A blood reservoir comprises a rigid casing and a perforated tubular member positioned within the casing and extending between the edges thereof. An inlet aperture is at a position at the upper end of the reservoir in communication with the bore of the tubular member while an outlet aperture is positioned adjacent the bottom of the casing exterior to the tubular member. The bore of the tubular member contains first blood-defoaming means, and the tubular member carries a blood filter. In accordance with this invention, second blood defoaming means are positioned about the exterior of the tubular member to dissipate the fine bubbles without interference from the larger bubbles, which have been previously removed by passage through the first blood defoaming means.

BACKGROUND OF THE INVENTION 
Cardiotomy reservoirs are currently used in major surgical procedures, such 
as open heart surgery, for receiving blood from a cardiotomy sucker and 
other sources, for defoaming the blood, filtering out debris, and 
returning it to the patient. 
In U.S. Application Ser. No. 901,323 filed May 30, 1978, by Thomas W. 
Crockett, et al. and entitled "Improved Cardiotomy Reservoir", a reservoir 
for blood is disclosed, having a rigid casing and a perforated tubular 
member positioned within the casing and extending between the ends 
thereof. Blood defoaming material is positioned within the tubular member, 
and a filter is carried by the tubular member so that blood clots and 
larger bubbles cannot escape from the interior of the filter member to the 
exterior. 
Other designs of cardiotomy reservoirs are known, for example, a cardiotomy 
reservoir similar to that disclosed in U.S. Pat. No. 3,993,461, its 
predecessor in design being as disclosed in U.S. Pat. No. 3,891,416. In 
both of these cardiotomy reservoirs, a hollow casing is provided in which 
a tubular member is positioned within the casing and extends between the 
ends thereof. Blood enters the bottom of the tubular member rising 
upwardly until it passes out of an aperture to the exterior of the tubular 
member. 
In accordance with this invention, the above described type of cardiotomy 
reservoir is improved by the use of a double stage defoaming structure. 
As in the previously cited patent application, the defoaming sponge within 
the tubular member may be surrounded by a fine weave filter netting, which 
confines large gas bubbles to the region containing the first defoaming 
sponge material. Small bubbles, however, may pass through the filter 
screen. 
In the structure of this invention, those small bubbles which do pass 
through the filter screen to the area which is outside of the tubular 
member encounter a second defoaming sponge, where they also are broken 
down. Unlike the situation in the first defoaming means, the second stage 
can dissipate the fine bubbles without interference from the large 
bubbles, which can tend to create small bubbles and inhibit their 
dissipation. 
Also, the structure of this invention may be adapted so that small bubbles 
which are formed or otherwise reside within the reservoir outside of the 
tubular member and fine weave filter netting may easily enter into contact 
with the second defoaming means for further bubble removal. 
DESCRIPTION OF THE INVENTION 
There is disclosed herein a blood reservoir which comprises a rigid casing, 
a perforated tubular member positioned within the casing and extending 
between the ends thereof, and inlet aperture means positioned at the upper 
end of the reservoir in communication with the bore of the tubular member, 
to provide fluid communication from the exterior to the bore. 
The bore contains first blood defoaming means, while the tubular member 
carries blood filter means to filter fluid passing through the 
perforations of the tubular member. An outlet aperture is positioned at 
the bottom of the casing, exterior to the tubular member. 
In accordance with this invention, second blood defoaming means are 
positioned about the exterior of the tubular member to dissipate fine 
bubbles without interference from larger bubbles previously removed by the 
first blood defoaming means. 
Preferably, the second blood defoaming means are enclosed in a tubular, 
coarse-weave cover, capable of allowing small bubbles outside of the cover 
to pass therethrough into contact with the second blood defoaming means. 
Thus, bubbles which are generated or otherwise reside exterior to the 
tubular member and fine weave filter netting can be dissipated with the 
assistance of the second blood defoaming means. 
The first and second blood defoaming means may be separated by the blood 
filter means, with the filter member being of tubular shape and fine-weave 
construction. This permits the filter, which is made of generally 
hydrophilic material, to retain larger bubbles to prevent their passage 
from the inside to the outside of the filter means. Typically, the 
tubular, fine-weave filter member may have a pore size of, for example, 
120 to 130 microns, and may be made of a nylon material. 
Because of the second stage blood defoaming means present in accordance 
with this invention, a significant improvement in the performance of the 
cardiotomy reservoir of this invention is provided over those of the prior 
art.

Referring to the drawings, the cardiotomy reservoir which is shown herein 
is similar in its design to the cardiotomy reservoir of the Crockett, et 
al. patent application No. 901,323, filed May 30, 1978, entitled "Improved 
Cardiotomy Reservoir", except as otherwise indicated herein. 
Cardiotomy reservoir 10 comprises a rigid housing 12 which may be made from 
a pair of shells 14, 16, sealed together about flanges 18 by 
radio-frequency sealing, solvent sealing, or the like. Casing 12 may be 
made of a transparent acrylic plastic or similar material. 
Casing 12 encloses a perforated tubular member 20, which may be made out of 
polyethylene, or other similar plastic, and typically carries numerous 
perforations 22 so that the walls of the tubular member can pass fluid. 
The upper end of tubular member 20 is positioned within an annular gasket 
24 which may be made out of silicone rubber, and which fits about flange 
26 positioned at the end of shell 14 about aperture 15 in a sealing 
manner. 
The lower end of tubular member 20 rests in an annular ledge 28 of a plate 
30. Plate 30 is retained by a silicone rubber end plug 34, defining an 
aperture which surrounds protrusion 36. Protrusion 36 is part of inwardly 
upstanding hump 38, which is defined at the bottom end of shell 16. 
Tubular member 20 carries, preferably about its exterior, a tubular nylon 
filter screen 35, which may have a mesh size of about 125 microns for 
filtration of the blood and the retention of debris. 
A fine weave filter 35 is folded at its upper end about the upper end of 
tubular member 20, inside of slot 39 of silicone rubber gasket 24, for 
frictional retention of the ends of tubular filter 35. At the lower end, 
filter 35 passes under plate 30, and then fits through the central 
aperture of plate 30, between the plate and plug 34, for frictional 
retention. Filter 35 may have a pore size on the order of 120 to 130 
microns, specifically 125 microns. 
Annular trough 40 is defined about hump 38 in shell 16, and is angularly 
positioned to define an acute angle to the longitudinal axis of tubular 
member 20. 
Outlet aperture 46 communicates through the lowest portion of trough 40, so 
that all blood will easily drain from the reservoir. 
If desired, a calibration strip having volume indication markings may be 
provided on an outer wall of the reservoir so that, at a minimum blood 
level, blood volumes as small as 25 or 50 cc. can be measured. 
A mass of conventional blood defoaming sponge 23 is positioned within tube 
20. 
At the upper end of reservoir 10, inlet members are defined, being of a 
configuration similar to that of the previously described patent 
application of Crockett, et al. 
An aperture is defined by a sleeve member 54 which passes through casing 12 
and in which is fitted luer lock connector 56 for the addition of 
supplemental medication when desired. The connector 56 may be of 
conventional design. 
Vent tube 58 may be provided with a closable rubber vent cap 60. If 
desired, a porous, hydrophobic material may be placed in vent tube 58, to 
filter out any contamination, while permitting the flow of gas into and 
out of the reservoir. 
A port tube (not shown) may also be present to be used as a connection to a 
vacuum pump, if desired. 
Positioned within sleeve 26 is a molded inlet assembly 62, which is also of 
a design similar to the cited Crockett, et al. application, including 
three inlet aperture tubes 66. 
In accordance with this invention, the conventional blood defoaming sponge 
23 positioned in the interior of tube 20 may be supplemented with a second 
blood defoaming means, which constitutes a generally tubular mass of 
conventional blood defoaming sponge material 68 such as silicone coated 
metal turnings, positioned about the exterior of tube 20. Second blood 
defoaming means 68 is retained in its position by means of a tubular 
coarse-weave fabric cover 70, which is retained at its ends in a manner 
similar to the retention of tubular filter 35. The weave of tubular cover 
70 may be coarse enough (e.g., an aperture size on the order of 1/16 or 
1/32 inch) to allow any small bubbles outside of the cover 70 to pass back 
into the area occupied by second defoaming means 68 to be dissipated. 
Cover 70 may, for example, be a knit material. This provides an advantage 
to the device of this invention, since the presence of fine weave filter 
member 35 has hitherto generally prevented the passage of such bubbles 
back into the interior of tube 20 for dissipation. 
Accordingly, blood enters the device through an inlet port 66, spilling 
through the first defoaming means 23 and then passing out of tube 20 
through fine weave filter member 35. Any large bubbles are prevented from 
passage by the presence of fine weave filter 35. Any small bubbles which 
remain pass through the second defoaming means 68 in the absence of larger 
bubbles. Blood and bubbles external to the outer coarse-weave retainer 
member 70 are free to pass relatively unhindered back to the second 
defoaming sponge 68, which tends to increase the removal rate of such fine 
bubbles. 
Blood is then withdrawn through outlet 46, with the sloping trough 40 
serving to facilitate the complete drainage thereof. 
The above has been offered for illustrative purposes only, and is not to be 
viewed as limiting the invention of this application, which is as defined 
in the claims below.