Patent Publication Number: US-11033299-B2

Title: Multimodal surgical gas delivery system having continuous pressure monitoring of a continuous flow of gas to a body cavity

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The subject application claims the benefit of priority to U.S. Provisional patent application Ser. No. 62/421,480 filed Nov. 14, 2016, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention relates to surgical gas delivery systems, and more particularly, to multimodal gas delivery systems for surgical insufflation, smoke evacuation and/or recirculation, which is also configured for continuous pressure monitoring of a continuous flow of gas to a body cavity. 
     2. Background of the Related Art 
     Minimally invasive surgical techniques such as endoscopic and laparoscopic surgical procedures have become increasingly common. Benefits of such procedures include reduced trauma to the patient, reduced opportunity for infection and decreased recovery time. Laparoscopic surgical procedures within the abdominal (peritoneal) cavity are typically performed through a device known as a trocar or cannula, which facilitates the introduction of surgical 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 way of 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, often 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 provide a way to insufflate the abdominal cavity, so that the surgeon has an open interior space in which to operate and work. 
     The trocar must maintain the pressure within the abdominal cavity by providing a seal between the trocar and any surgical instrument being passed therethrough, 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 within trocars to prevent the escape of insufflation gas. These 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. 
     Surgical access devices or trocars that permit sealed access to an insufflated surgical cavity without the need for conventional mechanical seals are known in the art. These devices are adapted and configured to provide sealable access to a surgical cavity through the use of a pneumatic or gaseous seal generated and maintained by a circulating flow of pressurized insufflation gas. Such devices are described in U.S. Pat. Nos. 7,854,724 and 8,795,223, the disclosures of which are herein incorporated by reference in their entireties. Also known in the art are multimodal surgical gas delivery systems that are used in conjunction with such pneumatically sealed trocars for delivering insufflation gas to a body cavity, for circulating surgical gas through the trocar to generate and maintain the pneumatic seal and for facilitating smoke evacuation from the body cavity. 
     Use of a multimodal system helps to reduce costs by requiring 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. Such systems are described for example in U.S. Pat. Nos. 8,715,219 and 8,961,451 as well as in U.S. Pat. Nos. 9,295,490 and 9,375,539, the disclosures of which are all herein incorporated by reference in their entireties. 
     In certain applications, it is advantageous to monitor pressure at body cavity, for example, the abdominal cavity, in real time during insufflation. Real time pressure monitoring helps to better detect and respond to changes in pressure at surgical site within the body cavity. Conventional methods of continuously monitoring surgical cavity pressure, such as the one disclosed in U.S. Pat. No. 6,299,592, separate insufflation and pressure monitoring, requiring a dedicated pressure sensing lumen, port, or connection to the body cavity. 
     The systems described herein do not require a dedicated pressure sensing lumen or connection, and instead, utilize the consistent flow of new or recirculated insufflation gas being provided to the surgical cavity. Furthermore, because it is not necessary to stop the flow of new insufflation gas to the surgical cavity to sense pressure, the systems disclosed herein provide improved smoke removal by recirculating gas through a pneumatically sealed access device. 
     SUMMARY OF THE INVENTION 
     The subject invention is directed to a new and useful system for delivering insufflation gas to a body cavity of a patient during an endoscopic or laparoscopic surgical procedure. In one embodiment of the invention, the system includes an insufflation conduit for delivering a continuous flow of insufflation gas to the body cavity of a patient at a variable flow rate through a flow path that communicates with a pneumatically sealed trocar which prevents over-pressurization of the body cavity, and an insufflator for driving gas flow through the insufflation conduit at a given driving pressure, wherein the gas flow rate through the insufflation conduit will vary depending upon body cavity pressure. This system further includes a flow meter communicating with the insufflation conduit and located between the insufflator and the body cavity for continuously measuring gas flow through the insufflation conduit, and a processor for determining a body cavity pressure corresponding to a given driving pressure based upon a gas flow measurement from the flow meter. 
     Preferably, the processor relies upon data stored in memory in a look up table based upon a known resistance characteristic of the flow path, and it utilizes a calibration algorithm to determine the resistance characteristic of the flow path when it is initially unknown. The system further includes a pressure sensor located along the flow path for taking periodic static pressure measurements and associating those static pressure measurements with periodic flow measurements. 
     In another embodiment of the subject invention, the system includes an insufflation conduit for delivering a continuous flow of insufflation gas to the body cavity of a patient at a specified flow rate through a flow path that communicates with a pneumatically sealed trocar which prevents over-pressurization of the body cavity, and an insufflator for driving gas flow through the insufflation conduit at a variable driving pressure, wherein the driving pressure required to maintain the specified flow rate will vary depending upon body cavity pressure. This system further includes a driving pressure sensor communicating with the insufflation conduit and located between the insufflator and the body cavity for continuously measuring variable driving pressure in the insufflation conduit, and a processor for determining an amount of driving pressure required to maintain the specified flow rate of insufflation gas to the body cavity through the flow path. The processor is also configured to determine a body cavity pressure corresponding to a given gas flow rate based upon a driving pressure measurement from the driving pressure sensor. 
     The processor relies upon data stored in memory in a look up table based upon a known resistance characteristic of the flow path, and it utilizes a calibration algorithm to determine the resistance characteristic of the flow path when it is initially unknown. The system further includes a flow meter that provides feedback to the insufflator so that the insufflator can maintain the specified flow to the body cavity. The system also includes a second pressure sensor located along the flow path for taking periodic static pressure measurements and associating those static pressure measurements with periodic driving pressure measurements. 
     In another embodiment of the invention, the system includes an insufflation conduit for delivering a continuous flow of insufflation gas to the body cavity at a flow rate through a flow path that communicates with a pneumatically sealed trocar which prevents over-pressurization of the body cavity, and an insufflator for driving gas flow through the insufflation conduit at a driving pressure, wherein the system can be configured so that either the gas flow rate through the insufflation conduit or the driving pressure required to maintain the specified flow rate can vary depending upon body cavity pressure. 
     When the system is configured so that the gas flow rate through the insufflation conduit varies depending upon body cavity pressure, the flow rate of the insufflation gas will be variable and the driving pressure of the insufflation gas will be specified. When system is configured so that the driving pressure that is required to maintain the specified flow rate varies depending upon body cavity pressure, the flow rate of the insufflation gas will be specified and the driving pressure of the insufflation gas will be variable. 
     These and other features of the multimodal gas delivery system of the subject invention 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 having ordinary skill in the art will readily understand how to make and use the gas delivery systems and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to the figures wherein: 
         FIG. 1  is a schematic illustration of a multimodal surgical gas delivery system constructed in accordance with an embodiment of the subject invention which is configured for continuous pressure monitoring of a continuous flow of gas to a body cavity; 
         FIG. 2  is a schematic flow diagram of a computing environment that forms part of the multimodal surgical gas delivery system of  FIG. 1 ; 
         FIG. 3  is a schematic illustration of a multimodal surgical gas delivery system constructed in accordance with another embodiment of the subject invention which is configured for continuous pressure monitoring of a continuous flow of gas to a body cavity; 
         FIG. 4  is a graphical illustration of a look up table for insufflation gas delivered by the multimodal gas delivery system of the subject invention at a variable flow and a specified driving pressure of 60 mmHg; and 
         FIG. 5  is a graphical illustration of a look up table for insufflation gas delivered by the multimodal gas delivery system of the subject invention at a specified flow of 3 L/min and a variable driving pressure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring now to the drawings, wherein like reference numerals identify similar structural elements or features of the subject invention, there is illustrated in  FIG. 1  a multimodal surgical gas delivery system constructed in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral  100 . As described in more detail below, the gas delivery system  100  is designed for multimodal operation to facilitate insufflation of a body cavity, smoke evacuation from the body cavity and/or gas recirculation through an access port communicating with the body cavity. In addition, the surgical gas delivery system  100  is configured to maintain body cavity pressure when suction is used within the body cavity during a surgical procedure to remove solid debris, liquids and gases from the body cavity. 
     As shown in  FIG. 1 , the gas delivery system  100  is adapted to function with three surgical access devices or trocars ( 131 ,  133 ,  135 ) that are in communication with a patient&#39;s body cavity  190 . It is envisioned that gas delivery system  100  can also be used with two surgical access devices or trocars, as disclosed for example in commonly assigned U.S. Pat. No. 9,375,539. Alternatively, the system can be employed with a single surgical access device as disclosed for example in commonly assigned U.S. Pat. No. 9,295,490. 
     The multimodal gas delivery system  100  includes a computer-controlled control unit  110  which is driven by a general purpose computing system that is best seen in  FIG. 2 . It is to be understood and appreciated that the computing system facilitates the selective modes of operation of multimodal gas delivery system  100 . 
     Referring to  FIG. 2 , the computing system  10  of control unit  110  includes at least one processor  12 , a memory  14 , at least one input device  16  and at least one output device  18 , which are all coupled together via a bus  11 . The storage device  14  can be any form of data or information storage means, for example, volatile or non-volatile memory, solid state storage devices or magnetic devices. 
     In certain embodiments of the invention, input device  16  and output device  18  could be the same device. An interface  15  can also be provided for coupling the computing system  10  to one or more peripheral devices. For example interface  15  could be a PCI card or PC card. The memory or storage device  14  can house or maintain at least one database  17 . The memory  14  can be any form of memory device, for example, volatile or non-volatile memory, solid state storage devices, or magnetic devices. 
     Input device  16  receives input data  19  and can comprise, for example, a keyboard, a pointer device such as a pen-like device, a mouse, a touch screen, or any other suitable device, such as a modem or wireless data adaptor, or data acquisition card. Input data  19  could come from different sources, for example keyboard instructions in conjunction with data received via a network. 
     Output device  18  produces or generates output data  20  and can comprise, for example, a display device or monitor in which case output data  20  is visual. Output data  20  could be distinct and derived from different output devices, for example a visual display on a monitor in conjunction with data transmitted to a network. A user could view data output, or an interpretation of the data output, on, for example, a monitor or using a printer. 
     In use, the computing system  10  is adapted to allow data or information to be stored in and/or retrieved from, via wired or wireless communication means, at least one database  17  stored in memory  14 . The interface  15  may allow wired and/or wireless communication between the processing unit  12  and peripheral components that may serve a specialized purpose. 
     Preferably, the processor  12  receives instructions as input data  19  via input device  16  and can display processed results or other output to a user by utilizing output device  18 . More than one input device  16  and/or output device  18  can be provided. It should be appreciated that the computing system  10  may be in any form, but it is preferably provided integral with the control unit  110  of surgical gas delivery system  100 . 
     It is to be appreciated that the computing system  10  may be a part of a networked communications system. Computing system  10  could connect to a network, for example the Internet or a WAN. Input data  19  and output data  20  could be communicated to other devices via the network. The transfer of information or data over the network can be achieved using wired communications means or wireless communications means. A server can facilitate the transfer of data between the network and one or more databases. A server and one or more databases provide an example of an information source. 
     Thus, the computing system  10  may operate in a networked environment using logical connections to one or more remote computers. The remote computer may be a personal computer, a server, a router, a network PC, a tablet device, a peer device, or other common network node, and typically includes many or all of the elements described above. 
     Referring once again to  FIG. 1 , the multimodal surgical gas delivery system  100  includes a fluid pump  111  that is adapted and configured to circulate pressurized insufflation fluid through the system  100 . A supply conduit  114  is in fluid communication with an output of the fluid pump  111  and it is configured and adapted for delivering pressurized insufflation fluid to an output port  183  of the control unit  110 . 
     A return conduit  112  is in fluid communication with an input of the fluid pump  111  for delivering insufflation fluid to the fluid pump  111 , and it is configured and adapted for returning insufflation fluid to an input port  181  of the control unit  110 . An adjustable back-pressure control valve  113  is provided in fluid communication with the supply conduit  114  and the return conduit  112 , and is adapted and configured to respond to a supply conduit pressure exceeding a set pressure, by opening and directing fluid from the supply conduit  114  to the return conduit  112 . The back-pressure control valve  113  can be a mechanical valve, such as a resiliently-biased valve. Alternatively, the back-pressure control valve  113  can be an electro-mechanical valve, responding to a high pressure signal from one or more pressure sensors (e.g.  117 ) within the system  100 . 
     An insufflation subunit  121  is provided and it is adapted and configured to receive a supply of insufflation gas (e.g., carbon dioxide) from a source  140  such as a local tank as shown or from a central distribution system, which may also pass through a pressure regulator  141  prior to entering the gas delivery system  100 . The insufflation subunit  121  delivers insufflation gas to the rest of the system  100  through an insufflation conduit  118 . The insufflation subunit  121  includes an internal pressure sensor (not shown) that senses the pressure of surgical cavity  190  through the insufflation conduit  118 . 
     The gas delivery system  100  is operated or otherwise controlled by a user through a control panel, such as one provided on or otherwise in connection with the control unit  110 . Such a control panel is preferably adapted and configured to permit a user to select a mode for the multimodal surgical gas delivery system, such as by way of a switch, touch screen or other user interface. For example a graphical user interface (GUI) can be provided that permits the selection of an operating mode as well as the operational parameters for a particular mode. It is to be understood and appreciated that the control panel may be provided integral with the system  100  or it can be remotely located therefrom using known means of data communication. 
     Operating modes can include, but are not limited to, insufflation, smoke evacuation, combined smoke evacuation and insufflation, recirculation, or combined recirculation and smoke evacuation. Operating parameters for a mode can include, for example, flow rate (e.g., liters/minute), pressure (e.g., mmHg), and conditioning parameters (e.g., temperature and humidity), and the like. 
     As used herein, the “recirculation” mode, alone or combined with other modes, is one that is suitable for providing sufficient operating pressures and flow rates to drive pneumatically sealed surgical access devices such as those described in commonly assigned U.S. Pat. Nos. 7,854,724 and 8,795,223, incorporated herein by reference. 
     A tube set  150  is also provided and it is adapted and configured to connect at one end to the supply conduit  114 , return conduit  112  and insufflation conduit  118 , and at the opposing end to a plurality of surgical access devices  131 ,  133 ,  135 , which are in fluid communication with the surgical cavity  190 . The configuration of the tube set  150  can vary, depending on the desired implementation, as mentioned above. In the case of the system  100 , the tube set  150  preferably has a unitary, multi-lumen connection to input  181 , output  183  and insufflation  185  ports, and separate connections to the individual surgical devices  131 ,  133 ,  135 . It is envisioned that the tube set  150  can have a compound, multi-lumen tube, beginning at the connections to the ports  181 ,  183 ,  185  for a predetermined distance from the control unit  110 , and at an intermediate point a furcation  155  yields multiple separate tubes. In the case of the system  100 , three separate tubes, separately lead to each of the surgical devices  131 ,  133 ,  135 , which may be surgical access devices with insufflation capability, or other instruments, such one or more veress needles. The surgical devices  131 ,  133 ,  135  are thus individually connected to one of the supply conduit  114 , return conduit  112  and insufflation conduit  118 , and therefore respectively facilitate that function. 
     As set forth above, in one preferred aspect, the separate distal tube portions of the tube set  150  are connected by way of a conventional fitting, such as a luer-lock fitting on a conventional surgical device. The precise configuration of the tube set  150  can vary depending on the desired configuration. An example of a fitting for a multi-lumen tube set is described in commonly assigned U.S. Pat. No. 9,526,886, the disclosure of which is herein incorporated by reference in its entirety. 
     A disposable filter  116  is also associated with the tube set  150 , either separate therefrom or integral therewith. A filter suitable for use with a multimodal gas delivery system  100  with insufflation, smoke evacuation and recirculation functionality for use with specialized pneumatically sealed surgical access devices is disclosed in U.S. Pat. Nos. 9,067,030 and 9,526,849, the disclosures of which are herein incorporated by reference in their entireties. 
     It is envisioned that the disposable tube sets  150  and/or filters  116  used in connection with the system  100 , can be provided with identification devices that permit authorized use or otherwise prevent unauthorized use. Such identification devices can include, but are not limited to, a radio-frequency identification (RFID) transponder, computer readable data chip, bar code or other data-carrying element provided thereon. It is also envisioned that the identification device on the filter or tube set could cause or otherwise instruct the gas delivery system  100  to automatically switch into or launch in a particular operating mode (e.g., recirculation, smoke evacuation, or standard insufflation). 
     With continuing reference to  FIG. 1 , system  100  further includes a second dump valve  115  in connection with the fluid supply conduit  114 . In addition, to the short-circuiting action of the back-pressure control valve  113  described above, the system  100  is provided with a pressure sensor  117 , which can be mechanical or electronic as illustrated. Sensor  117  is in fluid communication with the insufflation conduit  118  or other source of abdominal pressure. When an over-pressure condition is sensed, the pressure sensor  117  signals the dump valve  115  to release fluid out of the system  100 . 
     System  100  can be employed with one surgical device  131  being used for insufflation and sensing functions, and another surgical device  135  serving to remove insufflation gas from the abdomen, which then passes through a filter, such as an ultralow-penetration air (“ULPA”) filter element  116  for example, before returning to the pump  111 . The filter  116  is preferably configured and adapted to clear all or essentially all smoke and debris from the gas passing therethrough, with the gas being returned to the abdominal cavity  190  through a third surgical device  133 . As illustrated, another filter element  116  can be provided in connection with the supply conduit  114  leading from the pump  111 . 
     For the purposes of explanation and illustration, and not limitation, a schematic illustration of an exemplary embodiment of a surgical gas delivery system in accordance with another aspect of the subject invention is shown in  FIG. 3  and is designated generally by reference numeral  200 . As compared with the system  100  of  FIG. 1  the system  200  only requires two surgical devices  231 ,  233 . The functionalities of components described above in connection with the system  100  of  FIG. 1  are the same as the corresponding components of the system  200  of  FIG. 2 , unless otherwise specified below. 
     The system  200  is in many ways similar to the system  100 , but with the addition of a diverting valve  295 , having three conduits  112 ,  114 ,  118  leading from other active internal system components, and two conduits  251 ,  253  leading, respectively, to two different surgical devices  231 ,  233 . 
     As illustrated, the diverting valve  295  is provided integrally, within the control unit  210 , as indicated schematically by placement of broken line referenced by number  210 . The diverting valve  295  is provided with three operating positions—positions, A, B and C, corresponding to different functions, as described below. When the sensing function of the system  200  is active, the diverting valve  295  is positioned in, position “A”, permitting connection of the insufflation/sensing conduit  118  therethrough, through one or both of the conduits  251 ,  253  of the tube set  250 , and to one or both of the surgical devices  231 ,  233 . 
     If configured to connect the insufflation/sensing conduit  118  to more than one surgical device, the potential for a lumen of such surgical device being blocked and thus not providing an accurate reading, is reduced. When the diverting valve  295  is positioned at position A, and connects the insufflation/sensing conduit  118  to the conduits  251 ,  253  of the tube set  250  and thus to the surgical devices  231 ,  233 , the insufflator subunit  121  is permitted to sense the abdominal pressure. In position A, output from the pump  111  enters the diverting valve  295  and is returned to the pump  111  immediately by mutually connecting the supply conduit  114  and return conduit  112  under such circumstances. This configuration allows the pump  111  to continue running during sensing and thus avoids any power spikes which might occur if stopping and restarting of the pump  111 . 
     If the system  200  is set to a suitable mode (such as combined smoke evacuation and insufflation), when the insufflator subunit  121  is finished sensing the abdominal pressure, the diverting valve  295  is switched from position A, to Position B, in order to connect the supply conduit  114  to a corresponding conduit  251  of the tube set  250 , and the return conduit  112  to a corresponding conduit  253  of the tube set  250 . In position B, the insufflator conduit  118  is connected to the return conduit  112 , permitting addition of insufflation gas into the system  200  through the return conduit  112 . Concurrently, the insufflator subunit  121  can be set to insufflating mode only, therefore only adding gas to the system  200  and not sensing pressures. While in position B, the diverting valve  295  permits delivery and return of fluid therethrough, between the pump  111  and filters  216 , and the surgical devices  231 ,  233 , and therefore gas exchange with, and filtration of, insufflation gasses from the surgical cavity  190 . 
     If the pump and tube volume are considered as one controlled volume in conjunction with the volume of the surgical cavity  190 , the function of the insufflator subunit  121  alone—switching from sensing to supplying carbon dioxide—is performed as in conventional surgical insufflators, in accordance with a preferred aspect. Accordingly, as described above, in system  200  of  FIG. 3 , smoke evacuation and filtration is only performed when the diverting valve  295  permits the insufflator control  121  to provide gas to the surgical cavity  190 . In such an arrangement, toggling to and from smoke evacuation/filtration and pressure sensing can be configured as either a normally sensing mode, or as a normally filtering mode, as desired or required. A normally sensing mode is likely to be preferred over a normally filtering mode, as monitoring of abdominal pressures is typically a priority. 
     As illustrated, position C of the diverting valve  295  permits the system  200  to be operated in a recirculation mode, which is suitable for providing sufficient pressures and flow rates to drive pneumatically sealed surgical access devices such as those described in U.S. Pat. Nos. 7,854,724 and 8,795,223, for example. In such a mode, a single tube of three lumens is typically provided, one lumen being in fluid communication with each of the supply conduit  112 , return conduit  114  and the insufflation conduit  118 . 
     In certain applications, it is advantageous to monitor pressure at the surgical cavity  190 , in real time, during insufflation. Real time pressure monitoring helps to better detect and respond to changes in pressure the surgical cavity. Furthermore, continuous pressure monitoring in conjunction with the consistent flow of new or recirculated insufflation gas also facilitate improved smoke removal from the surgical cavity. 
     With continuing reference to  FIGS. 1-3 , systems  100 ,  200  include a flow meter  123  positioned between the insufflation gas source  140  and the abdominal cavity  190 . Flow meter  123  measures the fluid flow through the associated insufflation conduit  118 . Monitoring of abdominal pressure in real time is accomplished by driving fluid flow through the conduit  118  at a constant source pressure by regulating the pressure provided from source  140  using insufflation subunit  121 . 
     As the amount of fluid flowing through conduit  118  varies, depending upon the amount of pressure at the surgical cavity  190 , the flow meter  123  measures the fluid flow. The processor  12  of system  100 ,  200  uses the fluid flow reading from flow meter  123  to determine pressure at the surgical cavity  190 , for a given source pressure provided by source  140 . Pressure at the surgical cavity  190  can be determined by the processor  12  using data stored in memory  14  of system  100 ,  200 , for example, in a look up table, or through calibration of the fluid path to the surgical cavity  190 , or a combination of both. When using data stored in memory  14  of system  100 ,  200  the appropriate data is selected by the processor  12  based on the known dimensions of a portion of the fluid path to the surgical cavity  190 , for example, the luer connection to a trocar or cannula connecting the surgical cavity  190  to system  100 ,  200 . 
     The known dimensions of the portion of the fluid path, in this instance the trocar or cannula luer connection, can be an industry standard, for example, ISO 594-1:1986 or ISO 594-2:1998, or known dimensions of a compatible component, for example, one of the trocars disclosed in U.S. Pat. No. 7,854,724, or 8,795,223, the disclosures of which are incorporated herein in their entireties. The known dimensions permit assumptions to be made as to the amount of flow through that portion of the fluid path for a given driving pressure, which in turn can be used to infer pressure at the surgical cavity  190  using, for example, a look up table stored in the memory  14  of system  100 ,  200 .  FIG. 4  illustrates an example of a look up table for a driving pressure of 60 mm of Hg at a variable flow rate provided by insufflation gas source  140 . 
     When the fluid path does not include known dimensions, pressure at the surgical cavity  190  can be determined by the processor  12  of system  100 ,  200  using a calibration algorithm. When calibration algorithm is used, system  100 ,  200  senses pressure at surgical cavity  190 , for example, using the pressure sensor included in insufflation subunit  121  or using a dedicated pressure sensor  122  positioned along the fluid path to the surgical cavity  190 . Calibration can be accomplished by taking periodic static pressure measurements using one of the pressure sensors described above and associating those pressure measurements with the periodic flow measurements taken using the flow meter  123 . In certain situations, it can be advantageous to combine calibration with the inferring technique described above. 
     Alternatively, monitoring of abdominal pressure in real time can be accomplished by driving fluid flow through the conduit  118  at a variable source pressure by regulating the pressure provided from source  140  using insufflation subunit  121 . The amount of fluid flow through conduit  118  is specified and maintained using a feedback from flow meter  123  to the insufflation subunit  121 . The amount of source pressure needed to maintain the specified flow through the fluid path depends on the amount of pressure at the surgical cavity  190 . A pressure sensor, for example, the pressure sensor included in insufflation subunit  121  or one, for example, pressure sensor  122 , positioned along the fluid path to the surgical cavity  190 , for example, near the pressure source or subunit  121 , measures the variable source pressure required to maintain the specified flow through the fluid path. 
     In this embodiment, pressure at the surgical cavity  190  can be determined by the processor  12  using data stored in memory  14  of system  100 ,  200  for example, in a look up table, or through calibration of the fluid path to the surgical cavity  190 , or a combination of both. When using data stored in system  100 , the appropriate data is selected based on the known dimensions of a portion of the fluid path to the surgical cavity  190 , for example, the luer connection to a trocar or cannula connecting the surgical cavity  190  to system  100 ,  200 . The known dimensions of the portion of the fluid path, in this instance the trocar or cannula luer connection, can be an industry standard, for example, ISO 594-1:1986 or ISO 594-2:1998, or known dimensions of a compatible component, for example, one of the trocars disclosed in U.S. Pat. Nos. 9,095,372, 7,854,724, or 8,795,223, the disclosures of which are incorporated herein in their entireties. 
     The known dimensions permit assumptions to be made as to the amount of source pressure needed to maintain the specified fluid flow through that portion of the fluid path, which in turn can be used to infer pressure at the surgical cavity  190  using, for example, a look up table stored in system  100 .  FIG. 5  illustrates an example of a look up table for a specified fluid flow of 3 L/minute through the fluid path. 
     When the fluid path does not include known dimensions, pressure at the surgical cavity  190  can be determined using a calibration algorithm. When calibration algorithm is used, system  100 ,  200  senses pressure at surgical cavity  190 , for example, using the pressure sensor included in insufflation subunit  121  or using a dedicated pressure sensor, for example, pressure sensor  122 , positioned along the fluid path to the surgical cavity  190 . Calibration can be accomplished in processor  12  of system  100 ,  200  by taking periodic static pressure measurements using one of the pressure sensors described above and associating those pressure measurements with corresponding driving pressures regulated by subunit  121 . In certain applications, it can be advantageous to combine calibration with the inferring technique described above for a specific fluid flow. 
     While the subject disclosure has been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.