Abstract:
An apparatus for sealing a passageway through an access assembly includes a variable seal member having an orifice for reception of an instrument therethrough. Each of a pair of compression members has a pressure face for contacting the variable seal member, each pressure face opposing the variable seal member from an opposite longitudinal side, and each compression member moveable with respect to the other compression member in a longitudinal direction transverse to the pressure faces. The compression members may be moved in the longitudinal direction to adjust the degree of compressive force exerted on the portal seal member and thus adjust a diameter of the orifice to effectively interface with the instrument to form a fluid tight relation therewith.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/163,557 filed on Mar. 26, 2009, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to a surgical portal apparatus employing a system for maintaining a fluid-tight seal across a passageway for surgical instruments. In particular, the disclosure relates to a portal apparatus employing a variable diameter seal with a longitudinal displacement mechanism in communication with a power source for accommodating instruments of various sizes. 
     2. Background of Related Art 
     Surgical procedures such as laparoscopic, arthroscopic, and endoscopic procedures in general are termed minimally invasive at least in part because the incision required is relatively small, perhaps one inch in length or less. Small incisions are preferred because they are inherently less traumatic to the surrounding body tissue. Also, small incisions subject internal organs to a limited exposure to the contaminants in the outside atmosphere. Thus, small incisions enable shorter hospital stays and faster recoveries with less pain and scarring than is common with the larger incisions required for conventional surgery. 
     Endoscopic surgery is possible due in part to the availability of instruments designed specifically for this purpose. A trocar assembly, for example, may include a sharp trocar or obturator for creating a small incision, and a cannula assembly for providing a conduit through the incision once the obturator has been removed. A cannula is an elongated tube, typically 5 mm to 13 mm in diameter, which may be configured to have a distal end inserted into an internal body cavity adjacent an operative site. The body cavity is often inflated with an insufflation gas, carbon dioxide for example, to separate the body wall from vital organs. This provides a space where a surgeon may introduce viewing equipment or maneuver tools into position without damaging surrounding tissue. Various other instruments may then be inserted and withdrawn through the cannula for access to the working space and operative site. In order to fit through a cannula and enable a surgeon to manipulate tissue far removed from the incision, instruments adapted for endoscopic surgery typically include a long and narrow cylindrical shaft. The exact size and shape of the instrument shaft, however, may vary for the many instruments required for a single procedure. 
     Endoscopic procedures generally require that any instrumentation inserted into the patient&#39;s body be sealed, i.e. provisions must be made to ensure insufflation gasses, blood and other fluids do not escape the body through the cannula. Furthermore, a seal acts to prevent contamination of the body cavity by the outside environment. In the absence of such a fluid-tight seal, many of the attendant advantages of minimally invasive surgery are lost. 
     A dual seal system is commonly employed wherein a first seal is normally biased to a closed condition to seal the conduit in the absence of an instrument, and a second seal configured to form a fluid-tight interface with the shaft of an instrument. The second seal must be adaptable to accommodate the various instrument sizes and geometries. Often the second seal takes the form of a septum seal, which is a generally flat, elastomeric member having an orifice therethrough. The orifice may be sized such that the smallest instrument may not pass through the septum seal without engaging and forming a seal with the elastic material. The elasticity of the septum seal permits the orifice to expand to accommodate the largest instrument. 
     An aspect of concern in the use of such a septum seal is the contact pressure applied by the septum seal on the instrument shaft. If the contact pressure is insufficient, the insufflation pressure may not be maintained as the surgeon manipulates the instrument. If the contact pressure is too great, however, the surgeon may experience difficulty in advancing and properly controlling the instrument. Because larger instruments must expand the orifice to a greater degree, the contact pressure is consequently larger than for smaller instruments, and thus larger instruments may be more difficult to manipulate than smaller instruments. Accordingly, a need exists for an apparatus for forming a seal about an instrument inserted through a cannula that is capable of accommodating variously sized instruments while ensure a proper contact pressure. 
     SUMMARY 
     The present disclosure describes a surgical portal apparatus which permits a surgical instrument to access a tissue site while maintaining a seal about the instrument. The portal apparatus includes a portal member, which is dimensioned for positioning within body tissue and defines a longitudinal axis. A longitudinal passageway through the portal member provides access to the tissue site. A variable seal member is mounted to the portal member and includes an orifice having a diameter dependent upon a longitudinal dimension of the variable seal member. Each of a pair of compression members is disposed on an opposite longitudinal side of the variable seal member, and each compression member has a pressure face for contacting variable seal member. A longitudinal displacement mechanism in communication with a power source is adapted to produce relative longitudinal motion between the compression members such that the longitudinal dimension of the variable seal is altered to vary the diameter of the orifice. 
     The diameter of the orifice may be dependent upon a Poission&#39;s ratio of a material of the variable seal member. The material may be elastomeric or the material may comprise a viscoelastic gel. The variable seal member may include a flexible casing containing a predetermined quantity of a fluid, and the casing may define a toroidal geometry. An electromagnet may be provided as a component of the longitudinal displacement mechanism. A control feature in communication with the longitudinal displacement mechanism may be included for adjusting the longitudinal dimension of the variable seal to a predetermined value. The control feature may include circuitry responsive to a diameter of an instrument inserted into the longitudinal passageway. A triggering mechanism may be adapted to detect an introduction of an instrument into the longitudinal passageway. 
     In another aspect of the disclosure, a surgical portal apparatus permits a surgical instrument to access a tissue site while maintaining a seal about the instrument. The portal apparatus includes a portal member, which is dimensioned for positioning within body tissue and defines a longitudinal axis. A longitudinal passageway through the portal member provides access to the tissue site. A septum seal member is mounted to the portal member and includes an orifice having a diameter dependent upon a longitudinal dimension of the septum seal member. Each of a pair of compression members is disposed on an opposite longitudinal side of the septum seal member, and each compression member has a pressure face for contacting septum seal member. A longitudinal displacement mechanism is adapted to produce relative longitudinal motion between the compression members such that the longitudinal dimension of the septum seal is altered to vary the diameter of the orifice. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure. 
         FIG. 1  is an exploded perspective view of a surgical portal apparatus in accordance with the present disclosure; 
         FIG. 2A  is a cross sectional view of the portal apparatus of  FIG. 1  illustrating a variable diameter seal in an initial condition for receiving an instrument; 
         FIG. 2B  is a cross sectional view of the portal apparatus illustrating the variable diameter seal in an activated condition for sealing an instrument; 
         FIG. 3A  is a cross sectional view of an alternate embodiment of the surgical portal apparatus illustrating a variable diameter seal in an initial condition; and 
         FIG. 3B  is a cross sectional view of the surgical portal apparatus of  FIG. 3A  illustrating the variable diameter seal in an activated condition. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present disclosure contemplates the introduction into a person&#39;s body of all types of surgical instruments including clip appliers, graspers, dissectors, retractors, staplers, laser fibers, photographic devices, endoscopes and laparoscopes, tubes, and the like. All such objects are referred to herein generally as “instruments.” In the drawings and in the description which follows, the term “proximal,” as is traditional, will refer to the direction toward the operator or a relative position on the surgical device or instrument which is closer to the operator, while the term “distal” will refer to the direction away from the operator or relative position of the instrument which is further from the operator. 
     Referring initially to  FIG. 1 , a surgical portal apparatus according to the present disclosure is depicted generally as  10 . At the proximal end, a cap  12  is open to provide an entryway for an instrument into the portal apparatus  10 . The interior of cap  12  includes a central opening  14  and a radial overhang  16 . Central opening  14  extends through cap  12  and defines a central longitudinal axis “A,” which extends centrally through the surgical portal apparatus  10 . Radial overhang  16  defines a transition in the diameter of central opening  14 , such that central opening  14  is wider distally of radial overhang  16  than proximally of radial overhang  16 . Radial overhang  16  may define a plane orthogonal to axis “A.” Proximal housing  20  is also hollow and open at both ends. An annular ridge  22  provides for a fluid-tight interface with cap  12  and may abut radial overhang  16 . 
     A variable diameter seal  30  is housed within proximal housing  20 , and generally includes a longitudinal displacement mechanism  34 , a proximal compression member  36 , a compressible septum seal  40 , and a distal compression member  44 . Longitudinal displacement mechanism  34  is configured to selectively vary the longitudinal distance between proximal and distal compression members  36 ,  44 . Here, a pair of pneumatic cylinders  46  having extendible pistons  48  are coupled to proximal compression member  36 . Proximal compression member  36  is a generally rigid component having an instrument passage  50  and a distal pressure face  52 , which is adapted for contact with septum seal  40 . 
     Septum seal  40  is a generally planar, washer shaped component having an orifice  56  for engaging an instrument in a fluid-tight, but low-pressure manner. In an uncompressed state as shown, septum seal  40  has a thickness “T” and an inner orifice diameter “D.” When compressed, as discussed below with reference to  FIG. 2B , septum seal  40  assumes a reduced thickness “t,” and, as a consequence, also assumes a reduced orifice diameter “d.” This reduction in orifice diameter permits a fluid tight-interface between septum seal  40  and an instrument inserted through orifice  56 . The materials comprising septum seal  40  may include an elastomeric material such as polyisoprene. Alternatively, septum seal  40  may include a material exhibiting some flow characteristics such as a viscoelastic gel or foam material. 
     Distal compression member  44  is a generally rigid component having an instrument passage  60  and a proximal pressure face  62 . The proximal pressure face  62  of distal compression member  44  opposes the distal pressure face  52  of proximal compression member  36 . Distal compression member  44  and proximal compression member  36  are movable in a longitudinal direction relative to one another such that their respective pressure faces  62 ,  52  may be approximated to compress septum seal  40  and separated to relax septum seal  40 . 
     Seal support  66  is rigidly coupled to proximal housing  20  and provides an interior shelf  68  upon which distal compression member  44  may rest. In some cases, such as the configuration depicted in  FIG. 1 , distal compression member  44  may be incorporated into seal support  66  such that interior shelf  68  serves the function of pressure face  52 . Because it is not required to translate in this embodiment, distal compression member  44  need not be a discrete and distinct component. 
     A circumferential ridge  70  on a distal surface seal support  66  provides a seat for duckbill valve  72 . Duckbill valve  72  is an elastomeric member with a pair of distally extending substantially flat lips  74  which are normally biased together to create a substantial fluid-tight seal through the portal apparatus in the absence of an instrument. Lips  74  may be easily separated upon the insertion of an instrument from the proximal side. The use of other zero-closure valves is also contemplated. 
     Distal housing  78  encloses duckbill valve  72  and forms a fluid-tight connection with proximal housing  20 . On the exterior, distal housing  78  includes diametrically opposed extensions  80  which provide a surface for a surgeon or operator to grip the portal apparatus  10  with two fingers. Distal housing  78  receives cannula  84  and forms a fluid-tight interface therewith. Cannula  84  is a hollow tube open at both ends providing a passageway for an instrument through a small incision made in a patient. A distal end (not shown) of cannula  84  may be positioned in a body cavity adjacent a tissue site, while the proximal end coupled to distal housing  78  remains external to the patient. 
     Referring now to  FIG. 2A , a longitudinal passageway  88  extends through surgical portal apparatus  10 . Only the lips  74  of duckbill valve  72  interrupt passageway  88 , which is otherwise clear to accommodate an instrument. Variable diameter seal  30  is disposed between radial overhang  16  of cap  12  and interior shelf  68  of seal support  66 . Because of the rigid interfaces that connect the cap  12  and seal support  66 , radial overhang  16  remains at a fixed distance from interior shelf  68 . 
     A user interface  90  is depicted schematically on an exterior surface of cap  12  in operative communication with longitudinal displacement mechanism  34 . User interface  90  may include a toggle switch as shown permitting a surgeon or operator to selectively approximate or separate compression members  36 ,  44 . Alternatively, user interface  90  may include a plurality of control surfaces allowing an operator to select appropriate values for variables such as an instrument diameter or desired seal pressure. Also, user interface  90  may be positioned as depicted, or at any other convenient location. 
     Also depicted schematically is power source  96  in communication with longitudinal displacement mechanism  34 . Power source  96  may comprise a supply of compressed air, electrical power or another source of energy for activating longitudinal displacement mechanism  34 . 
     The use of surgical portal apparatus  10  is now described with reference to  FIGS. 2A and 2B . The surgeon may first introduce a shaft  99  of a surgical instrument through cap  12  in a distal direction. The shaft  99  may include the shaft of an obturator of a trocar assembly (not shown) or any general instrument. A surgeon may position a distal end of cannula  84  adjacent a surgical site and establish an insufflation pressure. Duckbill valve  72  prevents insufflation gasses from escaping through the passageway  88  in the absence of an instrument. Shaft  99  may pass freely through orifice  56  of septum seal  40  when it is in an uncompressed condition as in  FIG. 2A . If the surgeon further advances the shaft  99  through the lips  74  of duckbill seal  72 , the seal across passageway  88  will be compromised. The surgeon may therefore wish to establish a seal about shaft  99  with variable diameter seal  30 . 
     The surgeon may manipulate user interface  90  to activate longitudinal displacement mechanism  34 . This results in pistons  48  extending from cylinders  46  and forcing proximal compression member  36  in a distal direction. Pressure faces  52 ,  62  are approximated and septum seal  40  is compressed to a reduced thickness “t” as depicted in  FIG. 2B . The reduction in thickness is indicative of a longitudinal strain in septum seal  40 . For a strained body to remain in equilibrium, the longitudinal strain must be accompanied by an opposite lateral strain in an orthogonal direction. This means that as the thickness “T” of septum seal  40  is reduced to thickness “t,” there is a tendency for a width of septum seal  40  to increase. Because the outer circumference of septum seal  40  is constrained by seal support  66 , this tendency manifests itself in a convergence or flow of the material of septum seal  40  adjacent orifice  56  radially inwardly about shaft  99 , thus forming a seal therewith. 
     With a seal about shaft  99  in place, the surgeon may manipulate tissue at the surgical site. The surgeon will likely make adjustments to the position and orientation of the instrument while in use and the variable diameter seal  30  may be adapted to provide the surgeon with this required flexibility. When the surgeon is finished with the instrument, the instrument shaft  99  may be withdrawn first through duckbill valve  72 . The lips  74  will return to their biased closed position reestablishing the seal across the passageway  88 . 
     The surgeon may then manipulate user interface  90  to cause longitudinal displacement mechanism  34  to separate the pressure faces  52 ,  62 . When the pressure causing the longitudinal strain is relieved, septum seal returns to its original uncompressed condition having thickness “T” and orifice diameter “D.” The portal apparatus  10  is then ready for the process to be repeated with an additional instrument. 
     The use described above presents at least one opportunity to control the contact pressure associated with septum seal  40 . The contact pressure may be controlled by controlling the size of orifice diameter “d” simply by controlling the pressure generated by longitudinal displacement mechanism  34 . For a septum seal  40  formed from a material associate with a given Poisson&#39;s ratio, i.e. the material property defined by the negative ratio of transverse strain to longitudinal strain, orifice diameter “d” decreases with a decreasing strained thickness “t.” Therefore, longitudinal displacement mechanism  34  may be configured to provide a greater pressure for smaller instruments than for larger instruments to provide an appropriate orifice diameter “d” for each instrument. 
     Referring now to  FIGS. 3A and 3B , another embodiment of a surgical portal apparatus in accordance with the disclosure is depicted generally as  100 . Cap  12 , proximal housing  20 , seal support  66 , duckbill valve  72 , distal housing  78  and cannula  84  may all operate identically as described above to provide a sealed passageway to a surgical site. Surgical portal apparatus  100  employs an alternate variable diameter seal  130  may to provide a seal about an instrument. 
     Variable diameter seal  130  includes a longitudinal displacement mechanism comprising an electromagnet  134  contained within proximal compression member  136 . Proximal compression member  136  may be rigidly coupled to cap  12  so that it is stationary with respect to portal assembly  100 . Because it may be stationary in this embodiment, it is not necessary that proximal compression member  136  be a distinct and discrete component. For example, electromagnet  134  may be incorporated into cap  12  such that cap  12  may serve the function of proximal compression member  136 . 
     Seal  140  comprises a flexible casing that may contain a predetermined amount of fluid. The shape of seal  140  may be toroidal such that seal  140  may assume at least a normal unstressed geometry as depicted in  FIG. 3A , or a flattened geometry as depicted in  FIG. 3B . Distal compression member  144  is disposed distally of seal  140  and comprises a magnetic or ferromagnetic material allowing it to be selectively attracted by the electromagnet  134 . An orifice  156  through seal  140  may thus be selectively altered to create a seal about an instrument shaft  99 . 
     Also included in portal apparatus  100  is longitudinal passageway  188 , a triggering mechanism such as sensor  190  and control circuitry  192 . Sensor  190  and control circuitry  192  are in operative communication with one another, and also with electromagnet  134 . Sensor  190  is adapted to detect the presence of an instrument within passageway  188 . Several arrangements are contemplated wherein sensor  190  may also detect the diameter of the instrument present within passageway  188 . 
     A cooperative arrangement is contemplated for sensor  190  where the instrument shaft  99  is specially configured to communicate diameter information. For example, the instrument shaft  99  may contain a passive radio-frequency identification (RFID) tag that responds to queries transmitted by sensor  190  when the RFID tag is in close proximity to the sensor  190 . The RFID tag may respond with an appropriate signal identifying the instrument by diameter. Alternatively, a cooperative arrangement may include a barcode or other size identification markings on the instrument shaft  99  that may be read by an optical sensor  190 . 
     A passive arrangement is also contemplated where the sensor  190  is able to determine the instrument diameter from the physical characteristics of the instrument shaft  99 . For example, a transmitter (not shown), such as an ultrasound transducer or light emitting element, may transmit signals that can be reflected by the instrument shaft  99  upon its entry into passageway  188 . Sensor  190  may be configured to detect the intensity and location of the reflections to determine the instrument diameter. 
     In either a passive or cooperative arrangement, sensor  190  may provide a signal to control circuitry  192  indicating the presence and possibly the size of shaft  99 . Control circuitry  192  is adapted to control the magnitude of the current supplied to electromagnet  134  based on the signal. The magnetic flux density generated by electromagnet  134  is based on the magnitude of the supplied current and dictates the attractive force applied to distal compression member  144 . A power source  196  is included to provide energy to the electromagnet  134  and sensor  190 . 
     In use, a surgeon may insert instrument shaft  99  into the passageway  188  of surgical portal apparatus  100 . The shaft may pass freely through seal  140  in a normal unstressed state as shown in  FIG. 3A . When the shaft  99  is detected by sensor  190 , a signal may be directed to control circuitry  192  indicating the presence and possibly the size of shaft  99 . Control circuitry  190  may process this information and activate electromagnet  134  to the degree necessary to produce a fluid-tight seal about shaft  99  with an appropriate contact pressure. When electromagnet  134  is activated, distal compression member  144  is drawn toward proximal compression member  136  thereby flattening seal  140  and reducing the diameter of orifice  156 . The degree to which orifice  156  is reduced is dependent upon the attractive force generated between proximal and distal compression members  136 ,  144 . Control circuitry  192  may therefore be adapted to supply electromagnet  194  with a greater magnitude of current when a smaller instrument is detected than when a larger instrument is detected. This may produce an appropriate contact pressure for any size shaft  99 . 
     Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.