Breathing aid apparatus

Abstract

An artificial respiration apparatus comprising a tip connectable to a source of gas under pressure, said tip including a bore hole; a valve seat at the end of said bore hole facing away from the source; an outlet connectable to the respiratory system of a patient; a movable valve member cooperating with said valve seat to close said bore hole, a spring cooperating with said movable valve member and biasing the same against said valve seat, a housing including a first chamber communicating with said source of gas and also with said outlet when the moving valve member is not in contact with the valve seat; and a second chamber in which said spring is housed, one wall of said second chamber being formed of said movable valve member, a channel communicating said first chamber with said second chamber, a pellet of porous material disposed in said channel which produces a loss of pressure therein; and a pressure screw cooperating with said pellet for varying the compression thereof, thereby adjusting the flow of gas from said first chamber to said second chamber.

Description

The present invention relates to a breathing aid apparatus and concerns an apparatus suitable for ensuring the inhaling phase of the pulmonary breathing of a user whose breathing out phase is controlled by his respiratory muscles as well as an apparatus which, while ensuring the enhaling phase of the pulmonary respiration, assists the breathing out phase of said breathing.

Such apparatus as the operating power of which is provided by a source of compressed gas, advantageously the source of the gas to be blown into the patient's lungs, are already known. In these apparatus, means are provided for controlling the breathing cycle, i.e. the sequence of fresh gas insufflation and of ventilation of the breathing system ventilation periods, by means of pneumatic logic circuits.

However, owing to the relatively large number of components required for constituting the logic circuits, such as valves, fluid throttle means, etc., a relatively large apparatus is required and which is consequently difficult to transport, particularly in the case of first aid to the injured persons. In addition, the large number of components increases the cost of the equipment without increasing their reliability.

One general aim of the invention is to provide a breathing aid apparatus of particularly simple design, with a reduced number of components, and consequently of low cost, which remedies the drawbacks of known apparatus as particularly an apparatus of reduced dimensions which is thus well suited to a plurality of operating conditions.

It is also a purpose of the invention to provide such an apparatus for simply and reliably humidifying gases or a mixture of gases blown into the lungs of a user, as is for example necessary in the case of anaesthesia, and whose working parameters particularly frequency, flow rate and the ratio of the fresh gas insufflation time to the breathing out time of stale air in an elementary cycle, can be adjusted easily.

The breathing aid apparatus according to the invention, comprising an end piece suitable for connection to a source of pressurized gas to be blown into a patient's lungs, and means deriving their operating power from the gas source and a circuit in derivation form a said source in which is inserted an adjustable throttling means, for periodically connecting the gas source to the output of the device suitable for connection to the patient's pulmonary system, is characterised in that said means are constituted by a single automatic servo-controlled valve, the mobile member of which is subjected to an elastic force applied in the same direction as that of the pressure in the circuit in derivation.

The invention will be fully understood by means of the following description given for the purposes of example and with reference to the attached drawings wherein:

FIG. 1 represents a longitudinal cross-section of a first embodiment of a device according to the invention;

FIG. 2 is a part view analogous to that of FIG. 1 but for an alternative embodiment;

FIG. 3 is a view analogous to that of FIG. 1, but for another embodiment;

FIG. 4 is a graph;

FIG. 5 is a view analogous to that of FIG. 1, but for yet another embodiment;

FIG. 6 is a larger scale view of a part of the device represented in FIG. 5 for a first state;

FIG. 7 is a view analogous to that of FIG. 6 but for another state of the device;

FIG. 8 illustrates the functioning of means for humidifying gas blown by a device according to the invention;

FIG. 9 is a view analogous to that of FIG. 8, but for an alternative embodiment;

FIG. 10 is a view analogous to that of FIG. 1, but for yet another embodiment;

FIG. 11 is a top view on a large scale of a member of the device represented in FIG. 10;

FIG. 12 is a cross-section along line 12--12 of FIG. 11;

FIG. 13 is a top view of another member of the device represented in FIG. 10;

FIG. 14 is a cross-section view along line 14--14 of FIG. 13;

FIG. 15 is a part longitudinal cross-section of another embodiment of a device according to the invention.

First, referring to FIG. 1, the breathing aid apparatus according to the invention comprises a first end piece 11 with a longitudinal bore 12 the althrough having a cross-sectional area s and whose mouthpiece 13 is suitable for connection to a source of pressurized gas to be blown into the lungs of a patient, for example oxygen or a mixture of oxygen and another gas. At its end opposite that connected to the gas source, end piece 11 is shaped into a collar 46, or valve seat, surrounding bore 12 which emerges in a chamber 14 provided in body 15, screwed to piece 11 with a seal 16 interposed between pieces 11 and body 15. The central portion of body 15 comprises a cavity 17, extending from chamber 14, in which is mounted a piston 19 with a working face 47 having an area S, a seal 18 being interposed, the piston being biased by a spring 20 bearing against the bottom of cavity 17. A channel 21 emerges in the cavity and connects it to a radial chamber 22 of body 15 housing an element 23 causing a considerable pressure drop, such as a pellet of porous polyurethane foam or analogous material, acted upon by a compression piston 24 bearing a seal 25 and displaceable by the operation of a screw 26.

A channel 27 connects the chamber 14 to chamber 22 and a longitudinal through bore 30 of body 15 connects chamber 14 to a chamber 31 provided in a body 32, screwed onto body 15, and shaped to form a venturi with a neck 33 and flared portion downstream from chamber 31 in the direction taken by the gas (arrow f) flowing from the pressurized gas source towards the patient.

A sleeve 38 is attached to the wall of body 32 by means of an internal thread 37 and a screw 35 having a longitudinal through bore 36; a mouthpiece 39 is integral with said sleeve and possesses a longitudinal bore 40 suitable for connection to a source of gas different from that introduced through mouthpiece 13, for example air or anaesthizing gas. A needle type device 41 is rotatably mounted in sleeve 38 for interconnecting chamber 31, as desired with the gas source suitable for connection to mouthpiece 39.

The lower portion of needle device 41 is provided with a non return valve 42 opening outwardly for decompressing chamber 31 if necessary by discharge into the atmosphere.

The device according to the invention functions as follows:

After connecting to mouthpiece 13 a pipe 48 the other end of which is connected to a pressurized gas source 49, for example a cylinder of compressed oxygen, which is reduced to a pressure P, the outlet 30 of body 32 is connected to the pulmonary system of a patient whose breathing said device is intended to ensure, the means for connection between outlet 50 and the pulmonary system being of any suitable known type, for example a mask, a cannula, a tube or analogous device.

In a first mode of use, connection between chamber 31 and bore 40 of mouthpiece 39 is cut off by the needle device 41 and, in the initial state, the spring 20 presses face 47 of piston 19 against collar 46. The relative pressure P in bore 12, together with the relative pressure p in chamber 51, defined by cavity 17 and piston 19, are zero. When gas cylinder 49 is opened, a relative pressure P is set up in bore 12 and the forces then acting upon the piston are, on the one hand, that set up by spring 20, having a value R, which tends to maintain piston 19 against collar 46 and, on the other hand, that of value Ps tending to displace piston 19 in the direction of arrow f.

If a value below Ps, for example Ps/2, is selected for the force R applied by spring 20, the pressure against face 47 is larger and piston 19 is displaced in the direction of arrow f against the bias of spring 20 which is compressed. The gas from cylinder 49 fills chamber 14 in which the pressure is equal to P; the gas then flows from cylinder 49 through conduit 30, chamber 31 flared portion 34 to the patient's pulmonary system, the gas flow rate being a function of the inside cross-section of conduit 30 which is here precalibred and, if necessary, can be adjusted by a variable throttle means such as a needle valve. Simultaneously, owing to the pressure differences in chambers 51 and 14, there is a flow of fluid between said chambers through channel 27, pressure drop member 23 and conduit 21. By analogy with the law whereby a current is set up in an electric circuit comprising a resistor and a capacitor (the volume of chamber 51 corresponding to an electric capacitor and element 23 causing a high loss of charge corresponding to an electrical resistor), pressure p in chamber 51 increases from zero value to a value p.sub.2 in accordance with a substantially expenential law, whose parameters depend on volume V in chamber 51 and the resistance to the flow of fluid through compressed porous pellet 23, this resistance being adjustable by operating screw 26.

When the pressure p in chamber 51 reaches the value p.sub.2 such that:

Sp.sub.2 + R = SP

i.e. for a value: ##EQU1## piston 19 is displaced in the opposite direction to that represented by arrow f and face 47 comes into contact with collar 46, blocking bore 12. The flow of fluid through bore 30 is then cut off, and the device does not supply the patient with gas. The pressure is zero in chamber 14 and gas then circulates between chambers 51 and 14 through channel 21, the porous pellet 23 and channel 27, this circulation decreasing pressure p from value p.sub.2 previously reached at moment t.sub.1 to a pressure value p.sub.1 reached at moment t.sub.2 and such that:

p.sub.1 S + R = sP

i.e. ##EQU2##

Owing to this pressure value in chamber 51, the pressure acting on face 47 of piston 19 again becomes preponderant and piston 19 is displaced in the direction of arrow f, unblocking the outlet of bore 12, reconnecting the gas supply to the patient and triggering a cycle analogous to the one above described.

Curves I and II respectively in FIG. 4 represent the variations in pressure and instantaneous flow of gas blown into the lungs of the patient, in a graph the abscisses of which is the time axis and the ordinate of which is the pressure and flow axes.

Time T during which the gas from source 49 is blown into the lungs of the patient, on one hand, and time t during which communication between the source and the patient is cut off, on the other hand, as well as the frequency of the respiratory cycle and the flow rate for gas blown in, can be determined, for a given pressure value P, by suitable selecting the force R of spring 20, the resistance to fluid flow afforded by pellet 23, the cross-section of bore 30 and the surface to surface ratio S/s of the working surfaces of piston 19 and bore 12. Thus, if the following ratio is chosen: ##EQU3## and a value of R is selected equal to PS/4, times T and t are equal, pressure p.sub.1 being equal to P/4 and pressure p.sub.2 equal to 3P/4.

During the phases of the cycle corresponding to portions AB of curve I in FIG. 4, i.e. during the patient's expiratory phase, the stale air escapes from the device through non-return valve 42. The invention here exploits the fact that, owing to the relatively high velocity of the gases at the outlet of bore 30 into chamber 31, a depression is set up upstream of neck 33, in relation to the gas flow direction represented by the arrow f and, if said depression is regulated to a value of the order of 30 mb by appropriately selecting the dimensions of the constituent members of the device, the requisite security means for artificial respiration devices in order to avoid pulmonary overpressure in the case of an excessive blown gas rate, or obstruction of the respiratory canals, are obtained, valve 42 becoming operative for a pressure of over 30 mb at outlet 50 of the device. In another mode of use of the device according to the invention, needle member 41 fully or partially opens the outlet of bore 40 of mouthpiece 39 communicating with the atmosphere, thus providing the mixture in a given proportion of gas from source 49 and ambiant air then drawn in by the depression obtaining in chamber 31.

In yet another mode of use, a source of anaesthizing gas, for example a container supplied with a suitable gas at a known flow rate, is connected to mouthpiece 39 and it is then a mixture of gas from source 49 and gas from the container connected to mouthpiece 39 which is blown into the lungs of the patient.

In the embodiment represented in FIG. 2, which is designed and functions in an analogous manner to that of FIG. 1, piston 19 is replaced by a membrane 55 bearing on the one hand, against a collar 56 surrounding the outlet of cavity 17 and, on the other hand, against collar 46 surrounding the outlet of bore 12, a spring 20a being interposed between membrane 55 and the bottom of cavity 17.

In the embodiment represented in FIG. 3, in order to provide additional security, body 32 is provided with orifices 57 and, substantially at right angles to neck 33 of the venturi, a shoulder 58 against which bears the extremity of a spring 59 the other extremity of which cooperates with the face 60 of a piston 61, a groove 63 of which is provided with a seal 64. This piston has a bore 62 therethrough connected to a cavity 65 emerging on face 66 of piston 61 opposite bore 30 of body 15. In this embodiment, in the state wherein gas flow is cut off between source 49 and the patient, spring 59 maintains piston 61 away from holes 57, so that the patient can, if necessary breathe freely through these holes. In the inhaling phase, actuated by the device, the pressure exerted on face 66 of piston 61 overcomes the bias of spring 59, so that piston 61 is displaced towards neck 33 of the venturi, blocking holes 57; the device then functions in an analogous manner to that of the embodiment represented in FIG. 1. In this embodiment, the switch-over to natural spontaneous breathing on the part of the patient can be made without disconnecting the device simply by cutting off gas supply, so that a failure or an accidental interruption of supply does not entail the risk to see the patient's pulmonary system cut off.

Reference is now made to FIGS. 5 to 7 concerning an embodiment of an breathing aid apparatus suitable, not only for ensuring the inhaling phase of pulmonary respiration, but also for assisting the breathing out phase.

In this embodiment, the device comprises an end piece 111 having a longitudinal bore 112 therethrough whose mouthpiece 113 is suitable for connection to the source of pressurized gas to be blown into the lungs of a patient. The extremity of piece 111 remote from mouthpiece 113 is shaped to form a collar 114, or a valve seat, adjacent to a flange 115 having a threaded periphery connected to mouthpiece 113 by a sleeve 116 with a smaller outside diameter than flange 115 and which has a radial through bore 117. At the extremity of sleeve 116 adjacent to mouthpiece 113, one portion of the outer face of piece 111 comprises a thread 118 engaging with the internal thread of a ring 119, which is advantageously knurled, comprising an annular collar 120 whose internal diameter is substantially equal to that of sleeve 116 and whose external diameter is substantially that of flange 115. In order to adjust the position of ring 119 in relation to piece 111, the latter comprises tapped blind holes 121, (FIG. 7), distributed in a ring coaxial with piece 111 and with which screws A 122 passing through coaxial bores 123 of ring 119 are suitable for cooperating.

At its extremity adjacent to collar 114, bore 112 emerges in a chamber 124 provided in a body 125 assembled to piece 111 by screwing flange 115 in a tapped bore 126 of body 125. Two O-rings 127 and 128 being interposed between sleeve 116 and said body opposite the outlet of a through channel 130 of body 125 facing the outlet of bore 117 of piece 111. In its central portion, body 125 is shaped to form a cavity 131 in which is mounted a piston 132, a seal being interposed, the piston being biased by the action of a spring 133 bearing against the bottom of the cavity in which emerges a channel 134 connecting it to a radial chamber of body 125 containing an element 135 causing a considerable pressure drop, such as a pellet of porous polyurethane or analogous material, which is subjected to the action of a compression piston that can be displaced by operating a screw 136.

A channel 137 connects a chamber 124 to the radial chamber of body 125 and a bore 138 connects chamber 124 to a chamber 139 provided in a body 140 prolonging body 125 to which it is screwed and which is shaped to form a venturi with a neck 141 and a flared portion 142 downstream from chamber 139, in the direction in which gas from the pressurized gas source flows towards the patient. At the downstream extremity of flared portion 142, in the flow direction above defined, is located a nozzle 143 whose calibrated orifice, which is substantially aligned with the axis of the device, communicates with a bore 144 of body 140 prolonging channel 130 of body 125.

Chamber 139 is provided with orifice 145 and, substantially at right angles to the neck 141 of the venturi, a shoulder 146 supports the extremity of a spring 147 whose other extremity engages the face 148 of a piston 149 housed in said chamber and pierced by a bore 150 communicating with a cavity 151 which emerges on face 152 of the piston opposite bore 138 of body 125.

In body 140, beyond orifices 145 in the direction of gas circulation from the source towards the patient, a recess 153 houses an O-ring 154 projecting on the internal wall of chamber 139.

In the state represented in FIG. 5, ring 119 is adjacent to body 125 and collar 120 presses O-rings 127 and 128 together, thus preventing any gas flow from the pressurized gas source through channel 117; the device functions in an identical manner to that of the embodiment represented in FIG. 1 or FIG. 3.

If it is also desired to assist the breathing or ventilation phase of the pulmonary system, ring 119 is unscrewed in order to be spaced from body 125 by an adjustable predetermined distance as represented in FIGS. 6 and 7.

During the patient's inhaling phase, piston 132 is removed from collar 114, (FIG. 7): chamber 124 is at the pressure of the gas source connected to end 113 and, owing to the non-sealing screw assembly of piece 111 to body 125, this pressure applies a greater force on O-ring 127 than that applied by the pressure obtained in conduit 117, so that O-ring 127 is pressed in sealing engagement against O-ring 128 abutting collar 120. Channel 130 does not communicate with the pressurized gas source. and the inhaling phase takes place as with the apparatus of the previous embodiments.

During the expiratory phase, piston 132 is in contact with collar 114 and chamber 124 is no longer connected to the gas supply source (FIG. 6). Under the effect of the pressure obtaining in bore 117, O-ring 127 comes into contact with flange 115 and O-ring 128 remains in contact with flange 120 whose face opposite flange 115 is at a precisely predetermined distance from said flange, so that there is a pressure drop in the gas circulating between bore 117 and channel 130. The gas from the pressurized gas source is then sent through bore 117, channel 130 and bore 144 to nozzle 143 which circulates it through venturi 141, this circulation setting up a depression which brings about and favours the ventilation phase of the pulmonary system of the patient to whom the device is connected. This device then ensures, successively, the inspiratory and expiratory phases of pulmonary respiration.

According to the invention, prevision is also made for humidifying the gas blown into the lungs of the patient, by disposing, downstream from O-ring 154 -- in the flow direction of the gas from the pressurized gas source towards the patient--and in the vicinity of the axis of bore 150, a capillary tube 160, (FIG. 8), connected by a hose 161 to a liquie container 163, which, in its most simple form, is a glass in which the extremity of a tube provided with a strainer 164 is immersed. The high speed accurately located gas flow from bore 150 pulverizes the humidifying liquid in a quantity depending on the height between the output of capillary tube 160 and collector 163 to create a fine spray of humidifying liquid particles in the blown gas, as required, for example, when anaesthizing or carrying out analogous operations.

In the embodiment according to FIG. 9, the extremity of hose 161 remote from capillary tube 160 is not immersed in a humidifying reservoir but is connected, for example, by a chamber 165, communicating with a dropping bottle 166, a valve 167 being interposed. Bottle 166 may then be disposed above the respiratory device and, by adjusting with valve 167, the number of drops supplied for each inspiration is determined for precisely dosing the quantity of liquid to be sprayed.

Reference is now made to FIGS. 10 to 14 concerning another embodiment of a device according to the invention, which, for clarity, is represented as a device of the same type as that in FIG. 2, but which may be of the type represented in FIG. 5.

The device according to this embodiment comprises an end piece 211 having a longitudinal bore 212 therethrough which also runs along mouthpiece 213 suitable for connection to the source of pressurized gas to be blown into the lungs of a patient. At its extremity opposite that connected to the pressurized gas source, piece 211 is shaped to form a sleeve 214 pierced by two radiating bores 215 and 216 which emerge respectively in chambers 217 and 218 provided between the outer periphery of sleeve 214 and the interval surface of member 219, screwed to piece 211, a seal 220 being interposed. Substantially opposite sleeve 214, member 219 provides a seat 221 for a membrane 222 housed in said sleeve and biased by spring 223 bearing against the bottom of a chamber 224, the force of the spring being adjustable by means of a screw 225.

Chamber 217 communicates through a channel 226 with the internal chamber 227 of a tubular piston 228 the bottom 230 of which is pierced by a bore 231 and which is biased by the action of a spring 229 which bears against a shoulder 229a of an mouthpiece 229b integral by screwing with member 219 and which comprises a venturi 232 with a neck 233 and flared portion 234 the extremity of which is suitable for connection to the pulmonary system of a patient by any appropriate means.

Channel 226 is, in fact, constituted by three portions end to end, two of which 226a and 226b are provided in member 219 and which are suitable for interconnection by a third portion provided in barrel member 240, (FIGS. 10, 11 and 12), rotatably mounted about its axis 241 in member 219, O-rings 252, and 254 being interposed. The body of barrel member 240 possesses a blind hole 243 for attaching a knurled operating button 242 and it comprises, for putting the two portions 226a and 226b of channel 226 in communication, a certain number of passages at right angles (6 in the example represented) each comprising (FIG. 12), a radial arm 244 in which emerges a longitudinal arm 245 extended, on the end face 246 of the barrel member, by a forward hole 247. As represented in FIG. 11, the arms 245, uniformly distributed angularly about axis 241, have different predetermined diameters for supplying six different blowing rates for the same supply pressure. Each of the flow rates is read off a graduated annular zone surrounding operating button 242, provided with an index, the precise location of each of its six positions being ensured by a snap-locking means such as a ball 248 suitable for cooperating with semi-circular grooves 251 in the barrel body against which bears a spring 249 the force of which can be adjusted by means of a screw 250.

An apparatus somewhat analogous to that described above for controlling the blowing rate is provided for controlling the blowing frequency, i.e. the number of breathing cycles per minute. As represented in FIGS. 10, 13 and 14, the blowing frequency control means comprise a barrel member 260 with an x axis 262 and a control button 261 pierced by bores, six in the example represented, uniformly disposed angularly about said axis and represented at 263.sub.1, 263.sub.2, etc . . . 263.sub.6. In each of bores 263 emerges a radial bore 264 for connecting chamber 218 with cavity 224, a member 265 causing a high pressure drop being interposed in the junction zone of each bore 263 and 264 associated therewith. Member 265 is, for example, a pellet of porous polyurethane foam or teflon material, compression of which is adjustable by means of a needle screw 266 bearing an O-ring 267 and cooperating with an internal thread of bore 263.

O-rings 268, 269 and 270 contribute to tight communication between chamber 218 and cavity 224.

In a manner analogous to that described above in connection with the blow rate control barrel, a ball 271 biased by a spring 272 is suitable for cooperating with grooves 273 of the body of barrel 260 for precisely locating it in one of the six positions corresponding to the six bores 263 to each of which is attributed a frequency that is predetermined and preset in the workshop by actuating needle screw 266 on member 265 with which it cooperates. By suitably adjusting needle screw 266, it is possible, for example, to attribute to bores 263 values of 15, 20, 25, 30, 40, 50 cycles per minute.

FIG. 15 represents another embodiment of the device according to the invention wherein the flow control means and the blowing frequency control means are continuously adjustable, means being provided on the unit for displaying the real blowing rate and frequency at any moment.

In this embodiment, body 280 of the device possesses tapped bores 281 and 282 with which blowing rate and frequency adjusting screws 283 and 284 respectively cooperate. Screw 283, which is provided, in a shoulder formed by its body, with a sealing O-ring 285, is pierced by a longitudinal hole 287 which emerges in a diametral bore 288 for setting a channel 289 connected to the source of pressurized gas to be blown, not represented, in communication with the chamber of an annular piston, also unrepresented, whose role analogous to that of piston 228 of the previous form of embodiment. Said chamber is connected, by means of a pneumatic circuit in which is inserted an non-return valve and adjustable pressure release means, to a pressure gauge 291 which continuously displays the flow rate of gas blown in accordance with the pressures obtaining in said chamber.

Screw 284, interposed between a cavity and a chamber analogous to cavity 224 and chamber 218 in the previous embodiment, enables the blowing frequency to be continuously adjusted by greater or lesser compression of an element causing a high pressure drop analogous to that represented at 265 in FIG. 14. This embodiment functions as follows:

The flow rate for gas to be blown set at a given value, for example 10 liters per minute, by operating screw 283, is displayed on the pressure gauge 291 during the inhaling phase during which the source of pressurized gas communicates with the user's pulmonary system. When, through actuating the periodic flow device, communication between the pressurized gas source and the user is cut off, the pressure displayed by pressure gauge 291 decreases progressively owing to the presence of the non-return valve and the escape means provided on the circuit interconnecting the pressure gauge and the piston chamber, until a new inspiratory phase begins which again causes said pressure gauge to display the flow rate regulated by means of screw 283. The displayed flow rate again decreases when the inhaling phase ceases and the oscillating flow rate indication resistered by the pressure gauge, which is representative of the blowing frequency, can be indicated on an appropriate scale of the pressure gauge which then simultaneously and continuously indicates both blowing frequency and rate.

Claims

I claim:

1. An artificial respiration apparatus comprising:

a tip connectable to a source of gas under pressure, said tip including a bore hole;

a valve seat at the end of said bore hole facing away from the source;

an outlet connectable to the respiratory system of a patient; and

means for controlling the flow of gas permitting it to pass from the source of gas to said outlet during the inhalation phase of the patient but preventing said flow during the exhalation phase of the patient, said means comprising a movable valve member cooperating with said valve seat to close said bore hole, a spring cooperating with said movable valve member and biasing the same against said valve seat, a housing including a first chamber communicating with said source of gas and also with said outlet when the moving valve member is not in contact with the valve seat; and a second chamber in which said spring is housed, one wall of said second chamber being formed of said movable valve member, channel means causing said first chamber and said second chamber to communicate with each other, a pellet of porous material disposed in said channel means, said pellet introducing a loss of pressure in the channel means; and a pressure screw cooperating with said pellet for varying the compression thereof, variation of the compression of the pellet permitting adjustment of the flow of gas between said first and second chambers.

2. The apparatus according to claim 1 wherein said outlet is formed by the throat portion of a venturi, the apparatus further comprising a nozzle between said outlet and a neck portion of the venturi, said nozzle having an orifice directed towards said neck portion, a channel connecting said nozzle to said bore hole, and means interposed in said channel for selectively interrupting and establishing pneumatic communication between said bore hole and said nozzle, said means including an annular third chamber of adjustable length surrounding said bore hole, a displaceable member defining one of transverse walls of said third chamber for modifying the length thereof, and two toroidal gaskets in said third chamber, said gaskets being movable by the action of pressure forces, placement of said two gaskets in contact with each other interrupting said pneumatic communication when said movable valve member is out of engagement with said valve seat, said communication being open when said movable valve member is in engagement with said valve seat whereby a flow of gas in the direction opposite that during the inhalation phase is established in the venturi during the exhalation phase.

3. An artificial respiration apparatus comprising:

a tip connectable to a source of gas under pressure, said tip including a bore hole;

a valve seat at the end of said bore hole facing away from said source, the axis of said valve seat being coaxial with the axis of said bore hole;

an outlet connectable to the respiration system of a patient; and

means for controlling the flow of gas, said means permitting the gas flow to pass from the source of gas to said outlet during the inhalation phase of the patient but preventing said flow during the exhalation phase of the patient, said means including a servo-controlled valve, said valve comprising a movable member cooperating with said valve seat, elastic means biasing said movable member toward said valve seat to close said bore hole in response to the action of said movable member being subjected to the pressure of gas from said source of gas and to the action of a differential pressure acting in the same direction as the elastic means, said differential pressure being obtained from said source of gas by means introducing an adjustable loss of pressure in a flow circuit provided between said valve seat and the face side of the movable member upon said elastic means acts.

4. The apparatus according to claim 3 wherein said elastic means is a spring, the apparatus comprising further means for adjusting the force developed by said spring, said spring force controlling the ratio of the duration of engagement of said movable valve member with said valve seat relative to the duration of non-engagement of said movable valve member with said valve seat.

5. The apparatus according to claim 3 wherein said movable valve member comprises a piston tightly slidable in a further chamber, said elastic means being disposed in said further chamber, and said flow circuit including said means for introducing an adjustable loss of pressure discharges into said further chamber.

6. The apparatus according to claim 3 wherein said movable valve member comprises a deformable diaphragm forming an end wall of a further chamber in which said elastic means is disposed and into which discharges said flow circuit including said means for introducing an adjustable loss of pressure.

7. The apparatus according to claim 3 further comprising:

a. means for controlling the flow of gas fed to the patient, said means being interposed between said bore hole and said outlet and including a first rotary barrel having a plurality of channels of different cross-sectional area, a member for setting said barrel and means for indexing the position of the barrel in order to adjust the flow to a value selected from among a plurality of predetermined values; and

b. means for controlling the number of phases of inhalation per unit of time, said means comprising a second rotary barrel interposed in said flow circuit and provided with a plurality of means for introducing an adjustable loss of pressure, an operating member, and means for indexing the position of said second barrel so that said number of phases of inhalation per unit of time is adjustable to a value selected from among a plurality of predetermined values.

8. The apparatus according to claim 3 further comprising a non-return valve disposed between said bore hole and said outlet, and an adjustable leak means for adjusting the flow through said non-return valve.

9. The apparatus according to claim 3, comprising further a chamber disposed in the gas flow and having a venturi neck upstream in the direction of flow of the gas from the source of gas towards said outlet, a thin capillary tube; a tank of liquid for moistening the gas coming from the source of gas, and a connection connecting said tank to said tube the discharge end of which into the apparatus is substantially flush with the axis of said venturi neck so that the flow of gas coming from said source obtains a high speed atomizing said liquid thereby producing a fine mist of liquid particles in the gas fed to the patient.