation of blood clots. This is because the catheter provides a single heat transfer extension free from any junctions, constrictions, or abutting components that might otherwise encourage blood clots. As another advantage, owing to the unitary design of the heat transfer extension, the catheter of this invention is more easily manufactured than more complicated designs. The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention.
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Alsius Corporation
Burns Doane , Swecker, Mathis LLP
Dvorak Linda C. M.
Gibson Roy
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