U.S. patent number 3,807,390 [Application Number 05/312,099] was granted by the patent office on 1974-04-30 for fiber optic catheter.
This patent grant is currently assigned to American Optical Corporation. Invention is credited to David Ostrowski, Michael L. Polanyi.
United States Patent |
3,807,390 |
Ostrowski , et al. |
April 30, 1974 |
FIBER OPTIC CATHETER
Abstract
A flexible fiber optic catheter insertable into the
cardiovascular system for monitoring blood oxygen saturation. The
catheter has a distal cage for preventing its end face from
contacting vessel walls or the endocardium during use. The cage is
terminated with a smoothly surfaced ball which is adapted to
provide fixed reflections of light directed thereon from the
catheter when in air or placed in a clear sterile solution for
calibration prior to use.
Inventors: |
Ostrowski; David (Dudley,
MA), Polanyi; Michael L. (Webster, MA) |
Assignee: |
American Optical Corporation
(Southbridge, MA)
|
Family
ID: |
23209881 |
Appl.
No.: |
05/312,099 |
Filed: |
December 4, 1972 |
Current U.S.
Class: |
600/332; 385/117;
356/41; 385/119; 604/523 |
Current CPC
Class: |
A61B
5/155 (20130101); A61B 1/0008 (20130101); A61B
5/150992 (20130101); A61B 5/153 (20130101); A61B
5/1459 (20130101); A61B 1/00165 (20130101); A61B
5/15003 (20130101); A61B 2560/0233 (20130101) |
Current International
Class: |
A61B
5/00 (20060101); A61B 5/15 (20060101); A61B
1/00 (20060101); A61b 005/02 () |
Field of
Search: |
;128/2.5R,2.5D,2.5F,2L,DIG.9,DIG.16 ;356/41 ;350/96B,175SL |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Laudenslager; Lucie H.
Attorney, Agent or Firm: Nealon; William C.
Claims
We claim:
1. A fiber optic catheter for use in measuring amounts of diffuse
reflection of light in blood, said catheter having a multiplicity
of light-conducting fibers and a catheter tubing surrounding said
fibers, the fibers all being intimately juxtaposed adjacent the
distal end of said catheter with corresponding end faces thereof
exposed at said distal end and separated into a pair of branches
adjacent the opposite proximal end of said catheter, corresponding
fibers of each branch being intimately juxtaposed and respective
end faces thereof exposed; wherein the improvement comprises;
a rigid ball disposed forwardly of said exposed faces of said
fibers at said distal end of said catheter and spaced away
therefrom a distance greater than a maximum distance of penetration
of light into blood whereby light emitted from said exposed faces
of said fibers will be prevented from reaching said ball when said
distal end of said catheter is placed in blood, said ball further
being formed of a substance which characteristically reflects a
fixed ratio of at least two preselected wavelengths of light
directed thereupon from said exposed faces of said fibers at said
distal end of said catheter when said distal end including said
exposed faces and said ball is disposed in air and clear liquids;
and
a pair of slender posts supporting said ball in said spaced
relationship with said fiber faces, said posts respectively
extending from approximately diametrically opposed sides of said
ball in a direction longitudinally of said catheter tubing and
being secured to said distal end of said catheter for completing
the configuration of a cage permitting a free flow of blood between
said ball and adjacent fiber faces when said catheter distal end is
placed in said blood for testing thereof, said cage further
preventing contact of said exposed fiber ends with walls of means
containing said blood.
2. A fiber optic catheter according to claim 1 wherein said fibers
of each of said branches are randomely intermixed adjacent said
distal end of said catheter.
3. A fiber optic cather according to claim 1 wherein said fibers in
said branches are maintained in correspondingly separated
relationship throughout the length of said catheter.
4. A fiber optic catheter according to claim 1 wherein said pair of
slender posts comprise oppositely disposed extensions of a looped
length of wire and said ball is affixed to the intermediate looped
portion of said wire.
5. A fiber optic catheter according to claim 1 wherein said ball is
formed of a white pigmented plastic material.
6. A fiber optic catheter according to claim 1 wherein said ball is
formed of metal.
7. A fiber optic catheter according to claim 4 wherein said ball is
molded over said looped intermediate portion of said length of
wire.
8. A fiber optic catheter according to claim 1 wherein said slender
posts are at least partially imbedded in said catheter tubing and
said tubing is smoothly finished thereover.
9. A fiber optic catheter according to claim 1 in combination with
means for introducing light into said exposed end faces of one of
said branches and photoelectric means for receiving light emitted
from said exposed faces of the other of said branches.
10. A fiber optic catheter in the combination according to claim 9
further including means for determining ratios of amounts of light
of two preselected wavelengths returned through said catheter from
said distal end to one of said branches at said proximal end.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention:
Fiber optic catheters with particular reference to catheters
intended for insertion into the cardiovascular system.
2. Description of the Prior Art:
In-vivo fiber optic catheters which are sterilized before use
require calibration in conjunction with their associated
electro-optical equipment so that absolute values of oxygen
saturation or dye concentration and/or accurate measurements of
variations thereof with time are made possible in the performance
of blood oxygen saturation determinations or dye dilution
measurements with these catheters.
Heretofore, catheter calibration has required that the distel end
of the catheter be placed in a sterile suspension medium such as
milk-of-magnesia which will give a fixed ratio of reflections of
wavelengths of light such as 805mu and 660mu or others which may be
used for blood oxygen saturation or dye dilution testing. This
method of calibrating in-vivo catheters, however, is potentially
dangerous to patients since portions of the suspension medium
clinging to the catheter may become introduced into the patients
blood stream. These inclusions in not being isotonic with blood and
embolic, are potentially dangerous to the patient and, leastwise,
may adversely affect the accuracy of oxygen saturation
determinations and/or other measurements taken with the in-vivo
catheter and its associated equipment.
This invention makes it possible to calibrate in-vivo catheters
without the subsequent danger of introducing extraneous matter into
the blood stream and further provides an improved catheter tip
design offering minimal obstruction and resistance to a flow of
blood therethrough and maximum exposure of all of its external
surfaces for cleaning and sterilization.
SUMMARY OF THE INVENTION
The objectives of this invention are accomplished by providing the
fiber optic catheter in this case with a forwardly directed cage
protecting its end face against coming into contact with or close
enough relationship to the blood vessel walls or endocardium to
cause problems of errors in oxygen saturation determination or
other tests being conducted by intravascular and intracardiac fiber
optic catherization. This cage uniquely comprises a dual pronged
configuration, e.g., a single loop or wire, having a ball tip of a
diametral size approximating the thickness of the catheter. The
ball is formed of a substance which will provide a fixed ratio of
reflections of wavelengths of light emitted from the catheter face
when the catheter tip is in air or in a clear sterile solution
after sterilization. By such means, the fixed ratio of reflections
may be used to calibrate the catheter and its associated
instrumentation so that absolute readings of oxygen saturation, for
example, or other accurate measurements may be obtained. With
calibration performed in a clean air environment or a clear saline
solution which is isotonic with body fluids, such hazards as
contamination of patient's blood or the creation of embolisms
therein by residue of conventional calibrating suspension mediums
is avoided.
Details of the invention will be more readily understood by
reference to the following description taken in conjunction with
the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration, in perspective, of a fiber optic
catheter and system of a type useful in performing in-vivo testing
of blood wherein the catheter incorporates a preferred embodiment
of the invention;
FIG. 2 is a greatly enlarged fragmentary view, in perspective, of
the distal end portion of the catheter of FIG. 1 showing the
embodiment of the invention in greater detail; and
FIG. 3 is a fragmentary longitudinal cross-sectional view of the
portion of the catheter shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fiber optic catheter 10 comprises a length of standard cardiac
catheter tubing 12 containing a bundle 14 of efferent and afferent
light-conducting fibers 16 (FIGS. 2 and 3).
Included with the bundle 14 of light-conducting fibers 16 is tube
18 which may be disposed centrally of bundle 16 or to one side
thereof as illustrated in FIG. 2. Tube 18 which may be used for
monitoring blood pressure or withdrawing samples of blood or
introducing a medication is conventional. Also conventional in
catheters of this type are optical fibers 16, some of which conduct
light efferently through catheter 10 toward its distal end and
others of which receive and conduct light afferently toward its
proximal end. These fibers in bundle 14 may be randomly intermixed
adjacent the distal end of catheter 10 and respectively
individually separated into branches 20 and 22 at the proximal end
of catheter 10 (FIG. 1). Alternatively, they may be retained in
separately bundled relationship throughout the entire length of
catheter 10. Those interested in greater details of fiber optic
catheter constructions and/or the construction and function of
individual fibers may refer to U.S. Pat. Nos. 3,068,742 and
3,068,739.
In determining oxygen saturation of blood in-vivo with catheter 10,
for example, light from lamp 24 is introduced into the optical
fibers contained in one branch 20 of the catheter for conductance
through the catheter and emission outwardly thereof at its face 26
directly into blood within a vessel or heart chamber of the
cardiovascular system into which the catheter is inserted for this
purpose. This light, upon entering the blood becomes diffusely
reflected thereby back toward and partially into face 26 for
reception by afferent fibers therein which convey the reflected
light back through catheter 10 to and outwardly of branch 22. It is
then received by a photodetector 28 from which a measurement of its
intensity may be made.
To the extent that catheter 10 and its function in determining
oxygen saturation of blood have been thus far described, the
catheter and its associated light source and photoelectric detector
28 are conventional and explained in detail in the aforementioned
U.S. Pat. Nos. 3,068,742 and 3,068,739. As is also explained in
these patents, typical wavelengths of light useful in performing
in-vivo oxygen saturation determinations are 805mu and 660mu which
may be alternately or intermitently supplied to branch 20 of
catheter 10 by positioning suitable light filters 30 and 32 in the
path of light from lamp 24. Filters 30 and 32 may be supported in a
rotating disc 34 as illustrated in FIG. 1 or in a sliding mechanism
as shown and described in the aforementioned U.S. patents.
Alternatively, the filters 30 and 32 may be replaced by a suitable
dichroic beam splitter placed so as to receive the light returned
by catheter through branch 22 and direct preselected individual
wavelengths of this light along separate paths to two or more
photoelectric detectors similar to detector 28 from which
interpretation of the ratio of intensities of the different
wavelengths of light may be accomplished for determination of blood
oxygen saturation. This latter arrangement of beam splitting and
individual photoelectric detection of different wavelengths of
light may be found in U.S. Pat. No. 3,296,922.
In order to render catheter 10 and its associated electro-optical
system capable of affording absolute and/or accurate measurement of
oxygen saturation or dye dilution in-vivo with each application of
catheter 10 to the body, calibration of the catheter and its
associated electro-optical instrumentation is required as is
explained in U.S. Pat. Nos. 3,068,742; 3,068,739; and 3,296,922.
This calibration, accordingly, requires that a portion of light
directed through and emitted from face 26 of catheter 10 be
returned therethrough with a fixed ratio of reflections, e.g.,
805mu/ mu. This, has been accomplished heretofore by placing face
26 of catheter 10 in a suspension medium of, for example,
milk-of-magnesia whereupon a zero or other preselected meter
reading of an electro-optical measuring system used in conjunction
with catheter 10 may be established as a reference for interpreting
readings of blood oxygen saturation or dye concentration
in-vivo.
According to the present invention, a fixed ratio of reflections of
light emitted from face 26 of catheter 10 is accomplished in air or
in a clear saline solution or the like, i.e., without contamination
of the catheter by non-isotonic mediums such as milk-of-magnesia,
as follows: Catheter tubing 12 is longitudinally slotted adjacent
face 26 at diametrically opposite sides to receive each of the free
ends 36 of a two pronged, hairpin-like cage 38 which extends
forwardly from the slotted catheter tubing 12 beyond face 26. A
ball 40 at the end of cage 38 is grooved and set into place or
previously molded over the looped end 42 of cage 38. The ball 40
may be formed of metal and cemented or soltered in place or,
preferably, molded of a white pigmented epoxy which will not
degrade or deteriorate when exposed to gas sterilization, e.g.,
ethylene oxide gas. In either case, ball 40 is highly polished or
otherwise smoothly finished and is preferably of a diameter
approximately equal to the diametral thickness of catheter tubing
12. Ends 36 of cage 38 are permanently fixed to catheter 10
preferably with a binding wire or cord 44 wrapped therearound in a
circumferential slot extending about catheter tubing 12. Once ends
36 of the cage are secured in place, the slots are filled with a
suitable cement preferably of the epoxy type which forms a smooth
outer surface flush and continuous with the main outer surface of
catheter tubing 12. All potentially sharp edges of the catheter are
removed by rounding and/or polishing and all corners between face
26 and cage 38 as well as between ball 40 and the wire legs of the
cage are open and readily accessible for cleaning and
sterilization.
In use, the distal end of the catheter is inserted into the
cardiovascular system with the smoothly finished ball 40
functioning to guide the catheter thereinto with minimal friction
and/or irritation to vascular walls of the endocardium while
keeping face 26 of the catheter sufficiently spaced therefrom to
permit a free flow of blood across face 26 at all times.
Prior to use or reuse of catheter 12 it must, in either case, be
sterilized, e.g., by exposure to ethylene oxide gas, and then
calibrated in conjunction with the electro-optical system with
which it may be used for performing oxygen saturation or dye
dilution measurements. This calibration, with the cage 38 of the
present invention may be performed simply in a clean air
environment by directing light of wavelengths intended to be used
for testing through afferent fibers 16 of bundle 14 which light
becomes emitted from face 26 and reflected from ball 40 as shown by
arrows in FIG. 3 reversely upon face 26. All directions of
reflection being fixed and constant, calibration of the catheter
and its associated instrumentation according to the ratio of light
wavelengths (e.g., 805mu and 660mu) returned through the catheter
may be accomplished. The instrument measuring meter may be set to
read zero at this time or, alternatively, set to read a percentage
of blood oxygen saturation, e.g., 85 percent which is known to
reflect the same ratio of light wavelengths.
This calibration, in either case, is performed without
contamination of the catheter by the heretofore requirement that it
be placed in a non-isotonic medium. It should be understood that
calibration of catheter 10 with ball 40 of cage 38 may be
accomplished within a clear isotonic liquid such as a saline
solution if desired.
When the catheter is inserted into the cardiovascular system
wherein the space between ball 40 and face 26 is filled with blood,
ball 40 has no effect upon the reflection of light from the blood
back into face 26. The density of blood prevents light, especially
805 and 660mu wavelengths, from penetrating appreciably thereinto
before diffuse reflection. The spacing between face 26 and ball 40
is considerably greater than a distance in blood capable of being
penetrated by light and especially, even greater than a distance
through which light might be directed and returned by reflection in
blood.
In addition to catheter 10 being adaptable to calibration without
immersion of its distal end in an extraneous calibrating medium,
its cage 38 construction, having only two posts 48, uniquely
renders this catheter relative to conventional catheters, more
readily adaptable to cleaning and complete sterilization and less
resistant to the circulation of blood through its cage with a
corresponding lessening of tendencies for clotting.
* * * * *