Enteral feeding system utilizing gastrointestinal myoelectrography

An improved system for initially positioning and for continuous or intermittent monitoring of the location of the distal end of a feeding tube in a patient's gastrointestinal tract and for selectively controlling a feeding device associated therewith by detecting and processing myoelectric signals unique to different areas of the gastrointestinal tract, such signals being detected by electrodes carried by the distal end of the feeding tube and transmitted by leads extending through the feeding tube to a monitor.

BACKGROUND OF THE INVENTION 
In many patients, gastrointestinal feeding is the preferred route of 
nutrient delivery with either the stomach or the upper portion of the 
small intestine being the two areas of major importance. Proper 
positioning of the feeding end of an enteral feeding tube in the desired 
area of the gastrointestinal tract has always been a problem. Even after 
proper positioning of the feeding end of a feeding tube in either the 
stomach or the small intestine, it is possible that the feeding end of the 
tube may unknowingly migrate from the selected area whereupon the patient 
may be subject to a risky feeding situation. A common method of initially 
positioning and then monitoring the proper positioning of the feeding end 
of such a gastrointestinal feeding tube has been by the use of X-ray. To 
repeatedly verify proper placement in this manner is not only cumbersome 
and expensive, but it also subjects the patient to unnecessary X-ray 
exposure. 
One attempt to improve this situation is disclosed in U.S. Pat. No. 
4,381,011 to Somers, dated April 26, 1983, wherein the pH or acidity of 
certain portions of a gastrointestinal tract are monitored by a pH 
measuring device positioned on the end of a feeding tube. However, as the 
pH may vary as the feeding process proceeds and may also be affected by 
extraneous factors, the monitored results may be seriously deficient as to 
the desired accuracy thereof. X-rays, etc. would probably be necessary for 
back-up purposes. 
Further as to Somers and applicants' disclosure herein, the basic functions 
of the gastrointestinal system, the primary organs being the esophagus, 
the stomach, and the small intestine, are to mechanically transport 
foodstuff, chemically break down complex food ingredients, and to absorb 
processed foodstuff into the blood. Each of the noted primary organs 
possesses a muscle coat which contracts and propels the foodstuff along 
the system (peristalsis). This muscle contraction is controlled by nerve 
tissue via the movement of calcium and other ions from inside the cell to 
outside the cell and vice versa. This effect begins at a specific 
anatomical region called a pacemaker and propagates through the muscle 
mass of that organ. A complete cycle consists of depolarization, 
hyperpolarization and repolarization of the cell wall. The ion 
concentrations undergo increases and decreases during the cycle with each 
of the foregoing organs being characterized by its own cyclic frequency. 
This ion movement causes a chemical interaction at the surface of 
applicants' feeding tube electrodes whereby electrical potentials are 
created, voltage being the unit of measure for the difference between the 
two sources of electrical potential, applicants' electrodes. Applicants' 
feeding tube electrodes therefore detect any cyclic change in electrical 
voltage at their location in a patient's gastrointestinal tract. 
Somers, on the other hand, depends on the digestive activities in the 
stomach where foodstuff is chemically broken down by pepsin and 
hydrochloric acid. The acid is produced in the stomach which is, 
therefore, normally a zone of high acid concentration relative to the 
esophagus and the small intestine due to the esophageal and pyloric 
sphincters at the entrance to and exit from the stomach, respectively. 
Acidity is measured in pH units which is the concentration of the hydrogen 
ion. Thus, a pH electrode undergoes a reaction which is dependent on the 
concentration of hydrogen ions adjacent thereto, which reaction produces 
an electrical potential. However, in pH systems the second potential 
source needed to measure a voltage must be provided by a reference 
electrode. It is obvious, therefore, that the pH system of Somers is 
affected to a much greater degree by gastrointestinal contents than is 
applicants' myoelectrography system disclosed herein, which 
myoelectrography system thus provides much more accurate results. 
SUMMARY OF THE INVENTION 
The present invention is directed to an apparatus which aids in initially 
positioning a feeding tube in a desired location in a patient's 
gastrointestinal tract and which provides continuous assurance that 
nutrients are being delivered into that preselected area. This apparatus 
thus provides a new advanced level of clinical patient care. If an 
automatic feeding system, such as a pump or a flow-regulating clamp, is 
operably connected to the feeding tube of the present invention, any 
migratory movement of the feeding end thereof out of its desired position 
in the gastrointestinal tract is automatically detected and monitored, 
whereupon the feeding system is automatically shut down until the feeding 
end of the feeding tube has been repositioned to its proper location in 
the patient's gastrointestinal tract. 
It has been determined that different areas of a human being's anatomy 
including the gastrointestinal tract are characterized by electrical 
signals of different frequencies generated by muscle activity at such 
areas, such muscle-generated signals being known as myoelectric signals. 
For instance, in normal human beings, it is known that myoelectric signals 
originate in the stomach area at a rate of three per minute and in the 
duodenum of the small intestine at a rate of eleven per minute. Other 
areas of the gastrointestinal tract, such as the esophagus, the 
distal-most post-pyloric portion of the small intestine, and the colon, 
would produce different frequency signals. Continuous detection and 
monitoring of these myoelectric depolarization signals at the distal 
feeding end of a feeding tube, a technology known as gastrointestinal 
myoelectrography, provides immediate notification of changes in the 
positioning thereof. Further, gastrointestinal myoelectrography may be 
able to determine changes in the functioning of any of these areas of the 
gastrointestinal tract by detecting minor variations in the aforesaid 
depolarization signal frequencies, for instance, to automatically 
determine and control the rate of operation of a feeding system and also 
to automatically introduce suitable selected nutrients; to automatically 
monitor post-surgical patients for return of gastrointestinal motility; 
and/or to differentiate between absorption disorders and rhythm disorders 
during diagnostic procedures. 
The present invention is directed to a feeding tube which is provided at 
its distal end, the feeding end thereof, with one or more electrodes which 
detect such myoelectric signals. The invention may also be characterized 
by an amplifier/filter module to which the detected signals are fed, by a 
monitor which receives the signals from the module, and by a feeding 
system which may be controlled by the monitor. 
An object of the present invention is to provide a new and improved system 
for initially positioning and then monitoring the position of a feeding 
tube in a patient's gastrointestinal tract by detecting and monitoring 
myoelectric signals generated therein, which signals may also be used to 
control an enteral nutrient feeding system. 
Another object of the present invention is to provide a new and improved 
feeding tube of the type having a bolus at its distal end and a 
Y-connector at its outer end, wherein the bolus has one or more spaced 
apart electrodes provided thereon with leads from the electrodes passing 
through the feeding tube to a monitor.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, two possible forms of a gastrointestinal 
locating/feeding system 10 embodying the invention for the feeding of 
liquid nutrients into preselected areas of the gastrointestinal tract are 
shown in FIG. 1. The system 10 includes an elongated, flexible, feeding 
tube 12,12a having a suitable Y-connector 14,14a provided on its proximal 
end and a bolus 16,16a provided at its distal feeding end, which bolus 
16,16a is provided with voltage-sensing (myoelectric signals) electrodes 
18' and 18" (FIGS. 2 and 4); a module 20 for amplifying the detected 
myoelectric signals and for filtering out undesired frequencies; a monitor 
22 capable of processing the detected signals; and, in certain instances, 
a controllable feeding device 24 such as an infusion pump or a 
flow-regulating clamp. 
Two of several possible forms of the system 10 are illustrated in FIG. 1. A 
nasal-enteral feeding arrangement into the upper portion or duodenum 26 of 
a patient's small intestine 28, as shown in full line, is characterized by 
the feeding tube 12 which extends through the patient's esophagus 30 and 
through the patient's stomach 32 with the bolus 16 being positioned in the 
patient's duodenum 26. The Y-connector 14 is provided on the proximal end 
of the feeding tube 12 and sheathed leads 34' and 34", which are connected 
to the electrodes 18' and 18" by a connector 19' and by a connector for 
lead 34" which is not visible in FIG. 2, extend through the feeding tube 
12 (FIGS. 2 and 3) and out of the Y-connector 14 through an arm 36 thereof 
for connection to the amplifier/filter module 20. As is best shown in FIG. 
5, a separate passage or lumen 60 may be provided in the feeding tube 
12,12a for the electrode leads 34' and 34". An abdominal stoma feeding 
arrangement passing transcutaneously into the patient's stomach 32, as 
shown in broken line in FIG. 1, is characterized by the feeding tube 12a 
which extends through a stoma 46 provided in the abdominal wall 48 with 
the bolus 16a being positioned in the stomach 32. Adjustable retaining 
members 50 and 52 are provided on the feeding tube 12a at internal and 
external ends of the stoma 46, respectively, as an aid in preventing 
undesirable movement of the feeding tube 12a relative thereto. The 
Y-connector 14a is provided on the proximal end of the feeding tube 12a 
and sheathed electrode leads 34a' and 34a" extend outwardly of the 
Y-connector 12a through an arm 36a thereof for connection to the 
amplifier/filter module 20. 
Although not shown in the drawings, it is noted that the bolus 16 of the 
nasal-enteral feeding tube 12 may, if desired, be positioned in the 
stomach 32, the remaining small bowel, or the colon (not shown) if the 
myoelectric signals of these areas of a patient's gastrointestinal tract 
are to be monitored. Likewise, it is noted that the bolus 16a of the 
abdominal stoma feeding tube 12a may, if desired, be positioned in the 
duodenum 26 or even in the patient's remaining small bowel or colon. As 
illustrated in FIG. 3, there may be instances where it is desirable for 
diagnostic or treatment purposes to have a feeding tube 12 which extends 
through a patient's nasal passage 62 and which has three spaced electrode 
means provided thereon, an esophageal electrode means 64, a stomach 
electrode means 66, and a small bowel electrode means 68. 
The amplifier/filter module 20, which filters out all frequencies outside 
the range of physiological interest as well as 60 hertz noise, will 
amplify the detected signal to a magnitude acceptable to the monitor 22 
and will also provide impedance matching between the feeding tube 
electrodes 18' and 18" and the monitor 22. The module 20 is suitably 
connected to the monitor 22, as at 38 and the monitor 22 may be suitably 
connected to the feeding device 24, as at 40. The monitor 22 is an 
electronic device which is adapted to process the detected 
electrophysiological or myoelectric signals received from the module 20 in 
such a way that the unique properties of the various segments of the 
enteral tract's electrical activity can be readily identified. Once the 
parameters of the signals are determined, they may be compared to selected 
standards by the programming of the monitor 22. The monitor program will 
also contain a logic path such that the results of the comparison may be 
used to control the feeding device 24 whereby the feeding device 24 may be 
directed to maintain its current feeding rate setting or to 
increase/decrease the rate of nutrient feeding or even to select a 
different nutrient. This unique system 10 thus provides a solution to the 
problem of overloading a patient's gastrointestinal tract. Feeding is 
normally started at a low rate of infusion which is periodically increased 
until the patient's nutrient needs are met or the patient exhibits 
discomfort or other symptoms. However, this system 10 allows digestive 
problems to be recognized and prevented by regulating the rate of feeding 
prior to gastric overload and the onset of more harmful physical symptoms 
such as cramps, nausea, vomiting, diarrhea. gastric reflux, or aspiration 
pneumonia. The feeding device 24 may be connected to another arm 42,42a of 
the Y-connector 14,14a by a tube set 44,44a. 
Another major problem of gastrointestinal feeding is that of initially 
positioning the feeding end of the tube 12,12a the bolus 16,16a at the 
desired location in the gastrointestinal tract during the intubation 
process and later verifying that the proper placement still exists. Past 
and current practice is to use X-rays, aspiration, and ascultation to 
locate the bolus, all of which have serious drawbacks. The present system 
10 provides a direct, continuous, and reliable method of overcoming this 
problem as the monitor 22 may be programmed to not only regulate a feeding 
rate but also to sound an alarm or otherwise alert an observer while it 
may also simultaneously cease the feeding should the bolus 16,16a migrate 
away from its proper feeding position or if a malady such as dysrhythmia 
occurs. The monitor 22 may also possess display and storage devices such 
as a CRT display, a chart recorder and/or a magnetic tape recorder, 
whereby to provide a record of the detected signals. 
With reference to FIGS. 2 and 4, it is noted that the electrodes 18' and 
18" of the preferred embodiment are in the form of coils of fine metal 
wire wrapped around the bolus 16 in spaced-apart relationship and adjacent 
to nutrient exit ports 54 and 56 provided in the bolus 16. The metal wire 
for the electrodes 18' and 18" should have good electrical conductivity 
such as is provided by gold, silver and platinum wire, for instance. 
Another suitable wound-coil electrode would be a silver/silver chloride 
electrode formed of silver wire coated with a chloride salt of silver. The 
wound coil configuration presents a conducting surface all around the 
circumference of the bolus 16 while maintaining flexibility in that the 
individual coils can deform and deflect in conformance with changes in the 
shape of the bolus 16, as during the intubation process. 
However, it is noted that many other forms of electrodes besides wound-coil 
electrodes may be used in the gastrointestinal locating/feeding system 10 
of the present invention. 
The multiple lumen feeding tube arrangement, as is best illustrated in 
FIGS. 4 and 5, provides means for detecting myoelectric signals in desired 
locations in a patient's gastrointestinal tract while simultaneously 
introducing liquid nutrients at the site of detection. Two pathways are 
provided in the tube 12, a fluid channel 58 communicating throughout the 
length of the tube 12 and providing a means for the liquid nutrient to 
move from its source, the feeding device 24, to the bolus nutrient exit 
ports 54 and 56 and a separate channel or lumen 60 separate from the fluid 
path 58 but still inside the tube 12 and providing a means for electrical 
communication between the electrodes 18' and 18" and the module 20 by 
passage of the sheathed leads 34' and 34" therethrough. 
While there has been shown and described several possible embodiments of 
the invention, it will be obvious to those skilled in the art that changes 
and modifications may be made without departing from the invention, and it 
is intended by the appended claims to cover all such changes and 
modifications as fall within the true spirit and scope of the invention.