Method of making selective organ cooling catheter

#Not Applicable

#I. Field of the Invention

#The present invention relates generally to the modification and control of the temperature of a selected body organ. More particularly, the invention relates to a method and intravascular apparatus for controlling organ temperature.

#The features, objects, and advantages of the invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify corresponding throughout and wherein:

#FIG. 1 is a graph illustrating the velocity of steady state turbulent flow as a function of time.

#FIG. 2A is a graph showing the velocity of the blood flow within an artery as a function of time.

#In order to intravascularly regulate the temperature of a selected organ, a heat transfer element may be placed in the feeding artery of the organ to absorb or deliver the heat from or to the blood flowing into the organ. The transfer of heat may cause either a cooling or a heating of the selected organ. The heat transfer element must be small enough to fit within the feeding artery while still allowing a sufficient blood flow to reach the organ in order to avoid ischemic organ damage. A heat transfer element which selectively cools an organ should be capable of providing the necessary heat transfer rate to produce the desired cooling or heating effect within the organ. By placing the heat transfer element within the feeding artery of an organ, the temperature of an organ can be controlled without significantly effecting the remaining parts of the body. These points can be illustrated by using brain cooling as an example.

#The common carotid artery supplies blood to the head and brain. The internal carotid artery branches off of the common carotid to directly supply blood to the brain. To selectively cool the brain, the heat transfer element is placed into the common carotid artery, the internal carotid artery, or both. The internal diameter of the common carotid artery ranges from 6 to 8 mm and the length ranges from 80 to 120 mm. Thus, the heat transfer element residing in one of these arteries cannot be much larger than 4 mm in diameter in order to avoid occluding the vessel.

#It is important that the heat transfer element be flexible in order to be placed within the small feeding artery of an organ. Feeding arteries, like the carotid artery, branch off the aorta at various levels. Subsidiary arteries continue to branch off the initial branches. For example, the internal carotid artery is a small diameter artery that branches off of a common carotid artery near the angle of the jaw. Because the heat transfer element is typically inserted into a peripheral artery, such as the femoral artery, and accesses the feeding artery by initially passing though a series of one or more of these branch, the flexibility of the heat transfer element is an important characteristic of the heat transfer element. Further, the heat transfer element is ideally constructed from a high thermally conductive material such as metal in order to facilitate heat transfer. The use of a high thermally conductive material increases the heat transfer rate for a given temperature differential between the coolant within the heat transfer element and the blood. This facilitates the use of a higher temperature coolant within the heat transfer element, allowing safer coolants such as water to be used. High thermally conductive materials, such as metals, tend to be rigid. The design of the heat transfer element should facilitate flexibility in an inherently inflexible material.