System and method for detecting perforations in a body cavity

A system and method for detecting perforations in a body cavity. In accordance with the method of the invention, a fluid (liquid or gas) is delivered into a body cavity to slightly pressurize the cavity. A pressure sensing system monitors the pressure within the cavity for a predetermined test period. If cavity pressure is not substantially sustained during the test period, the physician is alerted to further assess the cavity for perforations before initiating treatment within the cavity. In a preferred form of the system, a medical treatment system such as an RF ablation system is provided with perforation detection functionality. The system preferably includes a pre-test and post-test lockout system. The lockout system prevents RF power delivery unless, during a predetermined test period, the pressure sensing system determines that no perforation exists, or unless a previously performed perforation detection procedure determined a perforation was present but the lockout system was subsequently overridden by the physician.

FIELD OF THE INVENTION

The present invention relates to the field of systems and methods for detecting the presence of perforations in body cavities. More particularly, the present invention relates to a system and method that pressurizes a body cavity and detects whether the body cavity can maintain a pressurized condition

BACKGROUND OF THE INVENTION

There are certain medical procedures that are carried out within a body cavity. One example of such a procedure is tissue ablation. Ablation of the interior lining of a body organ is a procedure which involves heating the organ lining to temperatures which destroy the cells of the lining or coagulate tissue proteins. Such a procedure may be performed as a treatment to one of many conditions, such as chronic bleeding of the endometrial layer of the uterus or abnormalities of the mucosal layer of the gallbladder. Existing methods for effecting ablation include circulation of heated fluid inside the organ (either directly or inside a balloon), laser treatment of the organ lining, and resistive heating using application of RF energy to the tissue to be ablated.

Ablation procedures are often carried out without direct endoscopic visualization. For example, ablation of the endometrium typically involves insertion of an elongate ablation device into the patient's cervix without the use of a hysteroscope. As can be appreciated, the presence of a perforation in the uterus could result in inadvertent passage of the ablation device through the perforation and out of the uterus into the bowel. Although events of this nature are rare, the injury that could result from such occurrences make it highly desirable to provide a mechanism by which a physician can evaluate whether perforations are present in a body cavity before a treatment device such as an ablation device is used to deliver power.

SUMMARY OF THE INVENTION

The present invention is a system and method for detecting perforations in a body cavity. In accordance with the method of the invention, a fluid (either liquid or gas) is delivered into a body cavity to slightly pressurize the cavity. A pressure sensing system monitors the pressure within the cavity for a predetermined test period. If cavity pressure is not substantially sustained during the test period, the physician is alerted to further assess the cavity for perforations before initiating treatment within the cavity. In a preferred form of the system, a medical treatment system such as an RF ablation system is provided with perforation detection functionality. The system preferably includes a pre-test lockout feature that prevents RF power delivery unless a perforation detection procedure has been performed.

DETAILED DESCRIPTION

A perforation detection system10(also referred to as a “body cavity assessment system”) utilizing principles of the present invention will be described herein as forming part of an RF ablation system used to ablate tissue within a body cavity such as a uterus. However, it. should be appreciated that the perforation detection system10may be provided with another type of system used for treatment, or it may be provided independently of a larger treatment system.

Generally speaking, perforation detection system10includes a medical ablation device12of a type used for tissue ablation, and an RF generator system14of the type used to deliver RF ablation energy to an electrode array on ablation device12. The RF generator unit, however, is provided with additional components that are used for the body cavity assessment function of the present invention. In particular, the RF generator unit is provided with a fluid/gas source16and a body cavity assessment system20. Fluid/gas source16is fluidly coupled to ablation device12via a source line22. The ablation device is positionable within a body cavity BC so as to deliver fluid/gas from source16through the source line22and the ablation device and into the body cavity.

Body cavity assessment system20includes a pressure sensing system24fluidly coupled to the medical device via pressure detection/signal line26. Pressure sensing system24monitors the pressure within the body cavity BC while fluid/gas is being (or after it has been) delivered to the body cavity, and detects whether elevated pressure can be maintained above a predetermined threshold level over a predetermined period of time. If it cannot, the user is alerted that there may be a perforation in the organ.

Body cavity assessment system20further includes a lockout system28that prevents treatment with the ablation device12unless body cavity assessment has been performed (pre-test lockout) and that prevents treatment if the body cavity assessment indicates a possible perforation (post-test lockout). The RF generator system14is additionally provided with a vacuum system30coupled to pressure detection/signal line26, RF circuitry27, and other components needed to perform the ablation function, A footswitch32or other input device controls operation of the RF generator system14. A microprocessor or programmable logic device34within the RF generator system14governs various functions, including the body cavity assessment, lockout, and RF ablation procedures.

Ablation Device

An example of an RF ablation device12that may be used with the system10is shown inFIG. 2A and 2B. Ablation devices of this type are shown and described in U.S. Pat. No. 5,769,880 and U.S. application Ser. No. 09/103,072, each of which are incorporated herein by reference. A similar device is the Novasure® ablation device available from Novacept, Inc., Palo Alto, Calif. Naturally the perforation detection system may be provided in combination with the other medical devices as well. Such alternative devices include thermal ablation devices in which heated liquid is circulated through a balloon positioned within the body cavity of interest, or other device used for procedures besides ablation. Alternatively, the system may be provided with two medical devices, one for use in delivering inflation medium and another for use in treating body tissue. As a further alternative, a treatment device may be provided independent of the system10.

Ablation device12is configured to deliver RF ablation energy to the interior surface of a body cavity, while causing moisture (e.g. steam) generated during ablation to be withdrawn away from the body tissue preferably using suction. This moisture transport feature of the device12is advantageous in that removing steam from the ablation site minimizes the amount of thermal ablation that would otherwise be caused by the steam. Greater control over ablation depth is thus achieved by allowing ablation to occur only (or primarily) by RF energy rather than by thermal conduction.

The device12includes an RF applicator head36, a sheath38, and a handle40. The applicator head36is slidably disposed within the sheath38to give the appicator head36a streamlined profile (FIG. 2A) to facilitate insertion of the device into a body cavity (e.g. the uterine cavity). Once the applicator head36has been inserted into the body cavity, handle40is manipulated to cause the applicator head36to extend from the distal end of the sheath38and to expand into the position shown inFIG. 2Bas to make contact with body tissue.

Referring toFIG. 2B, applicator head36extends from the distal end of a length of tubing42which is slidably disposed within the sheath3B. Applicator head36includes an external electrode array44and an internal deflecting mechanism46used to expand and tension the array for positioning into contact with the tissue.

The array44is preferably formed of a stretchable metallized fabric mesh which is preferably knitted from a nylon and spandex knit plated with gold or other conductive material. In one array design, the knit is formed of three monofilaments of nylon knitted together with single yarns of spandex. Each yarn of spandex has a double helix of five nylon monofilaments coiled around it.

When in its expanded state, the array44includes a pair of broad faces48(one of which is shown inFIG. 2B) spaced apart from one another, and narrower side faces (not shown) extending between the broad faces48along the sides and distal end of the applicator head36, and a distal face52extends between the broad faces48at the distal end of the applicator head36.

Insulating regions (not shown) formed by etching or other techniques on the applicator head divide the mesh into electrode regions.

The array may be divided by the insulated regions into a variety of electrode configurations. In a preferred configuration the insulating regions divide the applicator head into four electrodes by creating two electrodes on each of the broad faces.

Deflecting mechanism46and its deployment structure is enclosed within electrode array44. External hypotube58extends from tubing42and an internal hypotube60is slidably and co-axially disposed within hypotube58. Flexures62extend from the tubing42on opposite sides of external hypotube58. Hypotube60is a dual lumen tube that is coupled to the pneumatic subsystem as will be described below.

A plurality of longitudinally spaced apertures (not shown) are ford in each flexure62. During use, these apertures allow moisture to pass through the flexures and to be drawn into the exposed distal end of hypotube58using a vacuum source located in the RF generator system14and fluidly coupled to hypotube58.

Each flexure62preferably includes conductive regions that are electrically coupled to the array44for delivery of RF energy to the body tissue. For example, strips of copper tape (not shown) or other conductive material may extend along opposite surfaces of each flexure. Conductor leads (not shown) are electrically coupled to the strips and extend through tubing42to an electrical cable which is attachable to the RF generator.

During use of the ablation device, the applicator head36is inserted into the uterus with the sheath38covering the array44to compress the applicator head36into a streamlined condition. Once the applicator head is within the uterus, the handle is used to withdraw the sheath and to open the array into its deployed position. Vacuum source30(FIG. 1) is activated, causing application of suction to hypotube60. Suction helps to draw uterine tissue into contact with the array44.

Ablation power is supplied to the electrode array44by the RF generator system14. The tissue is heated as the RF energy passes from electrodes56to the tissue, causing moisture to be released from the tissue. The vacuum source helps to draw moisture from the uterine cavity into the hypotube60. Moisture withdrawal is facilitated by the apertures formed in flexures, by preventing moisture from being trapped between the flexures and the lateral walls of the uterus.

Pneumatic Subsystem

The fluid/gas source16, pressure sensing system24, and associated components are shown in FIG.3. Each of the components of the pressure sensing system24is preferably coupled to microprocessor34of the RF generator system14although for clarity the microprocessor is not shown in FIG.3. All pressure transducers, solenoid valves, and the vacuum pump are controlled by the microprocessor. As discussed, a programmable logic device may be used in place of the microprocessor, although the term “microprocessor” will be used here for simplicity.

It is also important to note that in the embodiment described below the two lines (source One22and pressure detection/signal line26) play different roles during RF ablation than for perforation detection. Specifically, the signal line26for perforation detection serves as a suction line for ablation. The source line22for perforation serves as a vacuum signal line for ablation.

Components along the source line22will first be described. Fluid/gas source16is preferably a disposable CO2cylinder, and may be a 16 gm cylinder providing approximately 850 psi at 25 C. One such example is the Linde medical grade 16 gm cylinder. The cylinder is removably attached to a pressure regulator68such as the Leland Model 50033 or equivalent. Regulator68includes a main shutoff valve70and pressure regulation component72which has a control pressure of approximately 60 psi. A pressure gauge74such as SenSym model ASCX100DN or equivalent is fluidly coupled to source line22. Pressure gauge74monitors the pressure remaining in the fluid/gas source16so as to detect when a low volume of fluid/gas remains, or when the user has failed to open the valve70.

A solenoid valve76is positioned along the source line22, downstream of the pressure regulator68. Valve76remains in a dosed condition, preventing flow of gas through the line22, except when a cavity assessment procedure is being carried out. A second pressure regulator78, such as an Airtrol R-920 series regulator, is positioned downstream of the valve76so as to reduce pressure in line22down to approximately 90+/−10 mmHg during a cavity assessment procedure. A flow control orifice80, positioned downstream of regulator78, limits flow in line14to 100+/−10 scc/min (standard cc/min). A pressure sensor82downstream of orifice80monitors whether the pressure limit (of, for example, approximately 100 mm Hg) has been exceeded. If the limit has been exceeded, an output signal from this sensor causes an audible alarm to be triggered and the solenoid valve76is turned off. Downstream of orifice80, source line22is coupled, using a flexible Tygon® tubing for example, to the introducer sheath38(FIG. 2B) of the ablation device12. The introducer sheath is located at the internal surface of the body cavity BC (the internal os, for example, in the case of a uterine cavity) so as to deliver gas into the body cavity BC that is to be treated.

Turning to the components along the pressure detection line26, the pressure signal line26is fluidly coupled, using a Tygon® tubin for example, to the lumen of hypotube60. Downstream of the medical device12is a pressure sensor84, such as the Sensym ACSX05DN. During a cavity assessment procedure, sensor84monitors pressure in the pressure signal line26and delivers the signal to microprocessor34. Microprocessor34(or other electronic means such as the programmable logic device mentioned previously) then determines if pressure in the body cavity BC has failed to achieve a predetermined threshold (indicating a perforation in the body cavity) or if it has and maintained the threshold for a predetermined time period (indicating that the body cavity has no perforation). In this capacity, the microprocessor or (programmable logic device) serves as a feedback means that activates a notification signal to alert a user if the pressure monitored by the pressure sensor fails to rise and remain above a predetermined level during a predetermined amount of time. The microcroprocessor may initiate various forms of notification signals, such as visual or auditory signals.

Further downstream of the pressure sensor84is a vacuum pump86. While not needed for perforation detection, vacuum pump86is used to carry out the moisture transport function of the medical device12described in the section entitled Ablation Device above.

A second solenoid valve88lies upstream of the vacuum pump86. Valve88remains open at all times except during cavity assessment. Because the exhaust line of the vacuum pump may not be air-tight when it is not operating (including during the cavity assessment procedure) the valve88is provided to close the pressure signal line against leaks through the vacuum pump.

A simplified state diagram illustrating operation of the system is shown in FIG.4. Operation begins with valve76in the closed condition, and with valve88in the opened condition. In preparation for use of the system, a CO2 cylinder16is connected to the appropriate receiving device on the RF Generator's pneumatic subsystem (FIG.3). The power to the generator is switched on. Pressure gauge74detects the pressure in the portion of pressure/monitoring line22extending between CO2cylinder16and valve76. If the user has failed to open the main CO2shutoff valve70, or if the pressure detected by gauge74is less than the specified pressure, an audible alert will sound, indicating a low-gas condition. Assuming no low-gas condition is detected, the user will connect the ablation device12to the RF generator system14.

The system remains in a “WAIT FOR CONNECT” condition, step102, until the user connects the ablation device12to the RF generator system. When the ablation device is plugged in, it actuates a microswitch or similar feature, which alerts the microprocessor that the ablation device has been connected. Connection of the device automatically starts the “CO2PURGE” cycle, step104. During the purge cycle, valve76is opened to permit the flow of CO2through the device to drive air from the device. The purge cycle lasts for a duration sufficient to purge the air from the system, approximately 10 seconds. During the purging cycle the user is alerted by audible and visual indicators not to insert the device into the body cavity in order to prevent air from being delivered into the body. As a safety precaution, the vacuum pump that is,part of the RF Controller is pulsed every few seconds during purging. If the user has inserted the ablation device into a body cavity during purging, the vacuum pump will draw out air that is delivered to the body.

During the purge cycle and device insertion into the body cavity, the ablation device is dosed, such that the poles of the electrode array are in contact with each other. A low voltage signal is applied to the ablation device which senses that the poles are in contact by detecting a DC short. After the completion of the purging cycle the system waits for the device to be deployed within the patient, step106, by monitoring for the end of the DC short condition. Once the user inserts the device into the uterine cavity and opens the array, the system detects that a DC short condition is no longer present. As a safety precaution, the perforation detection cycle cannot be initiated until the DC short condition is eliminated. In this way the last operation to be performed before the application of RF energy is the perforation detection cycle.

From the completion of the purge cycle to the initiation of the perforation detection test, a continuous, low level flow of CO2 is circulated through the ablation device to keep the source and pressure signal lines open and free from blockage.

Next, the system waits for the user to depress the footswitch32, “WAIT FOR FOOTSWITCH”, step108. Once the footswitch has been depressed, a 30-second timer is initialized (“RESET TIMER”) and the perforation detection test, (“PERFORM PRESSURE TEST”) 110 begins. Valve88is energized to close off the vacuum pump86to avoid loss of pressure through it. If it was not already opened, valve76is opened, allowing CO2to flow into the body cavity via medical device12. When the pressure at gauge84rises and remains above 50 mmHg for 4 seconds, the test has passed and the system moves to a “PASSTHROUGH” state. (It should be noted that the system may alternatively pressurize the cavity and then detect whether the monitored pressure falls below a predetermined level within a predetermined time period, indicating that a perforation may be present.) As illustrated inFIG. 4, the “PASSTHROUGH” condition cannot be reached unless the body cavity assessment has been performed. In this capacity, the perforation detection system circuitry and logic components function as a pre-test lockout means.

In the “PASSTHROUGH” condition the CO2is turned off and the vacuum pump is re-enabled by re-opening valve88. If the ENABLE button33has been pressed (automatic mode), RF power114(“APPLY RF POWER”) will be delivered automatically to the array44once the cavity assessment cycle has been completed and passed. If the ENABLE button has not been depressed (semiautomatic mode), the system moves through the “PASSTHROUGH” state and waits for footswitch actuation112(“WAIT FOR FOOTSWITCH”), The user must press the button to enable the RF generator and then press the foot switch32to deliver RF power114.

In the event the cavity assessment test is not passed after the30second timer has expired, an audible tone sounds and visual indicators flash. The system remains in a TEST FAIL state, step116, and awaits further action by the user. If the user presses the foot switch, the system re-sets to the initial ready state, step108, with the CO2flow off. The user may attempt the cavity assessment sequence as many times as desired. AsFIG. 4illustrates, the perforation detection system circuitry and logic components function as a post-test lockout means preventing delivery of RF power using the ablation device if the body cavity assessment is run but not passed.

Alternatively, after one or more cavity assessment procedures has been performed and failed, the user may choose to activate a form of override means to override the post-test lockout means and cause the system to deliver RF energy despite the cavity assessment test having been failed. To do so, the user will press and hold the ENABLE button33for six seconds. Note that the pressure check must be attempted at least one time before this feature is available. If the user overrides the cavity assessment, the system moves to the “PASSTHROUGH” state to wait for footswitch step112.

If at any time during the above sequence, the user should dose the ablation device, a DC short will be detected in the electrode array by the RF generators DC short detection circuitry. Closing the device causes the state of the perforation test to change to fail, and the system resets to the “WAIT FOR DEPLOY” state, step106. The system will then require that cavity assessment be performed again once the array is reopened. This assures that the last step performed before the application of RF energy is the perforation detection test: if the user, after having successfully completing the test, decides to close and remove the device for any reason, the perforation detection test must be performed again once the device is deployed in the body cavity. This requirement also prevents a user from abusing the system by running cavity assessment with the device outside the body, and then inserting the device, overriding the test, and ablating without having ever performed cavity assessment within the body cavity.

For additional safety, the perforation detection system preferentially uses CO2, though other gases or liquids, such as normal saline, may be used. The pressure and flow limits follow well known guidance documents for insufflators. In the case of uterine perforation detection, the limits follow hysteroflator guidance documents. Though other configurations are possible, the cavity to be assessed should be in series between the source and pressure signal lines. In this manner, any kinked tubing or other problems will not lead to a false test result. Additionally, the system is capable of detecting perforations exceeding the range of sizes of devices normally inserted into body cavities (from say 15 mm down to less than 1 mm diameter).

In order to reliably detect perforations in uterine cavities, the pressure threshold in that case is preferentially kept below the average cracking pressure of the fallopian tubes.

There are several features that improve the system's ease of use. Firstly, the physician can start or stop the perforation test at any time in the sequence. Secondly microprocessor34is capable of distinguishing the difference between a device that is closed versus a device that is undergoing slight motion in the body cavity, thus reducing the likelihood that a passed test condition will be overturned. Finally, the system includes a collar assembly63inFIG. 2awhich is capable of sealing the entry into the body cavity BC if leaks are determined to exist, thus reducing the likelihood of a false test failure.

Although the forgoing description is with reference to a perforation detection system having a device usable to ablate tissue within a uterus, the present invention is applicable to perforation detection within other body cavities, and to perforation detection systems having medical devices useful for procedures other than ablation. In addition, although the system is described with reference to a particular embodiment, many other configurations are suitable for implementing the teachings of the invention. Those having ordinary skill in the art will certainly understand from the embodiment disclosed herein that many modifications are possible without departing from the teachings hereof. All such modifications are intended to be encompassed within the following claims.