Abstract:
Apparatus for controlling the volume of surgical fluid present in a cavity in the body of a patient during surgery includes a conduit to the cavity for conducting the surgical fluid therefrom to at least one receptacle for receiving the fluid from said cavity. A source of vacuum assists in withdrawing fluid from the cavity and a vacuum controller interposed between the vacuum source and the receptacle controls the duration of time the receptacle is exposed to vacuum from the vacuum source. The apparatus preferably has a vacuum sensor for sensing vacuum levels in the receptacle when disconnected from the source of vacuum and shares the source of vacuum with another application, giving priority to maintaining a proper vacuum level in the receptacle.

Description:
FIELD OF THE INVENTION 
   The present invention relates to medical procedures and devices, more particularly to those devices used to infuse and remove fluids from the body of a patient during a surgical procedure. 
   BACKGROUND OF THE INVENTION 
   Endoscopic/laproscopic surgical procedures have grown significantly in popularity over the years due to the fact that they are minimally invasive and the miniature, remotely-controlled surgical instruments used have improved. To allow such procedures to be undertaken, means are frequently required to distend the patient&#39;s body cavity at the site of surgery to allow for surgical implement manipulation and visualization. Gasous or liquid insulflatants are used for this purpose depending upon the operation. Certain procedures also utilize a liquid insulflatant as a lavage for removing blood and excised tissue from the surgical site to maintain visibility and to clean the area. For example, in fibroid removal, the uterus is flooded with a clear liquid, e.g., isotonic saline solution, under sufficient pressure to separate the walls of the uterus to permit the surgical site to be viewed with an endoscope. After the uterine cavity has been distended by the liquid, a surgical tool such as an electrocautery tool or resectoscope, may be positioned within the uterus to remove the fibroids which are vaporized at its cutting surface. During the surgery, fluid flow out of the uterus is maintained and the severed tissue and electro surgical debris are removed from the uterus with the outflowing fluid. During procedures of this type, the amount of irrigating liquid present in the patient&#39;s body must be closely controlled because excessive absorption thereof can be extremely detrimental to the patient. Accordingly, inflow to the body cavity must closely approximate outflow. In certain instances, a pressure differential is provided in order to maintain distension of the cavity. Many fluid management systems utilize a source of vacuum to control fluid outflow. Various methods have been proposed in the past to monitor the fluid inflow and outflow in surgical fluid management systems, but there is a continuing need for ever improved precision in the management of fluid flow in these applications. Accordingly, an object of the present invention is to provide for simpler, more accurate and more reliable fluid flow control during surgical procedures. 
   SUMMARY OF THE INVENTION 
   The problems and disadvantages associated with conventional techniques and devices for controlling the volume of surgical fluid present in a cavity of the body during surgery are overcome by the present invention which includes a conduit to the cavity for conducting the surgical fluid therefrom into at least one receptacle for receiving the fluid from the cavity. A source of vacuum assists in withdrawing fluid from the cavity and a vacuum controller interposed between the vacuum source and the receptacle controls the duration of time the receptacle is exposed to vacuum from the vacuum source. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     For a better understanding of the present invention, reference is made to the following detailed description of an exemplary embodiment considered in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a schematic diagram of a fluid management system as known in the prior art; 
       FIG. 2  is a schematic view of a fluid management system in accordance with the present invention; 
       FIG. 3  is a front perspective view of a flow dampener in accordance with the present invention; 
       FIG. 4  is a rear perspective view of the flow dampener of  FIG. 3 ; 
       FIG. 5  is a cross-sectional view of the flow dampener of  FIG. 3  taken along section lines V—V and looking in the direction of the arrows; 
       FIG. 6  is a cross-sectional view of the flow dampener of  FIG. 4  taken along section lines VI—VI and looking in the direction of the arrows; 
       FIG. 7  is a cross-sectional view of the flow dampener of  FIG. 4  taken along section lines VII—VII and looking in the direction of the arrows; 
       FIG. 8  is an end-on view of the cross-section of the flow dampener shown in  FIG. 7 ; 
       FIG. 9  is a diagrammatic view of light transmitted through an empty tube and reflected from an adjacent reflective member; 
       FIG. 10  is a circuit diagram for an optical sensor in accordance with the present invention; 
       FIG. 11  is a perspective view of an optical fluid sensor in accordance with a second embodiment of the present invention; 
       FIGS. 12-14  are cross-section views of second, third and fourth embodiments of the flow dampener of the present invention; 
       FIG. 15  is a schematic diagram showing the relationship between elements in a vacuum control system in accordance with the present invention; 
       FIGS. 16 and 17  are schematic diagrams showing a spool valve in two different states of distributing and measuring vacuum in a fluid management system in accordance with the present invention; and 
       FIG. 18  is a graph of pressure vs. time exhibited by a fluid management system in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a fluid management system  10 ′ in accordance with the prior art and includes those components necessary to simultaneously fill and drain a body cavity  12 ′, such as the uterus, with a liquid for distending the body cavity. The liquid may also be used for removing surgical debris, blood and exudate from the cavity  12 ′ during surgery via a continuous flow into and out of the cavity  12 ′. The fluid is pumped to the cavity  12 ′ by a pump  14 ′ which is fed by a suitable reservoir  16 ′ of sterile fluid, such as isotonic saline solution. Fluid pumped to the cavity  12 ′fills and distends it to facilitate performing a surgical procedure therein. A vacuum source  18 ′ provides suction under the control of a vacuum regulator  20 ′ to aid in withdrawing fluid from the cavity  12 ′. The regulator  20 ′ acts through a flow-back filter  22 ′ which prevents fluid withdrawn from the cavity  12 ′ from flowing into the vacuum regulator  20 ′ or the vacuum source  18 ′. The foregoing arrangement is used to establish a constant flow of fluid to and from the cavity  12 ′ and thereby establishes an equilibrium fluid level and pressure in the cavity  12 ′. On the vacuum side of the fluid management system  10 ′, a plurality of receptacles  24 ′,  26 ′ may be provided to receive waste fluid that has been withdrawn from the cavity  12 ′. Typically, these fluid receptacles are arranged in series and provide some convenient and sanitary method and apparatus for disposal of the wasted surgical fluid, such as by using removable plastic liners and the like. Given that there is a positive fluid pressure present in the cavity  12 ′ for distending the walls of the cavity  12 ′ and that neither the inlet fluid conduit  25 ′ or the suction fluid conduit  27 ′ is perfectly sealed, some fluid leakage is to be expected and is collected in a surgical drape system  28 ′. The drape system  28 ′ is drained of surgical fluid by the vacuum system  18 ′,  20 ′,  22 ′, which draws it into fluid receptacle  29 ′. Because the fluid retention levels in the patient are critical, the fluid management system described must maintain an acceptable equilibrium fluid volume and pressure in the cavity  12 ′. As can be appreciated, this requires close monitoring and control of the pump  14 ′ that delivers fluid to the cavity  12 ′, as well as the vacuum  18 ′ which withdraws surgical fluid to waste. 
   In  FIG. 2 , the present invention is shown to include a fluid management system  30  having a pump  32  preferably controlled by a feedback control loop as described below. Fluid is drawn from the reservoir  16  and pumped through a flow dampener  34  which smooths the output pressure variations of the pump  32 . Pump  32  is typically a peristaltic type pump utilizing a plurality of rollers that sequentially compress a tube to impart motion to the fluid while preserving sterility of the fluid. The flow dampener  34  preferably includes a pressure sensor  36  for sensing pressure within the flow dampener  34  and a flow sensor  38  to sense the presence of fluid passing through the flow dampener  34 . Both sensors  36 ,  38  preferably communicate their data output to a microprocessor controller  40  that may then utilize that sensor information to control the speed and/or cycle time of the pump  32 . Alternatively, pressure and flow data may be displayed on a visual indicator to cue an operator to adjust the pump  32 . As yet another alternative, the pump  32  may be equipped with its own pressure sensing probe and pressure responsive controller as more fully described in reference to  FIG. 4. A  user interface  42  is preferably provided which may include a monitor to display the pressure and flow sensed by the pressure sensor  36  and flow sensor  38 , as well as the present output volume of the pump  32 . The user interface  42  would typically also include a keyboard or other input device for setting the parameters of system  30  operation. 
   On the suction side of the system, a plurality of receptacles  24 ,  26  receive the waste fluid from the cavity  12  for temporary storage and disposal. A flow-back filter  23  is provided in the vacuum line drawing fluid from the cavity  12  and a separate flow-back filter  25  is provided in the drape vacuum line. A regulator valve  44 , which may be manually or automatically controlled by the controller  40 , controls the presence of vacuum on the vacuum side of the system by connecting or disconnecting with the vacuum source  18 . Vacuum present when the valve  44  is open is regulated by the vacuum controller  46  which will be described further below. The vacuum controller  46  acts in cooperation with a vacuum sensor  48  and a vent valve  50  to provide the appropriate amount of vacuum required to maintain the desired fluid level and pressure in the cavity  12 , given the inflow established by the pump  32 . The vacuum sensor  48  preferably provides vacuum data to the controller  40  which then controls the operation of the vacuum controller  46  and vent valve  50 , e.g., by varying the time that vacuum is applied to the flow-back filters  23  and  25  as shall be described further below. 
     FIG. 3  shows the flow dampener  34  having a pressure chamber  52  which is supplied with fluid by inlet tube  54 . Fluid exiting the pressure chamber  52  does so via outlet fitting  56 . The pressure chamber  52  is formed by joining a pair of hollow mating members  52   a  and  52   b  and includes on the face thereof an indentation  62  to enable the user thereof to grip the flow dampener  34 . Distal to the pressure chamber  52 , the flow dampener  34  has a coupling plate  58  and a rotor opening  60  that enables the dampener to be fitted to a standard peristaltic pump as can be appreciated more fully in reference to  FIGS. 4 and 6 . 
   Referring to  FIG. 4 , the flow dampener  34  includes a tubing section  64  having a u-shaped configuration that communicates with the inlet tube  54 . The u-shaped section  64  interacts with the rollers  66  of a peristaltic pump, as shown diagrammatically in  FIG. 6. A  window  60  permits the rollers  66  to engage tubing  64 . In the embodiment in  FIG. 4 , the pressure sensor  36  includes a pressure sensing diaphragm  70  that is distended or displaced outwardly by pressure internal to pressure chamber  52 . The external distension of the pressure sensing diaphragm  70  is sensed by a pressure probe shaft  72  associated with the peristaltic pump to which the dampener  34  is fitted. The sensed pressure is used for controlling the motor of the pump to maintain a particular pressure automatically, viz., if sensed pressure drops below the setpoint, the pump  32  is turned on. If sensed pressure exceeds the setpoint, the pump  32  is turned off. The foregoing pressure sensing and control feedback arrangement operates either in isolation or in cooperation with the digital controller  40  of FIG.  2 . 
   A fluid detection window  68  is provided in an upper portion of the pressure chamber shell  52   b  proximate to the inlet tube  54  which is preferably clear or light transmissive material. The fluid detection window  68  is utilized with an optical sensor described further below for determining if fluid fills the inlet tube  54 . The pressure chamber  52  has an air vent  74  that is used to vent the chamber  52  of excess air and to allow the fluid to rise to a specific level within the chamber  52 , as described further below. 
     FIG. 5  shows a first dampener  34  embodiment with an air vent  74  for maintaining a predetermined fluid level within the pressure chamber  52 . A hydrophobic micropore filter  76  permits air to flow therethrough allowing the fluid  78  level to rise to just cover the hydrophobic filter  76 . A one way valve  80 , e.g., a mushroom valve, prevents air from entering the pressure chamber  52  in response to negative pressure therein. The fluid  78  traps a pocket of air  86  thereabove, with gravity maintaining this stratified air/fluid separation. The pocket of air  86  exhibits the expected pressure/volume relationship at room temperature in accordance with Boyle&#39;s law. With increased fluid input, the air pocket  86  becomes pressurized and this pressure is transmitted to the pressure sensor  36  (i.e., the pressure sensing diaphragm  70 ). Because the air pocket  86  is compressible, unlike the fluid  78 , variations in output volume from the pump  32  (i.e., due to turning rollers  66  which sequentially squeeze down upon the unshaped section  64 ) are smoothed by the air pocket  86 , which acts like a cushion. More specifically, the fluid exiting the pressure chamber  52  is propelled therefrom by the pressure prevailing in the air pocket  86 . Small variations in pump  32  output volume to the pressure chamber  52  do not cause significant variations in pressure in the air pocket  86 . As a consequence, fluid output from the pressure chamber  52  is more constant. The air pocket  86  also retains gases that are contained in the fluid, thereby avoiding pumping gases in the fluid to the surgical site. 
     FIG. 6  shows the interaction of the rollers  66  of a peristaltic pump  32  with the u-shaped section  64  of tubing, such interaction inducing a flow of fluid in the direction of the arrows shown. Specifically, fluid flows into the inlet tube  54  and through the u-shaped section  64  into the pressure chamber  52 . A pair of baffles  82 ,  84  are shown positioned around a fluid inlet  85  of the pressure chamber  52 . The baffles  82 ,  84  induce a fluid flow in an upward direction and prevent the in-flowing fluid to flow out the outlet directly, thereby permitting air or other gases entrained in the fluid to rise through the fluid  78  into the upper portion of the pressure chamber  52  (i.e., into the air pocket  86 ). 
     FIG. 7  shows how a flow sensor  38  (see  FIG. 2 ) may be incorporated into the flow dampener  34  of the present invention. More particularly, a light-emitting element  90 , such as a light bulb or LED, is positioned proximate to the light detection window  68 . The light emitted by the element  90  is transmitted through the light-transmissive tubing  88  and strikes a reflective surface or mirror  94  on the other side of the tubing  88 . Light reflected from the mirror  94  is retransmitted through the tubing  88  and strikes a light-sensing element  92 , such as a photodiode or phototransistor, that converts the incoming light signal to a voltage level or current flow. 
   Referring to  FIGS. 8 and 9 , one can appreciate how the foregoing light sensing arrangement will operate, namely, that light emitted by the element  90  will pass through the tubing  88 , if it is empty, in a diffuse manner and will strike the mirror  94  and diffuse even further, such that the return signal to the light-sensing element  92  will be weak (see FIG.  9 ). In contrast, if the tubing  88  is filled with fluid as shown in  FIG. 8 , it will act as a lens, focusing the light signal from the light-emitting element  90  on the reflective surface  94  such that the signal retransmitted from the mirror  94  will be likewise focused on the light-sensing element  92  and will have a much greater magnitude than if the tubing  88  were empty. The light signal received at the light-sensing element  92  can then be processed by suitable circuitry, e.g., like that shown in  FIG. 10 , to interpret the variation in light magnitude to indicate the presence of fluid in the tubing  88  or the lack of fluid. 
     FIG. 10  shows a circuit  91  having a light-emitting element  90  (in the form of a light-emitting diode) and a light-sensing element  92  (in the form of a phototransistor), which would by physically juxtaposed as shown in FIG.  7 . The voltage at point  93  will vary depending on the current flow through the light-sensing element (i.e., phototransistor)  92  as determined by the presence or absence of fluid in tubing  88  (see  FIG. 7 ) and the corresponding magnitude of light transmitted to the light-sensing element (i.e., phototransistor)  92 . The voltage level at  93  is compared with a reference voltage and the difference amplified by operational amplifier  95 , the output of which is the signal representing the presence or absence of fluid in the tubing  88 . 
     FIG. 11  shows an alternative embodiment for a fluid detector  96  in accordance with the present invention which includes a body  98  having a tube receptacle  100  formed therein. The tube receptacle  100  slidably receives a tube (not shown) which can be flattened slightly and inserted into the narrowed portion of the tube receptacle  100  and then allowed to relax and assume its normal cylindrical shape. As before, a light-emitting element  90  can be placed on one side of the tubing. In this embodiment however,rather than having a single photodetector and circuitry to distinguish between two light magnitudes associated with the presence or absence of fluid in the tube, there are two light-sensing elements  92   a ,  92   b  spatially separated such that if a diffuse transmission of light through the tube results, namely if the tube is empty, then both of the spaced light-sensing elements  92   a ,  92   b  will receive the light transmission. Otherwise, if the transmission is focused due to the presence of fluid in the tube, then only the light-sensing element  92   b  will be exposed to the light transmission. The signals received by the light-sensing elements  92   a ,  92   b  can be compared, amplified, etc. in order to convey a signal indicative of the presence or absence of fluid in a tube about which the detector  96  is positioned. 
     FIGS. 12 ,  13  and  14  show variations of the flow dampener  34  described above, with  FIG. 12  having a modified baffle  182  which causes the input flow to reverse direction. As before, a hydrophobic micropore filter  174  determines fluid level in the pressure chamber  152 . 
   In  FIG. 13 , the hydrophobic micropore filter of the previous embodiments has been replaced by an upper air vent orifice  274  which is stoppered and unstoppered depending upon the fluid level  278  within the pressure chamber  252  which lifts float  277  and plug  279  to close the air vent  274 . 
   In  FIG. 14 , the hydrophobic micropore filter has been replaced with an air vent  374  that is controlled by a needle valve  379 , the position of which is responsive to fluid level  378  which urges float  377  up and down. In  FIG. 14 , the buoyancy of float  377  is counterbalanced by a pair of pistons  381 ,  383 , each having different cross-sectional areas and thereby applying different counteracting forces on a shaft  389  that couples the pistons  381 ,  383  and attaches to the float  377 . A common cylinder sleeve  385 , which includes upper and lower mating cylinder bores, vents centrally to the atmosphere via a vent  387 . 
   Turning now to the suction side of the system  30 , one will recall that in a conventional fluid management systems vacuum control like the one shown in  FIG. 1 , a mechanical vacuum regulator regulates a pressure common to multiple fluid receptacles, i.e., those going to the fluid receptacles  24 ′,  26 ′, as well as to the drape system  28 ′. Frequently, the large volume of flow attributable to the drape system  28 ′ overpowers the common regulator dropping the vacuum level to the fluid receptacles  24 ′,  26 ′ until the drape suction is turned off. This situation is compounded by the fact that vacuum regulators are sometimes ineffective in supplying a well-regulated high volume flow and often vent very slowly if the vacuum is too high. In conventional systems, the vacuum level is sensed at the regulator, therefore vacuum drops through the flow-back filter  22 ′, the receptacles  24 ′,  26 ′ and their associated tubing are not compensated for in regulating the vacuum. 
     FIG. 15  diagrammatically shows that the vacuum controller  46  of the present invention provides controlled vacuum to the body cavity  12  (resectoscope suction), be uncontrolled vacuum to the surgical drape where maintenance of controlled vacuum is less critical. The present invention thus utilizes prioritized vacuum sharing wherein the vacuum controller  46  maintains a regulated vacuum in the fluid receptacles  24 , 26  connected to the resectoscope. Any remaining vacuum is routed to the drape suction once sufficient vacuum is directed to the fluid receptacles  24 ,  26 . This eliminates the problem of an open drape suction overpowering the ability to maintain a good regulated vacuum. The valve means for performing the foregoing are described below in reference to  FIGS. 16 and 17 . 
     FIGS. 16 and 17  show the vacuum controller  46  equipped with a high capacity spool valve  47  actuated by actuator  49  under the control of microprocessor  51  based upon signals representing vacuum magnitude received from the vacuum sensor  48 . 
   In position A shown in  FIG. 16 , the controlled vacuum outlet is connected to the vacuum sensor  48  and the vent valve  50 . The vacuum appearing at regulator valve  44  is connected to the spare vacuum output connected to the flow-back filter  25  leading to the drape. If the vent valve  50  is open in this position, it will vent the controlled vacuum. If the vent valve  50  is closed, the vacuum sensor  48  can measure the vacuum in the controlled vacuum receptacles  24 ,  26  with no flow and therefore no erroneous vacuum readings. The present invention recognizes the fact that when vacuum is applied to the receptacles  24 ,  26 , there is significant pressure drop through the flow-back filter  23  and the tubing to the receptacles  24 ,  26 . The present invention samples the vacuum pressure only when the flow is stopped so that the vacuum controller  46  can operate based on a more accurate vacuum reading. 
   In position B shown in  FIG. 17 , the controlled vacuum outlet is connected to the vacuum appearing at regulator valve  44 . The vacuum sensor  48  and the spare vacuum to the flow-back filter  25  leading to the drape are blocked. In this position, vacuum in the receptacles  24 ,  26  and heading to the cavity  12  increases. 
   To control the level of vacuum evacuating the fluid from the cavity  12 , a software algorithm in microprocessor  51  switches the spool valve  49  between position A and position B periodically, e.g., once per second. The amount of time the valve  47  is in position B, supplying vacuum to the controlled receptacles  24 ,  26 , is based upon the last vacuum measurement made in position B. By observing the change in vacuum level from one measurement to the next in relationship to how long the spool valve  47  was last held in position B, the software can determine how long to next hold the spool valve  47  in position B to achieve and maintain a given vacuum level in the controlled vacuum receptacles  24 ,  26 . 
   The low restriction spool valve  47  allows quick changes in the vacuum level in the controlled vacuum receptacles  24 ,  26 . The inclusion of the vent valve  50  makes increasing the pressure (bleeding off vacuum) quick as well. This relationship is depicted graphically in FIG.  18 . 
     FIG. 18  shows the vacuum present in the receptacle  26  as a function of time and as a result of the intermittent connection of the flow-back filter  23  to the vacuum source  18  via the vacuum controller  46  and more specifically the spool valve  47 . At time t 1 , the spool valve  47  is placed in position B (see FIG.  17 ), whereupon the vacuum directed to cavity  12  increases rapidly (drop in pressure). The spool valve  47  is held in position B until time t 2 , when it is cycled to position A (see FIG.  16 ). Time period t 1  to t 2  can be described as the time the cavity  12  suction is exposed to input vacuum or t v . The change of position of the spool valve  47  from position B to position A is not instantaneous but rather occurs over a transition period t trans  extending from time t 2 to t 3  Once the spool valve  47  is in position A at t 3 , the vacuum present in elements (i.e., the flow-back filter  23  and the reservoirs  24 ,  26 ) between the spool valve  47  and the cavity  12  can stabilize during the period from t 3  to t 4  when the spool valve  47  remains in position A. The time period from t 3  to t 4  when the vacuum source  18  is isolated from the flow-back filter  23  may be called t off . During t off  a vacuum drop (raise in pressure) Δp  is experienced. The foregoing process is repeated cyclically such that the number of complete cycles from t 1 to t 4  over a reference time period is the frequency. The objective then is to vary the pulse widths representing the times when the spool valve  47  is alternately in positions B and A so that the approximate average or intermediate pressure P i  during t off  approximates the set point pressure P s . This can be accomplished under algorithmic control by interactively measuring the vacuum and adjusting t v  such that P i  approximates P s . 
   System capacity varies depending upon the number of receptacles  24 ,  26  chained together and the level of fluid fill in each. Thus, the relationship between t v  and Δp  varies as the case proceeds. The control loop evaluates the ratio of Δp/t v   and uses this in a difference equation to compute the next t v  in order to achieve a desired vacuum level. The slope of vacuum drop over time t off  is a measure of air flow. The control algorithm preferably maintains a maximum Δp  difference within some minimum valve cycle time. 
   The variable t v  is computed based on the last observed Δp  and the desired Δp. A pulse may be skipped to vent vacuum. Maximum t v  must be less than the repetition rate so that Δp  can be measured, i.e., a minimum t off  time is required at least once per/period. Once t off  is at minimum, the vacuum flow is maxed out. 
   It should be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention as defined in the appended claims.