Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-04-30
2002-10-08
Gibson, Roy D. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S108000, C607S112000
Reexamination Certificate
active
06461379
ABSTRACT:
FIELD OF INVENTION
The present invention generally relates to a method and apparatus for heat transfer with a patient, and more particularly to a method and apparatus for cooling and/or heating a localized tissue region of interest on a patient.
BACKGROUND OF THE INVENTION
The use of heating/cooling devices in medial applications is well established. By way of example, bodily heating may be employed for hypothermia patients. Hypothermia may occur, for example, in patients undergoing surgical procedures. It has been shown that nearly seventy five percent of all patients who undergo surgical procedures develop hypothermia from factors including anesthesia, air conditioning of the operating room, and infusion of cold blood or I-V solutions. Studies show that by reducing hypothermia, patient outcome is improved and recovery is quicker.
Further, bodily cooling has been proposed for stroke patients to reduce potential brain damage due to ischemia. In this regard, studies show that cooling the brain 2-3° C. yields neuro-protection that might hasten recovery. Additionally, during vascular procedures requiring circulatory arrest, a common technique is to cool the patient's core via cardiovascular extracorporeal perfusion to less than 15° C. In order to maximize protection of major organs, including the brain and spine, peripheral cooling may be employed to prevent rewarming via heat conduction from surrounding tissues.
To date, self-contained thermal exchange pads and other devices have been used for cooling and/or heating of a patient. Fluids, such as water, are circulated between layers of the thermal exchange pad to cool or heat the patient. For example, fluids colder/hotter than the patient's body temperature may be circulated through the pad to absorb/release heat from/to the patient, thereby achieving cooling/heating. While such devices have proven effective for many applications, the present inventor has recognized that further improved results are achievable in certain applications.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a method and apparatus for enhanced heat transfer with a localized tissue region of interest. The apparatus/method utilizes a membrane configured for covering a tissue region of interest and a spacing structure that maintains a spacing relation between an interior side of the flexible membrane and the tissue region of interest to define a fluid circulation space therebetween. Thermal exchange fluid may be drawn into the fluid circulation space through an inlet in the flexible membrane and out of the fluid circulation space through an outlet in the flexible membrane. In this regard, the fluid directly contacts the tissue region of interest. A related fluid circulation system includes a pump connected downstream from the fluid outlet and a fluid reservoir connected upstream from the fluid inlet. When operated, the pump draws thermal exchange fluid from the reservoir, into, and out of the fluid circulation space. Thermal energy is exchangeable between the tissue region of interest and the thermal exchange fluid circulated within the fluid circulation space to cool and/or warm the tissue region of interest.
The fluid may be circulated under negative or nearly negative gauge pressure which has several advantages. For example, the flexible membrane is not distended/expanded by the pressure of the circulated fluid and thereby fluid velocity over the tissue region of interest is maximized thus maximizing heat transfer. Circulating the fluid under negative or nearly negative gauge pressure also achieves inherent sealing at the edges of the flexible membrane as compared to a positive pressure situation. Further, direct contact of the fluid with the tissue region of interest also enhances heat transfer where the tissue region of interest is covered by hair (e.g. a person's head) as compared with a thermal exchange pad which contains the fluid and prevents direct contact of the fluid with the tissue region of interest.
According to one aspect of the present invention, an apparatus for local exchange of thermal energy with a tissue region of interest includes a flexible membrane having an interior side and an exterior side. The flexible membrane is configured for covering the tissue region of interest. The flexible membrane may be comprised of an elastic material, such as silicone rubber, natural rubber, an elastomer, a thermoplastic polyurethane or a latex material, to allow for stretching of the flexible membrane to facilitate positioning of the flexible membrane over a body element (e.g., over a patient's head). The apparatus also includes a spacing structure for maintaining the interior side of the flexible membrane in a spaced relation with the tissue region of interest to define a fluid circulation space therebetween. The apparatus further includes at least one fluid inlet and at least one fluid outlet communicating with the fluid circulation space. A thermal exchange fluid is circulatable through the fluid circulation space from the inlet to the outlet at or near a negative gauge pressure (i.e. pressure measured relative to ambient pressure). In this regard, the thermal exchange fluid may be circulated through the fluid circulation space at a gauge pressure ranging from slightly positive (e.g., about 0.1 psi) to substantially negative (e.g., about −10.0 psi).
The spacing structure may be comprised of one or more ribs, one or more studs, or a combination of both. The spacing structure may be integrally molded to the interior side of the flexible membrane and project from the interior side of the flexible membrane. However, the spacing structure may also be removably attached to the interior side of the flexible membrane or may even be a separate structure such as a net or the like that is disposable between the tissue region of interest and the interior side of the flexible membrane. The spacing structure may define a plurality of fluid flow paths from the fluid inlet to the fluid outlet. In this regard, the fluid flow paths are generally of equal length from the fluid inlet to the fluid outlet and inhibit the formation of boundary layers of stationary thermal exchange fluid that may reduce the overall efficiency of the apparatus.
The flexible membrane may also include a sealable edge. In one embodiment the sealable edge may comprise a strip, located on the periphery of the interior side of the flexible membrane that is free of any spacing structure (e.g. smooth). In another embodiment, the strip may include a plurality of elongated parallel ridges projecting from an interior side of the strip. In use, the ridges are forced into the periphery of the tissue region of interest such that portions between the ridges are approximately coplanar with the tissue region of interest. In another embodiment, the sealable edge may include an adhesive material disposed on the interior side of the strip. The adhesive aids in facilitating a tight seal between the sealable edge and the periphery of the tissue region of interest. In this regard, the adhesive on the seal should be comprised of a material having sufficient adhesive strength for holding the flexible membrane in place without having too great of an adhesive strength so as to cause tissue damage during removal. Generally, for best results, the sealable edge should be positioned next to a portion of the patient's skin that lacks substantial hair. The above-described embodiments of the sealable edge allow the sealable edge to grip the patient's skin, and thus help maintain the conformance of the flexible membrane to the tissue region of interest to limit unintentional movement of the flexible membrane.
According to another aspect of the present invention, a system for local exchange of thermal energy with a tissue region of interest includes a flexible membrane configured for covering the tissue region of interest and a spacing structure that maintains an interior side of the flexible membrane in a spaced relation with the tissue region of interest to define a
Carson Gary A.
Voorhees Marc
Gibson Roy D.
Marsh & Fischmann & Breyfogle LLP
MediVance, Incorporated
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