EP0818217B1 - Closed circuit breathing apparatus - Google Patents

Description

The invention relates to a breathing apparatus made of closed circuit,

Respirators in a closed circuit where the exhaled air is regenerated by an appropriate substance, generally KO ² (super potassium oxide), are well known and are distinguished from each other by the means used to level the temperature very high of the gases regenerated by the reaction, strongly exothermic, which transforms carbon dioxide into oxygen.

In its basic principle, a device of this type essentially consists of a 4 to 6 liter respiratory bag called "false lung", connected to the respiratory tract via a filter cartridge containing the KO ² . The air contained in the "false lung" is then breathed in a closed circuit (pendulum breathing).

The gases thus recycled are, on the subject side depleted in oxygen and enriched in CO ² , while, after passing over the KO ² , the CO ² is fixed by a reaction which produces oxygen to replace that consumed by the subject.

In practice, such a configuration of the device has the major drawback of supplying, on inspiration, gases leaving directly from the KO ² cartridge, then at a temperature of more than 100 ° C.

To lower the temperature of the inspired gases, it is known to replace pendulum breathing simple, a breath where the gas paths inspired and expired are separated by a set of conduits and valves so that the hot gases partially cool in the "false lung", from where they will be taken directly to inspiration.

The temperature of the inspired gases is thus reduced at 50-60 ° C, temperature still high enough to require the exclusive use of a mouthpiece, which avoids contact of the gases around the outer periphery of the mouth.

To ensure the first inspiration during the taken in the mouth, known devices are equipped with a device for producing a few liters of oxygen for initially fill in the "false lung".

Generally intended for emergency evacuation, these devices are often for single use and their simplicity is an important asset.

The use of a mouthpiece and the choice of a selective circulation of gases (non-pendulum breathing) have two drawbacks: verbal communications are excluded, and the minimum necessary amount of KO ² is increased due to a single pass gases through the filter cartridge per respiratory cycle.

The publication EP 0 182 581 describes an apparatus pendulum type closed circuit breathing system which includes a respiratory bag constituting a false lung in gas communication with a facial means to be applied to the subject for which the device is intended so that the gases expired by the subject are sent to the false lung and that the inspired gases come from the false lung, this device comprising a filter cartridge capable of eliminating the gas carbon dioxide from exhaled gases and comprising a trap capable of absorb heat from gases from the cartridge filter, the trap and the cartridge being placed in this order in the expired gas path and in order reverse on the path of the inspired gases.

• la cartouche filtrante est conçue pour absorber le gaz carbonique sans recyclage de ce gaz ;
• le piège à calories est un échangeur chimique qui ne fonctionne que dans un sens ;
• il est nécessaire de prévoir un apport d'oxygène en permanence.

In this device:

• the filter cartridge is designed to absorb carbon dioxide without recycling this gas;
• the calorie trap is a chemical exchanger that only works in one direction;
• it is necessary to provide a supply of oxygen at all times.

The present invention relates to an apparatus realizing a simple pendulum circuit compatible with the use of a mask, freed from the above drawbacks.

According to the invention, this is achieved with an apparatus pendulum type respiratory system operating in closed circuit, comprising a respiratory bag constituting a false lung in gas communication with a room facial to apply to the subject for which the device is intended so that the gases exhaled by the subject are sent to the false lung and that the gases inspired by the subject come from the false lung, this device comprising a filter cartridge capable of removing carbon dioxide from exhaled gases and comprising a trap capable of absorbing heat in the gases coming from the filter cartridge, the trap and the cartridge being placed in this order on the path of the exhaled gases and in reverse order on the path of inspired gases, characterized in that said filter cartridge contains a substance suitable for converting carbon dioxide from exhaled gases to oxygen, in that said trap is a thermal sponge suitable for absorb the heat of gases by capacitive effect from the filter cartridge and able to cool in contact with the exhaled gases passing through it, in that the false lung is provided with an admission means for admitting outside air into the false lung when the pressure in the false lung is less than the pressure and in that the apparatus includes a filter active carbon, said filter, the thermal sponge and the filter cartridge being placed in this order on the path of the exhaled gases and in reverse order on the path of inspired gases.

A thermal sponge cannot work this way that in pendulum regime, the term sponge meaning well that any amount of heat drawn assumes that the previous was evacuated. The thermal trap described in prior art can be arranged in a circuit not pendulum (fig. 2), it clearly appears that it cannot be a thermal sponge.

It can also be noted that the the prior art works with a tip, while a important advantage of the present invention is to allow the use of a means other than a nozzle buccal, due to better gas cooling before inspiration.

• ladite substance est ou comprend du super oxyde de potassium.
• le filtre au charbon actif est constitué d'une couche de 4 à 6 millimètres d'une mousse poreuse carbonée.
• l'éponge thermique est constituée de copeaux métalliques compacts formant une couche poreuse de 10 à 20 millimètres.
• le faux poumon est muni d'un moyen d'admission de l'air dans le faux poumon.
• ledit moyen d'admission d'air extérieur est un clapet qui est normalement fermé et qui s'ouvre vers l'intérieur du faux poumon lorsque la pression dans le faux poumon est inférieure à la pression extérieure.
• lequel ladite pièce faciale est un demi-masque.

In the preferred embodiments, the apparatus of the invention also has one or more of the following characteristics:

• said substance is or comprises super potassium oxide.
• the activated carbon filter consists of a layer of 4 to 6 millimeters of porous carbon foam.
• the thermal sponge is made up of compact metal chips forming a porous layer of 10 to 20 millimeters.
• the false lung is provided with a means for admitting air into the false lung.
• said outside air intake means is a valve which is normally closed and which opens towards the inside of the false lung when the pressure in the false lung is lower than the external pressure.
• which said face piece is a half mask.

An embodiment will be described below. preferred of the invention with reference to the single figure of attached drawing which is a principle view of this production.

• un élément filtrant (2) contenant du charbon actif et destiné à éliminer d'éventuels polluants qui auraient pénétré initialement dans le circuit par l'élément (6) décrit ci-dessous.
• un élément (3) dit "éponge thermique" destiné à piéger les calories. Cette "éponge"est avantageusement constituée d'un tampon de copeaux métalliques, présentant une grande surface de contact et une haute capacité thermique. Lorsqu'un gaz chaud traverse l'éponge, un échange thermique s'effectue en rapport avec les capacités thermiques entre le gaz et le métal. Quelques degrés d'élévation de la température de l'éponge suffisent pour absorber près de 80% de la chaleur dans le gaz chaud. A l'expiration, les gaz à 37°C se réchaufferont en sens inverse en traversant l'éponge.
• l'élément (4) est une cartouche filtrante contenant 150 à 200 g de KO² concassé ou pastillé, ainsi qu'il est connu.
• l'élément (5) est le "faux poumon", sac souple et étanche pouvant contenir 5 à 6 litres d'air.
• l'élément (6) est un clapet s'ouvrant vers l'intérieur du sac, de telle sorte qu'une dépression dans le sac entraíne son ouverture et, par là, une entrée d'air ambiant. Tant que le sac contient du gaz et ne se collabe pas durant les mouvements respiratoires, ce clapet reste fermé.

A half mask (1) connects the respiratory system to the subject's airways. It successively leads to:

• a filter element (2) containing activated carbon and intended to eliminate any pollutants which may have entered the circuit initially through the element (6) described below.
• an element (3) called "thermal sponge" intended to trap calories. This "sponge" advantageously consists of a pad of metal chips, having a large contact surface and a high thermal capacity. When a hot gas passes through the sponge, a heat exchange takes place in relation to the thermal capacities between the gas and the metal. A few degrees of temperature rise in the sponge is enough to absorb almost 80% of the heat in the hot gas. At expiration, the gases at 37 ° C will heat in the opposite direction by passing through the sponge.
• the element (4) is a filter cartridge containing 150 to 200 g of crushed or pelletized KO ² , as is known.
• element (5) is the "false lung", flexible and waterproof bag that can contain 5 to 6 liters of air.
• the element (6) is a valve opening towards the inside of the bag, so that a depression in the bag causes its opening and, thereby, an entry of ambient air. As long as the bag contains gas and does not collapse during respiratory movements, this valve remains closed.

The device works as follows:

On initial installation of the device, the "false lung" (5) is naturally empty of air and the first inspiration tries to collab the bag (5), which opens the valve (6) and lets in a volume of air ambient corresponding to the volume of inspiration.

If this air contains pollutants (odors, smoke, ...), the filter (2) will fix these pollutants on the charcoal.

If this filtration is not complete on the first respiratory cycle, the circuit then being closed, it will continue during the following cycles. This filter is therefore relatively discreet and can advantageously be consisting of a layer of 4 to 6 millimeters of foam synthetic, porous, impregnated with activated carbon.

Following the first inspiration, the exhaled gases are depleted in O ² and enriched in CO ² .

During their passage on the KO ² in (4), the CO ² reacts with the KO ² to produce oxygen to replace that consumed by the subject. The very exothermic reaction heats the KO ² , which rises to a temperature of almost 150 ° C.

As the respiration is pendular, the inspired gases exit the KO ² cartridge at almost 100 ° C, but transfer this heat into the thermal sponge (3), which rises only a few degrees above its temperature. medium, limited to 40-45 ° C. In fact, if the sponge heats up during inspiration, the gases exhaled at 37 ° C cool it during expiration.

The oxygen supplied by the reaction on the KO ² is in reality slightly greater than that consumed by the subject.

As a result, the tidal volume breathed increases slowly, and there comes a time when the "false lung" bag (5) is full before the end of expiration. A valve opening to the outside is then necessary to evacuate this too full.

Insofar as a device uses a tip mouth, this valve is absolutely necessary.

In the case of the present invention, if one use a half mask, this acts as a valve too full since respiratory suppression takes it off the face and ensures, by this, the escape of excess circulating air.

The invention does not, however, exclude the possibility insert an exhaust valve, which can be possibly a mechanical means of reopening the valve (6), if the "false lung" takes up a volume exceeding a given value.

The invention is not limited to this example of production.

Claims (6)

1. Breathing apparatus of the pendular type with closed-circuit operation, the apparatus comprising a breathing bag constituting a false lung in gas communication with a face piece (1) suitable for applying to the subject for whom the apparatus is intended so that the gas breathed out by the subject is sent into the false lung and the gas breathed in by the subject comes out from the false lung, the apparatus including a filter cartridge (4) suitable for eliminating carbon dioxide gas from the breathed-out gas and including a trap (3) suitable for absorbing heat from the gas that comes from the filter cartridge, the trap and the cartridge being placed in that order on the path of the breathed-out gas and in the opposite order on the path of the breathed-in gas, the apparatus being characterized in that said filter cartridge contains a substance suitable for transforming the carbon dioxide of the breathed-out gas into oxygen, in that said trap is a heat sponge suitable for absorbing heat from the gas coming from the filter cartridge by a heat capacity effect, and suitable for cooling in contact with the breathed-out gases passing through it, in that the false lung (5) is provided with admission means (6) for admitting outside air into the false lung when the pressure in the false lung is lower than outside pressure, and in that the apparatus has an activated carbon filter (2), said filter (2), the thermal sponge (3), and the filter cartridge (4) being placed in that order on the path of the breathed-out gas and in the opposite order on the path of the breathed-in gas.
2. Apparatus according to claim 1, in which said substance is or comprises potassium super oxide.
3. Apparatus according to claim or claim 2, in which the activated carbon filter (2) is constituted by a 4 millimeter to 6 millimeter thick layer of a carbon-containing porous foam.
4. Apparatus according to any one of claims 1 to 3, in which the thermal sponge (3) is constituted by compact metal shavings forming a porous layer that is 10 millimeters to 20 millimeters thick.
5. Apparatus according to any one of claims 1 to 4, in which said air admission means (6) is a valve which is normally closed and which opens towards the inside of the false lung whenever the pressure inside the false lung is lower than outside pressure.
6. Apparatus according to any preceding claim, in which said face piece (1) is a half-mask.

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