Abstract:
A warming gas flows through a jacket to heat an insufflation gas flowing in a separate tube, thereby reducing cost and disposable waste. The heated warming gas may be filtered to sterilize or maintain sterility and released to atmosphere after heating the flowing insufflation gas. Alternatively the warming gas may be reheated and recirculated through the jacket, with an additional tube being used within the jacket so that the warming gas flows in both directions lengthwise. As an alternative to separate tubes, a single, multi-lumen tube may be used. The insufflation gas may be CO 2  and the warming gas may be room air. The heating element and sensors may be separate from the disposable unit of a heated insufflation set, and need not be re-sterilized prior to or after use in surgery. The heat is constantly maintained, thereby eliminating “cold spots” caused by the natural cycling of the resistance heaters.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/902,826, filed Oct. 12, 2010, which claims priority from U.S. Provisional Patent Application Ser. No. 61/250,144, filed Oct. 9, 2009, the entire content of both of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to instruments and methods used in minimally invasive surgery and, in particular, to apparatus and methods for heating insufflation gas of the type used in laparoscopic procedures. 
       BACKGROUND OF THE INVENTION 
       [0003]    Laparoscopic surgery, also called minimally invasive surgery (MIS) is a recent development in which operations in the abdominal or pelvic cavities, for example, are performed through small incisions (usually 0.5-1.5 cm) as compared to larger incisions associated with “open” surgical procedures. Laparoscopic procedures typically use images displayed on TV monitors for magnification of the surgical elements as oppose to direct visualization by the surgeon. 
         [0004]    There are a number of advantages to the patient with laparoscopic surgery versus an open procedure. These include reduced pain due to smaller incisions and hemorrhaging, and shorter recovery time. A key element is the use of a laparoscope, which may either be a telescopic rod lens system connected to a video camera or a digital laparoscope wherein an image sensor is located at the end of the laparoscope, thereby eliminating the rod lens system. Also attached is a fiber optic cable system connected to a light source (i.e., halogen or xenon), to illuminate the operative field. 
         [0005]    During laparoscopic surgery, the abdomen (or other cavity) is usually insufflated, or blown up like a balloon, with carbon dioxide (or other) gas. This elevates the abdominal wall above the internal organs like a dome to create a working and viewing space. CO 2  is used because it is common to the human body and can be absorbed by tissue and removed by the respiratory system. It is also non-flammable, which is important because electrosurgical devices are commonly used in laparoscopic procedures. 
         [0006]    It has been suggested that replacing cold, dry CO 2  with heated, humidified gas for insufflation during complex laparoscopic procedures offers certain benefits, including decreased hypothermia and peritoneal cell desiccation, with a resultant decrease in postoperative pain and a shortened recovery. This has led to the development of numerous heated insufflation sets, many of which include humidification apparatus. 
         [0007]    One commercially available insufflation gas heater uses a separate heater “box” built into the set close to the patient. The heater is controlled by a separate heat controller remote from the heater, and may therefore be situated outside the sterile field. Other types use resistance wire heaters placed inside of the tubing. These wires are usually accompanied by an over-heat fuse. Some of these sets have wires which extend the overall length of the set, while others use resistance heating limited to the patient end. In some cases the wires are coiled; in other cases the wires are straight. 
         [0008]    There are several drawbacks to these existing approaches. The deficiencies are related to the fact that the CO 2  gas does not flow continuously but is instead intermittent, with flow in the range of 0 to 40 liters per minute. When first filling the body cavity the flow is very high; a high flow rate may also occur at other points in the operation as the surgeon manipulates instruments. With the flow of cold CO 2 , the controller delivers power to the resistance heater, and while this may occur rapidly, heat-up is limited by the need to avoid over heating which could burn the patient. Often times this results in unheated CO 2  entering the patient. 
         [0009]    Also existing sets are very expensive, as the heating element in all of the sets is disposable. In products that use a heater “box,” the entire heater unit either has to be autoclaved or thrown out and replaced with each use. The need remains for a more elegant solution. 
       SUMMARY OF THE INVENTION 
       [0010]    This invention improves upon existing insufflation gas heaters through the use of a warming gas which flows through a jacket to heat an insufflation gas flowing in a separate tube, thereby reducing waste and the cost of the equipment involved. Since the CO 2  does not flow directly over a heater such as a resistance wire as it travels from an insufflator to a patient, the heating element (and sensors) may separate from the disposable unit of a heated insufflation set, thereby reducing disposable waste. The heating element and sensors also need not be cleaned or re-sterilized prior to, or after, use in surgery, which reduces the cost of production of the disposable set and or the operation. Moreover, the heat is constantly maintained, thereby eliminating “cold spots” caused by the natural cycling of the resistance heaters due to the nature of the operation being performed on the patient. 
         [0011]    A basic system for heating insufflation gas in accordance with the invention comprises first and second tubes. The first tube carries insufflation gas from a proximal end to a distal end adapted for connection to an instrument used to inflate a body cavity with the insufflation gas. The second tube, surrounding or adjacent to the first tube, carries a warming gas to heat the first tube and the insufflation gas flowing therethrough. If the insufflation gas is already sufficiently warm, the system and method may be used to maintain temperature as opposed to “heating” it. 
         [0012]    The system may include a filter for sterilizing the warming gas so that it may be released into a surgical field at the distal end after heating the first tube and insufflation gas. Alternatively, the system may include a third tube within the second tube for carrying the warming gas from the proximal end of the first tube to the distal end of the second tube where the warming gas is released to flow back toward the proximal end and around the first tube. A port at the proximal end enables the warming gas to exit the second tube so that it can be re-heated and recirculated back into the third tube. 
         [0013]    As an alternative to separate tubes, multi-lumen tubes may be used in accordance with the invention. Such a tubing assembly would include a proximal end adapted for connection to a source of insufflation gas and a source of warming gas, and a distal end adapted for connection to an instrument used to inflate a body cavity with the insufflation gas. A flexible, elongated multi-lumen tube with an outer wall interconnects the proximal and distal ends of the tubing assembly. The multi-lumen tube includes a first lumen for flowing insufflation gas from the proximal end to the instrument, and at least one additional lumen for flowing a warming gas to heat or maintain the temperature of the insufflation gas as it flows through the first lumen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic diagram of a device to heat insufflation gas constructed in accordance with the invention. 
           [0015]      FIG. 2  depicts a tubing assembly for use with the heater of  FIG. 1 ; 
           [0016]      FIG. 3  depicts an alternative heater; 
           [0017]      FIG. 4  is a drawing that shows an alternative tubing assembly which eliminates a return heated gas line; 
           [0018]      FIG. 5A  is a cross section of a two-lumen tube constructed in accordance with the invention; 
           [0019]      FIG. 5B  is a cross section of a three-lumen tube; 
           [0020]      FIG. 5C  is a cross section of a multi-lumen tube; 
           [0021]      FIG. 5D  is a cross section of a three lumen tube with saddle-shaped air channels; 
           [0022]      FIG. 5E  is a cross section of a multi-lumen tube with saddle-shaped air channels; 
           [0023]      FIG. 6A  is a cross section of a tubing assembly utilizing the tube of  FIG. 5D ; and 
           [0024]      FIG. 6B  is an end-on view of the assembly of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    This invention relates to instruments and methods used in minimally invasive surgery (MIS) and, in particular, to apparatus and methods using a warming gas for heating insufflation gas of the type used in laparoscopic procedures. In all preferred embodiments, the insufflation gas is carbon dioxide and warming gas is air. Although any other non-flammable gas may be used for warming, certainly air is least expensive. 
         [0026]    One embodiment of the invention uses two remote heaters; one to heat the CO 2  insufflation gas to body temperature prior to entering the patient, and a second heater to control a circular flow of warming gas (i.e., room air) in a jacketed tubing assembly to heat the insufflation gas. The heaters may both run at a constant temperature of approximately 98° F. (i.e., 98±7°. As such, heat entering the body will be approximately 98° because the CO 2  has been preheated and heat is not allowed to escape into the atmosphere through the tubing walls. 
         [0027]    As an alternative to a separate heater for the insufflation gas, a single heater for the warming gas may be provided if the temperature and/or flow rate are sufficient. As a further alternative, a single heater may be used for the warming gas with the insufflation gas passing through a heat exchanger to pre-warm the insufflation gas prior to entry into the jacketed tubing assembly. 
         [0028]    As described in further detail herein below, the jacketed tubing assembly may have one or two internal tubes, depending upon whether the warming gas is recirculated or released in to the environment. If the warming gas is recycled (and re-heated), it need not be sterile as it does not enter the sterile surgical field. If the warming air is released after use, it preferably passes through a filter to “sterilize” the air, (i.e., to remove bacteria or virus). This latter configuration has the advantage of requiring only two tubing layers. This approach is less costly, easier to manufacture, and the tubing set is lighter and more flexible which may be desired in the marketplace. A dispersing member may be used to diffuse the preheated gas as it exits the tubing. 
         [0029]    Referring to the Figures, a system according to one embodiment of the invention includes a heater unit depicted generally at  10  and a tubing assembly shown generally at  100 . The length of the tubing assembly is variable, but may be on the order of 10 feet, or thereabouts. It should be understood that these drawings are intended to illustrate important structural components and operational functionality and are not necessarily drawn to scale. 
         [0030]    The tubing assembly  100  attaches to the heater unit  10  by way of a connector  140   a ,  140   b  as described in further detail with respect to  FIG. 2 . Insufflation gas such as carbon dioxide enters the heater unit  10  through port  14 . The gas is carried by an appropriate conduit coupled to a source of pressure-controlled insufflation gas (not shown) at a rate typically in the range of 0.5-50 liters/min. or greater as technology allows. The insufflation gas passes through coupling  16  and into heater unit  18  which heats the gas. Heater unit  18  may be a Cast-X type heater from Watlow of St. Louis, Mo., a self-contained unit using medical grade stainless-steel tubing. Numerous alternative heating devices may be used. The heated insufflation gas passes through tube  20  and exits the heater via coupling  140   a.  All components are sterilized such that the sterility of the insufflation gas is maintained throughout. 
         [0031]    Air or other warming gas is delivered by fan  24  and heated by heater  26  which may be a Model 375 finned strip heater, also available from Watlow. The warming gas is routed to tube  28  and through coupling  140   a  to the tubing assembly  100  at a flow rate in correlation to the heater temperature, which could be in the range of 1-2 cfm, enabling a desired heat to be maintained within the tube, depending upon the length of the tubing assembly and other factors. Return warming gas is received from inlet  22  through coupling  140   a,  which is recycled through fan  24  and reheated by heater  26  due to partition  12  in the heater unit  10 . 
         [0032]    Turning now to  FIG. 2 , as mentioned coupling  140   b  attaches to coupling  140   a , thereby connecting tube  106  to tube  22 ; tube  108  to tube  20 ; and tube  109  to tube  28 . Tube  108  carrying warmed CO 2  may pass through filter  107 . The warming gas travels through tube  109  from the proximal end  110  of the assembly to the distal end  112 , at which point it emerges into outer tube  102 , which may include lengthwise accordion structure  104 . As the warming gas travels back through the outer tube it heats or maintains the temperature of the CO 2  in tube  108 , which may terminate in a standard Luer-Lok fitting  130  for interconnection to an instrument used for body cavity inflation. 
         [0033]    In operation, the temperature of the gas used for insufflation may be maintained at a desired temperature, as in the range of 100° F. As such, the temperature of the warming gas may be set somewhat high to account for loss to the ambient environment. Although not shown, various temperature sensors and/or feedback systems may be incorporated to ensure reliable operation. For example, one or more thermistors may be included to monitor the temperature of either or both heaters or the gasses directly to maintain temperature control or to terminate heating if it becomes excessive. 
         [0034]    All of the tubes depicted in  FIG. 2  may be made of flexible plastic material. A distinct advantage of the system is that the tubing assembly  100  maintains temperature of the insufflation gas without the need for electrical heaters integral to the tubing, thereby reducing the cost of the tubing assembly  100 , which is typically discarded and replaced following each procedure. Although separate tubes are shown for the insufflation gas and warming gas, in alternative embodiments an extrusion process may be used to form three or more tubes simultaneously so that they touch or are at least in close proximity. 
         [0035]    In the embodiment of  FIGS. 1 ,  2  the warming gas is recycled and not released into the ambient atmosphere of the surgical suite. This has two advantages: one, the warming gas need not be sterile (through filtration may be added for such purpose), as the system is closed-loop; and two, the previously heated warming gas is essentially re-heated, which may cut down on power requirements. A disadvantage, however, is that the tubing assembly  100  required three passageways—one for the insufflation gas and two for the warming gas 
         [0036]    The embodiment of  FIGS. 3 ,  4  uses an additional filter  411  to ensure that the warming gas is sterile, enabling the gas to be released through port  412  at the distal end  420  of the tubing assembly. Although the warming gas filter is shown at the proximal end of the tubing assembly, it may alternatively be positioned inside the heater unit  10  or at the distal end  420  immediately prior to the exit port  412 . 
         [0037]    Otherwise the system and method of  FIGS. 3 ,  4  is similar to those described with reference to  FIGS. 1 ,  2 . The tubing assembly  400  connects to the heater unit  10  through connector  340   a,  which now only has two passageways. Connector  340   a  connects to  340   b , coupled to hoses  408 ,  409 , which are filtered by filters  407 ,  411 , respectively. Tube  402 , containing only one inner conduit  408  (which terminates at connector  430 ), may be smaller in diameter and less expensive. As with tube  102 , tube  402  may include an accordion structure shown schematically at  404 . 
         [0038]    As discussed earlier, if the temperature and/or flow rate of the warming gas is sufficient, a separate heater for the insufflation gas (i.e., heater unit  18  in  FIGS. 1 and 3 ) may be eliminated. As a further alternative, the insufflation gas may pass through a heat exchanger associated with heating the warming gas (i.e., heater  26  in  FIGS. 1 and 3 ) prior to entry into the tubing assemblies shown in  FIGS. 2 ,  4 . In all embodiments, the heater(s) may be located at any point(s) in the system, including as a separate box, integral to the insufflator, or within the tubing “set.” 
         [0039]    As an alternative to separate tubes, multi-lumen tubes may be used in accordance with the invention. Such tubes may be extruded from polyurethane or other suitable plastic or polymeric materials.  FIG. 5A  is a cross section of a two-lumen tube;  FIG. 5B  is a cross section of a three-lumen tube; and  FIG. 5C  is a cross section of a multi-lumen tube. In  FIG. 5A , either lumen  502 ,  504  could be used for the insufflation gas or warming gas, with the warming gas being expelled at the distal end as there is no return warming gas path. In preferred configurations, the insufflation gas channel is larger in diameter and central to the tube as shown as  512  in  FIG. 5B . This allows on or more heating gas channels  514 ,  516  to ‘surround’ the central channel  512 , facilitating a return path(s) and recycling/reheating of the warming gas.  FIG. 5C  illustrates numerous warming gas channels  524  surrounding a central insufflation gas channel  522 . 
         [0040]    To enhance the efficiency of heating and/or insulation,  FIG. 5D  is a cross section of a three lumen tube with saddle-shaped air channels, and  FIG. 5E  is a cross section of a multi-lumen tube with saddle-shaped air channels. In  FIG. 5D , insufflation gas is carried by channel  532 , with channels  534 ,  536  being used for warming gas, whether or not recirculated. If tube ‘kinking’ is an issue, ribs may be added to produce a greater number of saddle-shaped channels as shown in  FIG. 5E . As with other embodiments, all of the channels  544 ,  546 ,  548 ,  550  may be used for ‘outgoing’ warming gas, or some may be used for recirculation. For example, gas through  544  may be brought back through  546 , and gas through  548  may be brought back through  550 . Once ‘brought back,’ the gas may be reheated or simply sent out a different lumen for further recirculation, depending upon temperature requirements. 
         [0041]      FIG. 6A  is a cross section of a tubing assembly utilizing the tube of  FIG. 5D , and  FIG. 6B  is an end-on view of the assembly of  FIG. 6A . This assembly includes a proximal connector  602  that interfaces to the insufflator apparatus. The connector  602  includes a hot air input port  604  and a warm air return port  606 . Insufflation gas is delivered through port  608 . The assembly includes a distal end  610  providing an air turnaround structure such that hot air is carried out by one of the channels  534 ,  536  of  FIG. 5D , with the recirculated air being returned to the insufflator through the other lumen. 
         [0042]    In the embodiment just described, the CO 2  is preheated to body temperature. The warming air is room air heated to 104 or 105 degrees on the out flow, and returning at about 80 plus degrees. The outer luminal flow is not necessarily intended to heat the inner or center lumen CO 2  but only to maintain its temperature. Such heat may be maintained by the temperature and/or speed of the flow of the warming gas. The fan (i.e.,  24 ) in the insufflator may be replaced with a pump to ensure flow speed and variable speed to maintain temperature of our circulating air.