AU762460B2

AU762460B2 - Method and device for supplying modified air

Info

Publication number: AU762460B2
Application number: AU51456/99A
Authority: AU
Inventors: Jean-Baptiste Menut
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-17
Filing date: 1999-08-15
Publication date: 2003-06-26
Anticipated expiration: 2019-08-15
Also published as: WO2000010632A1; AU5145699A; EP1105177A1; ATE298601T1; DE69926004T2; BR9912393A; DE69926004D1; CA2340048A1; EP1105177B1

Abstract

The invention concerns a device wherein oxygen-deficient air is supplied by the compliant bag (1) provided with the switch (1d) which controls the valve (2g) opening when the compliant bag (1) volume reaches its lowest limit (Vmin) so as to connect the ejector (2) to the nitrogen source (4), to inject nitrogen and suck up ambient air into the ejector (2) and fill up the compliant bag (1) with oxygen-deficient air at ambient pressure and drawn from the respirator (3). The valve (2f) controls ambient air suction into the ejector (2) and adjusts the oxygen content of the air inside the compliant bag (1). The compliant bag (1) is repeatedly filled up to 10 times per minute depending on the amount of air drawn, each time the compliant bag volume reaches its lowest limit (Vmin). The compliant bag (1) with a useful volume of 20 litres delivers 5 litres per minute of oxygen-deficient air. The invention is particularly useful for sports training sessions to simulate breathing at high altitude.

Description

Method and Device for Drawing off Modified Air Field of the Invention The present invention concerns processes and devices for drawing off modified air intended for respiration, particularly oxygen-depleted air intended for simulating respiration at high altitude.

Prior Art The prior art relating to means for obtaining oxygen-depleted air intended for respiration may be illustrated for example by the publication W09637176 which concerns an apparatus for training and therapy which comprises a membrane separator serving to extract oxygen from ambient air with the help of a vacuum pump. It is moreover mentioned in said publication that the oxygen content may be reduced by adsorption of oxygen from ambient air or else by adding an oxygen-deficient gas such as nitrogen or air exhaled by the user.

EP 0 744 184 Al concerns a container of variable volume in a breathing/anaesthesia system, said container being connected via an inlet valve to a source of gas intended for respiration and comprising at least a part consisting of an elastic material which produces a constant force and subjects the gas in the container to a constant pressure between predetermined limits of the volume of the container. Gas under pressure is drawn off from said container and delivered to a patient via an outlet valve and a breathing circuit forming a part of said artificial-respiration/ anaesthesia system. The elasticity of said container serves to apply a constant pressure to the gas in the container and said system enables a restricted amount of gas under constant pressure to be delivered to a patient.

Intensive sports training enabling the simulation of the conditions at high altitude nevertheless necessitates the respiration of considerable amounts of oxygen-depleted air.

Summary of the Invention The present invention is intended to provide any amount of air having any modified composition and notably enabling breathing rates to be obtained in a very broad range.

The expression "modified air" used here with regard to the present invention means air with a composition which is modified with respect to ambient air, particularly air intended for respiration.

la Modified air is drawn off according to the invention from a compliant bag whose variation in volume at ambient pressure ensures an interaction between the inflow and the outflow of the modified air.

The present invention essentially consists in enabling modified air at ambient pressure to be drawn off from a compliant bag which is capable of undergoing variations in volume at constant pressure, so that it can be filled with modified air at ambient pressure each time its volume reaches a given lower limit. This compliant bag thus constitutes an air exit buffer which enables any amount of air required for respiration to be drawn off by means of a suction pipe.

The repeated filling of the compliant bag at ambient pressure as a function of the amount of air drawn off according to the invention allows the volume of the compliant bag to be reduced to the strict minimum which is necessary to enable the replacement of any amount of air which is drawn off.

Accordingly, in one aspect there is provided a method of obtaining any amount of modified air required for respiration, comprising: filling a compliant bag with modified air at ambient pressure, said compliant bag being capable of undergoing rapid changes in volume at ambient pressure without elastic deformation; drawing off modified air at ambient pressure for respiration via a suction tube communicating with said compliant bag; and repeating step to fill said compliant bag with modified air at ambient pressure each time the volume of said compliant bag reaches a predetermined lower limit and drawing off modified air by step so as to withdraw any amount of modified air at ambient pressure required for respiration via said suction tube.

S 25 In another aspect, there is provided a device for obtaining any amount of modified air at atmospheric pressure required for respiration according to the method of claim 1, where the device includes the combination: a compliant bag that can be rapidly filled with modified air at ambient pressure; a suction tube communicating with said compliant bag and enabling the modified air 30 at ambient pressure required for respiration to be withdrawn via said suction tube; a valve associated with a source of modified air for filling said compliant bag; and a switch associated with a wall of said compliant bag and arranged to open said valve in order to supply modified air whereby to fill said compliant bag with modified air at ambient pressure each time the volume of the compliant bag reaches a lower limit, Ib wherein said compliant bag is adapted to be filled with modified air at ambient pressure each time its volume reaches said lower limit and thereby enables any amount of modified air required for respiration to be withdrawn from said compliant bag via said suction tube.

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(TRANSLATION)

WO 00/10632 PCJTICH99100377 2 The compliant bag may consequently have a very small volume and be rapidly filled in a few seconds, so that its repeated filling several times per minute allows very large air flow rates in comparison with its restricted volume to be constantly delivered.

The compliant bag employed to carry out the present invention must be a flexible bag which is capable of changing its volume at constant pressure and is consequently capable of being filled at ambient pressure. To this end, said compliant bag may be advantageously made of a pliable and extremely thin sheet of plastics material with a thickness of a few hundredths of a millimetre so as to be able to undergo rapid changes in volume without elastic deformation or modification of its surface.

Air having any composition required fo r respiration is advantageously obtained by means of an ejector connected to the compliant bag as is described later on.

Filling the compliant bag is advantageously achieved by means of an ejector and preferably meets the following conditions: 1. The supply of modified air delivered by the ejector to the compliant bag is equal to the denand for air taken off frm the compliant bag, 2. The intermittent operation of the ejector is controlled by means of the compliant bag according to the air taken off from the compliant bag.

3. The repeated filling of the compliant bag is onstantly adapted to the air taken off for respiration.

4. The compliant bag. and the ejector are arranged in a feedback control loop so as to control the repeated filling of the compliant bag only by means of a switch associated with the compliant bag and a vlve associated with the ejector.

The outlet of the ejector opens freely into the compliant bag at ambient pressure.

6. The pressure and the flow rate of the injected gas are kept constant in the ejector.

7. The flow rate of the air sucked in depends on the air inlet section of the ejector.

8. The composition and the flow rate of the modified air delivered by the ejector depend essentially on the air inlet section of the ejector.

9. The combination of a compliant bag provided with a switch with an ejector provided with a valve thus makes it possible to provide any amount of air having any required composition.

V, Detailed description The invention may be illustrated with the help of embodiments described for example hereinafter and represented as follows in the figures of the drawing.

Fig. I shows schematically an embodiment of a device comprising a compliant bag and an ejector which is associated with a source of nitrogen and serves to provide oxygen-depleted air.

Fig. 2 shows a schematic section of the ejector of the device according to Fig. 1.

Fig. 3 illustrates the variation of the oxygen fraction of air as a function of the ratio of ambient air sucked in to the nitrogen injected into the ejector according to Fig. 2.

Fig. 4a to 4d show respectively the periodic variation of the volume of the compliant bag according to Fig. 1 while taking off 5, 25, 100 and 200 litres per minute while epeatedly filling the compliant bag.

Fig. 5 shows schematically a variant of the device according to Fig. 1.

The device according to Fig. 1 comprises a compliant bag 1 communicating with the outlet of an ejector 2 through a supply pipe la and with a suction pipe lb associated with a breathing mask 3 and with two non-return valves Ic and 3a so as to ensure inhaling via the valve Ic and exhaling via the valve 3a.

The bag 1 is selected so as to be perfectly compliant and capable of undergoing repeated changes in volume at constant pressure, so as to be capable of being filled at ambient pressure in accordance with the invention.

The compliant bag 1 contains a switch represented by a contact Id disposed in a plane represented by the dash-dotted line which corresponds to a lower predetermined limit of the volume of the bag 1. The compliant bag 1 is provided with a conductive inner surface le serving to establish electrical contact with the switch Id when the volume of the compliant bag 1 reaches its lower limit Vmin according to Fig. 1.

The ejector 2 according to Fig. 1 comprises a longitudinal flow channel consisting of a convergent inlet channel 2c communicating with an inlet end 2a and with a divergent outlet channel 2d communicating with an outlet end 2b of the ejector 2. The convergent inlet channel 2c communicates with the atmosphere by mean of an air valve 2f and with a source of nitrogen under pressure 4, in the form of a cylinder of nitrogen in this case, by means of a nitrogen supply pipe 4a, an electrovalve 2g and a supply pipe 2e for the admission of nitrogen under pressure, an annular injection gap 2i and an annular nitrogen admission compartment 2j, which are arranged in the ejector (see Fig. The divergent outlet channel 2d communicates with the compliant bag 1 at the opposite outlet end 2b of the ejector 2 by means of a supply pipe la.

The air valve 2f is provided near the inlet end 2a of the ejector so as to adjust the amount of air sucked into the ejector 1, indicated by the letter A (Fig. 1 and 2).

The nitrogen supply pipe 4a is moreover provided with a pressure reducing valve 4b and with a manometer 4c allowing control of the pressure of the nitrogen supplied to the electrovalve 2g.

Fig. 1 further shows that the switch Id is connected to the electrovalve 2g by means of a retarder 2h, as is indicated by the dash-dotted line So.

The compliant bag 1 is associated with the pipe 2e for supplying nitrogen to the ejector 2 by means the switch Id and the electrovalve 2g so as to control the opening and closing of the electrovalve 2g via a retarder 2h according to the volume of the compliant bag 1.

The electrovalve 2g is an electromagnetic valve associated with the switch Id and with the retarder 2h and is arranged so that it is normally closed in its rest position by means of a spring, that it is activated and brought into its active open position as soon as the volume of the compliant bag reaches its lower limit V and the switch Id establishes an electrical contact with the inner surface le of the bag, that it is kept open in its active position with the help of the retarder 2h during a predetermined period enabling the compliant bag 1 to be filled with air at ambient pressure, and that it is then closed and brought back into its closed rest position.

The supply of nitrogen under pressure to the ejector 2 through the electrovalve 2a is thus controlled in accordance with the invention by means of the compliant bag 1 associated with the switch Id.

Fig. 1 represents the nitrogen-supply pipe 2e by an oblique line in order to indicate that the ejector 2 is provided in this case to effect lateral injection as well as longitudinal flow in the channels 2c and 2d and the axial suction of ambient air.

Satisfactory operation of the device according to Fig. 1 could be ensured by means of a compliant bag made of a fine sheet of Mylar" provided with a metallized inner surface le intended to establish an electrical contact with the switch Id.

Tests have been carried out in the framework of the present invention with a device as described according to Fig. 1 comprising a bag 1 of metallized Mylar in combination with an ejector 2 of known type obtained under the designation "Airmover" of the type AM40. These tests have shown that the described apparatus according to Fig. 1 allows variations of the composition as well as the flow rate of the air taken off from the compliant bag in very broad ranges.

Fig. 2 shows a schematic section in greater detail of an ejector of the described type according to Fig. 1, while the same elements bear the same references in both of these figures.

The ejector according to Fig. 2 comprises a longitudinal flow channel consisting of a convergent inlet channel 2c opening into a divergent outlet channel 2d and a lateral pipe 2e for the supply of nitrogen under pressure. As appears from Fig. 2, the lateral nitrogen-supply pipe 2e communicates with the longitudinal flow channel of the ejector through an annular nitrogen-supply compartment 2j connected to an annular gap 2i which opens into the convergent inlet channel 2c so as to produce longitudinal flow. The configuration of the annular gap 2i is specially designed so as to direct a jet along the wall of the flow channel, to carry along ambient air sucked in at the ,inlet end 2a of the ejector, to mix ambient air with the nitrogen in the divergent channel and to deliver oxygen-depleted air through the outlet end 2b.

The patent CH 595 558 contains a detailed explanation of the structure and the mode of operation of an ejector of the same type as the ejector 2 according to Fig. 1 and 2. An ejector of the type according to Fig. 2 particularly allows the delivery of modified air at high flow rates and rapid filling of the compliant bag at ambient pressure in accordance with the present invention.

Fig. 3 shows the variation of the percentage of oxygen in air as a function of the ratio A/N of the amount of air A sucked in to the amount of nitrogen N injected into said type of ejector.

As appears from Fig. 3, said type of ejector allows the air/nitrogen ratio in the provided modified air to be varied in a broad range extending from A/N 0.5 up to 15 and the oxygen content in a large range extending from Oz 7% up to about which corresponds, at sea level, at a normal pressure of 760 mm Hg, to oxygen partial pressures of 53 mm Hg and 145 mm Hg, that is to say, oxygen partial pressures which air has in the natural environment at altitudes of 8400 and 800 m, respectively.

Fig. 4a to 4d illustrate the operation of the described device according to Fig. 1 by saw-toothed lines representing the successive changes in the volume of the compliant bag 1 as a function of time during the evacuation of air at different flow rates and intermittent operation of the ejector.

Fig. 4a illustrates the variation of the volume of the bag 1 during the evacuation of 5 1/min of air and filling phases each with a duration of 4 seconds. The consumption of air of an individual at rest corresponds to 5 1/min.

Fig. 4a shows the filling and evacuation cycles each comprising on one hand a filling phase during 4 seconds, represented by an oblique ascending branch F which corresponds to the expansion of the bag from a lower limit Vi,n of 10 1 up to an upper limit of about 30 1 during operation of the ejector at the same time as taking off and evacuating air for respiration by means of the suction pipe Ib. Each of said cycles comprises on the other hand an evacuation phase represented by an oblique descending branch R which corresponds to the decrease in volume of the bag down to the lower limit of 10 1.

Each filling phase F is produced by operation of the ejector 2 as soon as the volume of the bag 1 reaches the lower limit Vmi, of 10 1. The switch Id establishes an electrical contact with the conductive inner surface le of the bag 1 so as to cause opening of the electrovalve 2g, to inject nitrogen and to suck ambient air into the ejector 2, to thus fill the bag 1 with modified air at ambient pressure. The electrovalve 2g is in this case maintained in its open position during 4 seconds with the help of the retarder 2h during 4 seconds in order to fill the bag I and to increase its volume from 10 1 to about 30 1.

The electrovalve 2g is then brought back automatically by a return spring and is closed in its rest position during the evacuation phase R corresponding to the decrease in volume of the bag down to the lower limit of 10 1.

It should be noted that the evacuation of air for respiration is effected in this case at an average flow rate of 5 1/min during the entire filling and evacuation cycles, that is to say, during the filling phases F when the ejector 2 is operating as well as during the evacuation phases R.

The description of Fig. 4a applies essentially to Fig. 4b, 4c and 4d and the main differences will be mentioned below.

Fig. 4b represents the variation of the volume of the compliant bag 1 during the evacuation of i/min of air, this flow rate being increased 5 times in comparison with Fig. 4a and the frequency of the cycles F/R as well as the slopes of the saw-toothed lines according to Fig. 4b being increased accordingly.

Fig. 4c represents the variation of the volume of the compliant bag 1 during the evacuation of 100 1/min of air, this flow rate being increased 20 times in comparison with Fig. 4a and the frequency of the cycles F/R as well as the slopes of the saw-toothed lines according to Fig. 4c being increased accordingly.

Fig. 4d represents the variation of the volume of the compliant bag 1 during the evacuation of 200 I/min of air, which corresponds to the consumption of air of an athlete of very high level at full effort, this rate of evacuation being increased 40 times in comparison with Fig. 4a and the frequency of the cycles F/R as well as the slopes of the saw-toothed lines according to Fig. 4d being increased accordingly.

Fig. 4a to Fig. 4d show that the compliant bag with a useful filling volume of only 20 litres can constantly delivery from 5 I/min to 200 /rmin of air. The rate of flow of air delivered by the compliant bag depends on the frequency and the speed of its filling rather than on its volume, while this rate may moreover be further increased.

Fig. 5 represents schematically a variant of the described apparatus according to Fig. 1, the identical elements being designated by the same references in both of these figures.

The variant according to Fig. 5 comprises a compliant bag 51 which is suspended from a horizontal wall 51 f and has an upper opening which is closed off in an airtight manner by said wall.

The compliant bag 51 communicates with the outlet of an ejector 2 by means of a supply pipe la which passes through the horizontal wall 51f in an airtight manner. The ejector 2 according to this variant is essentially the same as the ejector already described according to Fig. 1 and 2. The compliant bag 51 also communicates with a breathing mask 3 by means of a suction tube lb which passes through the horizontal wall 5 If in an airtight manner and comprises a non-return valve Ic. The mask 3 is also provided with a non-return valve for the evacuation of exhaled air.

A proximity switch 51d is mounted in a fixed position in the compliant bag 51 at a location indicated by a dash-dotted line which corresponds to a predetermined lower limit Vm of the volume of the bag 51. Said proximity switch 51d delivers a detection signal sVi, when the volume of the compliant bag reaches its lower limit Fig. 5 represents this detection signal by the dash-dotted line marked sV.n.

The compliant bag 51 further contains an oxygen probe 51g which delivers a signal of oxygen partial pressure spo2 corresponding to the oxygen partial pressure in the air contained in the bag 51.

Fig. 5 represents this oxygen partial pressure signal by a dash-dotted line marked spo2.

A nitrogen supply conduit 4a connects the source of nitrogen under pressure 4 to the electrovalve 2g by means of a pressure reducing valve 4b, a manometer 4c and a pressure sensor 54d which emits a signal spm2 corresponding to the nitrogen pressure in the supply conduit 4a. Fig. 5 represents this nitrogen pressure signal by a dash-dotted line marked spm The device according to Fig. 5 is further provided with a control panel C which is associated with an electronic circuit, not shown, which receives the detection signal sVin from the proximity switch 51d, the oxygen pressure signal spao from the oxygen probe 51g and the nitrogen pressure signal spm from the pressure sensor 54d, and which transmits a control signal scN2 to the electrovalve 2g in order to fill the compliant bag 51 each time its volume reaches its lower limit Vi..

The control panel C comprises a screen with three display zones Dpo 2 Dm, Da, a control button S associated with a main switch (of the ON/OFF type, not shown) for putting the device according to Fig. 5 into operation and taking it out of service and three selection buttons Sp, Sm, Sa serving respectively to select the display of the oxygen partial pressure po2 expressed in mm Hg in the display zone Dpo 2 or else the display of the altitude corresponding to po2 expressed in metres in the display zone Dm or in feet in the display zone Da.

When the volume of the compliant bag 51 reaches its lower limit the detection signal sVm, is emitted by the proximity switch 51d and transmitted to the electronic circuit associated with the control panel C. Said electronic circuit then transmits a control signal scm to the electrovalve 2g so as to cause its opening, to connect the nitrogen source 4 to the ejector 2, to inject nitrogen under pressure and to suck ambient air into the ejector and to fill the compliant bag 51 with a mixture of nitrogen and ambient air having the required composition.

The electronic circuit associated with the control panel comprises a retarder which is not shown and which maintains the control signal scr during a sufficient time to fil the compliant bag 51. The electrovalve 2g is closed automatically under the action of a return spring when the signal scm disappears so as to terminate filling the bag 51.

Said electronic circuit associated with the control panel C is arranged so that it contatl receives thenitoge prssre ignl s~ rom the Pressure sensor 54d when the described device is put int operation by the main switch S and so that it delivers an acoustic warning signal when the nitrogen pressure diminishes to a lower limit required for operation Of the ejector, namely when the nitrogen cylinder 4 is empty.

Carrying Out the invention by means of a device such as described according to Fig. I allows the following advantages to be combined: 1. Any amount of air required for respiration is provided by the compliant bag which is filled each time that its volume reaches it, lower limit, 2, The evacuationI Of air from the comnpliant bag constantly controls its repeated filling according to the amount of air evacuated in each case.

3. The repeated filling of the compliant bag is controlled by the variation of its volume, is constantly adapted to any amount of air consumed and may be ensured by a-valve associated with a source of gas under pressure and controlled by a switch associated with the compliant bag.

4. The volume of the compliant bag may be reduced to the strict minimum required so that its repeated filling enables any required amount of air to be evacuated.

Th aea hc i stkn f a evre m 6. The compliant bag constitutes an exit buffer which eliminates storage in a bulky reservoir, the volume of the compliant bag being negligible with respect to the rate of air evacuated during long periods.

7. The use of an ejector for carrying out the invention enables intimate mixing of any amount of a gas injected under pressure and air sucked into the ejector.

8. An ejctor of small size constitutes a particularly simple and reliable means enabling prompt delivery of the ir necessary for repeatedly filling the compliant bag.

9. The compliant bag remains at constant pressure and a valve disposed at -the air inlet of the ejector allows the composition of the air delivered by the ejector to be varicd over a very broad range.

The combination of an ejector communicating directly with a compliant bag in accordance with the invention thus makes it possible to constantly provide any amount of air having the required composition.

JI, -The -possibility of considerably varying the composition as well as the flow rate of the air delivered according to the invention.

12. The invention is thus carried out by means of a particularly simple combination of very reliable elements whose number and size are reduced to the strict minimum necessary for delivering any amount of air having the required composition and enabling prolonged respiration.

The compliant bag used for carrying out the invention may have any desired form and its dimensions may be reduced and adapted to any amount of air required for respiration.

Various variants and modifications may be envisaged in the framework of the present invention with respect to the devices described for example.

Instead of controlling the repeated filling of the compliant bag by means of a switch with a retarder, one could also use two switches, particularly proximity switches, arranged respectively at a lower limit and at an upper limit of the volume of the compliant bag so as to control the opening as well as the closing of the electrovalve at the beginning and at the end of each filling period.

One may also advantageously use similar means comprising a source of oxygen under pressure for delivering oxygen-eriched air.

Various intensive training tests carried out by high-level athletes while breathing oxygen-depleted air, provided in accordance with the invention by means of a device such as that described, have shown satisfactory operation of said device and have provided promising results, particularly an appreciable increase in the maximum consumption of oxygen.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

Claims

1. A method of obtaining any amount of modified air required for respiration, comprising: filling a compliant bag with modified air at ambient pressure, said compliant bag being capable of undergoing rapid changes in volume at ambient pressure without elastic deformation; drawing off modified air at ambient pressure for respiration via a suction tube .communicating with said compliant bag; and repeating step to fill said compliant bag with modified air at ambient pressure eich ;ime the volume of said compliant bag reaches a predetermined lower limil. and drawing off modified air by step so as to withdraw any amount of modified air at ambient pressure required for respiration via said suction tube.

2. A device for obtaining any amount of modified air at atmospheric pressure required for respiration according to the method of claim 1, where the device includes the combination: a compliant bag that can be rapidly filled with modified air at ambient pres:ure; a suction tube communicating with said compliant bag and enabling the modified air at ambient pressure required for respiration to be withdrawn via said suction tube; a valve associated with a source of modified air for filling said compliant bag; and a switch associated with a wall of said compliant bag and arranged to open said valve in order to supply modified air whereby to fill said compliant bag with modified air at ambient pressure each time the volume of the compliant bag reaches a lower limit, 20 wherein said compliant bag is adapted to be filled with modified air at arbient pressure each time its volume reaches said lower limit and thereby enables any amount of modified air required for respiration to be withdrawn fiom said compliant bag via said suction tube-

3. The device of claim 2, further including an ejector constituting said source of modified air and having a first inlet connected to a source of gas under pressure via said valve, a second inlet communicating with the atmosphere and an outlet communica:ing directly with said compliant bag, so that the gas under pressure may be injected in a predetermined ratio to ambient air drawn into said injector and thereby fill said compliant bag with modified air at S: ambient pressure having any composition required for respiration.

4 The device of claim 3, wherein the first inlet of said ejector is connected to a source of 30 nitrogen under pressure in order to fill said compliant bag with hypoxic air wiih an adjustable, reduced oxygen concentration.

A method of obtaining any amount of modified air required for respiration substantially as hereinbefore described with reference to Figs. 1 to

6. A device for obtaining any amount of modified air at atmospheric pressure required for respiration substantially as hereinbefore described with reference to Figs. 1 to Dated this 30th day of April 2003 PATENT ATTORNEY SERVICES Attorneys for JEAN-BAPTISTE MENUT *o