Patent Publication Number: US-2016220769-A1

Title: Filter cartridge with integrated gaseous seal for multimodal surgical gas delivery system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application in a continuation-in-part of co-pending U.S. application Ser. No. 14/609,952 filed Jan. 30, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention is directed to laparoscopic surgery, and more particularly, to a filter device for a multimodal insufflation system used during laparoscopic surgical procedures. 
     2. Description of Related Art 
     Laparoscopic or “minimally invasive” surgical techniques are becoming commonplace in the performance of procedures such as cholecystectomies, appendectomies, hernia repair and nephrectomies. Benefits of such procedures include reduced trauma to the patient, reduced opportunity for infection, and decreased recovery time. Such procedures within the abdominal (peritoneal) cavity are typically performed through a device known as a trocar or cannula, which facilitates the introduction of laparoscopic instruments into the abdominal cavity of a patient. 
     Additionally, such procedures commonly involve filling or “insufflating” the abdominal (peritoneal) cavity with a pressurized fluid, such as carbon dioxide, to create what is referred to as a pneumoperitoneum. The insufflation can be carried out by a surgical access device (sometimes referred to as a “cannula” or “trocar”) equipped to deliver insufflation fluid, or by a separate insufflation device, such as an insufflation (veress) needle. Introduction of surgical instruments into the pneumoperitoneum without a substantial loss of insufflation gas is desirable, in order to maintain the pneumoperitoneum. 
     During typical laparoscopic procedures, a surgeon makes three to four small incisions, usually no larger than about twelve millimeters each, which are typically made with the surgical access devices themselves, typically using a separate inserter or obturator placed therein. Following insertion, the inserter is removed, and the trocar allows access for instruments to be inserted into the abdominal cavity. Typical trocars often provide means to insufflate the abdominal cavity, so that the surgeon has an open interior space in which to work. 
     The trocar must provide a means to maintain the pressure within the cavity by sealing between the trocar and the surgical instrument being used, while still allowing at least a minimum freedom of movement of the surgical instruments. Such instruments can include, for example, scissors, grasping instruments, and occluding instruments, cauterizing units, cameras, light sources and other surgical instruments. Sealing elements or mechanisms are typically provided on trocars to prevent the escape of insufflation gas. Sealing elements or mechanisms typically include a duckbill-type valve made of a relatively pliable material, to seal around an outer surface of surgical instruments passing through the trocar. 
     SurgiQuest, Inc., Milford, Conn. USA has developed unique surgical access devices that permit ready access to an insufflated surgical cavity without the need for conventional mechanical seals, and it has developed related gas delivery systems for providing sufficient pressure and flow rates to such access devices, as described in whole or in part in U.S. Pat. No. 7,854,724. 
     The present invention relates to a multimodal gas delivery system and related devices for performing multiple surgical gas delivery functions, including insufflation, recirculation and filtration of insufflation fluids and gases. The use of a single multimodal system reduces operating costs by requiring the purchase of only one system while achieving multiple functions, and also thereby reduces the amount of equipment needed in an operating room, thus reducing clutter and allowing space for other necessary equipment. 
     SUMMARY OF THE INVENTION 
     The subject invention is directed to a new and useful system for delivering gas during a laparoscopic surgical procedure performed within a patient&#39;s abdominal cavity. The system includes, among other things, a gas delivery device having a housing with a port for receiving insufflating gas from a gas source. The gas delivery device includes a pump assembly for circulating pressurized gas throughout the system. The system further includes a disposable gas conditioning unit or cartridge configured for operative association with the gas delivery device. 
     The gas conditioning unit includes a first internal flow path for delivering pressurized gas delivered from the pump to an internal nozzle assembly configured to accelerate the pressurized gas and thereby generate a continuous pressure barrier contained within the gas conditioning unit that inhibits egress of insufflation gas from the abdominal cavity. The gas conditioning unit further includes a second internal flow path for delivering insufflation gas to the abdominal cavity and for facilitating periodic static pressure measurements from the abdominal cavity, and a third internal flow path for returning depressurized gas spent by the internal nozzle assembly back to the pump under vacuum. 
     The gas conditioning unit includes a generally cylindrical housing having a front end and an opposed rear end. The gas delivery unit includes an engagement port for detachably receiving the rear end of the gas conditioning unit. The rear end of the gas conditioning unit includes a rear cover having a first rear flow port corresponding to the first internal flow path, a second rear flow port corresponding to the second internal flow path, and a third rear flow port corresponding to the third internal flow path. The front end of the gas conditioning unit includes a front cover having a first front flow port corresponding to the first internal flow path which communicates with a first conduit, and a second front flow port corresponding to the second internal flow path which communicates with a second conduit. 
     The housing of the gas conditioning unit includes a pressure chamber located within the first internal flow path and communicating with the first rear flow port. The housing of the gas conditioning unit further includes a central nozzle chamber having a cylindrical wall supporting the annular nozzle assembly. The central nozzle chamber communicates with the pressure chamber through an internal delivery port. 
     The annular nozzle assembly includes a cylindrical jet set having a pair of axially spaced apart outer sealing rings for sealingly isolating the nozzle assembly within the central nozzle chamber. The central nozzle chamber includes a plurality of circumferentially disposed spaced apart axial fins distal to the cylindrical jet set for directing gas flow. The central nozzle chamber communicates with a breathing tube proximal to the cylindrical jet set that is open to atmosphere. 
     A first filter element is disposed within the pressure chamber for filtering pressurized gas from the pump. The housing of the gas conditioning unit includes a diverter plate which interacts with the rear cover to define a conditioning cavity disposed in the second internal flow path and configured to support a second filter element for filtering insufflation gas from the gas source. The housing of the gas conditioning unit also includes a vacuum chamber located within the third internal flow path. 
     The vacuum chamber communicates with the nozzle chamber through a plurality of gas transfer ports to permit spent gas from the nozzle assembly to return to the pump for repressurization and circulation. A third filter element is disposed within the vacuum chamber for filtering depressurized gas returning to the pump. 
     The housing of the gas conditioning unit further includes a reservoir chamber located within the third internal flow path, downstream from and in fluid communication with the vacuum chamber through a fluid transfer port, for accommodating any fluid drawn into the housing of the gas conditioning unit by the pump. A fluid level sensor is arranged within the reservoir for detecting a predetermined fluid level therein. 
     The first conduit includes a fitting for communicating with a first surgical access port, and wherein the first access port includes a mechanical valve associated with a central lumen thereof for accommodating the introduction of surgical instruments into the abdominal cavity. The second conduit includes a fitting for communicating with a second surgical access port responsible for insufflation and pressure measurement of the abdominal cavity. 
     The subject invention is also directed to a gas conditioning unit for use with a gas delivery device during a laparoscopic surgical procedure performed within a patient&#39;s abdominal cavity. The unit includes, among other things, a housing having a rear end configured for engagement with the gas delivery device and an opposed front end, a first filtered flow path within the housing for delivering pressurized gas delivered from the pump to an internal nozzle assembly configured to accelerate the pressurized gas and thereby generate a continuous pressure barrier contained within the gas conditioning unit that inhibits egress of insufflation gas from the abdominal cavity, a second internal flow path for delivering insufflation gas to the abdominal cavity and for facilitating periodic static pressure measurements from the abdominal cavity, and a third internal flow path for returning depressurized gas spent by the internal nozzle assembly back to the pump under vacuum. 
     These and other features of the surgical gas delivery system and the gas conditioning device of the subject invention and the manner in which both are manufactured and employed will become more readily apparent to those having ordinary skill in the art from the following enabling description of the preferred embodiments of the subject invention taken in conjunction with the several drawings described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is an illustration of the operating environment in which the gas delivery system of the subject invention is employed during a laparoscopic surgical procedure, which includes, among other things, a gas delivery device having a housing with a port for receiving pressurized insufflation gas from a gas source, and a separate gas conditioning unit configured for operative association with the gas delivery device; 
         FIG. 2  is a perspective view of the gas delivery device and separate gas conditioning unit illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view of the gas conditioning unit of the subject invention as viewed from the front end of the unit, illustrating the two conduits extending therefrom; 
         FIG. 4  is a perspective view of the gas conditioning unit of the subject invention as viewed from the rear end of unit, illustrating the three flow ports thereof; 
         FIG. 5  is an exploded perspective view of the gas conditioning unit of the subject invention, with parts separated for ease of illustration; 
         FIG. 6  is an exploded perspective view of the annular jet rings which form the internal nozzle assembly of the gas conditioning unit shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional perspective view of the gas conditioning unit of the subject invention taken along line  7 - 7  of  FIG. 3 , illustrating the location of the filter elements within the housing of the filter unit; 
         FIG. 8  is a cross-sectional perspective view of the gas conditioning unit of the subject invention, taken along line  8 - 8  of  FIG. 3 , illustrating the internal features of the vacuum chamber within the housing of the filter unit; 
         FIG. 9  is a cross-sectional view of the gas conditioning unit of the subject invention, with a wall broken away to show the liquid level sensing prisms in the reservoir; 
         FIG. 10  is a cross-sectional view of the gas conditioning unit of the subject invention with a wall broken away to illustrate the insufflation and sensing path layout within the housing; 
         FIG. 11  is a cross-sectional view of the gas conditioning unit of the subject invention with a wall broken away to illustrate the pressure path layout within the housing; 
         FIG. 12  is a localized cross-sectional view of the central nozzle chamber within the housing; and 
         FIG. 13  is a cross-sectional view of the gas conditioning unit of the subject invention with a wall broken away to illustrate the vacuum path layout within the housing. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention, there is illustrated in  FIGS. 1 and 2 , a new and useful system for delivering and circulating medical gas (e.g., carbon dioxide) during a laparoscopic surgical procedure performed within a patient&#39;s abdominal cavity. 
     The gas delivery system, which is designated generally by reference numeral  10  includes, among other things, a gas delivery device  12  having a housing  14  with a rear connector or port  16  for receiving pressurized insufflation gas from a gas source  18 . As shown, the gas source  18  is a portable supply canister. However, it is envisioned that the medical or insufflating gas could be supplied from another source, including for example, a remote storage tank (e.g., house gas) as is well known in the art. A pump assembly  20  is enclosed within the housing  14  of delivery device  12  for circulating pressurized gas throughout the system  10  to maintain a stable pneumo-peritoneum during a surgical procedure. 
     A graphical user interface  25  with associated control circuitry is provided within the housing  14  of gas delivery device  12  for controlling the operation of the pump assembly  20 , as well as the delivery of insufflating gas from supply source  18 . The interface and associated circuitry enables a user to readily adjust flow rates and supply pressures relating to the delivery, circulation and recirculation of gas and fluid throughout the system. 
     The gas delivery system  10  further includes a separate and preferably disposable gas conditioning unit  30 , which is dimensioned and configured for operative association with the gas delivery device  12 . As described in more detail below, the gas conditioning unit  30  is constructed in such a manner so that a continuous gaseous pressure barrier is generated within the housing of the unit itself, remote from the patient. This gaseous pressure barrier or working zone prevents the egress of insufflation gas from the abdominal cavity of the patient while maintaining a stable pneumoperitoneum within the abdominal cavity. This feature differs from the multi-modal gas delivery systems disclosed in commonly assigned U.S. Pat. No. 7,854,724, wherein the gaseous pressure barrier is generated within the housing of a specialized trocar at the surgical site. 
     The gas conditioning unit  30  includes a number of internal flow paths configured to facilitate the periodic delivery of insufflating gas, as well as the continuous circulation and recirculation of pressurized gas. In particular, a first internal flow path (i.e., the pressure path shown in  FIG. 11 ) is provided for receiving pressurized gas from the pump assembly  20  of the gas delivery device  12 . The first internal flow path is associated with a first conduit  32  that is connected to a first surgical access device or trocar  34 . The trocar  34  is the primary path for introducing surgical instrumentation into the abdominal cavity during a surgical procedure, and it has a mechanical seal installed therein. The pressurized gas is used to create a pressure barrier within the gas conditioning unit  30  that prevents the egress of gas from the abdominal cavity by way of conduit  32 . In doing so, it also maintains a stable pneumoperitoneum within the abdominal cavity of the patient  15 . 
     The gas conditioning unit  30  further includes a second internal flow path (i.e., the sense/insufflation path shown in  FIG. 10 ) for delivering insufflating gas from the gas delivery device  12  to the abdominal cavity of the patient  15  and for facilitating periodic static pressure measurements from the abdominal cavity by way of a second conduit  40  connected to a second surgical access device or cannula  42 . The duration of the insufflation interval between pressure measurements can vary, depending upon the patient and the operating environment. This flow and stop methodology for obtaining static pressure measurements from the abdominal cavity is well known in the art. 
     The gas conditioning unit  30  also includes a third internal flow path (i.e., the vacuum path shown in  FIG. 13 ) for returning pressurized gas to the pump assembly  20  of the gas delivery device  12 . The gas returned to the pump assembly  20  is the spent pressurized gas that was used to create the pressure barrier within the conditioning unit  30 . 
     With continuing reference to  FIG. 2 , the gas conditioning unit  30  is adapted and configured for ready installation into and removal from the housing  14  of gas delivery device  12  by way of a interfitting lug arrangement. More particularly, as best seen in  FIGS. 3 and 4 , the generally cylindrical housing  50  of gas conditioning unit  30  includes a plurality of circumferentially spaced apart engagement lugs, including an L-shaped lug  52  and a square-shaped lug  54 . A third lug  56  can be seen in  FIG. 8 . The three engagement lugs  52 ,  54  and  56  are dimensioned and configured to interact with correspondingly shaped and positioned recesses  62 ,  64  and  66  defined in the periphery of the cartridge engagement port  60  formed in the front panel of housing  14 , as shown in  FIG. 2 . 
     With continuing reference to  FIGS. 3 and 4 , the housing  50  of gas conditioning unit  30  includes a front end cap or cover  70  and a rear end cap or cover  90 . The front end cap  70  has two conduit connection tubes associated therewith. These include a first or central conduit connection tube  72  that extends through an aperture  75  in the front end cap  70  and is operatively associated with the first conduit  32 , shown in  FIGS. 1 and 2 . Front end cap  70  also includes a second conduit connection tube  80  operatively associated with the second conduit  40 , which are also shown in  FIGS. 1 and 2 . 
     Referring to  FIG. 4 , the rear end cap  90  includes three outlet ports, each having an associated sealing ring. The first outlet port  92  communicates with the first internal flow path (i.e., the pressure path shown in  FIG. 11 ) and ultimately with tube  72 . The second outlet port  94  communicates with the second internal flow path (i.e., the sense/insufflation path shown in  FIG. 10 ) and ultimately with tube  80 . The third outlet port  96  communicates with the third internal flow path (i.e., the vacuum path shown in  FIG. 13 ). 
     The first outlet port  92  includes a first O-ring seal  102 , the second outlet port  94  includes a second O-ring seal  104  and the third outlet port  96  includes a third O-ring seal  106 . The three O-rings seals  102 ,  104  and  106  are seated and arranged in a co-planar manner on the rear end cap  90  to cooperate with corresponding features within the cartridge engagement port  60  in the front panel of housing  14 . 
     A similar co-planar arrangement of O-ring seals is disclosed in commonly assigned U.S. Patent Application Publication 2012/0138523, which is incorporated herein by reference in its entirety. In addition, the rear end cap  90  includes a central exhaust port  108 , which permits the entrainment of air into the recirculation flow under certain operating conditions. This will be described in more detail hereinbelow. 
     Referring now to  FIG. 5 , there is illustrated the gas conditioning unit  30  with each of the components parts thereof separated from the cylindrical housing  50  for ease of illustration. Also shown are certain internal features of the housing  50  of conditioning unit  30 . Starting there, the housing  50  includes several internal cavities for supporting components and/or defining gas/fluid flow passages. At the front end of housing  50 , there is a vacuum chamber  110 , which is located within the third internal flow path (i.e., the vacuum path shown in  FIG. 13 ). 
     The vacuum chamber  110  is dimensioned and configured to support a cylindrical pleated filter element  120  (see also  FIG. 7 ). The pleated filter element  120  is preferably made from a porous non-woven or melt-blown filter media fabricated from a plastic material such as polypropylene or the like. Filter element  120  has an offset bore  122  to accommodate the passage of the central conduit connection tube  72  therethrough, when the unit  30  is fully assembled. 
     As best seen in  FIGS. 7 and 9 , the housing  50  of gas conditioning unit  30  further includes a reservoir chamber  130 , which is also located within the third internal flow path, downstream from and in fluid communication with the vacuum chamber  110 . More particularly, the reservoir chamber  130  communicates with the vacuum chamber  110  through a fluid transfer port  132  formed in the internal wall  135  of housing  50 . Any fluid or debris accidentally drawn into the housing  50  of the gas conditioning 30 unit (e.g., through conduit  32 ) by the suction of pump  20  in gas delivery device  12  accumulates first within the vacuum chamber  110  until it reaches the level of the transfer port  132 , whereupon such fluid enters into the reservoir chamber  130 . 
     Referring to  FIG. 9 , prism shaped fluid level sensors  134  and  136  are arranged within the reservoir chamber  130  for detecting a predetermined fluid level therein. The structure and function of the fluid level sensors  134 ,  136 , and the alarm set points and circuitry associated therewith is described in greater detail in commonly assigned U.S. Patent Application Publication 2013/0231606, the disclosure of which is herein incorporated by reference in its entirety. 
     With continuing reference to  FIG. 5  in conjunction with  FIGS. 7 and 9 , the housing  50  of gas conditioning unit  30  further includes a pressure chamber  140  located within the first internal flow path (i.e., the pressure path shown in  FIG. 11 ). Pressure chamber  140  is dimensioned and configured to support a cylindrical pleated filter element  150  (see also  FIG. 7 ). Pleated filter element  150  is preferably made from a porous non-woven or melt-blown filter media fabricated from a plastic material such as polypropylene or the like. 
     Filter element  150  has a central bore  152  to accommodate, among other components, a cylindrical breathing tube  165 . Breathing tube  165  communicates with the central breathing port  108  in the rear end cap  90  to facilitate the entrainment of ambient air into the system under certain operating conditions. As best seen in  FIGS. 5 and 7 , an annular barrier wall  160  separates and fluidly isolates the reservoir chamber  130  from the pressure chamber  140 . The barrier wall  160  is seated on an annular ledge  162  formed in the inner wall of the housing  50 . 
     The housing  50  of gas conditioning unit  30  also includes a central nozzle chamber  170  defined primarily by a cylindrical wall  172 , which is surrounded by pleated filter  150 . The central nozzle chamber  170  communicates with the pressure chamber  140  through an internal delivery port  174  (see  FIGS. 5 and 11 ). The central nozzle chamber  170  supports a two-part annular nozzle assembly  180 , which is shown in a separated condition in  FIG. 6 . The annular nozzle assembly  180  is described in greater detail in commonly assigned U.S. Pat. No. 8,795,223, which is herein incorporated by reference in its entirety. 
     In general, the annular nozzle assembly  180  includes upper and lower ring jet components  182  and  184 , which are connected to one another by a set of circumferentially spaced apart cooperating lugs  182   a - 182   d  and  184   a - 184   d . The upper ring jet component  182  includes a central tubular portion  183  having a set of circumferentially spaced apart recessed areas  185  forming a set of spaced apart land areas  187 . The lower ring jet component  184  includes a continuous seating surface  189  for intimately receiving the tubular portion  183  of upper ring jet component  182 . 
     When the two ring jet components  182 ,  184  are interfit together, an annular nozzle is formed between the land areas  187  of the tubular portion  183  and the continuous seating surface  189 . When pressurized air is delivered from the pressure chamber  140 , through the delivery port  174 , into the nozzle chamber  170 , and then through the nozzle  180  formed by the intimate engagement of the tubular portion  183  and the continuous seating surface  189 , a pressure barrier or working zone is created within the housing  50  of conditioning unit  30  to prevent the egress of insufflation gas from the abdominal cavity of a patient by way of conduit  32 . This is best seen in  FIG. 12 . 
     The annular nozzle assembly  180  further includes a pair of axially spaced apart outer sealing rings  186   a ,  186   b  for sealingly isolating the nozzle assembly  180  within the central nozzle chamber  170 , as best seen in  FIG. 7 . The central nozzle chamber  170  of housing  50  includes a chamber extension member  175  that has a proximal funnel portion  177  and a distal tubular portion  179 . The funnel portion  177  has a plurality of circumferentially disposed spaced apart axial vanes or fins  190  located distal to the cylindrical jet set  182 ,  184 . The vanes  190  are adapted and configured to direct the flow of spent gas (i.e., pressurized gas that has lost its momentum after being delivered from the jet set nozzle assembly  180 ) away from the working zone. The distal portion  179  extends downwardly from the nozzle chamber  170  to a reduced distal section  179   a  that accommodates conduit  32 . 
     The central nozzle chamber  170  communicates with the breathing tube  165 , which is located proximal to the nozzle assembly  180 . The breathing tube  165  is open to atmosphere and permits the entrainment of air into the recirculation flow of the gas delivery system under certain operating conditions. The breathing tube  165  includes a base portion  167  that forms an end cap for the nozzle chamber  170 . 
     Referring to  FIGS. 8 and 9 , the vacuum chamber  110  communicates with central nozzle chamber  170  through a plurality of circumferentially spaced apart gas transfer ports  192  which permit spent gas from the nozzle assembly  180  to return to the pump  20  for repressurization and circulation, as explained in more detail below. This is caused by suction created by pump  20 . The gas transfer ports  192  are defined about the periphery of the funnel portion  177  of chamber extension member  175 . 
     Referring once again to  FIG. 5 , the housing  50  of the gas conditioning unit  30  also includes a diverter plate  210  which interacts with the outlet cover  90  to define, among other features, a conditioning cavity  212  therebetween. The conditioning cavity  212  forms part of the second internal flow path, communicates with port  94  in end cap  90 , and is configured to support a planar filter element  220  made from a non-woven mesh or the like for filtering insufflation gas delivered from the gas source  18 . Diverter plate  210  also includes a central aperture  215  to accommodate the passage of breathing tube  165 . 
     Referring now to  FIG. 10 , during operation, insufflation gas is delivered from the gas source  18  into the conditioning cavity  212  through the port  94  in the rear end cap  90 . The gas is conditioned or otherwise filtered as it passes through planar filter element  220 . The filtered gas exists the conditioning cavity  212  through the crescent shaped side aperture  214  in diverter plate  210  and then flows into the internal side flow passage  216  of housing  50 . The insufflating gas then exits from the housing  50  by way of conduit tube  80  in the front end cap  70  for delivery to the patient  15  through flexible conduit  40 . 
     This same pathway shown in  FIG. 10  is used to periodically sense abdominal pressure. That is, the flow of insufflation gas from gas source  18  is intermittently turned off by a valve (not shown) located in the housing  14  of gas delivery device  12 . As a result, there are intervals of time in which there is no flow through the sensing path (e.g. through path  216  in housing  50 ). At such times, static pressure within the abdominal cavity can be measured by the gas delivery device  12  by way of conduit  40 . This pressure measurement is utilized to adjust the flow of gas to the abdominal cavity, for example. 
     Referring now to  FIG. 11 , during operation, pressurized gas is delivered from the pump  20  in gas delivery device  12  through the port  92  in the rear end cap  90 . The pressurized gas then passes through the centrally offset circular aperture  218  in diverter plate  210  and then into the pressure chamber  140 , where it is conditioned or otherwise filtered by passing through pleated filter element  150 . 
     The pressurized gas then travels to the central nozzle chamber  170  by way of internal delivery port  174 . In the central nozzle chamber  170 , the pressurized gas is directed through the nozzle assembly  180  where it forms a pressure barrier within the upper region of central tubular passage  280  of tubular portion  179  that is operatively associated with the conduit tube  72 , as best seen in  FIG. 12 . This pressure barrier or working zone prohibits the egress of insufflation gas coming up from the abdominal cavity through flexible conduit  32  and conduit tube  72 , while maintaining a stable pneumoperitoneum within the abdominal cavity of the patient  15 . 
     Referring to  FIG. 13 , during operation, the suction from pump assembly  20  draws the spent fluid/gas that had been used to develop the pressure barrier within the conditioning unit through the plural apertures  192  of the nozzle chamber  170 . That spent fluid/gas enters into the vacuum chamber  110 , flows through the side port  282  and into the lateral flow path  284 . The spent fluid/gas then exits the housing  50  through exit port  96  and returns to pump  20 . The conditioned flow is repressurized by the pump  20  and recirculated back to the housing  50  through pressure aperture  92  for subsequent delivery to the nozzle assembly  180  in nozzle chamber  170 . 
     While the gas delivery device and associated gas conditioning unit of the subject invention have been shown and described with reference to a preferred embodiment, those skilled in the art will readily appreciate that various changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention as defined by the appended claims. For example, the locations and relative positions of each of the gas flow paths formed within the conditioning unit could vary, and the type and size of the filter elements used within the conditioning unit could also vary.