Rebreathing system with carbon dioxide absorbers

Abstract

A system and method is registered which allows the breathing air containing carbon dioxide gas to be bound in an absorber in a rebreathing device, wherein the absorber is formed by soda lime and / or caustic soda and is separated by means of a membrane which is predominantly permeable to carbon dioxide.

Description

[0001] The invention relates to a rebreathing system according to the preamble of claim 1. Such systems are known, for example, from the publications US 2019 / 0038859 A1, WO 2022 / 096147 A1, DE 103 00 141 A1 and US 2 966 235 A.

[0002] Rebreathing systems are well known. These are systems used, for example, by divers, firefighters, and anesthesia systems. In this system, a portion of the inhaled gas is first at least partially freed of carbon dioxide using an absorber, and then a portion of the exhaled gas is rebreathed by the user.

[0003] In anesthesia systems, part of the gas exhaled by the patient is also at least partially freed of carbon dioxide by means of an absorber, provided with an inhalation anesthetic and then part of the exhaled gas is re-inhaled by the patient.

[0004] At www.abfallmanager-medizin.de / you can read: "If an anesthesia rebreathing system takes over ventilation during surgery, patients not only need to be supplied with oxygen, but also the exhaled carbon dioxide (CO2) must be removed from the breathing air. To do this, the exhaled air within the anesthesia machine is passed through a carbon dioxide absorber containing soda lime. The soda lime acts as a filter that removes the CO2 from the air, which is then enriched with fresh gas and recirculated to the patient. The absorber filling must be changed regularly, and the used soda lime must be disposed of."

[0005] This explains the procedure and its disadvantages very well.

[0006] The site further explains: "Soda lime is a fine-grained medical product with high absorption capacity. The most commonly used soda lime products in Germany primarily contain calcium dihydroxide (Ca(OH)2). Sodium hydroxide (NaOH) and calcium chloride (CaCl2) are also sometimes added, along with an average of 16 percent water. Soda lime should be stored in closed containers in a dry place at a constant temperature and protected from direct sunlight. Once opened, containers must be used immediately or within four weeks at the latest."

[0007] Replacement and disposal of soda lime.

[0008] The absorber's soda lime filling must be changed regularly. This is mandatory when the CO2 concentration reaches 1 percent. Furthermore, for anesthesia machines used daily, a fixed schedule applies, even if the soda lime shows no signs of depletion. Routine changes should occur at least once a month. Due to its chemical composition, soda lime is classified as hazardous waste and must be disposed of according to waste code number 180106*.

[0009] The disadvantages of the process, in addition to the above-mentioned problem of disposal as hazardous waste, are that soda lime is classified as hazardous waste due to its chemical composition and that soda lime must be stored in a dry place at uniform temperatures and protected from direct sunlight.

[0010] Another disadvantage is that the load on the soda lime cannot be measured and therefore a "... fixed time schedule ..." requires the replacement of the soda lime, even if "... it does not yet show any signs of exhaustion."

[0011] Other sources also highlight the disadvantages of soda lime.

[0012] Exhaustion of the absorption capacity of the soda lime - exhaustion and fading of the color indicator under intense light irradiation - drying out of the soda lime, thereby increasing the risk of absorption and / or chemical reaction of inhalation anesthetics with the lime.

[0013] During the absorption of CO2 the soda lime heats up. Exhausted soda lime becomes hard and dry and can no longer heat up, but can react with inhalation anesthetics.

[0014] The patient’s breathing stream has so far come into direct contact with the soda lime.

[0015] The soda lime must be stored in a dry place at a constant temperature and protected from direct sunlight.

[0016] A routine change should take place at least once a month, even if there are no signs of exhaustion.

[0017] Due to its chemical composition, soda lime is classified as hazardous waste and must be disposed of carefully and in accordance with waste code number 180106*.

[0018] Once opened, containers must be consumed immediately or within four weeks at the latest.

[0019] The use of a color indicator is a highly unreliable method for monitoring the absorption capacity of the soda lime.

[0020] The following aspects are relevant for the user when choosing a suitable product: risks of use (especially exhaustion, release of toxic substances), CO2 absorption capacity (e.g. “service life”), absorption of inhalation anesthetics (e.g. during infusion), dust formation.

[0021] Source: https: / / www.dgai.de / alle-docman-dokumente / entschliessungenvereinbarungen / 939-januar-2019-atemkalk-hinweise-zu-korrektem-umgang-und-fachgerechter-nutzung-in-rückatemsystemen-stellungnahme-der-kommission-fuernormung-und-technische-sicherheit-der-dgai / file.html

[0022] The object of the invention is to develop a device that does not have the aforementioned disadvantages.

[0023] This problem is solved by the features of claim 1.

[0024] For this purpose, it is intended to realize the safe separation of absorbers and breathing air by means of at least one membrane and to use a dry substance, e.g. soda lime and / or a liquid substance, preferably caustic soda, as an absorber for the CO2 from the breathing air.

[0025] Sodium hydroxide has the advantage that it can be stored well even under robust conditions and no changes are to be expected under the influence of temperature and light.

[0026] The caustic soda is supplied in sturdy plastic containers and is easy to use as a liquid. If the containers remain tightly sealed, it can be stored almost indefinitely.

[0027] The lye does not need to be changed regularly when conductivity is measured. The conductivity measurement serves as a test for the anesthesiologist during preparation and as a clear source of information during surgery.

[0028] The brine filling of the absorber container naturally needs to be changed when its absorption capacity decreases. This is mandatory, regardless of the absorber material, when the CO2 concentration of the patient's breathing air reaches 1%. Measuring the conductivity of the brine provides the anesthesiologist with an additional source of information about the absorber's saturation.

[0029] An automatic visual and / or acoustic warning is therefore very easy to implement. This provides quality management with storable documentation.

[0030] During prolonged use of the rebreathing system, the lye is improved or replaced by adding fresh lye and removing contaminated lye without interrupting normal operation, i.e., patient ventilation. This is preferably done by gravity, although the use of pumps and a regulated exchange system is also conceivable and feasible.

[0031] The breathing air is passed over the at least one membrane, preferably a membrane bundle (11), and the CO2 diffuses through the semipermeable membrane material, preferably silicone materials, into the absorber on the other side of the at least one membrane, preferably into the lye (5) or into the soda lime (13 and 14) and is chemically bound there.

[0032] The membranes can be designed in any geometric shape, preferably tubular membranes, although flat or rectangular membranes are also applicable. Tubular membranes can preferably be designed so that the breathing air is guided through the interior of the tubular membrane, with the absorber arranged outside the membrane. Alternatively, the breathing air can be guided outside the tubular membrane, with the absorber arranged inside the tubular membrane.

[0033] A further embodiment of the process allows the use of the known soda lime (13 and 14) as a CO2 absorber. Here, too, the breathing air is separated from the absorber by the at least one membrane (11) described above.

[0034] For this purpose, the soda lime is to be poured into a bulk container, for example, with the outer surface made of a porous material. The bulk container has a window made of glass or clear plastic, allowing the familiar color change of the absorber to be monitored.

[0035] The required number of bins are placed in a container (4) in which the membranes (11) are arranged so that the patient's breath flows through or, depending on the design, past the membranes. After a short period of action, the soda lime creates a CO2-free space (15) through absorption around the membranes or membrane bundle. This creates a potential difference that drives or pulls the CO2 molecules through the semipermeable membrane, thus removing them from the breathing air.

[0036] Furthermore, it is provided to surround the membrane, the membranes or preferably the membrane bundle with a bed (14) of soda lime, whereby the advantage of consistent separation of the breathing air from the absorber material also comes into play here.

[0037] Another advantage of caustic soda is that it can be produced easily and inexpensively from caustic soda beads and distilled water in a conventional manner. The caustic soda beads are easy to store as a dry mass and have a long shelf life. If caustic soda is out of stock or if emergency situations result in high demand, caustic soda is immediately available to produce the required caustic soda solution. Examples of embodiments.List of reference symbols 1 collection room for CO2-free breathing air 2 Outlet of CO2-free breathing air 3 Flow direction of CO2-free breathing air 4 Housing made of solid, rigid or flexible material 5 Liquid absorbent, preferably sodium hydroxide solution 6 Absorbent inlet 7 Inflow of breathing air containing CO2 8 Condensate collection chamber 9 Collection room and distributor of CO2-laden breathing air 10 Drain liquid absorbent 11 membranes, preferably tubular membranes 12 Conductivity sensor 13 Soda lime in porous containers 14 membranes in bulk soda lime

[0038] The Fig. Figure 1 shows an example of the described process. The air flows via (7) into the collection chamber and distributor (9) and then into the tubular membranes (11). The CO2 in the air diffuses through the membranes (11) into the liquid absorbent (5) in the container (4), where it is bound. The CO2-free air flows in direction (3) into the collection chamber (1) to the outlet (2) and is available for further use. The conductivity sensor (12) provides information about the saturation of the absorber. Saturated absorber can continuously flow out via the outlet (10), and fresh absorber can continuously flow in via the inlet (6).

[0039] The Fig. Figure 2 shows an example of the described process. The air flows through (7) into the collection chamber and distributor (9) and then into the tubular membranes (11). The CO2 in the air diffuses through the membranes (11) into the porous container (13) filled with soda lime and is bound in the soda lime. The CO2-free air flows in direction (3) into the collection chamber (1) to the outlet (2), where it is available for further use.

[0040] The Fig. Figure 3 shows an example of the described process. The air flows via (7) into the collection chamber and distributor (9) and then into the tubular membranes (11). The CO2 in the air diffuses through the membranes (11) into the loosely poured soda lime in container (14) and is bound in the soda lime. The CO2-free air flows in direction (3) into the collection chamber (1) to the outlet (2) and is available for further use.

Claims

[1] Rebreathing system with a housing (4) through which exhaled breathing air can be passed, wherein a carbon dioxide absorber (13) is arranged in the housing (4), in particular with which carbon dioxide in the breathing air can be reduced, wherein the housing (4) is divided into two housing sections by means of at least one membrane (11) permeable to carbon dioxide, in particular which is impermeable to the absorber (13), wherein a first housing section comprises the absorber and the breathing air can be passed through the second housing section, characterized by in that in the first housing area the absorber (13) is arranged without contact with the membrane surface of the at least one membrane (11), for which purpose a solid absorber (13) is arranged in at least one gas-permeable container in the first housing area. [2] System according to claim 1, characterized by that the absorber (13) is formed by soda lime. [3] System according to claim 1 or 2, characterized byin that the at least one membrane (11) is designed as a tubular membrane (11), wherein the breathing air can be conducted through the interior of the at least one tubular membrane (11), in particular all the inner lumens of a plurality of tubular membranes (11) form the second housing region, and the absorber (13) is arranged in the first housing region formed around the at least one tubular membrane (11), or the breathing air can be conducted through the second housing region formed around the at least one tubular membrane (11), and the absorber (13) is arranged in the inner lumen of the at least one tubular membrane (11), in particular wherein all the inner lumens of a plurality of tubular membranes (11) form the first housing region. [4] System according to one of the preceding claims, characterized by that the at least one membrane (11) is made of silicone, in particular as a silicone tube. [5] System according to one of the preceding claims, characterized byin that the first housing region comprising the absorber (13) has a source connection through which the absorber (13) can be introduced into the first housing region and has a sink connection through which the absorber can be led out of the first housing region, in particular wherein a conveying device is provided with which the absorber (13) can be conveyed from the source connection to the sink connection through the first housing region, in particular intermittently or continuously, preferably the conveying device is gravity-driven or comprises a pump. [6] System according to one of the preceding claims, characterized bythat a measuring device is arranged in the first housing area, with which the loading of the absorber (13) with carbon dioxide can be measured, in particular so that an anaesthetist has access to a chemical-electronic source of information about the saturation of the absorber (13), preferably wherein an automatic optical and / or acoustic warning can be triggered if a loading limit value is exceeded. [7] System according to one of the preceding claims, characterized by that with the solid absorber (13), in particular soda lime, the CO2 can be bound in the first housing area by absorption and thus a CO2-free space (12) can be created in the first housing area, wherein the resulting CO2 potential difference draws the respiratory CO2 through the semi-permeable membrane (11) into the resulting CO2 vacuum and binds to the absorber (13).

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