Abstract:
A pneumatic syringe driver having a control module for regulating pressure applied to the plunger of an associated syringe is disclosed. The syringe driver is adapted for receiving a compressed gas canister and for enabling the selective release of gas from the canister into a chamber, one wall of which being formed by the syringe plunger via a three-way valve. The valve also enables the selective venting of gas from the canister into the atmosphere, thereby forming a venturi which reduces the pressure in the chamber and causes the syringe plunger to be withdrawn into the chamber. A pressure sensor in communication with the control module is provided for pressure feedback. Pushbuttons or switches in communication with the control module are provided for defining the syringe driver operation. The device is suited for the selective inflation and deflation of a balloon attached to the syringe driver for a balloon angioplasty procedures.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent applications claims priority of U.S. Provisional Patent Application No. 60/322,832, filed Sep. 17, 2001. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND OF THE INVENTION 
     While devices have been developed for automatic control over syringe actuation, the size and power requirements of such devices suggest against their use in environments in which space is limited or external power is not readily available. Such devices have been employed for balloon inflation in various surgical procedures including the opening of strictures, or narrowings of bodily passages, such as in endoscopic dilation where a balloon is used to open an esophageal stricture. Another application is in balloon angioplasty. For example, such applications involve the use of a syringe for delivering pressurized fluid for inflating a balloon. However, in surgical settings, there tends to be minimal free space immediately proximate the surgical site, thus rendering large and complex syringe actuation devices inappropriate. Furthermore, the cost and complexity of such automatic devices make them appropriate for sequential, repeated use. Repeated use requires that the devices be cleaned, serviced, and periodically recalibrated, resulting in higher operating costs. 
     Without such devices, precise control over fluid dispensed from a syringe has typically required the manual manipulation of a syringe plunger by an operator. For example, a physician may apply axial pressure on a syringe plunger to force pressurized fluid into an attached balloon for inflation. Other mechanical interfaces have been proposed for coupling operator movements to the syringe piston. One example of such interfaces includes the use of threads between the plunger and the syringe barrel whereby rotation of the plunger results in a gradual axial progression (or regression) of the plunger. Reliance on human operation exposes the inflation or deflation procedure to significant variability in terms of total volume of pressure fluid dispensed, rate at which the fluid is dispensed, and susceptibility to drawback. 
     Consequently, there is a need for a compact and inexpensive device which can accurately control the dispensing of fluid from a syringe, particularly for balloon angioplasty applications. The compact size of the device would make it suitable for use in space-limited environments, while the lower cost would enhance its suitability for one-time or disposable use. 
     BRIEF SUMMARY OF THE INVENTION 
     The presently disclosed invention pertains to a pneumatic syringe driver having a control module for regulating pressure applied to the piston of an associated syringe. The syringe driver is also adapted for receiving a canister of compressed gas such as carbon dioxide. A valve mechanism and conduits are provided in the driver for enabling the selective release of gas from the canister into a chamber, one wall of which being formed by the syringe piston. The valve mechanism and conduits also enable the selective venting of gas from the canister into the atmosphere, thereby forming a venturi which reduces the pressure in the chamber and causes the syringe piston to be withdrawn into the chamber. 
     An on-board battery is provided for powering the control module and the valve mechanism. A pressure sensor in communication with the control module is provided in the syringe for feedback purposes. Visual display or indicator elements are also provided in various embodiments of the invention for conveying status relative to syringe internal pressure, battery life, and/or other pertinent device information. Input elements such as pushbuttons or switches are in communication with the control module for defining the operation of the syringe driver. 
     One particular application of the disclosed device is for selectively inflating and deflating a balloon attached to the syringe driver in a balloon angioplasty procedure. The balloon may be attached directly or indirectly to the syringe driver. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       These and other objects of the presently disclosed invention will be more fully understood by reference to the following drawing, of which: 
         FIG. 1  is a diagrammatic view of components of a pneumatic syringe driver according to the presently disclosed invention; 
         FIG. 2  is a flow chart illustrating a method of using the pneumatic syringe driver of  FIG. 1 ; and 
         FIGS. 3A and 3B  illustrate the configuration of a three-way valve of the pneumatic syringe driver of  FIG. 1  during various modes of operation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A first embodiment of the presently disclosed pneumatic syringe driver  10  is illustrated in  FIG. 1 . The device is comprised of two main portions, a control and gas canister portion  20  and a valve and syringe portion  30 . 
     The control and gas canister portion  20  includes a control module  22 , an operator input interface  24 , an operator output interface  26 , a battery compartment (not shown), and a gas canister receptacle  28 . 
     The control module  22  may comprise a custom integrated circuit or a digital signal processor or micro-controller with an associated and custom-programmed memory. In communication with the control module  22  and three-way valve  32  is a battery (not shown). A variety of batteries may be employed depending upon the power requirements of the active elements of the driver  10 . A small form factor is beneficial, however, due to the need for overall compactness. In an alternative embodiment, a power port is provided on the driver  10  for interfacing a remote power supply to the control module  22  and the electronic three-way valve  32 . 
     The operator input interface  24  comprises pushbuttons or switches and enables the operator to have one of several inflation routines executed by the control module  22  or to program a specific inflation regimen. The control module may respond immediately to each activation of an operator interface element, or may accumulate commands prior to be instructed to execute a programmed routine. Controls may be provided for commanding various degrees of balloon inflation, balloon inflation rate, and/or time delay between operations. Controls may also be provided for deflating the balloon according to the variables described above. In view of the applicability of the syringe driver  10  in surgical environments, it is preferred that the control interface elements be sealed and large enough to be actuated by gloved fingers. 
     The operator output interface  26  may comprise optical indicators such as light emitting diodes each have a predefined meaning. Alternatively, the output interface  26  may be comprised of a display screen, such as illustrated in  FIG. 1 . Various messages may be provided to an operator, including algorithm steps programmed, current programmed pressure, measured syringe pressure, projected gas pressure remaining, battery life, etc. 
     In a further embodiment, an electrical interface may be provided on the surface of the driver  10  and in communication with the control module for the purpose of enabling the remote programming of the inflation and deflation regimen, as well as the transmission of performance and status information to a remote terminal. 
     The control and gas canister portion  20  is provided in a first embodiment with a pre-installed gas canister which ahs a pierceable seal  50 . In this embodiment, an element such as a threaded cap  29  is used to thrust the canister into communication with a fluid conduit  51  that pierces the canister seal. In a second embodiment with a pre-installed gas canister, the canister is already in fluid communication with the fluid conduit. In a third embodiment, the syringe driver is provided without the gas canister, and an access element such as the threaded cap  29  enables canister installation. Once again, tightening the cap  29  results in the fluid conduit piercing the canister seal. 
     The valve and syringe portion  30  comprises an electronic three-way valve  32  with associated fluid conduits, a syringe  44 , a piston  34  dividing the syringe into a piston chamber  36  and a syringe chamber  38 , a pressure sensor  40 , and a balloon interface  42 . 
     In one embodiment of the syringe driver of the present disclosure, the three-way valve  32  is an electronically driven rotary valve operating under the control of the control module  22 . Alternatively, the valve may be provided as an electronically driven ball valve. Further still, the valve may be implemented through plural, independently displaceable shutters. Regardless of particular embodiment, a common requirement is that each port of the valve be gas-tight when closed. 
     One port of the three-way valve is in communication with the compressed gas canister once the canister is fully installed in the control and gas canister portion  20 . As previously mentioned, this portion of the fluid conduit is preferably provided with a sharpened point or similar feature for piercing a seal in the compressed gas canister. A resilient seal such as an O-ring of rubber or like material may be provided in one embodiment for sealing a forward end of the gas canister to the valve and syringe portion  30  of the driver  10 . 
     An anti-blow-by piston  34  is disposed for translation along the interior walls of the syringe  44 . One side of the piston  34  forms part of the piston chamber  36 , while another side of the piston  34  forms part of the syringe chamber  38 . As gas pressure builds in the piston chamber relative to that in the syringe chamber, the piston moves in order to equalize the pressures. A sealing ring or rings (not shown) may also be used intermediate the piston and the syringe  44  barrel. 
     The syringe chamber  38  preferably contains incompressible fluid which, depending upon the specific application, may be liquid or gas. A pressure sensor  40  mounted within the syringe chamber  38  is in communication with the control module  22 . Communication is preferably by way of sealed, electrically conductive wire (not shown). 
     While not illustrated in  FIG. 1  for simplicity, the balloon interface  42  may include projections or other physical features which facilitate the attachment of a balloon to the syringe driver  10 . Alternatively, the balloon interface  42  may be configured for use with a discrete fluid tube which is employed intermediate the balloon interface  42  and the balloon itself. The latter embodiment is particularly useful when the area surrounding a point of balloon insertion is limited or crowded with other surgical tools and instruments. 
     The operation of the pneumatic syringe driver  10  is now described with reference to  FIG. 2 . If the syringe driver  10  is provided to a user with a gas canister  28  pre-installed, the user prepares the driver  10  for use by placing the gas canister  28  in fluid communication with the compressed gas canister port of the three-way valve  32 , such as by tightening the threaded cap  29  against the canister  28 . This action causes a seal enclosing the canister to be pierced and places the canister contents in fluid communication with the valve  32 . 
     Alternatively, if the pneumatic syringe driver  10  is provided to the user without a pre-installed compressed gas canister  28 , such a canister is inserted and placed in fluid communication with the canister port of the three-way valve, such as in the manner just described. 
     If a balloon has not already been attached to the balloon interface  42  of the syringe driver, one is now attached, and the balloon is disposed in position for inflation as required. Alternatively, the balloon is disposed in the operating environment prior to it being attached to the syringe driver. 
     Through use of the operator input interface  24 , a user such as a surgeon can program the device to inflate the balloon according to a desired regimen. Then, once the driver and balloon are placed in the proper position and other surgical procedures have occurred or are ready to be performed, the inflation regimen can be started. 
     Inflation of the balloon occurs when the control module  22  commands the three-way valve  32  to open a fluid path from the gas canister  28  to the piston chamber  36  ( FIG. 3A ). This pathway is maintained until the pressure sensor  40  detects a target pressure reading in the syringe chamber  38 . As gas flows from the gas canister  28  into the piston chamber  36 , the piston chamber pressure will rise, resulting in the piston  34  being urged into the syringe chamber  38  and increasing the pressure in the balloon inflation fluid. Syringe chamber pressure may thus be one of the parameters programmed into the control module  22  via the operator input interface  24 . Once the proper pressure is achieved in the syringe chamber  38 , the three-way valve  32  is commanded by the control module  22  to close the fluid pathway. 
     Additional sequences of pressure increase in the piston chamber  36  may be affected by operation of the three-way valve until the desired balloon inflation is achieved. 
     Once the surgical procedure requiring balloon inflation has been completed, a certain portion of the inflation fluid pressure may be relieved by opening a fluid pathway between the piston chamber  36  and the atmosphere via the three-way valve  32 . However, there may still be sufficient pressure in the syringe chamber  38  to prevent complete deflation of the balloon. 
     To further reduce the syringe chamber  38  pressure, all three ports of the three-way valve  32  may be placed in mutual communication by the control module  22 , as in  FIG. 3B . This will result in a flow of gas from the canister to the atmosphere, thus creating a venturi with respect to the piston chamber  36 . As the compressed gas flows rapidly through the three-way valve towards the exterior port, the pressure within the valve decreases in accordance with the Bernoulli effect. This results in a flow of gas from the piston chamber into the valve and consequently the retraction of the piston  34  out of the syringe chamber  38 . The pressure in the syringe chamber  38  thereby decreases, and the attached balloon is further deflated. The control module may monitor the pressure within the syringe chamber  38  via the pressure sensor  40  in controlling the three-way valve  32 . The balloon may then be removed from its operating site. 
     The gas canister  28  is provided with enough pressurized gas to carry out the foregoing inflation regimen, including instances in which the attached balloon is inflated and deflated multiple times during a procedure. However, in order to minimize the size of the pneumatic syringe driver, only enough gas is provided to ensure operation for one procedure. The inexpensive electronics and battery power supply thus make the disclosed device ideal for single, disposable use. 
     These and other examples of the invention illustrated and described above are intended by way of example and the actual scope of the invention is to be limited solely by the scope and spirit of the following claims.