the detailed description begins with a general description of the invention and then concludes with the illustrative embodiments of the invention illustrated in fig1 - 6 , which do not however limit the invention . the gas flow reversing element according to the invention serves for the use of a gas supply under excess pressure , in particular oxygen , for selectively generating a gas flow from or to a line connector , in particular for connection to a catheter or cannula that can be inserted into the airway of a patient . it is designed as a main piece with a branching piece , which main piece connects a pressure connector , for connection to the gas supply , to at least one closable outlet opening , and which branching piece leads from the main piece to a line connector . a nozzle , particularly an injector nozzle , is configured and arranged in the main piece in such a way that , by a gas flow flowing from the pressure connector through the nozzle to the outlet opening , a gas flow can also be generated in the branching piece in the direction of the outlet opening , and , from the branching piece as far as the outlet opening , the main piece has a flow cross section that is substantially constant or that increases in the direction of the outlet opening . for the nozzle , it is in fact possible to choose any design principle that generates a suction effect by means of a gas flow . however , the principle of a gas jet pump is preferably used here . particularly with a view to aspirating large volumes of gas , it is important to manage as far as possible without any reduction in cross section in the main piece between the branching piece and the outlet opening . there are various possible ways of achieving a good function of the gas flow reversing element . it has been found in tests that there are nozzle and mixing channel dimensions that show good results at subsonic speed , but it is also possible to use dimensions for a nozzle outlet speed in the supersonic range . experiments have shown that in one embodiment of the invention the spread of the gas stream after emergence from the nozzle into a mixing channel can be divided into three characteristic areas , namely the widening area , the eddy area , and the area of uniform movement . the widening area begins directly at the outlet of the nozzle . at this location , the stream of air is unable to follow the sharp edge of the nozzle and widens along a length corresponding to ca . 3 to 5 times the diameter of the nozzle . the widening area is followed by the eddy area , where a turbulent flow forms in the gas stream . in this area , the inflowing gas is mixed with the gas located in the main piece and is transported together with this in the direction of the outlet opening . the eddy area generally forms along a length that corresponds to ca . 5 to 7 times the diameter of the nozzle . the eddy area is followed by the area of uniform movement where the inflowing gas is mixed homogeneously with the gas previously located in the main piece . here , there are virtually no turbulent flows any longer , and instead the gas or gas mixture moves uniformly in the direction of the outlet opening . thus , the mixing channel should at least have a length corresponding to 8 times the nozzle diameter . lengths of the mixing channel are preferred that correspond to 5 to 30 times the diameter of the nozzle . in diameter , the lumen of the branching piece and the lumen of the main piece between nozzle and outlet opening are preferably not smaller than the lumen of the catheter or cannula insertable into the airway of a patient ( e . g . at least 2 mm when using a catheter with an internal diameter of 2 mm ), since otherwise an additional resistance is created that disturbs in particular the outward flow or aspiration of gas from the lung . a much larger opening or openings to the branching piece again lead to the design problem of accommodating these in or on the smaller lumen of the main piece . this , like a much larger lumen of the branching piece too , is also without any relevant effect on the flow resistance , which is then determined mainly by the catheter or cannula insertable into the airway of a patient . the described design not only allows a gas or gas mixture under excess pressure to be delivered to a catheter or cannula and thus generate a gas flow there in the direction of the patient , it also permits use of a gas flow or gas mixture flow to generate an underpressure and thus generate a gas flow in a catheter or cannula away from the patient . this can be done selectively by opening and closing the outlet opening , even though the gas flow reversing element is supplied only with excess pressure . for patient safety , it is important that no effect is made on the airway in the event of unintentional manipulation of the gas flow reversing element . it is therefore advantageous if at least one safety opening is present , preferably in the branching piece . there should preferably be two safety openings , particularly preferably two safety openings lying next to each other or opposite each other . these safety openings serve at the same time to control the overpressure or underpressure in the direction of the patient . when released , they additionally act as pressure compensation openings and permit compensation of an intrathoracic overpressure or underpressure when the jet ventilation is briefly stopped . in this way , the pressure in the lung can be balanced with the outside pressure . this is particularly important when there is a completely obstructed airway and it is not known whether the patient &# 39 ; s lung is in fact inflated slightly too much or has been emptied . when the pressure connector of the gas flow reversing element is connected to a compressed gas source , gas flows through the nozzle to the outlet opening , which , without safety openings , leads directly to an underpressure at the line connector and thus possibly also in the airway . this is avoided by the still open safety openings , which for this purpose should have a sufficiently large cross section , since the underpressure is compensated by ambient air flowing in there . it is only when all the safety openings have been deliberately closed , e . g . by an operator &# 39 ; s fingers , that an underpressure arises at the line connector . by additional closure of the outlet opening , a gas or gas mixture can then also be conveyed into the airway . by contrast , when the safety openings are released , the gas or gas mixture escapes immediately into the ambient air . effective ventilation is achieved by selectively opening and closing the outlet opening while the safety openings are closed . the outlet opening is preferably shaped as an outwardly opening funnel that cannot unintentionally be closed so easily as a small outlet opening . particularly in emergency care , it is advantageous , according to a preferred embodiment of the invention , to arrange the outlet opening and the safety openings in such a way that they can selectively be closed individually or together , completely or partially , for example manually , preferably with the ball of the thumb and and / or with the fingers of just one hand of a helper or of an operator . thus , with one hand , a helper can perform the ventilation as required , interrupt the ventilation or regulate it by partially closing the openings , while still having the other hand free for other measures or activities ( e . g . securing the catheter or cannula ). the pressure connector of the gas flow reversing element is preferably designed to establish a connection to a compressed gas source , preferably a compressed oxygen cylinder . most vehicles for emergency medical treatment and most casualty wards have at least one small compressed oxygen cylinder ( e . g . 2 liters ) with which the gas flow reversing element can be operated for a period of at least 20 minutes . it may be necessary to admix medicaments to the gas or gas mixture . for this purpose , a closable side access can be arranged particularly advantageously on the branching piece , preferably between the safety openings and the line connector . thus , for example , adrenaline , local anesthetics , expectorants and the like can be conveyed in finely atomized form to the patient by means of the rapidly flowing gas or gas mixture . in this way , a medicament can be distributed effectively and over a large surface area into the bronchi and is thus more rapidly absorbed . the side access also provides a possible connection for a capnometry line via which a small sample for measuring the carbon dioxide concentration can be removed from the aspirated respiratory air in the secondary stream . this permits ongoing determination of the efficiency of the ventilation ( ventilation decreasing or increasing over time ). direct or indirect attachment of a gas flow meter or pressure meter is also conceivable . according to the invention , the main piece and the branching piece preferably together form what is approximately a t - piece , with the main piece as the crossbeam . this makes the structure particularly noticeable and the nozzle construction very simple . alternatively , according to the invention , a gas flow reversing element is proposed in which the main piece and the branching piece together form what is approximately a y - piece , with the outlet opening forming the foot of the y . an arrangement in which the branching piece is at an angle of between 10 ° and 90 ° with respect to a straight main piece may also be advantageous in terms of the flow . to simplify production , the gas flow reversing element according to the invention is preferably assembled , in particular screwed together , from several component parts . this permits the use of standard components for part of the arrangement . it is also preferable for the pressure connector and / or the line connector , and if appropriate the side access , to be designed as a luer lock , in order to permit pressure - tight connection to standard components . for safety reasons , it appears expedient to encapsulate the high - pressure part of the gas flow reversing element , including the connecting tube attachment . generally , the gas flow reversing element according to the invention should be made substantially of plastic , the nozzle being composed of plastic or of a metal insert . the method according to the invention for operating a gas flow reversing element will be explained in detail below . the method is basically one in which a substantially constant gas pressure , in particular oxygen pressure , is applied to the pressure connector , and , in order to generate an overpressure at the line connector , the outlet opening and if appropriate all the safety openings are closed and , in order to generate an underpressure , the outlet opening is opened , if appropriate with the safety openings still closed . by means of this principle of aspirating respiratory air via a catheter or cannula insertable into the airway of a patient , the gas flow reversing element can be combined in a very practicable way with conventional jet ventilation . it is in this way possible , not only in emergency cases , for a patient to be efficiently ventilated ( i . e . sufficiently supplied with oxygen while at the same time carbon dioxide is removed ) via conduits of small cross section ( e . g . catheters or cannulas inserted transcutaneously into the trachea , but also so - called tube changers or working channels of flexible fiber optics ). it is unimportant whether the upper airway is open , as is essential in conventional jet ventilation , or is by contrast partially or even completely obstructed . for the use of the gas flow reversing element according to the invention , only a compressed oxygen cylinder and a connecting line are needed . the gas flow reversing element can be designed such that it can be adapted or constructed in particular also for different pressures of the oxygen sources . for example , oxygen sources have an outlet pressure of 3 . 5 bar in the united states and , by contrast , of up to 5 bar in europe . an important variable in the gas flow reversing element is the emission pressure at the nozzle , by which an underpressure is generated at the line connector . the emission pressure correlates directly with the flow and the resulting speed of flow of the gas or gas mixture through the gas flow reversing element , and the speed of flow of the gas or gas mixture in turn correlates with the underpressure at the line connector . with a view to the considerable suction performance that is desired , it is necessary to work with very high gas speeds . these can be achieved preferably by injector nozzle openings of 1 mm or less . a compressed gas flow of 15 liters per minute through such a nozzle can give gas speeds in the supersonic range . it is also important that the generated underpressure in the branching piece can be converted into a relatively high gas flow , which is best achieved if there are no reductions in cross section significantly impeding the gas flow in the main piece between the branching piece and the outlet opening . the gas flow reversing element can also be combined with an upstream flow meter . this permits very simple and quick adaptation to the patient ( e . g . children are in this way ventilated with a lower oxygen flow and thus with a lower emission pressure at the nozzle and thus also a lower underpressure at the line connector ). a reduction in the gas ( mixture ) flow always results in weaker ventilation ( reduction of the respiratory minute volume ), while an increase in the gas ( mixture ) flow always results , by contrast , in stronger ventilation ( increase of the respiratory minute volume ). since a typically used catheter or cannula provides a considerable flow resistance , the overpressure or the underpressure acting alternately at the line connector is attenuated . pressure changes in the lung of a patient are always attenuated primarily by the gas volume still present in the lung after normal exhalation ( functional residual capacity ) and secondarily by the elastic thoracic wall and the displaceable diaphragm . the danger of barotrauma is minimized in this way . barotrauma is basically only possible upon prolonged incorrect operation of the gas flow reversing element by the user . thus , the risk of collapsing lung sections ( development of atelectasis ) in the event of an excessively long and strong aspiration of respiratory air from the lung is countered by what is in emergency situations a desired positive circulatory effect , while a low pressure in the thorax improves the return flow of blood to the heart . in ventilation tests in a lung model using an oxygen flow of 15 liters per minute and an overpressure of ca . 1 bar above atmospheric pressure , and using a transtracheal catheter measuring approximately 10 cm in length and with an internal diameter of 2 mm , a respiratory minute volume of more than 6 liters per minute was measured , which is sufficient for ventilating an adult . this gives a ratio of at least 0 . 4 : 1 , preferably 0 . 6 : 1 to 2 : 1 , between the volumetric flow rate through the branching piece and the volumetric flow rate through the pressure connector . it should also be noted here that , in jet ventilation through a transtracheal catheter , there is no anatomical dead space and , therefore , a smaller respiratory minute volume is in principle already enough for sufficient ventilation ( called normal ventilation ) of a patient . a noticeable aspect of the tests was a more or less physiological relation between inhalation time and exhalation time ( here the time of injection of oxygen , and the time of aspiration of respiratory air ). this minimizes ventilation - induced circulatory problems . by contrast , passive removal of respiratory air through such a transtracheal catheter results in a grotesque inhalation / exhalation ratio , with an exhalation time longer by a multiple than the inhalation time . limiting the underpressure in relation to atmospheric pressure ( relative pressure ) to approximately − 0 . 3 bar , which was achieved in tests , is advantageous . if the catheter or cannula lies on the mucosa , it cannot aspirate too strongly and cause local damage to the mucosa . the principle used causes the catheter or cannula to be forced away from the mucosa upon each injection . the simple “ switching ” between overpressure and underpressure functions well and is virtually without risk to the patient and user , with cyclical reversal of flow and pressure in the gas flow reversing element , and opens up new possibilities particularly in emergency ventilation . the absence of any mechanisms or movable parts not only makes the relatively small device maintenance - free , but also makes it easy to understand and safe to use . something potentially dangerous ( under very unfavorable conditions ) can happen only as a result of deliberate manipulation by the user , not by connection of the gas flow reversing element as such or by the loosening of a connected compressed gas source . the range of use , however , goes far beyond the “ cannot ventilate , cannot intubate ” situation . a patient with only a partially or temporarily obstructed upper airway will no doubt also benefit from this ventilation principle , the suction - assisted exhalation providing a virtually greater free airway . even in patients with an open upper airway , it is to be expected that more efficient gas exchange and greater gas conversion in the lung will result in more rapid oxygen enrichment and at the same time more effective carbon dioxide elimination . there is also the possibility of simple jet ventilation . for this , the outlet opening and the safety openings simply have to be closed simultaneously and then released again , i . e . suction - assisted exhalation is only an option that can be used ; it does not have to be used . the implementation of this principle in conventional jet ventilators is desirable . today &# 39 ; s devices all require a sufficiently large , free upper airway in the patient . in the event of substantial or complete obstruction of the airway ( e . g . by instrumentation ), these devices stop as soon as too high a pressure is measured in the airway , with the result that the patient is no longer ventilated . based on the present invention , jet ventilators can be constructed which , independently of the free cross section of the airway and even in cases of complete obstruction of the airway , are able to ventilate a patient not only sufficiently , but also very safely and effectively . starting out from the operating principle of the gas flow reversing element , very precise control of the inhalation / exhalation ratio and of the ventilation frequency could be achieved by means of an apertured disk or apertured wheel that rotates about the outlet opening . by suitable cutouts in this apertured disk or apertured wheel , inhalation time and exhalation time could therefore be determined in such a way that the injected gas ( mixture ) volume is subsequently removed again . with a rapidly rotating apertured disk or apertured wheel , it would also be relatively simple to achieve ventilation frequencies in the sense of high - frequency ventilation ( e . g . for lung - protective ventilation of critically ill patients ) which , in conventional devices , require considerably greater outlay in technical terms . this would open up entirely new possibilities in diagnostic and therapeutic interventions . in fig1 , a gas flow reversing element 1 is shown with a main piece 2 which connects a pressure connector 4 to an outlet opening 5 . the pressure connector 4 can be connected by a connecting line 13 to a gas supply 14 which is under excess pressure in a compressed gas source 11 . a compressed oxygen cylinder is generally made available for the emergency care of patients . extending off from the main piece 2 is a branching piece 3 , which leads to a line connector 6 . in the main piece 2 there is a nozzle 7 through which gas can flow from the pressure connector 4 to the outlet opening 5 . this nozzle 7 lies near the branching piece 3 , such that the gas flowing through the nozzle to the outlet opening 5 generates an underpressure in the branching piece 3 . here , the principle of a gas jet pump is used . however , it is possible to choose any arrangement that is able to generate a suction effect by means of a gas flow . for this purpose , it is in particular not necessary for the branching piece 3 , as shown in the illustrative embodiment , to form a right angle α ( alpha ) with the main piece 2 . moreover , the branching piece 3 has a first safety opening 8 and a second safety opening 9 . as long as these two safety openings 8 , 9 are not deliberately closed , the device , even with gas flowing through it , does not exert any influence on the airway of a patient . it is only when these safety openings 8 , 9 are closed that an underpressure is generated in the branching piece 3 , as long as the outlet opening 5 is open , and an overpressure when the outlet opening 5 is closed . all the openings should preferably be arranged in such a way that , although an operator can intentionally close them using one hand , they cannot be closed unintentionally . at least the outlet opening 5 should be able to be closed with one finger , since it has to be selectively opened and closed during ventilation . here too , in order to avoid unintentional actuation as far as possible , the main piece 2 can be widened in a funnel shape before the outlet opening 5 . as is indicated schematically , a rotatable apertured disk 16 with holes of different sizes can also be arranged before the outlet opening 5 and can then be turned to the respectively desired position by an operator . the branching piece 3 also has a closable side access 12 through which medicaments can be added or probes inserted . a catheter 10 or a cannula can be attached to the line connector 6 . each of the connectors is preferably designed as a luer lock . the whole arrangement is preferably made of plastic , although , if so required , the nozzle 7 can also be fitted as a metal part . fig2 , 3 and 6 show alternative embodiments of the main piece 2 and of the nozzle 7 . fig2 shows an embodiment of the main piece 2 as a venturi tube in which the branching piece 3 opens in at the point of greatest speed and therefore of lowest pressure . in both of fig2 and 3 , the main piece 2 , at the area behind the branching piece 3 , forms a channel 15 that widens conically with an opening angle θ ( beta ) of 1 ° to 7 °, for example . fig4 shows another schematic representation of an embodiment of the gas flow reversing element 1 with main piece 2 and branching piece 3 . here , d 1 designates the internal diameter of the nozzle 7 , d 2 the internal diameter of the mixing channel 17 , and d 3 the internal diameter of the branching piece 3 . l 1 designates the length of the nozzle 7 , and l 2 the length of the mixing channel 17 . in a preferred functional test arrangement , the internal diameter d 1 of the nozzle 7 was between 0 . 5 and 2 mm , preferably 1 mm , and the internal diameter d 2 of the mixing channel 17 was between 1 and 5 mm , preferably 2 to 3 mm , in particular 2 . 5 mm . the internal diameter d 3 of the branching piece 3 was of the same order of magnitude as the internal diameter d 2 of the mixing channel 17 . the length l 1 of the nozzle 7 was 5 to 20 mm , preferably 15 mm . the length l 2 of the mixing channel was 10 to 40 mm , preferably 20 to 30 mm , and the ratio of the length l 2 of the mixing channel 17 and the internal diameter d 1 of the nozzle 7 was between 2 : 1 and 100 : 1 , preferably between 5 : 1 and 50 : 1 . fig5 shows another embodiment of the gas flow reversing element 1 , in which the gas flow reversing element 1 is arranged in an ergonomically shaped housing 18 . the housing 18 is shaped in such a way that it is adapted to the human hand . the safety openings 8 , 9 can be completely or partially closed with the fingers , and the outlet opening 5 with the thumb . it does not matter whether the outlet opening 5 , the safety openings 8 , 9 , the pressure connector 4 and / or the line connector 6 are mounted directly on the outer wall of the housing or whether the respective connection between the opening or connector and the outer wall of the housing is embodied by a line section , for example a connecting line 13 . by means of such a configuration , a helper can operate the gas flow reversing element 1 using just one hand . for easier handling , it is also possible to provide just one safety opening 8 . the housing 18 and the gas flow reversing element 1 can be assembled in different ways or produced in one piece . the important thing is that a device is obtained which is easy to operate manually and can be held in one hand , with the outlet opening 5 and the safety openings 8 , 9 being able to be closed off by the fingers or by other parts of this hand . the present invention permits effective ventilation of a patient . under emergency conditions , in addition to a catheter 10 or cannula that can be inserted into a patient &# 39 ; s airways , and a connecting line 13 , all that is needed is a compressed gas source 11 , e . g . a compressed oxygen cylinder . this ventilating technique provides a high degree of safety for patient and helper . it can also be used as a means of respiratory assistance to support the respiration of a patient who is breathing spontaneously . the gas flow reversing element and the method for operating the gas flow reversing element according to the present invention can in particular be used for ventilation of a patient , in particular a patient having no adequate respiratory function on his own , with expiratory assistance by suction . the method for ventilation of a patient with expiratory assistance by suction can in particular be used in case of one of the following indications : a ) transtracheal jet ventilation ; b ) ventilation via conduits of small cross section ( e . g ., catheters ) in case of obstructed , nearly complete or even completely blocked airways due to pharyngeal , laryngeal , tracheal or bronchial tumor ( e . g ., carcinoma , submucosal edema , bleeding , emphysema ); c ) one lung ventilation via conduits of small cross section ; and d ) diagnostic and / or therapeutic intervention in the airway limiting the size of the artificial airway ( e . g ., endotracheal tube ) that can be placed for maintaining adequate ventilation . the method for ventilation of a patient with expiratory assistance by suction can in particular be used in case of one of the following medical conditions : a ) pharyngeal , laryngeal , tracheal , bronchial airway obstruction limiting passive backflow from the lungs ; b ) pharyngeal , laryngeal , tracheal , bronchial airway obstruction limiting the size of an artificial airway ( e . g ., endotracheal tube ) that can be placed for maintaining adequate ventilation ; c ) pharyngeal , laryngeal , tracheal , bronchial airway obstruction limiting the size of the artificial airway ( e . g ., endotracheal tube ) that can be placed for maintaining adequate ventilation during diagnostic and / or therapeutic interventions in the airway ; d ) “ cannot ventilate , cannot intubate ” situation ; and e ) support of cardiocirculatory resuscitation by alternately creating negative and positive intrathoracic pressure . furthermore , for the gas flow reversing element , according to the present invention , the outlet opening of the nozzle is preferably positioned in front or above the branching piece . this improves the efficiency of the jet entrainment effect in the element according to the present invention . while certain exemplary embodiments have been described and shown in the accompanying drawings , it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention , and that this invention not be limited to the specific constructions and arrangements shown and described , since various other changes , combinations , omissions , modifications and substitutions , in addition to those set forth in the above paragraphs , are possible . those skilled in the art will appreciate that various adaptations and modifications of the just described embodiments can be configured without departing from the scope and spirit of the invention . therefore , it is to be understood that , within the scope of the appended claims , the invention may be practiced other than as specifically described herein .
a gas flow reversing element is provided comprising a main piece defining at least one closable outlet opening , a branching piece extending from the main piece , a line connector connected to the distal end of the branching piece , a pressure connector connected to the main piece , the pressure connector being structured to be fluidly connected to a pressurized gas supply ; and a nozzle being configured and arranged in the main piece in such a way that a gas flow flowing in the main piece from the pressure connector through the nozzle to the at least one outlet opening , with the at least one outlet opening being disposed in the second open position , a gas flow can also be generated in the branching piece in a direction toward the at least one outlet opening .