a first embodiment of an insufflation system according to the invention makes use of fixed gas mixtures . one can perform endoscopical surgery using carbon dioxide - oxygen gas mixtures using containers of premixed gases . it is obvious that this solution offers total independability of co 2 — o 2 ratio from gas flow . flow control can be obtained using existing equipment . this embodiment has the advantage of its simplicity . the only extra equipment needed are some containers with mixtures of carbon dioxide gas and oxygen with different co 2 — o 2 ratios and a valve to switch from one mixture to another . this valve can be placed before the gas inlet of existing equipment , or it can be integrated into an apparatus for gas flow control . the valve can be pure mechanical , or electromechanical . an important limitation of this first embodiment is the fact that it is impossible to continuously vary the carbon - dioxide - oxygen ratio during an endoscopical operation . only a number of fixed ratios can be used during an operation . hereunder are two other embodiments proposed , which can overcome this limitation . fig1 gives a schematic overview of an open loop control system for mixing carbon dioxide and oxygen in a predefined ratio . the proposed solution consists of a buffer volume 6 and a controller unit 7 . the two ( one for oxygen , one for carbon dioxide ) gas inlets are equipped with electromechanical valves 4 and 5 . a periodically opening of the valves 4 and 5 , makes it possible to mix the two gases in the buffer volume 6 . if one makes sure that the opening times of the valves are rather small , or the incoming gas flow is rather small or the buffer volume 6 is rather large , then the pressure in the buffer volume 6 will remain rather constant during one period . in short , the increase in pressure in the buffer volume 6 during one period , can be neglected for small periods , large buffer volumes or small incoming gas flows . by consequence , if these conditions are met , the gas flow in the two gas inlets can be considered equal and the ratio of the two gases in the buffer volume 6 will be the same as the ratio of the opening times of the two valves . since no feedback is provided in this solution , some extra measures are necessary to make sure gas always flows in the buffer volume 6 through the valves 3 and 4 . this can be achieved by providing the pressure sensors 1 , 2 and 3 . the controller unit 7 may only periodically open valves if the pressure at sensor 3 is smaller than the pressure at the sensors 1 and 2 . the controller unit must issue a warning to the user if the pressure at sensors 1 or 2 drops below some predefined value . in order to compensate for slight differences in input pressure between 1 and 2 ( and by consequence , differences in incoming gas flow ), the controller must always maintain a predefined pressure difference between the buffer volume 6 and the incoming gas flows . this embodiment has the advantage of flexibility over the previous one . by varying the ratio of opening times of the valves 4 and 5 any carbon dioxide - oxygen ratio can be achieved . response will not be immediate , since the buffer volume 6 will introduce a delay . this embodiment can be placed before the gas inlet of existing equipment for flow control , or integrated in new equipment for flow control . this embodiment tries to overcome the problem of delayed response to different mixture ratios , as discussed above . fig2 shows a schematic overview of a third embodiment of the invention with a closed loop control system . the control unit 14 measures via the sensor 13 the composition of the gas mixture . it compensates for deviations of a predefined composition by means of the proportional valves 11 and 12 at the gas inlets . this embodiment guarantees a quasi immediate response to a request to alter the mixing ratio . pressure sensors at the inlets , to guard against a “ no pressure ” situation at the inlet are no longer necessary , since this must be the case if the controller is no longer able to obtain the requested gas composition . they may be , however , useful in order to build a more efficient controller unit . again , this embodiment can be placed before existing equipment for flow control or integrated into new equipment for flow control . it offers the advantages of improved reaction speed and size ( no buffer volume needed ) to the open loop control system . it must be stated , however , the above given embodiments are extensively simplificated for reasons of clarity , and it is further possible to add some extra sensors for pressure measurement and flow measurement , and if the controller unit is well designed , this system can implement gas mixture and flow control all together , so no extra equipment for flow control will be necessary anymore . prevention of anoxemia and of the consequences of anoxemia have been investigated mainly in obstetrics , in cardiology and in transplant surgery . in obstetrics it is obvious that prevention of anoxemia and / or of the consequences of anoxemia are important to prevent brain damage of the child . also in cardiology prevention of anoxemia and / or of the consequences of anoxemia as a result of ischemia is important to minimize the consequences of an infarction . during transplant surgery ( kidney , heart , lung , liver ) prevention of ischemia and / or anoxemia and / of of the consequences of ischemia and / or anoxemia is essential to minimize damage of the donor organ . a lower temperature obviously decreases metabolism and oxygen consumption and has been used to prevent ischemia and / or anoxemia e . g . for the mammary artery transplantation . a cooled co 2 / oxygen mixture will be used to prevent adhesion prevention . the originality of the concept is illustrated by the recent introduction of 2 insufflators with warmed co 2 up to 37 °. the invention further relates to methods for preventing adhesion by controlling anoxemia . the present invention shows that the presence of o 2 diminished the adhesion formation . this was experimentally proven by the administration of 1 , 2 . 5 , 5 ; 10 and 20 % of oxygen together with the co 2 . in these experiments , exposure of 60 min of pure co 2 increased the adhesion scores 4 fold in comparison with an exposure of 10 min . from a final concentration of 5 % oxygen onwards , this adhesiogenic effect of co 2 was completely abolished . also visually the appearance of the lesions following pure co 2 and following a co 2 / oxygen mixture was obviously different , the latter looking much healthier . these above mentioned experiments demonstrate clearly that prevention of anoxemia reduces adhesion formation by or during co 2 pneumoperitoneum , which principle is used as a basis in developing an insufflation system which delivers a controlled o 2 / co 2 mixture . the invention further relates to a method according to the claims 1 - 7 . as an illustration of part of the method and of the effectiveness of the method according to claim 6 , as an example , in the following a series of experiments in rabbits is described that show that co 2 is an independent adhesiogenic factor . co 2 causes not only ph changes . taking into account the relative pressures , it was found that the peritoneal lining was anoxic during the pneumoperitoneum , and that this was a direct cause of cell damage and adhesion formation . co 2 in pneumoperitoneum is generally used because of safety . indeed the solubility and high exchange rate in the lungs make it the safest gas available with respect to gas embolism . co 2 pneumoperitoneum has complex systemic and local effects depending on the duration of the application and intra - abdominal pressure . systematic effects of co 2 pneumoperiteum have been described , such as changes in acid - base balance ( moten , m ., et al ., 1973 , volz , j ., et al ., 1996 ), cardiopulmonary system ( barnett , r . b ., et al ., 1992 ; ho , h . s ., et al ., 1993 ; liu , s d . y ., et al ., 1991 ) inmunologic and endocrine systems ( volz , j ., et al ., 1996 ). for this reason , other gases have been investigated . nitrous oxide or air have been used but they are potentially combustible or explosive in presence of cautery ( robinson , j . s ., et al ., 1975 ; esposito , j . m ., 1975 ; el - minawi , m . f ., et al ., 1981 ). helium is physiologically inert , nonexplosive but it is very expensive ( leighton , t . a ., et al ., 1992 ; bongard , f . s ., et al ., 1993 ; rademaker , b . m ., et al ., 1995 ). locally , the co 2 pneumoperitoneum produces disturbances of the peritoneal surface . it was clinically demonstrated that co 2 pneumoperitoneum produces intense intraperitoneal acidosis ( volz , j ., et al ., 1997 ). moreover , co 2 exposure may have adverse effects on peritoneal microcirculation and cell - protective systems ( buhur , a ., et al ., 1997 ). our observation that co 2 pneuoperitoneum increases adhesion formation , could be explained by acidosis or by local anoxemia . to test the latter hypothesis , experiments were carried out with variable o 2 concentrations . all animals received two standard co 2 laser injuries . a non opposing lesion was inflicted in the retro - uterine space , i . e . on the posterior utero - vaginal wall , consisting of a 2 cm 2 ; vaporization of the superficial layers with co 2 laser . in addition , an apposing lesion was performed in the oviduct and pelvic side wall , consisting of a 2 cm 2 vaporization , on both sides . the time required to induce the lesions varied from 3 to 7 minutes . animals were assigned randomly on a daily base , to one of the following seven experimental groups . first and second groups were considered control groups . in group 1 , using conventional co 2 pneumoperitoneum , the total duration of the procedure was restricted to 10 minutes . in group 2 , the pneumoperitoneum was maintained for 70 minutes , to demonstrate the effect of co 2 pneumoperitoneum . in groups 3 , 4 , 5 , 6 and 7 , duration of pneumoperitoneum was also 70 minutes , but the pneumoperitoneum was maintained with a mixture of co 2 and increasing amounts of o 2 ( 1 %, 2 . 5 %, 5 %, 10 % and 20 %, for groups 3 , 4 , 5 , 6 and 7 respectively ). adhesions were evaluated by laparoscopy after one week . all second look laparoscopies were videotaped , and subsequently scored blindly by two investigators , taking into account extent ( 0 to 4 points ), type ( 0 to 3 points ), tenacity ( 0 to 3 points ) and inflammatory reaction ( 0 to 3 points ) at the injury and at de - novo siteds . sixty five new zealand white rabbits weighing between 2150 and 3000 grams were operated with a standard 3 puncture laparoscopy . standard surgical injuries were inflicted with co 2 laser ( sharplan 1060 : sharplan , tel aviv , israel ) with a spot diameter of 1 mm and a power setting of 10 watts in the continuous superpulse mode . pneumoperitoneum was created and maintained with two thermoflators ® ( karl storz - endoscope , belgium ), one for co 2 and one for o 2 . the output of both insufflators was mixed in a mixing chamber , humidified and warmed . the insufflation pressure was 10 cm of water and the intra - abdominal flow rate 20 l / min . it is obvious that all means in contact with o 2 are adapted therefor . results are summarized in table 1 and fig3 . adhesion score was higher in group 2 than in group 1 confirming the effect of co 2 . using increasing concentrations of oxygen , the amount of adhesions decreased progressively . groups 2 and 3 presented higher total adhesion scores ( mean 17 . 5 ± 6 . 7 and 15 . 8 ± 5 . 2 for groups 2 and 3 respectively , p = ns ). mean total adhesion scores for 5 %, 10 % and 20 % of oxygen concentration ( 5 . 3 ± 3 . 8 , 6 . 6 ± 4 . 4 , 6 . 3 ± 2 . 5 , respectively ) was comparable with the control group 1 , consisting in only 10 minutes procedure ( 4 . 5 ± 3 . 7 , p = ns ). ( fig3 ). this decrease in total adhesion score with the addition of o 2 was not only observed at the lesion sites , i . e . opposing lesion in tube / side wall ( p = 0 . 0014 ) and non opposing lesion in the pouch of douglas ( p = 0 . 0002 ), but also de novo adhesions around the opposite tube ( p = 0 . 0001 ) ( fig4 ). moreover , this reduction in total score was obviously produced by a reduction in all items of the scoring system , such as inflammation , extent , tenacity and type ( fig5 ). laparoscopic surgery requires a pneumoperitoneum to provide adequate space to work . co 2 gas is the most common distending medium in laparoscopic surgery because its high solubility and exchange rate in the lungs . co 2 absorbed across the peritoneal surface can cause systematic effects such as respiratory acidosis , hypercarbia and arrhytmia . locally , co 2 induces severe acidosis and some anoxemia in the peritoneal surface . these disadvantages of co 2 pneumoperitoneum have led investigators to look for other gases . nitrous oxide and air have been tested but they can be dangerous in presence of cautery . gasless laparoscopy is another alternative . the disadvantage is a more difficult surgical procedure , since the visceras can interfere with a good visualization . helium is nonexplosive , inert and nontoxic but is expensive . our data suggest that the addition of oxygen is useful in the preventing of adhesion formation .
a method of treating or preventing adhesion formation during or following a surgical procedure comprising administering to a patient in need thereof at least one medicament selected from the group consisting of potassium channels ; modulators of macrophage activation and leucocyte attraction through cytokines , or their inhibitors , antibodies or inhibitors blocking the effect of vegf expression ; prostaglandin e1 ; free radical scavengers , lipid peroxysomes ; pregnatrienes ; calcium antagonists ; hypoxia ; acidosis ; mp ; dopamine ; and atp - mgcl 2 , wherein the method prevents adhesion formation by preventing anoxemia .