Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2002-03-11
2004-02-24
Kearney, Rosiland S. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S106000, C607S113000, C128S898000
Reexamination Certificate
active
06695873
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The 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.
2. Background Information
Organs in the human body, such as the brain, kidney and heart, are maintained at a constant temperature of approximately 37° C. Hypothermia can be clinically defined as a core body temperature of 35° C. or less. Hypothermia is sometimes characterized further according to its severity. A body core temperature in the range of 33° C. to 35° C. is described as mild hypothermia. A body temperature of 28° C. to 32° C. is described as moderate hypothermia. A body core temperature in the range of 24° C. to 28° C. is described as severe hypothermia.
Hypothermia is uniquely effective in reducing brain injury caused by a variety of neurological insults and may eventually play an important role in emergency brain resuscitation. Experimental evidence has demonstrated that cerebral cooling improves the patient's outcome after global ischemia, focal ischemia, or traumatic brain injury. For this reason, hypothermia may be induced in order to reduce the effect of certain bodily injuries to the brain as well as other organs.
Cerebral hypothermia has traditionally been accomplished through whole body cooling to create a condition of total body hypothermia in the range of 20° C. to 30° C. However, the use of total body hypothermia risks certain deleterious systematic vascular effects. For example, total body hypothermia may cause severe derangement of the cardiovascular system, including low cardiac output, elevated systematic resistance, and ventricular fibrillation. Other side effects include renal failure, disseminated intravascular coagulation, and electrolyte disturbances. In addition to the undesirable side effects, total body hypothermia is difficult to administer.
Catheters have been developed which are inserted into the bloodstream of the patient in order to induce total body hypothermia. For example, U.S. Pat. No. 3,425,419 to Dato describes a device and technique of lowering and raising the temperature of the human body. The Dato reference discloses a technique of inducing moderate hypothermia in a patient using a metallic catheter. The metallic catheter has an inner passageway through which a fluid, such as water, can be circulated. The catheter is inserted through the femoral vein and then through the inferior vena cava as far as the right atrium and the superior vena cava. The Dato reference discloses a catheter having an elongated cylindrical shape and is constructed from stainless steel. By way of example, Dato suggests the use of a catheter approximately 70 cm in length and approximately 6 mm in diameter. However, use of the Dato device implicates the negative effects of total body hypothermia described above.
Due to the problems associated with total body hypothermia, attempts have been made to provide more selective cooling. For example, cooling helmets or head gear have been used in an attempt to cool only the head rather than the patient's entire body. However, such methods rely on conductive heat transfer through the skull and into the brain. One drawback of using conductive heat transfer is that the process of reducing the temperature of the brain is prolonged. Also, it is difficult to precisely control the temperature of the brain when using conduction due to the temperature gradient that must be established externally in order to sufficiently lower the internal temperature. In addition, when using conduction to cool the brain, the face of the patient is also subjected to severe hypothermia, increasing discomfort and the likelihood of negative side effects. It is known that profound cooling of the face can cause similar cardiovascular side effects as total body cooling. From a practical standpoint, such devices are cumbersome and may make continued treatment of the patient difficult or impossible.
Selective organ hypothermia has also been attempted by perfusion of a cold solution such as saline or perflourocarbons. This process is commonly used to protect the heart during heart surgery and is referred to as cardioplegia. Perfusion of a cold solution has a number of drawbacks, including a limited time of administration due to excessive volume accumulation, cost, and inconvenience of maintaining the perfusate and lack of effectiveness due to the temperature dilution from the blood. Temperature dilution by the blood is a particular problem in high blood flow organs such as the brain.
Therefore, there is a need for a practical method and apparatus which modifies and controls the temperature of a selected organ but does not suffer from the drawbacks of total body hypothermia or cold perfusion.
BRIEF SUMMARY OF THE INVENTION
The invention provides a method and device to transfer heat to or from a selected organ in an efficient manner. The device has a high degree of lateral flexibility and is collapsible, thereby affording an easy insertion procedure. The device allows high surface area to increase heat transfer.
In one aspect, the invention is directed to a catheter system to change the temperature of blood by heat transfer to or from a working fluid. The system includes an inflatable inlet lumen and outlet lumen. The outlet lumen is coupled to the inlet lumen so as to transfer working fluid between the two. The outlet lumen has a structure when inflated to induce turbulence in the blood and/or in the working fluid.
Variations of the system may include one or more of the following. The inlet lumen and the outlet lumen may be made of a flexible material such as latex rubber. The outlet lumen may have a structure to induce turbulence in the working fluid when inflated, such as a helical shape which may be tapered in a segmented or non-segmented manner. The radii of the inlet and outlet lumens may decrease in a distal direction such that the inlet and outlet lumens are tapered when inflated. A wire may be disposed in the inlet or outlet lumens to provide shape and strength when deflated.
The thickness of the outlet lumen, when inflated, may be less than about {fraction (1/2 )} mil. The length of the inlet lumen may be between about 5 and 30 centimeters. If the outlet lumen has a helical shape, the diameter of the helix may be less than about 8 millimeters when inflated. The outer diameter of the helix of the outlet lumen, when inflated, may be between about 2 millimeters and 8 millimeters and may taper to between about 1 millimeter and 2 millimeters. In segmented embodiments, a length of a segment may be between about 1 centimeter and 10 centimeters. The radii of the inlet and outlet lumens when inflated may be between about 0.5 millimeters and 2 millimeters.
The outlet lumen may further include at least one surface feature and/or interior feature, the surface feature inducing turbulence in the fluid adjacent the outlet lumen and the interior feature inducing turbulence in the working fluid. The surface feature may include one or more helical turns or spirals formed in the outlet lumen. Adjacent turns may employ opposite helicity. Alternatively or in combination, the surface feature may be a series of staggered protrusions formed in the outlet lumen.
The turbulence-inducing outlet lumen may be adapted to induce turbulence when inflated within a free stream of blood when placed within an artery. The turbulence intensity may be greater than about 0.05. The turbulence-inducing outlet lumen may be adapted to induce turbulence when inflated throughout the period of the cardiac cycle when placed within an artery or during at least 20% of the period.
The system may further include a coaxial supply catheter having an inner catheter lumen coupled to the inlet lumen and a working fluid supply configured to dispense the working fluid and having an output coupled to the inner catheter lumen. The working fluid supply may be configured to produce a pressurized working fluid at a tempe
Dobak III John D.
Lasheras Juan C.
Innercool Therapies, Inc.
Kearney Rosiland S.
Mayer Fortkort & Williams
Wieczorek Mark D.
Williams Karin L.
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