PROCESS AND DEVICE FOR SEPARATING CARBON DIOXIDE FROM A BREATHING GAS MIXTURE BY MEANS OF A FIXED SITE CARRIER MEMBRANE

Abstract

A process and a device are provided for separating carbon dioxide from a breathing gas mixture by means of a “Fixed Site Carrier” membrane. The breathing gas mixture is guided in the device on a side of a selective, semipermeable membrane, which is provided with amine groups, which are bound covalently to a polymer. Through the membrane, the transport of the components of the gas mixture can take place. The membrane is selected to be such that the permeability for CO2 is substantially higher than the permeability for the other gas components of the breathing gas mixture. The membrane has or is associated with means for guiding the gas, which acts to guide the gas mixture on one side along the membrane. The membrane separates volume areas in which different CO2 partial pressures prevail from one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view showing a counterflow hollow fiber membrane module for carrying out the process according to the present invention; and

FIG. 2 is a schematic view showing the overall design of the selective, semipermeable membrane with the asymmetrical support structure with the larger pores on the left-hand side of FIG. 2 and with the selective, semipermeable layer applied, designated by “a,” on the right-hand side on the support structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, FIG. 1 shows a counterflow hollow fiber membrane module, with hollow fibers 1, integrated in the expiratory branch of the breathing gas guide as a separating element for separating carbon dioxide from the expiratory breathing gas mixture, which may contain, among other things, halogenated hydrocarbons. This counterflow hollow fiber membrane module has a number of hollow fibers 1 extending in parallel, whose walls are formed by a selective, semipermeable membrane. The positions of the hollow fibers 1 extending in parallel are stabilized by their ends being molded in a common molding 2, 2′. The openings of the hollow fibers 1 remain non-closed. The entire module is shaped in the form of a cylinder, whose jacket surface is formed by a gas-impermeable wall 3. The moldings 2, 2′ are sealingly connected to the gas-impermeable wall 3. The hollow fibers 1 extending in parallel pass through the interior of the cylinder, and gas transport between the interior of the hollow fibers 1 and the intermediate space between the hollow fibers 1 is possible only through the membrane. The interior space of the cylinder represents a volume area that is at least partially limited by the membrane. Two openings 4, 5, one of which can be used as an inlet opening 4 and the other as an outlet opening 5, pass through the jacket surface of the cylinder.

Flow can pass through the counterflow hollow fiber membrane module in two paths. The first path passes through the hollow fibers 1 arranged in parallel, and the second through the openings 4, 5 in the jacket surface of the cylinder. The two flow paths are separated from one another by the membrane of the walls of the hollow fibers 1 only. If gas mixtures that differ in terms of their CO₂ partial pressures flow through the flow paths, the CO₂ passes through into the volume with the lower CO₂ partial pressure due to the selective permeability. The direction of the partial pressure gradient makes, in principle, no difference for the mode of action according to the present invention. The flow path through the hollow fibers 1 is integrated into the expiratory branch of the breathing gas guide of the anesthesia apparatus 50 in this example. The second flow path is used for passing through air as the flushing gas. It is guaranteed hereby that carbon dioxide, whose concentration is increasing, is flushed rapidly out of the intermediate space between the hollow fibers 1, as a result of which a CO₂ partial pressure that corresponds to the ambient air will always approximately prevail on the side of the selective permeable membrane facing away from the breathing gas mixture.

A further increase in the performance capacity of the process according to the present invention can be achieved if the outlet opening 5 is connected to a vacuum pump 6, which lowers the overall pressure in the intermediate space between the hollow fibers 1 and if air is admitted as a flushing gas optionally through a pneumatic throttle 7.

The openings 8 of the hollow fibers 1 on the left-hand side of the module form the breathing gas inlet. The openings 9 of the hollow fibers 1 on the right-hand side of the module form the breathing gas outlet.

In a preferred embodiment, the counterflow hollow fiber membrane module acting as a CO₂-separating element is equipped with a memory element 10, which is designed especially as a transponder, can be read in a wireless manner and contains a model identification and/or operating parameters and/or characteristics of the element for identification and/or calculation of the state of consumption or the remaining use time of the element. The evaluation or calculation is carried out especially in a computing unit of the anesthesia apparatus or respirator, which uses the separating element.

FIG. 2 shows the design of the semipermeable membrane. The pore structure is such that the pore diameter decreases from one side of the membrane to the other.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A process for separating carbon dioxide (CO2) from a breathing gas mixture, the process comprising: providing a selective and semipermeable membrane which is provided with amine groups bound covalently to a polymer;guiding a breathing gas mixture on one side of the selective and semipermeable membrane such that transport of the components of the gas mixture takes place through the selective and semipermeable membrane.

2. A process in accordance with claim 1, wherein the breathing gas mixture contains halogenated hydrocarbons and transport of the components of the gas mixture results in a separation of CO2 from the breathing gas mixture.

3. A process in accordance with claim 2, wherein the transport of CO2 takes place with a selectivity of at least 50 relative to the transport of halogenated hydrocarbons.

4. A process in accordance with claim 1, wherein the breathing gas mixture is guided along one side and air is guided as a flushing gas on the other side of the membrane under substantially equal overall pressure, the membrane having a selectivity of at least 500 for CO2 relative to N2.

5. A process in accordance with claim 1, wherein a CO2 partial pressure that is below 500 Pa is set on the side of the membrane facing away from the breathing gas mixture.

6. A process in accordance with claim 5, wherein the partial pressures of N2, CO2 and H2O are set by a flushing gas on a side of the membrane facing away from the breathing gas mixture.

7. A process in accordance with claim 5, wherein the partial pressures of N2, CO2 and H2O are set by lowering the overall pressure on the side of the membrane facing away from the breathing gas mixture.

8. A process in accordance with claim 5, wherein the partial pressures of N2, CO2 and H2O are set by a flushing gas and simultaneously lowering the overall pressure on the side of the membrane facing away from the breathing gas mixture.

9. A process in accordance with claim 1, wherein the breathing gas mixture is guided along one side of the membrane and a flushing gas is on the other side of the membrane and the selectivity of the membrane for CO2 relative to N2 decreases in proportion to the partial pressure of N2 on the flushing gas side and is below 500 Pa.

10. A process in accordance with claim 1, wherein a relative humidity of at least 60% is set on at least one side of the membrane during the separation of CO2 at the membrane.

11. A process in accordance with claim 10, wherein the relative humidity is set by at least one of expiratory breathing gases from the breathing gas mixture and by an additional humidification source.

12. A device for separating CO2 from a breathing gas mixture, the device comprising: a breathing gas mixture flow space through which a breathing gas mixture flows;another gas flow space;a separating element comprising a selective semipermeable membrane separating volume areas of said breathing gas mixture flow space and said another gas flow space on each side of said selective semipermeable membrane, said selective semipermeable membrane defining a breathing gas mixture guide on one side of said selective semipermeable membrane for forming a separating element, said selective semipermeable membrane comprising amine groups bound covalently to a polymer, through which transport of the components of the gas mixture can take place, said selective semipermeable membrane having a permeability for CO2 that is substantially higher than the permeability for the other gas components of the breathing gas mixture, said selective semipermeable membrane guiding the gas mixture along the membrane to separate said volume areas on each side of said selective semipermeable membrane in which different CO2 partial pressures prevail from one another.

13. A device in accordance with claim 12, wherein the breathing gas mixture flow contains halogenated hydrocarbons and the selective semipermeable membrane is provided with a porous support structure, which is resistant to halogenated hydrocarbons and through which the transport of CO2 takes place at a selectivity of at least 50 relative to the transport of halogenated hydrocarbons.

14. A device in accordance with claim 12, wherein a CO2 partial pressure that is below 500 Pa prevails on a side of the membrane facing away from the breathing gas mixture.

15. A device in accordance with claim 12, further comprising a gas flushing means provided in communication with said another gas flow space for gas flushing of the side of the membrane facing away from the breathing gas mixture.

16. A device in accordance with claim 12, further comprising an evacuating means for evacuating the volume area of said another gas flow space, which is limited at least partially by the membrane and is located on the side of the membrane facing away from the breathing gas mixture.

17. A device in accordance with claim 12, further comprising: a gas flushing means provided in communication with said another gas flow space for gas flushing of the side of the membrane facing away from the breathing gas mixture; andan evacuating means for evacuating the volume area of said another gas flow space, which is limited at least partially by the membrane and is located on the side of the membrane facing away from the breathing gas mixture.

18. A device in accordance with claim 12, further comprising moistening means for moistening the membrane on the side of the breathing gas mixture.

19. A device in accordance with claim 12, further comprising moistening means for moistening the side of the membrane facing away from the breathing gas mixture.

20. A device in accordance with claim 12, wherein said membrane contains buffer substances, including one of trihydroxymethylaminomethane, borates or carbonates, which maintain the pH value above a value of 7.

21. A device in accordance with claim 12, in combination with one of an anesthesia apparatus or respirator wherein said breathing gas mixture flows from said anesthesia apparatus or respirator.

22. A device in accordance with claim 12, wherein said separating element further comprises a support structure in the form of a counterflow hollow fiber membrane module supporting said selective semipermeable membrane.

23. A device in accordance with claim 12, wherein said separating element further comprises a support structure in the form of a counterflow flat membrane module supporting said selective semipermeable membrane.

24. A device in accordance with claim 12, wherein said separating element further comprises a support structure in the form of a cross-flow flat membrane module supporting said selective semipermeable membrane.

25. A device in accordance with claim 12, wherein said separating element further comprises a support structure in the form of a wound membrane module supporting said selective semipermeable membrane.

26. A device in accordance with claim 12, wherein said selective semipermeable membrane is formed of polyvinylamine and is connected to an asymmetrically porous hollow fiber membrane as a support structure or is applied to same, the membrane being arranged on the side of the small pore sizes of the support structure.

27. A device in accordance with claim 26, wherein the porous hollow fiber membrane consists of polysulfone, polyacrylonitrile, cellulose acetate or polyether sulfone.

28. A device in accordance with claim 12, wherein the separating element is equipped with a memory element, which can be read in a wireless manner, can be written to and is designed as a transponder and contains a model identification and/or operating parameters and/or characteristics of the element for identification and/or calculation of the state of consumption or the remaining use time of the element, the calculation being carried out in a computing unit of an anesthesia apparatus or a respirator.