Abstract:
A dual pump aspiration system having both a vacuum level control loop and a flow rate control loop. The system can be operated either as a vacuum priority system or a flow rate priority system and uses a vacuum chamber of variable volume within the vacuum pathways.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    During small incision surgery, and particularly during ophthalmic surgery, small probes are inserted into the operative site to cut, remove or otherwise manipulate tissue. During these surgical procedures, the surgical site typically is flushed with an irrigating solution and the irrigating solution and tissue is aspirated from the surgical site. The types of aspiration system used, prior to the present invention, where generally characterized as either flow controlled or vacuum controlled, depending upon the type of pump used in the system, and each type of system has certain advantages.  
           [0002]    Vacuum controlled aspiration systems are operated by setting a desired vacuum level, which the system seeks to maintain. Flow rate information is unavailable. Vacuum controlled aspiration systems typically use a venturi or diaphragm pump. Vacuum controlled aspiration systems offer the advantages of quick response times, control of decreasing vacuum levels and good fluidic performance while aspirating air, such as during an air/fluid exchange procedure. Disadvantages of such systems are the lack of flow information resulting in high flows during phacoemulsification/fragmetation coupled with a lack of occlusion detection. Vacuum controlled systems are difficult to operate in a flow controlled mode because of the problem of non-invasively measuring flow in real time.  
           [0003]    Flow controlled aspiration systems are operated by setting a desired aspiration flow rate for the system to maintain. Flow controlled aspiration systems typically use a peristaltic, orbital or vane pump. Flow controlled aspiration systems offer the advantages of stable flow rates and automatically increasing vacuum levels under occlusion. Disadvantages of such systems are relatively slow response times, undesired occlusion break responses when large compliance components are used and vacuum can not be linearly decreased during tip occlusion. Flow controlled systems are difficult to operate in a vacuum controlled mode because time delays in measuring vacuum can cause instability in the control loop, reducing dynamic performance.  
           [0004]    One surgical system currently commercially available, the Millennium from Storz Instrument Company, contains both a vacuum controlled aspiration system (using a venturi pump) and a flow controlled aspiration system (using an orbital pump). The two pumps can not be used simultaneously, and each pump requires separate aspiration tubing and cassette.  
           [0005]    Another currently available system, the ACCURUS® system from Alcon Laboratories, Inc., contains both a venturi pump and a peristaltic pump that operate in series. The venturi pump aspirates material from the surgical site to a small collection chamber. The peristaltic pump pumps the aspirate from the small collection chamber to a larger collection bag. The peristaltic pump does not provide aspiration vacuum to the surgical site. Thus, the system operates as a vacuum controlled system.  
           [0006]    Accordingly, a need continues to exist for a surgical system that operates in both vacuum controlled and flow controlled modes.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention improves upon prior art by providing a dual pump aspiration system having both a vacuum level control loop and a flow rate control loop. The system can be operated either as a vacuum priority system or a flow rate priority system and uses a vacuum chamber of variable volume within the vacuum pathways. The vacuum chamber has an inner housing and an outer housing that are movable relative to each other.  
           [0008]    Accordingly, an objective of the present invention to provide a dual pump aspiration system.  
           [0009]    Another objective of the present invention to provide an aspiration system having both a vacuum level control loop and a flow rate control loop.  
           [0010]    A further objective of the present invention to provide an aspiration control system and method that can be operated either as a vacuum priority system or a flow rate priority system.  
           [0011]    A further objective of the present invention to provide an aspiration control system having a vacuum chamber of variable volume.  
           [0012]    Other objectives, features and advantages of the present invention will become apparent with reference to the drawings, and the following description of the drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic diagram of a first embodiment of the dual mode system of the present invention.  
         [0014]    [0014]FIG. 2 is a schematic diagram of a second embodiment of the dual mode system of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    As best seen in FIG. 1, system  10  of a first embodiment of the present invention generally contains vacuum pump  12 , flow pump  14 , variable volume chamber (VVC)  16 , optical sensor  20 , collection chamber  22  and handpiece  26 . Vacuum pump  12  may be any  67  suitable pump, such as a diaphragm pump, a vane pump, an orbital pump or a peristaltic pump, but a venturi pump is preferred. Flow pump  14  may be any suitable pump, such as a venturi pump, a diaphragm pump, a vane pump or an orbital pump, but a peristaltic pump is preferred. VVC  16  contains inner housing  17  and outer housing  18  separated by seals  19 . Inner housing  17  is sized to reciprocate within outer housing  18  by, for example, stepper motor or other driver  34 , so as to define variable interior volume  21 . VVC  16  may be of any suitable shape in cross-section, but elliptical is preferred. VVC  16  preferably is made from optically clear, medical grade thermoplastic. Optical sensor  20  may be any suitable device for measuring the relative position of inner housing  17  and outer housing  18 . Interior volume  21  is fluidly connected to collection chamber  22  through outer housing  18 , line  24  and valve V 1 . Flow pump  14  is fluidly connected to interior volume  21  and collection chamber  22  through inner housing  17 , line  28  and line  24 . Handpiece  26  is fluidly connected to interior volume  21  through outer housing  18 , line  30  and valve V 3 . Vacuum pump  12  is fluidly connected to interior volume  21  through outer housing  18 , line  32  and valve V 4 .  
         [0016]    The connections to vacuum pump  12  and flow pump  14 , as well as VVC  16 , collection chamber  22 , fluid lines to VVC  16  and valves V 1  and V 3  preferably are all contained within or withon a common housing or cassette for attachment to a control console (not shown) using latch mechanism  36 . Vacuum pump  12 , flow pump  14  and valve V 4  are preferably contained in the control console.  
         [0017]    In use, system  10  of the present invention is first primed by opening valve V 3  and motor  34  drawing out inner housing  17  from within outer housing  18 , thereby increasing the size of interior volume  21  and drawing fluid into interior volume  21  through handpiece  26 , line  30  and outer housing  18 . When inner housing  17  reaches a predetermined location, as sensed by optical sensor  20 , movement of inner housing  17  stops, valve V 3  is closed, valve V 4  is opened and flow pump  14  is started, thereby draining fluid from interior volume  21  and into collection chamber  22  through line  28  and drawing air into interior volume  21  through valve V 4 . Operation of flow pump  14  is stopped prior to draining the contents of interior volume  21 , valve V 4  is closed and valve V 1  is opened. Motor  34  then moves inner housing  17  into outer housing  18 , forcing the remaining air and fluid within interior volume  21  into collection chamber  22  through line  24 .  
         [0018]    To operate system  10  in a vacuum control mode, valves V 3  and V 4  are closed and  67  valve V 1  is opened. Inner housing  17  is driven by motor  34  into outer housing  18  to a “home” or fully closed position. Valve V 1  is closed and valve V 4  is opened. Inner housing  17  is drawn out of outer housing  18  to a predetermined position so as to provide the optimum volume for interior volume  21 . Vacuum pump  12  is then set to the desired aspiration vacuum level and valve V 3  is opened, allowing fluid to flow through handpiece  26  and line  30  into interior volume  21 . When the fluid level in interior volume  21  reaches its maximum, flow pump  14  activates to drain fluid out of interior volume  21  and into collection chamber  22 .  
         [0019]    To operate system  10  in a flow control mode, valves V 3  and V 4  are closed and valve V 1  is opened. Inner housing  17  is driven by motor  34  into outer housing  18  to a “home” or fully closed position. Valve V 1  is closed. Fluid flow rate may be maintained in two alternative methods. In the first method, valve V 3  is opened and inner housing  17  is drawn from outer housing  18  by motor  34  at a predetermined speed so as to cause a vacuum to be created in interior volume  21  and thereby provide the desired flow rate through handpiece  26  and line  30 . When inner housing  17  reaches the full extent of its travel (as sensed by sensor  20 ), valve V 3  is closed and valve V 1  is opened. Inner housing  17  is then forced back within outer housing  18  by motor  34 , thereby pressurizing interior volume  21  and forcing fluid out of interior volume  21  and into collection chamber  22  through line  24  until inner housing  17  reaches the “home” position. The cycle discussed above is then repeated until the surgical procedure is completed.  
         [0020]    In a second flow control method, inner housing  17  is drawn out of outer housing  18  by motor  34  to a predetermined location so as to provide an optimum volume for interior volume  21 . Flow pump  14  is activated and run at a speed sufficient to provide the required fluid flow rate into from interior volume  21  to collection chamber  22  through line  28 .  
         [0021]    As best seen in FIG. 2, system  110  of a second embodiment of the present invention generally contains vacuum pump  112 , flow pump  114 , variable volume chamber (VVC)  116 , fixed volume chamber (FVC)  115 , optical sensor  120 , collection chamber  122  and handpiece  126 . Vacuum pump  112  may be any suitable pump, such as a diaphragm pump, a vane pump, an orbital pump or a peristaltic pump, but a venturi pump is preferred. Flow pump  114  may be any suitable pump, such as a venturi pump, a diaphragm pump, a vane pump or an orbital pump, but a peristaltic pump is preferred. VVC  116  contains inner housing  117  and outer housing  118  separated by seals  119 . Inner housing  117  is sized to reciprocate within outer housing  118  by, for example, stepper motor or other driver  134 , so as to define variable interior volume  121 . VVC  116  may be of any suitable shape in cross-section, but elliptical is preferred. VVC  116  and FVC  115  preferably are made from optically clear, medical grade thermoplastic. Optical sensor  120  may be any suitable device for measuring the relative position of inner housing  117  and outer housing  118 . Interior volume  121  is fluidly connected to collection chamber  122  through outer housing  118 , line  124  and valve V 1 . Flow pump  114  is fluidly connected to interior volume  121  and collection chamber  122  through inner housing  117 , line  128  and line  124 . Handpiece  126  is fluidly connected to interior volume  121  through outer housing  118 , line  138 , valve V 2 , line  130  and valve V 3 . Vacuum pump  112  is fluidly connected to interior volume  121  through outer housing  118 , line  136 , valve V 6 , FVC  115 , line  132  and valve V 4 . FVC  115  is fluidly connected to handpiece  126  through valve V 5  and line  130 .  
         [0022]    The connections to vacuum pump  112  and flow pump  114 , as well as VVC  116 , FVC  115 , collection chamber  122 , fluid lines to VVC  116  and FVC  115  and valves V 1  V 2 , V 3  V 5  and V 6  preferably are all contained within or withon a common housing or cassette for attachment to a control console (not shown) using latch mechanism  140 . Vacuum pump  112 , flow pump  114  and valve V 4  are preferably contained in the control console.  
         [0023]    In use, system  110  of the present invention is first primed by opening valve valves V 3 , V 5  and V 6  and motor  134  drawing out inner housing  117  from within outer housing  118 , thereby increasing the size of interior volume  121  and drawing fluid into interior volume  121  through handpiece  126 , lines  130  and  136  and outer housing  118 . When inner housing  117  reaches a predetermined location, as sensed by optical sensor  120 , or after a predetermined time, valves V 5  and V 6  are closed and valve V 2  is opened. Outward movement of inner housing  117  continues until an appropriate fluid level in interior volume  121  is reached or the appropriate amount of time has pasted at which time valves V 3  and V 2  are closed, valve V 4  is opened and flow pump  114  is started, thereby draining fluid from interior volume  121  and into collection chamber  122  through line  128  and drawing air into interior volume  121  through valve V 4 . Operation of flow pump  114  is stopped prior to draining the contents of interior volume  121 , valve V 4  is closed and valve V 1  is opened. Motor  134  then moves inner housing  117  into outer housing  118 , forcing the remaining fluid within interior volume  121  into collection chamber  122  through valve V 1  and line  124 .  
         [0024]    To operate system  110  in a vacuum control mode, valves V 3 , V 5  and V 6  are closed. and valve V 1  is opened. Inner housing  117  is driven by motor  134  into outer housing  118  to a “home” or fully closed position. Valve V 1  is closed and valve V 4  is opened. Inner housing  117  is drawn out of outer housing  118  to a predetermined position so as to provide the optimum volume for interior volume  121 . Vacuum pump  112  is then set to the desired aspiration vacuum level and valves V 2 , V 3  and V 6  are opened, allowing fluid to flow through handpiece  126 , lines  130  and  138  and valve V 2  into interior volume  121  and through line  136  into FVC  115 . In this manner, FVC  115  acts as a fluid capacitor, providing a fluidic buffer between vacuum pump  112  and VVC  116 . When the fluid level in interior volume  121  reaches its maximum, flow pump  114  activates to drain fluid out of interior volume  121  and into collection chamber  122 .  
         [0025]    To operate system  110  in a flow control mode, valves V 5  and V 6  are closed and valves V 2  and V 3  are opened and inner housing  117  is driven by motor  134  into outer housing  118  to a “home” or fully closed position. Valve V 1  is closed. This flow rate may be maintained in two alternative methods. In the first method, inner housing  117  is drawn from outer housing  118  by motor  134  at a predetermined speed so as to provide the desired flow rate through handpiece  126  and lines  130  and  138 . When inner housing  117  reaches the full extent of its travel (as sensed by sensor  120 ), valve V 2  is closed and valve V 1  is opened. Inner housing  117  is then forced back within outer housing  118  by motor  134 , thereby forcing fluid out of interior volume  121  and into collection chamber  122  through line  124  until inner housing  117  reaches the “home” position. The cycle discussed above is then repeated until the surgical procedure is completed.  
         [0026]    In a second flow control method, inner housing  117  is drawn out of outer housing  118  by motor  134  to a predetermined location so as to provide an optimum volume for interior volume  121 . Flow pump  114  is activated and run at a speed sufficient to provide the required fluid flow rate into from interior volume  121  to collection chamber  122  through line  128 .  
         [0027]    One skilled in the art will recognize that other methods of operating systems  10  and  110  are possible.  
         [0028]    While certain embodiments of the present invention have been described above, these descriptions are given for purposes of illustration and explanation. Variations, changes, modifications and departures from the systems and methods disclosed above may be adopted without departure from the scope or spirit of the present invention.