U.S. patent application number 12/919209 was filed with the patent office on 2011-01-06 for pressure sensing catheter.
This patent application is currently assigned to Robert Hoch. Invention is credited to Robert C. Hoch.
Application Number | 20110004198 12/919209 |
Document ID | / |
Family ID | 41056620 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110004198 |
Kind Code |
A1 |
Hoch; Robert C. |
January 6, 2011 |
Pressure Sensing Catheter
Abstract
A pressure sensing catheter having a proximal end and a distal
end. The proximate end includes one or more leur fittings
contiguous with one or more lumens disposed within the catheter, a
connector coupled to a signal lead which spans the length of the
pressure sensing catheter and a pressure transducer coupled at
about a distal end of the pressure sensing catheter. One or more
apertures are provided at about the distal end of the pressure
sensing catheter to allow infusion of fluids and/or withdrawal of
fluid samples contemporaneous with pressure monitoring within a
blood vessel. Signals sent from the pressure transducer are
converted into vascular pressure units by an electronic monitor
coupled to the signal lead connector.
Inventors: |
Hoch; Robert C.; (Eden
Prairie, MN) |
Correspondence
Address: |
LAW OFFICE OF PHILIP A STEINER
1212 MARSH STREET, SUITE 3
SAN LUIS OBISPO
CA
93401
US
|
Assignee: |
Hoch; Robert
|
Family ID: |
41056620 |
Appl. No.: |
12/919209 |
Filed: |
March 4, 2009 |
PCT Filed: |
March 4, 2009 |
PCT NO: |
PCT/US09/35970 |
371 Date: |
September 25, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61033810 |
Mar 5, 2008 |
|
|
|
61092623 |
Aug 28, 2008 |
|
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Current U.S.
Class: |
604/523 |
Current CPC
Class: |
H02J 3/005 20130101;
A61B 5/412 20130101; A61M 2025/0037 20130101; A61M 2025/0002
20130101; A61M 2205/3331 20130101; H02J 7/00 20130101; A61M
2039/082 20130101; A61M 25/0026 20130101; A61M 2205/3344 20130101;
A61B 5/02152 20130101; H02J 9/00 20130101 |
Class at
Publication: |
604/523 |
International
Class: |
A61M 25/00 20060101
A61M025/00 |
Claims
1. A pressure sensing catheter comprising: a flexible conduit
having a proximal end, a distal end, and a lumen longitudinally
spanning between the proximal and distal ends; the flexible conduit
dimensioned to longitudinally travel within a blood vessel of a
patient such that the distal end is disposed proximate to a
predetermined location within the blood vessel; a pressure
transducer coupled to the flexible conduit at about the distal end
and external to the lumen, the pressure transducer configured to
generate fluid pressure signals when disposed proximate to the
predetermined location within the blood vessel; and, an electronic
monitor coupled to the pressure transducer configured to process
the fluid pressure signals generated by the pressure
transducer.
2. The pressure sensing catheter of claim 1 wherein the flexible
conduit is further dimensioned to allow delivery of a therapeutic
agent into the blood vessel via the lumen.
3. The pressure sensing catheter of claim 2 wherein the flexible
conduit is constructed from a polymeric material having sufficient
elasticity to allow delivery of the therapeutic agent as a bolus or
as a continuous stream.
4. The pressure sensing catheter of claim 1 wherein at least a
portion of the pressure transducer is coaxially encompassed by the
flexible conduit but separate from the lumen.
5. The pressure sensing catheter of claim 1 wherein the flexible
conduit further includes at least one septum which longitudinally
subdivides the lumen into a plurality of lumens.
6. The pressure sensing catheter of claim 1 wherein the pressure
transducer is optically coupled to the electronic monitor.
7. The pressure sensing catheter of claim 1 wherein the
predetermined location is within a superior vena cava or inferior
vena cava of the patient.
8. The pressure sensing catheter of claim 1 wherein at least a
portion of the distal end of the flexible conduit or pressure
transducer is constructed from a material having a property
selected from the group consisting of: an electromagnetic property,
a radiographic opacity property, and a acoustically reflective
property.
9. The pressure sensing catheter of claim 1 wherein the blood
vessel is a vein.
10. The pressure sensing catheter of claim 1 wherein the lumen is
configured to coaxially receive a guide wire.
11. The pressure sensing catheter of claim 1 wherein the pressure
transducer is one of a nano-wire and optoelectric pressure
transducer.
12. The pressure sensing catheter of claim 7 where the at least one
septum is constructed of a polymeric material having sufficient
elasticity to allow lateral expansion and contraction of the
plurality of lumens.
13. The pressure sensing catheter of claim 7 wherein at least two
of the plurality of lumens are configured to allow simultaneous
withdrawal of a fluid sample via one lumen and allow delivery of a
therapeutic agent via a second lumen.
14. The pressure sensing catheter of claim 1 wherein the flexible
conduit is configured to allow fluid pressure measurement proximate
in time with therapeutic agent delivery or fluid sample withdrawal
from the blood vessel of the patient.
15. The pressure sensing catheter of claim 1 wherein the flexible
conduit has a diameter no greater than 12 French.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional application is a national stage patent
application and claims priority under 35 U.S.C. .sctn.371 from
co-pending PCT application PCT/US09/35970 filed Mar. 4, 2009 to a
common inventor and assignee. This non-provisional application also
claims priority under 35 U.S.C. .sctn.119(e) from co-pending
provisional patent applications 61/033,810 filed Mar. 5, 2008
entitled "Catheter" and 61/092,623 filed Aug. 28, 2008 entitled
"Pressure Sensing Catheter," both to a common inventor and
assignee. Provisional applications 61/033,810 and 61/092,623 are
hereby incorporated by reference in their entirety as if fully set
forth herein.
FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
[0002] Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not Applicable
TECHNICAL FIELD
[0004] This application relates to pressure sensing catheters,
particularly for infusing and withdrawing of fluids from a blood
vessel and for measuring fluid pressures within the blood
vessel.
BACKGROUND
[0005] Physicians, healthcare professionals, veterinarians and
researchers may need to establish central venous vascular access
for the purpose of monitoring a patient or subject's central venous
pressure (CVP), while simultaneously administering medication,
hydration fluids, nutrients, radiologic contrasts, or other fluids.
There are numerous clinical indications for blood withdrawal which
can be facilitated by a central venous catheter. Knowledge of CVP
is useful in the management of several disease states and injuries,
including but not limited to shock, acute renal failure,
hypotension, congestive heart failure, cerebral trauma, and spinal
cord trauma. Infused fluids and many medications have effects on
CVP, and the ability to measure these effects is medically
indicated. In addition to infusion, there are numerous clinical
situations for blood of fluid withdrawal which can be facilitated
by a central venous access catheter. These situations include but
are not limited to checking blood chemistries, blood counts,
pathogen identification and treatment, and determining oxygen
saturation in central venous blood samples. In the relevant art,
securing central venous vascular access includes catheters placed
directly into blood vessels via a direct percutaneous route or via
subcutaneously tunneled catheters (e.g., Hickman and Broviac
devices). Securing central venous vascular access via direct
percutaneous central venous line placement may be achieved by
inserting a central venous catheter (CVC) into a larger vein of the
neck/subclavian or groin region, or by placing a peripherally
inserted central catheter (PICC), which is typically inserted into
one of the major veins of an upper or lower extremity. The distal
ends of either of these types of catheters are advanced into the
largest central veins, generally into the superior vena cava or
inferior vena cava. However, there are significant differences that
exist between CVCs and PICCs in terms of placement techniques and
potential complications. Typically, CVCs are generally placed in
large veins (e.g., jugular vein) in or near the patient's neck or
groin (e.g., external iliac vein) using the Seldinger technique.
While effective, CVC placement is not without risks. These risks
include inadvertent arterial puncture, intra-arterial placement,
large vessel bleeding which may prove difficult to control, air
embolism, cardiac arrhythmias and pneumothorax. As a consequence of
these significant risks, CVC placement is almost exclusively
performed by a skilled physician, effectively limiting the number
of those capable of performing CVC placement.
[0006] In the relevant art, CVCs typically employ fluid column
manometer transduction of CVP. Fluid column manometry requires
skilled personnel and the utilization of one the catheter's lumens
(as detailed below), rendering that lumen unavailable for
simultaneous use as an infusion or blood drawing port. Due to the
need for skilled operators and operator-dependent external
equipment required for pressure measurements using this technique,
from a practical standpoint CVP measurement is restricted to
specialized settings, such as the intensive care unit (ICU) or the
operating room (OR). This fact limits the practical applicability
of CVCs for measurement of CVP in the ICU/post-OR and post-hospital
settings, despite potential continued need for such information to
guide care. Moreover, due to issues regarding catheter care and
safety, patients are rarely discharged from hospital care to home
with a percutaneous CVC still in place.
[0007] In current manometer transducer CVP measurement, at least
one lumen of the catheter is filled with an isotonic saline
solution, and pressure measurements are made using a manometer
situated external to the patient. This is typically performed by
specially trained staff who must take particular care to position
an external transducer at a height approximating the level of the
patient's right atrium. Operator-dependent variations in
positioning of the external transducer height, or change in patient
position after transducer positioning, can predispose to erroneous
CVP measurements which can adversely affect care decisions. In
addition, the saline solution is in direct contact with biological
fluids in a given blood vessel which could provide a direct path
for pathogenic organisms resulting in sepsis.
[0008] Moreover, the manometer transducer measurement technique is
less than ideal for PICC applications, most notably due to the very
small diameter of PICCs in general, and the size of the lumen
dedicated as a saline column in specific. Kinks, blood clots or
other restrictions in the saline pressure column prevent accurate
measurement of CVP. Additionally, hydrostatic forces caused by the
ratio of the saline pressure column diameter vs. saline column
length can additionally introduce error to the measurement of CVP.
Reduced-size catheters capable of electronic CVP measurement use a
venting lumen to reference an atmospheric reference for pressure
measurements. A venting lumen occupies valuable space within the
catheter and is not available for infusing or withdrawing fluids.
Catheters that use fluid column transduction of CVP do not allow
for simultaneous fluid infusion or withdrawal from the CVP
measurement lumen during CVP determination.
[0009] Existing multi-lumen catheter devices present limitations
when bolus infusions are indicated due to semi-rigid septum wall
design. Existing designs are not intended to allow the septum wall
to undulate or flex under bolus pressure. As a result, movement in
the septum wall is largely a function of the elastomeric properties
of the catheter material, not the design of the septum wall, and as
such is negligible. This semi-rigidity effectively limits
instantaneous volume as a bolus travels through the catheter, with
a resultant increase in bolus delivery time. The resultant increase
in medication or nutrient delivery time can have a negative impact
on the patient, particularly the critically ill. Limitations of the
maximally achievable flow rate through a given lumen may result in
sub-optimal patient care at times of acute clinical need. In
addition, conventional luminal design may be predisposed to
intra-luminal thrombosis and catheter dysfunction.
[0010] The approaches described in this section could be pursued,
but are not necessarily approaches that have been previously
conceived or pursued. Therefore, unless otherwise indicated herein,
the approaches described in this section are not prior art to the
claims in this application and are not admitted to be prior art by
inclusion in this section.
SUMMARY
[0011] In a peripherally-inserted central catheter (PICC)
embodiment, an electronic pressure-sensing catheter is provided
which is designed to facilitate catheter placement and minimize
catheter insertion-related complications (including unintended and
undesirable placement or migration of catheter tip into right heart
structures) by providing real-time pressure measurement both during
and post-insertion. Employment of the electronic pressure-sensing
element in the embodiment eliminates need to employ conventional
fluid-column manometry technique to determine CVP, thereby freeing
a lumen of the catheter for other uses, while simultaneously
eliminating inherent shortcomings of fluid column manometry,
including introduction of infectious agents via the CVP measurement
lumen and operator-dependent error in CVP measurement. In this
embodiment, the electronic pressure sensing element is
non-operator-dependent and does not require a venting lumen to
reference atmospheric pressure, thus providing a significant
advantage over existing designs and allowing for a more compact
catheter design that minimizes risk of catheter-associated
thrombosis of resident vessels compared with comparable larger
diameter catheters. In this embodiment, more compact design extends
the lower limits of patient anatomic size for which catheter may be
employed for CVP determination compared with current comparable
designs.
[0012] In an embodiment, the pressure sensing catheter includes at
least one flexible conduit. In an embodiment, a pressure sensing
catheter is provided which is designed to minimize uncontrolled
bleeding, embolisms and infections. In addition, the pressure
sensing catheter may be installed within a blood vessel of a
patient by healthcare professionals other than physicians providing
healthcare savings. In an embodiment, the pressure sensing catheter
includes at least one flexible conduit which is dimensioned to
longitudinally travel within a blood vessel without occluding the
blood vessel. The flexible conduit includes a proximal end and a
distal end. The distal end of the flexible conduit includes one or
more apertures for dispensing therapeutic agents and/or other
fluids into the blood vessel. The apertures are disposed near the
distal end of the pressure sensing catheter such that infusion or
sample withdraw does not interfere with pressure measurements.
[0013] In multi-lumen embodiments of the pressure sensing catheter,
one or more of the apertures may be used to collect fluid samples
from within the blood vessel. In this embodiment, sufficient
elasticity is provided by use of selected polymeric materials to
allow delivery of the therapeutic agent as a bolus. In such
embodiments, the delivery of the bolus may temporarily "borrow"
volumes from adjacent lumens to allow the bolus to be infused into
the blood vessel. Once the bolus has been delivered, the lumens
return to their original shape which allows resumption of a
continuous stream of therapeutic or other fluids being infused into
the patient. Suitable polymeric construction materials for the
lumens and/or conduit include but are not limited to polypropylene,
polyethylene, polyurethane, polytetrafluoroethylene, silicone
rubber, nylon and combinations thereof.
[0014] Pressure sensing is accomplished using a pressure transducer
generally having a diameter no greater than 12 French, depending on
the age of the patient and condition of the patient's vascular
system.
[0015] The pressure transducer is coupled at about the distal end
of the flexible conduit and is used to measure vascular pressures.
In an embodiment, the pressure measurements are based on changes in
optical signal characteristics as part of the pressure transducer.
In another embodiment, pressure measurements are based on
piezoelectric properties of a nano-wire which flexes in response to
pressure changes. The pressure transducer is configured to measure
fluid pressure when disposed proximate to a predetermined location
to be monitored, for example, within a superior vena cava of the
patient. In one embodiment, the pressure transducer allows for
electrical isolation of the patient from the sensing electronics
which minimizes the possibility of electrical shock.
[0016] At the proximate end of the flexible conduit, one or more
leur connectors are coupled to the flexible conduit to allow for
infusion and/or withdrawal of fluid samples. The proximate end also
includes an connector which allows for linking the pressure
transducer to an electronic monitor which converts signals sent by
the pressure transducer into fluid pressure readings.
[0017] In an embodiment, at least a portion of the pressure
transducer is coaxially encompassed by the flexible conduit. For
example, the pressure transducer may be encompassed directly into
the polymeric construction of the flexible conduit to form an
integral pressure sensing catheter, or longitudinally disposed
within a lumen of the pressure sensing catheter.
[0018] In an embodiment, at least a portion of the pressure
transducer is constructed from a material having at least one
electromagnetic property. For example, ferromagnetic material
and/or radiographic opacity is provided in the construction of the
pressure transducer or catheter material in proximity to the distal
end of the flexible conduit. Alternately, or in conjunction with
the electromagnetic property, a portion of the pressure transducer
or catheter material may be constructed from a material having an
acoustically reflective property. The electromagnetic and/or
acoustically reflective properties allows a practitioner to
accurately determine the location of the distal end of the pressure
sensing catheter within the blood vessel to ensure proper placement
of the pressure transducer. In an embodiment, the placement of the
pressure transducer is within a superior vena cava or inferior vena
cava.
[0019] In an embodiment, the pressure sensing catheter is routed
through a peripheral vein, typically into the superior vena cava.
Once positioned within the superior vena cava, pressure sensing,
infusion and/or withdrawal of fluid samples may be performed.
[0020] In an embodiment, routing of the pressure sensing catheter
is accomplished using a guide wire which is inserted into the
flexible conduit and positioned in the proper location by the
practitioner. Once the end of the guide wire is positioned in the
proper vascular location, the flexible conduit is slidably
positioned such that the pressure transducer is positioned at or
near the end of the guide wire. The guide wire is then removed,
leaving the flexible conduit and pressure sensor in the proper
location within a given blood vessel. In an embodiment, the guide
wire is eliminated by reducing the flexibility of the flexible
conduit such that at least the outer circumference allows direct
routing within a blood vessel.
[0021] In an embodiment, a central venous catheter (CVC) may be
configured for placement via a central vein of the neck, subclavian
vein or groin vein regions which includes an electronic
pressure-sensing element and at least one flexible septum
BRIEF DESCRIPTION OF DRAWINGS
[0022] The features and advantages of the invention will become
apparent from the following detailed description when considered in
conjunction with the accompanying drawings. Where possible, the
same reference numerals and characters are used to denote like
features, elements, components or portions of the invention.
Optional components or feature are generally shown in dashed lines.
It is intended that changes and modifications can be made to the
described embodiment without departing from the true scope and
spirit of the subject invention as generally defined by the
claims.
[0023] FIG. 1 provides an isometric view of a pressure sensing
catheter in accordance with an exemplary embodiment;
[0024] FIG. 1A provides a detail plan view of a distal end of a
pressure sensing catheter in accordance with an exemplary
embodiment;
[0025] FIG. 2 provides a plan view of an implementation of a
pressure sensing catheter in accordance with an exemplary
embodiment;
[0026] FIG. 3 provides a detail plan view of an implementation of a
pressure sensing catheter in accordance with an exemplary
embodiment;
[0027] FIG. 4A provides an isometric view of a single lumen
pressure sensing catheter in accordance with an exemplary
embodiment;
[0028] FIG. 4B provides an isometric view of a dual lumen pressure
sensing catheter in accordance with an exemplary embodiment;
[0029] FIG. 4C provides an isometric view of a triple lumen
pressure sensing catheter in accordance with an exemplary
embodiment;
[0030] FIG. 4D provides a cross section view of a triple lumen
pressure sensing catheter in accordance with an exemplary
embodiment;
[0031] FIG. 5 provides a block diagram of an electronic monitor in
accordance with an exemplary embodiment.
DETAILED DESCRIPTION
[0032] FIGS. 1, 1A provide an exemplary embodiment of a pressure
sensing catheter. In an embodiment, pressure sensing catheter 100
is comprised of a flexible conduit section 105 having dual lumens
110, 115 (FIG. 1A). Each lumen 110, 115 is contiguously connected
at a proximal end to a leur connector 130, 135 (FIG. 1A; shown with
leur caps installed). Leur connectors 130, 135 allow for the
contemporaneous infusion of fluids and/or withdrawal of fluid
samples from a patient when pressure sensing catheter 100 is
disposed in situ. One skilled in the art will appreciate that other
types of connectors known in the relevant art may be used in lieu
of the leur connectors 130, 135.
[0033] A separate signal lead connector 125 is provided at the
proximal end of pressure sensing catheter 100 which facilitates
coupling of a signal lead 120 with an electronic monitor 500 (FIG.
5). Signal lead 120 longitudinally extends from signal lead
connector 125 to a pressure transducer 160 disposed at about a
distal end of pressure sensing catheter 100 and connects with
electronic monitor 500 via a sensor interface link 170. The
longitudinal placement of signal lead 120 is not critical. For
example, signal lead 120 may be integrated with flexible conduit
section 105, longitudinally disposed in one of lumens 110, 115, or
coupled to an exterior surface of flexible conduit section 105.
[0034] In this dual lumen embodiment of pressure sensing catheter
100, apertures 140, 145 provide fluidic continuity with lumens 110,
115 and leur connectors 130, 135. Apertures 140, 145 are
dimensioned to allow a uniform infusion flow rate using gravity
feed. In an embodiment, the cross-sectional area of apertures 140,
145 is approximately equal to or greater than the cross-sectional
area of lumens 110, 115. The actual dimensions of apertures 140,
145 may be varied to allow smaller or greater infusion fluid flow
rates by changing the dimensions of apertures 140, 145
accordingly.
[0035] In an embodiment, apertures 140, 145 are longitudinally
disposed proximate to pressure transducer 160 but longitudinally
positioned along flexible conduit section 105 a sufficient distance
from pressure transducer 160 to minimize pressure measurement
disturbances induced by infusion or withdrawal of fluids via
apertures 140, 145. A hemispherical tip 155 may be provided at the
distal end of pressure sensing catheter 100 to reduce the amount of
force required to move pressure transducer 160 into a predetermined
location within a blood vessel. In an embodiment, hemispherical tip
155 is constructed from polytetrafluoroethylene to reduce glide
resistance within the blood vessel.
[0036] In an embodiment, a portion of pressure transducer 160
includes a material which allows for external detection of the
distal end of pressure sensing catheter 100. For example, a
ferromagnetic material 150 may be disposed proximate to pressure
transducer 160 to provide radiographic opacity, ultrasonic
reflectivity and/or magnetic detection. Alternately, polymeric
materials used in the construction of pressure sensing catheter 100
may be embedded with metal particles to increase electromagnetic
and/or ultrasonic detection properties. The electromagnetic and/or
acoustically reflective properties of pressure sensing catheter 100
allows a practitioner to accurately determine the location of at
least the distal end of pressure sensing catheter 100 within a
given blood vessel.
[0037] Once pressure sensing catheter 100 is placed in situ, the
patient or subject's CVP is measured via pressure transducer 160.
In an embodiment, pressure transducer 160 senses reflected optical
signals. Reflected optical signals are returned to electronic
monitor 500 via signal lead 120 for processing and conversion to
CVP. Suitable optoelectric type pressure transducers are
commercially available from FISO Technologies, 500 St-Jean-Baptiste
Ave., Suite 195, Quebec, QC, G2E 5R9, CANADA and BIOPAC Systems,
Inc., 42 Aero Camino, Goleta, Calif. 93117. In another embodiment,
pressure transducer 160 utilizes a nano-wire which induces a
current flow based on piezoelectric properties. An example of a
suitable nano-wire pressure transducer is described in non-patent
printed publication, "MIT Technology Review," "A Nano Pressure
Sensor," by Prachi Patel-Predd dated Mar. 6, 2007. The
aforementioned non-patent printed publication is hereby
incorporated by reference in its entirety as if fully set forth
herein. In either embodiment, flexible conduit section 105
generally has a diameter no greater than 12 French 165, depending
on the age of the patient and condition of the patient's vascular
system. The diameter of flexible conduit section 105 is chosen to
allow positioning within a blood vessel without occlusion of blood
flow.
[0038] Referring to FIG. 2, an exemplary implementation of a
pressure sensing catheter 100 is depicted. In an embodiment, a
practitioner selects a venipuncture site, with basilic, cephalic or
median cubital veins commonly chosen 205. Alternately, venipuncture
sites such as neck/subclavian 235 or groin region 230 may be
accessed as well. The desired venipuncture site is prepared for the
procedure using standard sterile technique. Vascular access is
typically achieved using a cannula (not shown) of appropriate size.
Various options for vascular access are possible, including the use
of a needle/stylet which incorporates a peelable sheath/cannula
arrangement. One skilled in the art will appreciate that various
methods are known in the relevant art for obtaining vascular
access.
[0039] Once vascular access is achieved, pressure sensing catheter
100 is introduced into a selected vein 205 via the previously
inserted cannula, and may be advanced over a guide wire 400 (FIGS.
4A, 4B, 4C) or via direct puncture placement. Pressure sensing
catheter 100 is then carefully advanced through the selected vein
205 into a desired position, typically the superior vena cava 305
for CVP monitoring.
[0040] In an embodiment, the insertion procedure may be guided
using real-time pressure data provided by pressure transducer 160
if electronic monitor 500 is connected to signal lead connector 125
(FIG. 1). The location of the distal end of pressure sensing
catheter 100 may be verified by use of fluoroscopy, conventional
X-ray, ultrasound and/or magnetic signature. Proper placement of
pressure sensing catheter 100 in the superior vena cava 305 (FIG.
3) is critical, since intrusion of a catheter or other foreign body
into the right atrium 310 of the heart 300 can result in
arrhythmias and fatal pericardial tamponade. For example, tips of
PICC lines frequently migrate either centrally into a chamber of
the heart or migrate peripherally so that the tip of the PICC line
is no longer in an ideal position or safe location. If the PICC
line migrates centrally, the catheter may be malpositioned and
could result in perforation and life-threatening hemorrhage. If the
PICC line tip migrates peripherally, the utility of the PICC line
can be affected, and the PICC line may need to be replaced. Thus
the ability to monitor pressure using a PICC line would aid in
identification of PICC line tip migration, since pressures vary
depending on where in vascular system a pressure transducer is
positioned.
[0041] In an embodiment, pressure transducer 160 may used to detect
unintended proximity of the distal end of pressure sensing catheter
100 to the right atrium 310 or right cardiac ventricle 315.
Following verification of proper pressure sensing catheter 100
placement, CVP monitoring, infusion and/or sample withdrawal may
then proceed. For example, a first intravenous fluid source IV1 210
is connected to pressure sensing catheter 100 via leur 135 which
allows gravity feed of the fluid contained in IV1 210 to flow
through lumen 115 and into the superior vena cava 305 of patient
200. Analogously, a second intravenous fluid source IV2 215 is
connected to pressure sensing catheter 100 via leur 130 which
allows gravity feed of the fluid contained in IV2 215 to flow
through lumen 110 and infuse into the superior vena cava 305 of
patient 200 contemporaneously with fluid flow from IV1 210.
[0042] When infusing, the fluid travels from the proximal end of
pressure sensing catheter 100 through a selected lumen 110 or 115
(FIG. 1A) and exits at the distal end of pressure sensing catheter
100 into the patient's 200 blood vessel through a contiguous
aperture 140 or 145. For fluid withdrawal, the proximal end of
pressure sensing catheter 100 is connected to either a gravity or
negative-displacement source, such as syringe 220. During fluid
withdrawal, fluids enter the distal end of pressure sensing
catheter 100 via apertures 140 or 145, and travel through
respective lumen 110 or 115 into a suitable fluid collection
container.
[0043] In an embodiment, CVP monitoring is provided by pressure
transducer 160 (FIG. 1A) which is positioned within the superior
vena cava 305. In this embodiment, optical signals are generated by
electronic monitor 500 and sent through signal lead connector 125
(FIG. 1A). Signal lead 120 (FIG. 1A), which in this embodiment is
an optical fiber, transfers the signals to pressure transducer 160
which reflects optical signals back to electronic monitor 500 as a
function of vascular pressure. Electronic monitor 500 processes the
reflected optical signals and converts the processed optical
signals into usable pressure measurements which may appear on a
display 560 (FIG. 5).
[0044] In an embodiment, CVP monitoring is provided by pressure
transducer 160 (FIG. 1A) which is likewise positioned within the
superior vena cava 305. In this embodiment, electrical signals are
generated by pressure transducer 160 (FIG. 1A) and sent through
signal lead connector 125 for processing by electronic monitor 500
as a function of vascular pressure. Signal lead 120 (FIG. 1A), in
this embodiment is a wire. Electronic monitor 500 processes the
electrical signals and converts the processed electronic signals
into usable pressure measurements which may appear on a display
560. A bolus of fluid may be injected into one of the IV lines
using for example, syringe 220.
[0045] In an embodiment, electronic monitor 500 may be programmed
to detect CVP changes that are characteristic of an unintended
approach to heart 300 (FIG. 3). An acceptable CVP range may be
output by electronic monitor 500 to display 560. Deviations
detected by electronic monitor 500 outside the acceptable CVP range
may be used to trigger a tactile, auditory and/or visual
annunciator. Such annunciators may be integrated into electronic
monitor 500 and/or may be located remotely (e.g., nursing station).
Additionally, electronic monitor 500 may trigger annunciators via
wireless means. Alternately, electronic monitor 500 may communicate
with annunciators via a computer network.
[0046] Referring to FIG. 3, a detail plan view of a pressure
sensing catheter 100 positioned within a central venous system of
the patient's heart 300 is provided. In an embodiment, the distal
end of pressure sensing catheter 100 is positioned within the
superior vena cava such that pressure transducer 160 can measure
the CVP within the superior vena cava 305. Flexible conduit section
105 of pressure sensing catheter 100 is cannulated within
peripheral vein 205 as shown in FIG. 2. As discussed above,
placement of pressure sensing catheter 100 within the patient's
superior vena cava 305 must be carefully performed to avoid
disruption of normal heart function or damage to the heart
itself.
[0047] FIGS. 4A, 4B and 4C provides cross-sectional views of
various embodiments of pressure sensing catheter 100. FIG. 4A
provides an exemplary embodiment of a single lumen 110 pressure
sensing catheter 100 in which signal lead 120 is axially
encompassed paracentrally within flexible conduit section 105 of
pressure sensing catheter 100. An exemplary guide wire 400 is shown
axially disposed within lumen 110 for positioning of pressure
sensing catheter 100 within a selected blood vessel.
[0048] FIG. 4B provides an exemplary embodiment of a dual lumen 110
pressure sensing catheter 100 in which signal lead 120 is axially
encompassed within flexible conduit section 105 of pressure sensing
catheter 100 and disposed subjacent to lumens 110, 115. A septum
410 is provided which separates lumen 110 from lumen 115. Lumens
110, 115 are depicted as having approximately equal cross-sectional
areas for illustrative purposes only. One skilled in the art will
appreciate that each lumen 110, 115 may be individually dimensioned
to meet a particular requirement. In an embodiment, septum 410 may
be constructed from a resilient polymeric material to allow for
temporary expansion and contraction of a given lumen 110 or 115 due
to infusion of a bolus. A more detailed discussion of variable
lumen dimensions is provided below with the discussion accompanying
FIG. 4D. As discussed above, an exemplary guide wire 400 is shown
axially disposed within lumen 110 for positioning of pressure
sensing catheter 100 within a selected blood vessel.
[0049] FIG. 4C provides an exemplary embodiment of a triple lumen
110 pressure sensing catheter 100 in which signal lead 120 is
axially encompassed within the flexible conduit section 105 of
pressure sensing catheter 100 and disposed at about an axial
centerline of conduit section 105. In this embodiment, three septa
410, 415, 420 are provided which axially separate lumens 110, 115,
405 from one another. As discussed above, the cross-sectional area
of each lumen 110, 115, 405 may be varied to meet a particular
cannulation need. In addition, the location of each septum 410,
415, 420 may be varied as well. As depicted, each septum 410, 415,
420 divides the cross-sectional area of flexible conduit section
105 into three equal lumens 110, 115, 405 and are radially disposed
relative to an axial centerline of flexible conduit section 105 at
approximately 120 degrees apart. One or more of septa 410, 415, 420
may be constructed to allow for temporary expansion and contraction
of a given lumen 110, 115, 405 due to infusion of a bolus. A more
detailed discussion of variable lumen dimensions is provided below
with the discussion accompanying FIG. 4D. As also discussed above,
an exemplary guide wire 400 is shown axially disposed within lumen
110 for positioning of pressure sensing catheter 100 within a
selected blood vessel.
[0050] FIG. 4D provides a cross-sectional view of a triple lumen
pressure sensing catheter 100 in accordance with an embodiment. In
this embodiment, three septa 410, 415, 420 are radially connected
to an inner wall of flexible conduit section 105 such that three
separate lumens 110, 115, 405 are provided within pressure sensing
catheter 100. Septum 410 includes a straight profile, septum 415
has a fanfold shape with a zigzag profile, and a wall thickness
that is thinner than the wall thicknesses of flexible conduit
section 105 and septum 410. In an embodiment, septum 420 has an
S-shaped, wavy, undulating profile and is provided with a wall
thickness that is thinner than the wall thicknesses of flexible
conduit section 105 and septum 410. The nonlinear profiles and
thinner wall thicknesses render septa 415, 420 more flexible than
septum 410.
[0051] The flexible septum arrangement is applicable to both CVC
and PICC designs, and manufacture of the undulating septum
multi-lumen catheter begins with sizing the catheter to the
intended use. For pediatric applications, catheters outside
diameters of 3 to 6 French are common. In adult applications,
outside diameters of 4 to 12 French are common. In all
applications, typical catheter and septum wall thickness are 0.002
to 0.010 inches. Next, the desired number of lumens is determined,
as well as the location of the guidewire opening. Finally, a
suitable flexible, elastomeric, biocompatible polymeric material is
selected. For example, suitable polymeric materials for
constructing pressure sensing catheter 100 and/or septa 410, 415,
420 include but are not limited to polypropylene, polyethylene,
polyurethane, polytetrafluoroethylene, silicone rubber, synthetic
rubber, nylon and various combinations thereof. In an embodiment,
the nonlinear (undulating and/or zigzag) profiles and/or thinner
walls render septa 415, 420 more flexible than septum 410.
[0052] The added flexibility accommodates a temporary increase in
fluid volume (bolus) in multi-lumen catheters. Flexible lumen
volumes allow more rapid delivery of life-saving medications such
as epinephrine, anti-arrhythmic agents, bicarbonate, dextrose,
antibiotics, etc at times of critical need. Flexible lumens also
permit rapid bolus infusion of radiologic contrast agents, such as
required for computerized tomographic angiography to detect a
pulmonary embolism. A smaller size catheter with flexible septae
may provide the benefits of a larger one, and may be less likely to
induce clot formation in a given vein in which the PICC resides, as
the risk of PICC-associated vascular thrombosis increases as
catheter French size increases.
[0053] In an embodiment, signal lead 120 provides sufficient
stiffness to allow positioning of pressure sensing catheter within
a given blood vessel which may eliminate the need for guide wire
400 (FIGS. 4A, 4B, 4C).
[0054] In an embodiment, manufacturing of a triple lumen pressure
sensing catheter 100 is performed using an extrusion process
whereby flexible conduit section 105, septum 410, 415, 420
multi-lumen embodiments and signal lead 120 are extruded together
in a single operation. The extruded flexible conduit section 105 is
then cut to a desired length, followed by coupling of pressure
transducer 160 (FIG. 1A) and optional hemispherical tip 155 (FIG.
1A) to the distal end of flexible conduit section 105. At the
proximate end of flexible conduit section 105, leur connectors 130,
135 (FIG. 1) may then be coupled to lumens 110, 115 (FIG. 1A) and
signal lead connector 125 (FIG. 1A) coupled to signal lead 120
forming pressure sensing catheter 100. One skilled in the art will
appreciate that other manufacturing processes may be used in the
production of pressure sensing catheter 100. Electronic monitor 500
(FIG. 2) is provided by the vendor supplying pressure transducer
160.
[0055] The use of low cost construction materials allows for the
one time use of the pressure sensing catheter. A used pressure
sensing catheter may be disposed of as medical waste after use.
[0056] FIG. 5 provides a block diagram of an electronic monitor in
accordance with an exemplary embodiment. In an embodiment,
electronic monitor 500 is coupled to pressure sensing catheter 100
via sensor interface link 170. In an embodiment, electronic monitor
500 includes a communications bus 510 or other communication
mechanism for communicating information coupled with bus 510, and a
processor 505 coupled with bus 510 for processing information.
Electronic monitor 500 also includes a main memory 520, such as a
random access memory (RAM), flash memory, or other dynamic storage
device, coupled to bus 510 for storing information and instructions
to be executed by processor 505. Main memory 520 also may be used
for storing temporary variables or other intermediate information
during execution of instructions to be executed by processor
505.
[0057] In an embodiment, processor 505 executes one or more
sequences of instructions contained in main memory 520. Such
instructions may be read into main memory 520 from a
computer-readable medium, such as storage device 525. Execution of
the sequences of instructions contained in main memory 520 causes
processor 505 to convert signals received from pressure sensing
catheter 100 for outputting in a human cognizable format. In
alternative embodiments, hard-wired circuitry may be used in place
of or in combination with software instructions to convert signals
received from pressure sensing catheter 100 for outputting in a
human cognizable format. Thus, embodiments are not limited to any
specific combination of hardware circuitry and software. Electronic
monitor 500 further includes a read only memory (ROM) 515 or other
static storage device coupled to bus 510 for storing static
information and instructions for processor 505. A storage device
525, and/or removable storage media 535 such as a magnetic disk,
flash memory or optical disk may be provided and coupled to bus 510
for storing information and instructions on computer readable media
as is discussed below.
[0058] Electronic monitor 500 may be coupled via bus 510 to a
display 560, such as a cathode ray tube ("CRT"), liquid crystal
display (LCD) or other display device for displaying information in
human cognizable format to a user of electronic monitor 500. A user
interface 555 is provided for communicating information and command
selections to processor 505 of electronic monitor 500. User
interface 555 is coupled to bus 510 and may include for example, a
keyboard, a mouse or other pointing device, and/or a touch-screen
sensor coupled to display 560.
[0059] A communication interface 550 may be coupled to bus 510 for
communicating information and command selections to processor 505.
Communications interface 550 may be a conventional serial interface
such as an RS-232, RS-422, or a USB interface. Communications
interface 550 may also be configured as a network interface for
exchanging data with one or more external networked devices over a
private or public packet switched network. In an embodiment,
communication interface 550 is used to wirelessly connect pressure
sensing catheter 100 to sensor interface 540. In some such
embodiments, sensor interface link 170 is a wireless network
connection.
[0060] Pressure sensing catheter 100 is coupled via sensor
interface link 170 to a sensor interface 540. Sensor interface 540
provides any necessary digital signal processing, analog to digital
conversion, digital to analog conversion, noise discrimination
and/or optoelectric isolation for use of Pressure sensing catheter
100 with electronic monitor 500. Sensor interface 540 is coupled to
bus 510 and is controlled by processor 505 executing the sequences
of instructions contained in main memory 520.
[0061] In an embodiment, an alarm circuit 545 is provided which
monitors dynamic fluid signals received over bus 510 from sensor
interface 540. Alarm circuit 545 is programmed to provide a human
cognizable alert if dynamic fluid signals detected by pressure
sensing catheter 100 fall outside an allowable range. For example,
homeostasis central venous pressure typically falls within a range
of about 2-8 mmHg, while pressures associated with the right
ventricle of the heart 300 (FIG. 3) typically range between 5-25
mmHg. Thus, to prevent malpositioning pressure sensing catheter 100
too close to the heart 300, an alarm set to annunciate when dynamic
fluid signals indicate, for example, a pressure at 20 mmHg. One
skilled in the art will appreciate that other alarm setpoints can
be established as well.
[0062] Additional processing may be provided to distinguish between
central venous pressure waveforms from right ventricle waveforms in
order to cause alarm circuit 545 to annunciate an alarm. Alarms
generated by alarm circuit 545 may be output audibly, visually to
display 560 and/or tactilely to an optional vibratory element 570
provided at the proximal end of pressure sensing catheter 100. One
skilled in the art will appreciate that the functionality of alarm
circuit 545 may be accomplished by firmware, software or a
combination of firmware and software executed by processor 505.
[0063] The term "computer-readable medium" as used herein refers to
any medium that participates in providing instructions to processor
505 for execution. Such a medium may take many forms, including but
not limited to, non-volatile media, volatile media, and
transmission media. Non-volatile media includes, for example,
optical or magnetic disks, such as storage device 510. Volatile
media includes dynamic memory, such as main memory 506.
Transmission media includes coaxial cables, copper wire and fiber
optics, including the wires that comprise bus 510. Transmission
media can also take the form of acoustic or light waves, such as
those generated during radio wave and infrared data
communications.
[0064] Common forms of tangible computer-readable media include,
for example, a floppy disk, a flexible disk, hard disk, magnetic
tape, or any other magnetic medium, a CD-ROM, any other optical
medium, punch cards, paper tape, any other physical medium with
patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any
other memory chip or cartridge, a carrier wave as described
hereinafter, or any other medium from which a computer can
read.
[0065] Various forms of computer readable media may be involved in
carrying one or more sequences of one or more instructions to
processor 505 for execution. For example, the instructions may
initially be carried on a magnetic disk of a remote computer. The
remote computer can load the instructions into its dynamic memory
and send the instructions over a telephone line using a modem. A
modem local to electronic monitor 500 can receive the data on the
telephone line and use an infrared transmitter to convert the data
to an infrared signal. An infrared detector coupled to bus 510 can
receive the data carried in the infrared signal and place the data
on bus 510. Bus 510 carries the data to main memory 520, from which
processor 505 retrieves and executes the instructions. The
instructions received by main memory 520 may optionally be stored
on storage device 525 either before or after execution by processor
505.
[0066] The various embodiments described herein are intended to be
merely illustrative of the principles underlying the inventive
concept. It is therefore contemplated that various modifications of
the disclosed embodiments will, without departing from the
inventive spirit and scope, be apparent to persons of ordinary
skill in the art. They are not intended to limit the inventive
embodiments to any precise form described. In particular, it is
contemplated that the various embodiments of the pressure sensing
catheter may be used for contemporaneous infusion, fluid sampling,
and pressure measurements of spinal, cranial, lymphatic, endocrine
systems or other biological fluid systems in which contemporaneous
pressure monitoring and infusion/sample are required. No specific
limitation is intended to a particular construction material or
manufacturing processes are intended or implied. Other variations
and inventive embodiments are possible in light of above teachings,
and it is not intended that this Detailed Description limit the
inventive scope, but rather by the Claims following herein.
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