U.S. patent application number 13/848766 was filed with the patent office on 2013-08-29 for device, apparatus and method for obtaining physiological signals by way of a feeding tube.
This patent application is currently assigned to KONINKLIJKE PHILIPS ELECTRONICS N.V.. The applicant listed for this patent is KONINKLIJKE PHILIPS ELECTRONICS N.V.. Invention is credited to DAVID LAWRENCE FEER, ROBERT ALFRED FEUERSANGER, BRIAN DAVID GROSS, SUZANNE KAVANAGH, ERIC DONALD NELSON, DANIEL SILBER.
Application Number | 20130225946 13/848766 |
Document ID | / |
Family ID | 41168419 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130225946 |
Kind Code |
A1 |
FEER; DAVID LAWRENCE ; et
al. |
August 29, 2013 |
DEVICE, APPARATUS AND METHOD FOR OBTAINING PHYSIOLOGICAL SIGNALS BY
WAY OF A FEEDING TUBE
Abstract
A neonatal feeding tube (10) includes electronics and
instrumentation for monitoring a neonate and for provides
nourishment to the neonate. The tube (10) includes electrodes (20)
for sensing ECG signals of the neonate. Thermistors (22, 24, 28,
30) are placed at various points along the tube (10) to measure the
neonate's temperature at those points. Breathing effort is measured
by calculating a pressure differential at two pressure ports (32,
34). Pulse and SpO.sub.2 are measured at a fiber optic window (35).
The electrodes (20), a distal electrode (64) and a light source
(66) aid in helping a caregiver position the tip (12) of the tube
(10) correctly in the stomach of the neonate.
Inventors: |
FEER; DAVID LAWRENCE;
(BROOKLINE, MA) ; FEUERSANGER; ROBERT ALFRED;
(WESTFORD, MA) ; GROSS; BRIAN DAVID; (NORTH
ANDOVER, MA) ; KAVANAGH; SUZANNE; (ANDOVER, MA)
; NELSON; ERIC DONALD; (HAMPTON FALLS, NH) ;
SILBER; DANIEL; (LEXINGTON, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS ELECTRONICS N.V.; |
|
|
US |
|
|
Assignee: |
KONINKLIJKE PHILIPS ELECTRONICS
N.V.
Eindhoven
NL
|
Family ID: |
41168419 |
Appl. No.: |
13/848766 |
Filed: |
March 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13057769 |
Feb 7, 2011 |
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PCT/IB2009/053550 |
Aug 11, 2009 |
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13848766 |
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61092468 |
Aug 28, 2008 |
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Current U.S.
Class: |
600/301 ;
600/376 |
Current CPC
Class: |
A61B 5/04 20130101; A61B
5/0538 20130101; A61B 5/0402 20130101; A61B 2562/223 20130101; A61B
5/0809 20130101; A61B 5/1459 20130101; G16H 40/60 20180101; A61B
5/01 20130101; A61B 5/0878 20130101; A61B 5/4233 20130101; A61J
15/0003 20130101; A61B 5/0205 20130101; A61J 15/0073 20130101; A61B
2562/224 20130101; A61J 15/0084 20150501; A61J 15/0011 20130101;
A61B 5/0421 20130101; A61B 5/02055 20130101; A61B 5/72 20130101;
A61B 2562/164 20130101; A61B 2562/222 20130101; A61B 5/037
20130101; A61B 5/02 20130101 |
Class at
Publication: |
600/301 ;
600/376 |
International
Class: |
A61B 5/042 20060101
A61B005/042 |
Claims
1. An orogastric or nasogastric feeding tube comprising: a molded
or jacketed build up of discrete parts such as lumen, wires,
electromechanical components; wire layered onto a center lumen that
is over-molded, cast, or encapsulated after layering; molded
in-wall wires in a single lumen or a multi-lumen extrusion; or a
discrete wire bundle installed into one of multiple lumens, the
multiple lumens physically separate a feeding path in one of the
lumens from the electro-mechanical components; tubular construction
defining at least one lumen that provides a pathway for nourishment
from outside of a subject into the stomach or small intestine of
the subject; and, at least one thermistor located within the tube,
wherein the positioning of the tube automatically locates at least
one thermistor to measure at least one of esophageal,
nasopharyngeal, oropharyngeal and hypopharengeal temperature.
2. The feeding tube of claim 1, wherein the tubular construction
includes at least one of: a molded or jacketed build up of discrete
parts such as lumen, wires, electromechanical components; wire
layered onto a center lumen that is over-molded, cast, or
encapsulated after layering; molded in-wall wires in a single lumen
or a multi-lumen extrusion; or a discrete wire bundle installed
into one of multiple lumens, the multiple lumens physically
separate a feeding path in one of the lumens from the
electro-mechanical components.
3. The feeding tube of claim 1, further including: a plurality of
lumens, a wiring bundle, and/or optical fiber bundles substantially
in a center of the lumens.
4. The feeding tube of claim 1, further including: an oropharynx
thermisto for monitoring a temperature and .DELTA.T synonymous with
flow of the subject in a region of the subject's pharynx; a
hypopharynx thermistor for monitoring a temperature of the subject
inferior to the pharynx of the subject; an esophageal thermistor
for monitoring core temperature of the subject, and wherein
optionally at least one of the thermistor is a segmented
thermistor.
5. The esophageal feeding tube of claim 1, wherein: a
supra-diaphragmatic pressure port for monitoring a pressure of the
subject superior to the diaphragm of the subject; a
sub-diphragmatic pressure port for monitoring a pressure of the
subject inferior to the diaphragm of the subject; flush fibers.
6. The esophageal feeding tube of claim 1, wherein at least one of:
fiber-optic filaments that provide light to a fiber optic window
adjacent to the jacket that senses pulse and SpO.sub.2; a soft
molded tip that is attached to a distal end of the feeding tube; or
a light source at the tip of the feeding tube for visually tracking
the tip of the feeding tube; or a distal electrode at the tip of
the feeding tube for indicating when the tip of the feeding tube
passes into the stomach of the subject.
7. The feeding tube of claim 1 which implements a monitoring
algorithm to select which of the electrodes has an optimal signal,
whereby the algorithm can be implemented when the feeding tube is
inserted or periodically as the subject grows and the feeding tube
is repositioned.
8. A method of inserting an esophageal feeding tube into a subject
comprising: inserting the feeding tube into the esophagus of the
subject; advancing the feeding tube to a position estimated to
place a tip of the feeding tube in a selected location in a stomach
or small intestine of the subject; sensing cardiac activity with at
least two electrodes, of which at least two are active at any given
time; processing the sensed cardiac activity to compare waveforms
at each of the segments measured; and, analyzing the relative
waveforms to determine when the feeding tube is located at the
selected location, such as when the active electrode is adjacent an
SA node to position the tip based on biometric or demographic
information related to the patient, e.g. biometric information,
age, gender, head circumference, or the like, and confirm that the
tube is properly placed, should be further advanced, or should be
retracted.
9. The method of claim 8, wherein there are at least three
electrodes and further including: selecting a subset of the
electrodes that detect the equipotential cardiac signals to
continuously monitor cardiac activity of the subject.
10. The method of claim 9, further including at least one of:
monitoring respiration signal or core temperature of the subject
with an esophageal thermistor; monitoring a temperature of the
subject in a region of the pharynx of the subject with an
oropharynx thermistor; or monitoring a temperature of the subject
inferior to the pharynx of the subject with a hypopharynx or
esophageal thermistor.
11. The method of claim 10, including: measuring a respiration
effort by: monitoring a pressure of the subject superior to the
diaphragm of the subject with a supra-diaphragmatic pressure port;
monitoring a pressure of the subject inferior to the diaphragm of
the subject with a sub-diphragmatic pressure port; and, calculating
a change in pressure to generate a respiration effort signal.
12. The method of claim 11, wherein the feeding tube includes a
tubular construction with at least one lumens that provides a
pathway for nourishment and further including: providing light to a
fiber optic window adjacent to the tubular construction with fiber
optic filaments.
13. The method of claim 12, including: visually tracking the tip
through the thorax or abdomen with a light source and fiber optic
component; tracking the position of the tip with a distal electrode
that conducts when in contact with the esophageal wall, and changes
conductivity when it passes into the stomach of the subject;
tracking the tip during insertion by monitoring at least one of
temperature and/or pressure for a fluctuating reading indicative of
air flow channels and a constant reading indicative of location in
the esophagus; and, As such, if .DELTA.T or .DELTA.P equals zero,
then the tube is correctly placed into the esophagus; verifying the
tip is in the stomach after insertion by measuring the pH at the
tip.
14. The method of claim 13, wherein the analyzing step includes
sensing relative strength of signals from the electrodes to select
which of the electrodes are to be active and, optionally, as the
patient grows, repeating the analyzing step to re-select which of
the electrodes are to be active without repositioning the feeding
tube.
Description
[0001] This application is a Continuation of prior U.S. patent
application Ser. No. 13/057,769, filed Jun. 16, 2011, which is the
U.S. National Stage application of International Application No.
PCT/IB2009/053550, filed Aug. 11, 2009, which claims priority to
U.S. Provisional Application No. 61/092,468, filed Aug. 28,
2008.
DESCRIPTION
[0002] The present application relates to neonatal and pediatric
care. It finds particular application with a feeding tube
associated with the care of newborns, and will be described with
particular reference thereto. It is to be appreciated, however,
that many of the concepts are scalable to pediatric and adult
applications, and are not limited to the aforementioned
application.
[0003] When caring for newborn babies, the size of the patient is
an obvious difference when compared to adult patients or other
pediatric patients. Because the patient is so much smaller,
instruments, sensors, and the like have to be redesigned to be used
with newborn patients. This task is not obvious to those skilled in
the art and this invention includes novel techniques to capture
familiar vital signs.
[0004] Neonates that need tube feedings typically are also
monitored electronically by a physiologic monitor. Such monitors
use multiple electrodes and sensors adhered to the patient's chest
and abdomen in order to capture ECG signals for calculating heart
rate and for obtaining a respiration-impedance waveform for
calculating respiration rate. Adhesion of skin electrodes is a
problem for neonates. Not only must the adhesive have the proper
electrical characteristics to transmit electrical signals, it also
must adhere well enough to maintain adequate signal integrity
despite motion artifacts. Also, due to poor skin development and
the criticality for fluid balance in the presence of insensible
water loss (evaporation), neonates are frequently maintained in
humidity and temperature controlled incubators which not only
compound the problem of electrode adhesion, but create a need to
obtain a feedback signal for the thermoregulation apparatus
typically found in the incubator. Each time an electrode or sensor
falls off, a caregiver must intervene immediately, which increases
the workload of the care giving staff, and is disruptive to the
important sleep cycle of the neonate.
[0005] Further, the preterm neonate typically lacks skin integrity
and the frail skin is subject to irritation and laceration as a
result of applying adhesives or sensors. Removal of said electrodes
or sensors for routine skin integrity checks and cleaning can
further irritate the delicate skin of the neonate during removal.
In practice, there is no perfect adhesive for a neonatal skin
electrode. External electrodes and their cables also complicate
routine care of the neonate (e.g., washing) and may be disturbing
to parents trying to bond with the infant.
[0006] As with all intensive care patients, temperature changes can
indicate fever or other medical situation requiring attention. In
the case of premature neonates, however, the thermoregulatory
system is not yet fully developed, so unlike the adult population,
a neonate's temperature can go into crisis within minutes (as
opposed to hours for an adult) and thus must be monitored closely.
Consequently, routine and continuous temperature monitoring is
conducted in the neonatal intensive care unit (NICU). This is
typically done with a thermistor probe temporarily placed in the
armpit, groin, or skin. These temperature sensors entail excessive
stimulation for the neonate, a factor which is believed to
negatively impact development. Often, NICU patients are kept in
incubators. Opening and closing the incubator in order to maintain
temperature signals makes it difficult to maintain desired air
temperature control inside the incubator.
[0007] Also, size from infant to infant can vary immensely. Viable
premature babies are much smaller than their full term
counterparts, in both weight and length. In the case of a neonatal
feeding tube, the size of the tube is tailored to the size of the
infant. In order to accommodate a range of sizes of infants,
different sizes of tubes are typically required so the tip of the
feeding tube rests in the stomach. Moreover, as newborn babies grow
rapidly, an infant's feeding tube may need to be changed and or
repositioned during its stay.
[0008] During insertion of a new feeding tube, care must be taken
and verification checks made to assure that the tube has followed
the esophageal path to the stomach and not the bronchial path into
the lungs. Further, the opening(s) in the tube must be properly
positioned in the stomach, not the esophagus, and the end of the
tube must terminate before reaching the bottom of the stomach.
Incorrect positioning of the feeding tube can result in aspiration
of stomach contents and feeding material into the lungs, which can
lead to a life-threatening lung infection or injury.
[0009] The present application provides a new and improved feeding
tube, which overcomes the above-referenced problems and others.
[0010] In accordance with one aspect, an esophageal feeding tube
that incorporates at least one lumen (tube) for feeding and
provides a pathway for nourishment from outside of a subject into
the stomach of the subject. At least two, but optimally three or
more uniformly or non-uniformly spaced electrodes are on the
outside of the feeding tube for measuring cardiac and respiratory
activity of the patient, of which at least two electrodes are used
at any given time.
[0011] In accordance with another aspect, an improved method of
inserting an esophageal feeding tube into a subject is provided.
The feeding tube is inserted into the esophagus of the subject. The
feeding tube is advanced to a position estimated to place the tip
of the feeding tube in the stomach of the subject. Cardiac activity
is sensed at all electrodes simultaneously and the SA node (cardiac
pacing center) of the heart location is detected by equidistributed
depolarization (equal positive and negative inflection through the
isoelectric line cardiac cycle (Figure X). Once this location is
detected, the distance to the proper tip placement in the patient
is a mathematical function of head circumference in the neonate and
maybe in the pediatric patient and adult. The sensed cardiac
activity is processed to compare relative strengths of the activity
sensed. The relative strengths are analyzed to determine whether
the feeding tube is properly placed, requires further advancement,
or requires retraction.
[0012] In accordance with another aspect, a method of monitoring a
subject is provided. A lumen is provided for nourishment from
outside of the subject into the stomach of the subject. The lumen
and electronic conductors may be integrally constructed or
assembled and then encased in a jacket. At least two electrodes,
needed to measure impedance for respiration rate calculations, are
positioned along the outside of the feeding tube for measuring
cardiac and respiration activity of the subject, of which at least
two of the electrodes are active at any given time.
[0013] In accordance with another aspect, a method of monitoring a
subject is provided. A lumen is provided for detecting pressure
above and below the diaphragm (see Figure #XX) thus enabling a
pressure differential monitoring indicating respiration effort and
aiding in respiration rate and respiration effort detection. As the
tube is inserted, the differential pressure is monitored until a
minimal, e.g., zero, differential pressure is sensed to indicate
proper placement. In accordance with another aspect, a method of
monitoring a subject's respiration is provided. A low-mass
thermistor is provided for detecting rapid temperature changes in
the hypopharynx and another below the diaphragm, thus enabling a
flow mode and differential flow temperature monitoring to indicate
respiration air flow rate and volume calculation indicating flow.
This also aids in the detection of proper tube placement. As the
tube is inserted, temperature changes are monitored to determine if
the thermistor is in the esophagus or the trachea. As the tube
enters the trachea, temperature fluctuation both at a single point
and between 2 points and therefore a respiration signal is still
detected; but if tube is in the esophagus, there is no delta
temperature detected, therefore no respiration signal is seen.
[0014] An advantage of this design is the opportunity to similarly
measure SpO.sub.2 insofar as esophageal SpO.sub.2 equals
Core/central SpO.sub.2. Another advantage lies in esophageal
temperature readings reflecting true core temperature as opposed to
axillary temperature.
[0015] Another advantage lies in fact that the esophagus is a
muscle that constricts along the feeding tube thus ensuring an
adequate electrode contact and automated reading generation,
obviating the need for caregiver intervention.
[0016] Another advantage is the measure of respiration effort and
resulting respiration by way of a differential pressure signal as
measured between the hypo pharynx and sub-diaphragmatically.
[0017] Another advantage lies in the proximity of the ECG signal
acquisition to the cardiac muscle itself thus increasing the
relative signal magnitude detected as compared to surface
electrodes.
[0018] Another advantage lies in continuous real time data
detection.
[0019] Another advantage is that the neonate or the neonate's
environment does not need to be disturbed to take readings.
[0020] Another advantage lies in the elimination of adhesive
electrodes associated with neonatal care.
[0021] Another advantage lies in compatibility with existing
monitoring equipment.
[0022] Another advantage lies in the ability to manually and/or
automatically correct tube positioning based on a plurality of
signals detected through ECG, Temperature differential and pressure
differential detected during the insertion process.
[0023] Still further advantages of the present invention will be
appreciated to those of ordinary skill in the art upon reading and
understanding the following detailed description.
[0024] The invention may take form in various components and
arrangements of components, and in various steps and arrangements
of steps. The drawings are only for purposes of illustrating the
preferred embodiments and are not to be construed as limiting the
invention.
[0025] FIG. 1 depicts a neonatal feeding tube with instrumentation,
in accordance with the present application;
[0026] FIG. 2 is a cross sectional view of the feeding tube of FIG.
1 through a distal portion;
[0027] FIG. 3 is a cross sectional view of the feeding tube of FIG.
1 through a thermistor;
[0028] FIG. 4 is a cross sectional view of the feeding tube of FIG.
1 through an electrode;
[0029] FIG. 5 is a cross sectional view of the feeding tube of FIG.
1 through a proximal portion.
[0030] With reference to FIG. 1, a neonatal feeding tube 10 is
depicted. In one embodiment, the tube 10 is an instrumented
disposable feeding tube for newborn infants (neonates) who have not
yet developed their sucking capabilities, or who are unable to feed
normally for some other reason. The tube 10 is a 5 French tube, or
1.67 mm in diameter, in one embodiment. Appropriate scaling can be
performed for larger or smaller tubes. For convenience, the tube 10
is shown segmented, though its actual size is approximately 300 mm
in length, for example.
[0031] The neonates are fed formula or breast milk through the tube
10. The tube 10 is typically inserted into the nose or mouth and
advanced into the esophagus, and into the stomach. Like a standard
feeding tube, there is a tip 12 at the distal end of the tube. FIG.
2 depicts a cross sectional view of the distal portion 14. A hole
16 in the tip 12 permits food, such as infant formula or breast
milk, to exit the tube. One or more additional holes 18, offset
from the tip 12, allow feeding to exit in the event that the end
hole 16 becomes clogged or otherwise blocked. The tip 12 and cross
holes 18 are preferably located in the subject's stomach in one
embodiment. The distal portion 14 is molded of a soft,
biocompatible material, such as (in one embodiment) silicone
rubber.
[0032] The feeding tube 10 also includes electrodes 20. The
electrodes 20 are on an outside of the feeding tube and, when
inserted, make contact with the subject's esophagus. Insulated
leads extend proximally from each electrode, either inside the
feeding tube 10 or the outer wall of the feeding tube. A thermistor
22 is inside the tube for taking temperature measurements and, in
one embodiment, lies distal to the electrodes 20. FIG. 3 shows a
cross section of the tube 10 including the thermistor 22 in
cross-section.
[0033] The thermistor 22 is assembled to a pair of wires, at least
one insulated. In one embodiment, the thermistor 22 is calibrated
to meet the requirements of a specific patient monitor or series of
monitors. Calibration is checked. Resistance is measured and
compared to the specification. Resistance is then increased if
necessary until the thermistor resistance meets specification. This
process brings the thermistor in compliance with appropriate
standards for accuracy. The thermistor 22 may be one piece of
semiconductor material or it may be two or more segments connected
in parallel, with a small gap between each segment. This allows the
assembly to flex in two directions and to twist, even if the length
is several multiples of the tube diameter. This is important,
because the overall resistance of the thermistor is proportional to
its thickness and inversely proportional to the area. Because the
width of the thermistor and thickness of the thermistor are
constrained by the size of the tube 10, the effective length of the
thermistor assembly needs to be selected based on the electrical
requirements of the monitoring system, without further constraint
This method of construction also minimizes difficulty and
discomfort during insertion, removal, and use. It is also more
flexible and more resistant to breakage during manufacture,
insertion, and use. In one embodiment, the thermistor 22 has a
resistance of approximately 2250.OMEGA. at 25.degree. C. and
approximately 1360.OMEGA. at 37.degree. C.
[0034] In a single-thermistor embodiment, the thermistor 22 is
preferably located in the esophagus to accurately measure core
temperature, rather than the stomach or pharynx, where readings
would be less accurate. Placement in the stomach is undesirable due
to the corrosive effects of gastric fluids and the inaccuracy that
might be caused by air or food in the stomach. Whether the
thermistor is located distal to the electrodes, proximal to them,
or among them is determined by practical design issues and patient
size. However, Dual lumen with at least 1 thermistor in the
hypopharynx and can provide respiration measurement.
[0035] Proximal to the electrodes 20 is a nasopharyngeal section 26
of the feeding tube 10. The nasopharyngeal section 26, as the name
indicates, lies inside the pharynx and nose when inserted. This
section is smooth and small in diameter to avoid irritating the
subject or interfering with air flow during breathing. In an
alternate embodiment, however, it has a non-circular shape and/or
concave flutes to reduce the possibility of complete blockage of a
nare. In yet another embodiment, a hypopharynx thermistor 28 and an
oropharynx thermistor 30 are included in the nasopharyngeal section
26. The thermistors 28, 30 are used to measure respiration flow, in
addition the distal or caudal thermistor provides a core
temperature measurement. The respiration flow is measured as a
relative temperature change between the oropharynx thermistor 30
and the hypopharynx thermistor 28. An array of these thermistor
pairs may accommodate variations of patient sizes.
[0036] A pressure differential .DELTA.P is measured by a pressure
gradient between a sub-diaphragmatic (or caudal) port 32 and a
supra-diaphragmatic (or cephalic) port 34. AP represents the
respiration effort of the subject. Flow can be measured separately
(with thermistors 28 and 30), as an airway obstruction may produce
increased effort but no .DELTA.P. Respiration flow and respiration
effort are measured separately and can differ. For example, in the
case of an airway obstruction, effort will increase but flow will
decrease. The measured flow can be cross-checked against .DELTA.P
for accuracy, and can signal an alarm if the two do not
coincide.
[0037] Proximal to the supra-diaphragmatic pressure port 34 are two
fiber optic window 35. The fiber optic windows are polished ends of
many fiber optic strands. At the proximal end of the feeding tube
the fiber optic strands separate into a source fiber (run from a
light source, not shown) and a return fiber. Both fiber bundles run
down the tube 10 to the fiber optic windows 35. One fiber optic
bundle in esophagus and another at the distal tip of the feeding
tube. The distal fiber bundle does not need to be separated into a
sending and receiving bundle as it is used only to send light down
which would emanate from the small patient due to the thin
membranes and relatively translucent nature of the skin. This tip
light is used for placement verification by energizing the fibers
from an external light source and in a darkened room and
visualizing the location of the light emanating from the patient's
abdomen (if properly placed) or thorax (if not properly placed).
The pulse of the subject is measured by reflectance
photo-plethysmogram through the fiber optic window using
traditional reflectance pulse oximetry techniques. Core SpO.sub.2
is also measured at the fiber optic window 35. The
supra-diaphragmatic port 34 serves as a flush location to clean the
fiber optic window 35 as needed.
[0038] With reference now to FIG. 4, and continuing reference to
FIGS. 1-3, a possible method of manufacture is disclosed. In one
embodiment, there are four feeding lumens 36. In a three-electrode
embodiment, three of the four lumens 36 carry a contact for an
electrode 20, and one lumen 36 does not. In a four-electrode
embodiment, each of the four lumens 36 can carry a contact for an
electrode 20. In a five-electrode embodiment, three of the four
lumens 36 carry one contact while the fourth lumen 36 carries two
contacts. Fewer or additional electrodes 20 can be positioned
appropriately following the same pattern.
[0039] The lumens 36 are cut to length. At the appropriate location
for each electrode 20, an un-insulated end of a wire is secured. In
one embodiment, the wire is electrically and mechanically connected
to a metal fitting 38 by soldering, welding, bonding with a
conductive adhesive, crimping, or the like. The fitting 38 is then
attached to the lumen 36 in the appropriate position, either by
swaging, crimping, adhesive, or the like.
[0040] The lumen 36 and the thermistors 22, 24, 28, 30 are placed
together with the thermistors 22, 24, 28, 30 and wires 40 in the
center of the lumens 36, as depicted in FIG. 3. The distal portion
14 is brought together with the lumens 36 and thermistors 22, 24,
28, 30, held in place, and a jacket 42 is applied by extrusion,
heat-shrinking, tape wrapping, or the like. The lumens 36 may
reshape somewhat during this process, but this is inconsequential
to the operation of the feeding tube 10. The wires 40 are
preferably located in the center of the tube 10 for maximum
flexibility. If additional bond strength is needed, a mechanical
strength member (wire or fiber) can be added to the distal portion
14 and secured to the wires 40. A gap 44 between the distal portion
14 and a proximal portion 46 inside the jacket 42 serves as a
blending area for flow from the multiple lumen 36 to blend and
enter the distal part 14 and flow out the holes 16, 18 into the
subject's stomach.
[0041] Next, the electrodes 20 are added. The jacket 42 is removed
in the area of the electrode 20, as shown in FIG. 4. A conductive
transition 48 such as a conductive adhesive, spring-like device, or
the like is placed in the resulting removed area. An electrode 20,
in the form of a short thin-wall cylinder, is placed over each
conductive transition 48 and is then swaged to lock it in place.
The proximal and distal edges are then bent into the jacket 42 to
provide a smooth surface to reduce risk of injury to the
patient.
[0042] An outside portion 50 of the tube 10 lies outside of the
subject when the tube 10 is inserted. The outside portion 50 may
have a larger cross section. The wires 40 that run from the
components within the tube 10 terminate in a tube-side connector
52. A feeding lumen extension 54 may pass through the approximate
center of the tube-side connector 52 and terminates in an oral
style fitting 56 that permits baby formula or breast milk to be
injected by syringe, drip, pump, or other means. In one embodiment,
the fitting 56 is marked or physically differentiated to
distinguish it from ports meant for vascular injection.
[0043] Mating with the tube-side connector 52 is a cable-side
connector 58. In one embodiment, the cable-side connector 58 has a
slot (not shown) that allows the cable-side connector 58 to be
connected or disconnected without disturbing the feeding tube lumen
extension 54. After passing through a flex relief section 60,
external electrical wires 62 continue to a monitor. The external
wires 62 may be fitted with an adapter that allows interface to
various makes or models of patient monitors.
[0044] The outside portion 50, tube-side connector 52, feeding
connector 56 and lumen extension 54 are secured using conventional
insert molding, over-molding, and bonding techniques. An
over-molded or assembled tube-side connector 52 mates with the
cable-side connector 58 on the external wiring 62. The multiple
feeding lumens 36 transition into a single lumen in the outside
portion 50. The lumen extension 54 continues through openings in
the connector parts 52, 58. In the lumen extension 54 there are no
wires involved, and it is relatively transparent, which facilitates
visual confirmation of flow. The lumen extension 54 is also
flexible. If a caregiver needs to interrupt flow by pinching off
the lumen, it should be done at the lumen extension 54. Once
assembled, the feeding tube 10 is ready to be sterilized and
packaged.
[0045] Typically, only three electrodes are required for ECG
readings. For small neonates, the distal three electrodes 20 are
used. For medium neonates, the middle three electrodes 20 are used.
For larger neonates, the proximal three electrodes 20 are used. In
one embodiment, the electrodes are selected manually based on the
size of the neonate, and the judgment of the caregiver. The setting
can be selected by the caregiver by temporarily disconnecting the
connector, rotating the cable-side part 58 relative to the
connector 52, and then re-connecting, thereby changing which
internal contacts are used. In another embodiment, the electrodes
are selected by the monitor. Once the tube is inserted, all
electrodes 20 send signals to the monitor. The monitor displays
multiple wave-forms, and the operator selects the clearest display.
In other embodiments, all signals are recorded or the monitor
automatically chooses the best electrodes.
[0046] It should be noted here that respiration rate can be
determined by injecting a low-voltage electrical signal into the
patient via a pair of spaced ECG electrodes. The electrical
impedance of the connection varies during the act of respiration,
so the rate and depth of respiration can be deduced. In some
embodiments of this invention, the respiration rate is derived from
a choice of electrodes selected from the array of available
electrodes.
[0047] In an alternate embodiment a U-shaped connector on the
monitor side is used so that the feeding tube 10 can be in the
center, with mating in the axial direction. The U-shape allows the
electrical connection and the feeding connection to be made or
disconnected in any sequence, without mutual interference.
[0048] In another alternate embodiment, a connector is on the side
of the feeding tube, with mating in the radial or oblique
direction.
[0049] In another alternate embodiment, the tube 10 has a
rectangular (linear) connector rather than a circular or U-shaped
connector. In this embodiment, the feeding tube side would have a
number of sockets (pins) equal to the number of electrodes, while
the cable side would have a number of pins equal to the number of
electrodes used by the monitor. The cable could then be plugged in
to the feeding tube 10 in a number of locations, thereby selecting
which electrodes are operative.
[0050] In another alternate embodiment, the tube 10 has a connector
where the selection of the electrodes is performed by a switching
device inside the cable-side connector 58, or the cable 62
itself.
[0051] In another alternate embodiment, the tube 10 has a connector
with a rotating collar or other device which could be locked into
place to assure that the connector, after disconnection, can only
be re-connected in the selected position.
[0052] In another alternate embodiment, the tube 10 has a slide or
rotary switch on the connector to allow the caregiver to manually
select the electrodes with the strongest signal as shown on a
monitor display.
[0053] Placing the tube properly can be problematic in some
instances. The tube is to be inserted to a depth that places the
tip 12 of the tube 10 in the stomach of the neonate. It is
undesirable to insert the tube too far, into the duodenum, and it
is also undesirable to leave it short, such that the openings 16
& 18 are in the esophagus. With reference again to FIG. 1, a
distal electrode 64 on the tip 12 of the tube 10 is included to
facilitate placement confirmation. While the distal electrode 64
remains in the esophagus, contact with the wall of the esophagus
produces electrical continuity. However, when this electrode passes
through the esophageal sphincter into the larger opening of the
stomach, conductivity disappears. Because the relative location of
the electrode 64 and the openings 18 is established by the detailed
design of the device, the location of the openings 18 is now known
to the clinician relative to the beginning of the patient's
stomach.
[0054] In conjunction with the electrode 64, a light source 66 can
be used to judge the position of the tip 12 as it is passed down
the subject's esophagus. The neonate's chest is relatively thin and
translucent. The light source 66, if bright enough, can be seen
through the neonate's chest, and the caregiver can visually verify
the position of the tip 12. The light source 66 may be illuminated
by a lamp outside the proximal end and an optic fiber running the
length of the tube 10. It is also contemplated that a fiber optic
camera could be located at or fiber optically connected to the tip
12 and used as a traditional endoscope to aid in positioning the
tube 10. In some embodiments, the fiber optic device is a permanent
part of the tube 10; whereas, in alternative embodiments, the fiber
optic device is inserted into a feeding lumen 36 prior to placement
in the body and removed after the tube 10 is properly placed, so
that the lumen 36 may be used for feeding.
[0055] When inserting the tube 10, it is important to follow the
esophagus and not veer into the lungs. One way to tell which path
is being followed is by a temperature measurement with thermistors
at the tip 12. If different temperatures are measured with inhale
and exhale respiration, the tip is in an air passage. If the
temperature is constant, the tip is in the esophagus. Monitoring
pressure at the tip can be used analogously. Pressure can be
measured by sealing one of the lumens and adding a pressure
port.
[0056] Another aid in positioning the tube 10 is to include a
sensor that measures pH. If the tip 12 is properly in the stomach,
the measured pH should be acidic. If the tip 12 is in the lungs,
the measured pH will be neutral. If the tip 12 is in the esophagus,
the measured pH will be somewhat acidic, depending on reflux,
etc.
[0057] The invention has been described with reference to the
preferred embodiments. Modifications and alterations may occur to
others upon reading and understanding the preceding detailed
description. It is intended that the invention be construed as
including all such modifications and alterations insofar as they
come within the scope of the appended claims or the equivalents
thereof.
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