Heat exchanger and blood oxygenating device furnished therewith

The present invention provides a heat exchanger using hollow fibers formed of an organic polymer as the heat transfer tubes; a blood oxygenating device comprising a blood oxygenator combined with the aforesaid heat exchanger; and a small-sized and lightweight blood oxygenator which comprises a blood oxygenator of the hollow-fiber membrane type having the aforesaid heat exchanger incorporated thereinto to form an integral unit, and hence has excellent gas exchange and heat exchange performance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a heat exchanger using hollow fibers made of an 
organic polymer as the heat transfer tubes and capable of efficiently 
warming or cooling various fluids including liquids such as water or blood 
and gases such as air, oxygen or nitrogen and to a blood oxygenating 
device furnished with this heat exchanger. 
2. Description of the Prior Art 
Conventionally, various types of heat exchangers are known as devices for 
transferring heat from a high-temperature fluid to a low-temperature one. 
Most typical heat exchangers have a multitubular construction. For use as 
the material of heat transfer tubes in a heat exchanger of the 
multitubular type, metals having good heat conductivity are most 
effective. Among others, stainless steel pipes have been commonly used 
because of their excellent resistance to corrosion by the fluids involved 
in heat exchange. An effective method for installing stainless pipes in a 
heat exchanger is potting with an organic resin, but the large difference 
in hardness between the stainless steel pipes and the potting material 
makes it difficult to process the end surfaces of the potting members. 
That is, the ends of the pipes have exposed sharp edges which, in the 
treatment of a fluid containing particles as blood cells, tend to destroy 
those particles. In order to overcome this difficulty, the use of 
stainless pipes whose tips are covered with soft pipes is under 
investigation, but no marked improvements have been produced. 
A heat exchanger is used as a means for the heat exchange of various 
fluids. For example, when a blood oxygenator is used to perform an 
operation on the heart, a heat exchanger is usually added to the blood 
gas-exchange circuit including the blood oxygenator because of the 
necessity to adjust the body temperature of the patient to a low level at 
the beginning of the operation, the necessity to make the temperature of 
the blood having undergone gas exchange by means of the blood oxygenator 
almost equal to the body temperature of the patient before returning it to 
the body of the patient, or the necessity to restore the lowered body 
temperature of the patient to the normal level after the operation. In 
medical facilities such as hospitals and the like, this blood gas-exchange 
circuit is generally assembled by connecting a blood oxygenator with a 
separate heat exchanger by means of, for example, circuit tubes. However, 
such an arrangement is disadvantageous in that assemblage of the blood 
gas-exchange circuit is troublesome to the user, there is a risk of 
erroneous assemblage of the circuit, and additional space for the circuit 
is required. Moreover, since the blood oxygenator and the heat exchanger 
involves two separate stagnation sites of the blood and necessitate 
circuit tubes to connect them, the priming blood volume required at the 
initial stage of operation of the circuit is unduly large and the various 
circuit components must be degassed separately. Thus, such an arrangement 
is also complicated from the viewpoint of operation. 
As means for overcoming these disadvantages, blood oxygenating device 
comprising a blood oxygenator combined with a heat exchanger to form an 
integral unit are disclosed, for example, in Japanese Patent Publication 
No. 2982/'80 and Japanese Patent Laid-Open No. 39854/'82. In these blood 
oxygenating devices, however, the heat transfer member of the heat 
exchange section is formed of a metal such as stainless steel having good 
thermal conductivity. In the case of stainless steel pipes, additional 
difficulties may be encountered because the metallic debris produced 
during processing of the pipe ends may remain in the pipes and contaminate 
the blood and, moreover, stainless steel may be reactive with some 
components of blood having a complicated composition. Accordingly, there 
is a continuing demand for a heat exchanger diminishing these 
difficulties. 
On the other hand, a number of blood oxygenators using a hollow-fiber 
membrane have already been proposed, for example, in U.S. Pat. Nos. 
2,972,349, 3,794,468, 4,239,729 and 4,374,802. 
In these blood oxygenators, hollow fibers made of a homogenous membrane of 
gas-permeable material such as silicone or hollow fibers made of a 
microporous membrane of hydrophobic polymeric material such as polyolefins 
are used to bring blood into contact with gas through the medium of the 
hollow-fiber membrane and effect gas exchange therebetween. There are two 
types of blood oxygenators: the inside perfusion type in which blood is 
passed through the bores of the hollow fibers while gas is passed on the 
outside of the hollow fibers and the outside perfusion type in which, 
conversely, gas is passed through the bores of the hollow fibers while 
blood is passed on the outside of the hollow fibers. 
In most of the conventionally known blood oxygenators, a cylindrical 
housing is simply packed with a large number of hollow fibers of 
semipermeable membrane for use in gas exchange in such a way that the 
hollow fibers are parallel to the axis of the cylindrical housing. 
However, blood oxygenators of this construction have low gas exchange rate 
per unit area of hollow-fiber membrane, whether they are of the inside 
perfusion type or of the outside perfusion type. As an improved form of 
the outside perfusion type, U.S. Pat. No. 3,794,468 has proposed a blood 
oxygenator in which hollow tubular conduits of semi-permeable membrane are 
wound about a hollow, cylindrical core having a large number of pores in 
the wall and then contained in a housing, and blood is allowed to flow out 
of the cavity of the core through its pores while gas is passed through 
the bores of the hollow tubular conduits. 
In blood oxygenators of the inside perfusion type in which gas exchange is 
effected by passing blood through the bores of the hollow fibers while 
passing gas on the outside of the hollow fibers, channeling of the blood 
occurs less frequently. However, since the blood flowing through the bores 
of the hollow fibers moves in a laminar flow, the internal diameter of the 
hollow fibers needs to be reduced in order to increase the oxygenation 
rate (i.e., the oxygen transfer rate per unit area of membrane). For this 
purpose, hollow tubes of semipermeable membrane having an internal 
diameter of the order of 150-300 .mu.m have been developed for use in 
blood oxygenators. 
Nevertheless, as long as the blood moves in a laminar flow, the oxygenation 
rate cannot be greatly increased by reducing the internal diameter. 
Moreover, as the internal diameter becomes smaller, clotting (i.e., 
blockage of the bore due to the coagulation of blood) may occur more 
frequently and/or the blood will be more subject to hemolysis due to an 
increased pressure loss through the oxygenator, thus posing serious 
problems from a practical point of view. Furthermore, since a blood 
oxygenator generally uses tens of thousands of hollow fibers of 
semipermeable membrane made into a bundle or bundles, special 
consideration must be given so as to distribute the gas uniformly to the 
external surfaces of each of these numerous hollow fibers. If the gas is 
not distributed uniformly, the carbon dioxide desorption rate (i.e., the 
carbon dioxide transfer rate per unit area of membrane) will be reduced. 
On the other hand, in blood oxygenators of the outside perfusion type in 
which gas is passed through the bores of the hollow fibers while blood is 
passed on the outside of the hollow fibers, the gas can be distributed 
uniformly and the blood can be expected to flow turbulently. However, 
these oxygenators have the disadvantage of being subject to insufficient 
oxygenation due to channeling of the blood and/or blood coagulation at the 
sites of stagnation. Although the blood oxygenator of the aforementioned 
U.S. Pat. No. 3,794,468 has undergone improvements in this respect, it is 
still disadvantageous in that the priming blood volume is unduly large, a 
considerable pressure loss through the oxygenator is caused, and a 
complicated procedure is required for the manufacture thereof. Thus, it 
remains desirable to develop a more improved blood oxygenator. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a heat exchanger having 
high heat exchange efficiency in which an organic polymer that has been 
thought to be unsuitable for use in the material of heat transfer walls 
because of its low thermal conductivity is used as the heat transfer 
member in the form of a hollow fiber. 
It is another object of the present invention to provide a heat exchanger 
in which the difference in hardness between the barrier member formed of 
an organic material and the heat transfer tubes is small enough to permit 
easy processing of the ends of the heat transfer tubes. 
It is still another object of the present invention to provide a heat 
exchanger which comprises heat transfer tubes having neither exposed sharp 
edges at the ends thereof, nor metallic debris remaining therein, and 
hence is especially suitable for the treatment of liquids containing 
fragile particles such as blood. 
It is a further object of the present invention to provide a blood 
oxygenating device which comprises a combination of a blood oxygenator 
using hollow fiber membranes as the gas exchange membrane and a heat 
exchanger using hollow fibers as the heat transfer tubes. 
It is still a further object of the present invention to provide a blood 
oxygenating device which is constructed by combining a blood oxygenator 
having high oxygenation and carbon dioxide desorption rates and causing 
little stagnation or channeling of the blood with a small-sized and 
lightweight heat exchanger having excellent heat exchange performance to 
form an integral unit, and hence characterized by having a compact, 
low-cost and simple construction, requiring no complicated procedures 
during manufacture, and being easy to use. 
According to one feature of the present invention, there is provided a heat 
exchanger comprising (1) a housing, (2) a bundle of hollow fibers made of 
an organic polymer, the bundle of hollow fibers being supported and packed 
within the housing so as to be fluid-tight at both ends thereof, (3) a 
heat exchange chamber formed on the outside of the hollow fibers, and (4) 
a fluid inlet chamber and a fluid outlet chamber provided at the 
respective ends of the bundle of hollow fibers in such a way as to 
communicate with the bores of the hollow fibers. 
According to another feature of the present invention, there is provided a 
blood oxygenating device furnished with a heat exchanger. This blood 
oxygenating device has a heat exchange section for controlling the 
temperature of blood and a gas exchange section for effecting the gas 
exchange of blood, and is characterized in that (1) the heat exchange 
section contains a bundle of hollow fibers made of an organic polymer as 
the heat transfer member, the bundle of hollow fibers being supported and 
packed in the heat exchange section so as to be fluid-tight at both ends 
thereof and (2) a fluid inlet chamber and a fluid outlet chamber are 
provided at the respective ends of the bundle of hollow fibers in such a 
way as to communicate with the bores of the hollow fibers. 
According to still another feature of the present invention, there is 
provided an improved blood oxygenating device constructed by using the 
internal structure of an improved blood oxygenator of the hollow-fiber 
membrane type as the gas exchange section of the aforesaid blood 
oxygenating device and containing this gas exchange section and the 
aforesaid heat exchange section within a single housing to form an 
integral unit. This blood oxygenating device comprises (1) a housing 
having a blood inlet, a blood outlet, a gas inlet, a gas outlet, a heat 
exchange medium inlet and a heat exchange medium outlet and defining 
therein a contact chamber, the contact chamber comprising blood flow 
channels narrowed by baffles and a plurality of compartments separated by 
the blood flow channels, (2) a first bundle or bundles of hollow fiber 
membranes consisting of a large number of hollow fiber membranes for use 
in gas exchange and having fixed ends, and (3) a second bundle or bundles 
of hollow fibers consisting of a large number of hollow fibers for use in 
heat exchange and having fixed ends, the first and second bundles of 
hollow fiber membranes being disposed in separate compartments so as to be 
substantially parallel to said baffles, the respective ends of the first 
bundle of hollow fiber membranes communicating with the gas inlet and the 
gas outlet and the respective ends of the second bundle of hollow fiber 
membranes communicating with the heat exchange medium inlet and the heat 
exchange medium outlet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The construction of a heat exchanger in accordance with the present 
invention will now be described with reference to FIG. 1. 
As shown in FIG. 1, this heat exchanger comprises hollow fibers 1 for use 
in heat exchange, a housing 2 for containing the hollow fibers, and a heat 
exchange chamber 3. A barrier member 4 serves to separate the heat 
exchange chamber 3, in a fluid-tight manner, from the open ends of the 
hollow fibers 1 and from a fluid inlet (or outlet) chamber 5 and a fluid 
outlet (or inlet) chamber 6 which both communicate with the cavities of 
the hollow fibers. The heat exchanger also has a fluid inlet 7 and a fluid 
outlet 8 which both communicate with the heat exchange chamber 3. 
Referring to FIGS. 2 and 3, there are shown other embodiments of the heat 
exchanger of the present invention. Unlike the heat exchanger of FIG. 1, 
these embodiments have a bundle of hollow fibers 1 disposed in straight 
lines within a housing 2. In the embodiment of FIG. 3, a fluid 
distribution chamber 9 and a fluid collection chamber 10 are provided 
between the fluid inlet 7 and the region occupied by the hollow fibers 1 
and between the fluid outlet 8 and the region occupied by the hollow 
fibers 1, respectively, in order that the fluid flowing on the outside of 
the hollow fibers 1 may follow flow paths substantially perpendicular to 
the hollow fibers 1. 
In making the heat exchanger of the present invention, the material of the 
hollow fibers constituting heat transfer tubes may be selected from a 
variety of organic polymers. Examples thereof include polyolefins and 
fluorinated polyolefins such as polypropylene, polyethylene, 
poly-4-methyl-1-pentene, polyvinylidene fluoride, and 
polytetrafluoroethylene; acrylonitrile polymers; cellulosic polymers; 
polyamides and polyimides; polyesters; silicone resins; polymethyl 
methacrylate and its analogs; polycarbonates; and polysulfones. Among 
others, organic polymers having a thermal conductivity of 
1.0.times.10.sup.-5 to 50.0.times.10.sup.-4 cal/cm.sec..degree.C. can be 
used to make a plastic heat exchanger which compares favorably in heat 
exchange efficiency with conventional heat exchangers using metallic 
pipes. 
Moreover, in order to enhance the heat transfer efficiency of the heat 
exchanger of the present invention, it is preferable to use hollow fibers 
having an internal diameter of about 50 to 1,000 .mu.m and a wall 
thickness of about 2 to 200 .mu.m. 
If the internal diameter of the hollow fibers used is excessively small, a 
large pressure loss may be caused during operation and the sealability of 
the fluid paths will be reduced. On the other hand, if the internal 
diameter of the hollow fibers is excessively large, the fluid flowing 
through the bores of the hollow fibers will have a small heat transfer 
coefficient and the relative volume occupied by the hollow fibers per unit 
heat transfer area will be increased, resulting in a reduction in heat 
transfer efficiency and resulting in enlargement in the size of the heat 
exchanger. Moreover, the wall thickness of the hollow fibers should 
desirably be as thin as possible, with a view to decreasing their heat 
transfer resistance and making it possible to form a heat exchanger of 
compact size. However, it is most preferable from the viewpoint of 
strength and handleability that the hollow fibers used in the present 
invention should have an internal diameter of 150 to 500 .mu.m and a wall 
thickness of 10 to 100 .mu.m. 
In the embodiment shown in FIG. 1, the heat exchanger of the present 
invention can be assembled by providing hollow fibers 1 made of an organic 
polymer as described above and disposing them in a housing 2. After a 
barrier member 4 is formed using a potting material selected from, for 
example, epoxy resins, unsaturated polyester resins, and polyurethane 
resins, the end surface of the barrier member 4 is processed in such a way 
that the hollow fibers have open ends. Finally, a fluid inlet chamber 5 
and a fluid outlet chamber 6 are provided. 
The heat exchanger of the present invention permits easy processing of the 
end surface of the barrier member because the difference in hardness 
between the barrier member and the hollow fibers is very small as compared 
with heat exchangers using metallic pipes as the heat transfer member. 
Thus, the open ends of the hollow fibers are so smooth that, even when 
this heat exchanger is used for the treatment of blood, the bood cells 
contained in the blood are by no means damaged by any edge formed at the 
ends of the hollow fibers. Moreover, the heat exchange efficiency of this 
heat exchanger can stand comparison with that of heat exchangers using 
metallic pipes. 
Now, the blood oxygenating device furnished with a heat exchanger in 
accordance with the present invention will be more fully described with 
reference to the accompanying drawings. 
The blood oxygenating device furnished with a heat exchanger in accordance 
with the present invention constitutes a heat exchange section A for 
performing the function of heat exchange with blood and a gas exchange 
section B for performing the function of gas exchange with blood. The heat 
exchange section A can be of the inside perfusion type in which blood is 
passed through the bores of the hollow fibers for use in heat exchange, or 
of the outside perfusion type in which blood is passed on the outside of 
the hollow fibers for use in heat exchange. The embodiment shown in FIG. 4 
is of the inside perfusion type, while that shown in FIG. 5 is of the 
outside perfusion type. 
The heat exchange section A of the inside perfusion type shown in FIG. 4 
comprises a housing 11, a blood inlet (or outlet) 12, a blood flow channel 
13, hollow fibers 15 for use in heat exchange, potting members 14 for 
fastening the hollow fibers 15 within the housing 11 and separating the 
flow space for heat exchange medium from the flow space for blood, a heat 
exchange medium inlet(or outlet)16 and a heat exchange medium outlet (or 
inlet) 17. Where blood is passed through the heat exchange section A and 
the gas exchange section B in this order, the blood fed to the blood inlet 
12 flows through the bores of the hollow fibers 15 for use in heat 
exchange and undergoes heat exchange with the heat exchange medium fed to 
the heat exchange medium inlet 16 and passed on the outside of the hollow 
fibers 15 for use in heat exchange. Then, the blood traverses the blood 
flow channel 13 and enters the gas exchange section B, where it undergoes 
gas exchange. Thus, the temperature-controlled oxygenated blood emerges 
from the blood outlet 18. 
In the blood oxygenating device of FIG. 4, the gas exchange section B is 
constructed so as to be of the inside perfusion type in which blood is 
passed through the bores of the hollow fiber membrane 19 for gas exchange. 
An oxygen-containing gas is introduced through the gas inlet 20 into the 
gas exchange section B, where it undergoes gas exchange with the blood 
flowing through the bores of the hollow fiber membrane 19 for use in gas 
exchange, through the medium of the hollow fiber membrane. The gas thus 
decreased in oxygen content and increased in carbon dioxide content is 
discharged from the gas outlet 21. 
In the blood oxygenating device of FIG. 4, blood may first be subjected to 
gas exchange and then to heat exchange. This can be accomplished by 
feeding the blood through the blood outlet 18 and withdrawing it from the 
blood inlet 12. 
In the blood oxygenating device of the outside perfusion type shown in FIG. 
5, the heat exchange section A differs from that of FIG. 4 only in that 
the blood does not flow through the bores of the hollow fibers 15 for use 
in heat exchange, but flows on the outside thereof. The heat exchange 
medium fed through the heat exchange medium inlet 16 (or 17) passes 
through the heat exchange medium flow passage 22 (or 23) formed between 
the housing 11' and the potting member 14', through the bores of the 
hollow fibers, and they through the other heat exchange medium flow 
passage 23 (or 22). Thereafter, the heat exchange medium is discharged 
from the heat exchange medium outlet 17 (or 16). 
In the heat exchange section A of the blood oxygenating device of the 
present invention, the hollow fibers for use in heat exchange and the 
potting members may be made of the same material as described above in 
connection with the heat exchanger of the present invention. Moreover, the 
heat exchange section A may be made in the same manner as described in 
connection with the heat exchanger. 
In the gas exchange section B of the blood oxygenating device of the 
present invention, any of various types of blood oxygenators such as 
conventionally known membrane type blood oxygenators and bubble type blood 
oxygenators may be installed. However, membrane type blood oxygenators 
and, in particular, those using a hollow-fiber membrane are preferred. 
Since the blood oxygenating device of the present invention has an 
integrally formed heat exchanger, no circuit tubes or similar 
communicating devices are needed to connect the blood oxygenator with the 
heat exchanger, assemblage and operation of the circuit are easy, and the 
priming blood volume required at the initial stage of operation is small. 
Furthermore, the blood oxygenating device of the present invention has 
further advantages in that processing of the heat transfer tubes is easy 
because metal tubes are not employed, the blood cells contained in the 
blood suffer almost no damage, and it is small-sized and lightweight. 
Now, the blood oxygenating device of the present invention will be more 
fully described in connection with the most preferred embodiment in which 
the gas exchange section constitutes the internal structure of an improved 
membrane type blood oxygenator and both the gas exchange section and the 
heat exchange section are contained within a single housing. 
FIG. 6 is a vertical sectional view of such a blood oxygenating device, and 
FIG. 7 is a partially cutaway plan view thereof. This blood oxygenating 
device has a blood inlet 31, a blood outlet 32, a gas inlet 33, a gas 
outlet 34, a heat exchange medium inlet 35 and a heat exchange medium 
outlet 36, and includes a gas exchange section B and a heat exchange 
section A contained within a housing 37 generally in the form of a box. 
The gas exchange section B comprises compartments each having disposed 
therein a bundle of hollow fibers 38 for use in gas exchange and performs 
the function of gas exchange with blood, and the heat exchange section A 
comprises a compartment (or heat exchange chamber) having disposed therein 
a bundle of hollow fibers 39 for use in heat exchange and performs the 
function of heat exchange with blood, both sections being directly 
connected without the aid of tubes or similar communicating devices. 
Basically, the gas exchange section B includes hollow fiber membranes 38 
for use in gas exchange and potting members (or barrier members) 40. These 
members cause the internal space of the gas exchange section B to be 
divided into a contact chamber 41 through which blood flows, a gas 
distribution passage 42 for feeding an oxygen-containing gas to the bores 
of the hollow fiber membranes 38, and a gas collection passage 43 for 
conducting the gas to the gas outlet 34. The contact chamber 41 includes a 
plurality of baffles 44 disposed transversely to the flow of the blood so 
as to narrow the blood flow path in a direction perpendicular to that of 
the hollow fiber membranes (hereinafter referred to as the direction of 
the thickness of the contact chamber), and these baffles cause the contact 
chamber 41 to be divided into a plurality of compartments 45 containing 
hollow fiber membranes 38. On the baffles 44, one or more struts 46 may be 
provided in such a way as to extend in the direction of the thickness of 
the contact chamber 41. 
The hollow fiber membranes 38 are disposed substantially in straight lines 
within the compartments 45 and fastened with two opposite potting members 
40 in such a way that their respective ends remain open to the gas 
distribution channel 42 and the gas collection channel 43. 
In the gas exchange section B of this blood oxygenating device, an 
oxygen-containing gas is fed to the gas distribution passage 42 through 
the gas inlet 33 and then passed through the bores of the hollow fiber 
membrane 38 disposed in the contact chamber 41, where it undergoes gas 
exchange with the blood through the medium of the hollow fiber membrane. 
The gas thus decreased in oxygen content and increased in carbon dioxide 
content is conducted to the gas collection passage 43 and then discharged 
from the gas outlet 34. Of course, the oxygen-containing gas fed through 
the gas inlet 33 may comprise pure oxygen. 
On the other hand, blood withdrawn from a human body (i.e., venous blood) 
is introduced into the blood flow uniforming chamber 47 through the blood 
inlet 31 and then passed through the contact chamber 41, where it 
undergoes gas exchange, through the medium of the hollow fiber membrane, 
with the oxygen-containing gas flowing through the bores of the hollow 
fibers 38. Thus, the venous blood is converted into arterial blood, which 
is fed to the heat exchange section A by way of the blood flow channel 48 
connecting the gas exchange section B with the heat exchange section A. 
In the embodiment shown in FIG. 6, the contact chamber is divided into 
three compartments 45 by two baffles 44. However, there may be present any 
desired number of compartments 45, provided the number of compartments 45 
is not less than 2. Although greater numbers are more preferable, it is 
practicably desirable in view of the ease of manufacture to divide the 
contact chamber into 2 to 6 compartments. 
The baffles 44 may have any of various cross-sectional shapes, provided 
that they can narrow the blood flow channel in the direction of the 
thickness of the contact chamber. However, baffles having a curved cross 
section as shown in FIG. 6 are preferably used in order to avoid 
stagnation the blood. The baffles 44 provided in the contact chamber 41 
serve not only to prevent channeling of the blood flow in the direction of 
the thickness, but also to make uniform the oxygen and carbon dioxide 
contents of the blood in cross sections perpendicular to the direction of 
the blood flow and thereby achieve good gas exchange. 
As shown in FIG. 6, the manner in which the blood flow channel is narrowed 
by the baffles 44 in the direction of the thickness of the contact chamber 
should preferably be such that adjacent baffles 44 are alternately 
positioned on the upper and lower walls. 
The dimensions of the contact chamber 41 in the blood oxygenating device of 
the present invention will now be described hereinbelow. It is preferable 
that the length (a) of each compartment 45 as measured in the direction of 
blood flow be larger than the maximum thickness (h) of the compartment. If 
the thickness (h) is larger than the length (a), the flow of blood in the 
direction of the thickness will be so dominant that stagnation of the 
blood will tend to occur at the corners of the compartment (i.e., in the 
vicinity of the boundaries between the compartment and the narrowed blood 
flow channels) and entrained air bubbles can hardly be removed when air 
bubbles are entrained. In order to obtain the effects of the baffles 44, 
the thickness (e) of the blood flow channels narrowed by the baffles 44 is 
preferably equal to or smaller than one-half the thickness (h) of the 
compartments. 
The width (l) of the contact chamber 41 (i.e., the distance between the two 
potting members 40) should be appropriately determined in relation to the 
flow rate of blood and the thickness (h) of the compartments. However, in 
order to produce a desirable sheet-like flow of blood in the contact 
chamber, it is preferable that the width (l) of the contact chamber be 
about 1 to 20 times as large as the thickness (h) of the contact chamber. 
If the width (l) is smaller than the thickness (h), the surfaces of the 
potting members will exert a significant effect on the blood flow and, 
occasionally result in poor workability. If the width (l) is larger than 
20 times the thickness (h), it will become difficult to some extent to 
distribute the blood uniformly over the surfaces of all hollow fibers and 
thereby prevent channeling of the blood. 
In the contact chamber, the hollow fibers are disposed almost 
perpendicularly to the direction of blood flow. The term "direction of 
blood flow" as used herein does not mean the direction of the blood flow 
actually produced by passing blood through the contact chamber, but the 
direction of the straight line connecting the blood inlet with the blood 
outlet. In order to prevent channeling of the blood, the hollow fibers 
need to form an angle of at least 45.degree. with the direction of blood 
flow, and it is most preferable that the hollow fibers be almost 
perpendicular to the direction of blood flow. The reason for this is 
believed to be that, when the blood flows across the hollow fibers, small 
turbulences of the blood flow are produced around the hollow fibers. 
Moreover, the large number of hollow fibers contained in each compartment 
are preferably disposed in such a way that each hollow fiber is parallel 
to the longitudinal axis of the bundle of hollow fibers. However, they may 
be disposed in such a way that a plurality of hollow fibers are bundled 
and they are wound at an angle of up to 45.degree. with the longitudinal 
axis of the bundle of hollow fibers. 
The degree of packing of the hollow fibers contained in each compartment 
preferably ranges from 10% to 55%. The term "degree of packing" as used 
herein means the proportion of the total cross-sectional area of the 
hollow fibers to the cross-sectional area of the compartment, as viewed in 
a plane perpendicular to the direction of blood flow in the contact 
chamber. If the degree of packing is less than 10%, channeling of the 
blood will tend to occur and turbulence of the blood flow can hardly be 
produced. If the degree of packing is greater than 55%, the flow 
resistance of the blood will become unduly high and hemolysis may be 
induced. Although the degree of packing of the hollow fibers may vary with 
the compartment, it is preferable for convenience of manufacture to employ 
an equal degree of packing for all compartments. 
The hollow fibers contained in the blood oxygenating device for use in gas 
exchange may comprise hollow fibers made of various homogeneous or porous 
membrane materials including, for example, cellulosics, polyolefins, 
polysulfones, polyvinyl alcohol, silicone resins and PMMA. However, hollow 
fibers made of a porous polyolefin membrane are preferred because of their 
excellent durability and gas permeability. Especially preferred are hollow 
fibers formed of a membrane which comprises fibrils stacked in layers 
between both surfaces and nodes fixing the respective ends of the fibrils 
and, therefore, has micropores composed of the spaces between the fibrils 
and interconnected so as to extend from one surface to the other. Examples 
of such hollow fibers include polypropylene hollow fibers and polyethylene 
hollow fibers, both commercially available from Mitsubishi Rayon Co., Ltd. 
under the trade name of KPF and EHF, respectively. 
Struts 46 which may be provided on the baffles 44 can perform the functions 
of producing turbulences of the blood flow in the contact chamber and 
preventing the hollow fibers contained in the compartments from being 
moved toward the baffles by the blood flow to give an unduly high degree 
of packing of the hollow fibers in these regions and thereby induce 
hemolysis or the like. Accordingly, it is a preferred embodiment of the 
present invention to provide such struts 46. 
The potting members 40 may be conveniently formed in the same manner as in 
the manufacture of so-called hollow-fiber filtration modules using hollow 
fibers. Specifically, this can be accomplished by selecting a potting 
material having good adhesion properties from polyurethane, unsaturated 
polyesters, epoxy resins and the like, and molding it integrally with the 
hollow fibers. 
On the other hand, the heat exchange section A has provided therein a heat 
exchange medium inlet 35, a heat exchange medium distribution passage 49, 
a bundle of hollow fibers 39 for use in heat exchange, a heat exchange 
medium collection passage 50 and a heat exchange medium outlet 36. The 
bundle of hollow fibers 39 for use in heat exchange, which allows a heat 
exchange medium such as warm water to flow through the bores thereof, is 
disposed almost perpendicularly to the direction of the blood flowing from 
the blood flow channel 48 to the blood outlet 32. When the hollow fibers 
39 are disposed in this manner, the heat transfer resistance of the 
laminar film of blood can be reduced and the heat exchange efficiency 
between the blood and the heat exchange medium can be enhanced, thus 
making it possible to form a heat exchange section A of compact size. 
In the embodiment shown in FIGS. 6 and 7, the heat exchange chamber 51 
containing the bundle of hollow fibers 39 for use in heat exchange 
comprises only one compartment. However, similar to the gas exchange 
section B, the heat exchange chamber may be divided into a plurality of 
compartments. Moreover, although this embodiment is constructed so that 
the blood passes through the gas exchange section B and the heat exchange 
section A in this order, it is also possible to subject the blood to heat 
exchange in the heat exchange section B and then to gas exchange in the 
gas exchange section B. Furthermore, the bundles of hollow fibers for use 
in heat exchange and ones for use in gas exchange may be disposed in any 
desired compartments of the contact chamber of the blood oxygenating 
device of the present invention in order to subject the blood to gas 
exchange and heat exchange in any desired order. 
This improved type of blood oxygenating device furnished with a heat 
exchanger not only has the previously described advantages of the 
exchanger of the present invention, but also can exhibit the additional 
beneficial effect of achieving high oxygenation and carbon dioxide 
desorption rates per unit area of the hollow fiber membrane (even if the 
blood is passed with a low pressure loss) because little stagnation or 
channeling of the blood is caused and turbulence of the blood flow is 
produced easily. 
The present invention is further illustrated by the following examples. 
EXAMPLE 1 
A water-water heat exchange test was carried out using a heat exchanger of 
the construction shown in FIG. 2. The hollow fibers used in this heat 
exchanger were made of high-density polyethylene and had an internal 
diameter of 360 .mu.m and a wall thickness of 20 .mu.m. The effective heat 
transfer length (f) of the hollow fibers was 10 cm, their effective heat 
transfer area was 0.1 m.sup.2, and their degree of packing (i.e., the 
proportion of the total cross-sectional area of the hollow fibers to that 
of the housing as viewed in the cross section taken along the line X--X' 
of FIG. 2) was 17%. 
Specifically, water having a temperature of 30.degree. C. was fed through 
the fluid inlet at each flux shown in Table 1, while warm water having a 
temperature of 40.degree. C. was passed through the heat exchange chamber. 
Thus, the temperature of the water emerging from the fluid outlet was 
examined. 
TABLE 1 
______________________________________ 
Flux of water fluid temperature 
(liters/min) at fluid outlet 
______________________________________ 
1.0 37.2.degree. C. 
2.0 36.4.degree. C. 
______________________________________ 
It is to be understood that the water temperature at the fluid outlet can 
be adjusted to any desired value by appropriately determining the inlet 
temperature and flow rate of the water being passed through the heat 
exchange chamber. 
EXAMPLE 2 
A blood oxygenator of the construction shown in FIGS. 6 and 7 was 
assembled. The gas exchange section B comprised three compartments having 
a thickness (h) of 4.0 cm, a length (a) of 4.0 cm and a width (l) of 13 
cm, which compartments were separated by two blood flow channels narrowed 
by baffles and having a thickness (e) of 1 cm and a length of 0.5 cm. In 
each of these compartments, hollow fibers for use in gas exchange were 
packed so as to give a degree of packing of 25%. The hollow fibers used 
were hollow fibers made of a porous polypropylene membrane (commercially 
available from Mitsubishi Rayon Co., Ltd. under the trade name of KPF) and 
characterized by a wall thickness of 22 .mu.m, an internal diameter of 200 
.mu.m and a bubble point of 12.5 kg/cm.sup.2. The total surface area of 
the membrane as calculated on the basis of the internal diameter was 2.0 
m.sup.2. The heat exchange section A comprised a heat exchange chamber 
having a thickness (h' ) of 4.0 cm, a length (b) of 3.0 cm and a width (l) 
of 13 cm, in which the same hollow fibers as used in Example 1 (were 
packed so as to give a degree of packing of 25% with a heat transfer area 
of 0.25 m.sup.2 as calculated on the basis of the internal diameter). The 
gas exchange section B and the heat exchange section A were connected by a 
blood flow channel having a thickness of 1 cm and a length of 1 cm. 
Using this blood oxygenator, a heat exchange test was carried out on bovine 
blood which had previously been adjusted to 30.degree. C. The bovine blood 
had a hematocrit of 35%, a pH of 7.32, an oxygen partial pressure of 65 
mmHg, a carbon dioxide partial pressure of 45 mmHg and a hemoglobin 
concentration of 12.5 g/dl. 
Specifically, the bovine blood was fed through the blood inlet 31 at 
various flow rates, while pure oxygen having a temperature of 30.degree. 
C. was fed through the gas inlet 33 at flow rate of 10 liter/min. 
Separately, warm water having a temperature of 36.degree., 38.degree. and 
40.degree. C. was fed through the heat exchange medium inlet 35 at each of 
the flow rates of 5, 7 and 9 liter/min. Thus, the temperature of the blood 
emerging from the blood outlet 32 was measured. 
The results obtained with warm water having a temperature of 40.degree. C. 
are shown in FIG. 8. When the warm water had a temperature at 36.degree. 
C. or 38.degree. C., the results obtained were substantially the same as 
shown in FIG. 8. As can be seen from these results, the temperature of the 
blood emerging from the blood outlet can be adjusted to any desired value 
by varying the temperature and flow rate of the heat exchange medium. In 
FIG. 8, the coefficient of heat exchange is defined by the following 
equation: 
##EQU1## 
In addition, the same procedure was repeated except that the bovine blood 
and oxygen were adjusted to 37.degree. C. and the blood flow rate per unit 
area of membrane (Q/S) was varied from 0 to 3 liters/m.sup.2.min. Thus, 
the oxygen partial pressure of the blood emerging from the blood outlet 
was measured to determine the oxygenation rate (in ml/min.m.sup.2) of this 
blood oxygenator. 
The results thus obtained are shown in FIG. 9.