U.S. patent application number 16/943647 was filed with the patent office on 2020-11-19 for method and apparatus for pressure measurement.
This patent application is currently assigned to Potrero Medical, Inc.. The applicant listed for this patent is Potrero Medical, Inc.. Invention is credited to Daniel R. BURNETT, Paul B. GUERRA, Gregory W. HALL, Brian M. NEIL, Byron REYNOLDS.
Application Number | 20200359920 16/943647 |
Document ID | / |
Family ID | 1000005001474 |
Filed Date | 2020-11-19 |
United States Patent
Application |
20200359920 |
Kind Code |
A1 |
BURNETT; Daniel R. ; et
al. |
November 19, 2020 |
METHOD AND APPARATUS FOR PRESSURE MEASUREMENT
Abstract
Methods and apparatus for measuring pressure in a patient are
provided which may include any number of features. One feature is a
pressure measurement system comprising a pressure source, a
compliant bladder, a catheter in communication with the pressure
source, pressure sensors, and a controller configured to determine
a pressure within the compliant bladder. The pressure measurement
system can inflate the compliant bladder with gas or air to
determine a pressure within a patient. In one embodiment, the
pressure measurement system measures pressure within a peritoneal
cavity.
Inventors: |
BURNETT; Daniel R.; (San
Francisco, CA) ; REYNOLDS; Byron; (Menlo Park,
CA) ; NEIL; Brian M.; (San Francisco, CA) ;
HALL; Gregory W.; (Los Gatos, CA) ; GUERRA; Paul
B.; (Menlo Park, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Potrero Medical, Inc. |
Hayward |
CA |
US |
|
|
Assignee: |
Potrero Medical, Inc.
Hayward
CA
|
Family ID: |
1000005001474 |
Appl. No.: |
16/943647 |
Filed: |
July 30, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15897002 |
Feb 14, 2018 |
10758135 |
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16943647 |
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15441129 |
Feb 23, 2017 |
9931044 |
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15897002 |
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13809043 |
Apr 1, 2013 |
9622670 |
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PCT/US2011/043570 |
Jul 11, 2011 |
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15441129 |
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61393794 |
Oct 15, 2010 |
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61399298 |
Jul 9, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/14542 20130101;
A61B 5/14539 20130101; A61B 5/036 20130101; A61B 5/412 20130101;
A61M 25/1018 20130101; A61B 5/02055 20130101; A61B 5/20 20130101;
A61B 5/6853 20130101; A61M 2025/0003 20130101; A61B 5/0215
20130101; A61B 5/14546 20130101; A61B 5/205 20130101 |
International
Class: |
A61B 5/03 20060101
A61B005/03; A61B 5/20 20060101 A61B005/20; A61B 5/00 20060101
A61B005/00 |
Claims
1.-2. (canceled)
3. A method of monitoring a fluid from a patient, comprising:
detecting when a catheter is connected to a controller; receiving
the fluid through the catheter when the catheter is positioned
within a patient body, wherein the fluid is received within a
reservoir which is in fluid communication with the catheter;
sensing a volume of the fluid received within the reservoir;
emptying the reservoir automatically when the fluid within the
reservoir reaches a predetermined volume; and determining via the
controller a cumulative total volume of the fluid received from the
patient body.
4. The method of claim 3 wherein the fluid is received within the
reservoir which comprises a rigid cassette.
5. The method of claim 3 wherein emptying the reservoir comprises
actuating a valve to open such that the fluid within the reservoir
is removed upon reaching the predetermined volume.
6. The method of claim 3 further comprising tracking via the
controller a fluid output rate received from the patient body.
7. The method of claim 6 further comprising displaying the fluid
output rate.
8. The method of claim 3 further comprising inflating a pressure
sensing membrane disposed on the catheter prior to receiving the
fluid through the catheter.
9. The method of claim 8 further comprising executing a priming
sequence prior to sensing a pressure of the fluid, the priming
sequence comprising: commanding a pressure source to fill the
pressure sensing membrane with a first volume of fluid; and after
filling the pressure sensing membrane with the first volume of
fluid, commanding the pressure source to remove a second volume of
fluid from the pressure sensing membrane.
10. The method of claim 9 further comprise periodically repeating
the priming sequence to ensure accurate pressure measurements.
11. The method of claim 10 further comprising identifying drift in
a pressure signal.
12. The method of claim 8 further comprising measuring a pressure
of the pressure sensing membrane with a pressure sensor in
communication with the pressure sensing membrane and with the
controller to determine a pressure within the patient.
13. The method of claim 8 further comprising anchoring the catheter
within the patient via a retention balloon prior to inflating the
pressure sensing membrane.
14. The method of claim 8 further comprising removing a volume of
gas from the pressure sensing membrane.
15. The method of claim 14 wherein removing the volume of gas
further comprises opening the pressure sensing membrane to a lower
pressure for a period of time to remove the gas from the pressure
sensing membrane.
16. The method of claim 8 wherein inflating further comprises
inserting the catheter into a peritoneal cavity of the patient.
17. The method of claim 8 wherein inflating further comprises
inserting the catheter into a stomach of the patient.
18. The method of claim 8 wherein inflating further comprises
inserting the catheter into a urinary tract of the patient.
19. The method of claim 3 wherein the catheter is configured to
wirelessly communicate with the controller.
20. The method of claim 3 wherein the catheter is configured to
convey identification information about the catheter to the
controller.
21. The method of claim 3 wherein the catheter is configured to
provide tactile feedback when connected to the controller.
22. A catheter system, comprising: a catheter configured for
anchoring within a patient body; a reservoir which is in fluid
communication with the catheter; a sensor in communication with the
reservoir and with the controller, wherein the sensor is configured
to detect a volume of the fluid within the reservoir; a controller
configured to detect when the catheter is connected to the
controller and which is further configured to actuate the reservoir
to empty automatically when the fluid within the reservoir reaches
a predetermined volume.
23. The system of claim 22 wherein the reservoir comprises a rigid
cassette.
24. The system of claim 22 further comprising a valve in
communication with the controller, wherein the controller is
configured to actuate the valve to open to empty the reservoir.
25. The system of claim 22 wherein the controller is further
configured to track a fluid output rate received from the patient
body.
26. The system of claim 25 wherein the controller is further
configured to display the fluid output rate.
27. The system of claim 22 further comprising a pressure sensing
membrane disposed on the catheter for detecting a fluid
pressure.
28. The system of claim 27 further comprising a pressure sensor
coupled to the pressure sensing membrane, wherein the pressure
sensor is configured to receive a pressure signal from the pressure
sensing membrane.
29. The system of claim 27 further comprising a pressure source
coupled to the pressure sensing membrane.
30. The system of claim 29 wherein the controller is configured to
control the pressure source to control a flow of fluid from the
pressure sensing membrane.
31. The system of claim 27 wherein the pressure sensing membrane
comprises a pressure sensing balloon.
32. The system of claim 27 wherein the controller is programmed
with instructions to execute a priming sequence, the instructions
comprising: commanding a pressure source to fill the pressure
sensing membrane with a first volume of fluid; and after filling
the pressure sensing membrane with the first volume of fluid,
commanding the pressure source to remove a second volume of fluid
from the pressure sensing membrane.
33. The system of claim 32 wherein the instructions further
comprise periodically repeating the priming sequence to ensure
accurate pressure measurements.
34. The system of claim 32 wherein the controller is programmed
with instructions to execute a leak test sequence, the instructions
comprising identifying drift in the pressure signal.
35. The system of claim 22 wherein the controller is further
configured to collect identifying information from the
catheter.
36. The system of claim 22 wherein the catheter is configured to
wirelessly communicate with the controller.
37. The system of claim 22 wherein the catheter is configured to
provide tactile feedback when connected to the controller.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/897,002 filed Feb. 14, 2018, which is a
continuation of U.S. patent application Ser. No. 15/441,129 filed
Feb. 23, 2017, (now U.S. Pat. No. 9,931,044 issued Apr. 3, 2018),
which is a continuation of U.S. patent application Ser. No.
13/809,043 filed Apr. 1, 2013 (now U.S. Pat. No. 9,622,670 issued
Apr. 18, 2017), which claims the benefit under 35 U.S.C. 371 of
PCT/US2011/043570 filed Jul. 11, 2011, which claims the benefit
under 35 U.S.C. 119 of U.S. Provisional Patent Application. No.
61/399,298 filed Jul. 9, 2010, and U.S. Provisional Patent
Application No. 61/393,794, filed Oct. 15, 2010. These applications
are herein incorporated by reference in their entirety.
INCORPORATION BY REFERENCE
[0002] All publications, including patents and patent applications,
mentioned in this specification are herein incorporated by
reference in their entirety to the same extent as if each
individual publication was specifically and individually indicated
to be incorporated by reference.
FIELD OF THE INVENTION
[0003] The present invention generally relates to measuring
pressure within a patient. More specifically, the present invention
relates to measuring pressure within cavities and lumens of a
patient with an air capsule.
BACKGROUND
[0004] Hypothermia has been shown to provide distinct medical
benefits to stroke and cardiac arrest patients by limiting the size
of the infarction and related tissue injury if initiated soon
enough and if the level of cooling is significant enough. Both of
these limitations, initiation of and depth of cooling, have made
practical application of the technology quite challenging
particularly in an ambulance or other emergency settings in the
field. Initiation of cooling, for example, is a major issue since
most technologies require sophisticated machinery that would be
difficult to place in ambulance so the patient, at best, receives
the hypothermic benefit some time after they reach the hospital. Of
the technologies that can be initiated in the field, though, such
as cooling blankets, cooling caps, etc., the depth of cooling is a
major issue due to surface area limitations, complications (such as
intense shivering response) and patient access issues (once the
blanket is on, it may be difficult to access the patient).
[0005] Infusion of a hypothermic fluid into a patient, such as into
a patient cavity such as the peritoneal cavity, adds additional
challenges. The infusion of a large volume of fluid into the
patient cavity can increase pressure inside the cavity. High
pressures inside the peritoneal cavity can cause problems for the
patient, putting the patient's health and well being at risk.
Obtaining an accurate measurement of the pressure within the
patient can be very difficult in hypothermia applications but is
necessary to insure the safety of the patient. Access to the
cavity, changing volumes of fluid in the cavity, patient movement,
and organs within the cavity all provide challenges for accurate
pressure measurement within the patient.
[0006] Thus, there exists a need for improved devices for rapidly
producing hypothermia to treat stroke, severe cardiac events and
related conditions, particularly in the ability to accurately and
easily measure pressure within the patient.
SUMMARY OF THE DISCLOSURE
[0007] In one embodiment, a pressure measurement system is
provided, comprising a catheter, a pressure lumen disposed in the
catheter and coupled to a pressure source, a compliant bladder
disposed on the catheter, the compliant bladder being in
communication with the pressure lumen, a pressure sensor coupled to
the pressure lumen and configured to receive a pressure signal from
the compliant bladder via the pressure lumen, and a controller
configured to receive the pressure signal from the pressure sensor
and to control the pressure source to fill the compliant bladder
with a volume of gas.
[0008] In some embodiments, the controller is configured to execute
a priming sequence comprising commanding the pressure source to
fill the compliant bladder with a first volume of gas, and after
filling the compliant bladder with the first volume of gas,
commanding the pressure source to remove a second volume of gas
from the compliant bladder so the complaint bladder becomes
partially-filled.
[0009] In another embodiment, the controller is configured to
execute a priming sequence comprising commanding the pressure
source to fill the compliant bladder with gas until the complaint
bladder reaches a first pressure, and after reaching the first
pressure, commanding the pressure source to remove a first volume
of gas from the compliant bladder so the complaint bladder becomes
partially-filled.
[0010] In an additional embodiment, the controller is configured to
execute a priming sequence comprising commanding the pressure
source to fill the compliant bladder with gas until the complaint
bladder reaches a first pressure, and after reaching the first
pressure, opening the pressure source to atmospheric pressure for a
first amount of time to remove gas from the compliant bladder until
the complaint bladder becomes partially-filled.
[0011] In some embodiments, the catheter further comprises a fluid
infusion lumen and a fluid extraction lumen. In other embodiments,
the pressure lumen is disposed in a divider between the fluid
infusion lumen and the fluid extraction lumen. In additional
embodiments, the pressure lumen is disposed in an interior wall of
the catheter.
[0012] In one embodiment, a divider between the fluid infusion
lumen and the fluid extraction lumen includes ridges to prevent
total obstruction of fluid flow in the fluid infusion and
extraction lumens during bending or kinking. In another embodiment,
the pressure lumen is free floating in the fluid infusion
lumen.
[0013] In some embodiments, the system further comprises a second
pressure lumen coupled to the pressure source and in communication
with the compliant bladder. In one embodiment, the pressure lumen
and the second pressure lumen are disposed on opposing sides of the
catheter.
[0014] In some embodiments, the pressure lumen is disposed in an
asymmetric wall of the catheter.
[0015] In one embodiment, the catheter includes four-extrusions
connected end to end, wherein a first extrusion comprises the
pressure lumen, and wherein a second, third, and fourth extrusion
comprise infusion and extraction lumens. In one embodiment, the
infusion lumen occupies approximately one-third of a
cross-sectional volume of the catheter.
[0016] In some embodiments, the controller is configured to
periodically repeat the priming method steps of filling the
compliant bladder, then removing air or gas from the bladder until
the bladder is partially-filled, to ensure accurate pressure
measurements.
[0017] Another embodiment further comprises at least one
displacement balloon in close proximity to the compliant bladder,
the at least one displacement balloon configured to form a void
around the compliant bladder.
[0018] A method of measuring pressure in a patient is also
provided, comprising inserting a pressure measurement catheter into
a patient, inflating a compliant bladder of the pressure
measurement catheter with gas from a pressure source coupled to the
compliant bladder, after the inflating step, removing gas from the
compliant bladder so the compliant bladder is partially-inflated,
and measuring a pressure of the compliant bladder with a pressure
sensor coupled to the compliant bladder to determine a pressure
within the patient.
[0019] In one embodiment, the removing gas step further comprises
removing a predetermined volume of gas from the compliant bladder.
In another embodiment, the removing gas step further comprises
opening the compliant bladder to a lower pressure for a period of
time to remove gas from the compliant balloon. In some embodiments,
the lower pressure is atmospheric pressure.
[0020] In one embodiment, the inflating step comprises inflating
the compliant bladder with a first volume of air. In another
embodiment, the inflating step comprises inflating the compliant
bladder to a preset pressure.
[0021] In yet another embodiment, the inserting step comprises
inserting the pressure measurement catheter into a peritoneal
cavity of the patient. In some embodiments, the inserting step
comprises inserting the pressure measurement catheter into a
stomach of the patient. In one embodiment, the inserting step
comprises inserting the pressure measurement catheter into a
urinary tract of the patient.
[0022] Some embodiments of the method further comprise infusing a
fluid into the patient through an infusion lumen of the pressure
measurement catheter. The method can further comprise extracting
fluid from the patient through an extraction lumen of the pressure
measurement catheter.
[0023] In some embodiments, the infusing step comprises infusing a
hypothermic fluid into the patient. A method of measuring pressure
in a patient receiving therapeutic hypothermia is provided,
comprising, inserting a catheter into a peritoneal cavity of the
patient, infusing a hypothermic fluid into the patient to achieve
therapeutic hypothermia, and measuring a pressure of the peritoneal
cavity with an air-filled pressure measurement balloon of the
catheter.
[0024] A method of measuring pressure in a patient receiving
therapeutic hypothermia is provided, comprising, inserting a
catheter into a peritoneal cavity of the patient, infusing a
hypothermic fluid into the patient to achieve therapeutic
hypothermia, and measuring a pressure of the peritoneal cavity with
an air-filled pressure measurement balloon of the catheter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is one embodiment of a pressure measurement
system.
[0026] FIGS. 2A-2J illustrate various embodiments of a pressure
measurement catheter.
[0027] FIG. 3 is another embodiment of a pressure measurement
system.
[0028] FIG. 4 is one embodiment of a pressure measurement system
with displacement balloons adjacent to or in close proximity to a
measurement balloon.
[0029] FIG. 5 is one embodiment of a Foley-style pressure
measurement system.
[0030] FIG. 6 this figure illustrates the function of the urine
output measuring embodiment of the device.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0031] Devices and methods for measuring pressure are disclosed.
More specifically, some embodiments of the present disclosure
describe devices and methods for measuring pressure within a
patient with a compliant gas-filled bladder or balloon. The
compliant gas-filled balloon can be coupled to a gas-filled column
located within, for example, a catheter, to measure the pressure
inside of patient cavities, organs, lumens, etc.
[0032] The present invention overcomes the limitations of the prior
art through the use of an air bladder in conjunction with an
automated controller to ensure that the volume of air required to
perform accurate pressure measurements is maintained within the air
capsule.
[0033] FIG. 1 illustrates one embodiment of a pressure measurement
system 100, comprising a compliant balloon 102, catheter 104, a
pressure line within the catheter (not shown), pressure sensors
106, pressure source 108, and controller 110. The pressure
measurement system 100 can be configured to be inserted into a
patient to measure a pressure within the patient. In some
embodiments, the system is sized and configured to measure pressure
within patient cavities, organs, or lumens. In one embodiment, the
system is sized and configured to measure a pressure within the
peritoneal cavity of a patient. In another embodiment, the system
is sized and configured to measure a pressure within the urinary
tract of the patient, such as within the bladder or urethra. In
another embodiment, the pressure measurement balloon is inserted
into the stomach of the patient.
[0034] The compliant balloon 102 may comprise any compliant
material. Within this disclosure, the compliant balloon may be
referred to as a balloon, bladder, membrane, or other similar term.
The balloon can comprise any compliant, flexible, non-porous
material configured to expand or retract with inflation and
deflation of a gas or fluid. The balloon 102 may comprise a
thermoset or thermoplastic polymer, silicon, latex, or any other
compliant material used in medical balloon applications, for
example. In some embodiments, "rigid" polymers can be beneficial
for pressure measurement applications. In some embodiments, the
balloon that can be collapsed for insertion and removal. In one
embodiment, the balloon may be tacked down by folding and setting
of the balloon or through application of vacuum to collapse the
balloon radially. Alternatively, the tip of the balloon may
reversibly engage the tip of the catheter and may disengage during
air inflation of the capsule.
[0035] An important feature is for the balloon to have a sufficient
volume for a pressure measurement application. Sufficiency of the
volume of the balloon is determined by the ratio of the pressure
line volume to the balloon volume. In some embodiments, the volume
of the balloon at least 15% of the total volume in the pressure
lines. In one embodiment, the volume of the balloon is
approximately 8-12 cc and the volume of the pressure lines is
approximately 11-16 cc, however larger volumes may provide less
sensitivity to fill volume.
[0036] Referring still to FIG. 1, one or more balloons 102 may be
used in the pressure measurement system. In the illustrated
embodiment, the balloon is positioned at a distal end of the
catheter 104. However, in other embodiments, the balloon may be
located at any location along the length of the catheter, so long
as it can be positioned within the patient to collect pressure
information. The balloon 102 may be any shape, such as spherical,
ribbed, elongated, or with splines. An elongated balloon is
preferred because it can have a large volume but still groom or
deflate down to a small diameter for placement into the patient and
removal from the patient. In some embodiments, the balloon can have
a length of approximately 4-8 cm. The balloon may inflate to a
diameter of approximately 1-3 cm in a pressure measuring
configuration, and may deflate down to a total diameter of
approximately 0.1-1 cm in a delivery configuration. It should be
noted that, in the delivery configuration, the balloon diameter is
limited to the size of the catheter being used.
[0037] The balloon may also be asymmetric in a way that it expands
preferentially on the side of the catheter, aligning with holes for
air communication. This helps ensure that the balloon will not
interfere with other functions of the catheter which may occur on
the opposite side of the catheter, such as fluid flow, temperature
measurement, or optical or ultrasound assessment of surrounding
tissues.
[0038] Catheter 104 can include an independent pressure lumen for
communication between the balloon 102 and pressure sensors 106. The
pressure lumen is not illustrated in FIG. 1 as it is disposed
within the catheter, but will be illustrated and described in more
detail below. The pressure lumen couples the balloon 102 to
pressure sensors 106, providing an air/gas column between the
balloon and the sensors. The catheter 104 can further include fluid
infusion and/or extraction lumens for delivering fluid to a patient
and/or removing fluid from the patient. In some embodiments, the
catheter can include separate infusion and extraction lumens. Each
of the infusion and extraction lumens may further include infusion
and extraction ports positioned at specified points along the
catheter, to allow for communication between the
infusion/extraction lumens and the outside of the catheter. Further
details on a catheter system with suitable infusion and extraction
lumens and ports are described in U.S. pat. appln. Ser. No.
12/702,165, titled "Method and Apparatus for Inducing Therapeutic
Hypothermia," filed Feb. 8, 2010.
[0039] The catheter may have features to aid in correct depth
setting of the pressure sensing balloon including, a retention
balloon 105 proximal to the balloon 104 that can be used as an
anchor to the inside of the patient. In another embodiment, a bend
in the catheter proximal to the balloon 104 that can be configured
to anchor the catheter inside the cavity. The bend may be flexible
enough to pass through an access port (not shown) but offer enough
resistance to straightening to allow the user to feel the bend
against the inside of the patient when applying a removing force to
the catheter.
[0040] In some embodiments, the connection between the catheter and
the remainder of the system is done with a single motion. The user
can push the catheter into a receiving end until they reach a
certain force or until there is audible (click) or tactile
feedback. Tactile feedback may be provided by a detent feature,
such as a swaged extrusion passing by an O-ring, or by a feature
bottoming out into a tapered shaft.
[0041] The catheter connection may also complete an electrical
circuit or press a button, allowing the controller 110 to know that
the catheter has been connected. The connection may have a resistor
of a particular value to indicate an identifying piece of
information such as lot#, model#, or calibration. In other
embodiments, the catheter may also have an RFID chip in it to
convey information to the controller 110 about information such as
lot#, model#, or calibration. In other embodiments, the catheter
may have a fuse or other feature that can be disabled at the end of
treatment for identification of used devices.
[0042] FIG. 2A is one embodiment of a cross sectional view of
catheter 204, which can be catheter 104 of system 100 in FIG. 1. In
FIG. 2A, the interior of catheter 204 can comprise pressure lumen
212. The pressure lumen may connect to the controller and/or
pressure sensors as an individual connection (e.g., luer
connection) or as part of a step that connects multiple
connections, fluid and/or electrical to the controller and/or
pressure sensors. For applications in which the pressure lumen and
balloon are filled with air, the pressure lumen can be as small as
0.024'' ID and function as required. FIG. 2B is another embodiment
of catheter 204 and pressure lumen 212. In FIG. 2B, the pressure
lumen does not occupy the whole interior of the catheter, but
rather, is its own separate lumen. The embodiment of FIG. 2B shows
the pressure lumen 212 being disposed off-center within the
catheter. However, in other embodiments, the pressure lumen can be
disposed in the center of the catheter, or even positioned adjacent
to the interior wall of the catheter. In some embodiments, the
pressure lumen may be floating within an already-existing lumen of
the catheter.
[0043] In some embodiments, the pressure lumen may be part of a
multi-lumen extrusion within the catheter of the pressure
measurement system. As described above, one or more of these lumens
may be used for infusion or extraction of fluids to and from a
patient. In the embodiment of FIG. 2C, catheter 204 can include
infusion lumen 214 and extraction lumen 216. The pressure lumen 212
can be disposed within either of the lumens. In FIG. 2C, the
pressure lumen 212 is shown as a floating lumen within the infusion
lumen 214. The lumens can be separated by a divider 218, of any
desired thickness. For example, a thicker divider 218 may increase
the cross-sectional strength of the catheter, increasing bend or
kink resistance, at the expense of reducing the total volume of
fluid that can be infused/extracted by the catheter.
[0044] FIG. 2D illustrates an embodiment where the pressure lumen
212 is embedded inside a wall 220 of the catheter. FIG. 2E
illustrates an embodiment where the pressure lumen is embedded
inside the divider 218 of the catheter. In the embodiment of FIG.
2E, positioning the pressure lumen in the center of the catheter
allows the catheter to flex symmetrically during use, and provides
for some kink protection because the central location of the
pressure lumen holds the infusion and extraction lumens at least
partially open during flexure.
[0045] FIG. 2F illustrates yet another embodiment, wherein the
pressure lumen 212 is embedded inside of wall 220 of the catheter,
and the divider 218 includes ridges 222 to prevent total
obstruction of flow within the infusion/extraction lumens during
bending or kinking.
[0046] In FIG. 2G, the catheter includes two pressure lumens 212
for pressure measurement redundancy. Both pressure lumens may be
disposed in exterior walls of the catheter, as shown. In some
embodiments, the pressure lumens can be positioned across from
another in the catheter, for example, spaced 180 degrees apart.
This can allow the catheter to bend uniformly. In this embodiment,
the dual pressure lumens can also serve to prevent total occlusion
of the flow path in the infusion or extraction lumens 214 and 216
during bending or kinking. The dual pressure lumens may communicate
with the same pressure measurement balloon, or separate balloons
located on opposite sides are at different locations along the
length of the catheter.
[0047] In another embodiment, as shown in FIG. 2H, the pressure
lumen 212 can be disposed in an asymmetric wall 224. This design
allows for formation of a large extraction lumen 216 (relative to
the infusion lumen 214). In some embodiments, a reinforcing
structure, such as a coil or other device, can be used in the
extraction lumen or within the walls of the catheter to aid in
preventing kinking.
[0048] In FIG. 2I, the catheter 204 can include four extrusions to
provide for excellent kink resistance without needing to add a
separate kink-reducing structural component. In this embodiment,
the two lower extrusions can be used as extraction lumens 216, and
the upper right extrusion can be infusion lumen 214. The final
extrusion can be used as the pressure lumen 212. In the illustrated
embodiment, the infusion lumen 214 occupies approximately
120degrees of the catheter, and the pressure lumen occupies
approximately 60 degrees of the catheter.
[0049] In the embodiment of FIG. 2J, the infusion lumen 214 can be
a round lumen, the extraction lumen 216 can wrap around the
infusion lumen, and the pressure lumen can be disposed in the wall
of the catheter 204 next to the extraction lumen. This embodiment
also provides for excellent kink resistance while allowing for
efficient fluid infusion and removal.
[0050] In some embodiments, the pressure lumen comprises a
different material than the rest of the catheter. While it is often
desirable for the catheter to be flexible, in some embodiments, the
pressure lumen can be made out of a more rigid material, or the
infusion or extraction lumens may have a braided material in the
wall (stainless steel for example) to make the catheter wall
stiffer. This stiffness aids in the prevention of kinking and
isolates the pressure signal from pressure in the other lumens of
the catheter. Depending on the relationship in volume between the
pressure lumen and the measurement balloon, this level of isolation
may not be necessary because the lumen wall deflection may create
negligible volume change.
[0051] In the embodiments described above, the ratio of cross
sectional area between the infusion lumen and the extraction lumen
can vary from 1:1 to 1:2, respectively, but other ratios can also
be used. Also, in any of the embodiments described above, the
catheter or even the individual lumens can include anti-kinking
devices, including but not limited to a structure within one or
more of the catheter lumens or walls such as a coil, a braid, or an
extrusion in a V, Y, or + shape.
[0052] In some embodiments, the catheter can be designed in a way
that enables it to groom down in the region of the balloon to a
smaller diameter to allow for fitment of an access port over the
catheter. In one embodiment, the catheter grooms down to fit
through a 5 access port. In one embodiment, the catheter necks down
to a smaller outer diameter distal to the end of the infusion
lumen. The balloon can then reside distal to the termination of the
infusion lumen. In some embodiments, the catheter may have three
lumens on the proximal end (e.g., infusion, extraction, and
pressure), but reduce the number of lumens along its length. For
example, after the infusion holes, the infusion lumen could end.
After the pressure lumens/balloon, the pressure lumen could end.
This can be accomplished with stop-lumen extrusion technology, by
reflow of extrusion material, or by butt-joining different
extrusion designs to each other.
[0053] Referring back to FIG. 1, the system 100 can further include
one or more pressure sensors 106. The pressure sensor(s) 106 can be
any type of pressure sensor configured to measure air or fluid
pressure, as known in the art. In some embodiments, a pressure
sensor is included inside controller 110, however they are
described and illustrated separately in this disclosure to ease in
the description. The pressure sensors may be reusable or
disposable. In one embodiment, the sensors are a reusable component
in the controller. The advantage of using pressure sensors coupled
to the pressure lumen and balloon with air is that the sensors can
be at a different elevation than the balloon without having an
offset in the pressure signal, owing to the negligible density of
air. During a medical procedure in which a catheter is inserted
into a patient and the balloon is not visible, more accurate
pressure measurements can be made without having to worry about
aligning the elevation of external pressure sensors with a
(sometimes unknown) balloon depth.
[0054] Temperature compensation to account for differences in
temperature between the pressure sensor location and the balloon
location has not been found to be necessary in the pressures and
temperatures for therapeutic hypothermia with peritoneal lavage.
However in some embodiments, for added accuracy, temperature can be
measured in the catheter in the vicinity of the balloon with a
temperature sensor (thermistor, thermocouple, optical sensor,
etc.).
[0055] Referring still to FIG. 1, the system 100 can also include a
pressure source 108 to provide gas or air pressure to the pressure
lumen and balloon. In some embodiments, the pressure source is a
manual pressure source, such as a syringe or bellows. In other
embodiments, the pressure source is automated, such as a pump. Any
kind of automated pump can be used to move gas, air, or fluid into
the pressure lumen and balloon, such as a diaphragm, syringe, gear,
bellows, peristaltic pump, etc. In other embodiments, a compressed
air supply, such as in a hospital, can be used to fill the pressure
lumen and balloon with air.
[0056] When air is the material used to fill the balloon, the
design may have great sensitivity to the presence of fluid
contaminants in the pressure measurement lumen. With small diameter
pressure lumens, the surface tension of fluid can prevent small
volumes of fluid from moving within the lumen thereby damping,
diminishing, or even eliminating a pressure signal from reaching
the external sensors. Thus, various embodiments can mitigate
against fluid blockage of the pressure lumen. In one embodiment,
the pressure lumen can be lined with a hydrophobic material that
will reduce the attraction between an undesired fluid and the
pressure lumen wall. In another embodiment, the addition of a
surfactant or similar chemical can reduce the surface tension of
the fluid in the pressure lumen. In another embodiment, a
hydrophilic fiber can be disposed within the pressure lumen. The
hydrophilic fiber can have a smaller diameter than that of the
pressure lumen, so gas or air can still travel along the pressure
lumen. Fluid will be attracted to the fiber and be less likely to
wet the walls of the pressure lumen, thereby leaving space for the
pressure signal to travel. In one embodiment, if the hydrophilic
fiber becomes saturated with fluid, the system can include an
indicator or a circuit coupled to the control system to alert that
the fiber is full. For example, a saturated fiber could close a
circuit to set off an alarm in the control system, or
alternatively, the fiber could change color when saturated and be
checked occasionally by a medical worker (e.g., a nurse). In
another embodiment, the pressure lumen can include a combination of
a wick and hydrophobic coating on the inner wall of the lumen.
[0057] In yet another embodiment, the pressure lumen may be
hydrophobic and have an irregular cross-section involving one or
more projections in one or more directions. This irregular lumen
will be resistant to obstruction by water droplets which will want
to form spherical bodies based on the properties of the surface
tension of water in the presence of a hydrophobic material. With
droplets forming in the center of the lumen, said projections will
resist obstruction and provide a continuous air channel from
proximal end to the distal end of the catheter. Obstruction by a
fluid formation in the catheter may also be prevented by the use of
intermittent evacuation of the balloon and pressure lumen. This
method may be used on its own or in conjunction with any of the
other embodiments outlined above and entails intermittently
evacuation the balloon and the pressure lumen to remove fluid
excess into a proximal fluid collection reservoir or water
scavenger. In combination with the automated balloon priming to
appropriately refill the balloon, this feature will allow for
intermittent removal of accumulated water which, if not removed,
could potentially overwhelm the lumen.
[0058] Additional solutions to this issue of fluid in the pressure
lumen are disclosed. In one embodiment, a pump can move air through
the pressure lumen at all times that the catheter is disconnected
to keep the pressure lumen free of fluid. In another embodiment,
the catheter includes separate pressure lumen and infusion lumen
connectors, rather than a single connection that connects to the
rest of the system with a single motion. In another embodiment, the
pressure lumen can have a sleeve, sheath, cap, or other protective
mechanism over the proximal end of the pressure lumen that is
configured to slide out of the way upon connection to the rest of
the system. In one embodiment, a cap can be spring loaded so as to
engage whenever the pressure lumen is disconnected from the system.
In another embodiment, a stylet can be placed in the pressure lumen
of the catheter and be removed just prior to connection with the
system.
[0059] In FIG. 1, the system further includes a controller 110. In
many embodiments, the controller can be configured to automatically
control one or more parameters related to pressure measurement,
calibration, and infusion or extraction of fluid to and from a
patient. It should be appreciated that controller 110 can also be
configured to perform a variety of operations including
communicating with external devices including devices linked over
the Internet; wireless peripheral devices; data operations; and
various power management functions.
[0060] Controller 110 can include one or both of analog or digital
circuitry for performing its control operations. The controller
will also typically be configured to receive one or more inputs,
such as from pressure sensors 106. Typically, the controller will
include a computer processor which is configured to execute one or
more electronic instruction sets contained within a software
module, which can be stored in memory onboard the controller.
Additionally, controller 110 can be configured to be programmed by
the user (e.g., using a user interface or by an external device
such as a wireless device) to allow for manual control of one or
more operations of the system (e.g., infusion rate, extraction
rate, pressure line calibration, etc).
[0061] Methods of measuring pressure with the systems described
herein will now be described, with reference to FIGS. 1 and 3. The
pressure measurement system of FIG. 1, particularly balloon 102,
catheter 104, pressure sensors 106, pressure source 108, and
controller 110, can correspond to balloon 302, catheter 304,
pressure sensors 306, pressure source 308, and controller 310 of
FIG. 3. In one embodiment, pressure sensors 306 can be zeroed to
atmospheric pressure while the system is in a standby mode, before
use. Next, the catheter 304 can be placed into a space within the
patient P for which a pressure measurement is desired with the aid
of an access device. After removal of the access device, the
catheter can be connected to the controller 310 and/or pressure
sensors 306. In some embodiments, as described above, the
controller is configured to automatically detect when the catheter
is connected to the controller.
[0062] In one embodiment, upon connection of the catheter, the
controller can close a first valve 326 disposed between the
pressure source 308 (e.g., a pump) and the catheter 304, isolating
the pressure source 308 from the catheter 304. In one optional
embodiment, the system can evacuate the balloon and pressure lumen
prior to closing the first valve. The controller can then open a
second valve 328 disposed between the pressure source and the
outside to open the pressure source up to atmosphere and enable the
pressure source to fill with atmospheric air. Once the pressure
source is filled with air, the first valve can open to connect the
pressure source and catheter again.
[0063] Next, the pressure source can fill the pressure lumen of the
catheter and balloon 302 with air/gas. In some embodiments, the
controller 310 fills the balloon 302 until the balloon reaches a
specified pressure or volume (based on the volume of the balloon).
In some embodiments, when the specified pressure or volume is
reached it serves as an indicator to the controller that the
balloon is properly coupled to the controller and rest of the
system. In some embodiments, the specified pressure of volume is
the pressure or volume to fully fill the balloon with air/gas.
Thus, in one embodiment, the pressure source fills the pressure
lumen and balloon with air or gas until the balloon is fully
inflated.
[0064] In one embodiment, the controller can pause for a set period
of time and perform a leak test to evaluate the system for leaks in
the balloon or catheter connections. The leak test can ensure that
the balloon is viable and ready for use in pressure measurement.
The leak test can determine that the balloon is leak free based on
expected pressure and/or volume characteristics.
[0065] Next, in one embodiment, the controller can remove a
predetermined amount of air or gas from the balloon 302 to make the
balloon partially-filled. The amount of gas/air removed from the
balloon can be pressure-controlled or volume-controlled. In one
embodiment, a bellows pump displaces a fixed amount to remove a
fixed volume of air from the balloon. Additionally, the removal of
air or gas from the balloon can be time based, for example the
balloon could be vented to atmospheric pressure for a specified
amount of time (e.g., for fractions of seconds to seconds).
Finally, once the proper amount of gas or air is in the balloon and
pressure lumen, the first valve 326 between the pressure source 308
and the catheter 304 can be closed, rendering the system 300 ready
for pressure measurement. Even with bellows/syringe type pumps,
closing the first valve is beneficial because it decreases the air
volume of the sensing system, making the pressure in the system
more sensitive to changes in the catheter balloon.
[0066] During use, the controller 310 may periodically evaluate the
balloon 302 and the catheter connections by refilling the balloon
to a set pressure. Additionally, the controller can perform a leak
test prior to using the system for a pressure measurement by
observing the air pressure signal for drift. Retesting the system
is very useful in long procedures, where there is potential for
manipulation and/or damage to the catheter between pressure
measurements.
[0067] In some embodiments, the controller can automatically
maintain a desired pressure or volume in the balloon 302. As with
any air or gas filled balloon, air loss or pressure loss can always
be a problem. However, this air or pressure loss is unpredictable
and can vary based on the environment and type of procedure in
which the balloon is used. The present system can overcome this
limitation by intermittently filling the balloon 302 to a desired
pressure or volume of gas/air. In some embodiments, after filling
to the desired volume or pressure, the controller can automatically
remove a specified amount of gas or air from the balloon to make
the balloon partially-filled or more compliant. In another
embodiment, the controller can completely evacuate the balloon at
specified intervals during a procedure, then fill the balloon to
the optimal pressure or volume or the leak test pressure or volume
in the manner described above.
[0068] The controller may also test the connection between the
balloon and the pressure sensor by analyzing the pressure signal
for the pressure cycles associated with patient respirations. If
the balloon was not inflated or was over-inflated, these
respirations would not be evident. Respiration and patient activity
can create variations in pressure with magnitudes up to 100 mmHg
(coughs). Air pressure signals occur when the balloon has a nominal
amount of air in it and that volume can compress and expand in
response to changes in surrounding pressure. If a balloon is
under-inflated, the baseline pressure of the cavity may be
sufficient to collapse the volume of air in the balloon,
eliminating the air/gas pressure signal since no further
compression of the air/gas can take place. A similar problem occurs
if the catheter balloon is over inflated. Cavity pressures and
fluctuations below the catheter balloon pressure will not affect
the pressure in the balloon and thus go un-measured. For example,
if the catheter balloon was inflated to 200 mmHg, the 100 mmHg
pressure from a cough would not compress the catheter balloon and
generate a pressure signal.
[0069] The system may have an expected range of volumes of air that
are required to fill the balloon. This information can be used to
detect whether or not there is a kink in the line between the
sensors and the balloon. For example, if pressure readings from the
pressure sensors indicate that the pressure in the balloon is at
the expected value, but a lower volume of air or gas was filled in
the balloon to attain that value, then the controller can determine
that there is a kink in the pressure lumen.
[0070] Referring again to FIGS. 1, FIGS. 2A-2J, and FIG. 3, in one
embodiment the catheter of the present disclosure may be used in
methods to measure pressure in a patient while inducing and
maintaining therapeutic hypothermia in the patient. While this
disclosure is directed to the pressure measurement aspect of the
procedure, further details and description regarding the
therapeutic hypothermia aspect of the procedure may be found in the
U.S. pat. appln. Ser. No. 12/702,165 referenced above.
[0071] In a first step of the method, the catheter is inserted into
a peritoneal cavity of a patient. Next, the cavity pressure
measurement catheter is connected to the controller 108, primed,
and made ready to measure pressure in the manner described above.
Specifically, the pressure source can fully inflate the balloon
with air or gas, then remove a predetermined volume of fluid from
the balloon until it is partially-inflated. An initial pressure
reading can be taken with the balloon 102 of system 100.
[0072] Next, controller 110 can initiate infusion of a hypothermic
fluid into the peritoneal cavity to induce therapeutic hypothermia
in the patient. As the fluid is being infused into the patient, the
pressure sensors can acquire pressure signals from the pressure
lumen and balloon 102 indicating a pressure within the peritoneal
cavity. In some embodiments, the pressure measurements are taken in
real time. In other embodiments, the pressure measurements are
taken at pre-determined intervals.
[0073] In another embodiment of the pressure measurement system,
referring to FIG. 4, the system can include a mechanism for
protecting the pressure measuring balloon from interference by
foreign objects touching the balloon. In FIG. 4, catheter 404 of
system 400 can further include displacement balloons 430 adjacent
to or in close proximity to pressure measurement balloon 402. After
insertion of the catheter into a patient cavity or lumen,
displacement balloons 430 can be inflated to form a void 432 around
the pressure measurement balloon 402. The balloon can then be
primed and readied for pressure measurement following the steps
listed above. The displacement balloons form a void around the
pressure measurement balloon to protect the balloon from touching
foreign objects, such as organs within a dry patient cavity. One
benefit of the displacement balloons is that they can be deflated
to a small diameter during insertion of the patient so as to be
constrained through the access device.
[0074] Referring now to FIG. 5, in another embodiment, a pressure
measurement system 500 can incorporate a modified Foley catheter
specially configured to measure pressure and other parameters in
the urinary tract, such as within the urethra and/or bladder. As
such, the catheter 504 of FIG. 5 can be sized and configured to be
inserted into the urinary tract of a patient. In FIG. 5, the
catheter 504 can include a balloon 502 coupled to a pressure lumen,
as described above. Additionally, the catheter can include a
retention balloon 505 configured to hold the catheter in place. In
some embodiments, the catheter includes sensors 534 disposed
between the pressure balloon and the retention balloon, the sensors
configured to measure pH, nitrate, oxygen, hemoglobin, and/or
temperature.
[0075] Referring now to FIG. 6, the urine may collect into a small,
disposable reservoir 600 with tubing leading from the bladder to
the reservoir 600 and from the reservoir 600 to the urine
collection bag. The device may incorporate an external pinch valve
capable or other element capable of opening and closing the tube
leading from the reservoir 600 to the urine collection bag. In the
ideal embodiment, the reservoir 600 incorporates a sensor 602 (or
the device incorporates a sensor) that reports once a set volume
has been received (ie 10 mL) and opens the tubing to the collection
bag to dump the urine after which the tubing is again closed. The
boluses of fluid that are dumped from the reservoir 600 can be
reported and/or recorded by the device based on the number of times
that the valve has been opened. This will allow urine output to be
tracked and recorded in an automated manner.
[0076] The device/reservoir interface 604 --allows for closing and
opening of the outflow tubing once a fixed volume has been
collected. May also provide for sensing of the reservoir volume
using sensors 602 within the device at the reservoir interface 604
or within the reservoir 600 itself.
[0077] In alternative embodiments, other portions of the Foley
catheter may be configured to sense one or more of the following
parameters with sensors 536 and 538: urine pH, urine oxygen
content, urine nitrate content, respiratory rate, heart rate,
perfusion pressure of bladder wall and/or urethra, temperature
inside bladder and/or urethra, electrocardiography via sensors on
the bladder wall and/or urethra, respiratory volume, respiratory
pressure, peritoneal pressure, urine glucose, blood glucose via
urethral mucosa and/or bladder mucosa, urine proteins, urine
hemoglobin, blood pressure, and any other physiologic parameter
that can be measure in urine or from the urethra and/or bladder
wall.
[0078] In one embodiment, the catheter can sense a minimum of two
parameters, but may be limited to a single parameter for focused
applications (i.e., respiratory rate in a patient in respiratory
distress). The respiratory rate, relative tidal volume, peritoneal
pressure, heart rate and/or relative cardiac output may be measured
simultaneously, as well, by connecting a balloon with a flaccid
wall or semi-tense wall to an external pressure sensor via a lumen
that may be filled with liquid and/or gas. These parameters may
also be measured, alone or in concert with other parameters,
through the use of pressure measurement modalities other than the
external pressure sensor. These may include: a deflecting membrane
inside of the catheter, MEMs technology, a catheter-based sensor
and/or other embodiments.
[0079] In some embodiments, as well, the catheter may include a
blood pressure sensing element which may take many forms, one of
which involves an inflatable member (either a separate balloon or,
ideally, a balloon in fluid communication with the retention and/or
pressure sensing balloon) which may be optically analyzed as it is
inflated to determine at which pressure the vessels within the
urethra are blanched and blood flow is stopped. This will provide a
highly accurate reading of the perfusion pressure of the urethra
which provides an indication of both overall blood pressure and
vascular resistance. This implantable perfusion pressure device may
be used to provide early detection and/or monitoring of a variety
of disease conditions including sepsis, shock, hemorrhage, etc. and
can usually detect these conditions in the early stages. This
methodology may also be used to detect perfusion pressure in other
areas of the body with an intermittently inflatable member and
optical detection of blood flow and/or presence of blood.
[0080] Other modalities may be used to detect that the tissue has
been blanched, as well, with the critical component being that of
the intermittent inflation within the lumen, body cavity or bodily
tissues to provide the compression of the vasculature. Relative
cardiac output and relative tidal volume may be calculated, as
well, based on the deflection of the pressure sensor and/or other
force gauge. If sampled frequently enough (i.e., 2 Hz or faster),
the respiratory excursion can not only be counted, but they can be
quantified in a relative manner to the amplitude of the excursions
at the time of catheter placement. Larger excursions mean either
heavier breathing or, in the setting of an upward drift in the
baseline, a higher peritoneal pressure. The small peaks on the
oscillating respiratory wave, caused by the pumping heart, may be
tracked as well, and the amplitude of this wave may be used, in the
setting of a relatively constant peritoneal pressure, to determine
the relative cardiac output.
[0081] As for additional details pertinent to the present
invention, materials and manufacturing techniques may be employed
as within the level of those with skill in the relevant art. The
same may hold true with respect to method-based aspects of the
invention in terms of additional acts commonly or logically
employed. Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Likewise, reference to a singular item,
includes the possibility that there are plural of the same items
present. More specifically, as used herein and in the appended
claims, the singular forms "a," "and," "said," and "the" include
plural referents unless the context clearly dictates otherwise. It
is further noted that the claims may be drafted to exclude any
optional element. As such, this statement is intended to serve as
antecedent basis for use of such exclusive terminology as "solely,"
"only" and the like in connection with the recitation of claim
elements, or use of a "negative" limitation. Unless defined
otherwise herein, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. The breadth of
the present invention is not to be limited by the subject
specification, but rather only by the plain meaning of the claim
terms employed.
* * * * *