Abstract:
A method and device for removing gas from gas containing blood. A non-rotating cyclone eddy chamber has the blood circulating therein and centrifugal force separates the blood radially outward and the gas radially inward. The cyclone inlet comprises a blood inlet channel that extends in a helical circular form developed to narrow in funnel like manner in the direction of flow toward the cyclone eddy chamber to accelerate the blood flow entering that chamber tangentially. A gas outlet is arranged in the radially inner center of the cyclone eddy chamber path while the blood outlet is coaxial and outward of the gas outlet.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and device for removing gas from gas containing blood by operation of a centrifuging device. 
     This type of device is disclosed in British A-2 063 108. Further devices for separating gas from gas containing blood are described in U.S. Pat. Nos. 3,785,380, 4,368,118, 4,388,922 and 5,451,321, as well as in German DE-C-36 24 363 and 36 41 644 and DE-A-43 29 385. 
     Blood given to a patient should not contain any air or other gas, even in the form of micro-small bubbles of gas. The blood is fed to the patient by a pressure pump. Although that is the preferred field of use of the invention, it does not exclude the invention also being used to remove air from blood which is drawn from a patient at the site of a wound, since it frequently cannot be avoided that air is also drawn into the bloodstream at the site of the wound. The air must be removed from the blood as rapidly as possible and as close as possible to the wound since it can otherwise damage the blood. Other possible fields of use of the invention are the removal of gas from gas-containing blood which is transported from one instrument to another or to a container. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to improve the efficiency of the gas removal and, in particular, to provide a method and a device with which even micro-small bubbles of gas can be removed from gas containing blood, even if the gas containing blood is being conveyed in a large volume per unit of time. 
     The invention concerns a method and device for removing gas from gas containing blood. A non-rotating cyclone eddy chamber has the blood circulating therein and centrifugal force separates the blood radially outward and the gas radially inward. The cyclone inlet comprises a blood inlet channel that extends in a helical circular form developed to narrow in funnel like manner in the direction of flow toward the cyclone eddy chamber to accelerate the blood flow entering that chamber tangentially. A gas outlet is arranged in the radially inner center of the cyclone eddy chamber path while the blood outlet is coaxial and outward of the gas outlet. 
     Other objects, features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE FIGURE 
     FIG. 1 diagrammatically shows, in part in axial section, a device in accordance with the invention for removing gas from gas containing blood. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a source of blood  2 , which may be a device known in medicine, for instance, a blood oxygenator, a heart-lung machine, a blood filter, a reservoir, a cardioplegia system, a plasmaphoresis system, a dialysis system, or some other blood transfusion system. The blood source is connected by a pressure pump  4  to an input  6  of a cyclone, eddy current device  8  and conducts blood through the device  8  to a patient  10  or an instrument. This instrument or the patient  10  is connected via a hose  12  to a cyclone outlet channel  14  of the cyclone eddy current device  8 . 
     The cyclone eddy current device  8  contains, arranged coaxially one behind the other along a linear center axis  16 , a housing  18  of circular cross section with its inlet  6  at one axial end and its outlet channel  14  on the other axial end. The housing inlet  6  has, arranged axially one behind the other, an inlet section  20  which widens in funnel like manner in the direction of flow, followed by a cylindrical channel section  22  and then by a cyclone eddy chamber section  24  which narrows down in a funnel like manner in the direction of flow and forms the circumferential wall of a cyclone eddy chamber  26  which narrows down in a funnel like manner in the same way. The gas containing mixture of blood rotates with constant direction of rotation within the cyclone eddy chamber  26  from the axial inlet starting point of the chamber to the axial outlet end of the chamber. Here, the mixture of blood and gas is separated by centrifugal force into a radially outer blood phase (blood portion) and a radially inner gas phase (gas portion). The downstream end  28  of the cyclone eddy chamber  26  is connected to the upstream starting point of the outlet channel  14  and forms a cyclone outlet for the blood phase. 
     Within the channel section  22  of the housing  18  and coaxial to the center axis  16 , there is an insert body  30  which has at least one wider diameter helical rib  32 . Between adjacent coils of the rib and the body  30 , at least one helical groove  34  is formed. Together, the surrounding wall of the housing, which the rib  32  engages, the groove or grooves  34  define a helical blood inlet channel  36 . The blood inlet channel  36  extends from a point downstream of the inlet  6  up to the upstream starting point  38  of the cyclone eddy chamber  26  to there defines a substantially tangential cyclone inlet  40  from which the gas containing blood flows substantially tangentially into the cyclone eddy chamber  26 . The blood then flows in a cyclone eddy current up to the end  28  of the chamber, and after passing that end and further rotating, it passes into the outlet channel  14 . The cyclone eddy chamber  26  can be developed so as to narrow in funnel shape over its entire length, as shown in FIG. 1, or it may have a circular cylindrical shape, at least at its upstream initial section. The funnel like narrowing shape of the cyclone eddy chamber  26  is to maintain the cyclone centrifugal energy over the entire axial length of the cyclone eddy chamber  26 . 
     The diameter  44  of the insert body  30  at the base of the grooves  34  is smallest at the upstream starting point  46  of a groove and increases downstream in the direction of flow up to the cyclone inlet  40 , i.e., the diameter of the groove decreases and its volume decreases. The channel section  22  of the housing  18  which limits the grooves  34  at the outside circumference can have a shape other than circular cylindrical. In any event, it is so shaped that the helical blood inlet  36  defined by the ribs  32 , the grooves  34  and the channel section  22  has, at least over a part of its length but preferably over its entire length, a flow cross section which becomes continuously smaller in funnel like manner in the direction of flow so that the gas containing blood is accelerated downstream in it and flows with the greatest possible speed into the cyclone eddy chamber  26 . 
     The ribs  32  can rest against the channel section  22  or be a small distance in from it. On its upstream starting point, the insert body  30  preferably has a conical tip  48  directed opposite the flow of blood. At its downstream end, the body  30  has a conical tip  50  directed narrower in the direction of flow. Instead of such conical tips  48  and  50 , the insert body  90  may also have rounded or flat end surfaces. 
     The angles shown in the drawing have preferably the following size ranges: angle α between the center line  16  and a generatrix of the insert body  30  on the bottom of the grooves  34 : 0° to 30°; angle β between the channel section  22  of the housing  18  and the cyclone eddy chamber section  24  of the housing  18 : 0° to 45°; the angle γ between the center line  16  and an end of the rib  32  transverse to the center line  16 : 45° to 80°, and the angle δ of the downstream conical tip  50  between the center line  16  and the generatrix of this conical tip  50 : 90° to 150°. If the angle α between the center line  16  and the lengthwise line on the bottom of the grooves  34  is 0° or only a few degrees, then the lengthwise line of the channel section  22  should pass in the direction of flow of the blood obliquely to the center line  16  so that the grooves  34  of the blood inlet channel  36  have a cross sectional size which becomes narrower in wedge like manner in the direction of flow of the blood. As another possibility for developing the grooves  34  and thus also the blood inlet channel  36  in a manner which narrows down in funnel like manner in the direction of flow, the distance between the ribs  32  continuously decreases in the direction of flow. In these ways, the height and/or width of the grooves  34  can be changed to gradually decrease the volume of the groove downstream. 
     The gas containing blood which enters tangentially into the cyclone eddy chamber  26  at the cyclone inlet  40  flows in the form of a cyclone eddy current, through the cyclone eddy chamber  26  to its outlet end  28 . This produces centrifugal forces which force the blood phase or blood portion of the gas containing blood into the radially outer cyclone eddy current region. As the blood phase is heavier than the gas contained in the blood, this forces the gas or the gas phase into the radially inner cyclone eddy current region. The cyclone eddy current travels into the outlet channel  14 . 
     Within the radially inner center of this cyclone eddy current, a gas outlet opening  16  is arranged coaxial to the center line and facing in the direction opposite the axial flow of the blood phase and the gas phase, so that the gas phase can flow only from a small cross-sectional region in and around the center line  16  into the gas outlet opening  60 . The gas outlet opening  60  can, for instance, be arranged up to 10 cm downstream of the downstream end  28  of the cyclone eddy chamber  26 , and this is shown by a gas line  62  arranged coaxially in the outlet channel  14  or at the downstream end  28 , as shown in dashed line at  64 , or even upstream of the end  28 , as shown diagrammatically at  66 . In all cases, the gas outlet opening  60  is located coaxially on the center line  16  and is directed opposite the axial direction of flow of the gas phase and the blood phase. 
     In the embodiment shown, the inlet  6 , the eddy chamber  26 , the outlet channel  14 , the gas outlet opening  60 , and at least the initial section of the gas line  62  within which the gas outlet opening  60  is formed are all arranged coaxial to the linear center line  16 . 
     In a modified embodiment of the invention, the direction of the inlet  6  can lie in a region which is between an axial direction and a tangential direction to the center line  16 , the tangential direction pointing in the same circumferential direction as the grooves  34 , so that the flow of blood is not reversed when entering the chamber  26 . Furthermore, the direction of the blood outlet channel  14  and/or the direction of the gas outlet opening  60  and of its gas line  62 , or at least of the initial section of this gas line  62 , can lie in a region between the axial forward direction in accordance with FIG.  1  and the tangential direction of movement of the cyclone eddy current. 
     Although the present invention has been described in relation to a particular embodiment thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.