Abstract:
An apparatus for effecting hyperthermia in a narrow body cavity or duct including: a disposable first part ( 1 ) having an elongate distal section ( 5 ) intended to be inserted into the cavity or duct having a centrally located, heat-releasing element ( 22 ), which is either surrounded by an elongate housing ( 24 ) or is itself constituted by an elongate housing, and a flexible and/or elastic enclosure ( 23 ) surrounding the housing in a liquid-tight manner, further including a device for supplying energy to the heat-releasing element ( 22 ) and an axially operating first inlet ( 135 ) at the proximal part of the housing, an outlet ( 133 ) from the housing being arranged for the supply of heat-transmitting medium under pressure for expansion of the flexible enclosure ( 23 ) to accommodate and to exert a controlled pressure on surrounding walls of the cavity or duct, a second inlet ( 131 ) to the housing ( 24 ), and medium-actuating device ( 13, 19 ) for the expansion of the flexible enclosure ( 23 ) and for internal circulation of the medium through the housing ( 24 ); and a permanent non-disposable second part ( 51 ) having a drive ( 55, 75 ) for the device ( 13, 19 ) for expansion and for internal circulation, and a connection ( 43, 59; 41, 81 ) for releasably interconnecting the drive ( 55, 75 ) and the device means ( 13, 19 ) for expansion and internal circulation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for effecting hyperthermia in a narrow body cavity or duct. The invention is especially applicable to the treatment of the endometrium of the uterus. The treatment resides in a combination of the supply of heat to said body cavity or duct and simultaneous application of a controlled pressure on surrounding tissue. 
     2. Background Art 
     In the treatment of certain disorders in narrow body cavities or ducts the supply of heat is frequently used, the treatment residing in so called hyperthermia. For use in such treatment several apparatuses have been described including a special catheter employing a balloon attached to the distal end of the catheter. In the treatment of for example menorrhagia the distal end of the catheter including the balloon is inserted into the uterus cavity via vagina and cervix, the balloon being them  then expanded using a pressure medium up to a suitable pressure. The catheter includes heat-releasing means, for example an electric resistance element, to which electric energy is supplied from the exterior via the catheter, the generated energy and the temperature being controlled in different ways (see for example PCT/US89/03916). 
     In copending application PCT/SE92/00645 there is described an apparatus for carrying out hyperthermia involving the use of a heat-releasing element which is of an inherently self-regulating type. Examples of such elements are elements based on materials of the PTC-type or ferromagnetic materials where the means for the supply of energy are based on magnetic induction. In accordance with said PCT-application the problem of creating sufficient power output while avoiding self-inhibition associated with a heating element of the self-controlling type has been solved by arranging the element in a surrounding elongate housing through which the heat-transmitting medium is forced through and around the element by efficient internal circulation. Such internal circulation around and through the heat-releasing element is generated by providing a reciprocating movement of a small quantity of the pressurized quantity of heat-medium. 
     For details concerning this background art reference is made to the above-identified patent application PCT/SE92/00645, the full disclosure of which is incorporated herein by reference. 
     In apparatuses as those described above the balloon catheter is thus connected to sources for the supply of a liquid medium, electric energy and means for the control of the temperature and the supply of energy. In the apparatus according the above-mentioned PCT-application no means for temperature control are necessary but means for the generation of a reciprocating movement of a small quantity of the liquid medium will be required. 
     In the device according to the above PCT-application the liquid medium transferring heat to the area to be treated is in the form of a sterile liquid enclosed in a catheter, the distal part of which carries a distensible enclosure or balloon intended to be inserted in for example a uterus cavity. Due to this arrangement it is clear that not only the exterior parts of the catheter but also the interior thereof must be capable of cleaning and sterilization after use in view of the fact that leakage can result in infection of the enclosed liquid and thereby also the catheter parts. Even if a catheter is of a disposable type and is disposed of after use the means connected to the catheter, such as the means for generating pressure and internal circulation, will have to be cleaned and sterilized after every use since they have been in contact with the liquid medium. Such cleaning and sterilization is a very complicated and expensive procedure. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The present invention has for an object to provide a system meeting and requirements as to sterility. 
     Another object of the invention is to provide an apparatus where any risk of contamination from a preceding treatment is excluded. 
     Yet another object of the invention is to eliminate the risk for contamination and transfer of infection at a low cost for each treatment. 
     Still another object of the invention is to enable control and adjustment of the optimum average pressure during the course of treatment. 
     A further object of the invention is to provide a system through which excessive pressures hazardous to the patient can be avoided. 
     These and other objects will be obtained in accordance with the present invention by an apparatus for effecting hyperthermia in a narrow body cavity or duct, said apparatus being composed of a first disposable part comprising all constructional details subject to contamination, and a permanent non-disposable second part comprising the equipment necessary for operating the apparatus. 
     Accordingly, the present invention provides an apparatus for carrying out hyperthermia in a narrow body cavity or duct, said apparatus comprising: 
     a disposable first part comprising an elongate distal section intended to be inserted into said cavity or duct comprising a centrally located, heat-releasing element, which is either surrounded by an elongate housing or is itself constituted by an elongate housing, and a flexible and/or elastic enclosure surrounding said housing in a liquid-tight manner, further including means for supplying energy to the heat-releasing element end an axially operating first inlet at the proximal part of the housing, an outlet from the housing being arranged for the supply of heat-transmitting medium under pressure for expansion of the flexible enclosure to accomodate and to exert a controlled pressure on surrounding walls to said cavity or duct, a second inlet to the housing, and medium-actuating means for said expansion of the flexible enclosure and for internal circulation of said medium through the housing; and 
     a permanent non-disposable part comprising drive means for said means for said expansion and for internal circulation, and connecting means for unfastenably interconnecting said drive means and said means for expansion and internal circulation. 
     In a preferred embodiment of the apparatus of the invention said medium-actuating means comprise a first means for the expansion of the flexible enclosure and a second means for the internal circulation of the medium. 
     It is particularly preferred that said first means for the expansion of the flexible enclosure by introduction of heat-transmitting medium thereto is capable also of bringing the enclosure into a collapsed condition enabling withdrawal of the instrument from the body cavity or duct. 
     It is preferred that said second means involves the use of a reciprocating element creating a reciprocating motion to a determined quantity of pressurized medium. Said reciprocating element is suitably part of an injection syringe, although it is conceivable to use other types of reciprocating elements, such as a bellows or a deformable non-elastic container, as will be illustrated in the following description of preferred embodiments. 
     Said first means for the expansion of the flexible enclosure may likewise be constituted by an ordinary injection syringe, but also in this case the syringe can be replaced by other devices capable of performing the same function, which is also illustrated more in detail below. 
     For the creation of a reciprocating motion to said reciprocating element it is suitable to use a device comprising an eccentric capable of converting a rotary motion to a rectilinear motion. 
     Said means for expansion and for internal circulation can be either constituted by two different syringes separately operable for expansion on the one hand and for internal circulation on the other hand. As an alternative one and the same syringe can be used for providing both expansion and internal circulation, thus simplifying the construction. 
     According to still another aspect of the invention the apparatus can be supplemented with a pressure control system residing in a second distensible enclosure, the interior of which is in communication with the interior of said flexible enclosure, whereby any undesired pressure arising in the flexible enclosure will be released through distention of said second enclosure. 
     In such embodiment it is preferred that the second enclosure has a higher resistance to distention than the flexible enclosure associated with the distal part of the catheter. 
     In a preferred embodiment of such supplemented apparatus there is arranged a non-elastic container surrounding the second enclosure, and such container is suitably provided with means for controlling the pressure within the container and outside of the second enclosure. In this manner the level of release of an arising excessive pressure can be adjusted. 
     In the above-identified PCT/SE92/00645 application a number of embodiments relating to the internal circulation system are described. Furthermore, said application describes different types of heat-releasing elements, a preferred type being a heat-release element based on a PTC-material. For details regarding such features reference is made to said PCT-application. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will in the following be further described by exemplifying embodiments which, however, must not be construed to restrict the scope of protection except as defined in the appended claims. These embodiments are described in connection with the appended drawings, wherein: 
     FIG. 1 diagramatic illustration of a disposable first part of an embodiment of the apparatus according to the invention; 
     FIG. 2 is a diagramatic representation of combined disposable first part and permanent non-disposable part of the apparatus the present invention; 
     FIG. 3 is an enlarged side-view of a detail of the embodiment of FIG. 2; 
     FIG. 4 is an enlarged side-view of another detail of the embodiment shown in FIG. 2; 
     FIG. 5 is an enlarged side-view of a detail of the part shown in FIG. 4; 
     FIG. 6 is a side-view of an alternative arrangement using only one syringe for both expansion and internal circulation; 
     FIG. 7 is a section along line A—A of FIG. 6; 
     FIG. 8 shows in enlargement a longitudinal section through the central body  21  of the embodiment shown in FIGS. 1 and 2; 
     FIG. 9 shows a corresponding section of an alternative embodiment of the central body  21  of the embodiment shown in FIGS. 1 and 2; 
     FIG. 10 shows a side-view of an embodiment alternative to that shown in FIG. 3; and 
     FIG. 11 is an embodiment alternative to that shown in FIG.  4 . 
     FIG. 12 shows a diagram on the present/volume relation in using a pressure control device; and 
     FIG. 13 shows an embodiment of the device of the invention harbouring such a pressure control system through which hazardous excessive pressures can be avoided. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An embodiment of the apparatus according to the present invention is shown in full in FIG. 2, whereas the disposable first part thereof is shown in FIG.  1 . Said disposable first part  5   7 includes a catheter part  3  and a distal part  5  for the application of heat and pressure at the site of treatment, in the present embodiment the uterus cavity. 
     The distal part  5  includes a central body  21  comprising a housing  24  and harbouring a heat-releasing element  22 , both having an elongate configuration. The central body  21  is surrounded by a thin flexible and elastic enclosure or balloon  23 , which is distensible under the influence of a pressure medium supplied to the interior of said enclosure  23  in a manner to be illustrated below. 
     The disposable first part  5   7 is furthermore provided with a proximal part comprising conduit means  9  with a first three-way valve  11  and a first attachment stud  12 . As shown in FIGS. 1 and 2 conduit means  9  contains an access pipe  10  for the accomodation  accommodation of electrical leads extending up to the heat-releasing element  22 . Said leads are suitably connected to a voltage source, such as rechargable  rechargeable low-volt batteries. Said conduit means  9  additionally includes a side-conduit  16  attached at its end to said first three-way valve  11  and including a second three-way valve  15  and an associated second stud  14 . At the other end side-conduit  16  contains a leak-tight housing  18  having an elastic membrane to which a pressure sensor can be attached from the outside for pressure control purposes. 
     Proximal part  9  further includes two injection syringes  13 , 19  for a purpose to be described below. Each syringe  13 , 19  is provided with a housing or body  25  and  27 , respectively, and their respective front dispensing ends  29  and  31 , respectively, are leak-tightly connected to studs  12  and  14 , respectively. Syringes  13 , 19  are furthermore provided with conventional pistons  33 , 35 , respectively, each piston having its piston bar  37  and  39 , respectively, and actuating plates or discs  41  and  43 , respectively. Finally, syringe housings  25 , 27  are each provided with an outer circumferential flange  45  and  47 , respectively. 
     As previously indicated FIG. 2 illustrates the assemble apparatus including the disposable first part  7  and a non-disposable part  51  for repeated use. Said non-disposable part  51  includes support or platform  53  onto which the different parts of the auxillary equipment are attached. 
     As seen in FIG. 2, syringe  19  is associated with drive means  55 , whereas syringe  13  is associated with drive means  75 . 
     Referring now to FIGS. 4 and 5 drive means  55  for syringe  19  include a piston bar actuator  57  slideably mounted on platform  53  in the direction of arrows a). Actuator  57  includes a connecting element  59  with a slot  61  for receiving actuating plate or disc  43 . Furthermore, actuator  57  contains a through-hole  63  for a threaded bar  65  having an operating nob  67  at its free end and rotatably but axially fixed at its other end. Finally, actuator  57  is provided with a side-opening  69  containing a radially displacable threaded element  71 , the function of which is explained further below. 
     As seen in FIG. 4 syringe  19  is arranged on a bed  56  attached to a plate  59  which in turn through a spacer  68  is attached to platform  53 . Bed  56  is provided with a slot  60  for receiving the outer circumferential flange  47  of syringe  19 . 
     FIG. 3 illustrates in more detail drive means  75  associated with syringe  13 . Again, syringe  13  is arranged on a bed  73  attached to the upper side of platform  53  and is provided with a slot  74  for receiving the outer circumferential flange  45  of syringe  13 . Said drive means  75  are provided with an actuator  77  for piston bar  37  of syringe  13 . Actuator  77  is slideably mounted on platform  53  in the direction of arrows b), and has an upper part  81  provided with a recess or slot  79  for receiving actuating plate or disc  41  of syringe  13 . Actuator  77  is furthermore provided with a lower part  83  linked to a rotating excenter disc  87  via an arm  85 . 
     FIGS. 6 and 7 disclose an alternative embodiment of the apparatus of the inventions wherein syringes  13  and  19  are replaced by one single syringe capable of performing two functions as will be described in the operation of the apparatus below. This alternative arrangement according to FIGS. 6 and 7 has the single syringe  13  arranged axially slideable on a bed  89  and contains as before an outer circumferential flange  45 . Drive means  75  correspond closely to those described in connection with FIG.  3 . 
     In this alternative embodiment there is arranged an alternative drive means  55 ′ largely corresponding to drive means  55  illustrated in detail in FIGS. 4 and 5 but performing the same function in a different manner. Drive means  55 ′ are provided with an-upper part  91  extending above platform  53  and provided with a slot  93  receiving flange  45  of syringe  13 . Its lower part  57  corresponds functions-wise to actuator  57  according to FIGS. 4 and 5. Actuator  57  with its upper part  91  is slideably arranged in platform  53  in the direction of arrows a). Threaded bar  65  is rotatably arranged but axially fixed in a block  66  attached To platform  53  underneath thereof. The remaining parts of drive means  55 ′ are designed and perform in the same manner as described in relation to drive means  55  of FIGS. 4 and 5. FIG. 7 shows an illustrative cross-section along line A—A in FIG.  6 . 
     FIGS. 8 and 9 show two embodiments of the central body  21  including the heat-releasing element  22  and the flexible or elastic enclosure or balloon  23  according to FIG.  1 . 
     FIG. 8 shows a detail a system from enabling effective heat transport and heat transfer from the heat-emitting element  119  to the uterus mucosa (endometrium). Element  119  contains wires  115  for electrical resistance heating thereof. Wires  115  are supplied with electric energy via leads  116  entering through canal  135 . Apertures  131  in the proximal part of the tubular central body operate as radially acting inlets for a pressurized liquid medium to a valve housing  132  communicating with an inlet canal  135 , the space between central body  21  and enclosure  23 , as well as with canals  121  arranged about and through the heat-emitting element  119  in the middle part of the central body  21 . Apertures  133  arranged in the distal part of the central body  21  act as outlets for the pressurized liquid medium from a second valve housing  139  communicating with canals  121  and the space between the central body  21  and the elastic enclosure  23 , said enclosure being liquid-tight sealed around the proximal part of the central body at  151  and being attached to a nose member  141  of the central body. In valve housing  132  back valves  149  are arranged so as to close apertures or openings  131  at over-pressure in the valve housing  132  and opening at a sub-pressure relative to the liquid pressure in the space between central body  21  and the elastic enclosure  23 . A partition  143  having openings  145  is arranged in valve housing  139 . A disc valve  147  is moveable in an axial direction and arranged so as to close openings  145  at over-pressure in valve housing  139  relative to the liquid pressure in canals  121  in the heat-emitting element of the central body or opening at sub-pressure in valve housing  145 , respectively. 
     FIG. 9 shows in detail a central body  21  containing heat-releasing elements  157  of an inherently self-regulating type, such as PTC-material or ferromagnetic material having a Curie point. Element  157  also contains canals or passages  121 , and said elements  157  and canals  121  are surrounded by a housing  29 . In other respects the embodiment of FIG. 9 corresponds to that of FIG. 8 but with the difference that the disc valve  147  and the associated partition  143  with apertures  145  are now arranged in the proximal part of central body  21 . Between the inlet side of the wires  153  and the partition  143  a chamber  155  is arranged. 
     FIG. 9 shows how the liquid medium is forced to circulate into chamber  145  and further in through the wire package  157  at a pressure shock at the same time as valves  149  close apertures  131 . 
     The procedure for performing hyperthermia in a uterus cavity using the apparatus described above including the function of said apparatus will now be explained more in detail. 
     The disposable first part  7  can be stored in a sterile package separate from the stationary part up to the time of treatment when it is assembled with the stationary part  51  in the manner indicated above. Although said disposable first part  7  contains a number of elements performing the necessary functions for the operation of the apparatus according to the invention it is interesting to note that all parts thereof, in order to obtain a disposable assembly, can it be produced in large series at a direct cost not amounting to approximately more than between say 25 and 50 USD. 
     At preparation for treatment the syringe  19  is filled with somewhat more than the quantity of sterile liquid medium required to fill up the system and is then connected to stud  14 . By maintaining the disposable part  7  in a vertical position with syringe  19  in a vertical uppermost position and imparting short movements to piston  35  of syringe  19  the system will be filled with liquid and at the same time air can be removed from the system and collected in syringe  19 . Syringes  19  and  13  can easily be freed from air by disconnecting them from the system. Syringes  19  and  13  are then connected to their respective studs and piston of syringe  19  is positioned so that the enclosure  23  remains in a collapsed condition. The distal part  3  of the applicator is then inserted through vagina, cervix and into the uterus cavity up to the bottom of the cavity. The length of the central body  21  corresponds approximately to the length of the uterus cavity, i.e. normally 4 to 6 cm. Next, syringe  19  is attached with its operating end to drive means  55  by inserting disc  43  into slot  61 . Syringe  13 , partially filled with liquid, is attached with its rear operating end to drive means  75  by inserting disc  45  into slot  79 . Three-way valves  11 , 15  are set so as to establish communication between syringes  19  and  13  and the interior of enclosure  23 , and piston  35  is pushed forward within syringe  19  to expand the flexible enclosure  23  to conform to the surrounding uterus wall. Piston  35  is pushed forward until the desired pressure is reached as recorded by the pressure sensor. 
     As seen in FIGS. 4 and 5 drive means  55  can be used for free movement of piston  35  in syringe  19  by retracting threaded element  71  to the position shown in FIGS. 4 and 5. On the other hand, by pushing threaded element  71  into engagement with the threaded bar  65  fine adjustment of the position of piston  35  can be attained by rotating nob  67 , whereby fine adjustment of the pressure in the system can be attained. 
     After the filling procedure drive means  75  are started imparting to the piston  33  of syringe  13  a reciprocating motion. At every positive pressure shock a certain volume of liquid is brought to move forward through the conduits up to the inlet canal  135  of the central body (FIG.  8 ). This has for an effect that simultaneously a corresponding quantity of pressurized liquid medium is forced through canals  121  in the central body  21  in view of the fact that valves  149  are closed at the same time as valve  147  is opened, and a corresponding quantity of pressurized liquid medium will be pushed out into the space inside the flexible enclosure  23 . 
     At every subsequent backward movement of the piston of syringe  13  a corresponding quantity of liquid medium will be sucked back, valves  149  taking the open position shown in FIG.  8  and valve  147  its closed position. It is appreciated that under the influence of the oscillating pressure shocks and the described valve system a powerful and effective circulation in an internal flow circuit of liquid medium at the pressure given by syringe  19  will be provided through canals  121  of the central body  21  and out into the space within the balloon enclosure and back to the central body without hot liquid passing the inlet canal  135  of the catheter to the other parts of the apparatus. Thus, circulation takes place only in the distal part of the apparatus, whereas the inlet canal  135  during circulation only serves as a communication conduit for transmitting in a hydraulic manner the oscillating pressure and liquid movement provided by syringe  13  and for maintaining the desired pressure in the system by means of syringe  19 . 
     In the treatment using the apparatus according to the present invention the pressure used in the system varies from case to case and may also vary during the treatment of one and the same patient, in view of for example variations in blood pressure, contractions of muscular tissue etc. A suitable pressure range lies within the interval between about 120 and about 170 mm Hg, and a suitable temperature of the circulating liquid is about 65° to 90° C. The period of treatment for obtaining the desired result varies within relatively wide limits but satisfactory results are usually obtained with a time of treatment varying from about 20 to about 30 min. 
     In order to obtain satisfactory internal circulation it has been found that a reciprocating frequency for the means for internal circulation lies between about 300 and 1000 strokes per min at a stroke volume of about 0.1 to 0.5 ml. It is to be noted that these values are to be considered only as suitable guidelines and other values lying outside of the ranges given are fully conceivable. 
     By considering the illustrations of FIGS. 1 and 2 it is appreciated that FIG. 2 shows the disposable first part  7  which, after use, can be disconnected from the non-disposable stationary part  51  and is then transferred to a destruction site so that infection through contamination can be avoided. The stationary part  51  will be completely free of any contamination and can be used repeatedly. 
     The stationary part  51  can additionally contain sources of electric energy, electrical leads and it can also contain a unit for the control of pressure, temperature and time and suitable displays for visualizing the corresponding parameters. 
     The embodiment shown in FIGS. 6 and 7 using only one syringe  13  for performing both filling and pulsating functions operates in a similar manner, although expanding the enclosure is performed by operating drive means  55 ′ to move the body or housing  23  of syringe  13  relative to the piston  33  and the bed  89  in an axial direction. After the expanding operation the body  25  of syringe  13  is maintained in a fixed position by bringing threaded element  71  in engagement with the threaded bar  65 , whereafter drive means  75  is started to perform the function of providing internal circulation in the same manner as the device shown in FIG.  3 . 
     FIG. 10 shows an arrangement which constitutes an alternative to the embodiment shown in FIG.  3 . This alternative drive means  75  is arranged on platform  33 , and syringe  13  of FIG. 3 has been replaced by a device  36  comprising an elongate hollow body  32  and, attached at the rear end thereof outside of flange  45 , a bellows  46  which at its rear end in turn carries actuating plate or disc  41 . 
     Operatively, the device of FIG. 10 operates in exactly the same manner as the arrangement described in connection with FIGS. 2 and 3 to provide for effective circulation in an internal flow circuit of liquid medium. 
     In FIG. 11 there is shown an arrangement which constitutes an alternative to the embodiment shown in FIG. 10, where syringe  13  of FIG. 3 has been replaced by another device  38 . Driving device  75  as shown in FIG. 3 is not illustrated in FIG. 11 except element  59  that has been modified to match new device  38  replacing syringe  19 . 
     Device  38  contains a hollow elongate body  34  having an exterior circumferential flange  45  engaging a slot in bed  57  in the same manner as shown in FIG.  3 . At the rear end of body  34  there is arranged a flexible inelastic container  48  which is connected to element  59  of drive means  55  through a bar  50  having at its free end a ball  52  fitting into a recess  54  of element  59 . 
     The device shown in FIG. 11 can thus be used to replace syringe  13  shown in FIG. 2 using the eccentric device of FIG. 3 for providing reciprocation of element  59  resulting in internal circulation as previously described. In such pulsation, container  48  of FIG. 11 moves between the position shown in full line and the position shown in dotted line at  42 . 
     Even if an indicated above there are alternative embodiments, wherein the syringe  19  and  13  according to FIG. 1 have been replaced with other devices illustrated in FIGS. 10 and 11, the embodiment according to FIG. 1 involving syringe  19  is preferred. On the one hand, such syringes can be massproduced at a very low cost and, on the other hand, as already described such a syringe can easily be deairated and filled with liquid, respectively, through an operation well known to the operator. Furthermore, syringe  19  can be graduated, such as with a milliliter scale, so that the operator will know the quantity of liquid injected into the system. 
     When using drive means  55 ′ and  55 ′, according to what has bee described in connection with FIGS. 4 and 5 and FIG. 6, respectively, fine adjustment of the system pressure can be made, and practice has also shown that this is necessary. 
     As earlier described the distal section  5  of the device, the enclosure being in a collapsed condition, is inserted into the uterus cavity, piston  35  of syringe  19  being then pushed forward to expand the enclosure. As long as the expansion takes place without the walls of the enclosure touching the walls of the cavity the expansion takes place at a low pressure depending inter alia on the elastic properties and thickness of the material of the enclosure. As a rule a highly elastic, thin enclosure material is desirable in order to obtain maximum compliance with the irregular inside surface contour of the uterus cavity while offering at the same time efficient heat transfer from the liquid medium to the endometrium. 
     To the extent that the enclosure in its expansion comes into engagement with the major part of the interior surface of the uterus cavity the resistance of the uterus muscle towards expansion will increase, the pressure in the system increasing at a higher rate for every volume of liquid injected. Pressure versus volume is indicated in FIG.  12 . Curve  1  in full line shows said relation in the free expansion of a thin-walled elastic enclosure suitable for the treatment of uterus in accordance with the present invention. As seen from the figure a certain initial pressure (about 70 mm Hg) will be required for a first small expansion (about 1 ml). Then the expansion takes place at a slowly increasing pressure (about 70-100 mm Hg) that can be designated the plateau pressure. As earlier mentioned the curve will take another shape when the enclosure is brought to expand in for example a uterus cavity. 
     FIG. 12 shows two curves A-C and B-D with dashed lines the pressure/volume relation with two different cavity sizes. As seen from the figure the curves increase quite steeply depending on the resistance of the uterus muscle. According to the invention it is intended to open the cavity by expansion of the enclosure so that the whole interior surface of the cavity will be subjected to heat treatment at the same time as the circulation of blood will be reduced so that a more efficient and deeply penetrating heat destruction can be obtained. However, it is important that uterus will not be subjected to an excessive pressure which can cause damage through tissue failure. It has been found that a suitable pressure lies within the range about 100 to 140 mm Hg. Higher pressures can be used but the pressure should not exceed abouth 170 to 180 mm Hg. Even if for example such a device for fine adjustement of the pressure as described in connection with FIG. 4 will be used the steep increase in pressure at a small change of volume constitutes a problem, inter alia in view of the fact that the living muscle does not give a constant resistance. In certain cases strong contractions arise in the muscle, which could result in a drastic increase pressure if a rapidly acting pressure release cannot be provided. 
     It is conceivable to arrange for servo control of the device for fine adjustment as described so that the pressure can be maintained between two pre-determined values, but such system is complicated and is not always rapid enough in order to compensate for for example muscle cramps. 
     FIG. 13 shows a pressure control device which in a simple and efficient manner provides for facilitated adjustment of pressure and enables pressure release upon sudden pressure increase resulting from for example contraction of uterus. Said control means designated  101  has been added to =he  the disposable part  7  shown in FIG. 1, via a second side conduit  103  connected to side conduit  16  of the disposable part  7 . Control device  101  contains a central tube  105  provided with holes  107 . Said tube  105  is surrounded by an elastic balloon  109  which is thereby connected to the disposable part  3  so as to be filled with liquid when the system is filled using syringe  19 . When pressurizing the system elastic balloon  109  then expands, such as to the position  109 ′ shown in full line in FIG.  13 . 
     In accordance with the invention there is selected for balloon  109  an elastic material of for example silicon. The plateau pressure of said material is substantially higher than the plateau pressure for enclosure  23  but somewhat higher or equal to the pressure suitable for the treatment. 
     The pressure/volume relation for a suitable material is shown in FIG. 12 by curve  12  in dotted line. As is clear from FIG. 12 the plateau pressure lies within the range about 180 to 200 mm Hg. 
     The system including pressure control device  101  is pressurized as described in connection with FIGS. 4 and 5, but the pressure/volume relation will be different in view of the fact that also balloon  109  will expand during the pressure increase. 
     FIG. 12 shows how the pressure increase AC changes to AE and how the pressure increase BD changes to BF. The change obtained by adding the pressure control device  101  to the system results on the one hand in the advantage that the pressure increase within the range 80 to 150 mm Hg is less steep, i.e. easier to control. On the other hand, the pressure increase at pressures exceeding about 160 mm Hg is very slow. In this case a suitable operating pressure is about 150 to 160 mm Hg. This means for example that at a sudden contraction of uterus the pressure increase from the pre-set pressure will be relatively small so that damages to uterus can be prevented. The reason as to why drastic pressure increase can be prevented is the fact that if enclosure  23  will be compressed through contraction of uterus a corresponding quantity of liquid will be transferred to balloon  109 . If the contraction of uterus ceases a corresponding quantity will be transferred back from balloon  109  to enclosure  23 . 
     As is clear from the above description the supplementary equipment residing in pressure control device  101  is simple end  and cheap in manufacture and belongs to the part of the equipment that is disposed of after use. 
     In certain cases it can be of advantage to be able to vary the plateau pressure of the balloon  109 . This can be done by surrounding balloon  109  with an airtight container  111  shown by the dashed square in FIG.  13 . Container  111  can be provided with pressurizing means, such as a manual operated pump, not shown it FIG.  13 . By pressurizing container  111  the plateau pressure of balloon  109  can be set at the desired value. In this manner different plateau pressures can be obtained using one and the same balloon  109 .