Patent Application
20070060834
The invention relates to a device coupleable with an indwelling catheter used in site specific therapy which combines the functions of data display and data storage and also contains a vacuum pump for withdrawal of collected bodily fluid. In one embodiment, the invention further contains an infusion pump.
A number of clinical conditions involve (e.g., are caused by and/or themselves cause) impaired circulation, and particularly circulation within interstitial spaces and within discrete, localized tissues. Among the more difficult examples of circulatory problems are those that involve localized tissue swelling, including compartment syndrome and edema (particularly cerebral edema), as well as solid and semisolid tumors forming confined sites within the body.
Acute compartment syndrome (ACS) generally involves impaired circulation within an enclosed fascial space (e.g., the anterior compartment of the lower leg), leading to increased tissue pressure and necrosis of muscle and nerves. The soft tissue of the lower leg is contained within four compartments, each bounded by heavy fascia: the anterior, lateral, superficial posterior, and deep posterior compartments. Once diagnosed, the injury requires immediate decompression through surgical release of the skin and fascia covering the area. Other proposed treatment strategies include the use of a sympathetic blockage, hyperbaric oxygen therapy and treatment with mannitol and allopurinol.
Several different apparatus and methods have been proposed for treating ACS. Among these are drainage by the use of catheters and similar instruments inserted into tissue sites including syringes, breast pumps, dental suction devices and waste gas scavenging. See, for example, the Mini VAC (Vacuum Assisted Closure) device, available from KCl (San Antonio, Tex.). The Mini VAC device provides negative pressure therapy for treating chronic and acute wounds and allows for the measurement and displaying of therapy at the wound site through micro-processor control and multi-lumen tubing. Negative pressure is applied to a special dressing positioned in a wound cavity or over a flap or graft. The pressure distributing wound dressing supposedly helps remove fluids from the wound. It should be mentioned that the Mini Vac is not used to prevent ACS but rather to treat the wound from the fasciotomy to decompress ACS.
A “mechanical leech” has been developed, which attaches to a wound site to remove blood and promote wound healing. See, the University of Wisconsin Press release dated Dec. 12, 2001, “Novel Device Takes Over Where Medicinal Leeches Leave Off.”
See also U.S. Pat. No. 5,484,399, which describes a method and apparatus for reducing interstitial fluid pressure in tissues, particularly in tumors, by applying suction to the interior of the tissue. The method comprises inserting into the tissue one or more needle-like, elongated tubes, each having at least one hole at or near the end that is inserted into the tissue and each having means to apply suction to the protruding end. Components may be provided to measure the pressure within the tissue and to use this measurement to control the suction applied to the tissue through the tubes.
Applicant has also previously described methods and related systems for use in site specific therapy of a tissue site. See issued U.S. Pat. Nos. 6,030,358, 6,537,241 and published PCT application PCT/US98/16416, the disclosures of which are all incorporated herein by reference. In one embodiment, the PCT application provides a system that comprises one or more catheters adapted to be positioned within the tissue site and a delivery/recovery mechanism for employing the catheter(s) to control the movement of bulk fluids and/or active fluid components within or between tissue portions or adjacent tissues in a manner that achieves a therapeutic effect. The catheters, in turn, can comprise one or more semipermeable microcatheters, adapted to effect the movement of fluid or fluid components within the tissue site by microdialysis within the tissue site. In its various embodiments, the system previously described by Applicant can be used for the treatment of a variety of disorders, including cerebral edema and compartment syndrome.
Bioactive agents, such as drugs, have long been delivered to the body by a wide variety of methods, including ingestion, inhalation, injection and transdermally, among others. With any remote or systemic delivery the ability of the delivered drug to access its intended site of action is often dependent on a number or parameters, including: (1) the flow kinetics of fluids containing such drugs, such as blood, into or through the desired site; (2) the concentration and form of drugs within those fluids; and (3) the extent to which the drug is able to be transferred to, or concentrated within, the desired site from the fluid. As compared with systemic delivery, site specific approaches for delivering drugs have been developed as well and include the use of indwelling catheters and implantable drug delivery devices.
The delivery of drugs to tumors, however, presents additional challenges beyond those associated with both systemic and site specific delivery techniques. Reduced perfusion to tumors is known to limit the ability to effectively deliver chemotherapeutic agents to the tumor. One of the most pervasive and compelling theories regarding causation is the Baxter-Jain hypothesis, which states that elevated tissue pressure within the tumor limits tumor perfusion. The theory and modeling suggest that absence of lymphatics plays a key role in pathogenesis of the interstitial hypertension.
A variety of approaches have been considered to improve the delivery of drugs to tumors. For instance infusion of fluid directly into tissues bypasses the microcirculatory system and has been attempted with mixed results. Investigators have shown, for instance, that fluid injected too rapidly into tumors caused a shearing action that results in an inhomogeneous distribution.
More recently, improved perfusion by the removal of excess interstitial fluid has been proposed as well. See the papers and patents or applications of DiResta et al., including Ann. biomed. Eng. 28:543-555 (2000) and Ann. Biomed Eng. 28:556-564 (2000), as well as U.S. Pat. No. 5,484,399 (“Process and Device to Reduce Interstitial Fluid Pressure in Tissue”), and U.S. Patent Pub. US2001/0047152 (“Apparatus and Method for Reducing Interstitial Fluid Pressure and Enhancing Delivery of a Therapeutic Agent”).
DiResta et al. suggest a therapeutic effect can be derived by the alleviation of interstitial hypertension and have developed an “artificial lymphatic system” or “ALS”. These various references establish that removal of fluid from tumors increase blood flow, oxygenation and delivery of a dye to the hypoperfused center. In these studies, an “aspiration probe”, in the form of a stainless steel needle, was used to remove tissue fluid. DiResta et al. also demonstrated that fluid removal will result in shrinkage of the tumor compared with controls when chemotherapeutic drug treatment is given systemically. The device consists of a needle with slits along its length that is inserted into the center of the tumor through which suction is applied. Treatment with ALS has reduced interstitial hypertension, increased tumor blood flow, and enhanced dye penetration into the tumor. When used with intravenous chemotherapy, ALS has resulted in significant reduction in tumor growth.
U.S. Patent Publication 2001/0047152 (DiResta et al.) further describes the manner in which cancer therapy may be categorized into three major approaches: (1) Surgical Excision; (2) Radiotherapy; and (3) Chemotherapy. Chemotherapy is defined as the treatment of cancer by a systemic administration of drugs. Unfortunately, most drugs which showed promising effects in vitro have failed to be as effective in vivo, particularly in solid tumors. It has been suggested that one of the major reasons for this failure is the impediment of drug transport into tumors. In particular, a physiological barrier created by raised interstitial fluid pressure appears to be responsible the interstitial fluid pressure is raised in tumors primarily because of the lack of lymphatics in tumors and growth of tumor cells in confined spaces. The raised interstitial fluid pressure in tumors is a principal transport-retarding factor for the delivery of drugs such as macromolecules, i.e., large molecular weight molecules such as monoclonal antibodies (MoAb), tumor necrosis factor and other chemotherapeutic agents.
The above-cited DiResta et al. application goes on to describe an interstitial fluid pressure reducing apparatus that includes an aspiration probe having a body with an open proximal end and a closed distal end, an interior chamber defined by the body and proximal and distal ends, and at least one slit along the body providing fluid communication between the chamber of the aspiration probe and tissue upon insertion of at least a portion of the aspiration probe in tissue. The proximal end is configured and dimensioned for coupling to a suction source for generating suction in the chamber of the aspiration probe upon connection with the aspiration probe to thereby reduce interstitial fluid pressure of the tissue.
Despite these promising findings, the above-cited DiResta articles each describe various “limitations” to their use of ALS, including apparent limitations regarding the extent of vacuum that can be safely applied to the aspiration probe, and the concern that drugs may be removed along with the fluid itself. The authors describe the range of about −50 to −80 mm Hg as being an optimal vacuum range under their experimental conditions. In addition, the small holes of the ALS could potentially be problematic. As a result, long term use of the ALS may be further complicated by the lack of a mechanism to secure the drains of the ALS to the tissue so that the drains remain spatially fixed. Finally, the ALS had no features that facilitate use with adjunct therapies that enhance drug delivery. Use of various other therapies to enhance efficacy of the ALS would be desirable. However, until now, no other adjunct therapy has been used in conjunction with the ALS.
In an effort to address interstitial hypertension within the body, including that associated with tissue swelling and tumor formation, Applicant has developed systems, methods and apparatus allowing integrated pressure monitoring, aspiration and fluid infusion (See U.S. Pat. Nos. 6,030,358, 6,537,241, U.S. Patent Publications 2003-0167031, 2003-0187367, Ser. No. 10/508,610, and PCT/US03/08921, the disclosures of which are herein incorporated by reference. While systems, methods and apparatus have been developed to monitor pressure, aspirate and infuse fluids, separate pieces of equipment are presently used to achieve each of these functions. What is clearly needed is, therefore, a single unit attachable to the indwelling pressure monitoring, infusing and fluid collection catheter that is able to interpret and monitor pressure signals, remove water and other fluids and also infuse fluids into the treatment site.
In one aspect, the invention comprises a console for use with an indwelling pressure monitoring, infusing and fluid collection catheter, having a power supply for supplying uniform and controlled energy. A vacuum pump is coupleable to the catheter for extraction of bodily fluids collected by the catheter and an infusion pump is coupleable to the catheter for infusion of fluids. A pressure signal conditioner is in communication with a pressure transducer coupled to the catheter for converting analog pressure signals generated by the pressure transducer to digital signals. A microprocessor control unit is in communication with the vacuum pump controlling extraction of bodily fluids through the catheter and in communication with the infusion pump for infusing fluids through the catheter and in communication with the pressure transducer for processing received digital pressure signals. A display is also part of the console for displaying parameters and processed pressure signals.
In another aspect, the invention comprises a console for use with an indwelling pressure monitoring, infusing and fluid collection catheter, the catheter having a pressure tube, an outer tube defining a lumen and hollow fibers in fluid communication with the lumen of the outer tube. A vacuum pump is coupleable to the outer lumen of the catheter for extraction of bodily fluids collected by the catheter and an infusion pump is coupleable with the pressure tube of the catheter for infusion of fluids collected by the hollow fibers. A pressure signal conditioner is in communication with a pressure transducer coupled to the pressure tube for converting analog pressure signals generated by the pressure transducer to digital pressure signals. A microprocessor control unit is in communication with the vacuum pump for controlling extraction of bodily fluids according to parameters and in communication with the infusion pump for controlling fluid infusion according to parameters and processing received pressure signals. A user interface is in communication with the microprocessor control unit for setting parameters; and a display is in communication with the microprocessor control unit for displaying set parameters and processed pressure signals.
In yet another aspect, the invention comprises a console for use with an indwelling pressure monitoring, infusion and fluid collection catheter, the catheter having a pressure tube, an outer tube defining a lumen and hollow fibers in fluid communication with the lumen of the outer tube comprising. A vacuum pump is coupleable to the outer lumen of the catheter for extraction of bodily fluids collected by the catheter and an infusion pump is coupleable with the pressure tube of the catheter for infusion of fluids collected by the hollow fibers. The console has a power section, comprising a power supply attachable to a power source, a battery charger attached to the power supply and a battery attached to the battery charger. Also included within the power section is a power switch over attached to the power supply and the battery for providing battery power when the power source fails. A battery charge monitor is in communication with the battery and a microprocessor control unit to monitor the battery to determine when battery voltage drops below a predetermined value and allow the battery charger to charge the battery and to prevent overcharging of the battery. A power conditioning power supply for suppressing electrical surges and supplying a uniform power stream to the microprocessor.
The console has a digital section, comprising the microprocessor control unit connected to the power switch over and to the battery charger for controlling battery charging. The microprocessor control unit is in communication with the vacuum pump for controlling extraction of bodily fluids according to parameters and in communication with the infusion pump for controlling fluid infusion according to parameters and processing received pressure signals. A display is in communication with the microprocessor control unit for displaying set parameters and processed pressure signals. A user interface is in communication with the microprocessor control unit for communicating with the microprocessor control unit and for setting parameters and an NV RAM unit is in communication with the microprocessor control unit for storing the operating system and software. An infusion pump control is in communication with the microprocessor control unit and the infusion pump to control the rate of infusion and whether the infusion pump is on or off. Likewise, a vacuum pump control is in communication with the microprocessor control unit and the vacuum pump to turn the vacuum pump on and off. A real time clock is in communication with the microprocessor control unit to record the timing of the medical procedure and a USB interface is in communication with the microprocessor control unit to allow for downloading or transfer of generated data.
The console also has an analog section comprising a pressure signal conditioner in communication with a pressure transducer coupled to the pressure tube for converting analog pressure signals generated by the pressure transducer to digital pressure signals. An isolation transformer is connected between the microprocessor and the pressure signal conditioner to absorb excess voltage.
In an alternative aspect, the invention comprises console for use with an indwelling pressure monitoring/fluid collection catheter. The console has a power supply for supplying uniform and controlled energy and a vacuum pump coupleable to the catheter for extraction of bodily fluids collected by the catheter. A pressure signal conditioner is in communication with a pressure transducer embedded within the catheter for converting analog pressure signals generated by the pressure transducer to digital signals. A microprocessor control unit is in communication with the vacuum pump for controlling extraction of bodily fluids through the catheter and with the pressure transducer for processing received digital pressure signals. A display is in communication with the microprocessor control unit for displaying parameters and processed pressure signals.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.
a is a longitudinal section of the catheter taken at the point that the hollow fibers emerge from the outer tube as designated by brackets 2a-2a.
a is a cross section taken through lines 3a-3a of the catheter shown in
“Coupleable” means capable of being coupled to another structure.
“CRT” refers to a cathode ray tube.
“LCD” refers to a liquid crystal display.
“Mounting Platform” refers to any structure used to mount the components of the invention on.
In another embodiment, a catheter (not shown) similar to the catheter 10 embodiment shown in
a is a lateral section of the portion of the catheter body 12 where the hollow fibers 104 terminate inside the first lumen 108 of the outer tube 106.
The microprocessor 210 is separately and electrically connected to the various components of the digital section: an NV RAM 222 is electrically and directly connected to the microprocessor 210 which stores the operating system, software and collected data; keypad 220 is electrically and directly connected to the microprocessor 210 which allows the console operator to access the various functions provided by the console 200 and input information as required; a display 202 is electrically and directly connected to the microprocessor 210 which can be a CRT, LCD, LED or other digital or analog display type and displays the various functions and readings made by the indwelling pressure displaying, infusing and fluid collection catheter system 10; a real time clock 212 is electrically and directly connected directly to the microprocessor 210 to eventually display and record the timing of the medical procedure. It should be mentioned that a display 202 could also incorporate touch screen technology (not shown) wherein the keypad 220 appears as part of the display and control is achieved by touching the appropriate area of the screen. A vacuum pump control 216 is electrically and directly connected to the microprocessor 210 and in turn electrically and directly connected to a vacuum pump 204. The vacuum pump control 216 functions to turn the vacuum pump 204 on and off as well as regulate the amount of vacuum produced, however, the vacuum pump control 216 is optional and the console 200 would also function using a continuous vacuum. In another embodiment, a mechanical valve (not shown) is manually opened or closed by the operator as deemed necessary for treatment.
An infusion pump control 234 is electrically connected to the microprocessor 210 and electrically connected to the infusion pump 206 and functions to control the rate of infusion as well as whether the infusion pump 206 is on or off. In one embodiment the infusion pump 206 is a simple syringe pump (not shown) of conventional design and well known to those having ordinary skill in the art, in which a loaded syringe (not shown) is loaded into a mechanism which depressed the syringe plunger, thus infusing the loaded fluid. A suitable syringe pump (not shown) is model NE-500, manufactured by New Era Pump Systems, Farmingdale, N.Y. In another embodiment (not shown) the infusion pump 206 comprises a fluid impermeable sac containing fluid which is pressurized by applying external mechanical pressure on the sac.
A USB interface 214 is electrically connected to the microprocessor 210 and functions as an attachment point for a memory stick 236 to download and save data for future use or analysis.
In the analog section 244 a pressure signal conditioner 254 is coupleable with the pressure transducer 18 which is discussed in detail above. The pressure signal conditioner 254 amplifies and filters out electronic noise in electrical signals generated by the pressure transducer 18 and is electrically connected with the isolation transformer 256. The isolation transformer 256 is in communication with the microprocessor 210 and functions to absorb excess voltage and also to isolate the line voltage from the patient. A suitable isolation transformer is part number 9399-V2-00, manufactured by Piltron, Toronto, Ontario.
In operation the indwelling pressure displaying, infusing and fluid collection catheter system 10 is connected to the displaying, infusion and collection console 200 by connecting the electrical connection 32 (emanating from the pressure transducer 18) to a pressure signal port 246. The pressure transducer 18 is connected to the pressure line 16 which is connected to the first branch 14a of the first Y connector 14, which is connected to the second lumen 112 of the inner tube 110. The infusion line 23 is connected to the infusion pump 206 via an infusion pump port 248 on its proximal end and to the pressure line 16 on its distal end. The vacuum pump 204 is connected to the first lumen 108 by vacuum line 28 via vacuum connector 30.
The invention does not show, but contemplates and therefore encompasses in scope, an input (not shown) for a blood pressure sensor (not shown). A blood pressure sensor (not shown), integrated with the catheter (not shown) or independent (not shown) would generated blood pressure signals which would be read by the console. Blood perfusion pressure (the difference between blood pressure and tissue pressure) would be calculated, displayed and stored by the console.
Using the present invention involves inserting the indwelling pressure displaying and fluid collection catheter 10 into the targeted muscle compartment by skin puncture via an introducer (not shown). The second lumen 112 is infused with saline solution prior to insertion and connected to the pressure transducer 18 which generates and sends analog electrical signals to the microprocessor 210 via the pressure signal conditioner 254, which are eventually displayed on the display 202. Interstitial fluid pressure is measured at the tip 102 of the catheter body 12 through the slit pressure lumen 100. Fluid within the second lumen 112 is displaced corresponding with the amount of pressure within the muscle compartment or tumor and the pressure transducer 18 generates a signal which is transmitted to the display 202 where a reading can be manually taken or digitally recorded. Catheter 12 patency is maintained by the slit pressure lumen 100 and by continuous infusion of a very small volume of sterile normal saline (approximately 5 μL/hr) by the infusion pump 206 which is connected to and in fluid communication with the second lumen 112.
The first lumen 108 is typically maintained under cyclic on/off vacuum (−50 mm Hg for 3 minutes, 0 mm Hg for 3 minutes) by connection with the vacuum pump 204. During the vacuum phase interstitial fluid passes through the hollow fibers 104 and moved from the first lumen 108 within catheter 12 eventually to the fluid collection port 26, where it is collected. Fluid samples can be taken from the reservoir when desired using a standard syringe. During the off phase, interstitial fluid is replenished in the region near the catheter tip 102 by the hydraulic pressure gradient induced during the vacuum phase. Pressure readings are observed on the display 202 and treatment adjusted as necessary.
The immediate effect of using the console 200, 300 when attached to a catheter system 100, 400 is that the removal of fluid reduced the interstitial pressure or at least prevents the pressure from increasing. The pressure monitoring function is used to verify that interstitial pressure has been reduced or not increased. Fluid removed during the procedure can then be used for analysis to aid in determining further treatment. In the case of Compartment syndrome, it is possible that the analysis will determine if the patient is developing Compartment Syndrome, wherein additional measures can be taken. In other applications, such as tumors, additional diagnostics can be done to determine further treatment.
Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the sprit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.
