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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates broadly to surgical appliances and, more
particularly, to oximetry devices for determining oxygen saturation in a
surgery patient's arterial blood.
Over recent years, the measurement of arterial blood oxygen saturation,
commonly referred to as oximetry, has come into increasingly widespread
usage during surgical procedures as a means for monitoring and preventing
undetected hypoxemia of the surgical patient. Essentially, oximetry
measures the amount of oxygenated hemoglobin in the arterial blood of the
patient as a percentage of the total hemoglobin in the blood.
Various devices, typically referred to as oximeters, are available for
performing oximetry measurements. So-called noninvasive pulse oximeters
are configured to attach to a patient's fingertip, earlobe or nose and are
operable to transmit light of differing wave lengths or colors, typically
in the red and infrared spectrums, into the body part and to detect the
light transmitted therethrough or the light reflected thereby. It is known
that the ability of blood hemoglobin to absorb light varies in relation to
the level of oxygenation of the hemoglobin. Accordingly, detection of the
reflected or transmitted light from a pulse oximeter indicates the amount
of light absorbed, from which the arterial blood oxygen saturation can be
calculated.
While non-invasive pulse oximeters of the aforementioned type provide
substantial advantages over previous oximetry methods which required the
withdrawal of blood samples from a patient, pulse oximeters are still
subject to several disadvantages. First, when the patient is in a state of
low blood perfusion, e.g. when the patient has lost a substantial amount
of blood, is cold, or has peripheral vascular disease or for other reasons
does not perfuse the extremities well, difficulty may often be experienced
in obtaining a sufficient light transmission or reflectance signal from
which to calculate the patient's arterial blood oxygen saturation.
Likewise, ambient light sources and relative movement of the patient and
the oximeter may also interfere with the accuracy of the measurements and
calculations obtained.
During surgery under general anesthesia, it is standard practice to insert
an endotracheal tube through the patient's mouth and into the trachea to
connect the patient to a ventilator to assist breathing. It is well known
that such an endotracheal tube is subject to movement and migration within
the patient's trachea which poses a continual potential problem in
maintaining correct placement and positioning of the tube within the
patient's trachea. Accordingly, it is common practice upon initial
insertion of an endotracheal tube for the anesthetist or anesthesiologist
to check the patient for equal breathing sounds in both lungs, or to
perform a chest radiograph of the patient, or to measure the length of the
tube inserted past the patient's teeth or lips in comparison to
pre-established norms, as a means of determining whether the tube has been
properly positioned. Alternatively, some endotracheal tubes are provided
with a metal band positioned to be detectable by a compatible sensor
placed on the front of the patient's neck in the suprasternal notch when
the tube is properly positioned. Under any of these methods, it is
necessary to periodically perform the same check at appropriate intervals
over the course of the surgical procedure to insure that the proper
positioning of the tube is maintained. Disadvantageously, however, none of
these tube placement methods enables continuous monitoring of the
placement of the endotracheal tube.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a device
which enables oximetry measurements and calculations to be performed
during surgical procedures with improved accuracy over conventional
non-invasive pulse oximeters. It is a particular object of the present
invention to incorporate such oximetry device in an endotracheal tube to
enable more accurate and more quickly responsive oximetry measurements to
be made through the patient's neck while also simultaneously enabling
continual monitoring of the tube position within the trachea.
Briefly summarized, the present invention provides an improved endotracheal
tube for insertion within a surgical patient's trachea for assisting
breathing during surgical and like procedures. According to the present
invention, the tube is provided with an arrangement for transmitting light
outwardly from a predetermined location on the tube which resides within
the patient's trachea during use and a compatible arrangement for
detecting light transmitted by the light transmitting arrangement. The
detecting arrangement is manipulable outside the patient's body for
selective positioning on the patient's neck in disposition for receiving
light transmitted by the transmitting arrangement. A suitable arrangement
is provided for operatively connecting the transmitting arrangement and
the detecting arrangement with an oximeter for measuring oxygen saturation
in the patient's arterial blood as a function of the transmitted light
received by the detecting arrangement.
In one embodiment of the present invention, the transmitting arrangement
includes a light emitting device, such as a light emitting diode, affixed
to the endotracheal tube at the aforesaid predetermined location.
Appropriate electrical wiring extends along the tube from a second
predetermined location thereon which resides outside the patient's body
during use to the first-mentioned predetermined location whereat the
wiring is operatively connected to the light emitting device.
In an alternate embodiment, the light emitting device resides outside the
patient's body and is operatively connected to an optical fiber which
extends along the endotracheal tube to a light emitting terminus of the
fiber at the aforesaid first predetermined location.
The detecting arrangement preferably includes a photosensitive device, such
as a photodiode, detached from and manipulable independently of the
endotracheal tube, the photosensitive device being operatively connected
to the oximeter by suitable electrical wiring which is essentially
unattached to the tube.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic side elevational view of an endotracheal tube
according to one preferred embodiment of the present invention; and
FIG. 2 is another schematic side elevational view, similar to FIGURE
depicting an alternative embodiment of endotracheal tube according to the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the accompanying drawings and initially to FIG. 1 an
endotracheal tube according to the preferred embodiment of the present
invention is generally indicated at 10. Basically, the endotracheal tube
10 includes a tube body 12 to which an oximetry measuring probe and sensor
assembly, collectively indicated at 14, is affixed.
The tube body 12 may be of any conventional endotracheal tube construction,
the tube body 12 illustrated in FIG. 1 being schematically representative
of one common type of endotracheal tube. Basically, the tube body 12 is
hollow along its entire length and is open at its opposite leading
(distal) and trailing (proximal) ends 16,18, respectively. A radially
outwardly expansible cuff 20, e.g., an inflatable balloon, is affixed
exteriorly to the tube body 12 closely adjacent its leading end 16 and a
side port 22 is formed through the annular wall of the tube body 12
intermediate the cuff 20 and the leading end 16. One or more appropriate
passageways (not shown) are formed through the outer wall of the tube body
12 along its length and are connected to a suitable valve or the like
(also not shown) for supplying and exhausting inflating air to and from
the cuff 20. A radially outwardly projecting collar 24 is formed at a
close spacing to the trailing end 18 of the tube body 12 to facilitate
end-to-end connection of the trailing end 18 to a flexible hose (not
shown) extending from a ventilator or other conventional breathing
apparatus.
In use, the leading end 16 of the tube body 12 is inserted through a
surgical patient's mouth and throat into the trachea within the patient's
neck and, when properly positioned, the cuff 20 is inflated to assist in
retaining the leading end 16 in its desired disposition within the
trachea. The tube body 12 is of sufficient length that the trailing end 18
remains outside the patient's mouth, adhesive surgical tape typically
being applied about the tube to the patient's mouth to essentially seal
the patient's lips to the tube body 12. Upon connection of the trailing
end 18 of the tube body 12 to a breathing apparatus, a controlled supply
of oxygen can be delivered to the patient during surgery.
The oximetry measuring probe and sensor assembly 14 includes a connection
cable 26 by which the assembly 14 is connectable to an oximetry measuring
and calculation unit, only representatively indicated at 28, which may be
of any conventional construction. The connection cable 26 includes a first
electrical lead wire 30 affixed to or embedded in the annular wall of the
tube body 12 to extend from a proximal location closely adjacent the
collar 24, which location resides outside the patient's body during use,
to a distal location closely adjacent the cuff 20, which location resides
within the patient's trachea during use, whereat the lead wire 30 is
operatively connected to one or more light emitting devices 32, preferably
in the form of light emitting diodes. The connection cable 26 also
includes a second electrical lead wire 34 which extends outwardly from the
cable 26 without connection to the tube body 12 and is operatively
connected at its extending free end to one or more photosensitive devices
36, preferably in the form of photodiodes.
In operation, the light emitting diode or diodes 32 are operatively
controlled by the oximetry device 2 to emit light in a direction radially
outwardly from the tube body 12 and the photodiode 36 is adapted to
receive and detect light transmitted by the light emitting diode or diodes
32 when the photodiode or photodiodes 36 are positioned within the path of
transmitted light. The lead wire 34 is flexible so as to enable the
photodiode or photodiodes 36 to be freely movable and manipulable for
placement of the photodiode or photodiodes 36 at an location on the
anterior surface of the patient's neck to intercept light transmitted by
the light emitting diode or diodes 32 on the distal portion of the tube
body 12 within the patient's trachea. Once the photodiode or photodiodes
36 are positioned to detect transmitted light from the light emitting
diode or diodes 32, the photodiode or photodiodes 36 are finally
positioned to maximize the light reception and, thereafter, are maintained
in direct contact with the skin of the patient's neck, e.g. by surgical
tape.
Thus, upon initial insertion of the tube body 12 into the trachea of a
surgical patient, the light emitting diode or diodes 32 and the photodiode
or photodiodes 36 enable the disposition of the leading (distal) end of
the tube body 12 within the patient's trachea to be detected and, in turn,
to be precisely positioned where desired. Likewise, throughout the ensuing
surgical operation, the positioning of the leading end 16 can be
continuously monitored. Simultaneously, the oximetry measuring and
calculation device 28 compares the amount or intensity of light detected
by the photodiode or photodiodes 36 with the amount or intensity of light
transmitted by the light emitting diode or diodes 32 to obtain a
measurement of the amount of light absorbed by the hemoglobin in the blood
passing through the intervening arteries through the patient's neck. In
conventional fashion, the oximetry device controls the light emitting
diode or diodes 32 to transmit both red and infrared light in performing
such measurements and, from such measurements calculates the level of
arterial blood oxygen saturation for the patient.
Advantageously, since the human body automatically preserves blood flow
through the arteries in the neck to the brain at the cost of blood flow to
the extremities or more peripheral skin regions, the blood oxygen
saturation measurements and calculations obtained by light transmission
through the neck under the present invention will not only be more
accurate but also more quickly responsive to oxygen saturation changes
than with conventional pulse oximetry devices attachable to a patient's
fingertip, earlobe, or nose. At the same time, the artifact associated
with ambient light will affect the oximetry calculations under the present
invention to a substantially lesser degree than with conventional pulse
oximeters. Further, as aforementioned, the provision of an oximetry light
emitting device on an endotracheal tube in accordance with the present
invention enables the positioning of the tube within the patient's trachea
to be continuously monitored over the entire course of a surgical
procedure.
Referring now to FIG. 2, an alternative embodiment of the endotracheal tube
of the present invention is indicated generally at 110 and basically
includes a tube body 112 identical to that of the embodiment of FIG. 1
with an alternative form of oximetry measuring probe and sensor assembly
114. In this embodiment, the oximetry probe and sensor assembly 114
utilizes a light emitting diode or other light emitting device 132
disposed outside the patient's body and a flexible light-transmitting
optical fiber 130 connected to and extending from the light emitting diode
132 through the annular wall of the tube body 112 from a proximal location
closely adjacent the tube collar 124 to a distal location closely adjacent
the tube cuff 120 whereat a terminus 130' Of the optical fiber 130 is
exposed at the exterior surface of the tube body 112 for transmitting
light radially outwardly therefrom. The light emitting diode 132 is
electrically connected to a connection cable 126 along with a lead wire
134 to a photodiode 136 substantially identically to that of the
embodiment of FIG. 1 for selective manipulation and positioning to
intercept light transmitted from the optical fiber terminus 130'. As will
thus be understood, operation of the endotracheal tube 110 and the
attendant advantages thereof are the same as described above for the
endotracheal tube 10.
It will therefore be readily understood by those persons skilled in the art
that the present invention is susceptible of a broad utility and
application. Many embodiments and adaptations of the present invention
other than those herein described, as well as many variations,
modifications and equivalent arrangements will be apparent from or
reasonably suggested by the present invention and the foregoing
description thereof, without departing from the substance or scope of the
present invention. Accordingly, while the present invention has been
described herein in detail in relation to its preferred embodiment, it is
to be understood that this disclosure is only illustrative and exemplary
of the present invention and is made merely for purposes of providing a
full and enabling disclosure of the invention. The foregoing disclosure is
not intended or to be construed to limit the present invention or
otherwise to exclude any such other embodiments, adaptations, variations,
modifications and equivalent arrangements, the present invention being
limited only by the claims appended hereto and the equivalents thereof.
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