U.S. patent number RE37,379 [Application Number 09/534,926] was granted by the patent office on 2001-09-18 for high pressure gas exchanger.
This patent grant is currently assigned to Wayne State University. Invention is credited to James Richard Spears.
United States Patent |
RE37,379 |
Spears |
September 18, 2001 |
High pressure gas exchanger
Abstract
An apparatus 10 and method for delivering a high partial
pressure of a gas into a liquid. The apparatus has a gas transfer
device 12 with a housing 14 that includes upstream 16 and
downstream 18 regions, between which there is located a gas-liquid
contacting region 20 with contacting members 22, such as hollow
microporous fibers. A reservoir 36 of gas supplies the gas at a
high pressure (P) to a flask 38 of gas-depleted liquid and to the
gas transfer device 12. The reservoir 36 of gas provides
hydrostatic pressure for urging the liquid through the contacting
members 22 and propelling the gas around the contacting members 22
so that the gas does not diffuse across the contacting members 22.
The gas-enriched liquid is then ducted to a high resistance
delivery channel 44 for administration to a site of interest
without effervescence, bubble formation, or significant disruption
of laminar flow.
Inventors: |
Spears; James Richard
(Bloomfield Hills, MI) |
Assignee: |
Wayne State University
(Detroit, MI)
|
Family
ID: |
27558404 |
Appl.
No.: |
09/534,926 |
Filed: |
March 23, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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353137 |
Dec 9, 1994 |
5599296 |
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273652 |
Jul 12, 1994 |
5569180 |
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152589 |
Nov 15, 1993 |
5407426 |
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818045 |
Jan 8, 1992 |
5261875 |
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655078 |
Feb 14, 1991 |
5086620 |
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Reissue of: |
484284 |
Jun 7, 1995 |
05730935 |
Mar 24, 1998 |
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Current U.S.
Class: |
422/44; 261/101;
261/95; 422/45; 422/48; 604/24; 604/26; 604/4.01 |
Current CPC
Class: |
B01J
13/04 (20130101); C01B 5/00 (20130101); A61M
1/169 (20130101); C01B 13/00 (20130101); D21C
9/147 (20130101); A61M 1/32 (20130101); A61M
1/1698 (20130101); B01F 3/04439 (20130101); A61M
25/0026 (20130101); B01F 3/04985 (20130101); B01F
3/0876 (20130101); A61K 9/5089 (20130101); A61M
25/007 (20130101); C01B 13/02 (20130101); A23L
2/54 (20130101); B01F 2215/0052 (20130101); B01F
2215/0075 (20130101); A61M 1/1678 (20130101); A61M
25/09 (20130101); A61M 2025/0057 (20130101); B01F
2003/04893 (20130101); B01F 2003/04879 (20130101); A61M
2202/0476 (20130101); B01F 2215/0078 (20130101); B01F
2215/0034 (20130101); B01F 3/04099 (20130101); A61M
2202/0476 (20130101); A61M 2202/0007 (20130101) |
Current International
Class: |
A61K
9/50 (20060101); B01J 13/04 (20060101); A23L
2/52 (20060101); A23L 2/54 (20060101); C01B
5/00 (20060101); A61M 1/16 (20060101); C01B
13/00 (20060101); A61M 25/00 (20060101); C12M
1/04 (20060101); A61M 1/32 (20060101); C01B
13/02 (20060101); B01F 3/08 (20060101); B01F
3/04 (20060101); D21C 9/147 (20060101); A61M
001/14 (); A61M 001/34 (); A61M 037/00 () |
Field of
Search: |
;422/44,45,48
;604/4,24,26 ;261/DIG.28,95,101 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 343 845 |
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Mar 1974 |
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DE |
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2649126A1 |
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May 1978 |
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DE |
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2649126 |
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May 1978 |
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DE |
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Other References
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Edvard A. Hemmingsen, "Cavitation in gas-supersaturated
soluations," Journal of Applied Physics, vol. 46, No. 1, pp.
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microporous Teflon membrane oxygenator," Surgery, vol. 76, No. 6,
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W. Zingg et al., "Improving the Efficiency of a Tubular Membrane
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Robert H. Bartlett et al., "Instrumentation for cardiopulmonary
bypass--past, present, and future," Medical Instrumentation, vol.
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S. Marlow et al., "A pO.sub.2 Regulation System For Membrane
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270-275, 1981. .
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Membrane Oxygenator Using a Microporous Polysulfone Membrane,"
Trans Am Soc Artif Intern Organs, vol. XXVIII, pp. 338-341, 1982.
.
J. Mieszala et al., "Evaluation of a New Low Pressure Drop Membrane
Oxygenator," Trans Am Soc Artif Intern Organs, vol. XXVIII, pp.
342-349, 1982. .
S. Ohtake et al., "Experimental Evaluation of Pumpless
Arteriovenous ECMO With Polypropylene Hollow Fiber Membrane
Oxygenator for Partial Respiratory Support," Trans Am Soc Artif
Intern Organs, vol. XXIX, pp. 237-241, 1983. .
F.M. Servas et al., "High Efficiency Membrane Oxygenator," Trans Am
Soc Artif Intern Organs, vol. XXIX, pp. 231-236, 1983. .
Karl E. Karlson et al., "Initial Clinical Experience With a Low
Pressure Drop Membrane Oxygenator for Cardiopulmonary Bypass in
Adult Patients," The American Journal of Surgery, vol. 147, pp.
447-450, Apr. 1984. .
H. Matsuda et al., "Evaluation of a New Siliconized Polypropylene
Hollow Fiber Membrane Lung for ECMO," Trans Am Soc Artif Intern
Organs, vol. XXXI, pp. 599-603, 1985. .
T. Kawamura et al., "ECMO in pumpless RV to LA bypass," Trans Am
Soc Artif Intern Organs, vol. XXXI, pp. 616-621, 1985. .
J.B. Zwischenberger et al., "Total Respiratory Support With Single
Cannula Venovenous ECMO: Double Lumen Continuous Flow vs. Single
Lumen Tidal Flow," Trans Am Soc Artif Intern Organs, vol. XXXI, pp.
610-615, 1985. .
Yehuda Tamari et al., "The Effect of High Pressure on Microporous
Membrane Oxygenator Failure," Artificial Organs, vol. 15, No. 1,
pp. 15-22, Feb. 1991. .
JDS Gaylor et al., "Membrane oxygenators: influence of design on
performance," Perfusion, vol. 9, No. 3, pp. 173-180, 1994. .
Michael T. Snider et al., Small Intrapulmonary Artery Lung
Prototypes: Design, Construction, and In Vitro Water Testing, ASAIO
Journal, pp. M533-M539, 1994. .
Terry G. Campbell, Changing Criteria for the Articial Lung Historic
Controls on the Technology of ECMO,: ASAIO Journal, vol. 40, No. 2,
pp. 109-120, Apr.-Jun. 1994. .
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Pressure Loss, Implantable Artificial Lung," ASAIO Journal, vol.
40, No. 3, pp. M522-M526, Jul.-Sep. 1994..
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Primary Examiner: Bhat; Nina
Attorney, Agent or Firm: Kivinski; Margaret A.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
08/353,137, filed on Dec. 9, 1994, now U.S. Pat. No. 5,599,296
which is a continuation-in-part of application Ser. No. 08/273,652,
filed Jul. 12, 1994, now U.S. Pat. No. 5,569,180 which is a
continuation-in-part of application Ser. No. 08/152,589, filed Nov.
15, 1993 now U.S. Pat. No. 5,407,426, which is a
continuation-in-part of application Ser. No. 07/818,045, filed Jan.
8, 1992 now U.S. Pat. No. 5,261,875, which is a continuation of
application Ser. No. 07/655,078, filed Feb. 14, 1991 now U.S. Pat.
No. 5,086,620. The disclosures in each of the above-referenced
cases are incorporated herein by reference.
Claims
I claim:
1. An apparatus for delivering a high partial pressure of a gas
into a liquid, comprising:
a gas transfer device having
a housing including an upstream region, a downstream region, and a
gas-liquid contacting region with contacting members located
intermediate the upstream and downstream regions;
a liquid inlet port defined in the upstream region for receiving
gas-depleted liquid;
a liquid outlet port defined in the downstream region for
delivering gas-enriched liquid;
a gas inlet port defined in the housing for receiving the gas
before contact with the liquid in the contacting region;
a gas outlet port defined in the housing for returning gas which is
undissolved in the liquid;
a reservoir of gas for supplying the gas at a high pressure (P);
and
a flask of gas-depleted liquid in gaseous communication with the
reservoir, the flask being in liquid communication with the liquid
inlet port and in gaseous communication at a pressure (p), where p
is less than P, with the gas inlet port of the gas transfer
device;
whereby the reservoir of gas provides hydrostatic pressure for
urging the liquid through the contacting members and the gas around
the contacting members of the contacting region so that the gas
does not diffuse across the members thereof.
2. The apparatus of claim 1 further comprising:
a first regulator located between the reservoir of gas and the
flask of liquid.
3. The apparatus of claim 1 further comprising:
a second regulator situated between the flask of liquid and the gas
inlet port of the gas transfer device.
4. The apparatus of claim 1 further comprising:
a first regulator located between the reservoir of gas and the
flask of liquid; and
a second regulator located between the flask of liquid and the gas
transfer device.
5. The apparatus of claim 1 wherein the flask of gas-depleted
liquid includes:
a liquid conduit having an open end located below a meniscus of
liquid contained within the flask in order to promote delivery of a
relatively bubble-free liquid to the liquid inlet port of the gas
transfer device.
6. The apparatus of claim 1 further comprising:
a high resistance delivery channel in communication with the liquid
outlet port, the high resistance delivery channel serving to supply
a gas-enriched, bubble-free liquid to a desired site.
7. The apparatus of claim 1 wherein (P)-(p) is within a range of
about 5 p.s.i. to about 20 p.s.i.
8. The apparatus of claim 1 wherein the gas comprises oxygen and
the liquid comprises blood.
9. The apparatus of claim 1 wherein the gas comprises oxygen and
the liquid comprises water.
10. The apparatus of claim 1 wherein the gas comprises air and the
liquid comprises water.
11. The apparatus of claim 1 wherein the gas comprises air and the
liquid comprises gasoline.
12. The apparatus of claim 1 wherein the gas comprises carbon
dioxide and the liquid comprises water.
13. The apparatus of claim 1 wherein the gas comprises nitrogen and
the liquid comprises water.
14. A method for delivering a high partial pressure of a gas into a
liquid, comprising:
providing a gas transfer device having contacting members with a
gas-liquid contacting region;
supplying a gas under pressure to a flask of gas-depleted liquid
for expelling the liquid therefrom and to the gas transfer
device;
ducting the gas-depleted liquid to the gas transfer device; and
regulating a pressure differential within the contacting region
between the gas-depleted liquid and the gas whereby the liquid is
urged through the contacting members and the gas flows around the
contacting members so that the gas does not bubble across the
members. .Iadd.
15. An apparatus for producing a gas-enriched liquid,
comprising:
a gas transfer device comprising:
a housing having an upstream region, a downstream region, and a
gas-liquid contacting region with contacting members located
intermediate the upstream and downstream regions;
a liquid inlet port defined in the upstream region for receiving
liquid;
a liquid outlet port defined in the downstream region for
delivering gas-enriched liquid at a first pressure;
a gas inlet port defined in the housing for receiving the gas at a
second pressure wherein the first pressure is greater than the
second pressure; and
a gas outlet port defined in the housing for returning gas which is
undissolved in the liquid..Iaddend..Iadd.
16. The apparatus of claim 15, comprising a reservoir containing
the gas, the reservoir being operably coupled to the gas inlet
port..Iaddend..Iadd.
17. The apparatus of claim 16, comprising a flask containing the
liquid, the flask being operably coupled to the fluid inlet port
and to the reservoir containing the gas..Iaddend..Iadd.
18. The apparatus of claim 16 comprising:
a regulator located between a supply of the gas and the gas inlet
port..Iaddend..Iadd.
19. The apparatus of claim 17 comprising:
a first regulator located between the reservoir containing the gas
and the flask; and
a second regulator located between the flask and the gas inlet
port..Iaddend..Iadd.
20. The apparatus of claim 15 wherein a relatively bubble-free
liquid is supplied to the liquid inlet port of the gas transfer
device..Iaddend..Iadd.
21. The apparatus of claim 15 comprising:
a delivery channel in communication with the liquid outlet port,
the delivery channel serving to supply a gas-enriched, bubble-free
liquid to a desired site..Iaddend..Iadd.
22. The apparatus of claim 15 wherein the pressure differential
between the first pressure and the second pressure is within a
range of about 5 p.s.i. to about 20 p.s.i..Iaddend..Iadd.
23. The apparatus of claim 15 wherein the gas comprises oxygen and
the liquid comprises blood..Iaddend..Iadd.
24. The apparatus of claim 15 wherein the gas comprises oxygen and
the liquid comprises water..Iaddend..Iadd.
25. The apparatus of claim 15 wherein the gas comprises air and the
liquid comprises water..Iaddend..Iadd.
26. The apparatus of claim 15, wherein the gas comprises air and
the liquid comprises combustible fuel..Iaddend..Iadd.
27. The apparatus of claim 15, wherein the gas comprises carbon
dioxide and the liquid comprises water..Iaddend..Iadd.
28. The apparatus of claim 15 wherein the gas comprises nitrogen
and the liquid comprises water..Iaddend..Iadd.
29. The apparatus of claim 15 wherein the second pressure is
greater than atmospheric pressure..Iaddend..Iadd.
30. The apparatus of claim 22 wherein the second pressure is
greater than atmospheric pressure..Iaddend..Iadd.
31. A method for delivering a gas into a liquid, comprising:
providing a gas transfer device having contacting members with a
gas-liquid contacting region;
supplying a gas under pressure to the gas transfer device;
ducting a liquid to the gas transfer device; and
regulating a pressure differential within the contacting region
between the liquid and the gas so that the gas does not bubble
across the members..Iaddend..Iadd.
32. The method of claim 31 wherein the liquid within the contacting
region is at a first pressure which is greater than 760 mm Hg, and
wherein the gas within the contacting region is at a second
pressure which is less than the first pressure..Iaddend..Iadd.
33. The method of claim 32, wherein a pressure differential between
the first pressure and the second pressure is between about 5
p.s.i. and about 20 p.s.i..Iaddend..Iadd.
34. An apparatus for oxygenating blood comprising:
a membrane oxygenator adapted to provide oxygen-enriched blood at a
pO.sub.2 greater than 760 mm Hg..Iaddend..Iadd.
35. A method of oxygenating blood comprising:
providing a membrane oxygenator;
providing gas to the membrane oxygenator at a first pressure that
is greater than 760 mm Hg; and
passing blood through the membrane oxygenator to form
oxygen-enriched blood, wherein the pressure of the oxygen-enriched
blood proximate the exit of the membrane oxygenator is greater than
the first pressure, and wherein the blood remains within the
membrane oxygenator for sufficient time to form oxygen-enriched
blood with a pO.sub.2 greater than 760 mm Hg..Iaddend..Iadd.
36. The method of claim 35, wherein the pO.sub.2 of the
oxygen-enriched blood equals about the first
pressure..Iaddend..Iadd.
37. An apparatus for oxygenating blood comprising:
a membrane oxygenator adapted to provide oxygen-enriched blood at a
pO.sub.2 greater than 760 mm Hg, wherein the membrane oxygenator is
formed to operate as an equilibrium device..Iaddend..Iadd.
38. An apparatus for oxygenating blood comprising:
a membrane oxygenator adapted to provide oxygen-enriched blood at a
pO.sub.2 greater than 760 mm Hg and to operate as an equilibrium
device..Iaddend.
Description
TECHNICAL FIELD
This invention relates to an apparatus and method for generating a
relatively high partial pressure of a gas in liquid by the use of
an oxygenator.
BACKGROUND ART
In many industrial and clinical environments, it would be desirable
to deliver a gas-enriched fluid to a site of interest. For example,
in industrial applications it would be desirable to deliver carbon
dioxide rapidly via a liquid transfer medium to a fire in order to
extinguish the flame without the carbon dioxide becoming
prematurely liberated from its dissolved state in the transfer
medium. As another exampled the environmental problems of a toxic
site cleanup may be ameliorated if a neutralizing or cleansing
gaseous agent is delivered rapidly and at high concentration by a
transporting medium into the area which requires cleansing.
In clinical applications, as has been disclosed in my previous
patent applications referenced above, it would be highly desirable
to treat patients, for example stroke victims, by having ready
access to a system which would deliver an oxygen-enriched blood
stream rapidly to the anatomical area where the need for oxygen
enrichment is most acute.
For simplicity and brevity, the examples discussed below are
primarily selected from clinical environments, although the
applicability of the concepts and needs to be discussed to
non-clinical, including industrial, environments will be apparent
to those of skill in the art.
In the clinical area, if oxygen-supersaturated blood prematurely
liberates oxygen at the wrong place and at the wrong time, an
embolism may result. Its adverse consequences are well-known. For
example, the stroke victim may experience a sudden attack of
weakness affecting one side of the body as a consequence of an
interruption to the flow of blood to the brain. The primary problem
may be located in the heart or blood vessels. The effect on the
brain is secondary. Blood flow may be prevented by clotting
(thrombosis), a detached clot that lodges in an artery (embolus),
or by rupture of an artery wall (hemorrhage). In any event, a
severe interruption to the rate of mass transfer of oxygen-enriched
blood occurs if laminar flow becomes disturbed by bubble formation
and its consequent turbulent flow characteristics.
Ideally, the physician should be able to administer an
oxygen-enriched, supersaturated blood flow in a laminar fashion
quickly to a site of interest without premature liberation of
oxygen after it leaves a delivery apparatus, and undergoes a
pressure drop before arrival at the site requiring treatment.
What therefore is needed is a method and apparatus available to the
physician and industrialist which will enable them to deliver
gas-enriched fluids into environments of interest without premature
formation of bubbles in the transferring medium.
In the past, the main objections to the clinical use of hyperbaric
oxygen have been the risk of hemolysis and bubble emboli, together
with the complexity of the equipment. Dawids and Engell,
PHYSIOLOGICAL AND CLINICAL ASPECTS OF OXYGENATOR DESIGN,
"Proceedings On Advances In Oxygenator Design", June 1975, p. 140,
note that attempts to use oxygen at higher pressures call for the
blood to be pumped into the high pressure area where it is exposed
to the oxygen and then throttled down to normal pressure. These
workers note that such operations have caused considerable
hemolysis, which is more pronounced as the gas pressure increases.
Additionally, bubble formation may occur as a result of a rapid
pressure decrease and the high velocities in the throttling region.
Id.
SUMMARY OF THE INVENTION
Disclosed is an apparatus and method for delivering a high partial
pressure of a gas into a liquid. The apparatus includes a gas
transfer device with contacting members in a gas-liquid contacting
region thereof.
A reservoir of gas supplies the gas at a high pressure (P) to a
flask of gas-depleted liquid. The flask is in liquid communication
with the gas transfer device and in gaseous communication therewith
at a pressure (p), where p is less than P.
The reservoir of gas provides a single source of hydrostatic
pressure for urging the liquid through the contacting members and
the gas around the contacting members so the gas does not diffuse
across the contacting members.
The advantages of the present invention are readily apparent from
the following detailed description of the best mode for carrying
out the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic illustration of a representative apparatus
in which a relatively high partial pressure of a gas can be
achieved in a liquid.
BEST MODE(S) FOR CARRYING OUT THE INVENTION
Turning first to FIG. 1 of the drawing, there is depicted an
apparatus 10 for delivering a high partial pressure of a gas into a
liquid. The apparatus includes a gas transfer device 12 with a
housing 14. Included in the housing is an upstream region 16, a
downstream region 18, and a gas-liquid contacting region 20 with
contacting members 22, such as microporous hollow fibers, or solid
diffusible membranes. The contacting members 22 are located
intermediate the upstream 16 and downstream 18 regions.
To receive a supply of liquid, a gas-depleted liquid inlet port 24
is provided in the upstream region 16. A liquid outlet port 28 is
defined in the downstream region 18 for delivering gas-enriched
liquid to a high resistance delivery channel 44, such as a catheter
for medical applications. For industrial applications, a suitable
delivery device such as a nozzle or its equivalents may be
deployed.
A gas inlet port 32 is defined in the housing 14 for receiving the
gas before contact with the liquid in the contacting region 20.
Also provided in the housing 14 is a gas outlet port 34 for
returning gas which is undissolved in the liquid.
A reservoir 36 of gas supplies the gas at a high pressure (P). In
gaseous communications with the reservoir 36 is a flask 38 of
gas-depleted liquid. If desired; means could be provided for
continuous replenishment of the liquid. As illustrated in FIG. 1,
the flask is in liquid communication with the liquid inlet port 24
and via a "T" junction 46 is in gaseous communication with the gas
inlet port 32 of the gas transfer device 12. First and second
regulators 40, 42 progressively reduce the gas pressure from a
value represented by (P) in the flask 38 to a lower pressure (p)
upon entry into the gas inlet port 32.
Thus, the disclosed apparatus enables the reservoir 36 of gas to
provide a hydrostatic pressure which not only urges the liquid
through the contacting members 22, but also urges the gas around
the contacting members 22. In this way, the gas does not diffuse
across the members, thus promoting mass transfer of the gas into
the liquid.
The apparatus of the present invention will now be described in
further detail. In one set of experiments, a pediatric hollow fiber
(polypropylene) oxygenator (Turumo), which is normally used for
oxygenation of venous blood during extracorporeal circulation in
children was modified. One of two oxygen ports 32, 34 was connected
to a reservoir 36 of oxygen. The partial pressure of the gas was
adjusted with the regulator 40. A tubing from the latter was
connected to a stainless steel tank 38 (Norris, 27 liter capacity)
which had been filled with distilled water.
A liquid conduit section 48 extended below the meniscus of the
liquid contained within the flask, which allowed flow of liquid
from the bottom of the flask to the liquid in port 24 of the gas
transfer device: or oxygenator 12. From a "T" junction 46, a second
regulator 42 allowed adjustment of gas pressure to a value (p) that
was 5 to 20 psi lower than the input pressure (P).
Tubing leading to the regulator 42 was connected to the gas inlet
port 32 of the oxygenator 12.
The arrangement allowed a single tank 36 of oxygen to provide the
driving hydrostatic pressure needed to (1) urge water through the
interior of the hollow fibers 22 within the oxygenator 12 and (2)
cause oxygen to flow around the outside of the bundle of hollow
fibers 22.
The pressure difference across each hollow fiber ensured that
oxygen did not directly diffuse across the hollow fibers in its
gaseous state.
Three different runs performed with a hydrostatic pressure
maintained at approximately 45 psi within the hollow fibers and an
oxygen gas pressure of about 20 psi showed the same result.
When the effluent from the channel 44 was delivered into ordinary
tap water through either a metal or plastic tubing having an
internal diameter of approximately 0.5 mm, no bubbles were noted.
The PO.sub.2 of the effluent was approximately 1800 mm Hg, a value
similar to what would be predicted, assuming full equilibration of
the gas pressure outside the fibers to that dissolved in water
within the fibers.
It should be noted that no additional application of hydrostatic
pressure was found to be necessary to prevent bubble formation.
It is likely that, at relatively low dissolved gas partial
pressures, on the order of a few bar, the use of filtered water,
which had been allowed to stand for many hours, in addition to
sampling the water from the bottom of the tank, was effective for
delivering relatively gas nuclei-free water to the oxygenator.
Increasing the concentration of oxygen within the fibers only
slightly by application of a few bar therefore does not result in
bubble growth, i.e., generation of a high hydrostatic pressure
after enrichment of the water with oxygen is unnecessary.
A hydrostatic pressure of only 45 psi would be insufficient, of
course, for perfusion of coronary arteries through the small
channels available in angioplasty catheters. However, the
relatively large bore tubing (approximately 0.5 mm i.d.) which was
adequate to preserve the stability of the oxygen-supersaturated
water allowed flow rates in the 30 to 100 cc/min range. Catheters
with similar channels would be quite suitable for delivery of an
oxygen-supersaturated cardioplegic solution into the aortic root
during cardiopulmonary bypass procedures.
In a separate run, a similar Terumo hollow fiber oxygenator was
enclosed in a stainless steel housing, so that much higher
pressures could be tested. A SciMed membrane oxygenator may also be
used The arrangement for adjusting hydrostatic and oxygen gas
pressures was similar to that noted above, but regulators which
permitted a maximum pressure of about 500 psi were used.
Hydrostatic pressure was maintained at about 20 to 50 psi greater
than the oxygen gas pressure surrounding the bundle of fibers
(i.e., the gas pressure inside the steel housing, external to the
bundle).
Oxygen gas pressures of approximately 20 psi (to compare to the use
of the oxygenator without the housing above) 150 psi, and 500 psi
were tested. At 150 psi, no bubbles in the effluent were noted when
silica fibers having an internal diameter of 150 microns or less
were tested under tap water. However, at 500 psi, bubbles were
noted in the effluent, even when a silica tubing with an i.d. of 50
microns was used.
The liquid output of the oxygenator was connected to an air-driven
hydraulic pump (SC Hydraulics, Inc.). Hydrostatic pressure was
increased to a range of about 0.7 kbar to 1.0 kbar within a T-tube
mounted at the top of a 600 cc capacity high pressure vessel (High
Pressure Equipment Corp.). The output from the T-tube was connected
to a liquid regulator (Tescom), which allowed a reduction in
pressure to a range of 4,000 psi or less. Following brief
hydrostatic compression in the T-tube, the effluent, delivered at a
pressure of about 3,000 to 4,000 psi through silica tubing having
an i.d. of approximately 75 microns, was completely free of
bubbles.
Thus, conventional oxygenators can be used to provide the high
level of dissolved oxygen sought in clinical or industrial
applications of gas-supersaturated liquids. At relatively low gas
pressures, on the order of a few bar, application of additional
hydrostatic pressure, after enrichment of the liquid with the gas,
is unnecessary if the water is made relatively bubble-free by
filtration and/or prolonged standing, as in the 3 runs performed at
a gas pressure of about 20 psi. Much higher dissolved gas pressures
still benefit from a further increase in hydrostatic pressure, as
described in prior disclosures.
Experimental results have shown that the disclosed apparatus
enables higher pressures to be safely achieved in order to produce
a gas concentration exceeding two bar, both rapidly and
continuously. Thus, the disclosed apparatus, in combination with a
high resistance delivery system, allows the gas-enriched fluid to
be injected into a one bar environment without bubble
formation.
It will be apparent to those of ordinary skill in the art that the
gas-liquid contacting region may embodied in an oxygenator or a
membrane, or their equivalents. If a membrane oxygenator is used, a
silicon membrane is preferred. Suitable oxygenators include those
manufactured by Hoechst Celanese (LIQUI-CEL.RTM. CONTACTORS) and by
Medtronic, (MAXIMA PLUS.sup.198 OXYGENATOR) and their
equivalents.
In addition to oxygen as a gas of choice, air can be used usefully
in combination with water or gasoline, for example, to promote
efficient combustion in an internal combustion engine. Water can be
used in combination with carbon dioxide or nitrogen in certain
industrial applications.
While the best mode for carrying out the invention has been
described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention as defined by the
following claims.
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