U.S. patent application number 10/687298 was filed with the patent office on 2004-08-12 for implantable monitoring probe.
This patent application is currently assigned to Endonetics, Inc.. Invention is credited to Johnson, George M., Kilcoyne, John T., Klecher, Christopher, Tsukashima, Ross.
Application Number | 20040158138 10/687298 |
Document ID | / |
Family ID | 26964569 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040158138 |
Kind Code |
A1 |
Kilcoyne, John T. ; et
al. |
August 12, 2004 |
Implantable monitoring probe
Abstract
Disclosed is an ambulatory system for monitoring one or more
physiological parameters in a body lumen, such as the esophagus.
The system includes an implantable probe having a sensor for the
physiological parameter and a transmitter for transmitting data to
an external receiver. The probe may be used for monitoring any of
various physiological parameters, including pH, temperature, and
pressure, within the esophagus or other body lumens. Methods and
deployment catheters are also disclosed.
Inventors: |
Kilcoyne, John T.; (San
Diego, CA) ; Tsukashima, Ross; (San Diego, CA)
; Johnson, George M.; (Santa Ana, CA) ; Klecher,
Christopher; (San Diego, CA) |
Correspondence
Address: |
SHUMAKER & SIEFFERT, P. A.
8425 SEASONS PARKWAY
SUITE 105
ST. PAUL
MN
55125
US
|
Assignee: |
Endonetics, Inc.
|
Family ID: |
26964569 |
Appl. No.: |
10/687298 |
Filed: |
October 16, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10687298 |
Oct 16, 2003 |
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09544373 |
Apr 6, 2000 |
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6689056 |
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09544373 |
Apr 6, 2000 |
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09287617 |
Apr 7, 1999 |
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6285897 |
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Current U.S.
Class: |
600/350 ;
600/361 |
Current CPC
Class: |
A61B 1/00148 20220201;
A61B 5/0008 20130101; A61B 5/14546 20130101; A61B 5/4233 20130101;
A61B 1/00147 20130101; A61B 5/6882 20130101; A61B 5/14539 20130101;
A61B 5/0031 20130101; A61B 5/037 20130101; A61B 5/073 20130101;
A61B 5/14532 20130101; A61B 5/42 20130101; A61B 1/041 20130101 |
Class at
Publication: |
600/350 ;
600/361 |
International
Class: |
A61B 005/05 |
Claims
What is claimed is:
1. A method of attaching a device to a tissue surface inside of a
patient, comprising the steps of: providing a device having a
housing, a concavity on the housing, a window to permit
visualization through the housing of the interior of the concavity,
and a pin which is axially movable from a retracted position within
the housing to an extended position which extends at least part way
across the concavity; carrying the device on an introduction
instrument into the body; positioning the device at an attachment
site in the body such that the concavity is adjacent the tissue
surface at the attachment site; drawing tissue into the concavity;
visualizing tissue within the concavity through the window, and
advancing the pin through the tissue to retain the device at the
attachment site.
2. A method of attaching a device to a tissue surface inside of a
patient as in claim 1, wherein the device further comprises a lumen
in communication with the concavity, and the drawing tissue into
the concavity step additionally comprises the step of applying
suction to the lumen.
3. A method of attaching a device to a tissue surface inside of a
patient as in claim 1, wherein the window comprises a transparent
wall on the housing, and said visualizing tissue step comprises
observing tissue through the wall of the housing.
4. A method of attaching a device to a tissue surface inside of a
patient as in claim 1, wherein the carrying the device on an
introduction instrument step comprises carrying the device by an
endoscope.
5. A method of attaching a device to a tissue surface inside of a
patient as in claim 1, wherein the pin comprises a material which
degrades at the attachment site, and the method further comprises
the step of permitting the pin to degrade, thereby releasing the
device from the tissue surface.
6. A method of attaching a device to a tissue surface inside of a
patient, comprising the steps of: providing a device having a
housing, a concavity on the housing, and a pin which is axially
movable from a retracted position within the housing to an extended
position which extends at least part way across the concavity;
carrying the device on an introduction instrument into the body;
positioning the device at an attachment site in the body such that
the concavity is adjacent the tissue surface at the attachment
site; drawing tissue into the concavity; and advancing the pin
through the tissue to retain the device at the attachment site.
7. A method of attaching a device to a tissue surface inside of a
patient as in claim 6, wherein the device further comprises a lumen
in communication with the concavity, and the drawing tissue into
the concavity step additionally comprises the step of applying
suction to the lumen.
8. A method of attaching a device to a tissue surface inside of a
patient as in claim 6, wherein the carrying the device on an
introduction instrument step comprises carrying the device on an
endoscope.
9. A method of attaching a device to a tissue surface in side of a
patient as in claim 6, wherein the pin comprises a material which
degrades at the attachment site, and the method further comprises
the step of permitting the pin to degrade, thereby releasing the
device from the tissue surface.
10. A monitoring device for monitoring at least one physiological
parameter at an attachment site in a body, comprising: a housing,
having a tissue attachment surface; a pin which is movable from a
retracted position to allow the tissue attachment surface to be
brought into contact with tissue at a preselected attachment site,
and an extended position in which it extends through tissue in
contact with the attachment surface; and at least one physiological
parameter detector carried by the housing.
11. A monitoring device as in claim 10, further comprising a
concavity on the housing such that the tissue attachment surface is
on a surface of the concavity.
12. A monitoring device as in claim 10, wherein the pin comprises a
bioabsorbable material.
13. A monitoring device as in claim 11, further comprising a lumen
in communication with the concavity, for connection to a vacuum to
draw tissue into the concavity.
14. A monitoring device as in claim 10, wherein the physiological
parameter detector comprises a pH detector.
15. A monitoring device as in claim 10, further comprising an RF
transmitter for transmitting data generated by the physiological
parameter detector.
16. A monitoring device as in claim 10, further comprising an
electrical contact for contacting tissue in the body and
transmitting data relating to the physiological parameter through
the tissue.
17. A method of remotely monitoring a physiological parameter in a
body lumen of a patient, comprising the steps of: providing a
device having a housing, a physiological parameter detector in the
housing, a concavity on the housing, and a pin which is axially
movable from a retracted position within the housing to an extended
position which extends at least part way across the concavity;
carrying the device on an introduction instrument into the body;
positioning the device at an attachment site in the body such that
the concavity is adjacent the tissue surface at the attachment
site; drawing tissue into the concavity; advancing the pin through
the tissue to retain the device at the attachment site; and
monitoring at least one physiological parameter.
18. A method as in claim 17, wherein the attachment site is the
surface of the esophagus.
19. A method as in claim 17, wherein the device further comprises a
radiofrequency transmitter, and said physiological parameter data
transduced by the detector is transmitted to a radiofrequency
receiver and a recording device located outside the patient's
body.
20. A method as in claim 17, wherein the device further comprises a
microprocessor.
21. A method as in claim 17, wherein the device further comprises a
digital recorder that records physiological parameter data.
22. A method as in claim 21, further comprising the step of
transferring the physiological parameter data from the digital
recorder to an external data retrieval device.
23. A method as in claim 17, wherein the physiological parameter is
selected from the group consisting of pH, temperature, and
pressure.
24. A method as in claim 23, wherein the physiological parameter
data comprises data concerning at least two of said parameters.
25. A method as in claim 23, wherein the physiological parameter
data comprises data concerning all three of said parameters.
26. A method as in claim 17, wherein the physiological parameter
comprises the concentration of ions within a body fluid.
27. A method as in claim 26, wherein the ions are selected from the
group consisting of sodium, potassium, calcium, magnesium,
chloride, bicarbonate, and phosphate.
28. A method as in claim 17, wherein the physiological parameter
comprises the concentration of a solute within a body fluid.
29. A method as in claim 28, wherein the solute is selected from
the group consisting of glucose, bilirubin, creatinine, blood urea
nitrogen, urinary nitrogen, renin, and angiotensin.
30. A method as in claim 17, further comprising the step of using a
computer and a computer software program to analyze physiological
parameter data obtained over a period of time.
31. A method as in claim 30, wherein the pin used for attaching
said monitor to the lumen wall is made at least partially of
dissolvable materials.
32. A monitoring device for monitoring at least one physiological
parameter at an attachment site in a body, comprising: a housing,
having a tissue attachment surface; a pin which is movable from a
retracted position to allow the tissue attachment surface to be
brought into contact with tissue at a preselected attachment site,
and an extended position in which it extends through tissue in
contact with the attachment surface; and at least one physiological
parameter detector carried by the housing.
33. An implantable device for measuring at least one physiological
parameter indicative of gastroesophageal reflux, the device
comprising: a casing adapted to be implanted and secured within the
body of the patient in a location wherein the surrounding
environment provides the at least one physiological parameter
indicative of gastroesophagael reflux; a sensor, positioned within
the casing, the is adapted to measure the at least one
physiological parameter indicative of gastroesophageal reflux; a
transmitter, positioned within the casing, wherein the transmitter
is adapted to send a parameter signal indicative of the measured at
least one physiological parameter to a receiver located outside of
the body of the patient; a power source, positioned within the
casing, that provides power to the sensor and the transmitter; a
processor, positioned within the casing, that periodically induces
the sensor to obtain the at least one physiological parameter and
periodically induces the transmitter to transmit a parameter signal
indicative of the at least one physiological parameter, wherein the
processor enables the delivery of power from the power source to
the sensor during a first time interval during each measurement
cycle when the sensor is sensing the at least one physiological
parameter and wherein the processor enables the delivery of power
from the power source to the transmitter during a second time
interval during each measurement cycle when the transmitter is
transmitting the parameter signal so that consumption of power by
the sensor and the transmitter is reduced during intervals of each
cycle other than the first and second interval respectively.
34. The implantable device of claim 33, wherein the sensor is
comprised of a pH sensor that measures the pH of the fluid
surrounding the casing when the casing is implanted in the
patient's body.
35. The implantable device of claim 34, wherein the sensor is
comprised of an ISFET transistor with an associated amplifier
wherein the ISFET transistor is selectively activated in response
to the pH of the fluid surrounding the casing such that the ISFET
and the associated amplifier can provide a voltage signal to the
microprocessor that is indicative of the pH of the surrounding
fluid.
36. The implantable device of claim 34, wherein the sensor is
comprised of an antimony electrode with an associated amplifier
wherein the antimony electrode is selectively activated in response
to the pH of the fluid surrounding the casing such that the
antimony electrode and the associated amplifier can provide a
voltage signal to the microprocessor that is indicative of the pH
of the surrounding fluid.
37. The implantable device of claim 33, wherein the transmitter is
comprised of an RF transmitter that transmits a digital signal
indicative of the physiological parameter indicative of
gastroesophageal reflux.
38. The implantable device of claim 33, wherein the processor
initiates a measurement cycle wherein the sensor senses the
physiological parameter and the transmitter transmits a parameter
signal corresponding to the physiological parameter measured by the
sensor approximately every 6 seconds.
39. The implantable device of claim 38, wherein the processor
provides power to the sensor only during the first interval and
provides power to the transmitter only during the second interval
of the cycle so as to reduce power consumption during each
cycle.
40. The implantable device of claim 39, wherein the first interval
is approximately 20 ms in length and the second interval is
approximately 60 ms in length.
41. The implantable device of claim 33, further comprising a
non-volatile memory accessible by the processor, wherein the
processor is adapted so that calibration information can be stored
in the non-volatile memory prior to implantation of the device into
the patient.
42. The implantable device of claim 41, wherein the parameter
signals transmitted by the transmitter include the calibration data
such that the receiver external to the patient receives a
calibrated signal indicative of the physiological parameter
indicative of gastroesophageal reflux.
43. A method of measuring a physiological parameter indicative of
gastroesophageal reflux using an implanted sensor, the method
comprising: (a) providing power to a sensor circuit for a first
time interval so as to obtain a parameter measurement indicative of
gastroesophageal reflux; (b) ceasing providing power to the sensor
circuit following the first time interval; (c) providing power to a
transmitter circuit during a second time interval, following the
first time interval so that a parameter signal indicative of the
parameter measurement obtained by the sensor circuit can be
transmitted to a receiver located outside of the body of the
patient; and (d) ceasing providing power to the transmitter circuit
following the second time interval.
44. The method of claim 43, wherein providing power to the sensor
circuit comprises providing power to an ISFET transistor that is
electrochemically activated by the pH of the fluid surrounding the
implanted sensor and that produces a voltage signal that is
proportionate to the pH of the fluid surrounding the implanted
sensor.
45. The method of 44, wherein power is provided to the sensor for
approximately 20 ms during the first time interval.
46. The method of claim 44, further comprising providing a digital
signal representative of the physiological parameter measured by
the sensor so that providing power to the transmitter circuit
results in the digital signal being transmitted to the receiver
located outside of the body of the patient.
47. The method of claim 46, wherein providing power to the
transmitter circuit during a second time interval comprises
providing power to a RF transmitter.
48. The method of claim 47, wherein power is provided to the
transmitter for approximately 60 ms during the second time
interval.
49. The method of claim 43, wherein the acts (a) and (b) are
periodically repeated every 6 seconds and steps (c) and (d) are
periodically repeated every 12 seconds.
50. A system for measuring physiological parameters in the body of
a patient indicative of gastroesophageal reflux, the system
comprising: a plurality of sensors adapted to be implanted in the
body of the patient, wherein the plurality of sensors periodically
measure a physiological parameter indicative of gastroesophageal
reflux and wherein the plurality of sensors periodically transmit a
signal indicative of the physiological parameter indicative of
gastroesophageal reflux and wherein each signal includes an
identifier indicative of the sensor from which each signal is sent;
and a receiver that receives the signals from the plurality of
transmitters and records the signals.
51. The system of claim 50, wherein each of the plurality of
sensors includes a pH monitor and an RF transmitter.
52. The system of claim 51, wherein each sensor also includes a
microprocessor that periodically receives a signal from the pH
monitor and induces the RF transmitter to periodically send an RF
signal indicative of the pH measured by the pH monitor.
53. The system of claim 52, wherein the microprocessor periodically
enables the pH monitor during a first interval of each measurement
cycle to obtain the pH signal and then disables the pH monitor
during a second interval.
54. The system of claim 53, wherein the microprocessor enables the
RF transmitter during the second interval and disables the RF
transmitter during periods of each cycle other than the second
interval and disables the pH monitor during periods of each cycle
other than the first interval.
Description
BACKGROUND OF THE INVENTION
[0001] This is a continuation in part of U.S. patent application
Ser. No. 09/287,617 filed Apr. 7, 1999.
FIELD OF THE INVENTION
[0002] The present invention relates to minimally invasive
physiological monitoring systems. More particularly, the present
invention relates to an implantable probe for monitoring one or
more parameters in the esophagus, such as pH, in connection with
the detection of gastroesophageal reflux disease.
DESCRIPTION OF THE RELATED ART
[0003] Gastroesophageal reflux is a condition in which gastric acid
refluxes, or flows in the direction opposite to the normal flow,
from the stomach into the esophagus. Frequent reflux episodes may
result in a potentially severe problem known as gastroesophageal
reflux disease (GERD). GERD is the most common cause of dyspepsia
or heartburn. GERD affects approximately 75 million adults in the
United States on at least an intermittent basis, and approximately
13 million adults on a daily basis. As a common cause of chest
pain, GERD frequently mimics the symptoms of a myocardial
infarction or severe angina pectoris, which are signs of severe
coronary artery disease. Because their treatments and outcomes are
different, distinguishing between GERD and coronary artery disease
is of paramount diagnostic importance to the patient and
physician.
[0004] The lower esophageal sphincter (LES), or valve, is composed
of a smooth muscle ring located at the gastroesophageal junction,
and it plays a key role in the pathogenesis of GERD. Factors that
cause or contribute to GERD include the following: transient
relaxation of the LES, delayed stomach emptying, and ineffective
esophageal clearance. Another cause of GERD is decreased resting
tone of the LES, which produces incompetence (incomplete closing)
of the LES.
[0005] At rest, the LES maintains a high pressure, between 10 and
30 mm Hg above intragastric pressure. Upon deglutition
(swallowing), the LES relaxes before the esophagus contracts,
allowing food to pass through into the stomach. After food passes
into the stomach, the LES contracts to prevent the stomach
contents, including gastric acid, from refluxing into the
esophagus. The mechanism of the LES contraction and relaxation is
influenced by vagus nerve innervation and hormonal control by
gastrin and possibly other gastrointestinal hormones.
[0006] Complications of GERD include esophageal erosion, esophageal
ulcer, and esophageal stricture. Stricture formation results from
scarring of the esophagus following prolonged exposure of the
esophageal mucosa to acid reflux. The most common clinical
manifestation of stricture is dysphagia (difficulty swallowing).
Unlike dysphagia from nonstrictured esophageal reflux, dysphagia
caused by stricture is a progressive disorder in that the size of a
bolus which can pass into the stomach becomes progressively
smaller. Prolonged exposure of esophageal mucosa to acid often
leads to a precancerous condition known as Barrett's esophagus.
Barrett's esophagus is characterized by the replacement of the
normal squamous epithelium that lines the esophagus with abnormal
columnar epithelium. Barrett's esophagus is clinically important
not only as a marker of severe reflux, but also as a precursor to
esophageal cancer.
[0007] Efforts have been made to define and report as reflux rapid
changes of intraesophageal pH, even while the pH remains within the
normal esophageal pH range of 4 to 7. Such pH changes, however, can
be difficult to prove to be caused by true gastroesophageal reflux,
and in some instances may not be caused by reflux.
[0008] Some have measured gastroesophageal reflux with radioisotope
techniques. With these techniques, a radiolabeled meal is fed to
the patient. With a gamma camera positioned externally on the
patient's chest or internally within the esophagus, it is possible
to detect gastroesophageal reflux containing the isotope,
regardless of pH. The use of radioactive material and the expense
of stationary or ambulatory gamma cameras make the radioisotope
method for detection of reflux unattractive.
[0009] Intestinal impedance has previously been used as a surrogate
for measurement of gastric emptying into the intestines. In such
studies, a liquid or solid meal is administered to a patient, and
changes in intestinal impedance are monitored from external
electrodes around the abdomen.
[0010] The primary and most reliable method of objectively
diagnosing GERD, however, is 24-hour measurement of pH within the
lower esophagus. The normal pH range in the esophagus is between 4
and 7. As a general rule, when gastric acid enters the esophagus
from the stomach, the intraesophageal pH drops below 4. An epoch of
one second or more during which the intraesophageal pH falls below
4 is considered a reflux event.
[0011] Certain methods and apparatus are known in the prior art for
24-hour monitoring of intraesophageal pH in patients with suspected
GERD. An example of a system for ambulatory 24-hour recording of
gastroesophageal reflux is the Digitrapper.TM. System (manufactured
by Synectics Medical AB, in Stockholm, Sweden) used with glass or
Monocrystant.TM. pH catheters (as described in U.S. Pat. No.
4,119,498) and with the analysis software EsopHogram.TM. (by
Gastrosoft, Inc. in Dallas, Tex.). These prior art systems
typically measure pH in the esophageal tract with an
intraesophageal catheter and generate reports regarding esophageal
exposure of gastric juice.
[0012] Currently, ambulatory esophageal pH monitoring is performed
by passing a pH catheter transnasally into the esophagus, to a
point approximately 5 cm above the LES. The proximal end of the
nasoesophageal catheter extends outside the patient's nose and is
usually taped down to the cheek in two places and draped over the
ear.
[0013] The use of this indwelling nasoesophageal catheter for
ambulatory pH monitoring presents a number of disadvantages. Almost
invariably, the catheter's presence is very uncomfortable to
patients, who frequently develop a sore throat and rhinorrhea
(runny nose) because of local irritation of oropharyngeal and
nasopharyngeal mucous membranes, respectively, from the catheter.
In addition, many patients are embarrassed to be seen in public
with the catheter assembly attached to their faces. Furthermore,
patients frequently experience an increased swallowing frequency
when the catheter is in place, due to reflex stimulation. This
increased swallowing introduces a significant amount of air into
the stomach, which can cause abdominal discomfort. Finally,
increased swallowing in response to the catheter's presence may
erroneously raise a patient's intraesophageal pH readings because
saliva is alkaline.
[0014] Thus, there remains a need for an ambulatory system that
avoids the use of an indwelling nasoesophageal catheter during the
assessment of esophageal pH and other physiological parameters to
detect gastroesophageal reflux.
SUMMARY OF THE INVENTION
[0015] In accordance with one aspect of the present invention,
there is provided a monitoring device (sometimes referred to herein
as a "probe") for monitoring at least one physiological parameter
at an attachment site in a body. The monitoring device comprises a
housing, having a tissue attachment surface. A pin is movable from
a retracted position to allow the tissue attachment surface to be
brought into contact with or adjacent tissue at a preselected
attachment site, and an extended position in which it extends
through tissue in contact with or adjacent to the attachment
surface. The housing carries at least one physiological parameter
detector.
[0016] In accordance with another aspect of the present invention,
there is provided a method of attaching a device to a tissue
surface inside of a patient. The method comprises the steps of
providing a device having a housing, a concavity on the housing, a
window to permit visualization through the housing of the interior
of the concavity, and a pin which is axially movable between a
retracted position and an extended position which extends at least
part way across the concavity. The device is carried on an
introduction instrument into the body, and positioned adjacent an
attachment site. Tissue is drawn into the concavity, where it may
be visualized through the window. The pin is thereafter advanced
(proximally or distally) through the tissue to retain the device at
the attachment site.
[0017] Preferably, the device further comprises a vacuum lumen in
communication with the concavity, and the drawing tissue into the
concavity step additionally comprises the step of applying suction
to the lumen. In one embodiment, the window comprises a transparent
wall on the housing, and the visualizing tissue step comprises
observing tissue and the pin through the wall of the housing. In
one embodiment, the pin comprises a material which degrades or
absorbs at the attachment site, and the method further comprises
the step of permitting the pin to degrade following a sufficient
monitoring period of time, thereby releasing the device from the
tissue surface.
[0018] In accordance with a further aspect of the present
invention, there is provided a method of attaching a device to a
tissue surface inside of a patient. The method comprises the steps
of providing a device having a housing, a concavity on the housing,
and a pin which is axially movable from a retracted position within
the housing to an extended position which extends at least part way
across the concavity. The device is carried on an introduction
instrument into the body, and positioned at an attachment site,
such that the concavity is adjacent the tissue surface at the
attachment site. Tissue is drawn into the concavity, and the pin is
advanced through the tissue to retain the device at the attachment
site.
[0019] In accordance with a further aspect of the present
invention, there is provided a monitoring device for monitoring at
least one psychological parameter at an attachment site in a body.
The device comprises a housing, having a tissue attachment surface.
A pin is movable between a retracted position to allow tissue to be
brought into contact with the tissue attachment surface, and an
extended position in which the pin extends through the tissue in
contact with the attachment surface. The housing carries at least
one physiological parameter detector. In one embodiment, the
physiological parameter detector comprises a pH detector.
[0020] Preferably, the monitoring device further comprises an RF
transmitter for transmitting data generated by the physiological
parameter detector. Alternatively, the monitoring device comprises
an electrical contact for contacting tissue in the body and
transmitting data relating to the psychological parameter through
the tissue. In one application, the physiological parameter is
selected from the group consisting of pH, temperature and pressure.
Alternatively, the physiological parameter comprises a
concentration of a preselected ion on a tissue surface or within a
body fluid. The ion is preferably selected from the group
consisting of sodium, potassium, calcium, magnesium, chloride,
bicarbonate, and phosphate. In a further aspect of the invention,
the physiological parameter comprises the concentration of a solute
within a body fluid, such as glucose, biliruben, creatinene, blood
urea nitrogen, urinary nitrogen, renin, and angiotensin.
[0021] The monitoring device in one embodiment comprises a
microprocessor and non-volatile memory. The microprocessor controls
the various functions of the monitoring device circuits. The
monitoring device sends a digital signal that is coded to contain a
variety of information. The digital message contains code to
uniquely identify the monitoring device. This allows multiple
devices to be used and inhibits erroneous or stray signal
reception. The digital message also indicates what type of
information is being sent and a corresponding data packet. The
message also includes a checksum to help insure that the data
transmission was correctly sent and received.
[0022] The monitoring device provides the ability to power itself
off and on. This feature conserves battery power and extends the
useful life of the monitoring device. The monitoring device also
powers up the microprocessor and transmitting circuit up separately
from the sensor circuit and alternates the active circuit. This
feature further minimizes power consumption and further extends the
useful life of the power supply.
[0023] Further features and advantages of the present invention
will become apparent to those of ordinary skill in the art in view
of the detailed description of preferred embodiments, which
follows, when considered together with the attached drawings and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic side view of a person with the
physiological parameter monitor in place within the esophagus.
[0025] FIG. 2 is a schematic view of one embodiment of an
electrical circuit for the physiological parameter monitor.
[0026] FIG. 3 is a schematic view of a preferred embodiment of the
physiological parameter monitor circuit, wherein the circuit also
includes a microprocessor.
[0027] FIG. 4 is a schematic side view of one embodiment of a
physiological parameter monitor.
[0028] FIG. 5 is a schematic side view of the physiological
parameter monitor with an elastic band attached.
[0029] FIG. 6 is a cut-away side view of the esophagus with
endoscopic placement of the monitor by means of an elastic
band.
[0030] FIG. 7 is a side elevational cross section through an
implantable probe in accordance with the present invention,
removably attached to a deployment device.
[0031] FIG. 8 is a schematic representation of an endoscope having
a deployment device and a probe positioned within the
esophagus.
[0032] FIG. 9 is a schematic illustration as in FIG. 8, with tissue
drawn into the tissue cavity.
[0033] FIG. 10 is a schematic representation as in FIG. 9 with an
attachment pin advanced through the tissue.
[0034] FIG. 11 is a schematic representation as in FIG. 10, with
the deployment device detached from the probe.
[0035] FIG. 12 is a side elevational view of an alternate
deployment device in accordance with the present invention.
[0036] FIG. 13 is a side elevational partial cross section through
the distal end of a deployment catheter of the type illustrated in
FIG. 12, removably connected to a probe.
[0037] FIG. 14 is a side elevational view as in FIG. 13, with the
probe attached to the tissue and the deployment catheter
disconnected from the probe.
[0038] FIG. 15 is a side elevational view of a further embodiment
of a deployment device in accordance with the present
invention.
[0039] FIG. 16 is an enlarged cross-sectional view through the
distal end of the deployment device of FIG. 15, following
application of vacuum.
[0040] FIG. 17 is a side elevational view as in FIG. 16, following
distal advancement of a needle.
[0041] FIG. 18 is a side elevational view as in FIG. 17, following
distal advancement of a dowel or pin through the needle.
[0042] FIG. 19 is a side elevational view as in FIG. 18, following
proximal retraction of the needle.
[0043] FIG. 20 is a side elevational view as in FIG. 19, following
detachment of the docking structure from the probe.
[0044] FIG. 21 is a side elevational view as in FIG. 18, showing a
transnasal embodiment of the invention.
[0045] FIG. 21A is a schematic cross section through a probe,
following attachment to a tissue surface.
[0046] FIG. 22A is a side elevational view of an additional
embodiment of a deployment device in accordance with the present
invention.
[0047] FIG. 22B is an enlarged cross sectional view through the
distal end of the deployment device of FIG. 22A, positioned
adjacent a tissue surface.
[0048] FIG. 22C is a side elevational view as in FIG. 22B,
following application of vacuum to the tissue.
[0049] FIG. 22D is a side elevational view as in FIG. 22C,
following deployment of the pin.
[0050] FIG. 22E is a side elevational view as in FIG. 22D,
following retraction of the locking wire and deployment of the
probe from the delivery device.
[0051] FIG. 23 is a circuit diagram of a preferred embodiment of
the physiological parameter monitor circuit, wherein the circuit
includes a microprocessor and an ISFET sensor.
[0052] FIG. 24 is a circuit diagram of an alternative embodiment of
the physiological parameter monitor circuit, wherein the circuit
includes a microprocessor and an antimony sensor.
[0053] FIG. 25 is a flow chart showing the main functions of the
monitor microprocessor.
[0054] FIG. 26 shows the message structure of the digital messages
sent by the monitor to a waiting receiver.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0055] The present invention provides a method and system for
monitoring physiological parameters within a body lumen (cavity).
The invention also comprises methods for attaching a physiological
parameter monitor to a wall of a body lumen. The term "lumen" as
used herein refers to the space within a tubular wall (e.g., a
vessel) or the cavity within a hollow organ. While the invention is
described in detail as applied to the human esophagus, those
skilled in the art will appreciate that it can apply to other body
lumens or cavities, such as those of the stomach, colon, rectum,
bladder, uterus, vagina, biliary ducts (including the common bile
duct), or blood vessels. The term "esophagus" in this discussion
includes the lower esophageal sphincter (LES). Where different
embodiments have like elements, like reference numbers are
used.
[0056] FIG. 1 illustrates how physiological parameter data can be
relayed by the monitor 18, which is positioned within the esophagus
30, to a radiofrequency receiver 32 (hereinafter "radioreceiver")
located outside the body of a person 40. As is illustrated in FIG.
1, more than one monitor 18 can be implanted so that data can be
obtained from a plurality of different locations as will be
described in greater detail below.
[0057] In certain embodiments, this transmission of data is
accomplished via radio telemetry in real time. The radioreceiver 32
receives physiological parameter data within 12 seconds after it is
measured by the monitor 18. After reception of this data, the
radioreceiver 32 apparatus can record, manipulate, interpret and/or
display the data, using technology well known to those skilled in
the art. In certain embodiments, the patient can wear the receiver
32 and recorder on, for example, a belt, bracelet, arm or leg band,
or necklace during the period of pH study or other analysis.
[0058] The receiver 32 and recording apparatus can have buttons or
other switches thereon that enable the patient or other person to
mark certain events in time during the recording period, such as
when symptoms occur, when the patient is eating, when the patient
is recumbent (either supine or prone), or when the patient is about
to sleep. This event marking can be made in any recording medium
that is used for recording the physiological parameter, such as
magnetic tape or an electronic digital memory chip, in ways that
are well known to those of skill in the art.
[0059] The monitor 18 can be made to sense the position of the
patient, whether horizontal, vertical, or somewhere between
horizontal and vertical. Such position sensing can be accomplished
through the use of electrical switches that utilize floating fluid
bubbles, as used in mechanical level sensing, or electronic
gyroscopic techniques as are known to those skilled in the art.
[0060] In certain embodiments, the monitor 18 can record and
compress physiological parameter data as it is gathered, rather
than transmit the data in real time. Following the assessment
period, or at intervals therein, an external transceiver can be
used to download pulses of condensed data. Transmission of data can
be initiated at predetermined intervals or by an activation signal
sent from the external transceiver or other activating device to
the monitor 18, as will be understood by those of skill in the art.
In this manner, a tabletop transceiver can be utilized, either at
the patient's home, or in the physician's office or other clinical
site.
[0061] In other embodiments, the monitor 18 can record, compress,
and store physiological parameter data as it is gathered, using a
memory chip and microprocessor. The person 40 can excrete the
monitor 18 in his or her stool, and the monitor 18 can be
retrieved. Subsequently, data stored in the monitor 18 can be
downloaded into an external data retrieval device, which can be a
computer or other analysis machine located outside the patient's
body. This downloading can be accomplished by IR or RF transmission
in response to an activation signal, using magnetic field or
radiofrequency technology well known to those skilled in the
art.
[0062] Although the typical gastroesophageal reflux study lasts 24
hours, other time periods for this study can exist, such as 48
hours or longer. Through the use of this invention, it is possible
that fewer than 24 hours may be needed to establish the diagnosis
of GERD, particularly because real-time monitoring can provide
nearly immediate evidence of reflux events. The actual durations of
various reflux studies using the present invention will be apparent
to those of skill in the art.
[0063] FIG. 2 illustrates a simplified circuit for a monitor 18 of
a physiological parameter (hereinafter "monitor 18"). This monitor
18 may also be referred to as a "probe" or "pill". In the
particular embodiment illustrated in FIG. 2, pH is the
physiological parameter to be sensed, and it is detected by a
transducer 110, which comprises a pH sensor and preferably also a
reference sensor. In the present invention, a monitoring transducer
(hereinafter "transducer") can be any transducer that senses a
physiological parameter and furnishes a signal one of whose
electrical characteristics, such as current or voltage, is
proportional to the measured physiological parameter.
[0064] Although a pH sensor is described here, those skilled in the
art will appreciate that a sensor of any of a variety of other
physiological parameters, such as pressure or temperature, can be
detected and monitored. Sometimes, temperature and/or pressure will
be sensed and transduced together with pH, in order to adjust the
pH readings and make them more accurate, or to supply additional
data helpful in the analysis of the patient's condition. In
addition, the concentration of ions or other solutes present in
body fluids can be detected and analyzed using this invention. For
example, ions such as sodium, potassium, calcium, magnesium,
chloride, bicarbonate, or phosphate may be measured. Other solutes
whose concentrations in body fluids are of importance and may be
measured by the present invention include, among others, glucose,
bilirubin (total, conjugated, or unconjugated), creatinine, blood
urea nitrogen, urinary nitrogen, renin, and angiotensin. Any
combination of two or more of the preceding parameters may be
sensed by the transducer 110. For any physiological parameter
sensed and transduced by means of a transducer, a reference sensor
may or may not be required.
[0065] FIG. 2 also illustrates a radiofrequency transmitter circuit
112 and a power source 114. The radiofrequency transmitter circuit
112 can comprise an antenna (or antenna coil), and the antenna can
be at least in part external to the monitor shell 120 (seen in FIG.
4). Alternatively, the antenna, if present, can be entirely
self-contained within the monitor shell 120. As an alternative to
RF transmission, a signal which is indicative of the monitored
parameter can be propagated through the patient's tissue from an
electrical contact on the probe to a conductive dermal electrode or
other conductor in contact with the patient.
[0066] When located within the monitor 18, the power source 114 can
be a battery or capacitor or any other device that is capable of
storing an electrical charge at least temporarily. In a battery
powered embodiment, battery life can be extended by disconnecting
the battery from other circuit components thereby limiting
parasitic current drain. This can be accomplished in a variety of
ways, such as by including a magnetically activated switch in the
monitor 18. This switch can be used to connect or disconnect the
battery as needed. By packaging the monitor 18 with an adjacent
permanent magnet, the switch can be opened thereby disconnecting
the battery and the shelf life of the device can thus be extended.
Removing the monitor 18 from the packaging (and the adjacent
permanent magnet) closes the switch and causes the battery to
become connected and supply power to the monitor 18.
[0067] In alternative embodiments, the source of power to the
monitor 18 can be external to the monitor 18 itself. For example,
the monitor 18 can derive power from an external electromagnetic
radiofrequency (RF) source, as occurs with passive RF telemetry
techniques, such as RF coupling, that are well known to those
skilled in the art. The monitor 18 can be energized by a
time-varying RF wave that is transmitted by an external transceiver
32, also known as an "interrogator," which can also serve as a
reader of data from the monitor 18. When the RF field passes
through an antenna coil located within the monitor 18, an AC
voltage is induced across the coil. This voltage is rectified to
supply power to the monitor 18. The physiological parameter data
stored in the monitor 18 is transmitted back to the interrogator 32
(FIG. 1), in a process often referred to as "backscattering." By
detecting the backscattering signal, the data stored in the monitor
18 can be fully transferred.
[0068] Other possible sources of power for the monitor 18 include
light, body heat, and the potential difference in voltage that can
be generated in body fluids and detected by electrodes made of
varying materials. The harnessing of such power sources for
biotelemetry purposes is well described in R. Stuart Mackay:
Bio-Medical Telemetry, Sensing and Transmitting Biological
Information from Animals and Man, 2d ed., IEEE Press, New York,
1993, whose section entitled "Electronics: Power Sources" is hereby
incorporated herein by reference.
[0069] FIG. 3 illustrates alternative embodiments of the
physiological parameter monitor circuitry. In this embodiment, a
microprocessor 116, also called a central processing unit (CPU), is
illustrated. This microprocessor 116 can perform one or more
functions, including temporary storage or memory of data, reception
of input signal from the transducer, and transformation between
analog and digital signals, among other functions that will be
apparent to those skilled in the art. The transducer 110,
radiofrequency transmitter 112, and power supply 114 are also
present. Many other circuitry components that can help to generate,
amplify, modify, or clarify the electrical signal can be used in
other embodiments of the monitor. Such components include buffers,
amplifiers, signal offset controls, signal gain controls, low pass
filters, output voltage clamps, and analog-to-digital converters,
among others. Numerous possible circuitry features of a portable pH
monitoring device, all of which can be used in the present
invention, are well described in U.S. Pat. No. 4,748,562 by Miller,
et al., the disclosure of which is incorporated in its entirety
herein by reference.
[0070] In certain embodiments, the monitor 18 further comprises a
digital recorder or memory chip (not illustrated), which records
the transduced physiological parameter data. This recorder or
memory chip will allow temporary storage of this data accumulated
over time (e.g., over a period of 24 hours for a typical
gastroesophageal reflux study).
[0071] FIG. 4 schematically illustrates the configuration of
certain embodiments of the physiological monitor 18. In this
embodiment, an outer shell 120 surrounds the monitor's 18
electronic components. The transducer 110, the radiofrequency
transmitter 112, the power supply 114, and a microprocessor 116 are
encased within the outer shell 120. In certain embodiments, the
shape of the shell 120 can resemble that of a pill or gel capsule,
as commonly used in various oral drug delivery systems.
[0072] The shell 120 can be made of any of various materials,
including plastics such as polycarbonates, polyethylene,
polytetrafluoroethelyne (Teflon.RTM.), nylon, delrin, or
polyethylene terephthalate. The material used for the shell 120
should be resistant to water and acidic environments because the
shell will be exposed, in some embodiments, to food, water, and
gastrointestinal contents, including gastric acid, which is very
caustic (with a pH of approximately 1).
[0073] The shell 120 can have a lubricious coating applied to its
outer surface, which reduces friction between the shell 120 and any
object or material that comes in contact with the shell 120, such
as the esophageal wall or any food or fluids that flow down the
esophagus 30 past the monitor. Such a coating can be made of
silicone, silicone derivatives, or other hydrophilic materials that
will be apparent to those skilled in the art. This slippery coating
on the surface of the shell 120 will reduce the likelihood of
occurrence of the following events: (1) ingested material will
adhere to the monitor 18, (2) the esophagus 30 will become
irritated from repeated contact with the monitor 18 during
peristalsis of the esophagus 30, and (3) peristalsis or flowing
food or fluid will cause detachment of the monitor 18 from its
attachment site.
[0074] In certain embodiments, the shape of the shell 120 is
streamlined with smooth rounded corners. This feature helps to
avoid injury to the gastrointestinal mucosa during endoscopic
placement of the monitor 18, while the monitor 18 is attached to
the esophagus, and, when the monitor 18 becomes unattached from the
esophageal wall, while the monitor 18 passes through the
gastrointestinal tract and is excreted in the stool. Preferably,
detachment occurs from about 2 days to about 10 days following
attachment to the esophageal wall.
[0075] The physiological monitor 18 can be placed in the esophagus
30 in a variety of ways. In certain embodiments of the present
method, the monitor 18 is placed into the esophagus 30 through the
use of a flexible or rigid endoscope 160 inserted through the nose
or mouth of the person 40. The monitor 18 can be constrained within
or by a deployment device, such as a catheter, until the physician
visually verifies attachment through the endoscope 160. Then the
monitor 18 can be intentionally deployed and left within the
esophagus, using methods known to those of skill in the art.
[0076] In other embodiments, a physician can attach the monitor 18
directly to the inner aspect of the esophageal wall through an
opening in the esophagus 30 (esophagotomy) or stomach 36
(gastrotomy).
[0077] The physiological monitor 18 can be attached to the
esophagus 30 in a variety of ways, also referred to herein as
"attachment means." In certain embodiments, as shown in FIG. 4, the
monitor shell 120 has an eyelet attachment 122, which serves to
hold a suture 30, string, staple, or other securing structure,
which can secure the monitor to the wall of the esophagus or other
body lumen wall. Besides the eyelet attachment 122, many other
possible modifications of or attachments to the shell 120, such as
one or more loops, rings, brackets, tacks, hooks, clips, strings,
threads, or screws, can be utilized to facilitate the attachment or
fixation of the monitor to a lumenal wall.
[0078] The monitor 18 can, in some embodiments, be attached to the
esophagus 30 through the use of a clip, which may resemble, for
example, an alligator clip. This clip may or may not utilize a
spring mechanism, and it can hold the monitor in place by
capturing, or "pinching," the mucosa and submucosa of the esophagus
30 between its arms or "jaws." The clip can have one or more of its
parts made of one or more absorbable or dissolvable materials, such
as are described below and are known to those skilled in the art.
This dissolvable material can facilitate the removal of the monitor
18 from the wall of the esophagus 30 after a given period of time.
As materials in the clip dissolve, the tension in the clip that
causes it to hold onto, or pinch, the esophagus 30 will eventually
decrease, and the clip will break free of the esophagus 30 and
travel through the gastrointestinal tract and into the patient's
stool.
[0079] In certain embodiments of the present method, as shown in
FIG. 5, the monitor 18 is attached to the esophagus 30 by means of
a suture loop or an elastic band 150. The elastic band can be
attached to the monitor 18 with an absorbable or nonabsorbable
suture, string, or thread, otherwise referred to as a "tether" 152.
This tether 152 can be made from a variety of materials, such as a
polymeric filament, which can be absorbable or nonabsorbable in
vivo.
[0080] In some embodiments, the tether 152 can be attached to a
tooth, such as a molar, of a person. The monitor 18 is thus
suspended in the esophagus by the tether 152, which is attached at
its other end to the tooth. The attachment to the tooth can be
performed by means of an elastic band, plastic band, adhesive
materials, or any other means for attaching a structure to a tooth,
as are well known in the dental art.
[0081] As shown in FIG. 6, the elastic band 150 can be placed
around a protuberance 154 in the wall of the esophagus 30 or other
body lumen. Such a protuberance 154 can be found as a naturally
occurring pathological structure, such as a polyp, or it can be
formed by a physician (as a "quasi-polyp") using an endoscope 160
by applying suction to the wall of the esophagus 30. Such
suction-induced protuberances 154 in the esophagus 30 are well
known to those skilled in the art and represent a commonly used
method of ligating (tying off) esophageal varices, which are
enlarged blood vessels in the wall of the esophagus 30 caused by
elevated portal venous pressure.
[0082] Although endoscopic ligation techniques typically result in
necrosis of the tissue that is elevated into a protuberance 154 and
ligated, in the present method the aim of this technique is merely
to provide a structure in the lumen of the esophagus 30 or other
body lumen upon which to attach temporarily the physiological
parameter monitor 18. Thus, it may be desirable not to attach the
elastic band 150 to the protuberance 154 too tightly, so as to
avoid compromise to the blood supply to the protuberance 154.
[0083] In order to avoid exposure of the attachment site to
refluxed gastric acid, it will at times be desirable to attach the
monitor 18 to the esophagus 30 at a site some significant distance
rostral (cephalad) to the LES. The monitor 18 can thereby be
suspended from the esophageal attachment site by the tether 152,
such that the monitor 18 is positioned close (typically 5 cm
superior) to the LES, to facilitate detection of gastroesophageal
reflux. This technique optimizes the likelihood that while the
monitor 18 is exposed to refluxed gastric acid, the esophageal
attachment site is not so exposed because it is sufficiently far
from the LES as to avoid the surge of refluxed gastric contents.
Distances between the attachment site and the monitor 18 of at
least about 0.5 cm, and as much as 10 cm or more, may be utilized
for this purpose.
[0084] In other embodiments of the present method, the monitor 18
can be attached to the wall of the esophagus 30 or other body lumen
using an adhesive substance (hereinafter "adhesive") either alone
or in combination with the mechanical attachment structures
disclosed herein. This adhesive can be any of a variety of
cyanoacrylates, derivatives of cyanoacrylates, or any other
adhesive compound with acceptable toxicity to human esophageal
cells that provides the necessary adhesion properties required to
secure the monitor 18 to the wall of the esophagus 30 for at least
a sufficient monitoring period of time. In certain embodiments the
monitor 18 can be directly attached to the wall of the esophagus 30
with the adhesive. In other embodiments, the monitor 18 can be
attached indirectly, utilizing an intermediate structure, such as
an anchor, to which the monitor 18 attaches and which is in turn
adhered to the esophagus 30 by means of the adhesive. One example
of this type of intermediate structure is an elongate strip of
cloth or plastic, secured at one end to the shell 120 and having a
tissue attachment surface along its length or at the other end for
enhancing adhesive or mechanical bonding to the esophagus 30. Other
intermediate structures and materials can be used, as will be
apparent to those skilled in the art.
[0085] In other embodiments of the present method, the monitor 18
is attached to the esophagus 30 using a self-expandable support
structure (not illustrated) that expands or widens to span the
diameter of the body lumen, so as to retain the monitor 18 therein.
Suitable support structures include self-expandable wire cages,
such as are used for supporting grafts in the abdominal aorta and
elsewhere in the vascular system. Stents, struts, and other
structural devices known to those of skill in the art may be used.
Many of these structural devices are used in the fields of vascular
radiology and cardiology for the purpose of maintaining patency in
blood vessels. These support structures can be made from a variety
of materials such as stainless steel, nitinol, or polymeric
filament, which can be absorbable or nonabsorbable in vivo.
[0086] In further embodiments of the present method, the monitor 18
is attached to the esophagus 30 using one or more sutures, clips,
staples, tacks, pins, hooks, barbs, or other securing structures
that can at least partially penetrate the mucosa of the esophagus.
These securing structures can be made from a variety of materials,
including absorbable materials, such as polylactic acid (PLA) or
copolymers of PLA and glycolic acid, or polymers of p-dioxanone and
1,4-dioxepan-2-one. A variety of absorbable polyesters of
hydroxycarboxylic acids may be used, such as polylactide,
polyglycolide, and copolymers of lactide and glycolide, as
described in U.S. Pat. Nos. 3,636,956 and 3,297,033, which are
hereby incorporated in their entirety herein by reference. The use
of absorbable materials allows the securing structure to dissolve
or resorb into human tissue after a known or establishable time
range, such as 48 to 72 hours, and the monitor 18 can thereby
become detached from the esophagus 30 and can then be excreted in
the patient's stool.
[0087] For example, one or more short pointed barbs can be
integrally formed with the shell 120 or secured thereto using any
of a variety of attachment techniques which are suitable depending
upon the composition of the shell 120 and the barb. This embodiment
can be pressed into the wall of the esophagus, thereby causing the
barb or barbs to penetrate the mucosa and enter the submucosa.
Preferably, any such barbs will not penetrate the muscular wall
surrounding the submucosa. Hooks may also be attached to or
integrally formed with the shell 120, so that the shell 120 can be
hooked onto the wall of the esophagus, possibly in combination with
the use of a bioadhesive. Such hooks and barbs may be formed from a
bioabsorbable or dissolvable material as has been discussed, to
permit detachment of the monitor after a suitable period of
time.
[0088] In accordance with a further aspect of the present
invention, the monitoring device may be provided with a tissue
attachment surface adapted for contacting a tissue site. A pin is
movable from a retracted position to allow the tissue attachment
surface to be brought into contact with or closely adjacent the
tissue at the preselected attachment site, and an extended position
in which it extends through the tissue adjacent the attachment
surface. One embodiment having a concavity at the tissue attachment
site is illustrated in FIG. 7.
[0089] As illustrated in FIG. 7, the monitor or probe 18 is
provided with an outer shell 120, for enclosing a transducer 110,
such as a pH sensor or other detector as has been described herein.
The transducer 110 may be recessed within the shell 120 and exposed
to the external environment through a fluid port 111.
Alternatively, the transducer 110 may be mounted in the wall of the
shell 120, or positioned on the exterior surface of the shell 120,
depending upon the nature of the transducer 110 and its fluid
contact and surface area requirements. The transducer 110 is in
electrical communication with the electronics of the probe 18, such
as a transmitter 112, CPU 116 and batteries or other power supply
114 as has been discussed.
[0090] The shell 120 is provided with a tissue attachment cavity
124 for receiving tissue at the attachment site. The shell 120 is
further provided with a docking structure 126, such as a threaded
aperture 128 or other structure for removable connection to a
delivery catheter 138. Preferably, the docking structure 126 is in
communication with the attachment cavity 124 such as by a vacuum
port or other lumen 130. This enables application of a vacuum
through the delivery catheter 138 and into the cavity 124, to draw
tissue into the cavity 124 as will be discussed below.
[0091] The delivery catheter 138 is provided with a proximal end
(not illustrated) and a distal end 140. The distal end 140 is
provided with a docking structure 142 such as a complimentary
thread 144 for removably engaging the threaded aperture 128 on
docking structure 126. Any of a variety of alternative releasable
docking structures may be utilized, as will be apparent to those of
skill in the art in view of the disclosure herein.
[0092] The delivery catheter 138 is further provided with a central
lumen 146 having an axially movable plunger 148. Plunger 148 is
provided with a distal end 162 having a removable attachment pin
164 carried thereon.
[0093] In use, the probe 18 is removably carried by the delivery
catheter 138, and may be advanced through the working channel on an
endoscope or other access device to an attachment site.
Alternatively, the delivery catheter is positioned at the
attachment site without the use of a scope. Deployment can be
accomplished "blind", using indicia other than visualization. For
example, by monitoring psi in a suction (e.g. 15-25 mm Hg) applied
to the cavity 124, the presence of tissue at the suction aperture
in the cavity 124 can be observed.
[0094] The probe 18 is positioned such that the attachment cavity,
124 is adjacent the attachment site. A vacuum is applied through
the lumen 146, to draw mucosa or other tissue into the attachment
cavity 124. Once a sufficient volume of tissue has been drawn into
the attachment cavity 124, the plunger 148 is advanced distally to
drive the pin 164 through the tissue to pin the probe 18 to the
attachment site. In the illustrated embodiment, a pin guide 132,
such as a blind lumen, is provided on the distal end of a pin
travel path, to further secure the probe 18 at the tissue site.
Following deployment of the pin 164, the pin is detached from the
distal end 162 of plunger 148, and the delivery catheter 138 is
detached from the docking structure 126 on probe 18.
[0095] Preferably, the shell 120 is provided with at least a window
zone or viewing area 166 to permit endoscopic visualization of the
attachment cavity 124. This enables the clinician to view the
tissue drawn into the attachment cavity 124, and visually assess
the point at which a sufficient amount of tissue has been drawn
into attachment cavity 124 to provide an adequate engagement
between the pin 164 and the tissue to secure the probe 18 to the
attachment site. Window 166 may be a separate structure, such as a
plastic or glass wall which is transparent to visible light.
Alternatively, the entire shell 120 may be constructed from a
relatively clear material, such as polycarbonate, polysulfone or a
thermoset material such epoxy, so that the attachment cavity 124
may be viewed through the opposing side of the shell 120.
[0096] The pin 164 may comprise any of a variety of materials such
as absorbable or degradable materials discussed above, which will
permit the probe 18 to automatically disengage from the attachment
site after a period of time. Alternatively, the pin 164 may
comprise any of a variety of biocompatible structural materials
which are well known in the medical art, such as stainless steel,
titanium, high density polyethylenes, nylon, PTFE, or others which
are well known in the art.
[0097] One method of attaching the probe to the tissue surface is
further illustrated by FIGS. 8-11. As illustrated in FIG. 8, the
probe 18 is attached to a deployment catheter 138, which extends
through the working channel of an endoscope. The endoscope carrying
the deployment catheter 138 and probe 18 is transluminally advanced
through the esophagus or other body lumen or hollow organ to
position the probe 18 at the attachment site. Once positioned at
the site, vacuum is applied to the probe to draw mucosa into the
chamber. In the illustrated embodiment, the wall of the probe is
clear and a viewing zone 166 is provided with a convex curved outer
surface to magnify the image of the mucosa within the attachment
cavity 124. Alternatively a flat wall may be used.
[0098] Depending upon the desired attachment site and other
clinical requirements, the deployment assembly may further be
provided with one or more steering structures to advance the probe
laterally within the lumen, in order to position the attachment
cavity 124 sufficiently closed to the mucosal layer to draw mucosa
into the attachment cavity 124. For example, the delivery catheter
138 and/or endoscope may be provided with an inflatable balloon on
a medial side, which, upon inflation, will advance the probe
laterally such that the attachment cavity 124 is firmly positioned
against the lateral wall. Axially movable deflection wires and
other steering structures are well known in the catheter and
endoscope arts, and can be readily incorporated into the delivery
catheter 138 as desired. The catheter may also be provided with
torque transmission enhancement structures, such as a braided or
woven polymeric or metal wall layer.
[0099] Referring to FIG. 10, the endoscope is utilized to visualize
the mucosa within the attachment cavity 124 following application
of vacuum. Preferably, sufficient vacuum is applied to cause the
mucosa to contact ("wet") the top of the cavity, before the pin is
advanced through the tissue. Following deployment of the pin, the
deployment catheter is disengage from the probe and removed.
[0100] An alternate delivery catheter is illustrated in FIGS.
12-14. Referring to FIG. 12, the delivery catheter 138 is provided
with a docking structure 126 such as a collet 168. Collet 168
comprises two or three or more arms 170 which are movable between a
generally axial orientation for grasping the probe and an inclined
orientation for releasing the probe. Each arm 170 is provided with
a distal attachment surface 172, such as on a proximal face of a
radially inwardly directed flange. The arms 170 may be biased
radially outwardly from the longitudinal axis of the delivery
catheter 138, or may be mechanically linked to a proximal control
for opening the collet 168 to release the probe.
[0101] The collet 168 is attached to the distal end of a tubular
body 174. The proximal end 176 of tubular body 174 is provided with
a manifold 178, having a vacuum port 180 and a plunger 182 thereon.
Vacuum port 180 is in communication with a central lumen extending
through tubular body 174 as has been described, for applying a
vacuum to the attachment cavity 124 in probe 18. The plunger 182 is
axially movable to deploy a tissue pin 164 through mucosa or other
tissue drawn into the attachment cavity 124.
[0102] A proximal control 186 may be manipulated to axially
proximally retract the movable sleeve 184, to open and close the
collet 168. Referring to FIG. 13, the delivery catheter 138 is
illustrated with the movable sleeve 184 in a distal position, to
lock the collet 168 to the docking structure 126 on probe 18. The
proximal projection 188 is provided with one or more radially
outwardly extending projections, such as an annular flange 190, for
engaging the attachment surfaces 172 on the collet 168.
[0103] In this embodiment, the docking structure 126 comprises a
proximal projection 188 illustrated as a cylindrical element having
a central lumen extending therethrough for both axially movably
receiving the pin 164 and providing communication between the
central lumen and the attachment cavity 124. Multiple lumen systems
may also be devised, in which the pin travels through a different
lumen than the vacuum, as will be apparent to those of skill in the
art in view of the disclosure herein.
[0104] Following deployment of the pin 164, as has been previously
discussed, the proximal control 186 is manipulated to proximally
retract the sleeve 184, thereby opening collet 168 to release the
docking structure 126.
[0105] Any of a variety of docking structures can be readily
devised, as will be apparent to those of skill in the art in view
of the disclosure herein. In general, the docking structure permits
a removable attachment of the probe to a deployment catheter. The
docking structure permits communication between a vacuum lumen in
the deployment catheter and a vacuum pathway in the probe. In
addition, the docking structure permits communication between a
deployment element in the catheter and a pin adapted to cross at
least a portion of the cavity.
[0106] The attachment cavity 124 in any of the foregoing probe
embodiments can have any of a variety of configurations.
Preferably, the depth measured in the radial direction is related
to the cross-sectional area of the opening of the cavity in a
manner that permits mucosa or other tissue to prolapse into the
cavity to a sufficient depth to accomplish the pin function without
causing unnecessary trauma to the tissue. In general, depth to
opening ratios on the order of about 1:1 are presently
contemplated. In general, the tissue opening to the cavity 124 will
have an axial length within the range of from about 3 mm to about 5
mm, a width of from about 3 mm to about 5 mm and a depth of from
about 3 mm to about 5 mm.
[0107] Preferably, the vacuum port or ports between the vacuum
lumen and the attachment cavity 124 are positioned sufficiently far
away from the opening of the cavity that a sufficient volume of
tissue will be drawn into the cavity 124 before occluding the
vacuum ports. Two or more ports may be provided, to allow
additional application of vacuum following occlusion of the first
vacuum port.
[0108] Preferably, the opposing surface of the cavity towards which
the pin is advanced is provided with a texture or other friction
enhancing structure, for assisting to stabilize the tissue during
the pin deployment step. Friction enhancing surfaces, such as a
plurality of ridges or grooves may be utilized, to assist in
retaining tissue while at the same time minimizing trauma.
[0109] Referring to FIG. 15, there is illustrated a side
elevational view of an alternate delivery catheter 138 in
accordance with the present invention. The delivery catheter 138
comprises a tubular body 202 having a proximal end 200 and a distal
end 140. The delivery catheter 138 has an overall length within a
range of from about 60 cm to about 80 cm, and a maximum outside
diameter through the tubular body 202 of preferably no more than
about 3 mm. Construction materials and manufacturing methods for
the tubular body 202 as well as other components of the delivery
system are well understood in the catheter manufacturing arts.
[0110] The tubular body 202 comprises an outer sleeve 204 which
extends from a proximal end 206 to a distal end 208. The distal end
208 of outer sleeve 204 is connected to or integrally formed with a
docking structure 142, which will be discussed in greater detail
below. The proximal end 206 is spaced sufficiently far (proximally)
from the docking structure 142 that the proximal end 206 remains
outside of the patient during the procedure while the docking
structure 142 is at the treatment site. In general, the length of
the outer sleeve 204 is from about 30 cm to about 60 cm, and the
length of the docking structure 142 is within the range of from
about 2 cm to about 10 cm.
[0111] An intermediate tube 210 extends axially through the central
lumen in outer sleeve 204. Intermediate tube 210 is movably
positioned within the outer sleeve 204 such that it can be moved
between a first position in which a distal end 214 of intermediate
tube 210 removably engages the probe 18, and a second position in
which the distal end 214 of intermediate tube 210 is disengaged
from the probe 18. A releasable shaft lock 211 is preferably
provided to allow the position of the intermediate tube 210 to be
locked with respect to the outer sleeve 204, such as to secure the
probe 18 within the docking structure 142 during placement.
Preferably, the intermediate tube 210 is axially reciprocally
movable within the outer sleeve 204 between the first and second
positions.
[0112] Intermediate tube 210 extends from a manifold 212 to the
distal end 214. Manifold 212 may be provided with any of a variety
of access ports, depending upon the desired functionality of the
delivery catheter 138. In the illustrated embodiment the manifold
212 is provided with a vacuum port 214. The vacuum port 214 is in
communication with a central lumen (not illustrated) within the
intermediate tube 210, which communicates with the cavity 124 in
probe 18 when the probe is engaged in the docking structure 142.
This enables application of vacuum to the vacuum port 214, to draw
tissue within cavity 124 in the probe 18 as has been discussed.
[0113] Manifold 212 is also preferably provided with an access port
which may be provided with a Tuohy Borst valve 216, for axially
movably receiving a needle tubing 218. Needle tubing 218 extends
throughout the length of the intermediate tube 210, and is
advanceable into the cavity 124 as will be discussed.
[0114] A pin plunger 148 is axially movably positioned within a
central lumen in the needle tubing 218. Pin plunger 148 extends
from a proximal end 220 which remains outside of the proximal end
of the needle tubing 218, to a distal end which is positioned at or
about a distal end 214 of the intermediate tube for reasons which
will become apparent. The proximal end of pin plunger 148 may be
connected to any of a variety of controls, such as a lever or
slider switch.
[0115] In one embodiment of the invention, the outer sleeve 204
comprises Teflon, having an axial length of about 60 cm. The
intermediate tube 210 comprises nylon, having an axial length of
about 80 cm. Both the outer sleeve 204 and intermediate tube 210
may be extruded from any of a variety of materials well known in
the catheter arts.
[0116] The manifold 212 is preferably injection molded, in
accordance with well known techniques. Needle tubing 218 may
comprise stainless steel or various polymers such as PET, having an
outside diameter of about 0.040 inches, an inside diameter of about
0.020 inches, and an axial length of about 90 cm. The pin plunger
148 comprises 0.014" stainless wire, having a length sufficiently
longer than the needle tubing 218 to enable distal deployment of
the probe retention pin. Further construction details of the
delivery catheter 138 will be apparent to those of skill in the art
in view of the disclosure herein.
[0117] Referring to FIGS. 16-21A, further details of the docking
structure 142 and distal end 140 will become apparent from the
discussion of the method of using the delivery catheter 138.
[0118] Referring to FIG. 16, the delivery catheter 138 is
illustrated in position against the surface of a tissue structure
224, such as the wall of the esophagus. The distal end 214 of the
intermediate tube 210 is positioned within a lumen 130 which
extends from a proximal end of the probe 18 into the cavity 124. A
blind end 132 is also in communication with the cavity 124 as has
been discussed. At least one locking structure 226 such as a clip
is provided in or near the blind end 132, for retaining the pin as
will be discussed.
[0119] The probe 18 is releasably retained within the docking
structure 142 during the positioning step. Docking structure 142
comprises a body 228 having a concavity 230 thereon for receiving
the probe 18. A distal engagement structure 232 such as a
proximally extending pin 234 is provided on the docking structure
142, within the cavity 230. Engagement structure 232 may comprise
any of a variety of mechanical interfit structures, adapted to
cooperate with the distal end 214 of intermediate tube 210 to
releasably retain the probe 18 within the cavity 230. In the
illustrated embodiment, retention pin 234 extends proximally into a
recess 236 on the distal end of the probe 18. One or more guide
pins or other guide structures 238 may also be provided, as
desired, to retain the probe 18 in the proper position within
cavity 230.
[0120] FIG. 16 illustrates the delivery catheter 138 in a position
such that the probe 18 is in contact with the wall of the tissue
structure 224. Vacuum has been applied to vacuum port 214, which is
in communication with the cavity 124 by way of intermediate tube
210 and lumen 130. In this manner, a portion 240 of tissue 224 has
been drawn within cavity 124.
[0121] Referring to FIG. 17, the needle tubing 218 has been
advanced distally within the intermediate tube 210, to advance the
distal end 242 of a needle 244 through the tissue portion 240.
Needle 244 may comprise a sharpened distal portion of the needle
tubing 218, or may comprise a separate needle tip which is secured
to the distal end of the needle tubing 218.
[0122] Referring to FIG. 18, the pin plunger 148 is thereafter
advanced distally within the needle tubing 218 to advance a pin 246
distally out of the distal end 242 of needle 244. The pin 246 is
provided with a complementary surface structure for engaging lock
226. Any of a variety of mechanical interfit locking structures may
be utilized, such as an annular recess on the outside surface of
pin 246, which engages radially inwardly projecting tabs or flanges
in the blind end 132. Alternatively, any of a variety of ramped or
ratchet-type interference fit structures may be utilized. The pin
has an axial length within the range of from about 3 mm to about 10
mm, and a diameter within the range of from about 0.5 mm to about 2
mm. Any of a variety of materials, such as stainless steel, Nitinol
or biocompatible polymers may be used for pin 246.
[0123] Following deployment of the pin 246, the needle tubing 218
and pin plunger 148 are proximally retracted to leave the pin 246
in position. Vacuum is disconnected and the intermediate tube 210
is proximally retracted from lumen 130 to disengage the probe 18
from the docking structure 142. The delivery catheter 138 may be
advanced slightly distally to disengage the retention pin 234, or
other removable locking structure, and the delivery catheter 138 is
thereafter removed from the patient leaving the probe 18 in
position as shown in FIG. 21A.
[0124] Referring to FIG. 21, there is illustrated an alternate
embodiment of the delivery catheter 138 at the procedural stage
previously illustrated in FIG. 18. In the embodiment of FIG. 21, an
elongate flexible distal nose portion 250 is provided on the distal
end 140 of the delivery catheter 138. The distal nose 250 comprises
a blunt, atraumatic tip, which enables deflection of the docking
structure 142 along the soft palette during a transnasal approach.
Nose 250 may comprise any of a variety of soft, flexible materials,
such as silicone, neoprene, latex, and urethane.
[0125] A further embodiment of a delivery catheter 138 is
illustrated in FIG. 22A. Details of the distal end 140 including
the docking structure 142 are illustrated in FIGS. 22B-22E, which
show sequential steps in the deployment of a probe 18.
[0126] Delivery catheter 138 illustrated in FIG. 22A is provided
with a control 400 on the proximal end 200. Control 400 in the
illustrated embodiment comprises a housing 402 and a plunger or
other manipulator 404. One or more additional controls may be
provided, depending upon the desired functionality of the delivery
catheter 138. In the illustrated embodiment, distal advancement of
the plunger 404 enables deployment of the pin 246 as has been
discussed. Proximal retraction of the plunger 404, or manipulation
of other component on control 400 proximally retracts a locking
wire 408 to release the probe 18 from the docking structure
142.
[0127] In this embodiment, the docking structure 142 is provided
with a docking surface on concavity 234 for removably receiving the
probe 18. The probe 18 is retained on the docking structure 142 by
a lock, 406. In the illustrated embodiment, the lock 406 comprises
a locking lumen 410 on the probe 18, which, when the probe 18 is
positioned on the docking structure 142, aligns with a lumen 412
which removably carries a locking wire 408. See FIG. 22E. As will
be seen by reference to FIGS. 22B through 22E, proximal retraction
of the locking wire 408 following attachment of the probe 18 to the
tissue 224 causes the locking lumen 410 and probe 18 to become
disengaged from the docking structure 142.
[0128] In addition to measuring pH in the esophagus, the probe 18
may be utilized to measure any of a variety of additional
parameters such as esophageal pressure, and a respiratory rate. The
probe 18 may also be utilized in the uterus to provide continuous
or periodic monitoring of temperature, as a fertility monitor. In a
further embodiment, the probe 18 maybe utilized in the bladder to
measure muscular contraction or pressure waves.
[0129] The deployment of the probe 18 may be accomplished under
endoscopic visualization as has been discussed. Alternatively, the
probe 18 may be introduced "blind" either through the mouth or
through the nose. Confirmation that the probe 18 is in an
appropriate position for attachment to the esophageal wall in a
blind approach may be accomplished by providing a pressure gauge in
communication with the cavity 124. Occlusion of the cavity 124 will
be observed on the pressure gauge, and provides an indication that
tissue has been drawn into the cavity, so that deployment is
appropriate.
[0130] Alternatively, the monitor 18 may be secured to the wall of
the esophagus or other tissue surface by one or more bands which
wrap around the monitor 18 and are attached at either end to the
tissue surface. Either end of the band may be attached to the
tissue surface such as through the use of barbs or hooks, as
discussed above. As a further alternative, the monitor 18 may be
secured to the tissue surface using a bioabsorbable suture as are
known in the art. The suture may be passed through the mucosa,
travel laterally through the submucosa and exit the mucosa to form
an attachment loop. The suture may travel over the monitor 18 and
again travel through the mucosa, along the submucosa and exit the
mucosa where it is, tied off with the other suture end. This may be
accomplished using any of a variety of endoscopic instruments
adapted for suturing as will be apparent to those of skill in the
art.
[0131] In some embodiments, a computer software program is used to
analyze the physiological parameter data obtained over a period of
time. Such analysis can include graphical representation of the
data, identification of abnormal values outside the range of normal
(such as pH values outside the range of about 4 to 7, which may
represent reflux events), and averaging of data values, among other
types of analysis that will be apparent to those skilled in the
art.
[0132] The method of the present invention may comprise deploying
two or three or four or more probes in a single patient, to
accomplish any of a variety of objectives. For example, multiple pH
probes may be positioned at different axial distances along the
wall of the esophagus from the LES, to monitor the change in pH as
a function of distance from the LES. Each probe preferably
transmits at a unique frequency or with a unique code to enable
interpretation of the received data. In this aspect of the
invention, each of the multiple probes monitors the same parameter
or parameters. In an alternate aspect of the invention, two or more
probes may be deployed within a patient such that each probe
monitors at least one analyte or parameter that is not monitored by
the other probe. Thus, a first probe is positioned at a first site
in the body, and detects at least a first parameter. A second probe
is positioned at a second site in the body, and measures at least a
second parameter. Installation of multiple probes may be
accomplished utilizing procedures and devices described above in
connection with the installation of a single probe. Data from each
of the plurality of probes is preferably transmitted and received
in a manner which permits the received data to be attributed to a
particular probe. This may be accomplished, for example, by
transmitting at different RF frequencies, encoding the data, or any
of a variety of other manners which are well understood in the
radio frequency transmission arts.
[0133] FIG. 23 illustrates a circuit diagram of a preferred
implementation of a physiological parameter monitor circuit 300.
The monitor circuit 300 is contained within the monitor 18 and
comprises circuitry to monitor pH, amplify and process the pH
measurement, encode a digital message with information including
the pH measurement, and transmit the digital message via an RF
transmitter, 112 in a manner that will be described in greater
detail below.
[0134] The monitor circuit 300 comprises a power source 114 and a
hermetic switch 304. The power source 114 in this embodiment
comprises two 5 mm silver oxide coin cells connected in series and
a plurality of capacitors that stabilize the output voltage. The
hermetic switch 304 is a normally closed, magnetically activated
switch. A permanent magnet is placed adjacent the hermetic switch
304 in the shipping packaging of the monitor 18 to open the
hermetic switch 304 and disconnect the power source 114 from a
microprocessor 116 and non-volatile memory 302. While the monitor
18 is adjacent the permanent magnet in the shipping packaging, the
open hermetic switch 304 limits parasitic current drain through the
microprocessor 116 and the non-volatile memory 302. When the
monitor 18 is removed from the shipping packaging and distanced
from the permanent magnet included therein, the open hermetic
switch 304 returns to its normally closed position and permits
current flow to the monitor circuit 300.
[0135] The monitor circuit 300 also comprises a microprocessor 116,
also called a central processing unit (CPU). This microprocessor
116 can perform one or more functions, including temporary storage
or memory of data, reception of input signals from the transducer,
comparison and correction of a signal with respect to a stored or
measured reference signal, and transformation between analog and
digital signals, among other functions that will be apparent to
those skilled in the art. Moreover, in this embodiment, the
microprocessor 116 includes an internal clock for tracking a
measurement/transmission cycle as will be described in greater
detail below. The microprocessor of this embodiment is a type
12C672 available from MicroChip, Inc. of Arizona.
[0136] The monitor circuit 300 also comprises non-volatile memory
302. The non-volatile memory is connected to and accessible by the
microprocessor 116. The non-volatile memory 302 stores calibration
information for the transducer 110. The non-volatile memory 302
also stores the unique identification number for the monitor 18.
The non-volatile memory 302 will allow temporary storage of data
accumulated over time (e.g., over a period of 24 hours for a
typical gastroesophageal reflux study). The non-volatile memory is
a type 24LC00 available from MicroChip, Inc. of Arizona.
[0137] The monitor circuit 300 also comprises a transducer 110. In
this embodiment the transducer 110 is configured to function as a
pH sensor. In one embodiment, the transducer 110 comprises an ion
sensitive field effect transistor (herein after ISFET) 314. The
ISFET 314 is a field effect transistor that is responsive to
ambient ion concentration, in this embodiment, H+ ions. The ISFET
314 is switchably driven at a constant voltage by the power source
114. The concentration of H+ ions, thereby the pH, in the fluid
surrounding the ISFET 314 alters the current flow through the ISFET
314. The current flows through a signal resistor 312 to ground and
thus generates an initial pH signal across this signal resistor
312. This initial pH signal is of very low amplitude and is
amplified by an amplification circuit 308 before being sent to the
microprocessor 116.
[0138] The non-inverting input of the amplification circuit 308 is
driven through a voltage divider by the microprocessor 116. The pH
signal generated by the ISFET 314 across the signal resistor 312 is
connected to the inverting input of the amplification circuit 308.
The amplified pH signal is sent to the microprocessor 116. The
amplified pH signal output from the amplification circuit 308 is
also tied to a pH reference 328. The pH reference 328 is a
saturated potassium chloride gel that is well known to those
skilled in the art. In an alternative embodiment the pH reference
328 can comprise a silver/silver chloride solid state
reference.
[0139] Hence, the pH level applied to the gate of the ISFET 314
results in a voltage appearing at the resistor 312 that is
amplified and combined with the pH reference 328 signal before
being sent to the microprocessor 116. As the pH level changes, the
voltage at the resistor 312 will also change as will the voltage
being sent to the microprocessor 116. In this way, the
microprocessor 116 receives a signal that is indicative of the
sensed pH level.
[0140] The monitor circuit 300 also comprises a transmitter 112.
The transmitter 112 receives digital signals from the
microprocessor 116 and transmits the signals at a MHz frequency
using an amplitude shift keying transmission format in a manner
well known to those skilled in the art. The transmitter 112
comprises a RC filter network 316, an oscillator 306, a transistor
318, RF coils 322, biasing network 324, and an antenna 326. The
microprocessor 116 sends a serial digital signal that will be
described in greater detail below on the GP2 pin through the RC
filter network 316. The digital signal is superimposed on the MHz
output of the oscillator 306. The combined signal triggers the base
of the transistor 318. The transistor 318 is connected to the
biasing network 324 and also to the power source 114 through the RF
coils 322. The RF coils 322 comprise two inductors connected in
series. The connection of the two inductors is also connected to a
first end of the antenna 326. The time varying signal triggering
the base of the transistor 318 generates a corresponding time
varying current in the RF coils 322 which induces a time varying
field that is broadcast via the connected antenna 326.
[0141] In an alternative embodiment, the transducer 110 comprises
an antimony electrode 350 as shown in FIG. 24. The antimony
electrode 350 is a device adapted to measure pH in a manner well
known in the art. The monitor circuit 300 of this embodiment is
substantially similar to the monitor circuit 300 previously
described wherein the transducer 110 comprises the ISFET 314 and
signal resistor 312. The antimony electrode 350 and the pH
reference 328 are connected to the amplification circuit 308 in a
manner well known in the art. The amplification circuit 308 of this
embodiment is adapted to provide approximately two to five times
signal amplification.
[0142] FIG. 25 shows a flow chart depicting the manner in which the
microprocessor 116 controls the operation of the monitor circuit
300. The microprocessor 116 and thereby the monitor circuit 300 has
five basic operational states: non-active 348, measurement 336,
correction 338, message formation 340, and transmission 342. The
microprocessor 116 also has a calibration state 344 that is
normally only performed once prior to implanting the monitor 18 in
a patient. The microprocessor 116 performs three main decisions: is
the monitor 18 calibrated 332, is it time to make a measurement
334, and is a transmitter status message needed 346. The
microprocessor 116 conducts a measurement cycle at a variable
interval that in this embodiment is approximately every 6 seconds.
A transmission cycle is performed by the microprocessor 116 every
other measurement cycle, i.e. every 12 seconds in this
embodiment.
[0143] The monitor circuit 300 initiates operation with a power on
330 state when the monitor 18 is removed from the shipping
packaging and distanced from the permanent magnet included therein,
which returns the open hermetic switch 304 to its normally closed
position and permits current flow to the monitor circuit 300. The
microprocessor 116 then performs the calibration decision 332. If
the monitor 18 is calibrated the microprocessor 116 performs the
measurement decision 334. If the microprocessor 116 determines that
it is time to perform a pH measurement, the microprocessor places
the monitor circuit 300 into the measurement state 336.
[0144] The microprocessor 116 places the monitor circuit 300 into
the measurement state 336 by enabling the GP0 pin of the
microprocessor 116 which provides power to the transducer 110. The
transducer 110 measures the pH, amplifies the signal, and sends the
signal to the microprocessor 116 in the manner already described.
The measurement state 336 takes approximately 20 ms. After the
microprocessor 116 receives the pH measurement signal from the
transducer 110, the microprocessor 116 disables the transducer 110.
By enabling the transducer 110 for approximately 20 ms out of a 6
second cycle, the monitor circuit 300 realizes significant power
sayings compared to continuously monitoring the pH and thus
significantly extends the power source's 114 useful life.
[0145] After the completion of the measurement state 336, the
microprocessor 116 enters the correction state 338. The
microprocessor 116 calls the non-volatile memory 302 for the
calibration values stored therein. The microprocessor 116 then
corrects the measured pH signal as needed in a manner well known to
those skilled in the art.
[0146] Once the microprocessor 116 has completed the correction
state 338, the microprocessor 116 enters the message formation
state 340. In the message formation state 340, the microprocessor
116 prepares a digital message in a manner that will be described
in greater detail below. Once the microprocessor 116 has completed
the message formation state 340, the microprocessor 116 enters the
transmission state 342. The microprocessor 116 sends the digital
message to the transmitter 112 for transmission in the manner
previously described.
[0147] Once the monitor circuit 300 completes transmitting a
digital message, the microprocessor 116 returns to the calibration
decision 332 and the measurement decision 334. The correction 338,
message formation 340, and transmission 342 states together take
approximately 60 ms. A measurement/transmission cycle is performed
approximately every 12 seconds. Thus the monitor circuit 300 spends
much of its operational time in a non-active state 348. The
non-active state 348 refers to the period during which neither the
transducer 110 nor the transmitter 112 is active and the
microprocessor 116 is in a waiting mode. The non-active state 348
occupies most of the 12 second measurement/transmission cycle.
During the non-active state 348, the monitor circuit 300 and the
monitor 18 consume a minimum amount of power from the power source
114. In this embodiment, the microprocessor 116 is primarily only
operating an internal clock to track the measurement/transmission
cycle.
[0148] While the microprocessor 116 is performing the measurement
decision 334, if a measurement is not needed, the microprocessor
116 monitors whether a transmitter status message is needed in the
transmitter status state 346. If the microprocessor 116 determines
that a transmitter status message does need to be sent, the
microprocessor 116 prepares a digital message containing
information about the monitor circuit 300 status in a manner that
will be described in greater detail below. The monitor circuit 300
then transmits the status message in the manner previously
described.
[0149] In order to provide accurate pH measurements, the monitor
circuit 300 must first be calibrated. The calibration can be
performed at the manufacturer prior to shipment of the monitor 18
or can be performed by the user prior to implantation of the
monitor 18 in the patient. Calibration involves comparing the pH
value measured by the transducer 110 to that of the pH reference
328 in solutions of known pH and generating correction values.
Typically two solutions of known pH are selected and prepared in a
manner well known to those skilled in the art.
[0150] In the calibration decision 332, the microprocessor 116
checks whether or not the non-volatile memory 302 has calibration
values and if it does not, the microprocessor 116 puts itself into
calibration state 344. A message is sent to the transmitter 112 to
indicate that the monitor circuit 300 is ready for the first
solution. The monitor 18 is then placed in the first solution and
the monitor circuit 300 measures the pH and prepares a first pH
correction value with respect to the pH reference 328. The monitor
circuit 300 then sends a message that the monitor circuit 300 has
finished calibrating the first solution and is ready for the second
solution. The monitor 18 is then typically washed and inserted into
the second solution. The monitor circuit 300 measures a second pH
value and generates a second pH correction value with respect to
the pH reference 328. The monitor circuit 300 then evaluates the
calibration values and determines if the calibration procedure was
successful. A message is then sent indicating that either the
calibration is complete and successful or that calibration errors
occurred. Once the calibration procedure is successfully completed,
the non-volatile memory 302 stores the calibration information from
the pH calibration measurements.
[0151] The monitor 18 can be calibrated at the factory before it is
packaged for delivery. By pre-calibrating a number of monitors 18
at the factory, each monitor 18 can be more accurately calibrated.
The precalibrated monitor 18 is available for immediate use and
does not require the user to prepare solutions of known pH or to
perform the calibration procedure prior to using the monitor 18.
Precalibration provides added economy, greater convenience for the
user, and quicker availability for implantation in the patient.
[0152] The microprocessor 116 formats digital signals to be
transmitted via the transmitter 112. The microprocessor 116
prepares digital messages in the format shown in FIG. 26 in a
manner well known to those skilled in the art. The digital message
begins with a preamble. The message then includes a header that
includes a digital signal identifying the monitor 18. This
transmitter ID is stored in and recalled from the non-volatile
memory 302. The header then provides a message ID. The message ID
specifies what kind of information is being provided in the digital
message. The message ID can indicate that the information provided
is the transmitter status, calibration data, or pH measurements. A
variable length payload is then included which provides the data
specified by the message ID. The digital message concludes with a
checksum.
[0153] The payload provides the main data of the digital message
and is of a variable length depending on what information is being
provided. If the transmitter status is being sent, the payload
tells whether or not the transmitter is calibrated and whether the
power supply 114 voltage is low enough to cause imminent
transmitter shut down. The payload also provides information about
the current watchdog reset count, the monitor circuit's 300 current
transmit count, and the current power supply 114 voltage.
[0154] If the message is providing calibration status information,
the payload provides information that the monitor circuit 300 is in
calibration mode and one of the following states: user is to
prepare Liquid 1, the monitor circuit 300 is calibrating Liquid 1,
the monitor circuit 300 is finished calibrating Liquid 1 and is
ready for the user to prepare Liquid 2, the monitor circuit 300 is
calibrating Liquid 2, the monitor circuit 300 has finished
calibrating Liquid 2 and has not detected calibration errors, or
the monitor circuit 300 has detected calibration errors. The
message also provides two calibration values.
[0155] If the message is providing pH measurement information, the
message gives the last measured pH value. The message also provides
the second to last measured pH value.
[0156] Once the microprocessor 116 has formatted the message, the
message is sent via the GP2 pin of the microprocessor 116 to the
transmitter 112 in a serial format in the previously described
manner. Once the transmission of the message is complete, the
transmitter 112 and the transducer 110 are inactive for the
remainder of the measurement/transmission cycle. As previously
mentioned, the measurement cycle takes approximately 20 ms. The
correction, message formation, and transmission cycles together
take approximately 60 ms. Together a complete
measurement/transmission cycle takes approximately 80 ms. The
monitor circuit 300 is inactive for the remainder of the
measurement/transmission period of approximately 12 seconds.
[0157] It can be appreciated that by only activating the monitor
circuit 300 for approximately 80 ms out of a 12 second period, the
monitor 18 consumes appreciably less power than it would by
continuous operation and is thereby able to extend the life of the
power supply 114. In addition, by alternating the active status of
the transmitter 112 and the transducer 10 and having the one not
active in an inactive state, the monitor circuit 300 is able to
further reduce its power consumption rate and increase the life
span of the power supply 114.
[0158] Although the present invention has been described in terms
of certain preferred embodiments, other embodiments of the
invention will become apparent to those of skill in the art in view
of the disclosure herein. Accordingly, the scope of the present
invention is not intended to be limited by the foregoing, but
rather by reference to the attached claims.
* * * * *