CA1299044C

CA1299044C - Apparatus for removing obstructions from organs and body cavities

Info

Publication number: CA1299044C
Application number: CA000539046A
Authority: CA
Inventors: Salam Zakko
Original assignee: University of California San Diego UCSD
Current assignee: University of California San Diego UCSD
Priority date: 1986-06-09
Filing date: 1987-06-08
Publication date: 1992-04-21
Anticipated expiration: 2009-04-21
Also published as: DE3750445D1; JPH07108296B2; EP0251512B1; AU7386287A; JPS6340541A; DK289787A; DE3750445T2; AU612576B2; DK289787D0; MX173735B; EP0251512A1; ATE110552T1

Abstract

APPARATUS FOR REMOVING OBSTRUCTIONS IN ORGANS
OR BODILY CAVITIES

ABSTRACT OF THE DISCLOSURE
A fully automatic organ pressure sensitive apparatus for dislodging and removing obstructions in bodily cavities or organs by both delivering and removing fluid thereto operable by continuous or intermittent perfusion of fluid over a set pressure range to effect dissolution and removal of the obstruction without complications to the patient. By continuous feedback monitoring of organ and body cavity pressure, the apparatus can constantly vary in fusion and aspiration rates to maintain the set pressure range. If the pressure is above or below the set range, it displays a safety feature causing the apparatus to shut down and sounding an alarm to alert the operator.

Description

~g~4 APPAR~T~S P~R R~NOVING OBSTR~CTIONS IN ORGANS
OR BODILY C~VITIES

BACKGROUND OF TEE INVENTION
5For most of the 500,000 plus individuals who suffer from gallstones, the treatment of choi~e i6 to have a cholecystectomy, or removal of the gallbladder. Recently, because of the cost and possible side effects associated with surgery, methods have been developed for chemically removing gallstones in situ. Generally, this procedure requires inserting a catheter into the gallbladder followed by infusing a chemical solvent capable of dissolving the gallstone. The procedure thus avoids the need and attendant risk of surgery.
1~ A variety of chemical solvents have been tried and found to exhibit varying efficiencies of gallstone dissolution, depending on the chemical nature of the gallstone. Gallstones are generally composed of cholesterol, or calcium salts, particularly calcium bilirubinate and calcium carbonate. Lipid solvents are effective at dissolving cholesterol gallstones, whereas these solvents have little or no solubilizing effect on gallstones composed of calcium salts. Thus, diethyl ether readily dis~olves cholesterol gallstones, and other soIvents such as mono-octanoin and octadiol (glyceryl-l-octyl ether) have good to outstanding solubilizing properties.
Unfortunately, few if any solvents are satisfactory for dissolving calcium gallstones.
In addition to the solvents described above suitable for dissolving cholesterol, recently it has been recognized tæAKKLpA.Fo6] UC CASE NO. 86-025-1 ~;~99044 that methyl tert butyl ether ~MTBE), a solvent hithertofore used primarily as a gasoline additive and a chro~atographic solvent media; was discovered to have outstanding cholesterol gallstone dissolving properties. Moreover, the solvent rapidly dissolves the gallstones without damaging the mucosa of the gallbladder. This finding has led to considerable activity focused on developing apparatus and methods for delivering MTBE to patients suffering from gallstones in ways to most effectively solubilize gal}stones without the complications arising from introducing a solvent into the body.
It is obvious that delivering a solvent to a patient requires the utmost ca~e to avoid releasing the solvent into the patient's bodily fluids or outside the area of treatment. Thus a key consideration in developinq devices used in the chemical therapy of gallstone dissolution i5 ensuring the controlled~delivery and removal of the solvent used to dissolve the gallstones. Considering that studies have shown that MTB~E is injurious if it passes into the intestine where it gets~absorbed which may also be an effect of other solvents used to solubilize lipids, there is a critical need for devices that ensure that such chemicals will not be released during chemical therapy for gallstone removal.
Also, because of the nPed to ensure containment of the effective solvent, in addition to the safety features described above, a suitable device should be ~user friendly," and not require the presence of highly skilled technicians to run the device. Further, for the same reasons, it should be easily maintainable.

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With a little reflection, it becomes apparen~t that there are considerable hurdles to surmount if one is to develop a device that has the features described above. For instance, it must be "intelligent" and capable of sensing instantaneous changes in gallbladder pressure brought about by infusing the solvent, and rapidly relay this information to controlling feedback circuits.
This is a crucial feature for such a device. If a gallstone should in some way prevent the necessary circulation of the solvent through the gallbladder, a critical pressure will build up, possibly rupturing the organ, or causing leakage of the solvent from the gallbladder through the cystic duct into the common duct and intestine. Thus the device must be "intelligent"
in the sense that it senses gallbladder pressure changes over a predefined range, and reacts fast enough to~keep the pressure in that range, shutting down when the pressure is outside the range.
Moreover, ideally, it would be desirable to~have a device that not only is capable of shutting down, but actually can flush out any debrls causing the bloclcage, and resume normal operation should the debris be removed.

SUMMARY OF THE INVENTION
In one aspect, the invention provides apparatus for removal of a soluble obstruction in a bodily organ or cavity, comprising:
source reservoir means for containing a fluid capable of dissolving said obstruction; first and second fluid conduits attached to and forming a fluid circuit with said reservoir means ~. ~

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-3a-and said organ or cavity and providing fluid communication between said reservoir means and said organ or cavity; pump means associated with each of said conduits to move said fluid in said conduits and around said circuit; means for detecting and measuring fluid pressure in said organ or cavity, said means adapted to classify said pressure as high, normal or low according to predetermined physiological criteria; and means operatively 10 connecting said means for detecting and measuring at each of said pump means and responsive to said organ or cavity fluid pressure to cause said pump means to maintain forward fluid flow at low and normal pressures and to decrease or reverse fluid flow at high pressure.
A further aspect of the invention provides apparatus for removal of gallstones from the gallbladder, comprising: a :
reservoir for containing fluid capable of dissolving gallstones;
first and second fluid conduits each having one end communicating with said reservoir and another end communicating with the gallbladder; pump means comprising -first and second pumps operatively associated respectively with said first and second conduits for moving said fluid in said first conduit in the infusion direction from said reservoir into the gallbladder, and for moving said fluid in said second conduit in the aspiration ; direction from the gallbladder to said reservoir; whereby, by simultaneous infusion and aspiration, continuous withdrawal of said fluid after exposure to said gallstones can be maintained at a substantial rate over prolonged periods; said apparatus ' ~ ~

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-3b-including a control system for selectively inhibiting infusion, said control system including means for continuously monitoring pressure within said gal1bladder, means for de-termining the relationship of said pressure with respect to a desired range based on predetermined physiological criteria, and means for selectively inhibiting infusion in response to said pressure being above said desired range.
The invention also provides, in a gallstone removal apparatus which includes a liquid transfer system Eor introducing liquid solvent to and removing said liquid solvent from the gallbladder of a living patient via a catheter in a manner to cause the gallstone to disintegrate and be removed with the liquid: the improvement wherein the liquid transfer system includes a control system comprising a controller and means for continuously determining and supplying to the controller the actual liquid pressure within the gallbladder during the treatment; said controller having means to receive from the attending operator a 20 pressure setting related to the predetermined pressure at which flow of the solvent out of the gallbladder into other parts of the body may occur and said controller being responsive to actual sensed gallbladder pressure to cause pump means to automatically reduce the quantity of solvent within said gallbladder upon the occurrence of actual gallbladder pressure in excess of high pressure value based upon said setting, thereby preventing release of said solvent into the body.
The apparatus which is described is effective for therapeutic ~ ~d .

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66128~243 -3c-treatment of obstructions in bodily organs by solvent circulation, particularly gallbladder or common bile duct stones. The apparatus consists of a forward or reverse acting solvent delivery means that is linked via pressure transducers to a feedback controller circuit. Continuous feedback of organ pressure to the controller circuit by the transducers is determinative of whether the apparatus acts in the forward or reverse mode.
Another aspect of the invention provides a method for removing a soluble obstruc~ion in an enclosed space, comprising:
inserting a catheter into said enclosed space, said catheter having at least two fluid conduits each communicating with source and receiver reservoir means for containing a fluid suitable for dissolving said obstruction, said catheter, reservoir means and conduits forming a fluid circuit; providing a pump in each of said conduits for moving said fluid through said conduits between said reservoir and said enclosed space; detecting and measuring fluid pressure in said enclosed space, said pressure being classified as high, normal or low according to predetermined criteria; causing said pumps by means responsive to said high, normal or low pressure to produce forward fluid flow in said circuit when said pressure is low or normal and to halt or reverse said fluid flow when said pressure is h1gh, said fluid thus at normal or low pressure contacting and dissolving said obstruction.

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The apparatus is preset to perfuse at a set pressure range. Over this range the solvent is constantly passed from a reservoir into the gallbladder, and from the gallbladder it is aspirated to a suitable rece~tacle. Delivery and removal of the solvent is at a rate sufficient to effect gallstone dissolution. Shsuld there be an increase in pressure, a feedback loop activates the device into the high pressure mode, thereby diverting the solvent away from the gallbladder. If after a predetermined period of time the pressure sensing transducer readings from the gallbladder indicate a return to normal operating pressure range, the device automatically reinitiates the normal infusion and aspiration (perfusion) mode. An additionaI feature of the invention is a self~purging mechanis~ ~After a preset interval, if the pressure does not decr~ease, the device enters a reverse mode to purge the aspiration port from the gallbladder when fluid is aspirated backward through the infusion port and i~fused through the aspiration port to purge it ~or discrete short intervals, during which tlme the pressure in the organ is continuously monitored. Should the blockage be removable by this ~self-purging~ acSion, the pressure transducers indicate normal operating pressure, and the device again resumes action in the normal pressure mode.
However, should the obstruction not be removable, then an alarm circuit is activated, so notifying the user. A
further feature of the invention is that it is able to distinguish pressure changes occurring within the gall~ladder from those arising as a result o~ cou~hing, laughing or like behavior. This feature prevents needless changes of operating modes.

12~1~V4~4 BRIEF DESCRIPTION OF ~ ~ DRA~INGS
Figure 1 shows an apparatus suitable for delivering solvent to a gallbladder and for removing the same containing dissolved or fragmented gallbladder stones.
Figure 2 shows a controller circuit that regulates the pump units shown in Figure 1, as well as other features of the apparatus.
Figures 3, 4 and 5 show features of a 3-lumen catheter.
DET~ILED DESCRIPTIO~ OF THE INVENTION
The invention described herein is suitably employed for delivering fluids to organs for removing obstructions contained therein. It will be appreciated at the outset that, while the subject invention described below details the invention regarding the removal of gallstones from the gallbladder, the invention can be used to remove a variety of obstructions from organs other than the gallbladder, and thus should not be construed as being narrowly limited to the treatment of gallstones. Indeed, it will become readily apparent that the device is easily adapted to removing obstructions from organs in general.
The invention deecribed herein is an organ pressure sensitive apparatus having a solvent delivery means in constant communication with a controller circuit via pressure transducers that monitor organ pressura. The apparatus functions over a preset pressure range delivering fluid to the gallbladder causing the fluid to contact and dissolve the gallstones, and withdrawing fluid from the gallbladder, thereby effecting the removal of dissolved or fragmented gallstones. The rate of solvent delivery and [ZAKKLPA.F06] UC CASE NO. 86-025-1 ~9~o~

removal can be adjusted to best effect dissolution of the obstruction to create the necessary turbulance to dissolve or fragment gallstones. If the pressure exceeds that of the normal operating range, the apparatus diverts solvent from the organ, thereby preventing leakage of the solvent from the site of treatment. Further, above the normal operating pressure range, the apparatus can be programmed to be "self-purging". This may be desirable in the instance when the obstruction is only partially dissolvable, causing blockage of the solvent removal, or aspiration means. At lower pressure, or pressure below the normal operating pressure range, the rate of aspiration is decreased while infusion continues, thereby reestablishing normal operating pressure.
Figure 1 shows an exemplary apparatus for removing gallstones. A reservoir 10 contains a solvent that is a chemical suitable for dissolving gallstones. Should the gallstone be composed of cholesterol, a variety of solvents would be efficacious. Particularly effective is methyl tert butyl ether (MTBE). The latter, as described su~ra has been shown to readily dissolve cholesterol stones rapidly both in vitro and in vivo. At normal operating pressures, the solvent moves via a con~uit 12 from the reservoir by aid of a pumping apparatus 14. The fluid then moves through a valve 16 and from the valve through a catheter into the gallbladder. During this operation valve 26 is closed to prevent solvent return to reservoir. The solvent is delivered at a predetermined effective rate for gallstone dissolution thereby providing solvent turbulance and contact with the gallstones for a period of time sufficient to dissolve and fragment the stones.

[ZAKKLPA.F06] UC CASE N0. 86-025-1 : ` ~

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Simultaneous with the delivery of MTBE to the gallbladder, a second pump device 18 aspirates the fluid from the gallbladder now containing dissolved gallstones and debris. This material passes out of the gallbladder via an aspiration port in tbe catheter 20. The fluid moves from the catheter, passing through a valve 23, and from there it is deposited in a reservoir. Either the reservoir lO used to deliver the solvent, or a separate reservoir is suitable for this purpose. Figure l shows the same reservoir lO
being utilized to both deliver fluid to the gallbladder as well as receive aspirated fluid therefrom. It i~ worth noting that if the same reservoir is used, gallbladder stone fragments, mucous and~the like Eemoved from the gallbladder are heavier than the solvent, MTBE, and therefore settle to the bottom of the reservoir and do not hinder continued withdrawal of fluid from the reservoir to effect further stone dissolution.
The pum~s 14 and 18 are controlled by a controller circuit 22. `The controller circuit 22 in turn receives pressure readings from the transducer 24 causing the controller circuit 22 to open or close flow valves 16, 23 and 26 in a certain fashion to inhi~it infusion or aspiration as necessary to control organ pressure depending on whether the transducer 24 indicates that the pressure in the gallbladder is within, above, or below the normal operating pressure range. The transducer in turn is connected to the catheter through port 28 which is in communication with the ga}lbladder.
At the preset normal operating pressure, the pump 14 delivers fluid from the reservoir lO to the tube 12 through gO4~

the valve 16 and to the gallbladder. Simultaneously, and at a slightly slower rate, the pump 18 aspirates the fluid from the gallbladder through the catheter aspira;tion port 20.
Fluid passes through the valve 23 and thence to a reservoir~
The controller is further programmed to respond to pressures that exceed or are below that of the normal operating pressure range. Above the normal operating pressure range (high pres~ure mode), the controller unit 22 shuts down valve 16 and simultaneously opens valve 26~ ~his provides a path for diverting the incoming fluid away from the gallbladder. At that time valve 23 is open to effect continual gallbladder emptyinq to return the pressure to the normal operating range. If the pressure in the gallbladder does not return to the normal operating pressure setting within a preset time, for example, 7 seconds, then the controller can be ~programmed to instruct the pumps to reverse the direction of fluid movemen~, and simultaneousl~
valves 23 and 26 are ~losed. Valve 16 is opened to provide a path for fluid to be reverse aspirated from the gallbladder in this self-purging~ mode. This mode essentially causes a small amount of fluid to be pumped in through the aspiration port of the catheter 20 to clear it from obstructions while aspiration is effected by pump 14 through valve 16. This mode of operation continues for a brief period of time, and then the controller unit 22 instructs the machine to resume normal operation should the obstruction be removed and the pressure transducer 24 indicate reestablishment of normal operating pressure range.
If the transducer continues to indicate pressures present in the gallbladder, above the normal operating pressure, the ~299V~

controller unit 22 again instructs the pumping apparatus to purge the system. If, after several "self purging" cycles, the obstruction is still not removed, the controller unit 22 then shuts down the pumping system and activates an alarm circuit 34 notifying the user of a potentially dangerous condition.
Referring now to Figure 1 and Figure 2, a representative controller unit will be described. The controller circuit 22 instructs the pumps 14 and 18 to deliver or aspirate fluid from the gallbladder. Thus, a circuit will typically have a pressure transducer 30, and an example of a suitable transducer is a Statham gold pressure transducer P23ID. The pressure transducer 30 relays information to an amplication device 32 which amplifies the signal, and transmits it to a high and low pressure alarm circuit 34, and either directly or through the averaging circuit 36, to a pressure-sensing circuit 38 that reads preset low and high pressure values, and which is connected to the valves 16, 23, and 26. The latter valves are typically solenoid flow valves. The averaging circuit 36 can be switched in if desired to discriminate between pressure changes in the gallbladder arising from fluid buildup due to obstructions, or from hyperventilating, laughing or like activities. Thus the averaging circuit essentially screens out artificially high or low pressure peaks.
The pressure sensing circuit 38 is connected to a cascade timer 40, which in turn is connected to a pump reverse relay circuit 42. Thus, when gallbladder pressure exceeds that of the normal operating pressure range, and the ~ZAKKLPA.F06] UC CASE NO. 86-025-1 o~

obstruction is not removed within a few seconds, then the cascade timer 40 activates the pump reverse relay 42. The latter circuit is responsible for "self-purging" the system.
Should high pressure persist after several brief "self purging" cycles, then the alarm circuit 34 is activated, stopping the pumping system b~v shutting off its power supply and sounding an alarm notifying the user. Note that at any time during the pump reverse relay cycle, should the pressure return to within the normal pressure range, the apparatus resumes normal operation.
It will be further noted as shown in Figure 2 that a pump power relay circuit 4~ and a pump speed control circuit 46 are also interactive with the whole system. The pump speed control circuit 46 derives power through the pump power relay 44, which in turn is controlled by the alarm circuit 34. The pump motor 47 derives its power supply from the pump power relay 44. Any time an alarm condition exists, this relay shuts off power to the pump, stopping it from pumping. The pump speed control circuit 46 has a manual adjustment capability through which the operator can set the desired perfusion rate for that specific situation.
An analogue pressure readout 48 is provided for the operator to assess effective operation and to refer to during calibration.
Several features of an apparatus as described above that enhance its performance will be described. The pumping device preferred in the subject invention is a peristaltic pump. This type of pump offers several advantages such as replacable wettable surfaces, which are particularly advantageous in those instances where the solvent being used [ZAKKLPA.F06] UC CASE NO. 86-025-1 . ~

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to dissolve the obstruction is at all corrosive~ ~oreover, peristaltic pumps are resistant to clogging, in contrast to standard syringe type pumps. However, it should be noted that syringe pumps are similarly employable in the subject invention in those instances where the fluid used to dissolve and remove the obstruction is a solvent provided the syringe pumps are constructed of suitable material, particularly but not exclusively, glass. Syringe pumps made of plastic are not preferred in instances~where the solvents used are incompatible with the plastic composition of the syringe. An additional disadvantage associated with the use of syringe pumps that is not present in peristaltic pumps is that in those instance where a solvent is being utilized, evaporation of the solvent can cause deposits in the body of the syringe, causing it to ~freeze,~ and thus interrupt delivery of the fluid to the organ being treated. Lastly, peristaltic pumps are~ capable of mucb ~reater fluid circulation rates than a syringe pump. This is advantageous in certain instances where the obstruction to be removed, such as a gallstone, re~uires turbulent flow rates across the surface of the gallstone to accelerate the dissolution process.
A predetermined normal operating pressu~e range is programmed into the controller circuit 22. Should the pressure in the gallbladder exceed normal operating pressure, the action of the controller circuit 22 prevents leakage of solvent from the gallbladder through the cystic duct into the co~mon duct, as well as into the intestine or around the entry site of the cathetec. Also, because the controller circuit 'sees" true gallbladder pressure, it ~;~9gO~

readily adjusts to decrease as well as increase pressure by adjusting the net delivery rate of the solvent to the gallbladder. For example, should the pressure fall below the normal operating pressure range, the controller circuit 22 ceases or slows down the rate of aspiration of solvent, and simultaneously continues infusing solvent to reestablish normal operating pressure.
The pressure sensitive alarm circuit 34 is constantly monitoring system operation and gallbladder pressure. If gallbladder pressure cannot be brought to normal operating pressure range by the action of the controller circuit 22 in a specified period of time, it will shut down the pumping system and sound an alarm drawing the attention of the operator. The operator, after correcting the problem, can resume normal operation by activating the reset button 49.
The apparatus is completely automatic, and is operable without any significant operator input. Moreover, it i6 readily converted to a completely closed circuit system in those instances where the therapeutic fluid is combustible.
Z0 This feature is required for particularly combustible solvents.
A variety of tubing is suitably used with the pumps o~
the subject apparatus. However, we have found that tubing composed of TygonTM special formulation F-4040A is particularly compatible with solvents such as methyl tert butyl ether. Moreover tubing with a large internal diameter is favored for use with peristaltic pumps, enabling a high volume per revolution ratio to be obtained, thereby permitting a low revolution per minute rate to be utilized, [ZAKKLPA.F06] UC CASE N0. 86-02S-l ... ..

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-hence minimizing torque buildup when a switchover to the high pressure mode leads to pump motor reverse.
As discussed above, the subject apparatus can be utilized for removing obstructions in a variety of organs.
However, in the instance where it is used to remove gallstones from gallbladders, perfusion rates of about 50 ml/min - 300 ml/min may be effective. This is readily accomplished by manually adjusting the pump speed control circuit 46.
A variety of catheters usable to deliver and aspirate the fluid can be suitably employed. ~owever, a three lumen catheter as shown in Figures 3 and 4 is favoced since pressure measurements, as well as perfusion and aspiration of the fluid can all be carried out simultaneously. A
lS suitable 3-lumen catheter should have an outside dia~eter not larger than can be readily employed for the surgical insertion of the catheter into the gallbladder, and should have an aspiration port S0, a pressure sensing port 52, and an infusion port 54. To effectively remove dissolved gallstQne debris and the like, it is preferred that the aspiration port be larger in diameter than eitber cf the two other ports. Figures 4 and 5 further show another feature of the catheter. It has an elongated tapered tip 56, holes in the tip 58 and 60 that provide a means for fluid communication with the pressure sensing port, and the infusion port, respectively. In addition there are openings 62 in the wall of the catheter that provide a means for fluid communication of fluid in the gallbladder with the aspiration port. Note that thè number of openings is not invariant, and depending on ~he number of gallstones present - -. ` c i~99~344 in the gallbladder, as well as the desirable therapeutic need to effect rapid treatment, that more or fewer holes can be anticipated.
The system should not be construed as being limited to a 3-lumen catheter. A variety of catheters of different lumens will perform satisfactorily provided that the system is modified to accommodate such catheters, such modifications being well known to those skilled in the art.
It will be appreciated by those skilled in the art that there are numerous modifications in both the electrical circuitry, as well as the overall interconnecting features of the invention that will achieve the efficacious removal of obstructions in particular organs. For instance, while the automatic ~self purging" feature of the apparatus is desirable, a devioe without this feature will perform adequa~ely. Moreover, it should be further noted that, wbile the invention has been described as applicable to the removal of gallstones from gallbladders, its use should not be so narrowly construed. Thus, it is the intent herein to present an invention that is generally applicable for the removal of obstructions from a variety of organs by dissolving and dislodging the obstruction using solventsO
We claim:

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Claims

1. Apparatus for removal of a soluble obstruction in a bodily organ or cavity, comprising:
source reservoir means for containing a fluid capable of dissolving said obstruction;
first and second fluid conduits attached to and forming a fluid circuit with said reservoir means and said organ or cavity and providing fluid communication between said reservoir means and said organ or cavity;
pump means associated with each of said conduits to move said fluid in said conduits and around said circuit;
means for detecting and measuring fluid pressure in said organ or cavity, said means adapted to classify said pressure as high, normal or low according to predetermined physiological criteria; and means operatively connecting said means for detecting and measuring at each of said pump means and responsive to said organ or cavity fluid pressure to cause said pump means to maintain forward fluid flow at low and normal pressures and to decrease or reverse fluid flow at high pressure.

2. Apparatus as in Claim 1 wherein said responsive means comprises:
controller means to operate said pumps;
a first valve situated in said first fluid conduit and opened or closed by said controller means, said first valve being open at low or normal pressures and normally closed at high pressures;

[ZAKKLPA.F06] UC CASE NO. 86-025-1 a second valve situated in said second fluid conduit and opened or closed by said controller means, said second valve being open at low or normal pressures and closed shortly after detection of high pressure;
a bypass conduit connected to said first conduit for diverting fluid around said pump in said first conduit; and a third valve situated in said bypass conduit and opened or closed by said controller means, said third valve being closed at low or normal pressures and normally open at high pressures.

3. Apparatus as in Claim 2 wherein said detecting and measuring means comprises a pressure transducer.

4. Apparatus as in Claim 3 wherein said responsive means includes a pressure sensing averaging circuit in communication with said pressure transducer.

5. Apparatus as in Claim 2 wherein said controller means also causes said valves to cycle between open and closed portions several times while high pressure persists and then to halt operation of all pumps and activate an alarm if said high pressure has not been reduced to normal pressure during said cycling.

6. Apparatus as in Claim l wherein said responsive means comprises:
motor and motor drive means for each of said pumps, and controller means operatively connected to said pumps and responsive to signals from said pressure transducer to [ZAKKLPA.F06] UC CASE NO. 86-025-1 operate each pump through said motor and motor drive means independently as determined by whether said pressure is high, normal or low, said controller means causing said pumps to produce forward flow at low and normal pressure and to halt or reverse flow in at least the pump in the first of said fluid conduits at high pressure.

7. Apparatus as in Claim 6 wherein said controller means also causes said pumps to cycle between forward and reverse flow if high pressure persists and to switch said pump to aspiration and activate an alarm if after several such cycles such high pressure has not been reduced to normal pressure during said cycles.

8. Apparatus as in Claim 6 wherein said detecting and measuring means comprises a pressure transducer.

9. Apparatus as in Claim 8 wherein said responsive means includes a pressure sensing averaging circuit in communication with said pressure transducer.

10. Apparatus as in Claim 1 wherein the terminal portion of each of said first and second fluid conduits distal to said source reservoir means are combined into a catheter.

[ZAKKLPA.F06] UC CASE NO. 86-025-1

11. Apparatus as in Claim 10 where said catheter is a three-lumen catheter comprising a first lumen for passing fluid from a source reservoir to said organ or cavity, a second lumen for passing said fluid from said organ or cavity to a receiver reservoir and a third lumen for communicating said pressure to said measuring means.

12. A method for removing a soluble obstruction in an enclosed space, comprising:
inserting a catheter into said enclosed space, said catheter having at least two fluid conduits each communicating with source and receiver reservoir means for containing a fluid suitable for dissolving said obstruction, said catheter, reservoir means and conduits forming a fluid circuit;
providing a pump in each of said conduits for moving said fluid through said conduits between said reservoir and said enclosed space;
detecting and measuring fluid pressure in said enclosed space, said pressure being classified as high, normal or low according to predetermined criteria;
causing said pumps by means responsive to said high, normal or low pressure to produce forward fluid flow in said circuit when said pressure is low or normal and to halt or reverse said fluid flow when said pressure is high, said fluid thus at normal or low pressure contacting and dissolving said obstruction.

13. A method as in Claim 12 wherein said fluid is in turbulent flow while in contact with said obstruction.

14. A method as in Claim 12 further comprising cycling said fluid flow between forward and reversed flow several times while said high pressure persists.

15. A method as in Claim 14 further comprising halting said fluid flow and activating an alarm if said high pressure has not been reduced to normal pressure during said several cycles.

16. Apparatus as in Claim 6 wherein said controller means responds to said transducer through an averaging circuit.

17. Apparatus for removal of gallstones from the gallbladder, comprising:
a reservoir for containing fluid capable of dissolving gallstones;
first and second fluid conduits each having one end communicating with said reservoir and another end communicating with the gallbladder;
pump means comprising first and second pumps operatively associated respectively with said first and second conduits for moving said fluid in said first conduit in the infusion direction from said reservoir into the gallbladder, and for moving said fluid in said second conduit in the aspiration direction from the gallbladder to said reservoir;
whereby, by simultaneous infusion and aspiration, continuous withdrawal of said fluid after exposure to said gallstones can be maintained at a substantial rate over prolonged periods;

said apparatus including a control system for selectively inhibiting infusion, said control system including means for continuously monitoring pressure within said gallbladder, means for determining the relationship of said pressure with respect to a desired range based on predetermined physiological criteria, and means for selectively inhibiting infusion in response to said pressure being above said desired range.

18. The apparatus of claim 17 wherein said control system includes means for inhibiting aspiration in response to said pressure being below said desired range.

19. In a gallstone removal apparatus which includes a liquid transfer system for introducing liquid solvent to and removing said liquid solvent from the gallbladder of a living patient via a catheter in a manner to cause the gallstone to disintegrate and be removed with the liquid:
the improvement wherein the liquid transfer system includes a control system comprising a controller and means for continuously determining and supplying to the controller the actual liquid pressure within the gallbladder during the treatment;
said controller having means to receive from the attending operator a pressure setting related to the predetermined pressure at which flow of the solvent out of the gallbladder into other parts of the body may occur and said controller being responsive to actual sensed gallbladder pressure to cause pump means to automatically reduce the quantity of solvent within said gallbladder upon the occurrence of actual gallbladder pressure in excess of a high pressure value based upon said setting, thereby preventing release of said solvent into the body.

20. The apparatus of claim 19 wherein said pump means comprises an infusion pump and an aspiration pump, said pumps capable of operating simultaneously to infuse and aspirate said solvent relative to said gallbladder through respective lumens of said catheter whereby continuous flow of said solvent into and out of said gallbladder can be maintained by said controller during normal operation, said controller adapted to stop infusion and continue aspiration when actual gallbladder pressure exceeds said high pressure value.

21. The apparatus of claim 20 wherein said controller is capable of operating said pump means to simultaneously infuse and aspirate over a set pressure range and in response to actual gallbladder pressure below said range, said controller adapted to automatically stop aspiration while maintaining infusion flow.

22. The apparatus of claim 17, 19 or 20 wherein the pump means is adapted to transfer the solvent into the gallbladder at rates in the range between about 50 ml/min to 300 ml/min.

23. The apparatus of claim 17, 19 or 20 programmed to respond to occurrence of a selected irregular pressure condition in said gallbladder by automatically momentarily reversing flow to clear a possible obstruction to normal flow.

24. The apparatus of claim 17, 19 or 20 wherein said control system includes averaging means that functions to prevent response to a transient high pressure signal such as coughing or laughing,

25. The apparatus of claim 17, 19 or 20 wherein said pump means is of the peristaltic type.

26. The apparatus of claim 17, 19 or 20 in combination with a multilumen catheter constructed to infuse and aspirate solvent with respect to said gallbladder, an independent lumen of said catheter adapted to transmit an actual pressure signal from said gallbladder to said control system.

27. The apparatus of claim 26 wherein said catheter is of curved configuration and the opening for said pressure transmitting lumen is on the inside surface of said curved configuration.

28. The apparatus of claim 17, 19 or 20 in which said pump means is provided with a controllable motor and said control system controls said flow by controlling the direction and speed of the motor.