Note: Descriptions are shown in the official language in which they were submitted.
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--CIPl 1 BLOOD OXYGENATOR ~ITH INTEGRAL
2 HEAT EXCHANGER
Abstract of the Disclosure
A blood oxygenàtor includes a heat exchanger wherein heat
transfer fluid flows through a tube which is ribbed along its
6 length. The tube is positioned within a chamber connectea in
7 an extracorporeal blood circuit such that the blood is caused
8 to flow over the exterior surface of the ribbed tube. In
9 the preferred embodiment, the blood flows through a plurali~y
of continuous, restricted area ~low paths o fering substant~ally
11 uniform flow impedance to the blood, these restricted flow
12 paths being provided by constructing the tube with an integral~
13 substantially continuous, hollow, helical rib, and by forming
14 the helically ribbed tube in a helical configuration mounted
between an inner cylindrical column and an outer cylindrical
16 shell such that the blood is caused to flow through the plural
17 paths of restricted cross-sectional area provided by the
18 helical flute. In one embodiment, the heat exchanger tube
19 and blood chamber are formed as an independent unit adapted
for use in the desired location of an extracorporeal blood
21 circuit~ In the other embodiments, the heat exchanger is
22 formed integral with a blood oxygenator in which oxygen is
23 absorbed into the blood and carbon dioxide is released
2~ therefrom. In the p~eferred embodiment, the heat exchanger
also perorms substantially all of the transfer of oxygen into
2~ the blood and the removal of carbon dioxide from the blood~
27
28
29
3 sackground of the Invention
3Extracorporeal circulation is and has been a routine
3 procedure in the operating room for several years. An important
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1 component in the ex-tracorporeaL blood circuit is a heat exchanger
2 used to lower the temperature of the blood prior to and during
3 a surgical procedure and subsequently rewarm the blood to normal
4 body temperature. The cooled blood induces a hypothermia which
substantially reduces the oxygen consumption of the patient. The
6 published literature indicates that the oxygen demand of the
7 patient is decreased to about one-half at 30C, one-third at
8 25C and one-fifth at 20C. Light ~33 to 35C), moderate
9 (26 to 32C), and deep (20C and below) hypothermia are commonly
used in clinical practice. Hyp~thermia is used to protect the
11 vital organs including the kidneys, heart, brain and liver during
12 o~erative procedures which require interrupting or decreasing
13 the perfusion.
14 A number of different structural configurations for heat
exchangers have been used in the extracorporeal blood circuit
1 16 including hollow metal coils, cylinders and plates through which
17 a heat transfer fluid (typically water) is circulated. A survey
18 of a number of different t~pesof heat exchan~ers used in
19 extracorporeal circulation is included in the book entitled
"Heart-~ung Bypass" by Picrr~ M. Gall~tti, M.D. et al, pages
21 165 to 170.
22 Notwithstanding the pLurality oE diEferent types of heat
23 exchanger conigurations which have been usecl in the past, there
2~ remains a need for a safe highly efficient heat exchanger desiyn
which is simple to use and yet inexpensive enoug'n to be
26 manufactured as a disposable item. Thus, it is important that
27 there not be any leakage of the heat transfer fluid into the
28 blood. ~his fluid is typically circulating water flowing from
29 plumbing fixtures located in the operating room. Certain of the !
heat exchangers co~nonly used today for clinical bypass operations
31 have an upper pressure limit which is sometimes lower than the
32
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1 water pressures obtainable in -the hospital operating room. The
2 person who connects up the heat exc:hanger must therefore be
3 very careful to never apply the full force of the water pressure
4 through such a heat exchanger. Failing to take this precaution,
~ or an unexpec~ed increase in water pressure, could cause a
6 rupture within the heat exchanger resulting in contamination
7 of the blood flowing through the blood oxygenator.
8 Xt is also important that the heat exchanger have a high
9 performance factor in order to ~educe to a minimum the time
required to lower the temperature to induce hypothermia and
11 subsequently raise the blood temperature to normal. Some
12 physiological degradation oE the blood occ~rs after a patient
13 is connected only a few hours to any of the bubble oxygenators
14 presently in use. Therefore, time saved in cooling and
rewarming the blood is of direct benefit to the patient and
16 also giv~s the surgeon additional time to conduc-t the surgical
17 procedure if necessary.
18 Summary _f the Invention
19 The pre~ent invent;on relates to ~I hea-t exchanger for an
extracorporeal blood circuit formecl by a mctal tube having
21 int~ralr hollow ribbin~ along its lcngth. l'his tube in turn
22 i5 formed in an over~ll helical configuration and mounted
23 between an inner cylindrical column extending within the
24 helically configured tube and an outer cylindrical shell.
Both the column and the shell are sized such that peripheral
26 portions of the ribbing are in contact with or are closely
27 proximate to the exterior wall of the column and the interior
28 wall of the cylindrical shell. ~he method employed for regulating
29 the temperature of blood using this type of heat exchange
element involves flowing a heat transfer fluid through -the tube
31 and hollow rib and flowing the blood in a counterflow direction
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1 over -the exterior surEace of the ribbed tube. The co~bination
2 of the rib and the contactiny surfaces of the cylinder and
3 chamber confine the flow of blood substantially within pa-ths o~
4 restricted area and extended length provided by the ribbing.
~ The heat exchanger of the present invention enjoys several
6 significant advantages. Thus, its performance factor is very
7 high due to the long residence time of the blood, the high
8 conductivity o the heat exchange tube, the counterflow operation,
9 and high flow rate of the heat transfer fluid through the ribbed
tube.
11 Heat exchangers cons-tructed in accordance with the present
12 invention have the reliability necessary for routine use in open
13 heart surgery and other procedures utilizing extracorporeal
14 circulation. The metal heat transfer fluid tube is an integral
lS member which may be completely tested, both before and after
16 assembly into the blood chamber, for leaks under substantially
17 hi~hèr fluid pressures than are ever encountcred in an operating
18 room environment. The intcyral naturo o the h~at exchange
19 tube also pxovides an important advantage in that only the
ends oE the ~ube pass through the wall o~ the blood carrying
21 chamber, thus minimizing the number of openinys in the chamber
¦ 22 which must be hermetically sealed. ~oreover, no connections
23 need to be made to the tube within the blood chamber since a
24 heat transfer fluid inlet and heat transfer fluid outlet are
provided by the ends of the tube extending out from the chamber.
26 Any leak at the connection of the heat exchanger tube and the
27 fluid supply conduit will merely leak water or other heat
28 transfer fluid external of the blood chamber.
29 The ribbed heat exchanger tube may be mounted within a
blood chamber separate from the blood oxygenator or may be
31 incorporated integral with the blood oxygenator, e.g., in the
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1 venous side within the blood-oxygen mixing chamber or in the
2 outlet side within the defoaminy chamber. In the embodiments
3 described below in which the heat exchanger is incorporated
4 within the mixing chamber of a bubble oxygenator the flow o
~ the blood and blood foam through the lengthy paths of restricted
6 ¦ cross-sectional area Gontributes to the blood-gas transfer
7 ¦ process, and, in one embodiment, this flow of blood and blood foam
8 ¦ effects substantially all of the blood-gas transfer process.
9 ¦ The heat exchangers of thi~ invention are sufficiently
10 ¦ economical in terms of material and manufacturing costs so
11 ¦ that it is disposed of a~ter use, thus avoiding the problems
12 ¦ and cost o sterilization in the hospital. In addition, the
~3 ¦ heat exchangers construc-ted in accordance with this invention
14 ¦ may be made biologically inactive and compatible with human
15 ¦ blood.
16 ¦ Brief Description of the Drawings
17 ¦ Figure 1 is a vertical clevational partial sectional view
18 ¦ of a blood oxygenator having an integral heat exchanger
19 constructed in accordance with the present invention;
Figure 2 is a partially sectional view taken along the
21 line 2-2 of Figure l;
22 Figure 3 is a vertical elevational partial sectional view
23 of another embodiment of a blood oxygenator having an integral
24 heat exchanger constructed in accordance with the present
invention;
26 Figure 4 is a partially sectional view taken along the
27 line 4-4 of Figure 3;
28 Figure 5 is a v~rtical elevational partially sectional
29 view of a heat exchanger constructed in accordance with the
present invention for use as a separate component in an
33l extracorporeal blood circuit;
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1 Figure 6 is a partially sect;onal view taken along the
2 line 6-6 of Figure 5;
3 Figure 7 is a perspective view o~ the port member providing
4 a fluid conduit, a ridged connector and rods for positioning the
centrally located column shown in Figure 5;
6 Figure 8 is a vertical elevational partial sectional view
7 of another embodiment of a blood oxygenator having an integral
8 heat exchanger constructed in accordance with the present
9 invention;
Figure 9a is a par-tially sectional view taken along the
11 line 9-9 of Figure 8 showing the heat exchanger tube ends in
12 parallel alignment;
13 Figure 9b is a partially sectional view ta~en along the
14 line 9-9 of Figure 8 showing the heat exchanger tube ends in
a non-parallel alignment;
16 ~igure 10 .is a vertical elevational sectional view along
17 the line 10-10 of ~'icJure 11 o the prcferred embodiment o~ a
18 blood oxyg~nator h~vlng an i.nternal. heat ~xchanger constructed
19 .in accordanc~ with thc prescnt invention;
Figure 11 is a front ~Levational view of -the preferred
21 embodiment o the prosent .inve~ntion;
22 FicJure 12 is a fraclmentary rear elevational view of the
23 defoamer section of the prcferred ~mbodiment of a blood
2~ oxycJenator having an integral heat exchanger constructed in
accordance with the present invention;
26 Figure 13 is a hori~ontal partially sectional view taken
27 along line 13-13 o~ Figure 10;
28 Figure 14 is a bottom plan view taken along line 14-14 of
29 Figure 10, of the preferred embodiment of a blood oxygenator
having an integral heat exchanger constructed in accordance
~1 with the present inven~ion, and
32
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1 Figure 15 i5 a vertical elevational partial sectional view
2 of the oxygenating cham~er of the preferred embodiment incorporati
3 a modified form of the heat transfer fluid tube.
4 Detailed Description of the Embodiment of Figures 1 and 2
~ Referring to Figures 1 and 2, a blood oxygenator 10 is shown
6 incorporating a heat exchanger in accordance with this invention~
7 In this first embodiment as well as the other embodiments
8 described below and illustrated in Figures 3, 4, 8, 9a and 9b, ;
9 the blood oxygenator 10 is shown constructed in accordance with
the invention disclosed and claimed in Canadian Patent ~o.
11 1,072,849 issued March 14, 1980 to Robert M. Curtis, entitled
12 BLOOD OXYGENATOR and assigned to Shiley Laboratories, Inc., the
13 assignee of the present invention. The bubble oxygenator chamber
1~ 11 is formed by a cylindrical shell 12 having its lower end
closed off by a multi-port end cap 13. In the outer wall of
16 the end cap 13 are formed one or more blood inlet ports, one such
17 port 14 being connected to the extracorporeal blood circuit by
18 a flexible venous blood conduit lS. In the center of the cap 13
19 and extending through the wall thereof is an oxygen inlet port 20
including an outwardly extending ridged connector 21 for
21 attachment to a flexible oxygen line 22. ~he oxygen entering the
22 inlet port 20 is caused to form a plurality of oxygen bubbles
23 by means of a sparger 23. These bubbles flow through the venous
24 blood entering the annular trough 24 formed by the end cap 13
and the blood and oxygen mixture flow upwardly through a three-
26 dimensional, open cellular mixing material 25 supported above
27 the sparger 23 within the chamber 11 by a pair of annular
28 retaining rings 26 and 27. The mixing material 25 is formed as
29 a cylinder so as to completely fill the cross-sectional space
within the cylindrical shell 12 ~etween the annular retaining
3 rings 26 and 27.
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1 A column 30 is coaxially mounted within the upright
2 cylindrical shell 12 and supported by a horizontal rod 29 formed
3 as an integral cross brace of the annular retaining ring 27.
4 Both ends of the column 30 are hermetically sealed by caps 31.
The top of the chamber 11 is open. The arterializea blood
6 in the form of liquid blood and blood foam rises through this
7 opening and i5 contained in a channel 33 formed by a generally
8 half cylindrical shell 35 secured to a flat cover plate 36. As
described in the Canadian Patent 1,072,849 of Robert M. Curtis,
supra, the channel 33 leads to ~ defoamer chamb~r 37 wherein
11 the foam is collapsed and the arterialized whole blood collected
12 and returned to the extracorporeal blood circuits.
13 The heat exchanger comprises a pair of helically ribbed,
14 heat transfer fluid tubes 39 and 41. As shown, the hollow ribs
43 on these tubes have a triple helix configuration and provide
16 a continuous series of helical flutes 45 These helically
17 ribbed tubes 39 and 41 are advantageously constructed from a thin
18 wall tube of metal. Methods and apparatus for manufacturing such
19 helically ribbed tubes are described in U.S. Patent ~os. RE24,783
and 3,015,355.
21 An aluminum tube so formed and subsequently externally
22 coated with a thin coating of polyurethane provides a relatively
23 inexpensive, reliable and highly efficient heat exchange element.
24 The polyurethane film coating enables compatibility with human
blood, this coating being advantageously applied electrolytically
26 as a powder and subsequently heated to provide a very
27 permanent coating over the exterior surface of the aluminum tube.
28 Stainless steel may also be used and has the advantage-of not
29 requiring any coating for blood compatibility but also has
certain inherent disadvantages. Thus, this metal is a
31 substantially poor conductor of heat and is appreciably more
32 expensive than aluminum~ ¦
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1 ~s shown in Figures 1 and 2, the helicall~ ribbed tubes 39
2 and 41 are formed in a helical configuration and mounted between
the cen-tral column 30 and the interior wall of the shell 12
such that peripheral portions o~ the ribs are closely proximate
to and advantageously in con-tact with the exterior surface o
6 the column 30 and the interior wall 51 of the bubble oxygen
7 chamber 11. One end of each of the respective tubes 39 and 41
8 passes through hermetically sealed openings 53 and 55 formed in
9 the bottom of the chamber 11 and the opposite ends of the tubes
i 10 extend through hermetically sea~ed openings 57 and 59 fo~med in
¦ 11 the cylindrical shell 35. Urethane glue provides an effective
12 sealant between the outer surface of the polyurethane coated
13 tube and the chamber 11 and shell 35 formed of polycarbonate
14 plastic.
1~ Shell 12 is advantageously extruded from polycarbonate
16 plastic and includes a longitudinal slit (not shown) such that
17 the shell may be opened up during manufacture to accept the
18 helically ribbed tubes 39 and ~ fter these tubes and the
19 inner column 30 are mounted in place, the slit edges of the
shell are bonded togethcr by ethylene d~chloride.
21 Flex.iblQ conduits 61 and 63 are clamped to the upper ends
22 oE tubes 39 and 41 for suppl~ing ~ heat transEer fluid, typically
23 water under pressure, at the desired tempera~ure. The lower
2~ ends of the ribbed tubes 39 and ~1 are connected through 1exible
conduits 65 and 67 to a drain. In this manner, the flow of heat
26 transEer fluid is opposite to that of the flow of the blood in
27 the oxy~enator chamber 11 to produce a counterflow-type heat
2 exchanger.
29 Since the embodiment of Figures 1 and 2 has many features
3 and advantages in common with the other embodiments described
3 below, such features and advantages are described in detail
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1 hereinafter. ~ primary di~tinguishin~ feature of -the embodiment
2 of F:igures 1 and 2 is the use of dual heat exchanger tubes 39
3 and 41. The heat transfer performance of a heat exchanger is
4 related to the flow rate of the heat transfer fluid. Although
the single tube heat exchanger sho~m in the embodiments described
he~einafter has been found to have a most satisfactory performance
7 in all operating room environments tested to date, the double
8 tube embodiment of Figures 1 and 2 would be particularly useful if
9 only very low flow rates oE heat transfer fluid were available
during the extracorporeal procedure.
11 Detailed Description of the Embodiment of Figures 3 and 4 ' .
12 Another embodiment of a blooc oxygenator incorporating an
13 integral heat exchanger in accordance with this invention is
1~ sho~rn ln Figures 3 and 4. In this embodiment, the bubble
oxyyenating chamber 70 is formed by a pair oE mating plastic
16 shells 71 and 73, each including a flat peri~heral flange 75 and
17 77 which may be joined together to form a complete cylindrical
18 sheJ.l 80. Shell halves 71 and 73 are advantag~ously formed by
19 vacuuln ~orminy or in~e~ction moldincJ polycarbonate plastic.
Cylinclrical ~h~ll 80 :includc ~n upp~r s.ide opening 81 and
2~ a lower s.idc-~ opening 83 each havin~ an inteyral outwardly
22 extending cylindrical boss 85 through which extcnd the respective
23 en~s o~ a si.ngle helically ribbed heat transfer fluid tube 87.
24 The inside wal]. oE these eY~tendi.ng cylindrical bosses 85 and the.
proximate exterior surface of the heat exchanger tube 87 are
26 bonded together to effect a hermetic seal. Ethylene dichloride
27 forms an excellent bond between shell halves formed of polycarbon t
28 plastic~
29 ~ particular advantage of the construction shown in Figures
3 and 4 is that the heating coil 87 may be easily assembled
31 within the chamber 70. When the ribbed tube 87 is formed into a
32
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1 ¦ helical configuration, i-t has a tendency to open up, thereby
2 resulting in a certain amount of sliding frictional contact
3 with the inside walls of the chamber 70 and the exterior walls
4 of the column 90 when mounted in a unitary cylindrical shell
such as shown in Figures 1 and 2 at 12. In the embodiment of
6 Figures 3 and 4, the interior column 90 is inserted within the
7 helically formed ribbed tube 87 and both members placed in the
8 shell half 73 such that the two ends of heat exchange tube 87
9 extend through the openings 81 and 83. The mating shell half
71 is placed over the heat excha~ger tube 87 and the mating
11 flanges 75 and 77 bonded together to provide a completely sealed
12 cylindrical shell unit 80. As in the previously described
13 embodiment, the peripheral portions of the ribs 91 of the tube
14 87 advantageously contact both the interior wall of chamber 70
and the exterior wall of the column 90.
16 A plastic rod 93 or other convenient means is affixed to .
17 the opposite portions of one or both of the shell halve~ 71 and
18 73 for supportîng the interior column 90 in a predetermined positi on
19 The mating shells 7l and 73 are necked in at their bottom
and top to :Eorm respective openings 95 and 97 having cylindric~l
21 flanges 99 an~ 101. E`lange 101 snugl~ mates with the outside
22 diameter of a cylindrical member 103 on the bottom and a
23 cylindrical member lOS on th~ top respectively. As shown, a
24 small annular groove 107 may be formed in each of the flanges 99
and 101 to acc~mmodate an additional amount of bonding material
26 for providing a hermetic seal between the blood chamber 80 and
27 the cylinders 103 and 105.
28 Three dimensional, open cellular mixing material 109 is
29 supported within cylinder 103 by a pair of annular rings 111
and 113 attached to the inner wall of cylinder 103. This mixing
31 material comple.ely fills the cross-sectional interior of the
32 chamber 115 along the length of the mixing material.
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1 An end cap 117 is secured to and closes off the bottom of
2 cylinder 103. ~his ca~ includes one or more blood inlet ports,
3 one such port 119 being connected to the extracorporeal blood
41 circuit by a flexible venous blood conduit 121. In the center
51 of the cap 117 and extending through the wall thereo~ is an
61 oxygen inlet port 123 attached to a flexible oxygen line 125.
71 The oxygen entering the inlet port 123 is caused to form a
81 plurality of oxygen bubbles by means of a sparger 127. These
9¦ bubbles flo~J through the venous blood entering the annular
10¦ trough 129 formed by khe end ca~ 117.
11 ¦ The upper cylinder 105 is secured within an opening 131
12 ¦ formed in a flat cover plate 133. The arterialized whole blood
13 ¦ rises through this opening and is contained in a channel formed
14 ¦ by the cylindrical shell 35 through which it is passed to a
15 ¦ defoamer chamber 37 as described in the Canadian Patent 1,072,849 o
16 ¦ Robert M. Curtis, supra.
17 ¦ Detailed Description of the Embodiment of Figures 5, 6 and 7
18 ¦ Although the invention has been described hereinabove as
19 ¦ integral with a blood oxygenator, the heat exchanger of this
20 ¦ invention may be incorporat~d in a separate unit to be used
21 ¦ elsewhe~e in extracorporeal blood circuits. Refexring now to
22 ¦ Figures 5, 6, and 7, the same type of helically ribbed heat
23 transfer fluid tube 135 is mounted in a spiral configuration
24 between an interior cylindrical column 137 and within a
cylindrical chamber 139. Advantageously, peripheral portions
26 of the ribs are in contact with the exterior of the centrally
27 located column 137 and the interior wall of the chamber 139.
28 As described above with reference to the embodiment of Figures
29 1 and Z, the cylinder 145 is advantageously slit along its
length for facilitating insertion of the heat transfer fluid
31 tube, after which the edges of the slit are bonded together.
32 Respective end caps 141 and 143 are secured at opposite
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1 ends of the cylinder 145, each with a side opening having an
2 integral outwarclly extending cylindrical bosses 147 and 149
3 through which passes one end of the heat exchanger tube 135. A
4 suitable hermetic seal is formed between that portion of the
S exterior wall 151 of the heat transfer fluid tube 135 and the
6 inside wall of bosses 147 and 149 to prevent any blood leakage.
7 Typically, a suitable adhesive such as urethane glue is used to
8 form a bond between the cylinder 145 and end caps 141 and 143
9 formed of polycarbonate plastic.
The end cap members 141 and`143 each have a central aperture
11 153 and 155 concentric with the spirally formed heat exchanger
12 tube 135. In each such aperture, there is mounted a port member
13 157 having a ridged connector portion 159 extending outwardly
14 from the heat exchanger, four support rods 161 extending
inwardly into the heat exchanger, and a through conduit 163
1 16 through which blood passes into and out of the heat exchanger.
17 As shown in Figure 5, the four rods 1~1 make contact with the
1~ peripheral end surfacc 167 oE the centrally located column 137
19 to retain its ends equidistant Erom the end caps 1~1 and 143.
In use, flcxible water conduits 169 and 171 are attached
21 as shown to the extending ends 173 of the ribbed heat transfer
22 fluid tube 135,conduit 171 being connected to a suitable source
~3 of heat transfer fluid under pressure~ A counterflow of blood
2~ is introduced into the heat exchanger through a flexible conduit
Z5 172 attached to the ridged connector 159. The cooled or heated
26 blood flows out of the heat exchanger through port member 157
27 into flexible conduit 174 attached to the ridged connector 159.
28 Detailed Description of the Embodiment of Figures 8, 9a and 9b
_ . . . .
29 Another embodiment of a blood oxygenator incorporating an
30 ¦ integral heat exchanger in accordance with this invention is
31 ¦ shown in Figures 8, 9a and 9b. In this embodiment, the bubble
32 l
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1 ¦ oxygenator chamber 175 is formed by a cylindrical shell 177
21 having its lower end closed off by an end cap 179 having a side
31 opening 181 having an integrally attached, outwardly extending
41 cylindrical boss 183 formed in its ou-ter wall and a necked-in
~¦ portion 185 at its bottom including a cylindrical flange 187
61 surrounding a central aperture 189. This cylindrical flange of
ql the end cap 179 is sized to mate with the external diameter of
81 ~ cylinder 191 and bonded thereto with a suitable material such
9¦ as ethylene dichloride. A three~-dimensional, open cellular
lO ¦ mixing material 193 is supporte~ within cylinder 191 by
11¦ annular rings195 on its underside and 197 on its upper suriace~
1 12 ¦ As shown, material 193 completely fills the cross-sectional
1 13 ¦ interior oE the cylinder 191 along the length of the mixing
14 ¦ material.
15 ¦ The bottom of cylinder 191 is closed off by a multi-port
16 ¦ end cap 199. In the outer wall o the end cap 199 are ormed
17 ¦ one or more blood inlet E~orts, one such port 201 being connected
18 ¦ to the extracorporeal blood circuit by a flexible venous blood
19 conduit 202. In th~ c~nter of th~ cap 199 and extending through
the wall thereoE is an oxygen inlet port 203. '~he oxygen
21 ~ntering the :inlet port 203 v:;a oxyg~n line 205 is caused to
22 o.rm a plurality of o~ycJen bubble~ by means of a sparger 207.
23 These bubbles 1OW through the venous blood entering the
2~ annular trough 209 formed by the end cap 199 and the blood and
oxygen mi~ture flow upwardly through the three-dimensional,
26 open cellular mixing material 193 supported above the sparger
27 207 within the cylinder 191.
28 An upright column 211 is coaxially mounted within the
29 upright cylindrical shell 177 by a horizontal rod 213 supported
in appropriate semicircular slots 215 formed in the top surface
3~ ¦ of the cylinder 191. Column 211 is advantageously formed by
32 ~
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a hollow cyclindrical member 217 whose ends are sealed by
circular discs 219, one of which is shown at the lower end.
The top of the cylindrical shell 177 is closed by a similar
end cap 180 having a side opening 182 having an integrally
attached, outwardly extending cyclindircal boss 184 and a
necked-in flanged portion of 186 surrounding a central aperture.
The inner wall of flange 186 engages the outer wall of a cylin-
drical member 221 which in turn is attached to a flat cover
plate 223. As in the previous embodiments of Figures 1, 2, 3,
and 4, a generally half cylindrical shell 35 is secured to the
top surface of the cover plate 223 for directing the liquid
blood and blood foam into a defoamer chamber 37.
The helically ribbed heat transfer fluid tube 225 is
formed into a helical configuration and mounted in the space
between the central colum 211 and the inner wall of the cylin-
drical chamber 177 such that peripheral portions of the ribs
227 of the tube 225 advantageously contact or are in very close
proximity to the exterior wall of the column 211 and the
interior wall of the chamber 177.
The configuration of Figure 8 is conveniently assembled by
inserting the helically ribbed tube 225 along with the centrally
located column 211 into the cylindrical shell 177. As described
above with reference to the embodiments of Figures 1, 2, 5, 6,
and 7, the shell 177 is advantageously slit along its length
for facilitating insertion of the heat transfer fluid tube
225, after which the edges of the slit are bonded together.
As shown, the respective heat exchanger tube ends will then ex-
tend above and below the shell 177. These ends are then
inserted into the respective openings 181 and 182 formed in the
upper and lower end caps 179 and 180.
A particular advantage of this construction is illustrated
in Figures 9a and 9b. It has been found that after the helically
5~34
formed tube 225 is inserted in the chamber 177, the tube 225,
even when manufactured in conformance with the particular set
of specifications, does not always ultimately provide an
identical helical configuration. In particular, as noted above,
there is a tendency on the part of the spirally formed tube 225
to uncoil such that it may be difficult to orient the tube ends
along the parallel axes as illustrated in Figure 9a. In the
embodiment shown, the upper and lower end caps 179 and 180 may
be oriented along non-parallel axes as shown in Figure 9b to
accommodate whatever orientation the particular heat exchanger
coil 225 assumes when inserted whithin the chamber 177.
Detailed Description of the Preferred Embodiment of
a Pediatric Blood Oxygenator of Figures 10 Through 15
The preferred embodiment of a blood oxygenator incorporating
an integral heat exchanger in accordance with this invention is
shown in Figures 10 through 15. In the embodiment illustrated,
a pediatric blood oxygenator comprises a bubble oxygenating
chamber 240 formed by a pair of mating plastic shells, front
shell 242 and rear shell 244, each including a flat peripheral
20 flange 246 and 248 which are joined together to form a complete
cylindrical shell 250. Shell halves 242 and 244 are advanta-
geously formed by vacuum forming polycarbonate plastic, and
may be advantageously bonded together with ethylene dichloride.
Rear shell half 244 includes a blood outlet opening 252
hav.ing an integral rearwardly extending, tapered neck 254,
which is generally elliptical in cross section. Front shell
half 242 includes an upper side opening 256 and a lower side
opening 258, each having an integral forwardly extending
cylindrical boss 260 throu~h which extend the respective ends
of a single helically ribbed heat transfer fluid tube 262.
The inside wall of these extending cylindrical bosses
260 and the proximate exterior surface of the heat exchanger
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1 ~ tube 262 are bonded together to effect a hermetic seal.
2 ¦ ~s with the embod,ment illustrated in Figures 3 and 4,
3 ¦ the preferred embodiment is advantageously assembled by
4 ¦ inserting an extruded cylindrical interior column 264 within the
5 ¦ helically formed ribbed tube 262. Both ends of the column
6 ¦ 264 are hermetically sealed by end caps 265. The column
7 ¦ 264 and the tube 262 are placed in the front shell half 242
8 ¦ such that the two ends of the heat exchange-tube 262 extend
9 ¦ through the openings 256 and 258; The mating shell hal 244
10 ¦ is placed over the heat exchànge~r tube 262 and the mating flanges
11 ¦ 246 and 248 are bonded together to provide a completely sealed, .
12 ¦ cylindrical shell unit 250. The peripheral portion of the
13 ¦ ribs 266 of the tube 262 are closely proximate to and
14 ¦ advantayeously in contact with both the interior wall of the
chamber 2~0 and the exterior wall of the column 264.
16 The mating shells 2~2 and 244 are necked in at the bottom
17 to form a passage 268 defin~d by a hollow cylindrical neck 270.
18 The neck 270 snugly mate~ with the exterior wall of a hollow~
19 injection~molded cylindrical membe~ 272. As shown, a small,
annular ~roove 27~ may be ~ormed in the neck 270 to accommodate
21 additional bonding mater.ial to provide a hermetic seal between
22 the cylindrical shell unit 250 and the member 272.
23 The cylindrical member 272 includes one or more blood
2~ inlet ports 276, one such port 276 being connected to the
extracorporeal blood circuit by a flexible venous blood
26 conduit (not shown).
27 An end cap 278 is secured to and closes of the bottom
28 of the cylindrical member 272. In the center of the cap 278
29 and extending from the bottom thereof is an oxygen inlet port
280 which is attached to a flexible oxygen line (not shown).
31 The oxygen entering the inlet port 280 is caused to form a
32
~ 5~ 3 ~ `
l plurality of oxygen bubbles by means of a sparger 282. These
2 bubbles flow through the venous blood en-tering the cylindrical
3 member 272. The sparger 282 fills the entire cross-section of
4 the cylindrical member 272, and rests on an annular support
283. The sparger 282 is sealed around its periphery to the
6 inner wall of the cylindrical member 272. Advantageously, the
7 sparger 282 will be selected to produce small sized oxygen
8 bubbles, e.g., of the order of .3 cm or smaller, for most
9 efficient oxygenation in this embodiment.
The venous blood and oxygen bubbles then rise into the
11 oxygenating chamber 240, where they contact the extericr of the
12 tuhe 262. The combination of the tube ribbing 266 and the
13 contacting surfaces of the cylinder 264 and the chamber 240 confin 3
l~ the flow of blood and oxygen bubbl~s substantially within paths o
restricted area and extcnded length provided by the ribbing, thus
16 providing a tortuous path for the blood and axygen bubbles which
17 eff~ct a medically adequate transfcr of oxyg~n into the blood and
18 removal of carbon dioxide from th~ blood, without additional
19 mixing me~ns in the oxyg~nakor fluid path, ~ith~r upstxeam or
downstream o the ribbed tubing.
21 The arterialized blood, in the form of blood and
22 blood fo~lmr then flows Ollt of thc oxygenating chamber through
23 the outlet opening 252 and the taperedr elliptical cross-section
2~ neck 254 into a defoamer chamber 284.
The neck 254 communicates with an opening 286 in a flat
26 vertical plate 288 forming a side ~ortion defoamer chamber top
27 cap 290, which may advantageously be formed by injection-molded
2 plastic polycarbonate. The opening 286 in turn communicates with
29 a fluid channel member 292r located within the top cap 290
I
1 ¦ which empcies.the arterialized blood into an annular defoamer
2 inlet chamber 294. ~ .
3 Sealingly fixed to the underside of the top cap 290 is
an extruded hollow cylindrical cascade column 296 which runs
through a central axial void 298 in a tubular defoamer 300. The
6 defoamer 300 is contained within a cylindrical injection-molded,
7 polycarbonate plastic defoamer shell 302 which is bonded
8 hermetically around its upper periphery to a downwardly extending
9 peripheral flange 304 depending from the top cap 290. The
bottom of the defoamer shell 302 is sealed by a vacuum-formed,
11 polycarbonate plastic bottom cap` 306, which includes an inner
12 upwardly concave portion forming an annular seat 308 for a
13 defoamer lower support member 309. At the inner periphery of
14 the annular seat 308, the bottom cap extends still further
upwardly to form a circular, centrally raised portion 310.
16 The support member 309 bends appropriately so as to contact the
17 inner surface of the raised portion 310, forming a circular
18 centrally.raised platform 311, the inner surface of which closes
19 the bottom portion of the axial void 298 and seals thè bottom
of the cascade column 296.
21 The defoamer 300 shown is essentially as described in
22 the previously mentioned Canadian Patent 1,072,849. The defoamer
23 300 consists of an annular tube of reticulated porous sponge
24 materlal, such as polyurethane foam, and ls enclosed in a filter
cloth 312 of nylon tricot or dacron mesh. The filter clot~ 312
26 is secured by nylon cable ties 314 to an annular upper flange
27 315 which extends upwardly from an annular defoamer upper
28 support member 316, which, in turn, is bonded to a downwardly
29 extending cylindrical boss 317 in the top cap 290; and a lower
~1 ~ c lindrical flange 318 extending downward
,~ -19-
from the defoamer lower uppvrt member 309. soth -the ~loth
2 312 and the defoamer 300 are advan-tageously trea-ted with a
3 ¦ suitable antifoam compound.
4 ¦ The arterialized blood and blood foam flow from the inlet
1 5 ¦ chamber 294 int~ the annular axial void 298 through an annular
¦ 6 ¦ inlet 320. The majority of liquid blood entering the void 298
7 ¦ is guided by the column 296 to fill up the bottom of the void
298~ This liquid blood flows through the defoamer 300, as
¦ ~enerally shown by arrows 322. The blood and blood foam er.ter
lO I at the upper end oE the defoamer 300 so that a substantial
11 ¦ portion of the interior wall surface of the defoamer 300 is
. 12 contacted by the blood foam. As a result, a subs-tantial portion
13 of the defoamer 300 is used to separate the blood foam from the
1 14 entrapped gas such that the foam collapses and fluid blood flows
1 15 into an annular reservoir 32~ between the defoamer 300 and the
16 interior wall of the dcfoamer chamber 28~ and settles at the
17 bottom of the ch~mber 28~ and in the bottom cap 306. The
18 entrapped gclsr pr.im~r.ily c~xy~n ~nd CO2, which the defoamer
19 separatcs ou~ pass ~u~ o:E the ch~mber 284 ~hrough a vent 326
located in the upper end of the chamber at the juncture of the
21 top cap 290 and the cylindrical shell 302. ~s a result, only
22 whole liquid blood collccts i.n the reservoir 324, after having
23 been cleansed oE any particulate matter, such as blood
24 fragments and microemboli, by the filter cloth 312. The
oxygenated, filtered whole blood then passes through one or
26 more outlet ports 328 located in the lower-most portion oE the
27 bottom cap 306 and is returned to the patient by a flexible
28 arterial conduit (not sho~n).
29 The defoamer chamber 284 advantageously includes externally
applied indicia 330 of the volume oE blood contained therein.
311 The oxygena-tor may also include one or more externally threaded
321
~ ~5~3~
1 venous blood sampling ports 332 proximate the venous bloo~
2 inlet 276, and one or more arterial blood sampling ports 334
3 in the lower portion of the defoamer chamber 284~ One or more
4 priming ports 336 may also be provided in the top cap 290. Each
of the ports 332, 334, and 336 is conveniently sealed by
6 screw caps 338.
7 Figure 15 shows a modification of the preferred embodLment
8 wherein the helically ribbed heat transfer fluid tube is .
9 replaced by a tube 340 having discrete spaced annular hollow
ribs 342 formed in the wall of ~he tube along its length.
11 As with the heli.cally ribbed tube 262 shown in Figures 10 ,hrough
12 14, the peripheral portions of the annular ribs 342 are closely
13 proximate to and advantageously in contact with both the interior
l* wall of the chamber 240 and the exterior wall of the column
264. These discrete spaced annular ribs provide a plurality
16 of discontinuous flute passages around the tube whichr when their
17 individual lengths are added, total a distance considerably
18 longer than the length of the ~luid conduit. The combination
19 of the ribs 342 and the contacting surfaces o the column 264
and the chamber 240 confine the flow of blood and oxygen bubbles
21 substanti~lly wit:hin extended length, restricted area paths and
22 prov.ide a thorough mixi.ng o the blood and o~ygen bubb~esl therebs
23 cffecting a medically adequato transfer of oxygen into the blood
2~ and CO2 from the blood w:ithout addi-tional mixing means. Except
for the configuration of the ribbing on the tuber the embodiment
26 illustrated in Fiyure 15 is in all other respects iden-tical to
27 that illustrated in Figures 10 through 14.
28 The helically-ribbed heat transfer fluid tube 262t shown
29 in Figures 10 through 14 r is advantageously formed of a continuou
length of aluminum tubing with the exterior coated with a
33l polyurethane coat.ng, as discussed above or, alternativelyr the
I(
~ ~s~3~a
..
1 the exterior surfaces are electrolytically oxidized, or anodizedr
2 to form a "hard anodized" coating, as disclosed and claimed in
3 applicant's copending Canadian application Serial No. 317,615,
4 filed December 8, 1978.
~ The annular-ribbed heat transfer fluid tube 340, shown in
6 Figure 15 r may likewise be formed of anodized or polyurethane
7 coated aluminum. Alternativelyr it may be formed of brass or
8 bronze tubing having a blood compatible coating.
9 The preferrèd embodiment of~ Figures 10 through lS is
suited for use in both adult and pediatric applications. It is
11 advantageous to construct the oxygenating chamber with as small
12 a volume as possible, consistent with the requirements for heat
13 and gas transfer so as to minimize the amount of blood contained
14 in the oxygenating chamber during use.
~y way of specific example, a pediatric oxygenator with an
16 integral heat exchanger constructed in accordance with the
17 preferred embodiment comprises an oxygenating chamber 240 ha~ing
18 an inside diameter of approximately two inches, and contains a
19 central cylindrical column 264 having an outside diameter of
approximately one inch. The heat exchanger tube 262 is formed
21 of h~lf-inch outside diameter aluminum tubing, which, when
22 twisted to form the helical ribbing, has an outside diameter of
23 .490 inches from ridge to ridge of the ribs and .340 inches from
24 groove to groove between the ribs. The wall thickness of the
tube 262 is approximately .014 inches. The tubing is anodized,
26 as hereinabove described, and the anodized coating adds
27 approximately .001 inches to the wall thic~ness and approximately
28 .002 inches to the respective outside diameter measurements.
29 When completely assembled, and incorporating the heat exchanger
tube 262 and the central column 264, the oxygenating chamber has
332 a capacity of approximately 100 milliliters. The adult sized
, -22-
~ 1145ti3 ~
¦ unit is larger in scale with a capacity of approximatèly 450
2 I milliliters.
3 ¦ In constructing the oxygenating chamber, it is necessary to
~¦ coil the tube 262 tightly so as to have the peripheral portions
51 of the ribbing come into contact with, or at least be closely
6 ¦ proximate to, the exterior surface of the central column 264.
7 ¦ The hollow ribbing on the tube enables the tube to be so coiled
8 ¦ without kinking. Any kinking would be quite deleterious since it
9 ¦ would result in obstructed fluid flow and also a weakened wall
10 ¦ structure, which would make the tube prone to leaks. This
ll ¦ ability to be tightly coiled displayed bY the ribbed tubing
12 ¦ makes possible an oxygenating chamber having the relatively small
13 ¦ capacity of lO0 milliliters, and such a capacity has been found
l~ ¦ to be particularly advantageous in pediatric applications.
15 ¦ Tes-ts conducted on both adult and pediatric units constructed
16 ¦ in accordance with this embodiment show a medically adequate
17 ¦ transfer of oxygen into ~he blood and removal of carbon dioxide
18 ¦ thereErom. In general, tests conducted on identical units with
19 and without the~ mixing material of the prior e~bodiments show that
to achicve a given lcvel of oxygenation compared to these previous
i 2~ described embodiments, a higher level of ox~gen flow rate is
22 required Eor a ~iven blood fLow rate. Ln addition these tests
23 ~how that the level of ox~genation increases with an inc~ease
of the blood flow rate, e.g., at a blood flow oE 6 liters per
minute , the-oxygen gas content of the arterialized blood output
26 from the embodiment oE Figures 10-14 with a l:l o~ygen to blood
27 ratio closely approaches the oxygen gas content achieved with the
28 prior embodiments, whereas at a blood flow rate of 2 liters per
29 minute, a ratio of greater than 1:1 is required to achieve oxygen
gas content levels which are comparable to those achieved with
31
32 l
~ -23-
lll5~i3/~ ~
1 the prior embodiments of Fic3~lres 1, 2, 3, 4, 8 and 9.
2 sy way of specific ~Y.ample, th2 gas transfer da-ta obtained
3 duriny a specific tes-t are listed in Table 1. This test was
4 conducted November 1, 1977, on a female Suffolk lamb weighing
~ 26 kg which underwen-t a six-hour, partial veno-arterial
6 cardiopulmonary bypass using the oxygenator o~ the preferred
7 embodiment. The data indicate efficient oxygenation with ~2
8 removal in an oxygenator having an integral heat exchanger
9 constructed in accordance with the present invention, and
lacking any additional mixing structure in the oxygenating
11 chamber. ~he oxygenator used in these tests used a heat
exchanger anodized aluminum as previously described.
22
27
29
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5 ~ OO
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21 s ~ ~ ~ o o co o
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24 F ,~ ; o
O ~o ~ ~ o o cO C5~
26 h ~ ~1 ~ ~1 ~ t~
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l O ~ O
31 ~ ~ Lrl n G ~ ~ ~ ~ ~ d' h
l h S~ ~ ~ ~1 u ~ ~ Ln O
32 l ~ 1 o ~ ) o t~ u-)
~ ~ ~-- r-- ~ ~9 Lr) n ~ G ~9 ~1
1~563'~
A number of factors contribute to the excellent heat trans-
fer efficiency of the present invention and ir.clude the following:
1. ihe combination of the flutes of the heat transfer
fluid tube and proximate inner and outer surface walls of the
blood chamber provides a plurality of continuous, restricted
area flow-paths offering substantially uniform flow impedance
to the blood and blood foam. As a result, the blood and blood foam have
a long residence time in the heat exchanger. Mbreover, this structure avoids
areas of stagnation which otherwise hinder heat transfer from the blood
and are also undesirable from a physiological standpoint. In
the tests conducted to date on the embodiments of Figures 3, 4,
8, 9, and 10 through 14, the blood and blood foam was observed
to be in constant circulation through these restricted flow paths
and having extensive contact with and long residence time with
the heat exchanger tube. Only minimal areas of stagnation
were evident.
2. The extensive hollow ribs of the heat transfer fluid
tube provide a substantial surface area for transferring heat
from the heat transfer fluid to the blood and blood foam. The
tubes used in the above-described embodiments typically have an
external surface area of the order of 200 to 300 square inches.
The surface area of the tubes ued in the pediatric units is
on the order of 100 square inches.
3. Although the direction of fluid flow through the heat
exchanger tube may be in either direction, the heat transfer
performance is optimized by operating as a counterflow exchanger,
i.e., in the manner described above wherein the blood and heat
transfer fluid flow in generally opposite directions.
4. The wall thickness of the ribbed tube may be relatively
thin, e.g., .014 to .016 inch, so as to further improve its heat
transfer properties. As disclosed and claimed in the copending
application Serial No. 317,615, supra, very high thermal
ccnductivity is achieved using an anodized aluminum tube. The
-26-
3'~
polyurethane coated aluminum tubes described herein also have a
high thermal conductivity, notwithstanding that the polyurethane
coating reduces the overall thermal conductivity of the aluminum
tube by some 15 percent.
5. The ribbed heat exchanger tube has a sufficiently
large average internal diameter, e.g., approximately 0.5 inch,
for providing a high rate of flow of the heat transfer fluid,
e.g., 21 liters/minute of water. The average inside diameter
of the tubes used in pediatric units is approximately 0.34 inch
and accommodates a proportionately lower flow rate.
Although the integral heat exchanger embodiments described
above have incorporated the heat exchanger within the oxygenation
chamber, it will be apparent to those knowledgeable in the art
that the significant features of the heat exchanger tube which
contribute to its high heat transfer efficiency will be
beneficial in other locations within the blood oxygenator.
Thus, by way of specific example, the ribbed heat transfer fluid
tube may be located within the defoamer column such that the
blood flowing within or through the defoamer member is caused
to circulate through the flutes of the heat exchanger tube.
The integral nature of the heat exchanger tube also pro-
vides an important advantage in providing an effective seal for
preventing any possible contamination of the blood by the heat
transfer fluid. Thus, in the present invention, the heat
exchanger tube is advantageously constructed as a continuous
member with no connections being made to the tube within the
blood chamber. Any leak at the connection of the heat exchanger
tube and the flexible water or other heat transfer fluid conduit
-27-
11451j39L
I ~ill merely leak water or other fluid external of the blood
chamber.
In addition, the thickness of the heat exchanger tube,
4 af.ter being formed into a ribbed configuration, is ample to
~ handle fluid pressures considerably higher than those encountered
6 in clinical practice. This is important since typically the
7 heat exchanger tube is connected directly to a water faucet in
8 the operating room which, turned full on, may deliver water at a
9 pressure as high as 60 psi. Inadvertent closing of the drain
discharge can then build up pressure within the heat exchanger
11 to 60 psi. Such high pressures can rupture certain prior art
12 heat exchanger configurations concurrently in extensive use in
13 extracorporeal blood circuits. In contrast, in the present
14 invention, the ribbed tubes have been tested at substantially
high pressures, i.e., 120 psi without any indication of structural
16 damage or rupture.
17 In add.iti.on to its excellcnt heat transEer characteristics,
~ 18 the present .invent.ion is efficiently and economically manufactured .
I 19 Thus, the ribbed tube is an integral unit which may be completely
tested for leaks before and/or after assembly into the blood
21 carrying chamber. ~lso, .it has been found that pin hole or
22 other small leaks in the aluminum heat exchanger tube are sealed
2 by the polyurethane coating. Advantageously, the coa~iny covers
24 the entire tube includiny those portions extending through the
26 sealed openings of the blood chamber so as to provide this
2 additional protection against leakage.
27
31
L~/HJK:Pb32 -28-
