Abstract:
A device for dilating a body passageway. The device comprises an elongaed hollow shaft and a balloon at the distal end of the shaft in fluid communication with the lumen of the shaft, the balloon having at least a cylindrical portion. The balloon is formed from a flexible, unstretchable material capable of withstanding an inflation pressure of at least 10 bar. When the balloon in an uninflated state is collapsed onto the shaft the diameter of the balloon on the shaft is at most 35% of the diameter of the cylindrical portion in an inflated state.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to medical devices and more specifically to such devices for dilating a body passageway.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is often necessary to dilate a body passageway, such as a blood vessel, urethra, or cervix. In the case of the cervix, for example, it is sometimes necessary to dilate the cervix in order to allow access of surgical instruments into the uterine cavity during a medical procedure. Such procedures include induced abortion, completion of a spontaneous abortion, and operative hysteroscopy.  
         [0003]     The human cervix is a tubular structure between 2 to 5 cm in length. The cervical canal is usually closed, but a catheter having a diameter of 2 to 3 mm can be introduced into the cervical canal with only minor discomfort to a female patient in the absence of any anesthesia. It is usually required to dilate the cervix to a diameter between 10-12 mm.  
         [0004]     One known method for dilating the cervix uses Hegar dilators. These are essentially metal rods. A dilator of a relative small caliber is inserted into the cervix to achieve a small dilation. The rod is removed, and a rod of slightly larger caliber is inserted into the cervix. This rod is then removed, and the process repeated, each time with a rod of larger caliber, until the desired dilation has been achieved. This procedure requires some form of anesthesia, and may damage the cervix.  
         [0005]     U.S. Pat. No. 4,624,258 to Stubbs discloses a hygrometric dilator comprising an insertion body containing the vegetative stalks of Laminaria japonica. The insertion body is inserted into the cervix, whereupon the Laminaria expands as it absorbs fluids present in the cervix, causing the cervix to dilate.  
         [0006]     WO 81/01098 discloses a device for inflating a cervix comprising an inflatable latex balloon. The balloon is enclosed in a sleeve formed from an inelastic material in order to allow the balloon to withstand high pressures.  
         [0007]     U.S. Pat. No. 4,137,222 to Leininger discloses an inflatable device having an inflatable balloon with an enlarged bulbous portion at one end. When the balloon is inflated, the enlarged portion expands inside the uterus while the remainder of the balloon inflates in the cervix. The enlarged portion prevents the balloon from being expelled out of the cervix.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a device and method for dilating a body passageway. While the device will be described in relation to dilating a cervix, it should be understood that the device of the invention may be used to dilate other body cavities such as a urethra or blood vessel.  
         [0009]     The device of the invention comprises a hollow shaft having a distal end and a proximal end. The shaft typically has a diameter of about 1 to 2 mm. At the distal end of the shaft is an inflatable balloon. A pressurized fluid is made to flow in the lumen of the hollow shaft from the proximal end to the distal end so as to inflate the balloon. The balloon has at least a portion that is cylindrical in shape when inflated.  
         [0010]     The balloon is formed from a flexible essentially unstretchable material. The material of the balloon is further selected so that the inflated balloon can withstand pressures of up to 10 bar, more preferably 20 bar, and still more preferably, 30 bar. The wall of the balloon is sufficiently thin so that when the uninflated balloon is collapsed onto the shaft, the diameter of the balloon on the shaft is at most 35%, more preferably 30%, even more preferably 25% of the diameter of the inflated cylindrical portion of the balloon. The thickness of the wall of the balloon is preferably less than 0.1 mm, more preferably less than 0.08 mm, and still more preferably around 0.05 mm.  
         [0011]     For example, the inventors have found that a cylindrical balloon having an inflated diameter of 12 mm formed from polyethylene perephthalate (PET) or polyamide and having a wall thickness of 0.05 mm can withstand pressures up to at least 14 bar. Since the maximum pressure that a cylindrical balloon can withstand is proportional to its wall thickness, a balloon of this material and inflated diameter having a wall thickness of 0.10 mm can withstand pressures up to 28 bar. Similarly, a balloon of this material and inflated diameter having a wall thickness of 0.20 mm can withstand pressures up to 42 bar. A cylindrical balloon having an inflated diameter of up to 10 mm and a wall thickness up to 0.2 mm, will have, when collapsed onto a 1 mm diameter shaft, a diameter less than 3 mm.  
         [0012]     The balloon may optionally be formed so as to form a spherical bulb at the distal end of the inflated balloon having a diameter greater than that of the cylindrical portion. Alternatively, the device may comprise a cylindrical balloon and a separate spherical or ellipsoidal balloon. A distally located spherical balloon allows the cylindrical portion of the balloon to be properly positioned in the cervix, as described in detail below. Furthermore, a spherical balloon can withstand twice the pressure of a cylindrical balloon from the same material and wall thickness. Thus, in one embodiment, the device also includes a spherical balloon that is used, to expand a portion of the passageway.  
         [0013]     The proximal end of the shaft is adapted to be connected to a source of a pressurized fluid. The fluid is preferably an incompressible fluid such as water or saline. The fluid may be delivered from the proximal end of the shaft to the distal end of the shaft and into the balloon by any means of pressurizing the fluid. For example, the fluid may be loaded into a syringe that is placed in fluid communication with the lumen of the shaft. The fluid is then manually pressurized by displacing the piston of the syringe.  
         [0014]     In a preferred embodiment, the fluid is pressurized by an electrical pump that delivers the fluid through the shaft to the balloon at a predetermined flow rate. The flow rate is selected to be slow enough so as to inflate the balloon at a rate that does not cause severe pain to the patient. The device may thus be used without anesthetizing the patient.  
         [0015]     Since the balloon is formed from an unstretchable material, when an incompressible fluid is used to inflate the balloon, the volume of the balloon may be determined at any time from the amount of fluid delivered to the balloon. In particular, the maximum volume of the balloon is obtained when that volume of fluid has been delivered to the balloon.  
         [0016]     Thus, in its first aspect, the invention provides a device for dilating a body passageway comprising:  
         [0017]     (a) an elongated hollow shaft having a lumen, a proximal end and a distal end, and  
         [0018]     (b) a balloon at the distal end of the shaft in fluid communication with the lumen of the shaft, the balloon having at least a cylindrical portion, characterized in that: 
        (i) the balloon is formed from a flexible, unstretchable material capable of withstanding an inflation pressure of at least 10 bar.     (ii) when the balloon in an uninflated state is collapsed on the shaft, the diameter of the balloon on the shaft is at most 35% of the diameter of the cylindrical portion in an inflated state.        
 
         [0021]     In its second aspect, the invention provides a method for dilating a body passageway comprising inserting the cylindrical portion of the balloon of a device in accordance with the invention into the passageway and inflating the balloon. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:  
         [0023]      FIG. 1  shows a dilator having a balloon, in accordance with one embodiment of the invention;  
         [0024]      FIG. 2  shows the dilator of  FIG. 1  with the balloon in an uninflated state after insertion into a cervix,  FIG. 3  shows the dilator of  FIG. 1  after insertion into a cervix with the balloon in a partially inflated state;  
         [0025]      FIG. 4  shows the dilator of  FIG. 1  after insertion into a cervix with the balloon in an inflated state;  
         [0026]      FIG. 5  shows a dilator having two balloons in accordance with one embodiment of the invention;  
         [0027]      FIG. 6  shows a dilator having two balloons and a shaft with two lumens in accordance with another embodiment of the invention.  
         [0028]      FIG. 7  shows a dilator having two balloons in accordance with another embodiment of the invention; and  
         [0029]     FIGS.  8  to  11  show deployment of the dilator of  FIG. 7 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]      FIG. 1  shows a device for dilating a body passageway, in accordance with one embodiment of the invention. The device generally indicted by  2 , includes an elongated shaft  4  having a proximal end  6  and a distal end  8 . The shaft  4  has an outer diameter of 1 to 2 mm and encloses a lumen  10 . The shaft is formed from a flexurally resilient material such as plastic, stainless steel, or polyurethane. A blunt cap  5  at the distal end  8  of the shaft  4  prevents damage to tissues during insertion.  
         [0031]     An inflatable balloon  12  located at the distal end of the shaft  4  is formed from a flexible material that is essentially unstretchable. The balloon  12  is shown in  FIG. 1   a  in its inflated state. The inflated balloon  12  has a generally cylindrical shaped body portion  9  with a length of about  6  cm and an inflated diameter of about 1.2 cm. The cylindrical portion is coaxial with the shaft and has an annular cross-section. The balloon terminates in an ellipsoidal portion  11  having an axis of about 15 mm perpendicular to the axis of the shaft  4 .  
         [0032]      FIG. 1   b  shows the device  2  with the balloon  12  in its uninflated state. The balloon  12  has been collapsed and wrapped around the shaft  4 . The wall of the balloon  12  has a thickness of about 0.02-0.05 mm, so that the diameter  14  of the collapsed balloon on the shaft  11  does not exceed 3 mm.  
         [0033]     The balloon  12  is delivered to the passageway to be dilated with the uninflated balloon collapsed on the shaft  4 .  FIG. 2  shows the device  2  after delivery of the balloon  12  in its uninflated state to a cervix  16 . The distal end  8  and the ellipsoidal portion  11  are located in the uterus  24 . An electric pump  18  is used to deliver an incompressible fluid  20  in a reservoir  22  to the balloon  12 . The fluid flows from the pump  18  through the lumen  10  of the shaft  4  through openings  17  in the distal end of the shaft  4  into the balloon  12 . The pump  18  is may be programmable so as to deliver the fluid  20  at a rate that builds up pressure in the balloon  12  sufficiently slow so as to prevent excessive pain to the patient in the absence of anesthesia. Alternatively, the pump  18  may have a selectable flow rate by means of a flow rate selector  19 . The flow rate selector  19  may be located remote from the pump  18 , for example, by means of a cable  21 , or by a remote control (not shown). A remotely positionable flow rate selector  19  may be controlled by the patient so that the patient may select a flow rate that does not cause excessive pain. The pump  18  may be connected to a pressure gauge  3  that measures the fluid pressure inside the balloon  12  during inflation. In this case, the pump  18  may be programmed to deliver fluid to the balloon  12  so as to obtain a predetermined rate of increase in pressure. The pump  18  may further be programmable to discontinue delivery of the fluid  20  to the balloon when the volume of fluid  20  delivered to the balloon  12  is equal to the maximum capacity of the balloon  4 .  
         [0034]     As the balloon  12  is inflated, the ellipsoidal portion  11  of the balloon inflates before the cylindrical portion  9 , even though the thickness of the wall of the balloon is uniform throughout the cylindrical and ellipsoidal portions of the balloon  12 .  
         [0035]     This is because the ellipsoidal portion  11 , being located in the uterus  24 , is subjected to a lower external pressure than the cylindrical portion  11  in the cervix  16 .  
         [0036]      FIG. 3  shows the device  2  after partial inflation of the balloon  12 , showing the ellipsoidal portion  11  is almost completely inflated, and the cylindrical portion  9  only partially inflated. At this point, the balloon  12  is moved proximally in the direction of the arrow  23 , so as to lodge the ellipsoidal portion  11  in the internal os  25 . This ensures that the cylindrical portion is appropriately positioned in the cervix. Inflation of the balloon  12  continues until the balloon  12  has attained its maximum volume, at which time the cylindrical portion  9  is completely distended and has a diameter of at least 10 cm and preferably 12 cm. The pressure in the balloon when dilation of cervix  16  is complete may exceed 10 bar, 20 bar, 30 bar or 40 bar.  FIG. 4  shows the dilator  2  with the balloon  4  completely inflated and the ellipsoidal portion  11  of the balloon  4  lodged in the internal os  25 . The balloon  12  is now deflated and the device  2  is withdrawn from the body.  
         [0037]      FIG. 5  shows another embodiment of the device of the invention, generally indicated by  35 . The device  35  has features in common with the device  2 , and similar components are identified with the same numeral without further comment. The embodiment  35  has two balloons  36  and  37 , that are shown in their inflated state in  FIG. 5 . The balloon  36  has a cylindrical shape when inflated, and has dimensions similar to those of the cylindrical portion  9  of the balloon  12 . The balloon  37  is ellipsoidal in shape and has dimensions similar to those of the ellipsoidal portion  11  of the balloon  12 . The device  35  is used similarly to the device  2  as shown in FIGS.  2  to  4 . Both balloons  36  and  37  are in fluid communication with the shaft  11 . As explained above with reference to the ellipsoidal portion  11  of the balloon  12 , the ellipsoidal balloon  37  will inflate before the cylindrical balloon  36 . When the ellipsoidal balloon  37  is inflated, the shaft  4  is moved proximally until the ellipsoidal balloon  37  is lodged in the internal os. The shaft  4  is then moved distally a distance about equal to the spacing between the two balloons  36  and  37  along the shaft, so as to position the cylindrical balloon  36  in the cervix.  
         [0038]      FIG. 6  shows another embodiment of the device of the invention, generally indicated by  45 . The device  45  has features in common with the device  35 , and similar components are identified with the same numeral without further comment. In particular, the embodiment  45  has two balloons  36  and  37 , that are shown in their inflated state in  FIG. 6 . The balloon  36  has a cylindrical shape when inflated, and has dimensions similar to those of the cylindrical portion  9  of the balloon  12 . The balloon  37  is ellipsoidal in shape and has dimensions similar to those of the ellipsoidal portion  11  of the balloon  12 . In contrast to the device  35 , the device  45  has a shaft  46  containing a first lumen  47  and a second lumen  48 . The lumen  47  has a proximal end  49  and a distal end  50  located in the cylindrical balloon  36 . Fluid is delivered from the lumen  47  into the cylindrical balloon  36  through openings  17 a in the shaft  46 . The lumen  48  has a proximal end  53  and a distal end  51  located distal to the spherical balloon  36 . Fluid is delivered from the lumen  48  into the spherical balloon  37  through openings  17   b  in the shaft  46 . Each of the lumens  47  and  48  may be connected to a pump  18  and reservoir  20  (as shown in FIGS.  2  to  4 ) so that the balloons  36  and  37  may be inflated independently. The device  45  is used similarly to the device  2  as shown in FIGS.  2  to  4 . In particular, the ellipsoidal balloon  37  can be inflated before the cylindrical balloon  36 . This is done in order to position the cylindrical balloon  36  in the cervix as described above with reference to the embodiment of  FIG. 5 .  
         [0039]      FIG. 7  shows another embodiment of the device of the invention, generally indicated by  55 . The device  55  has features in common with the device  45  of  FIG. 6 , and similar components are identified with the same numeral without further comment. The embodiment  55  has two balloons  36  and  57 , that are shown in their inflated state in  FIG. 7   a,  and in their uninflated state in  FIG. 7   b.  The balloon  36  has a cylindrical shape when inflated, and has dimensions similar to those of the cylindrical portion  9  of the balloon  12 . The balloon  57  is ellipsoidal in shape when inflated and has inflated dimensions similar to those of the ellipsoidal portion  11  of the balloon  12 . The balloon  57  when uninflated is constricted around the shaft  46 , at an elastic constriction site  54  so as to form two separately inflatable compartments in the uninflated balloon  57 . As explained in detail below, pressurized fluid in the lumen  48  is released only into a distal compartment  56 . When fluid pressure in the distal compartment exceeds a predetermined value, the fluid forces passes from the distal compartment  56  into a proximal compartment  58 , as explained in detail below.  
         [0040]     FIGS.  8  to  10  show deployment of the device  55 . As shown in  FIG. 8 , the balloon  36  is delivered to the cervix  16  and the balloon  57  is delivered to the uterus  24 , with the balloons  36  and  57  in their uninflated state and collapsed on the shaft  46 . Fluid is now delivered through the lumen  48  of the shaft  46  and the opening  17   b  into the distal compartment  56  of the balloon  57 , until inflation of the distal compartment  56  is complete, as shown in  FIG. 9 . Due to the elastic constriction area  54 , the proximal compartment  58  of the balloon  57  does not inflate at this point. The inflated distal compartment  56  is then lodged in the internal os  25 , so as to ensure that the cylindrical balloon  36  is properly positioned in the cervix  16 . The proximal compartment  58  is now located in the distal termination of the cervix  16 . Now pressurized fluid is delivered to the cylindrical balloon via the lumen  48  of the shaft  46 .  FIG. 10  shows the device  55  after inflation of the cylindrical balloon  36  is complete. Now additional fluid is delivered to the distal compartment  56  of the ellipsoidal balloon. When the fluid pressure in the distal compartment  56  exceeds a predetermined threshold, the elastic constriction area  54  expands allowing fluid to flow into the proximal compartment  FIG. 11  shows the device with the balloon  57  completely inflated. As the proximal compartment expands  58 , it causes the distal terminal segment of the cervix  16  to expand. A spherical balloon can withstand a pressure that is twice that of a cylindrical balloon made of the same material and having the same wall thickness. Thus, the spherical balloon can deliver a pressure to the distal terminal portion of the cervix (where the resistance to dilation is greatest) that is about twice the pressure that can be delivered to the cervix by the cylindrical balloon