IL92608A - Life support apparatus - Google Patents

Description

LIFE SUPPORT APPARATUS LIFE SUPPORT APPARATUS The present invention relates to life support apparatus, and particularly to apparatus for providing breathable gas, to one or more -persons in a hazardous environment over an extended period of time.

Hazardous environments may develop within confined spaces or in open areas as a result of natural disasters (e.g. , earthquakes, volcanic eruptions) , industrial releases or mishaps, ecological pollutant fallout, and other man-made or natural-made causes. Such hazardous environments may release toxic gasses which present dangers to a human being by inhalation, and/or by skin penetration, and may persist for extended periods of time. A hazardous environment may also exist naturally, e.g., oxygen-poor air at very high elevations, in space or under water.

One form of life support apparatus presently used for providing breathable gas in a hazardous environment includes a filter which removes the toxic gasses or contaminants. However, such a system is not reliable when the hazardous environment is present over an extended period of time, such as many days, since the filter may saturate or clog or otherwise fail.

Another form of life support apparatus includes a source of oxygen supplied from cylinders via a mask worn by each individual, the individual exhaling the air into the atomosphere. Such apparatus, however, requires a relatively large volume of oxygen which may not be available where the hazardous environment persists over an extended period of time, for example many days .

An object of the present invention is to provide life support apparatus which is particularly useful over an extended period of time.

According to the present invention, there is provided a life support apparatus for providing breathable oxygen to a person or group of persons in a hazardous environment particularly over an extended period of time, comprising: an enclosure for the person shielding at least the person's face from the hazardous environment; a respiration bag connected to the enclosure in a closed circuit through which breathable gas is circulated through the enclosure; a source of oxygen connected to the closed circuit for supplying oxygen thereto; a scrubber in the closed circuit for removing carbon dioxide from the breathable gas circulated through the enclosure; and control means for controlling the source of oxygen to maintain the oxygen content of the gasses in the respiration bag to be at least 18% in volume.

According to the preferred embodiment of the invention described below, the apparatus further includes a source of an inert gas also connected to the closed circuit and also controlled by the control means so as to intermittently add inert gas to the closed circuit.

In the described preferred embodiment, the control means adds the inert gas at predetermined intervals of time.

It will thus be seen that the life support apparatus constructed in accordance with the above features of the invention provides a closed circuit system in which oxygen, and/or oxygen-enriched air, is recirculated so as to minimize the amount of oxygen required to be added in order to maintain the oxygen concentration at the required minimum level of at least 20% by volume. If the life support appartus is used for periods of less than 20 hours, it is not critical to add the inert gas, but if it is used for a period exceeding about 20 hours, the inert gas is added at each such interval as it has been found that this makes the gas more suitable for breathing and less toxic to the person .

The inert gas may include any gas or mixture considered by the medical authorities as safe for inhalation when mixed with oxygen in the appropriate concentrations. For purposes of example, the inert gas is preferably nitrogen, but may also be argon, helium, or a mixture of any of such gasses.

In the described preferred embodiment, the source of oxygen comprises an oxygen reservoir, and a plurality of oxygen supplying devices supplying oxygen to the reservoir under the control of the control means. The oxygen supply devices may be any of the known devices which generate breathable oxygen alone, or with other chemical compounds, by the ignition of high oxygen compounds (e.g., chlorates), by the decomposition of high oxygen compounds (e.g., potassium superoxide, sodium superoxide, or peroxides), by chemical reaction, by electric or heat decomposition of oxygen containing compounds (such as water or certain organic compounds), or by containers containing the oxygen in compressed or liquified form.

In the described preferred embodiment, the oxygen supplying devices are ignitable oxygen candles, and the control means sequentially ignites the oxygen candles to maintain a minimum pressure in the oxygen reservoir.

The scrubber may include any compound, or mixture of compounds, that remove carbon dioxide, and preferably also excessive water vapour, from the exhaled mixture of gasses, preferably before it is mixed with the freshly withdrawn oxygen in the respiration bag. Examples of such compounds include soda lime, superoxides, alkalies, and various metal oxides. The carbon dioxide and excessive moisture vapour may be removed by chemical reaction or by absorption.

Preferably, the enclosure is a face mask worn by the person to enclose the person's face, thereby providing protection against inhalation of hazardous materials. The person could use safety clothing to thereby also protect skin penetrating poisons; alternatively, the enclosure may be in the form of a garment worn by the person to enclose the person's body and thereby to protect the complete body against the hazardous materials. The enclosure could also be a "clean room" enclosing a plurality of persons.

The apparatus may be constructed in accordance with the foregoing features in the form of a self-contained autonomous unit light in weight, independent of an external power supply, and flexible enough to allow its use for as long as the hazardous environment persists, even for many days. It can also be constructed in modular form capable of having additional supply devices (e.g., oxygen candles) added thereto as the hazardous environment persists.

For example, the apparatus could be embodied in a backpack for personal or team assignments in hazardous environments, such as for rescue teams and maintenance teams in severe fire or heavy smoke conditions, or for special medical, decontamination or rescue teams. The apparatus could also be installed in mobile units, such as fire engines, ambulances, vehicles, airborne platforms, or in stationary units such as fallout shelters or other permanent installations designed to support life of a plurality of individuals.

Further features and advantages of the invention will be apparent from the description below.

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a schematic diagram illustrating the major components of one form of life support apparatus constructed in accordance with the present invention; and Fig. 2 is a logic diagram illustrating the operation of the system of Fig. 1.

The apparatus illustrated in Fig. 1 comprises an enclosure, in the form of a face mask 2, equipped with a demand valve, for each person to shield the person's face from the hazardous environment; and a respiration bag 4 connected in a closed circuit to mask 2 by a mask inlet 6 and outlet tube 8. The closed circuit further includes a scrubber 10 for removing carbon dioxide and excessive moisture from the air exhaled by the user wearing the mask 2, before the exhaled air is returned to respiration bag 4. These may be several face masks connected in parallel closed circuits to the same respiration bag, or to separate respiration bags.

The respiration bag 4 is further connected via a tube 12 to a source of oxygen comprising an oxygen reservoir 14 supplied from a plurality of oxygen supply devices in the form of ignitable oxygen candles 16. The oxygen candles 16 are selectively ignitable, as will be described below, to generate oxygen and to supply the oxygen in gaseous form to the oxygen reservoir 14 via tubes 18, a selector valve 20, a oneway valve 22, and an inlet tube 24 into the oxygen reservoir. The oxygen from reservoir 14 is supplied to the respiration bag 4 via a pressure reducer 26, a tube 28, pressure gauge 30, and the previously-mentioned tube 12 leading to respiration bag.

The pressure within the oxygen reservoir 14 is sensed by a pressure sensor 32 which outputs an electrical signal to an electrical logic circuit 34. Circuit 34 serves as one input to a control system 36 which controls the ignition of the oxygen candle 16 by a battery (not shown) so as to maintain a predetermined minimum pressure within the oxygen reservoir 14.

The illustrated apparatus further includes a source of an inert gas 38 having a valve 40 also controlled by control circuit 36 to intermittently add inert gas to the respiration bag 4. In the example described below, this intermittent addition of the The pressure within the oxygen reservoir 14 is continuosuly monitored by sensor 32, and when the pressure is below a predetermined threshold, the sensor outputs a signal to logic circuit 34 which controls control circuit 36 to activate the next candle 16, and thereby to supply more oxygen to the oxygen reservoir 14. The oxygen from reservoir 14 is continuously supplied to respiration bag 4 via pressure-reduction valve 26, tube 28, pressure gauge 30, and tube 12, so that the gasses within the respiration bag include at least 20% oxygen by volume.

The oxygen-containing gas within respiration bag 4 is inhaled by the user via tube 6 and the user's face mask 2, and is exhaled via scrubber 10 and tube 8 back to the respiration bag 4. Scrubber 10 removes carbon dioxide and excessive moisture from the exhaled gas before the gas is returned to the respiration bag 4 for recirculation to the user's mask 2 via the closed circuit defined by tubes 6 and 8.

The pressure within the oxygen reservoir 14 is continuously monitored by sensor 32, and whenever the pressure drops below a predetermined minimum threshold (block 56), it causes the control circuit 36 to ignite another oxygen candle 16 to supply additional oxygen to the reservoir 14.

Timer 42 also continuousl monitors the time, and if more than 20 hours of use have elapsed (block 58), it causes the control circuit 36 to open valve 40 to introduce another quantity of nitrogen or other inert gas (box 60) into the respiration bag 4, so as to maintain approximately the initial concentration of inert gas in the gasses breathed by the user.

While the described system controls the replenishment of the oxygen content of the respiration bag 4 by continuously monitoring the pressure within the oxygen reservoir 14, it will be appreciated that the replenishment of the oxygen may be controlled in other ways, for example, by continuously monitoring the actual oxygen concentration in the respiration bag 4, or in the closed circuit between the bag and the user's mask 2. Also, while the inert gas from source 38 is added at predetermined time intervals (every 20 hours), the addition of the inert gas can also be controlled by a sensor which senses the actual concentration of the inert gas within the respiration bag 4 or in the closed circuit between that bag and the user's mask 2.

Further, while the inert gas supplied to this closed circuit is indicated as being nitrogen, it will be appreciated that it could be other inert gasses; and while the oxygen supply devices 16 are indicated as ; being ignitable oxygen candles, it will be appreciated that other oxygen supply devices could be used.

Many other variations, modifications and applications of the invention will be apparent.

Claims (11)

WHAT IS CLAIMED IS:

1. Life support apparatus for providing breathable oxygen to a person in a hazardous environment particularly over an extended period of time, comprising: an enclosure for the person shielding at least the person's face from the hazardous environment; a respiration bag connected to said enclosure in a closed circuit through which breathable gas is circulated through the enclosure; a source of oxygen' connected to said closed circuit for supplying oxygen thereto; a scrubber in said closed circuit for removing carbon dioxide from the breathable gas circulated through said enclosure; and control means for controlling the source of oxygen to maintain the oxygen content of the gasses in said respiration bag to be at least 18% in volume.

2. The apparatus according to Claim 1 , further including a source of an inert gas also connected to said closed circuit and also controlled by said control means so as to intermittently add inert gas to the closed circuit.

3. The apparatus according to Claim 2, wherein both said oxygen and said inert gas are added directly to said respiration bag.

4. The apparatus according to either of Claims 2 or 3, wherein said control means controls said source of inert gas to add the inert gas at predetermined time intervals.

5. The apparatus according to any one of Claims 2-4, wherein said source of inert gas includes nitrogen, argon, helium, or a mixture thereof.

6. The apparatus according to any one of Claims 1-5, wherein said source of oxyen comprises an oxygen reservoir and at least one oxygen supplying device supplying oxygen to said reservoir, said control means controlling the oxygen supplying device to maintain a minimum pressure in the oxygen reservoir.

7. The apparatus according to Claim 6, wherein the source of oxygen comprises a plurality of oxygen supplying devices for supplying oxygen to the oxygen reservoir, said control means controlling said plurality of oxygen supplying devices to maintain a minimum pressure in the oxygen reservoir.

8. The apparatus according to Claim 7, wherein said plurality of oxygen supplying devices are ignitable oxygen candles, said control means sequentially igniting said oxygen candles to maintain a minimum pressure in said oxygen reservoir.

9. The apparatus according to any one of Claims 1-8, wherein said scrubber also removes water vapour from the breathable gas circulated through said enclosure . . · ..,

10. The apparatus according to any one of Claims 1-9, wherein said enclosure is a face mask worn by the person to enclose the person's face.

11. Life support apparatus substantially as described with reference to and as illustrated in the accompanying drawings .