Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-09-09
2001-02-13
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S102000, C607S156000, C606S032000, C606S033000, C606S034000, C606S041000, C128S898000
Reexamination Certificate
active
06188930
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and system for providing localized heating of bodily tissues, and more particularly to a system and method for localized heating of the preoptic anterior hypothalamus (POAH).
BACKGROUND OF THE INVENTION
Stroke is one of the leading causes of death in adults and also a major cause of neurological disability. Until recently, stroke has been viewed as an untreatable event and all physicians could offer a stroke victim was rehabilitation to try to regain lost functions. In an effort to reduce the damage caused by strokes, a number of treatments have been proposed. In one interventional approach, known as neuroprotectant therapy, the intent is to limit the amount of neurological damage that occurs after the initial event. Neuroprotectant approaches includes the administration of several pharmacological agents and a treatment known as mild hypothermia, or a lowering of core body temperature by 2-4 degrees Celsius. The induction of mild hypothermia has been shown to inhibit several points of the chemical cascade that cause secondary cellular death after an ischemic event and to provide broad neuroprotection.
One method of inducing mild hypothermia is through heating of the preoptic anterior hypothalamus (POAH) which is located in the lower portion of the brain adjacent to the skull. It is known that the POAH is the thermostat for sensing core body temperature and controlling thermo regulatory responses in animals. The cooling mechanisms elicited by the POAH include reduction of metabolic energy generation, vasodilatation enhancing skin cooling, and sweating. Full vasodilatation can increase the rate of heat transfer to the skin as much as eight fold. An additional one degree Celsius It is known that the POAH is the thermostat for sensing core body temperature and controlling thermo regulatory responses in animals. The cooling mechanisms elicited by the POAH include reduction of metabolic energy generation, vasodilatation enhancing skin cooling, and sweating. Full vasodilatation can increase the rate of heat transfer to the skin as much as eight fold. An additional one degree Celsius increase in body temperature can increase sweating enough to remove ten times the basal rate of heat protection.
SUMMARY OF THE INVENTION
For a patient receiving treatment, it has been recognized that if particular forms of radiant energy, such as microwave energy, are emitted from locations proximate to the POAH, localized heating of the POAH may be provided. It has been further recognized that heating of the POAH may also cause heating in bodily tissues which surround the POAH, and as such, a cooling may be provided for said tissues.
In order to induce the desired heating in the POAH, a catheter device configurable to emit radiant energy at a selected magnitude may be provided. The catheter device may be further configured to be positionable at a desired location with regards to the POAH. A cooling apparatus may be employed in conjunction with the catheter device to provide cooling for surrounding bodily tissues.
In operation, the catheter device may be initially positioned at the desired location proximate to the POAH. Once positioned, predetermined amounts of radiant energy may then be emitted from the catheter device at the POAH. While the POAH is being heated, the cooling apparatus may be activated and the surrounding bodily tissues cooled.
In one aspect of the invention, the catheter device may be routed through the nasal cavity of the patient into the sphenoidal sinus. Once the catheter device is positioned, radiant energy may be emitted, heating the POAH. Upon application of the heat, the POAH may begin initiating thermoregulatory cooling processes for the patient such as reduction in metabolic energy generation, vasodilatation, and sweating which act to reduce the core body temperature.
In another aspect of the invention, the catheter device and connecting electronics may be configured such that microwave radiation is employed as the radiant energy. A waveguide may run from a microwave oscillator and power source, to an antennae incorporated in the catheter device. A control device may be further connected to the oscillator to provide for manual or automated control of the magnitude of radiant energy emitted through the antennae.
As was described above, the system described herein may further include a cooling apparatus. As part of this cooling apparatus, the catheter device may include a bladder-like structure through which a coolant, such as a liquid or gas, may be circulated. A reservoir of coolant may be remotely located, and a pump may be employed to circulate coolant through the bladder. When the coolant is pumped, the bladder may expand and contact bodily tissues which are in close proximity to the catheter device, and the coolant circulated through the bladder may provide cooling for said tissues. The amount of cooling may be varied by changing the temperature or rate of circulation of the coolant.
The system described herein may further include a number of sensors which may be employed to control the heating process. These sensors may take measurements at designated locations and provide feedback signals which may be used to vary the amount of radiant energy emitted by the catheter device. A first condition which may be detected by a sensor is skin conductivity. This measurement may provide an indication of the amount a patient is sweating when the thermoregulatory cooling processes are initiated. Electrodes may be placed at a selected location on the skin surface of the patient and measurements taken across the electrodes.
The skin conductivity measurement may be employed in situations where the optimal location for positioning the catheter is sought. Because the microwave energy emitted from the antennae may have directional sensitivity, the catheter device requires positioning in order to identify an optimal transmission location. To find this optimal location, the catheter device may be initially positioned in the sinus cavity and radiant energy emitted from the catheter device at a low magnitude. As the POAH initiates the cooling processes for the body, measurements may then be taken of the skin conductivity as the position of the catheter device in the sphenoidal sinus is varied. When the maximum skin conductivity is detected (i.e., the greatest amount of sweating is detected), the optimal location for the catheter device may be determined.
One purpose of the system described herein is to lower the core body temperature of the patient to a desired level. As such, a sensor may be employed to monitor the core body temperature of the patient. This sensor may be located on an area of the patient which provides indications of the body core temperature, such as the tampanic membrane, esophageal, or nasopharyngeal. Feedback signals received by the control module from the temperature sensor may be employed to vary the amount of radiant energy emitted from the catheter device which in turn varies the core body temperature.
The core body temperature may come into use after the catheter device has been optimally positioned and the process for lowering the core body temperature is begun. The magnitude of the radiant energy may be increased to provide heating of the POAH so as to induce mild hypothermia. As the heating progresses, the POAH further initiates the thermoregulatory cooling processes.
As the core body temperature decreases, this is detected by the core body temperature sensor. Because the cooling of the core body temperature may also acts to cool the POAH, the magnitude of the radiant energy emitted from the catheter device may need to be increased as core temperature drops. When the desired drop in core temperature is achieved, this condition may be monitored and automatically maintained by the system described herein. the control module may make the necessary changes in radiant energy output and/or cooling in order to maintain the desired core body temperature.
After the core body temperature has been lowered for the desir
Dvorak Linda C. M.
Marsh & Fischmann & Breyfogle LLP
Medivance Incorporated
Ruddy David M.
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