Surgery – Instruments – Heat application
Reexamination Certificate
2000-03-01
2002-09-03
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Heat application
C606S031000, C607S105000
Reexamination Certificate
active
06443947
ABSTRACT:
TECHNICAL FIELD
The disclosed invention relates to an apparatus or device for effecting hyperthermia in a body cavity or duct. More specifically, the invention relates to apparatus and methods using a balloon or similar flexible bladder which is inserted into the uterus and filled with a heated liquid at a known pressure and for a known time in order to cauterize (“ablate”) the endometrium of the uterus. This method of treatment is known as “thermal balloon ablation”.
BACKGROUND AND SUMMARY OF THE INVENTION
Medical treatments involving ablation of the endometrium of the uterus are well known in the prior art. The endometrium is the portion of the uterine lining to which an embryo normally attaches and is responsible for the menstrual cycles. Such ablation treatments typically involve either the direct or indirect application of heat or cold to the endometrial tissue. Commonly, ablation devices and techniques have been used to treat menorrhagia (a condition of excessive menstrual bleeding) by cauterizing, or inducing necrosis of the endometrial lining. This cauterization prevents further proliferation of the endometrium and may result in permanent relief of menorrhagia symptoms.
Apparatuses for thermal balloon ablation are well known in the prior art. For applications to treat the endometrium of the uterus, thermal balloon ablation apparatuses typically comprise a distensible balloon which is inserted into the uterus through the external opening of the cervix. The balloon is then inflated with a liquid to expand the balloon such that it is in contact with substantially all of the uterine cavity. This liquid is then heated to a controlled temperature by a heating element within the balloon and the liquid is maintained at this temperature for a predetermined period of time. After this period of time has elapsed, the liquid is withdrawn and the balloon removed from the uterus. The heat energy which is transferred from the liquid filled balloon to the surrounding tissues of the uterus causes the desired cauterization of the endometrium. There are many examples of such devices in the prior art, for example those disclosed by Stevens et al—U.S. Pat. No. 5,800,493, and Wallsten et al—U.S. Pat. Nos. 5,693,080 & 5,571,153.
Typically the volume of liquid required to inflate the balloon ranges between 5 ml and 30 ml and is dependent on the natural volume of the uterine cavity and the liquid pressure. According to studies published in the medical literature, the liquid pressure should not exceed 180 mmHg applied to the uterine cavity walls above which there is risk of mechanical damage to the deeper tissue of the uterus.
Variations on thermal balloon apparatuses and methodologies include cryogenic apparatuses which use cooled liquid rather than heated liquid to achieve necrosis of the tissue (such as that disclosed by Lafontaine et al—U.S. Pat. No. 5,868,735) and apparatuses in which heated liquid is circulated through the uterus without the benefit of a flexible balloon to contain the liquid (such as that disclosed by Goldrath—U.S. Pat. No. 5,437,629).
A variety of alternatives to thermal balloon ablation are known for cauterization of endometrial tissue. These includes the use of microwave, RF, laser, electrical current or similar energy sources to heat a surgical probe inserted through the cervix and which is manipulated by means of direct hysteroscopic visualization. These devices typically require a highly skilled operator and produce treatment results which are more variable than those which can be achieved through thermal balloon ablation techniques. Such alternative ablation techniques also pose higher risk of perforating the uterus, normally require use of general anesthesia, and have a higher incidence of post-operative complications than thermal balloon ablation techniques.
In spite of the potential advantages of thermal balloon ablation techniques over alternative treatment methodologies, problems with the thermal balloon ablation apparatuses in the prior art have prevented such devices from being adopted widely for use in the treatment of menorrhagia.
Thermal balloon ablation systems in the prior art typically rely on heating elements located within the balloon. During heating, these devices often develop temperature gradients in the liquid which can result in uneven treatment of the endometrial surface. Typically the observed effect is to over-treat the area of the endometrium directly above the heating element and under-treat the area of the endometrium located directly below. This effect is magnified if the heating element within the balloon is inserted at an angle relative to the anterior/posterior plane of the uterus such that after inflation the heating element is located closer to the anterior wall of the balloon. Placement of the heating element relative to the balloon walls is difficult to control in practice. To reduce this problem, some inventions in the prior art include provision of an impeller, reciprocating piston or similar mechanical means to stir the liquid during heating (such as those disclosed by Neuwirth et al—U.S. Pat. No. 5,460,628 and Saadat et al U.S. Pat. No. 5,827,269) or utilize balloons which allow injection and re-circulation of heated liquid via multiple lumens, typically an “intake” lumen and an “exhaust” lumen (such as that disclosed by Lafontaine et al—U.S. Pat. No. 5,868,735). Furthermore, pulsing the liquid pressure is an alternative means to achieve more uniform mixing of the liquid (as described by Wallsten et al U.S. Pat. No. 5,957,962). However, such circulating methodologies add cost and complexity to the apparatus and the ability to achieve desired temperature uniformity depends among other factors on the volume of liquid within the balloon.
Thermal balloon ablation devices in the prior art such as that disclosed by Stevens et al—U.S. Pat. No. 5,800,493 have also relied on the operator to provide the liquid for inflation of the balloon and heating. This has limited the variety of liquids to those typically found in a clinical environment (e.g. D5%W or saline). Such liquids are generally water based and therefore cannot be heated above approximately 100 C., at which temperature these solutions begin to boil at sea level. Heating liquid to the boiling point can result in a dangerous increase in balloon volume due to expansion of gas and in uneven treatment since the presence of this gas pockets in the balloon act to thermally insulate the adjacent tissue. The maximum temperature limitation of these liquids has resulted in relatively long treatment times; it is well established in the research and in clinical practice that it requires in approximately 8 minutes to cauterize the endometrium by thermal balloon ablation using liquid temperatures of 85 C. Furthermore, the use of liquid temperatures in the range of 70-90 C. makes the use of liquid heating means external to the uterus or balloon ineffective since in this temperature range there is insufficient heat energy contained within the volume of liquid within the uterus to adequately cauterize the endometrium. In devices that employ heating means external to the balloon in the uterus and which use liquid temperatures below 100 C. (such as that disclosed by Chin U.S. Pat. No. 5,449,380) it is generally necessary to continuously circulate the liquid between the balloon and the external heating means in order to maintain an elevated liquid temperature within the uterus and to achieve the desired treatment. In addition, devices with heating elements located in the balloon within the uterus prohibit the use high viscosity liquids (such as 100% Glycerin) which resist flow at ambient temperatures but once heated become less viscous and can readily flow through a catheter to inflate a balloon placed in the uterus.
Systems which require the operator to supply the inflation liquid are also complicated for the operator to use. It is necessary for the operator to obtain a source of sterile liquid, inject the liquid into the system, check for leaks, purge gas or excess liquid from the system, and t
Bruce Monty
Marko Alexei
McDougall Ian
Yackel Douglass
Dvorak Linda C. M.
ipsolon llp
Ruddy Daniel M.
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