Abstract:
An apparatus for insufflating a body cavity with an insufflation gas comprising an insufflation device for delivering the insufflation gas to the body cavity. To detect possibly critical states in the body cavity, the apparatus is designed to withdraw a measuring gas from the body cavity. A measuring device having a gas sensor serves for measuring an additional substance contained in the measuring gas in addition to the insufflation gas and for outputting a measuring signal as a function of the additional substance.

Description:
CROSS-REFERENCE OF PENDING APPLICATION 
     This application is a continuation of pending international application PCT/EP2003/007809 filed on Jul. 18, 2003 which designates US and which claims priority of German patent application No. 102 33 861.2 filed on Jul. 19, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus for insufflating a body cavity with an insufflation gas, comprising an insufflation device having a delivery line for delivering the insufflation gas to the body cavity. The invention further relates to a method for insufflating a body cavity with an insufflation gas, said method comprising the following step: provision, by an insufflation device, of an insufflation gas for delivery to a body cavity. 
     Such an insufflation apparatus and such a method are known, for example, from the article entitled “Die Laparoskopie in der Gynätkologie” by K. Semm in “Geburtshilfe und Frauenheilkunde”, volume 11, November 1967. With the aid of the insufflation device, the so-called insufflator, an insufflation gas, usually carbon dioxide gas (CO 2  gas), is introduced into a body cavity of a human or animal, for example into the abdominal cavity. The insufflation gas inflates the abdominal cavity so as to create the viewing and operating space which is needed between the internal organs and the abdominal wall in order to permit examination or surgery with the aid of an endoscope. 
     In addition to the insufflation gas, it is also possible that other gases will collect in the abdomen, for example nitrous oxide (N 2 O) and/or methane (MH 4 ), which can result in explosive gas mixtures within the abdomen. Gas explosions may therefore occur, especially in connection with electrosurgical procedures. 
     Nitrous oxide is used for anaesthesia. It can diffuse from the bloodstream into the intra-abdominal cavity. If a nitrous oxide concentration of ca. 29% is exceeded, there is an increased risk of explosion of the gas mixture located in the abdominal area. The diffusion behavior of nitrous oxide in the abdominal area of pigs is known from the article “Nitrous Oxide Fraction in the Carbon Dioxide Pneumoperitoneum During Laparoscopy Under General Inhalation Anaesthesia in Pigs” by P. Diemunsch, Klaus D. Torp, T. Van Dorsselaer, D. Mutter, A. M. Diemunsch, R. Schaeffer, G. Teller and A. Van Dorsselaer. The article describes how, with the aid of a catheter and a gastight syringe, samples were taken from the abdominal cavities of pigs at ten-minute intervals. Nitrous oxide was used for anaesthesia. The abdominal cavities were inflated with carbon dioxide gas. The behavior of the nitrous oxide concentration in the abdomen was observed over a particularly long observation period. After approximately two hours, the critical limit of 29% nitrous oxide concentration is reached. After about nine hours, the nitrous oxide concentration rises to a value of just over ca. 66%. 
     The measuring method described in the article involving a catheter and a gastight syringe may well be acceptable for a scientific test. However, such an approach is not suitable for a typical endoscopic procedure in which the patient must be treated with great care and in which the operating physician must focus his concentration entirely on the patient. 
     A further problem in intra-abdominal interventions is that the patient&#39;s intestine may inadvertently be damaged or perforated. This danger is particularly great when using electrosurgery instruments. Damage to the intestine results in the escape of intestinal gases which contain methane. The methane can cause explosions. However, a far greater problem is that of the damage to the intestine not being detected during the intervention. In the postoperative period, this can lead to serious complications, or even to the death of the patient. However, an analysis of the gases in the abdominal area in the manner known from the abovementioned article is on account of the complicated collection of samples not really practicable with respect to methane. 
     It is therefore an object of the invention to permit early and reliable detection of any complications which may occur during an intervention in which an insufflation gas is insufflated into a body cavity, in particular into the abdominal cavity, of a human or animal. 
     SUMMARY OF THE INVENTION 
     According to the invention, the object is achieved by the fact that, in the apparatus mentioned at the outset, the insufflation device has a withdrawal line for withdrawing a measuring gas from the body cavity, and by a measuring device for measuring an additional substance contained in the measuring gas in addition to the insufflation gas and for outputting a measuring signal as a function of the additional substance, wherein the measuring device comprises a gas sensor. 
     Correspondingly, in the method mentioned at the outset, the object is achieved by the following further steps: providing a measuring gas, withdrawn from the body cavity, by the insufflation device, for a measuring device; measuring an additional substance contained in addition to the insufflation gas in the measuring gas and outputting a measuring signal as a function of the additional substance. 
     An underlying concept of the invention is the combined realization of the insufflation of the body cavity with an insufflation gas and the analysis of the gas mixture located there. The insufflation device and the measuring device are used jointly. During the intervention in the body cavity, in particular in an abdominal cavity, the physician carrying out the procedure is kept aware of the gas conditions present in said cavity at all times, as a result of which critical situations during and after the intervention can be avoided. 
     For example, it is possible to determine whether an explosive gas mixture has collected in the abdomen. Accordingly, the delivery of the insufflation gas can for example be increased and the body cavity at the same time ventilated, as a result of which the concentration of combustible gases in the abdomen decreases. A possible explosion can be reliably avoided in this way. 
     Any damage to the patient&#39;s intestine can be detected during the intervention. Countermeasures can be taken immediately, as a result of which postoperative complications, possibly even including the death of the patient, can be avoided. 
     A further important aspect of the invention is ventilation of the body cavity by withdrawal of the measuring gas. This way, the formation of explosive gas mixtures in the body cavity is prevented. 
     In a modular concept, measuring devices of different configurations can readily be used. For example, depending on requirements, a measuring device for the detection of nitrous oxide and/or a measuring device for the determination of intestinal gases, for example methane, can be used on the insufflation device according to the invention. In addition, the insufflation device can also be used on a stand-alone basis that is to say without a measuring device coupled to it, if in individual cases it is not necessary to analyze the gas mixture located in the abdominal area. The insufflation device can then even operate in a purely ventilating mode in which the withdrawn measuring gas, which in principle here forms a ventilation gas, is withdrawn from the body cavity only for ventilation purposes and is not analyzed for additional substances. 
     In one embodiment of the invention, the insufflation device comprises an insufflation cannula which at least partially houses both the delivery line and the withdrawal line. 
     This measure has the advantage, in handling terms, that only a single insufflation cannula is to be introduced into the body cavity. The patient is accessed at just one site by the introduction of the insufflation cannula. In principle, however, it would also be possible to use separate cannulas in each case for delivering the insufflation gas to the body cavity and for withdrawing the measuring gas from the body cavity. 
     In a further embodiment of the invention, the insufflation device comprises a tubing which at least partially houses both the delivery line and the withdrawal line. 
     This measure too is advantageous with respect to handling. A number of cannulas, for example a delivery cannula for delivering the insufflation gas to the body cavity and a withdrawal cannula for withdrawing the measuring gas from the body cavity, can be attached to the tubing which is, for example, a tubing with multiple lumens. However, it is particularly advantageous to use a “combined” insufflation cannula according to the aforementioned embodiment of the invention in which a delivery line as well as a withdrawal line is provided. 
     In a further embodiment of the invention, the measuring device comprises an alarm device for outputting an alarm signal when a predetermined limit value of the additional substance detected by the measuring device is exceeded. 
     Correspondingly, the step of outputting a measuring signal comprises outputting an alarm signal when a predetermined limit value of the additional substance detected by the measuring device is exceeded. 
     By means of this measure, the operating physician directly obtains an alarm signal if a critical situation arises in the body cavity being treated, for example if an explosive gas mixture has formed or if the patient&#39;s intestine has been damaged. 
     The following embodiments of the invention concern advantageous configurations of the gas sensor. 
     In an embodiment of the invention, the gas sensor is a gas chromatograph. 
     The gas chromatograph is, for example, a capillary gas chromatograph. A gas chromatograph permits a particularly accurate analysis of the measuring gas. 
     In a further embodiment of the invention, the gas sensor is a mass spectrometer. 
     This embodiment of the invention also permits an exact analysis of the measuring gas. 
     In a further embodiment of the invention, the gas sensor is designed to detect whether the measuring gas is combustible. 
     With this measure, explosive gas mixtures in the treated body cavity can be effectively avoided. In this connection, it is possible that the gas sensor does not determine in detail the nature and concentration of combustible gases in the measuring gas, but instead only determines whether the measuring gas as a whole is combustible. 
     In a further embodiment of the invention, the gas sensor is designed to detect a compound selected from the group consisting of methane (CH 4 ), nitrous oxide (N 2 O) and mixtures thereof. 
     As has already been explained, the detection of methane in the measuring gas permits early detection of possible damage to the intestine. These gases are primarily responsible for the fact that burns or even explosions can occur in the body cavity. 
     It will be appreciated that the gas sensor can also be designed to determine further additional substances, for example different types of intestinal gases, oxygen (O 2 ), the insufflation gas, for example carbon dioxide gas (CO 2 ), hydrogen or the like. It is also possible to detect medicaments which have been administered to the patient and which are contained in the measuring gas. 
     In a further embodiment of the invention, the insufflation device comprises a pressure measuring device for measuring at least one of a pressure of the insufflation gas delivered to the insufflation cannula and of the measuring gas. 
     The pressure measuring device can, for example, be included in the insufflation device. However, it preferably forms a component part of the measuring device. In principle, however, it would also be possible to provide a pressure measuring device in the insufflation device as well as in the measuring device. A pressure measuring device is advantageous particularly with respect to the insufflation device. On the basis of the measuring results determined by the pressure measuring device, the insufflation device can monitor the pressure conditions in the body cavity and, if appropriate, deliver more or less insufflation gas to the body cavity. 
     In a further embodiment of the invention, the measuring device comprises a quantity measuring device for measuring a quantity of the measuring gas. 
     Just like a pressure measuring device according to the aforementioned embodiment of the invention, a quantity measuring device is able to control and monitor the pressure and quantity conditions of the insufflation gas in the body cavity. 
     In a further embodiment of the invention, the insufflation device is designed to control at least one of a quantity and the pressure of the insufflation gas to be delivered to the body cavity. 
     This measure is particularly advantageous in connection with the two aforementioned measures. The insufflation device evaluates the measuring results from the quantity measuring device and/or from the pressure measuring device and accordingly controls the delivery of the insufflation gas in the direction of the body cavity. 
     In a further embodiment of the invention, the insufflation device is designed to control a delivery of the insufflation gas to the body cavity as a function of the measuring signal generated by the measuring device relating to the additional substance. 
     Correspondingly, the method according to the invention is distinguished by the delivery of the insufflation gas to the body cavity being controlled as a function of the measuring signal relating to the additional substance. 
     Thus, for example, the delivery of the insufflation gas can be advantageously increased in order to lower the proportion of combustible gases in the body cavity in relation to the insufflation gas. 
     In this connection, it should also be noted that the insufflation device can in principle also be designed to control the withdrawal of the insufflation gas from the body cavity as a function of the measuring signal generated by the measuring device. With this measure too, it is possible to avoid potentially undesirable gas mixture situations in the body cavity. 
     In a further embodiment of the invention, the insufflation device is designed to deliver a substantially continuous stream of the insufflation gas to the body cavity. 
     Correspondingly, the step of providing an insufflation gas comprises generating a substantially continuous stream of the insufflation gas for insufflating the body cavity. 
     It would be possible, in principle, also to deliver the insufflation gas to the body cavity discontinuously, for example in the form of one or more pump impulses. However, such pump impulses are often associated with noise, which disturbs the operating physician during the endoscopic intervention. By contrast, a continuous delivery of the stream of insufflation gas to the body cavity is quiet, if not completely silent. In addition, vibrations, which possibly also impact the patient, are reduced or completely avoided. 
     In a further embodiment of the invention, the insufflation device is designed to withdraw a substantially continuous stream of the measuring gas. 
     Correspondingly, the step of providing a measuring gas comprises withdrawing a substantially continuous stream of the measuring gas. 
     Here, the same principle applies as in the aforementioned measure, namely that a continuous stream of gas is comparatively quiet and reduces any mechanical loads on patient and insufflation device. 
     “Continuous” in the context of the two aforementioned measures signifies that the respective stream of gas is not interrupted or is only rarely interrupted. Nevertheless, the gas volume delivered, that is to say the gas stream, can still be increased or decreased. 
     In a further embodiment of the invention, the apparatus provides an amount of measuring gas capable of ventilating the body cavity. 
     A deliberate gas leakage is thus provided in order to ventilate the body cavity. This ventilation prevents the formation of a potentially explosive gas mixture in the body cavity. It will be appreciated that the deliberate ventilation of the body cavity is to be advantageously combined with a correspondingly high delivery of insufflation gas to the body cavity. The withdrawn measuring gas is thus replaced by freshly delivered insufflation gas in the body cavity. It has been found that the withdrawal of approximately half a liter to one liter of measuring gas per minute is expedient. In this connection, it should also be mentioned that the measuring gas can in fact be pure insufflation gas if, for example, no nitrous oxide, intestinal gas or other substance diffuses into the insufflation gas insufflated into the body cavity. 
     A minimum gas flow for ventilating the body cavity, in particular a continuous stream of measuring gas, according to the advantageous embodiment of the invention makes it possible to deliver a comparatively large stream of insufflation gas to the body cavity. The insufflation gas can be at a comparatively high pressure. It is therefore possible to use thinner insufflation tubings and thinner insufflation cannulas, which are easier to handle and impose less stress on the patient. An insufflation cannula according to the invention and an insufflation tubing according to the invention, each provided with a delivery line for the insufflation gas and a withdrawal line for the measuring gas, are therefore comparatively thin, although two or more lines are provided. A multilumen insufflation cannula of this kind and a multilumen insufflation tubing of this kind are not thicker, or are at any rate not much thicker, than a conventional insufflation cannula and conventional insufflation tubing in which in each case only one line is provided. An insufflator with a multilumen insulation cannula and/or a multilumen insufflation tubing, which are designed for delivering an insufflation gas to a body cavity and at the same time for withdrawing an evacuation gas from the body cavity, in principle already constitute an invention in themselves. 
     In a further embodiment of the invention, the measuring device comprises a withdrawal pump for withdrawing the measuring gas. 
     Such a withdrawal pump can be provided both in the insufflation device and also in the measuring device. The withdrawal pump, which for example can be a small suction pump, ensures a minimum flow of measuring gas from the body cavity. The delivery volume of the pump can be adjustable. 
     It will be appreciated that the features mentioned above and the features still to be explained below can be used not only in the stated combinations, but also in other combinations or in isolation, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is now described and explained in greater detail below on the basis of selected illustrative embodiments and with reference to the attached drawings, in which: 
         FIG. 1  shows a perspective view, very diagrammatically in part, of a first illustrative embodiment of an apparatus according to the invention for insufflating a body cavity with an insufflation gas, 
         FIG. 2  shows a cross section, along a line II-II, of an insufflation tubing of the apparatus according to  FIG. 1 , 
         FIG. 3  shows a cross section, along a line III-III, of an insufflation cannula of the apparatus according to  FIG. 1 , and 
         FIG. 4  shows a perspective view, very diagrammatically in part, of a second illustrative embodiment of an apparatus according to the invention for insufflating a body cavity with an insufflation gas. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIGS. 1 through 3 , an apparatus for insufflating a body cavity with an insufflation gas is indicated in its entirety by reference number  10 . 
     The apparatus  10  follows a modular concept in which a measuring device  14  can be connected to an insufflation device  12 . In the drawing, the measuring device  14  is shown in the state when connected to the insufflation device  12 . 
     The insufflation device  12  is used for delivering an insufflation gas  16  to a body cavity  18 , for example to the abdominal area, of a human or animal. In addition, the insufflation device  12  withdraws a measuring gas  20  from the body cavity  18  and transports this measuring gas  20  to the measuring device  14 . To transports both gases  16 ,  20 , the insufflation device  12  is provided with a combined delivery and withdrawal device  22  which, for the sake of simplicity, is referred to below as “delivery device  22 ”. The delivery device  22  is attached to a preparation device  24 , with which it can be connected in a releasable manner. The preparation device  24  is used for delivering the insufflation gas  16  to the delivery device  22 . With the preparation device  24 , it is possible to control the quantity and pressure of the insufflation gas  16  delivered to the delivery device  22 . In addition, the preparation device  24  prepares the insufflation gas  16 . In the illustrative embodiment, the preparation device  24  charges the insufflation gas  16  with a humidifying liquid  26 . 
     The measuring device  14  is used to analyze the measuring gas  20 . The measuring device  14  analyzes the measuring gas  20  and detects one or more additional substances contained in the measuring gas  20 , for example nitrous oxide, methane or the like. 
     The functioning of the apparatus  10  is explained in greater detail below: 
     The insufflation gas  16 , which can for example be carbon dioxide gas (CO 2 ), flows from a mainly cartridge-like storage vessel  28  through a line  30  to a preparation chamber  32  of the insufflation device  12 . The storage vessel  28  is connected to the line  30  via a releasable connection, for example a screw-type or bayonet-type connection  34 . Arranged on the line  30  there is a valve arrangement  36  with which the stream of insulation gas flowing into the preparation chamber  32  can be adjusted. 
     The insufflation gas  16  flows from the preparation chamber  32  and through a line  38  to a heater  40 . The heater  40  is used to heat the insufflation gas  16  so that the latter is optimally adapted to the microclimate conditions in the body cavity  18 . The heater  40  is releasably connected via an attachment piece  42  to an attachment device  44  of the delivery device  22 . The attachment piece  42  and the attachment device  44  form, for example, a screw connection and/or plug connection. 
     From the attachment device  44 , the insulation gas  16  flows through a delivery line  46  of a tubing  48  to an insulation cannula  50 . The insufflation gas  16  flows through the insufflation cannula  50  via a delivery line  52  and emerges from the insulation cannula  50 , at its front end remote from the tubing  48 , into the body cavity  18 . There, the insulation gas  16  forms an inflated space, so that an operating physician  54  can perform examinations, operations or the like with the aid of an endoscope  56 . 
     In such an intervention, nitrous oxide (N 2 O), for example, is used to anaesthetize the patient. It is further conceivable for the patient&#39;s intestine to be damaged during the intervention, as a result of which intestinal gases, in particular methane, pass into the body cavity  18 . These additional substances (not detailed in the figure) can mix with the insufflated insufflation gas  16 . Moreover, the insufflation gas  16  located in the body cavity  18  can be charged with particulate and/or liquid additional substances, for example with humidity present in the body cavity  18 . Some of the gas located in the body cavity  18  is withdrawn from said body cavity  18  to the measuring device  14  with the aid of the delivery device  22 , insofar as the latter constitutes a withdrawal device or includes a withdrawal device. The withdrawn gas constitutes the measuring gas  20 . 
     The measuring gas  20  flows through a withdrawal line  58  of the insufflation cannula  50  to a withdrawal line  60  of the tubing  48 , which is, for example, a multilumen tubing. The withdrawal line  60  opens into the attachment device  44  to which the measuring device  14  is connected via an attachment piece  62  of the measuring device  14 . The attachment piece  62  and the attachment device  44  are, for example, screwed onto one another and/or plugged into one another. 
     Arranged on the attachment device  44  there is an outlet  61  which communicates with an inlet  63  of the attachment piece  62 . The measuring gas  20  flows through the outlet  61  and the inlet  63 . The measuring gas  20  flows from the attachment device  44  via the attachment piece  62  and via a line  64  to a measuring chamber  66  of the measuring device  14 . Arranged on the line  64  there is a withdrawal pump  68  which sucks in the measuring gas  20  and pumps it into the measuring chamber  66 . The withdrawal pump  68  conveys a continuous stream of measuring gas from the body cavity  18  to the measuring chamber  66 . 
     It will be appreciated that the withdrawal pump  68  can in principle also operate in a discontinuous operating mode, for example in a pulsed mode or the like. 
     The measuring device  14  has an additive measuring device  70 , a quantity measuring device  72  and a pressure measuring device  74 . The devices  70 ,  72 ,  74  are arranged on the measuring chamber  66 , the important point being that they come into contact there with the measuring gas  20 . 
     The additive measuring device  70  includes, for example, a gas sensor, a gas chromatograph and/or a mass spectrometer. It will be appreciated that it is also possible for just one of the aforementioned instruments to be present in the additive measuring device  70 . In a simple embodiment, for example, a gas sensor is provided which determines whether the measuring gas  20  is combustible and/or has an explosive consistency. Additional substances can also be present in the measuring gas  20  in addition to the insufflation gas  16 , for example nitrous oxide, methane or the like, which can be determined by the additive measuring device  70 . 
     The quantity measuring device  72  and the pressure measuring device  74  measure the quantity and the pressure, respectively, of the measuring gas  20 . On the basis of the measuring values thus determined, the quantity and pressure ratios in the body cavity  18  can be determined. However, the determined measuring values can also be used to control and monitor the delivery of the insufflation gas  16  to the body cavity  18 . An evaluation device  76  of the measuring device  14  serves to evaluate the measuring values determined by the measuring devices  70 ,  72 ,  74 . 
     The evaluation device  76  has, for example, a display  78  and a speaker  80  as output devices with which can output the values determined by the devices  70 ,  72 ,  74 . The speaker  80  is used, for example, to output an alarm sound or other alarm signal if a value determined by the additive measuring device  70  exceeds a predetermined limit value, for example if the measuring gas  20  is explosive. To input such limit values or for other operations, input devices  82  of the evaluation device  76  are used, which input devices  82  include, for example, function keys or the like. The measuring gas  20  can flow out of the measuring chamber  66  through an outlet  84 . 
     A valve arrangement (not shown) for closing the outlet  84  can be arranged at this outlet  84 . In any event, the body cavity  18  can be ventilated with the aid of the delivery and withdrawal device  22  and the measuring device  14 . 
     The evaluation device  76  has a transmitter device  86  with which it can transmit messages to a receiver device  88  of a control device  90  of the insufflation device  12 . The devices  86 ,  88  are connected to one another, for example, via one or more electrical lines and a releasable plug connection (not shown). The signals can in principle be each of the measuring signals generated by measuring devices  70 ,  72 ,  74 . For example, a measuring signal  92  generated by the additive measuring device  70  is transmitted to the control device  90 . The measuring signal  92  is dependent on one or more additional substances which are contained in addition to the insufflation gas  16  in the measuring gas  20 , for example on the contentn of nitrous oxide in the measuring gas  20 . 
     The control device  90  serves to control and monitor the insufflation device  12 . It has input devices  94 , for example function keys, and output devices  96 , for example a display, LED or the like. In the present case, the control device  90 , like the evaluation device  76 , is a microprocessor control. A microprocessor  98  is indicated diagrammatically for the control device  90  only. 
     The control device  90  controls the valve arrangement  36  in order to influence the insufflation gas  16  to be delivered to the body cavity  18 . 
     In addition, the control device  90  controls and monitors a humidifying apparatus  100  used for humidifying the insufflation gas  16 . Alongside the preparation chamber  32  there is a cartridge-like storage vessel  102  from which the humidifying liquid  26  passes via a line  104  to an injector apparatus  106  and to the humidifying apparatus  100 . The injector apparatus  106  has an injector outlet  108  opening into the preparation chamber  32 . The injector apparatus  106  sprays a humidifying mist  110  through the injector outlet  108 , and this humidifying mist  110  is entrained by the insufflation gas  16  and conveyed to the body cavity  18 . There, the humidifying liquid  16  ensures advantageous microclimate conditions which result in a reduction in postoperative complications. Arranged on the line  104  there is a valve arrangement  112  with which the flow of the humidifying liquid  16  in the line  104  can be adjusted. The storage vessel  102  is connected to the line  104  via a releasable connection  116 , for example a screw-type and/or plug-type connection. 
     Arranged on the line  38  there is a sensor  116  which determines the quantity and the pressure of the insufflation gas  16  conveyed from the insufflation device  12  to the body cavity  18 . On the basis of the measuring values transmitted from the sensor  116  to the control device  90 , the latter can control the quantity of the insufflation gas  16  conveyed to the body cavity  18 . In addition, the control device  90  evaluates the measuring signal  92  coming from the measuring device  14 . If, for example, the concentration of one or more additional substances contained in the measuring gas  20  increases in an undesired manner, the control device  90  can increase the stream of the insufflation gas  16  to the body cavity  18 . 
     In this connection, it is possible in principle for the control device  90  to govern the measuring device  14  in an advantageous manner. For example, the control device  90  can govern the withdrawal pump  68  as a function of the stream of insufflation gas being delivered to the body cavity  18 , in which case it transmits corresponding control signals via a control line  99 . If more insufflation gas  16  is pumped to the body cavity  18 , the withdrawal pump  68  correspondingly increases its delivery rate, and vice versa. 
     From the cross section in  FIG. 2 , it will be seen that the tubing  48  comprises the two lines  46  and  60  separate from one another. The tubing  48  is made of flexible material, for example rubber or plastic. The lines  46 ,  60  are formed within an outer jacket  118  and are separated from one another by a dividing wall  120 . The tubing  48  preferably has a substantially circular cross section. The lines  46  and  60  each have semicircular cross sections. It will be appreciated that other cross-sectional shapes are also possible. Moreover, in contrast to the illustrative embodiment, the lines  46  and  60  can also have cross sections of different sizes. It is also possible for the tubing to comprise more than two lines. 
       FIG. 3  shows a cross section through the insufflation cannula  50  which is, for example, a trocar. In the insufflation cannula  50  there also are two lines, namely the delivery line  52  and the withdrawal line  58 . The insufflation cannula  50  is made of metal, for example. In the illustrative embodiment, it has a similar cross-sectional configuration to that of the tubing  48 , i.e. the two lines  52 ,  58  are formed within an elongate and substantially circular-cylindrical housing  122  and are separated from one another by a dividing wall  124 . 
     The two lines  52 ,  58  preferably emerge directly alongside each other at the end of the insufflation cannula  50  remote from the tubing  48 . In principle, however, it would also be possible to provide an insufflation cannula in which, as in the illustrative embodiment, a number of lines are provided, but in which these lines emerge from the insufflation cannula at positions relatively far apart from one another, at any rate not immediately adjacent. For example, as in the illustrative embodiment, the outlet of an insufflation line could be arranged at the front end of an insufflation cannula, whereas an inlet or a number of inlets for a measuring gas line could be arranged laterally on the insufflation cannula. 
     In  FIG. 4 , a second illustrative embodiment of an apparatus according to the invention for insufflating a body cavity with an insufflation gas is indicated in its entirety by reference number  150 . 
     The apparatus  150  mainly has similar components to those in the apparatus  10  according to  FIGS. 1 through 3 . Those components which have a similar function are indicated in  FIG. 4  with the same reference numbers as in  FIGS. 1 through 3  and, for the sake of simplicity, are not described in detail below. 
     In contrast to the apparatus  10 , the apparatus  150  does not follow a modular design, and instead it forms an integrated solution in which a measuring device  152  is integrated permanently into the apparatus  150 . The apparatus  150  has, for example, a housing (not shown in the figure) in which the measuring device  152  is contained. The measuring device  152  is otherwise basically similar to the measuring device  14 , but in contrast to the latter it does not have its own evaluation device comparable to the evaluation device  76 . 
     In the apparatus  150 , the functions of an evaluation device are performed by a control device  154  which otherwise has basically the same functions as the control device  90 . 
     Instead of the delivery device  22 , the apparatus  150  has a delivery and withdrawal device  156  which, for simplicity, is referred to below as “delivery device  156 ”. 
     The delivery device  156  comprises a tubing  158  in which a delivery line  160  is provided for delivering the insufflation gas  16  to an insufflation cannula  162 . In contrast to the insufflation cannula  50 , there is only one line in the insufflation cannula  162 , namely a delivery line  164  which is connected to the delivery line  160  and which opens into the body cavity  18  at the end of the insufflation cannula  162  remote from the tubing  158 . 
     In addition to the delivery line  160 , the tubing  158  also has a withdrawal line  166  which is not however connected to the insufflation cannula  162  but instead to a withdrawal cannula  168 . Through the withdrawal cannula  168  which, like the insulation cannula  162  in the position of use shown in  FIG. 4 , engages in the body cavity  18 , it is possible to remove a gas from the body cavity  18 , which is mainly the measuring gas  20 . The withdrawal cannula  168  forms a withdrawal device. The measuring gas  20  flows from the withdrawal cannula  168  through the withdrawal line  166  to the measuring device  152  which analyzes the measuring gas  20  in the manner already discussed and ensures controlled evacuation of the body cavity  18 . 
     In this connection, it should be noted that the measuring devices  14  and  154  can be operated in different operating modes. For example, they can be operated in a purely analytical mode, in which relatively small quantities of measuring gas  20  are sufficient for analysis and correspondingly small quantities of measuring gas  20  need to be withdrawn from the body cavity  18 . However, a purely ventilating mode is also possible, in which the measuring gas  20  serves mainly to ventilate the body cavity  18 . A relatively large quantity of measuring gas  20  is transported from the body cavity  18 . The measuring gas  20  is not analyzed, or is analyzed only at random. However, a combined analysis and evacuation mode is preferred in which the measuring gas  20  serves on the one hand to evacuate the body cavity  18  and on the other hand is analyzed continuously or at short intervals.