EXTRACORPOREAL CIRCUIT FOR REMOVAL OF CO2 FROM BLOOD

Abstract

The present invention concerns an extracorporeal circuit for removing CO.sub.2 from blood comprising a blood withdrawal line for withdrawing blood from the patient, a filtration unit for producing plasma water and a line for returning the blood to the patient, defining a main circuit; the extracorporeal circuit further comprises a decarbonating group comprising a secondary circuit for the recirculation of plasma water, means for removing a fraction of said plasma water, a CO.sub.2 exchanger, a cationic resin charged with H+ ions set upstream of the CO.sub.2 exchanger and adapted to generate acid plasma water, means for the infusion of the acid plasma water upstream of the CO.sub.2 exchanger and means for the infusion of ions in a solution downstream of the CO.sub.2 exchanger.

Claims

1. An extracorporeal circuit (1, 100, 200, 300, 400, 500) for removing CO.sub.2 from blood comprising a blood withdrawal line (2) for withdrawing blood from a patient, a filtration unit (6) for producing plasma water (30) and a line for returning the blood (5) to the patient, defining a main circuit (40); said extracorporeal circuit being characterised in that it comprises a decarbonating group (4) comprising a secondary circuit (7) for recirculation of plasma water, means (12) for removing a fraction of said plasma water (30), a CO.sub.2 exchanger (9), a cationic resin charged with H+ ions (10) set upstream of said CO.sub.2 exchanger (9) and adapted to generate acid plasma water (30a), means (15) for infusion of said acid plasma water (30a) upstream of said CO.sub.2 exchanger (9) and means (11) for infusion of ions in a solution downstream of said CO.sub.2 exchanger (9).

2. The extracorporeal circuit according to claim 1, characterised in that said filtration unit (6) is a filter selected from the group consisting of a haemodialysis filter, a haemofilter and a dialyser.

3. The extracorporeal circuit according to claim 1, characterised in that said cationic resin charged with H+ ions is selected from the group consisting of a cationic resin provided with sulphonic group and cationic resin provided with carboxylic groups.

4. The extracorporeal circuit according to claim 1, characterised in that said CO.sub.2 exchanger (9) is present on the main circuit (40) on said line for returning the blood (5) to the patient downstream of said filtration unit (6).

5. The extracorporeal circuit according to claim 1, characterised in that said CO.sub.2 exchanger (9) is present on said secondary circuit (7) downstream of said cationic resin charged with H+ ions (10).

6. The extracorporeal circuit according to claim 1, characterised in that it further comprises a gas trap arranged upstream of said CO.sub.2 exchanger (9) and downstream of said cationic resin charged with H+ ions (10).

7. The extracorporeal circuit according to claim 1, characterised in that it further comprises a group for removing calcium (16) arranged on the secondary circuit (7) for the recirculation of plasma water.

8. The extracorporeal circuit according to claim 7, characterised in that said group for removing calcium is a cationic exchange resin (16) charged with sodium and potassium ions.

9. The extracorporeal circuit according to claim 8, characterised in that said group for removing calcium (16) is positioned in parallel to said cationic resin charged with H+ ions (10).

10. The extracorporeal circuit according to claim 9, characterised in that said group for removing calcium (16) is positioned in series to said cationic resin charged with H+ ions (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a better understanding of the invention, it will now be described in detail for purely illustrative non-limiting purposes with the help of the figures of the attached drawings, in which:

[0024] FIG. 1 illustrates a first embodiment of the invention;

[0025] FIG. 2 illustrates a second embodiment of the invention;

[0026] FIG. 3 illustrates a third embodiment of the invention;

[0027] FIG. 4 illustrates a fourth embodiment of the invention;

[0028] FIG. 5 illustrates a fifth embodiment of the invention;

[0029] FIG. 6 illustrates a sixth embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] In FIG. 1 an extracorporeal circuit for removing blood according to a first embodiment of the present invention is indicated overall by 1.

[0031] The circuit 1 comprises a withdrawal line for withdrawing blood 2 from the patient, on which a pump 3 acts, for example a peristaltic pump, a filtration unit 6, for example a haemodialysis filter, a decarbonating group 4 and a line for returning the blood 5 to the patient. The withdrawal line for withdrawing blood 2 from the patient, the filtration unit 6, and the line for returning the blood 5 to the patient define a main circuit 40.

[0032] The haemodialysis filter 6 is connected to a secondary circuit 7 for recirculation of the plasma water 30, in this case dialysate, on which a pump 8 acts.

[0033] The decarbonating group 4 comprises a cationic resin charged with H.sup.+ ions 10 adapted to generate acid plasma water 30a positioned downstream of the pump 8 on the secondary circuit 7 of the plasma water 30.

[0034] The decarbonating group 4 further comprises an oxygenator 9 arranged on the main circuit 40 downstream of the haemodialysis filter 6 along the return line 5 for returning the blood to the patient.

[0035] Advantageously the cationic resin 10 is able to retain the calcium, potassium and magnesium ions but above all the sodium ions, present in large quantities in the plasma water 30, replacing them with H.sup.+ ions and generating acid plasma water 30a at the resin outlet.

[0036] Advantageously the acidification of the plasma water 30 causes a shift in the chemical balance (I) in favour of the gaseous CO.sub.2 in the acid plasma water 30a in recirculation. The gaseous CO.sub.2 is then removed by the action of the oxygenator 9, for example a bubble oxygenator. In this way, it is possible to improve removal of the CO.sub.2 from the plasma water 30a.

[0037] The acid plasma water 30a is returned to the haemodialysis filter 6, inside which it will function as a dialysis liquid, by means of the line 15. The blood flowing out of the haemodialysis filter 6 is then deprived of the CO.sub.2 by the oxygenator 9. The blood flowing out of the oxygenator 9 will therefore have an electrolytic imbalance due to the removal of cations by the cationic resin 10. To re-balance the concentration of the electrolytes in the blood before reinfusion to the patient, downstream of the oxygenator 9, along the line 5, means 11 are provided for the reinfusion of sodium, potassium, calcium and magnesium ions in solution to re-balance the quantity of cations lost at the level of the cationic resin 10. Said means 11 for the reinfusion of ions consist for example in one or more sacs 11a each containing an electrolytic solution, a pump 11b and an infusion line 11c. For example, an electrolytic solution comprising NaOH, KOH, NaCl or NaHCO.sub.3 can be infused and, separately, a solution comprising calcium ions and magnesium ions. Said solutions can also include glucose if CRRT is also performed.

[0038] The circuit 1 further comprises, upstream of the cationic resin 10, means 12 for removing part of the plasma water. Said means 12 for removing part of the plasma water consist, for example, of a removal line 12a, a peristaltic pump 12b and a discard tank 12c.

[0039] The removal of part of the plasma water is necessary to compensate for the increase in volume of the plasma water, which occurs following addition of the electrolytic solution through the means 11. Therefore, to respect the hydroelectric balance of the system, the quantity of water removed by the means 12 must be equal to the quantity of water reinfused with the electrolytic solution through the means 11.

[0040] Likewise, the electrolytic solution reinfused with the means 11 must contain a quantity of sodium, potassium, calcium and magnesium equal to that removed with the cationic resin 10 plus that removed with the means 12 for removing part of the plasma water.

[0041] Alternatively, when the circuit of the invention is used, not only for removing the CO.sub.2 but also for renal therapy, the quantity of water and electrolytes removed by the means 12 can be different from that reinfused with the means 11.

[0042] Lastly, the blood flowing out of the haemodialysis filter 6 is returned to the patient by means of a line for returning the blood 5.

[0043] In the circuit of FIG. 1, for example, the blood flowing out of the patient can be set to 200 ml/min, the flow of the plasma water through the cationic resin is therefore 10-25 ml/min.

[0044] FIGS. 2 to 6 illustrate alternative embodiments of the circuit of FIG. 1 according to the present invention; the details similar or equal to those already described are indicated for the sake of simplicity by the same reference numbers.

[0045] In particular, FIG. 2 illustrates a second embodiment of the invention which represents a variation 100 of the circuit illustrated in FIG. 1. In this case, the plasma water 30 flowing out of the haemodialysis filter is split into two flows, 30b and 30c respectively, at the connection point 14. Then part of the plasma water, indicated by 30c, is treated by the cationic resin 10, while the remaining part of the plasma water 30b is sent back to the connection point 17.

[0046] The acid plasma water 30a flowing out of the cationic resin 10 is recombined by means of the line 18 with the plasma water 30b and then conveyed along the line 15 to the oxygenator 9 which, in this embodiment, is on the secondary circuit 7.

[0047] Advantageously, this embodiment reduces the exogenous contact surface between the blood and the extracorporeal circulation system and reduces the pH variations to which the blood is exposed.

[0048] In this embodiment, for example, the blood flow leaving the patient can be set to 200 ml/min and the flow of the ultrafiltrate from the haemodialysis filter can be set to 400-1000 ml/min.

[0049] In FIG. 3 a third embodiment of the invention is illustrated which represents a variation 200 of the circuit illustrated in FIG. 1. In this case, the oxygenator 9 is positioned downstream of the haemodialysis filter 6 on the main circuit 40 on the line for return of the blood 5 to the patient and the plasma water flowing out of the cationic resin is returned to the main circuit of the blood on line 5 upstream of the oxygenator 9. In this embodiment, the oxygenator 9 is a membrane oxygenator. In this embodiment, for example, the blood flowing out of the patient can be set to 200 ml/min and the flow of the ultrafiltrate from the haemodialysis filter can be set to 10-25 ml/min.

[0050] In all the embodiments of the present invention, a gas trap can also be inserted downstream of the cationic resin 10 but upstream of the oxygenator 9 to further favour elimination of the carbon dioxide and prevent the accumulation of gas.

[0051] All the embodiments of the present invention can furthermore include a regional blood anticoagulation system. For example, the circuit of FIG. 1 can be modified as illustrated in FIG. 4. In particular, in the circuit 300, the plasma water flowing out of the haemodialysis filter 6 is split into two flows at the connection point 13. A part of the flow is directed to the cationic resin 10 while the remaining part is treated with a group for removal of the calcium, such as, for example, a cationic exchange resin 16 charged with sodium and potassium ions. Said resin 16 charged with sodium ions retains calcium ions, releasing sodium ions. The plasma water flowing out of the resin 16 charged with sodium ions is partly recombined with the acid plasma water 30a on the line 15 downstream of the cationic resin 10 and partly sent back on the line 2 upstream of the haemodialysis filter by means of the line 20 to carry out regional anticoagulation of the blood in the circuit. Restoration of the correct hydro-electrolytic balance in the blood is then carried out by the means 11 for the reinfusion of ions and the means 12 for removal of the plasma water.

[0052] The circuit of FIG. 2 can be modified as in FIGS. 5 and 6. In particular, in the circuit 400 of FIG. 5, a cationic exchange resin 16 charged with sodium and potassium ions is arranged upstream of the connection point 14 on the secondary circuit 7.

[0053] Alternatively, in the circuit 500 of FIG. 6, the cationic exchange resin 16 charged with sodium and potassium ions is present downstream of the oxygenator 9. In both cases part of the plasma water flowing out of the resin 16 is re-introduced into the circuit at the height of the withdrawal line for withdrawing blood from the patient 2 by means of the line 20 so as to cause regional anticoagulation of the blood.