GB2117101A

GB2117101A - Flow system for controlling the temperature of blood

Info

Publication number: GB2117101A
Application number: GB08235278A
Authority: GB
Inventors: Christoph Drechsler; Friedrich Gropp
Original assignee: Medizin und Labortechnik Leipzig VEB
Current assignee: Medizin und Labortechnik Leipzig VEB
Priority date: 1981-12-15
Filing date: 1982-12-10
Publication date: 1983-10-05
Also published as: GB2117101B; SE8207133D0; SE8207133L; CS245280B1; FR2518884B1; DD206626A3; FR2518884A1; DE3236678A1

Abstract

A one-way flow system with a flat bag 1 for heating, warming up or cooling blood and having a labyrinthine construction formed from a plurality of lumina 4 which are different sizes in length and diameter and which are disposed vertically side by side between an inlet 2 and an outlet 3. The lumina 4 are connected to one another at the top and bottom via deflection sections 5. The webs 11 separating the first lumen from the second and the third lumen from the fourth are perforated in the upper portion 12 and the last luman 13 is provided with air-bubble traps 14. <IMAGE>

Description

SPECIFICATION Flow system for controlling the temperature of blood The invention relates to a one-way flow system with a flat bag for heating, warming up or cooling blood. This may be inserted in a heat exchanger in thermal communication therewith. The bag is connected, with regard to signals, to a measuring circuit which measures the blood temperature at the inlet and outlet of the bag and regulates the operation of the heat exchanger to keep the blood temperature constant at the outlet.

There is already known an apparatus for heating liquid, particularly a cooled liquid such as blood, to a predetermined nominal temperature before dispensing it at rates of flow which are variable over a considerable predetermined range.

The apparatus consists of a housing with a heating chamber for heating the liquid inside the apparatus, and the liquid flows through the heating chamber with an input and an output temperature. The apparatus has at least one electrical heating element which can be fed with current and which is in thermal communication with the liquid in the heating chamber to heat the liquid during its passage through the apparatus.

The apparatus also has a control circuit which responds to the input and output temperature of the liquid to deliver a heating-element control signal depending both on the output temperature and on the rate of flow or throughput of the liquid, and an electric switch circuit connected between the heating elements and the electric current source. This switch circuit responds to the heating-element control signal to control the current applied to the heating element, in order to keep the liquid at a predetermined nominal or desired temperature regardless of fluctuations in its rate of flow or throughput (DE-OS 28 02 993). In this apparatus, all the lumina are isomorphous so that the free flow through of the liquid cannot be guaranteed.

A further disadvantage consists in that the air bubbles occurring during the filling of the apparatus to heat the liquid, cannot be seen and are not intercepted so that complications in the transfusion of blood cannot be excluded.

The present invention seeks to avoid the disadvantages of the known apparatuses for heating liquids. In particular an object of the invention is to provide a device which is uncomplicated in construction, reliable in operation and always ready for operation.

According to the present invention there is provided a one way flow system comprising a flat bag for heating or cooling blood and having a labyrinthine construction, the bag comprising a plurality of interconnected generally parallel lumina which are arranged to be disposed vertically between an inlet and an outlet and which have differing lengths and diameters.

The present invention provides a one-way flow system for the heating, warming up or cooling of blood, which renders possible a blood transfusion while ensuring a high degree of safety with regard to the patient.

The lumina may first have an increasing length and then one which becomes shorter again in the flow path and their cross-sections may become smaller as the length increases and their crosssections become larger as they become shorter.

Apertures in the webs between the lumina may have widths of passage of different sizes, and the aperture provided with the smallest dimension of passage may be the one disposed furthest away from the end of the web. All the webs may be apertured in the upper portion.

The inlet of the last lumen and the crosssection of the last lumen may be equally large as or larger than the cross-section of the first lumen.

The labyrinthine construction can -result from welding two transparent webs of foil, and their surface formed by the lumina may have an antiadhesion coating reducing the flow resistance.

The bag may further be provided with a heating element welded on or in, which can be constructed in the manner of a metallic strip and the course of which may be adapted to the labyrinthine construction of the one-way flow system. With this solution, the use of a heat exchanger is eliminated. In this case, the first lumen may be exposed to the pump action of a roller pump.

Thus there is provided a one-way flow system with a flat bag which includes a bag system in labyrinthine form with flow-line reversal points which are in the form of radii. A free passage of the blood is rendered possible with the simultaneous formation of pressure differences, and entrained air bubbles are immediately detected through the transparent material and are intercepted by the air-bubble traps disposed in alternate sequence in the last lumen.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawing which shows a bag with a one-way flow system.

As the drawing shows, the one-way flow system is produced in a flat blood heating bag 1 which can be inserted in known manner in a heat exchanger not illustrated here and can be brought into thermal communication therewith. It is connected, as regards signals, to a known measuring circuit which measures the blood temperature at the inlet side 2 and outlet side 3 of the blood heating bag 1 and regulates the operation of the heat exchanger to keep the blood temperature constant at the outlet side 3. The one-way flow system has a labyrinthine construction and is formed from a plurality of lumina 4 of different size in length and diameter.

The lumina 4 are disposed vertically beside one another between an inlet side 2 and an outlet side 3 at the same height, and are connected to one another at the top and bottom via deflection sections 5 with different deflection radii 6. The webs 1 1 separating the first lumen 7 from the second lumen 8 and the third lumen 9 from the fourth lumen 10 are perforated in the upper portion 12 and the last lumen 13 is provided with air-bubble traps 14 in alternate sequence. The interrupted separating webs 11 ensure in all cases a free throughput of the filled medium. A build-up of an air cushion is prevented without pressure differences occurring. The air bubbles flowing in generally settle in the deflection sections 5 and are finally arrested by the air-bubble traps 14.

The lumina 4 at first have a length increasing in the direction of flow, then becoming shorter again, and as the length increases, their cross-sections become smaller and as they become shorter, their cross-sections become larger. Thus a certain backing up is achieved as a result of which a partial settling of the air bubbles in the circuit is excluded. As a result of the exclusion of all air bubbles, including the oxygen released by the heating of the blood, the effect is further achieved that no reduction in the temperature transfer value occurs. The apertures 15 in the webs 11 have widths of passage of different sizes, and the aperture 15 provided with the smallest passage dimensions is disposed furthest away from the deflection section 5. The other webs 16, interrupted by the upper deflection sections 5, may also be perforated in the upper portion 12.As a result, various differences in the compressed-air and flow velocities in the system are compensated and the most favourable solution from the flow point of view is ensured. The inlet 1 7 into the last lumen 13 and the cross-section of the last lumen 13 are equally large as or larger than the crosssection of the first lumen 7. Thus a more rapid pressure drop is achieved.

The labyrinthine construction of the blood heating bag 1 results from the welding of two transparent webs of foil. The surface formed by the lumina has an anti-adhesion coating which reduces the flow resistance and which reduces the surface resistance of the foil surface in such a manner that a destruction of the blood cells is excluded. The blood heating bag can be provided with a heating element (not shown) which is welded on or in and which is constructed in the manner of a metallic strip and the course of which is adapted to the one-way flow system. The first lumen 7 can be exposed to the pump action of a roller pump (not shown).

A flexible tube may, however, also be introduced into the first lumen 7 of the bag 1 at the inlet side, which tube is inserted in a roller pump and during big operations is inserted in the closed outer blood circuit.

Claims

1. A one-way flow system comprising a flat bag for heating or cooling blood and having a labyrinthine construction, the bag comprising a plurality of interconnected generally parallel lumina which are arranged to be disposed vertically between an inlet and an outlet and which have differing lengths and diameters.

2. A system according to claim 1 wherein the inlet and outlet are at the same height.

3. A system according to claim 1 or 2 wherein the lumina are connected at the top and bottom via deflection sections.

4. A system according to any preceding claim wherein the web separating a first lumen from a second lumen, and the web separating a third lumen from a fourth lumen are apertured at their upper region.

5. A system according to claim 4 wherein the apertures in the webs have widths of passage of different sizes, the aperture provided with the smallest passage dimension being the lowest one.

6. A system according to any preceding claim wherein all the webs between the lumina are apertured at their upper region.

7. A system according to any preceding claim wherein a final lumen is provided with air bubble traps.

8. A system according to claim 5 wherein the air-bubble traps are arranged alternately on the sides of the final lumen.

9. A system according to any preceding claim, wherein the lumina have a length which first increases in the course of flow then becomes shorter again.

10. A system according to claim 7, wherein as the lengths of the lumina increase, their crosssections become smaller and as they become shorter, their cross-sections become larger.

11. A system according to any preceding claim wherein the inlet into the final lumen and the cross-section of the final lumen are equally large as or larger than the cross-section of the first lumen.

12. A system according to any preceding claim wherein the labyrinthine construction is formed by welding together two transparent sheets of foil.

13. A system according to claim 12 wherein the surfaces of the sheets which form the lumina have an anti-adhesion coating to reduce the flow resistance.

14. A system according to any preceding claim wherein the bag is provided with a heating element which is welded on or in and which is constructed in the manner of a metallic strip and the course of which is adapted to the labyrinthine construction.

15. A system according to any of claims 1 to 13 comprising a heat exchanger in thermal communication with the bag.

16. A system according to claim 15, comprising a circuit which detects the temperature at the inlet and the outlet and which regulates the operation of the heat exchanger to keep the temperature constant at the outlet.

17. A system according to any preceding claim wherein the first lumen is exposed to the pump action of a roller pump.

18. A one way flow system substantially as herein described with reference to the accompanying drawing.