FR2750869A1 - BREATHING APPARATUS WITH CLOSED CIRCUIT OPERATION - Google Patents

Abstract

A closed-circuit breathing apparatus is disclosed. The apparatus comprises a breathing bag constituting a counterlung (5) in air communication with a facepiece (1) to be applied to the subject for which the apparatus is intended so that the air exhaled by the subject is sent to the false. lung and that the air inhaled by the subject comes from the counterlung, this device comprising a filter cartridge (4) containing a substance capable of transforming the carbon dioxide in the exhaled air into oxygen, this device being characterized in that the cartridge filter is accompanied by an active carbon filter (2) and a thermal sponge (3), in that the filter (2) and the thermal sponge (3) and the filter cartridge (4) are placed in this order on the path of the exhaled air and in reverse order on the path of the inspired air.

Description

The invention relates to a closed circuit breathing apparatus. The

  closed-circuit breathing apparatus where the exhaled air is regenerated by an appropriate substance, generally KO2 (super potassium oxide), are well known and are distinguished from each other by the means used to overcome the very high temperature of the gases regenerated by the reaction, strongly exothermic, which transforms the

carbon dioxide in oxygen.

  In its basic principle, a device of this type essentially consists of a 4- to 6-liter respiratory bag known as a "false lung", connected to the respiratory tract by means of a filter cartridge containing KO2. The air in the "false lung" is then

  breathed in 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 KO2, the CO2 is fixed by a reaction which produces oxygen in replacement of 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 KO2 cartridge, then at a temperature of more than C. To lower the temperature of the inspired gases , it is known to substitute for simple pendular breathing, breathing where the paths of the inspired and exhaled gases are separated by a set of conduits and valves so that the hot gases cool partially in the "false lung",

  from where they will be taken up directly on inspiration.

  The temperature of the inspired gases is thus reduced to 50-60 C, a temperature still high enough to require the exclusive use of a mouthpiece, which avoids contact of the gases on the external periphery of

the mouth.

  To ensure the first inspiration when taken in the mouth, known devices are equipped with a device for producing

  a few liters of oxygen to initially fill 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 KO2 is increased due to a single passage of the gas through the filter cartridge by respiratory cycle. The present invention overcomes these drawbacks by proposing a simple pendulum circuit compatible with the use of a

  mask and does not require initial oxygen injection.

  This is achieved according to the invention with a breathing apparatus operating in closed circuit, comprising a respiratory bag constituting a false lung in air communication with a face piece to be applied to the subject to whom the apparatus is intended so that the air expired by the subject is sent to the false lung and the air inspired by the subject comes from the false lung, this apparatus comprising a filter cartridge containing a substance capable of converting the carbon dioxide of the exhaled air into oxygen, this apparatus being characterized in that the filter cartridge is accompanied by an active carbon filter and a thermal sponge, in that the filter and the thermal sponge and the filter cartridge are placed in this order on the path of the exhaled air between the face piece and the false lung, and in reverse order on the

path of inspired air.

  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 consists of metal chips

  compact forming a porous layer of 10 to 20 millimeters.

  - the false lung is provided with a means of admitting air into

the lungs.

  - 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.

  A preferred embodiment of the invention will be described below with reference to the single figure of the accompanying drawing which is a view

in principle of this realization.

  A half mask (1) connects the respiratory system to the subject's airways. It leads successively to: * a filter element (2) containing activated carbon and intended to eliminate any pollutants which may have initially entered the

  circuit by 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

crossing the sponge.

  * element (4) is a filter cartridge containing 150 to 200 g

  of crushed or pelletized KO2, as is known.

  * element (5) is the "false lung", flexible and waterproof bag

  can hold 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 it to open and, thereby, an entry of ambient air. As long as the bag contains gas and does not get

  _25 not collabe during respiratory movements, this valve remains closed.

  The device works as follows: When the device is initially put in place, the "false lung" (S) is naturally empty of air and the first inspiration attempts to collapse the bag (5), which opens the valve (6) and lets in a volume of ambient air

  corresponding to the volume of inspiration.

  If this air contains pollutants (odors, smoke, ...), the filter (2)

  will fix these pollutants on activated carbon.

  If this filtration is not complete during the first respiratory cycle, the circuit being closed thereafter, it will continue during the following cycles. This filter is therefore relatively discreet and can advantageously consist of a layer of 4 to 6 millimeters of synthetic foam,

  porous, impregnated with activated carbon.

  Following the first inspiration, the exhaled gases

depleted in 02 and enriched in C02.

  During their passage on the KO2 in (4), the CO2 reacts with the KO2 to produce oxygen to replace that consumed by the subject. The very exothermic reaction heats the KO2, which rises to a

temperature of almost 150 C.

  The respiration being pendular, the inspired gases leave the KO2 cartridge at almost 100 C, but transfer this heat into the thermal sponge (3), which rises only a few degrees above its average temperature, limited to 40-45 C. Indeed, if the sponge heats up on inspiration, the gases exhaled at 37 C cool it during expiration. The oxygen supplied by the reaction on the KO2 is actually in

  amount slightly greater than that consumed by the subject.

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

evacuate this too full.

  Since a device uses a mouthpiece, this

valve is absolutely necessary.

  In the case of the present invention, if a half is used

  mask, this acts as an overflow valve insofar as a respiratory suppression takes it off from the face and thereby ensures the escape of

excess circulating air.

  The invention does not however exclude the possibility of inserting an exhaust valve, which may possibly be 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 exemplary embodiment.

Claims (5)

Claims   1. Breathing apparatus operating in closed circuit, comprising a respiratory bag constituting a false lung (5) in air communication with a face piece (1) to be applied to the subject to which the apparatus is intended so that the air exhaled by the subject is sent to the false lung and the air inspired by the subject comes from the false lung, this apparatus comprising a filter cartridge (4) containing a substance capable of converting the carbon dioxide of the exhaled air into oxygen, this apparatus being characterized in that the filter cartridge is accompanied by an active carbon filter (2) and a thermal sponge (3), in that the filter (2) and the thermal sponge (3) and the filter cartridge (4) are placed in this order on the exhaled air path and in   reverse order on the path of the inspired air.   2. The apparatus of claim 1, wherein said substance   is or includes super potassium oxide.   3 Apparatus according to one of claims 1 or 2, wherein the   activated carbon filter (2) consists of a layer of 4 to 6 millimeters of a porous carbonaceous foam.   4. Apparatus according to one of claims 1 to 3, wherein   the thermal sponge (3) consists of compact metal shavings   forming a porous layer of 10 to 20 millimeters.   5_ Apparatus according to one of claims 1 to 3, wherein the   false lung (5) is provided with an outside air intake means (6) in the false lung.   6. Apparatus according to claim 5, wherein said outside air intake means (6) 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 less than the external pressure.   7. Apparatus according to one of the preceding claims, in   which said face piece (1) is a half mask.