U.S. patent application number 12/256269 was filed with the patent office on 2009-04-30 for nebulizing catheter system and methods of use and manufacture.
This patent application is currently assigned to Trudell Medical Limited. Invention is credited to George Baran.
Application Number | 20090107503 12/256269 |
Document ID | / |
Family ID | 22995221 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107503 |
Kind Code |
A1 |
Baran; George |
April 30, 2009 |
NEBULIZING CATHETER SYSTEM AND METHODS OF USE AND MANUFACTURE
Abstract
A method and apparatus for delivering a medicine to a patient
via the patient's respiratory system with control and efficiency. A
nebulization catheter is positioned in the patient's respiratory
system so that a distal end of the nebulization catheter is in the
respiratory system and a proximal end is outside the body. In a
first aspect, the nebulization catheter may be used in conjunction
with an endotracheal tube and preferably is removable from the
endotracheal tube. The nebulization catheter conveys medicine in
liquid form to the distal end at which location the medicine is
nebulized by a pressurized gas or other nebulizing mechanism. The
nebulized medicine is conveyed to the patient's lungs by the
patient's respiration which may be assisted by a ventilator. By
producing the aerosol of the liquid medicine at a location inside
the patient's respiratory system, the nebulizing catheter provides
for increased efficiency and control of the dosage of medicine
being delivered. In further aspects of the nebulizing catheter
apparatus and method, alternative tip constructions, flow pulsation
patterns, centering devices, sensing devices, and aspiration
features afford greater efficiency and control of aerosolized
medicine dosage delivery.
Inventors: |
Baran; George; (London,
CA) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Trudell Medical Limited
|
Family ID: |
22995221 |
Appl. No.: |
12/256269 |
Filed: |
October 22, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10607246 |
Jun 25, 2003 |
7469700 |
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12256269 |
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09265603 |
Mar 10, 1999 |
6729334 |
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10607246 |
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08787813 |
Jan 23, 1997 |
5964223 |
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09265603 |
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08261866 |
Jun 17, 1994 |
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08787813 |
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Current U.S.
Class: |
128/204.25 ;
128/204.26; 128/207.14 |
Current CPC
Class: |
A61M 16/0463 20130101;
A61M 11/001 20140204; A61M 16/0486 20140204; A61M 15/00 20130101;
A61M 25/003 20130101; A61M 2025/0073 20130101; A61M 2205/0266
20130101; A61M 2025/0035 20130101; A61M 16/0404 20140204; A61M
16/042 20140204; A61M 25/0068 20130101; A61M 2025/0036 20130101;
A61M 2025/0037 20130101; A61M 15/025 20140204; A61M 25/0009
20130101; A61M 16/0484 20140204; A61M 2025/0039 20130101; A61M
11/06 20130101; A61M 2025/004 20130101; A61M 25/0071 20130101; A61M
11/005 20130101 |
Class at
Publication: |
128/204.25 ;
128/207.14; 128/204.26 |
International
Class: |
A61M 16/10 20060101
A61M016/10 |
Claims
1-88. (canceled)
89. A method for delivering a medicine to a patient, comprising:
positioning a nebulization catheter in the patient; and operating
the nebulization catheter to produce an aerosol of the medicine at
a distal end of the nebulization catheter in synchronism with the
patient's inhalation while the nebulization catheter is positioned
in the patient.
90. The method of claim 89, wherein operating the nebulization
catheter comprises applying an electric signal to the distal end of
the nebulization catheter to produce the aerosol from the distal
end.
91. The method of claim 89, wherein operating the nebulization
catheter further comprises: delivering a liquid medicine to a first
orifice located at the distal end of the nebulization catheter; and
delivering a pressurized gas to a second orifice located at the
distal end of the nebulization catheter in proximity to the first
orifice.
92. The method of claim 91, further comprising: imparting pulsation
to the liquid medicine being delivered.
93. A method for delivering a medicine to a patient, comprising:
sensing a physiological condition of the patient; and operating a
nebulization catheter to produce an aerosol of the medicine at a
distal end of the nebulization catheter as a function of the sensed
physiological condition.
94. The method of claim 93, wherein sensing the physiological
condition of the patient comprises sensing inhalation of the
patient.
95. The method of claim 93, wherein sensing the physiological
condition comprises detecting one of a pressure, flow or
physiological parameter in the patient with a sensor.
96. The method of claim 95, wherein the sensor comprises a
plurality of sensors.
97. The method of claim 95, wherein the sensor is positioned on the
nebulization catheter.
98. A nebulization catheter system comprising: a nebulization
catheter having a catheter shaft comprising: a liquid lumen
centrally located in said catheter shaft and adapted for conveying
a medicine in liquid form; a gas lumen peripherally located
adjacent said liquid lumen and adapted for conveying a gas; a
distal liquid orifice communicating with said liquid lumen; and a
distal gas orifice communicating with said gas lumen, said distal
gas orifice being aligned with respect to said distal liquid
orifice so as to nebulize a liquid medicine discharged from the
liquid orifice; and a sensor configured to detect information
regarding a patient's respiration for use in controlling a flow of
the medicine or gas to the nebulization catheter.
99. The system of claim 98, wherein the sensor is positioned on the
nebulization catheter.
100. The system of claim 98, wherein the sensor is configured to
detect a pressure, a flow or a physiological parameter of a
patient.
101. The system of claim 98, wherein the physiological parameter
comprises a muscle contraction.
102. The system of claim 98, further comprising a controller in
communication with the sensor, the controller configured to control
a fluid flow of medicine to the nebulization catheter or a gas
pressurization of gas supplied to the nebulization catheter in
response to detected information regarding the patient's
respiration.
103. The system of claim 98, wherein the controller is configured
to operate in a first mode to provide medicine to the nebulizing
catheter except when an exhalation is detected at the sensor.
104. The system of claim 102, wherein the controller is selectably
adjustable to operate in the first mode or a second mode, where the
controller is operable to provide a controlled volume of medicine
to the nebulizing catheter during each of a plurality of
predetermined nebulization pulses in the second mode.
105. The system of claim 98, wherein the sensor comprises a
plurality of sensors.
106. The system of claim 98, wherein the sensor comprises one of a
piezoelectric, optical or Hall effect sensor.
107. The system of claim 98 wherein the sensor is configured to
control the flow of medicine or gas in synchronism with the
patient's inhalation.
Description
REFERENCE TO RELATED APPLICATION
[0001] The present application incorporates by reference the
copending application entitled "IMPROVED CATHETER SYSTEM FOR
DELIVERY OF AEROSOLIZED MEDICINE FOR USE WITH PRESSURIZED
PROPELLANT CANISTER" filed by the same inventor of the present
application and on even date herewith.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to aerosol delivery of
medication to the lungs and more particularly, the present
invention relates to delivery systems for application of nebulized
medication to the lungs with improved delivery rates, efficiencies,
and control.
[0003] Many types of medication can be administered to a patient
via the respiratory tract. Medication delivered through the
respiratory tract may be carried with a patient's inhalation breath
as airborne particles (e.g. an aerosol or nebula) into the lungs
where the medication can cross through the thin membrane of the
alveoli and enter the patient's bloodstream. Delivery of medication
via the respiratory tract may be preferred in many circumstances
because medication delivered this way enters the bloodstream very
rapidly. Delivery of medication to the lungs may also be preferred
when the medication is used in a treatment of a disease or
condition affecting the lungs in order to apply or target the
medication as close as physically possible to the diseased
area.
[0004] Although delivery of medication via the respiratory tract
has been used for many years, there are difficulties associated
with prior systems that have limited their use and application. For
example, conventional methods have provided for only limited
medication delivery rates, efficiency, and control. Conventional
methods for aerosol delivery result in a substantial portion of the
medicine failing to be delivered to the lungs, and thereby possibly
being wasted, or possibly being delivered to other parts of the
body, e.g. the trachea.
[0005] Aerosols in general are relatively short-lived and can
settle out into larger particles or droplets relatively quickly.
Aerosols can also impact each other or other objects, settle out as
sediment, diffuse, or coalesce. Aerosol particles can also be
subject to hydroscopic growth as they travel. Delivery of medicine
as airborne particles requires conversion of the medicine, which
may be in liquid form, to an aerosol followed relatively quickly by
application of the aerosol to the respiratory tract. One such
device that has been utilized for this purpose is an inhaler.
Inhalers may atomize a liquid to form an aerosol which a person
inhales via the mouth or nose. Inhalers typically provide only
limited delivery of medication to the lungs since most of the
medication is deposited on the linings of the respiratory tract. It
is estimated that as little as 10-15% of an aerosol inhaled in this
way reaches the alveoli.
[0006] Aerosol delivery of a medication to a patient's respiratory
tract also may be performed while the patient is intubated, i.e.
when an endotracheal tube is positioned in the patient's trachea to
assist in breathing. When an endotracheal tube is positioned in a
patient, a proximal end of the endotracheal tube may be connected
to a mechanical ventilator and the distal end is located in the
trachea. An aerosol may be added to the airflow in the ventilator
circuit of the endotracheal tube and carried by the patient's
inhalation to the lungs. A significant amount of the aerosolized
medication may be deposited inside the endotracheal tube and the
delivery rate of the medicine to the lungs also remains relatively
low and unpredictable.
[0007] The low and unpredictable delivery rates of prior aerosol
delivery systems have limited the types of medications that are
delivered via the respiratory tract. For new medications that are
relatively expensive, the amount of wasted medicine may be a
significant cost factor in the price of the therapy. Therefore, it
would be advantageous to increase the delivery rate or efficiency
of a medicine delivered to the lungs.
[0008] Another consideration is that some aerosols delivered to the
lungs may have adverse side effects, e.g. radioactive tracers used
for lung scans. Therefore, it would be advantageous to minimize the
overall amount of medication delivered while maintaining the
efficacy of the medication by providing the same or a greater
amount of the medication to the desired site in the respiratory
tract.
[0009] Further, some medications may be more effective when
delivered in certain particle sizes. Accordingly, an improved
aerosol delivery system may provide for improved rates and
efficiencies of delivery also taking into account the aerosol
particle size.
[0010] It may also be important to administer certain medications
in specific, controlled dosages. The prior methods of aerosol
delivery not only were inefficient, but also did not provide a
reliable means to control precisely the dosage being delivered.
[0011] It may also be advantageous to be able to target medication
to a specific bronchus, or specific groups of bronchia, as desired,
while avoiding delivery of medication to other portions of the
lungs.
[0012] Taking into account these and other considerations, aerosol
delivery via the respiratory tract could become an even more widely
used and effective means of medication delivery if the delivery
rate and efficiency of the delivery could be improved.
SUMMARY OF THE INVENTION
[0013] According to an aspect of the present invention, there is
provided a method and apparatus for delivering a drug with control
and efficiency to a patient via the patient's respiratory system. A
nebulization catheter is positioned in the patient's respiratory
system so that a distal end of the nebulization catheter is in the
respiratory system and a proximal end is outside the body.
According to a first aspect, the nebulization catheter may be used
in conjunction with an endotracheal tube and preferably is
removable from the endotracheal tube. The nebulization catheter
conveys medicine in liquid form to the distal end at which location
the medicine is nebulized by a pressurized gas or other nebulizing
agent. The nebulized medicine is conveyed to the patient's lungs by
the patient's respiration which may be assisted by a ventilator.
The nebulizing catheter incorporates alternative constructions
taking into account anatomical considerations and the properties of
the medicine being nebulized to provide delivery of medicine with
control and efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows an exploded view of a first embodiment of the
present invention.
[0015] FIG. 2 shows an assembled view of the embodiment of FIG.
1.
[0016] FIG. 2A is a sectional view of the nebulization catheter of
FIGS. 1 and 2.
[0017] FIG. 3 is a plan view of an alternative embodiment of the
endotracheal tube shown in FIGS. 1 and 2.
[0018] FIG. 4 is a cross sectional view taken along the line a-a'
of the alternative embodiment of the endotracheal tube shown in
FIG. 3 without the nebulizing catheter in place.
[0019] FIG. 5 is a cross sectional view taken along the line b-b'
of the alternative embodiment of the endotracheal tube shown in
FIG. 3 with the nebulizing catheter in place.
[0020] FIG. 6 is a plan view of an embodiment of the nebulizing
catheter of FIGS. 1 and 2 shown in place in the trachea of a
patient who is not intubated.
[0021] FIG. 7 is a view similar to that of FIG. 6 showing an
alternative embodiment of the nebulization catheter.
[0022] FIG. 8 is a cross section taken along lines a-a' of the
nebulization catheter of FIG. 7.
[0023] FIG. 9 is a view similar to that of FIG. 7 showing an
alternative embodiment of the nebulizing catheter shown in FIG.
7.
[0024] FIG. 10 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0025] FIG. 11 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0026] FIG. 12 is a perspective view of an alternative embodiment
of FIG. 11 with the liquid lumen shown in a closed condition.
[0027] FIG. 13 is a perspective view of the embodiment of FIG. 12
with the liquid lumen shown in an open condition.
[0028] FIG. 14 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0029] FIG. 15 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0030] FIG. 16 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0031] FIG. 17 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
10.
[0032] FIG. 18 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0033] FIG. 19 is a sectional view of the distal end of the
embodiment of the nebulization catheter shown in FIG. 18.
[0034] FIG. 20 is a sectional view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0035] FIG. 21 is a sectional view similar to that of FIG. 20
showing an alternative embodiment of the nebulization catheter
shown in FIG. 20.
[0036] FIG. 22 is a perspective view partially in section of a
distal end of an alternative embodiment of the nebulization
catheter shown in FIG. 1.
[0037] FIG. 23 is a view similar to that of FIG. 22, showing an
alternative embodiment of the nebulization catheter shown in FIG.
22.
[0038] FIG. 24 is a perspective view partially in section of a
distal end of an alternative embodiment of the nebulization
catheter shown in FIG. 1.
[0039] FIG. 25 is sectional view of a distal end of an alternative
embodiment of the nebulization catheter shown in FIG. 25.
[0040] FIG. 26 is sectional view similar to that of FIG. 25 showing
the embodiment of FIG. 25 during an exhalation stage of the
patient.
[0041] FIG. 27 is a perspective view of alternative embodiments of
the nebulization catheter and endotracheal tube shown in FIG.
1.
[0042] FIG. 28 is a perspective view of alternative embodiments of
the nebulization catheter and endotracheal tube shown in FIG.
27.
[0043] FIG. 29 is a perspective view of an alternative embodiment
of the nebulization catheter shown in FIGS. 27 and 28.
[0044] FIG. 30 is a perspective view of the embodiment of the
nebulization catheter shown in FIG. 29 shown with an endotracheal
tube in a patient's trachea.
[0045] FIG. 31 is sectional view of a distal end and a diagrammatic
view of a proximal end of an alternative embodiment of the
nebulization catheter shown in FIG. 1.
[0046] FIG. 32 is a cross section view of the embodiment of the
nebulization catheter shown in FIG. 31 taken along the line
a-a'.
[0047] FIG. 33 is sectional view of a distal end of an alternative
embodiment of the nebulization catheter shown in FIG. 1.
[0048] FIG. 34 is sectional perspective view of a distal end of an
alternative embodiment of the nebulization catheter and
endotracheal tube shown in FIG. 2.
[0049] FIG. 35 is sectional view of a distal end of an alternative
embodiment of the nebulization catheter shown in FIG. 1.
[0050] FIG. 37 is a cross section view of the embodiment of the
nebulization catheter shown in FIG. 36 taken along the line
a-a'.
[0051] FIG. 38 is a perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIGS.
36 and 37.
[0052] FIG. 39 is a perspective view of alternative embodiments of
the nebulization catheter and endotracheal tube shown in FIGS. 37
and 38.
[0053] FIG. 40 is sectional perspective view of a distal end of an
alternative embodiment of the nebulization catheter shown in FIG.
1.
[0054] FIG. 41 is a perspective view of alternative embodiments of
the nebulization catheter and endotracheal tube of FIG. 1 shown in
a patient's trachea.
[0055] FIG. 42 is a side view of an another embodiment of the
nebulization catheter of FIG. 1 showing an alternative centering
device.
[0056] FIG. 43 is a side view of an another embodiment of the
nebulization catheter of FIG. 1 showing another alternative
centering device.
[0057] FIG. 44 is a side view of an another embodiment of the
nebulization catheter of FIG. 1 showing yet another alternative
centering device.
[0058] FIG. 45 is a side view of the embodiment of FIG. 44 shown in
another stage of operation.
[0059] FIG. 46 is a side view of a distal end of a nebulization
catheter positioned in a patient's trachea illustrating an
undesirable condition.
[0060] FIG. 47 is a perspective view similar to that of FIG. 40 of
alternative embodiments of the nebulization catheter and
endotracheal addressing the condition shown in FIG. 46.
[0061] FIG. 48 shows an alternative embodiment of the nebulizing
catheter and endotracheal tube of FIG. 47 positioned in a patient's
trachea.
[0062] FIG. 49 shows an alternative embodiment of the nebulizing
catheter of FIG. 6.
[0063] FIG. 50 is a diagram illustrating an embodiment of a drug
reservoir and pressurization assembly that can be utilized in
connection with the embodiment of the nebulization catheter of FIG.
1.
[0064] FIG. 51 is a diagram similar to that of FIG. 50 illustrating
an alternative embodiment of the drug reservoir and pressurization
assembly.
[0065] FIG. 52 is a sectional view along line c-c' of FIG. 51.
[0066] FIG. 53 is a side view of an alternative embodiment of FIG.
1 including an optional humidification and heating arrangement.
[0067] FIG. 54 is a side view of a flow control system used in
connection with the embodiment of FIG. 1 used for pressuring the
liquid flow lumen.
[0068] FIG. 55 is a view similar to that of FIG. 54 showing the
flow control system of FIG. 54 in another stage of operation.
[0069] FIG. 56 is a perspective view of an alternative embodiment
of the present invention illustrating an alternative method of
use.
[0070] FIG. 57 is a perspective view illustrating an entire
nebulization catheter system including sensors.
[0071] FIG. 58 shows a sectional view of an embodiment of a
nebulizing catheter including a sensor.
[0072] FIG. 59 shows an alternative embodiment of the nebulizing
catheter shown in FIG. 58.
[0073] FIG. 60 is a sectional view of a distal end of an
alternative embodiment of the nebulizing catheter of FIG. 1.
[0074] FIG. 61 is a sectional view of an embodiment of the present
invention that incorporates a baffle to generate a secondary
aerosol.
[0075] FIG. 62 is a sectional view of another embodiment of the
present invention that incorporates a baffle to generate a
secondary aerosol.
[0076] FIG. 63 is a sectional view of yet another embodiment of the
present invention that incorporates a baffle to generate a
secondary aerosol.
[0077] FIG. 64 is a sectional view of still another embodiment of
the present invention that incorporates a baffle to generate a
secondary aerosol.
[0078] FIG. 65 is a diagram illustrating an embodiment of the
present invention that incorporates a pressurized drug/propellant
mixture canister.
[0079] FIG. 66 is a side view of an embodiment of a nebulizing
catheter incorporated into of a suction catheter.
[0080] FIG. 67 is a detailed sectional view of the tip portion of
the suction catheter--nebulizing catheter embodiment of FIG.
66.
[0081] FIG. 68 is a perspective view of the embodiment of FIG. 66
positioned in an endotracheal tube in a patient's respiratory
system.
[0082] FIG. 69 is cross sectional view of the embodiment of FIG. 66
taken along lines a-a'.
[0083] FIG. 70 is a perspective view similar to FIG. 68 showing the
suction catheter advanced during an further stage of operation.
[0084] FIG. 71 is a side view of a proximal end of an endotracheal
tube illustrating an arrangement of receiving a suction catheter
and a nebulization catheter into the endotracheal tube.
[0085] FIG. 72 is an alternative embodiment of the arrangement
shown in FIG. 71.
[0086] FIG. 73 is another alternative embodiment of the arrangement
shown in FIG. 71.
[0087] FIG. 74 is another embodiment of a suction catheter
incorporating aerosol delivery by nebulization.
[0088] FIG. 75 is still another embodiment of a suction catheter
incorporating aerosol delivery by nebulization.
[0089] FIG. 76 is a sectional view of a distal end of an embodiment
of a nebulizing catheter also incorporating a vibrating tip.
[0090] FIG. 77 is a sectional view of another embodiment of the
nebulizing catheter incorporating micropulsation of the liquid
supply.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0091] The present invention provides for the controlled and
efficient delivery of an aerosolized medication to the lungs of a
patient by nebulization of a medication at a distal end of a
catheter positioned in the respiratory tract. Throughout this
specification and these claims, the nebulization catheter is
described as used for the delivery of medicine or medication. It is
intended that the terms "medication", "medicine", and "drug" should
be understood to include other agents that can be delivered to the
lungs for diagnostic or therapeutic purposes, such as tracers, or
for humidification.
I. Nebulizing Catheter--Basic Configuration
[0092] Referring to FIGS. 1 and 2, there is depicted a first
embodiment of the present invention. FIGS. 1 and 2 show an
endotracheal tube 10 which may be a conventional endotracheal tube.
The endotracheal tube 10 may have an inflatable cuff 12 located
close to its distal end to facilitate positioning the tube 10 in
the patient's trachea, or alternatively the endotracheal tube 10
may be of a type without an inflatable cuff. The inflatable cuff 12
is connected via a separate inflation lumen in the endotracheal
tube 10 to a proximal fitting 13 for connection to a source of
inflating gas (not shown). The endotracheal tube 10 has a proximal
end connected to a manifold fitting 14. The fitting 14 has a port
15 suitably adapted for connection to a ventilator circuit (not
shown). The fitting 14 also includes another port 16 that permits
the introduction of a separate catheter into the endotracheal tube
from the proximal end. The fitting 14 may be similar in
construction to the elbow fitting described in U.S. Pat. No.
5,078,131 (Foley), the entire disclosure of which is incorporated
herein by reference. In FIG. 1, a nebulizing catheter 20 is located
in a position ready to be inserted into a ventilation lumen 22 of
the endotracheal tube 10 via the proximal fitting 14. In FIG. 2,
the nebulizing catheter 20 is positioned fully in the endotracheal
tube 10 with a proximal end extending out of the port 16 of the
proximal fitting 14.
[0093] At a proximal end of the nebulizing catheter 20 is a
manifold 24. The manifold 24 includes at least a gas port 28 and a
liquid (medicine) port 32. These ports 28 and 32 may include
conventional attaching means, such as luer lock type fittings. In
addition, these ports 28 and 32 may also include closure caps 31
that may be used to close the ports when not in use and may be
popped open when connection to a gas source or a liquid source is
desired. Optionally, the manifold 24 may also include a filter
located in-line with either the gas port 28 or the liquid port 32
or both ports to prevent lumen blockages by particulate matter. The
nebulization catheter 20 includes at least two separate lumens (as
shown in FIG. 2A). A first lumen 33 is used for conveyance of a
liquid medicine and communicates with the port 32 on the manifold
24. The other lumen 34 is used for conveyance of a pressurized gas
and communicates with the port 28 on the manifold 24. The liquid
lumen 33 communicates with a distal liquid orifice 35 and the gas
lumen 34 communicates with a distal gas orifice 36 near a distal
end 37 of the nebulization catheter 20. The distal opening 36 of
the pressurized gas lumen 34 directs pressurized gas across the
distal liquid lumen opening 35 thereby nebulizing the liquid
medication so that it can be delivered to the patient's lungs. The
distal liquid orifice 35 may be open or may be provided with a
porous material plug or a sponge-like or felt-like material plug
which may extend slightly from the distal orifice and that allows
liquid to flow from the orifice yet reduces the likelihood of
liquid drooling from the tip.
[0094] The length of the nebulization catheter 20 should be
sufficient so that the distal end 37 can be located in the desired
location in the respiratory system while the proximal end (i.e.,
including the manifold 24) is accessible to the physician or other
medical personnel for connection to suitable gas and liquid
supplies external of the patient's body. Accordingly, the length of
the nebulization catheter is dependent upon the size of the patient
in which it is being used. A shorter nebulization catheter may be
preferred in smaller patients, such as infants or children, and a
longer nebulization catheter may be needed for adults. For example,
a nebulization catheter suitable for adults may have a length of
approximately 45 cm. In one embodiment, approximately 30 cm of the
nebulizing catheter 20 is in the endotracheal tube 10. The
nebulization catheter may be introduced into the respiratory system
through a patient's mouth or via a tracheostomy tube or through the
nasal passages. The nebulization catheter may also be used to
deliver an aerosol to a patient's nasal passages in which case the
length may be correspondingly shorter.
[0095] As explained in more detail below, the generation of an
aerosol plume with the desired geometry, particle size, velocity,
etc., requires that the distal gas and liquid orifices have small
dimensions. Also as explained below, the distal gas orifice 36 and
the distal liquid orifice 35 should be in close proximity to each
other in order to produce an aerosol with the desired
characteristics and efficiency. Further, in order to provide the
desired medicine delivery rates and to operate with reasonably
available pressure sources, the liquid and gas lumens in the
nebulizing catheter should be as large as possible, consistent with
anatomical requirements. Accordingly, the nebulization catheter 20
has a multiple stage construction with a larger shaft size and
larger lumens in a main shaft section and a smaller shaft size and
smaller lumens in a distal shaft section.
[0096] As shown in FIG. 2A, the nebulizing catheter 20 is composed
of a shaft 38 having a main section 39 and a distal section 40. In
the main shaft section 39 of the nebulization catheter, the liquid
and gas lumens 33 and 34 have a larger size than in the distal
shaft section 40. For example, in the main shaft section 39, the
liquid and gas lumens each may have an I.D. of approximately 0.010
to 0.030 inches. At a most proximal end where the main shaft
section 39 connects to the manifold 24, the lumens may be even
larger. In the distal shaft section 40, the liquid and gas lumens
taper to a much smaller I.D. with the liquid lumen approximately
0.002 to 0.008 inches or even smaller and the gas lumen 0.002 to
0.020 inches. In a preferred embodiment, the liquid and gas
orifices 35 and 36 are less than 0.125 inches apart, and more
preferably less than 0.030 inches apart, and in a most preferred
embodiment less than 0.001 inches apart. In a nebulizing catheter
having an overall length of 45 cm, the main shaft section 39 may be
approximately 25 cm and the distal shaft section 40 may be
approximately 20 cm. Also, although the liquid and gas lumens are
shown to be side by side in FIG. 2A, they may also be constructed
to have an coaxial or other arrangement. Further, although the main
shaft section 39 is shown to be of a uniform diameter and profile,
alternatively it may also have a tapered diameter and profile such
that the entire shaft 38 is tapered along its length.
[0097] In a first preferred embodiment of the invention, as shown
in FIGS. 1 and 2, the nebulizing catheter 20 is removable, and
replaceable with respect to the endotracheal tube 10. This provides
several significant advantages. First, the nebulizing catheter 20
may be specifically adapted and chosen to have the desired
operating characteristics suitable for delivery of the particular
medication being administered to the patient. In addition, the fact
that the nebulizing tube 20 is removable and replaceable provides
versatility and flexibility regarding the therapy and dosage regime
that can be chosen by the physician. For example, a decision by the
physician whether to deliver a medication to the respiratory tract,
and the selection of the type and dosage of the medication to be
delivered, need not be made by the physician until after the
endotracheal tube is already in place in the patient. When the
physician determines the proper type of medication to the delivered
to the patient via the respiratory tract, the appropriate
nebulization catheter can be selected and inserted into the
endotracheal tube. Further, the nebulizing catheter 20 can be
removed after it is used and therefore it is not necessary for the
nebulization catheter to be left in the patient and occupy space in
the patient's respiratory tract or in the endotracheal tube 10 when
it is no longer needed. In addition, the decision regarding the
proper type of medication can be revisited again at any time after
the endotracheal tube is in place. If a different type of
nebulizing catheter is required, such as for sterility purposes,
the endotracheal tube need not be replaced as well.
[0098] Another advantage of providing the nebulization catheter as
a separate, removable device is that it can be accommodated in a
variety of other instruments and/or devices. For example, the
nebulization catheter of FIGS. 1-5 is shown used in an endotracheal
tube; however, the nebulization catheter could also be positioned
inside of a bronchoscope, such as in a working channel of a
bronchoscope. The nebulizing catheter could be positioned in any
instrument that is positioned in the respiratory tract and that can
accommodate the nebulizing catheter size.
[0099] The nebulizing catheter may be provided with radiopaque
markings 41 to facilitate positioning and placement. The radiopaque
markings 41 may be provided by radiopaque bands of metal or heat
shrunk bands of doped radiopaque plastic that are attached to the
nebulizing catheter, or alternatively the markings may be provided
by doping the plastic material of the nebulizing catheter with a
radiopaque material. Alternatively, a radiopaque dye may be added
to the liquid being delivered by the nebulization catheter to
assist observation. The markings 41 may be graduated to facilitate
recognition, or alternatively may extend over a portion or all of
the nebulizing catheter. In still a further embodiment, the
markings may be formed of a ultrasonic reflectors, e.g. textured
material, that are visible by means of ultrasonic imaging. The
nebulization catheter may also include a stripe 43 extending along
a side of the shaft (as shown in FIGS. 5 and 6). The stripe 43 may
be radiopaque or ultrasonically visible and may be used to
determine the rotational orientation of the shaft. The stripe may
be formed by a coextrusion process or by embedding a wire in the
wall of the nebulization catheter.
[0100] One method that may be employed to facilitate positioning of
the nebulization catheter is to monitor the pressure at the distal
end of the endotracheal tube as the nebulization catheter is being
advanced. Monitoring the pressure at the end of the endotracheal
tube may be accomplished through one of the endotracheal tube
lumens. The gas source connected to the proximal end of the
nebulization catheter may be operated so as to expel a gas from the
distal end of the nebulization catheter as it is being advanced.
The gas being expelled from the distal end of the nebulization
catheter affects the pressure being detected through the
endotracheal tube. When the distal end of the nebulization catheter
passes the distal end of the endotracheal tube, the pressure being
measured through the endotracheal tube abruptly changes thereby
providing a clear indication of the location of the distal end of
the nebulization catheter relative to the endotracheal tube.
[0101] The nebulizing catheter may also include a safety stop 44
located along a proximal portion that engages a portion of the
endotracheal tube proximal portion or a fitting thereon, as shown
in FIG. 2. The safety stop 44 ensures that the distal end of the
nebulizing catheter 20 is correctly positioned with respect to the
distal end 46 of the endotracheal tube 10 and prevents the distal
end 37 of the nebulizing catheter from extending too far into the
trachea. In addition to the safety stop 44, the proximal portion of
the nebulizing catheter 20 may also have graduated markings 48 that
would be visible to the physician handling the proximal end of the
nebulizing catheter to enable a determination of the position of
the distal end 37 of the nebulizing catheter 20 relative to a
distal end 46 of the endotracheal tube 10.
[0102] The nebulizing catheter 20 may also include a critical
orifice 49 located at a proximal portion of the nebulizing
catheter. The critical orifice 49 may be formed by a small critical
opening located in line with the gas pressurization lumen 34 of the
nebulizing catheter shaft close to the manifold 24. The critical
orifice 49 is sized so that if the nebulization catheter is
supplied with a flow in excess of its designed operating flow, the
critical orifice will allow only the designed operating flow to
pass through to the distal gas orifice. Alternatively, a safety
valve may be located in the proximal portion of the catheter shaft.
The safety valve would be designed to open if supplied with an
excess of pressure.
[0103] In addition, the nebulizing catheter may include a centering
device 50. The centering device 50 is located close to a distal end
of the nebulizing catheter shaft and helps to center and align the
distal end of the nebulizing catheter for improved performance, as
explained in more detail below.
[0104] According to one embodiment, the removable nebulization
catheter 20 is enclosed in a storage sheath 51. The storage sheath
51 may be similar to the type of storage sheaths used in
conjunction with suction catheters. The storage sheath is
preferably flexible, collapsible, or extendable to accommodate
insertion of the catheter. The storage sheath 51 may be connected
to the fitting 14. The storage sheath 51 can be used to receive the
nebulizing catheter 20 when it is being withdrawn from the
endotracheal tube 10. The storage sheath 51 is sealed and can
maintain the withdrawn nebulizing catheter in an isolated condition
when it is temporarily removed from the patient's respiratory
system. The storage sheath 51 also allows the physician to
re-insert the nebulization catheter into the patient. In this
manner, the nebulization catheter can be reused in a limited way
with respect to a patient and can be maintained in a sterile
condition while withdrawn from the patient. The storage sheath 51
may have a distal sleeve 53 that can slide along the shaft of the
nebulization catheter so that the nebulization catheter may be
advanced into the ventilation lumen of the endotracheal tube or
withdrawn into the storage sheath 51. The sleeve 53 may have a
close fitting seal 55 located therein which is designed to clean
and/or wash the nebulization catheter when it is withdrawn into the
sheath. Alternatively, a cleaning seal 55 may be located in the
port 16 of manifold fitting 14.
[0105] Another feature that may be used in conjunction with certain
procedures is radiation shielding. Some procedures for which the
nebulization catheter may be used may involve the delivery of
radioactive agents, e.g. tracers to the lungs. To minimize exposure
to radioactive materials, the nebulizing catheter may be provided
with shielding over all or a significant portion of the overall
length of the catheter. Shielding may also be provided at the
liquid source reservoir.
[0106] The nebulizing catheter is preferably constructed of a
biocompatible, chemically resistant polymer in order that it is
suitable for use with a wide variety of drugs. The catheter shaft
is preferably clear to allow visualization of contaminants or
blockages of the interior lumens. Also, the portion of the catheter
shaft that forms the liquid lumen 33 is preferably composed of a
relatively non-compliant material. In a present embodiment, the
catheter shaft is composed of a polymer such as polyethylene or
nylon. A polymer tubing is extruded with multiple lumens to be used
for the separate gas and liquid lumens. In order to produce a
nebulization catheter with the tapered distal section 40, a
multi-lumen extruded tubing may be drawn down in a portion thereof
to form the tapered distal section 40. The draw down ratio may be
selected to provide a nebulization catheter shaft with the desired
dimensions. The draw down process serves to make the lumens smaller
in size distally as well as closer together while maintaining the
proximal cross sectional profile of the multi-lumen tubing. The
larger proximal profile provides for greater pushability in the
catheter shaft and facilitates manufacturing by making the manifold
connection easier. The draw down ratio used on the extruded polymer
tubing may be on the order of 2-to-1, 5-to-1, or even as high as
20-to-1 or higher. Prior to drawing down, the extruded polymer
tubing is preferably exposed to high energy radiation to crosslink
the polymer molecules to provide for favorable material properties,
such as the ability to maintain orifice dimensions and tolerances.
The radiation may have an energy of approximately 10-700 kgy. After
the crosslinking step, the tubing is heated to its transition
temperature between its melt and glass states, and is drawn down by
the desired ratio.
[0107] As an alternative to drawing down the extruded tubing, the
multi-stage nebulization catheter shaft may be formed by a bubble
extrusion process wherein the desired tapered distal section is
formed directly in the shaft as it is being extruded. Again, this
process may be used for manufacturing efficiency and convenience.
As another alternative, the multi-stage shaft may be formed by a
combination of both bubble extrusion and drawing down. Still
another alternative for forming the desired tapered profile for the
nebulizing catheter shaft is to use a material that can be cold
drawn in order to cause a sharp neck down in diameter, such as a
linear low density polyethylene. Although the process for forming
the tubing is particularly suited for producing a nebulization
catheter shaft for use in delivering medicine to the respiratory
tract, it should be understood that the process could be used to
produce aerosol nozzles for non-medical purposes as well.
[0108] Alternatively, all or part of the nebulization catheter
shaft can be molded, especially at locations where close tolerances
are preferred such as at the tip.
[0109] After the shaft is formed with the desired stages, it is cut
and assembled with the other components of the nebulizing catheter.
Although the nebulization catheter is preferably constructed of a
polymer, in an alternative embodiment it could be formed of other
materials such as a metal, especially a malleable metal to
facilitate drawing, shaping or forming orifices. During the
manufacturing process, the nebulizing catheter may be
pre-sterilized by means of a conventional process, such as a gamma
ray or electron beam. The nebulizing catheter is preferably
disposable after use with a single patient, but may be reused to a
limited extent with a single patient provided that contamination
can be prevented such as through the use of the sheath 51,
described above. The nebulizing catheter shaft preferably possesses
torsional rigidity so that rotation of the proximal end is
transmitted at a 1:1 ratio to the distal end. The nebulizing
catheter may also be provided with an antiseptic coating.
[0110] Drug delivery rates are closely related to the particle size
with larger particles providing greater delivery rates. The
embodiments of the nebulization catheter described herein have the
capability of generating particle distributions with a GSD between
2 and 2.5. Drug delivery rates in a range between approximately 5
and 1000 mg (0.005-1.0 ml) per minute may be obtained. A variety of
particle size distributions can be generated at most flow rates
through selection of the catheter type and aerosol volume output.
An aerosol of this type can be generated with the nebulization
catheter using a gas flow rate as low as 0.1 liter/minute.
[0111] There are a number of factors that affect the particle size
generated. These factors include: (1) the gas orifice diameter, (2)
the liquid orifice diameter, (3) the liquid delivery tube outer
diameter and geometry, (4) the distance between the gas and liquid
orifices, (5) the rate of gas delivery, and (6) the pressure of the
liquid. Of course, the size of the solid particles in suspension,
if present, in the liquid are a defining aspect of the aerosol
particle size generated. In addition, there are other factors that
affect the aerosol particle size such as the characteristics of the
liquid, e.g. viscosity, suspension, surface tension and the
composition of the driving gas, however, these factors affect the
particle size of the aerosol generated to a lesser degree. By
selectively varying these parameters, the size and size
distribution of the aerosol particles can be changed from less than
a micron to at least 10 microns.
[0112] The embodiments of the present invention, described herein
are suitable for delivery of an aerosol by nebulization with a
volumetric particle size distribution comparable to other
nebulization systems. Further, by generating an aerosol at a
location in the trachea or even deeper in the bronchi, impaction
losses in tract can be avoided. By reducing impaction losses, it
may be acceptable to use larger particle sizes (e.g. greater than 5
microns). The combination of lower impaction losses and larger
particle sizes may provide higher effective delivery rates than
prior systems. Reducing impaction losses would enable an embodiment
of the nebulization catheter to provide acceptable delivery rates
with aerosol particle sizes greater than 5 microns.
[0113] Referring to FIGS. 3-5, there is depicted a further
embodiment of the present invention. According to the embodiment of
FIGS. 3-5, there is provided an endotracheal tube 52 and a
nebulizing catheter. The nebulizing catheter may be similar to the
nebulizing catheter 20 shown in FIGS. 1 through 3. In the
embodiment of FIGS. 3-5, the endotracheal tube 52 has an auxiliary
lumen 56 in addition to its main ventilation lumen 60. Some
endotracheal tubes provide auxiliary lumens through the shaft wall.
The auxiliary lumen 56 is preferably sized and adapted to receive
the separate nebulization catheter 20. This embodiment provides
many of the same advantages as the embodiment of FIGS. 1 through 3.
In addition, in this embodiment, the auxiliary lumen 56 may be
provided with a distal aperture 64 that facilitates locating and
aligning the distal end of 37 the nebulizing catheter 20 at a
desired location for nebulization purposes.
[0114] In the embodiments of the invention shown in FIGS. 1-5, the
nebulizing catheter 20 is shown used in conjunction with an
endotracheal tube either of a conventional type 10, as in FIGS. 1
and 2, or of a type especially designed for use with the nebulizing
catheter such as endotracheal tube 52 of FIGS. 3-5. The nebulizing
catheter 20 according to an embodiment of the present invention may
also be used without a separate endotracheal tube, i.e. the
nebulizing catheter may be used on a patient who is not intubated,
as shown in FIG. 6. If used on a spontaneously breathing patient
(without an endotracheal tube), the patient should be properly
anesthetized and/or that the airway passage of the patient be
topically anesthetized. The nebulizing catheter 20 is positioned in
the respiratory system of a patient directed past the carina 68
into one of the bronchi 72 of the lungs. Alternatively, the
nebulizing catheter 20 may also be positioned proximal of the
carina in the trachea, as desired. Embodiments of the nebulizing
catheter may also be used on patients who have had tracheotomies or
who have tracheotomy tubes.
[0115] In the embodiment of FIG. 6, a guiding sheath 73 is used.
The guiding sheath 73 is used to help position the nebulizing
catheter 20 in the respiratory system of the patient. The guiding
sheath 73 includes a lumen through which the nebulization catheter
20 can be advanced into a desired bronchi site. To facilitate
positioning the nebulization catheter, the guiding sheath 73 may
have a pre-shaped distal end to facilitate locating the sheath in
the desired airway passage. Alternatively, the guiding sheath 73
may have a distal end that can be formed into a desired shape by
the physician just prior to insertion. The guiding sheath 73
differs from the endotracheal tube 10 of FIGS. 1-5 in that it may
have a smaller outside diameter so that it can be advanced into
smaller airway passages deep in the patient's bronchi past the
carina 68. The inside diameter of the sheath 73 is large enough to
advance the nebulization catheter. The guiding sheath 73 is
particularly useful when the nebulization catheter 20 is being
located deep in the patient's lungs, or when the nebulization
catheter is used without an endotracheal tube. The guiding sheath
73 may also be used with an endotracheal tube through the
ventilation lumen thereof. The guiding sheath is preferably
composed of a torsionally rigid material so that the distal end of
the guiding sheath is responsive to rotation at the proximal
end.
[0116] Referring to FIGS. 7 and 8, there is shown another
embodiment of the nebulizing catheter. In the embodiment of FIG. 7,
a nebulizing catheter 76 includes an occlusion balloon 80 located
on a distal exterior surface of the nebulizing catheter shaft body
84. The nebulizing catheter 76 may include an additional lumen 88,
as shown in FIG. 8, located therethrough and communicating with the
interior of the balloon 80 for providing inflation fluid, i.e.
preferably gas, to expand the occlusion balloon 80. This lumen 88
for inflation fluid is in addition to the lumens 92 and 96 in the
catheter shaft 84 used for conveyance of the liquid medicine and
pressurized gas, respectively. The occlusion balloon 80 may be used
to position the nebulizing catheter in the appropriate respiratory
branch 100, center the nebulizing catheter tip for proper
orientation, and isolate a particular bronchus, as needed. The
embodiment of the nebulizing catheter 76 shown in FIG. 7 may be
used with an endotracheal tube in a manner similar to that shown in
FIGS. 1-3, or alternatively it may be used without a separated
endotracheal tube, similar to the embodiment of FIG. 6. When used
without a separate endotracheal tube, the nebulizing catheter 76 of
FIG. 7 could be used for the purpose of selective ventilation of
one of the bronchi of the lungs even without providing
aerosolization. Alternatively, the nebulization catheter 76 could
provide aerosolization on an intermittent basis with continuous
ventilation. If the nebulization catheter is used to provide
ventilation as well as aerosolized medication, the ventilation
regime can be tailored to maximize aerosol transport.
[0117] In addition, to further facilitate positioning and
placement, the nebulizing catheter 76 may be used with a guide wire
104. The nebulizing catheter may be provided with a separate guide
wire lumen 108 to receive the guide wire 104, or alternatively, the
guide wire may use one of the existing lumens that is also used for
either the pressurized gas or the liquid or alternatively the guide
wire may be incorporated and fixed into the nebulizing catheter so
that it is non-removable. The guide wire, whether of the removable
type of the type that is fixed to the nebulizing catheter, may also
be steerable, i.e. so that it can be guided from a proximal end to
access the appropriate location in the lungs. The steering
apparatus may utilize selective tensioning of a pull wire, etc.
from a proximal end. If the guide wire is of the separate removable
type, it may be withdrawn after it has been used to position the
distal tip of the nebulizing catheter so as to avoid interfering
with aerosol delivery. In addition, the distal tip of the guide
wire or nebulization catheter may be pre-shaped or shapable by the
physician so as to impart an appropriate curve or bend to
facilitate access to the desired airway.
[0118] Referring to FIG. 9, there is shown another embodiment of a
nebulizing catheter of FIG. 7. The embodiment of FIG. 9 is similar
to the embodiment of FIG. 7 with the exception that the separate
guide wire 104 is received in a loop 106 located close to a distal
end of the nebulizing catheter 76. Proximal of the loop 106, the
guide wire 104 is positioned adjacent to the shaft 84 of the
nebulizing catheter 76. Instead of a loop 106, the guide wire may
be received in a short lumen located in the distal end of the
nebulizing catheter.
II. Generation of Aerosol Plume
[0119] It has been discovered that the shape of the aerosol plume
can be a significant factor affecting the rate and efficacy of the
delivery of medication by an aerosol. In general, it is preferable
to generate an aerosol that has a shape that minimizes particle
impaction near the distal tip of the nebulizing catheter, given the
location of the tip and the airflow conditions around it. For
example, if the aerosol plume is wide, a portion of the drug may be
wasted in the end of the endotracheal tube or on the wall of the
trachea or other airway passage. On the other hand, if the plume is
too narrow or the velocity too high, a portion of the drug may
impact excessively on the patient's carina. In general, a low
aerosol particle velocity is desirable. One of the reasons for this
is to avoid impacting the carina with the discharge of high
velocity aerosol particles. In addition, it is also generally
desirable to have as wide an aerosol plume as possible while
avoiding significant impact with the walls of either the
endotracheal tube or the respiratory airway passage. The effects of
aerosol plume velocity and geometry are related to anatomical
factors. In some circumstances, e.g. away from the carina, a
narrow, fast aerosol plume may be preferable to a slower, wider
plume.
[0120] Regarding the embodiments described below, certain of the
embodiments may be preferable from the standpoint of versatility,
i.e. they may be able to deliver a variety of medications having
different viscosities, suspensions, surface tensions, etc. Others
of the embodiments may be more suitable for the delivery of
specific types of medications or the delivery of particles of
certain sizes.
[0121] Referring to FIG. 10, there is shown a tip configuration for
a nebulizing catheter 112. The nebulizing catheter 112 may be
either a stand alone-type of nebulizing catheter, similar to the
catheters shown in FIGS. 6 and 10, or may be incorporated into an
endotracheal tube either removably, as in FIGS. 1-5, or
non-removably. In the embodiment of FIG. 10, the nebulizing
catheter 112 has a coaxial configuration. Specifically, the
nebulizing catheter 112 includes an outer tubular member 116
defining a lumen 120 and an inner tubular member 124 also defining
a lumen 128. The inner tubular member 124 is located in the lumen
120 of the outer tubular member 116. According to the embodiment
shown FIG. 6, pressurized gas is conveyed in the annular region
defined between the inner and outer tubular members. Liquid
medication is conveyed in the lumen 128 of the inner member 124. As
shown in the embodiment of FIG. 10, a distal end of the outer
tubular member 116 is approximately adjacent to a distal end of the
inner tubular member 124. In the embodiment of FIG. 10, the outer
tubular member 116 has an O.D. of approximately 0.008 inches and an
I.D. of approximately 0.006 inches. The inner tubular member 124
has an O.D. of approximately 0.003 inches and I.D. of approximately
0.0015 inches. Both the inner tubular member 124 and the outer
tubular member 116 have larger dimensions proximal of the distal
tip portion. Along a main shaft portion proximal of the distal tip,
the outer tubular member 116 has an O.D. of approximately 0.115
inches and an I.D. of 0.080 inches and the inner tubular member 124
has an O.D. of approximately 0.060 inches and an I.D. of 0.050
inches.
[0122] The embodiment of FIG. 11 shows a tip of a nebulizing
catheter 132. This embodiment is similar to the embodiment of FIG.
10. The tip 133 is formed with a plurality of lumens terminating in
a plurality of orifices. An inner lumen 134 is used to convey the
liquid medication and the surrounding lumens 135 convey the
pressurized gas used to nebulize the liquid. This embodiment has
the advantage that the orifice of the liquid lumen 134 is centered
with a fixed spacing relative to the orifices of the gas lumens 135
around it. In the embodiment of FIG. 11, the multiple lumen
construction may extend all the way back to the proximal end of the
nebulizing catheter 132 or alternatively, only a distal segment may
have the multiple gas lumen configuration in which case the
pressurized gas may be conveyed through a single proximal lumen
that connects to the multiple distal lumens.
[0123] FIGS. 12 and 13 show an alternative embodiment 136 of the
multiple lumen nebulization catheter in FIG. 11. The embodiment in
FIGS. 12 and 13 is useful when it is desired to provide the aerosol
medicine with a pulsed delivery. The pulsed delivery may be timed
to coincide with the inhalation of the patient so that aerosol is
not wasted when the patient is exhaling. A potential drawback with
pulsed delivery is that the aerosol may drool from the tip of the
nebulizing catheter when the pressure being applied to the liquid
is reduced to effect the pulsation. To avoid this potential
problem, the nebulizing catheter 136 provides for closure of the
liquid lumen when the pressure being applied to it is reduced. As
in the previously described embodiment, the nebulization catheter
136 in FIGS. 13 and 14, has a centrally located lumen 137 for
delivery of a liquid medicine and a plurality of lumens 138
surrounding the central lumen 137 for conveyance of a pressurized
gas to nebulize the liquid at the distal orifice 139. In this
embodiment, the catheter 137 is formed of a low compliance material
in the outer wall area 140 and a relatively high compliance
material in the area 141 surrounding the centrally located liquid
lumen 137. These differing compliance characteristics may be formed
in the catheter shaft by coextruding a single tube with different
materials. When using the embodiment of FIGS. 12 and 13, a
constant, relatively high pressure is applied to the gas in the
lumens 138. Liquid medicine is delivered via the lumen 137 and
pressure pulses are applied to the liquid from an external delivery
source, such as a pump. When the pressure in the liquid lumen 137
is low, the high pressure in the gas lumens 138 deform the
compliant inner material 141 thereby compressing the liquid lumen
137 and closing it off, as shown in FIG. 12. When a pressure pulse
is applied to the liquid in the lumen 137, it overcomes the
compressive forces from the gas lumens 138 allowing the lumen 137
to open and permitting the liquid medicine to be delivered to the
distal orifice 139 to be nebulized, as shown in FIG. 13. In this
manner, the embodiment of FIGS. 12 and 13 provides for pulsed
liquid nebulization with reduced possibility of drooling.
[0124] Another feature shown in FIGS. 11 and 12 is a porous plug
142 located in the liquid orifice 139. This porous plug may be made
of a felt-like material and may assist in the production of fine
aerosol particles.
[0125] The embodiment of FIG. 14 shows a distal tip of another
embodiment of the nebulizing catheter. In this embodiment, a
nebulizing catheter 148 includes a main shaft section 152 and a
distal shaft section 156. The distal shaft section 156 is tapered
to a tip 160. At the tip 160, a liquid orifice 164 is surrounded by
a plurality of gas orifices 168. In a preferred embodiment, there
are six gas lumens terminating in the six orifices 168. In this
embodiment, the liquid orifice 164 has a diameter of approximately
0.002 inches and the gas orifices 168 each have a diameter of
approximately 0.002 inches. This embodiment is similar to the
embodiment of FIG. 11 except that the distal section 156 provides
for a reduction in the tip size and corresponding modification of
the nebulization plume properties. This reduction is preferable as
it provides a smaller orifice size.
[0126] The embodiment of FIG. 15 shows a distal portion of a
nebulizing catheter 172. In this embodiment, the nebulizing
catheter includes a proximal shaft section 176 and a distal shaft
section 180. The proximal shaft section 176 includes a plurality of
lumens 184. A central one 188 of the plurality of lumens 184 is
used to convey liquid medicine and the remainder of the lumens
surrounding it are used to convey gas. The distal shaft section 180
connects to the distal end of the proximal shaft section 176 and
defines a tapered cavity 192 between the distal end of the proximal
shaft section 176 and a distal orifice 196. At least one of the
plurality of lumens 184 is used to convey a pressurized gas that is
discharged into the cavity 192. A tubular extension 200 extends the
liquid lumen through the cavity 192 and distally out the orifice
196. The orifice 196 is sized to provide an annular region around
the tubular extension 200 to permit the pressurized gas to flow
through to nebulize the liquid medication that exits a distal
orifice 204 of the tubular extension 200. In a preferred
embodiment, the distal shaft section 180 is composed of stainless
steel and the orifice has an I.D. of 0.025 inches. The tubular
extension 200 has an O.D. of 0.012 inches and an I.D. of 0.007
inches. This embodiment has the advantage of combining a relatively
small distal profile with a relatively large proximal flow channel.
Another advantage of this embodiment it that it provides for a
balanced airflow around the liquid orifice 204.
[0127] FIG. 16 shows yet another embodiment for a tip for a
nebulizing catheter. In FIG. 16, a nebulizing catheter 208 has a
coaxial configuration similar to the embodiment of FIG. 10
(although it could also have a configuration similar to that of
other coaxial embodiments, e.g. FIG. 11, 14, or 15). In FIG. 16, a
thin solid wire or filament 212 is located at a distal end of a
liquid orifice 216 located at a distal end of an inner tubular
member 220. The tapered wire 212 extends a short distance distally
from the distal end of the inner tubular member 220. The tapered
wire 212 is located with respect to the liquid orifice 212 so that
liquid being conveyed through the inner member 220 continues to
flow distally of the distal orifice 216 along the wire 212, i.e.
adhering to it by surface tension. Of course, once the liquid
reaches a distal tip 224 of the wire 212, it is entrained and
nebulized by the gas flow from the annular region 228 defined
between the inner tubular member 220 and an outer tubular member
232. As mentioned above, one of the factors that affects the
nebulization plume particle size and geometry is the size of the
distal liquid orifice. In general, a smaller liquid orifice
produces smaller particles and a narrow aerosol plume cone. In the
embodiment of FIG. 16, the thin wire 212 carries only a small
amount of liquid along it so that it functions similarly to an
orifice of a very small size. Accordingly, the embodiment of FIG.
16 has the potential for producing an aerosol of very fine
particles. In the embodiment of FIG. 16, the outer tubular member
has an I.D. of approximately 0.020 inches. The inner tubular member
has an I.D. of approximately 0.006 inches. The thin wire has an
O.D. of approximately 0.002 inches. The wire or filament 212 may be
composed of a metal wire or a polymer wire, such as a polyolefin
fiber like Spectra fiber. Alternatively, the filament 212 may be
composed of a porous or felt-like material, such as nylon or Porex,
in which case it may be wider in diameter than if made of a solid
material.
[0128] FIG. 17 shows an alternative embodiment of the embodiment of
FIG. 16. In FIG. 17, there is a distal end of a nebulizing catheter
236 having a tapered wire or filament 240 located at the distal end
of a lumen of an inner tubular member 244. The tapered wire 240 in
this embodiment has a curved shape that is designed to whip in a
spiral when it is in a flow of air. In the embodiment of FIG. 17,
when pressurized gas flows through the annular region 248, it
causes the tapered wire 240 to whip around with a spiral motion.
The length of the wire 240 is chosen so that it does not impact the
wall of the trachea or other airway passage when it moves in a
spiral whipping motion. In one embodiment, the wire 240 has a
length of approximately 1-2 mm. The tapered wire 240 carries the
liquid out to its tip for entrainment, and the nebulization plume
is formed with a conical shape. The width of the plume may be
changed by changing the length of the filament 240. The speed of
the spiral motion can be controlled by appropriate selection of
wire stiffness and air foil shape. In general, the spiral plume
produced by the embodiment of FIG. 17 will be wider than the
embodiment of FIG. 16 and have less forward velocity. Both these
characteristics may be favored in a nebulization catheter.
[0129] FIGS. 18 and 19 show another embodiment of the nebulization
catheter. In this embodiment, a nebulization catheter 252 has a
coaxial configuration formed of an outer tubular member 256 and an
inner tubular member 260. A distal plug 264 fits into a distal end
of the annular region 268 forming the gas lumen. A plurality of
apertures 272 extend through the plug 264 to form distal gas
orifices. Located in a lumen 276 defined by the inner tubular
member 260 is a retractable wire or pin 280. The wire 280 is
preferably a solid wire of a rigid material. For example, the wire
may be composed of a metal, such as stainless steel, a polymer, or
a radiopaque material. A distal end 284 of the inner member 260 is
tapered and may extend distally of the plug 264 or alternatively
may extend only to the distal end of the inner tubular member 260
or even proximally thereof. The distal end of the inner member 260
terminates in a distal liquid orifice 285. A distal end 286 of the
wire 280 may also be tapered. The wire 280 is sized with respect to
the inner tubular member 260 so that the tapered distal portion 286
of the wire 280 seats against the tapered distal portion 284 of the
inner tubular member 260 and thereby seals a distal end of the
liquid lumen 276 in a manner similar to a needle valve. The wire
280 is retractable and in a preferred embodiment is operated to
reciprocate back and forth to pulse the delivery of liquid out the
distal end of the nebulizing catheter 252. The pulsing of aerosol
delivery may be adjusted to any suitable time period. In one
preferred mode of operation, the aerosol may be delivered only
during inhalation by the patient. If the nebulizing catheter 252 is
being used with an endotracheal tube and a ventilator, the pulsing
of the aerosol delivery may be timed to coincide with the patient's
inhalation by an appropriate connection with the ventilator. By
limiting the delivery of medicine to only the period of time when
the patient is inhaling, the medicine can be delivered more
efficiently and with less waste.
[0130] One preferred way to generate the pulsed aerosol plume with
the embodiment of FIGS. 18 and 19 is with a manifold arrangement
287. A proximal end of the wire 280 is fixed to an extendable
section 288 of the manifold 287. The wire 280 may be fixed by means
of an elastomeric seal 289. Pressurized gas is delivered to a port
290 of the manifold that communicates with the outer tubular member
256 and liquid medicine to be nebulized is delivered to a second
port 291 that communicates with the inner tubular member 260. The
liquid medicine also fills the volume 292 proximal of the port 291
in the expandable section 288. The wire 280 is connected to the
manifold so that the distal end of the wire is biased against the
distal end of the inner tubular member by the resilience of the
inner tubular member 260 and/or the expandable section 288. Pulsed
pressurization of the liquid medicine from the source causes the
extendable section 288 to reciprocate back and forth as shown by
the arrow 293. Since the proximal end of the wire 280 is attached
to the expandable section 288 proximal of the port 291, application
of pressure pulses to the liquid causes the proximal end of the
wire 280 to reciprocate back and forth as well. This causes the
distal end of the wire 280 to reciprocate back and forth in the
seat 284. Application of pressure pulses to the liquid medicine can
be timed to coincide with the patient's inhalation. Alternatively,
instead of forming an expandable or compressible section at the
manifold, the shaft of the inner tubular member 260 may be formed
of a stretchable material so that pressurization of the liquid
causes retraction of the wire as the entire shaft elongates. Other
alternatives for effecting reciprocating operation of the wire 280
are use of an electro-mechanical, mechanical, hydraulic, or
pneumatic actuator to drive the wire. Aside from providing for
pulsed delivery of the aerosol, this embodiment of the nebulization
catheter has the further advantage that the reciprocating action of
the wire may assist in keeping the orifice free of any blockages
which may occur, especially with some viscous solutions or
suspensions.
[0131] In a manner similar to the embodiments 208 and 236 of FIGS.
16 and 17, in the embodiment 252 of FIGS. 18 and 19, the distal tip
of the retractable wire 292 can extend distally from the distal
liquid orifice 288 in order to minimize particle size, or
alternatively may not extend distally of the distal liquid orifice
292. In one embodiment, the distal tip of the retractable wire may
extend distally of the liquid orifice 288 by approximately 0.2
mm.
[0132] FIG. 20 shows another embodiment of a nebulizing catheter.
In this embodiment, a nebulizing catheter 296 has a main shaft
portion 300 with a gas lumen 304 adjacent to a liquid lumen 308.
The gas and liquid lumens 304 and 308 flow into a distal cavity
312. The distal cavity 312 is formed by an outer tubular extension
316 that extends distally over and past a distal end 320 of the
main shaft portion 300. A filter 324 is located in the liquid lumen
308 to filter out any particles in the liquid. The liquid lumen 308
has a step down in diameter immediately distal of the location of
the filter 324. An insert plug 328 is located in a distal end of
the outer tubular extension 316. The insert plug 328 (which may be
a sapphire jewel, for example) has an aperture 332 through it that
forms an exit orifice from the cavity 312. The insert plug 328 has
a conical shaped proximal profile facing the cavity 312. An inner
tubular extension 336 fits into the stepped down portion of the
liquid lumen 308 and extends the liquid lumen 308 into the cavity
312. A distal end 340 of the inner tubular extension 336 terminates
in the cavity 312. Since the gas lumen 304 exits into the cavity
312, nebulization of the liquid takes place at the tip of the inner
tubular extension 336 inside the cavity 312. This region of the
cavity 312 is a positive pressure region due to the relative sizes
and locations of the apertures. The positive pressure in this
region may have the effect of reducing drooling of the liquid
medicine as it leaves the orifice of the tubular extension 336. The
aerosol exits the catheter 296 via the aperture 332 and the aerosol
plume is defined in part by the positive pressure in the cavity 312
and the aperture size. In this embodiment, the main shaft portion
and the tubular extension are composed of a suitable plastic such
as polyethylene. The filter is composed of multiple 50 .mu.m I.D.
tubes or similar course filter material. The gas and liquid lumens
may each have an I.D. of 0.010 to 0.015 inches. The inner tubular
extension 336 may be formed of polyimide tubing with an I.D. of
0.004 inches and an O.D. of 0.010 inches. The outer tubular
extension 316 may be formed of a heat shrunk tubing, such as
polyethylene. The plug 328 may have an O.D. 0.087 inches and the
aperture 332 in the plug 328 may have a diameter of 0.007
inches.
[0133] FIG. 21 shows another embodiment of the nebulizing catheter.
This embodiment is similar to the embodiment 296 shown in FIG. 20
and accordingly the components are numbered similarly. The
embodiment of FIG. 21 differs from the embodiment of FIG. 20 in
that the distal end of the inner tubular extension 312 is located
in the aperture 332 of the insert plug 328. In the embodiment of
FIG. 21, the orifice 332 at the distal end of the tubular extension
336 is in a low pressure, high velocity region as compared to the
embodiment of FIG. 20. This has a corresponding effect on plume
size and shape as well as possible particle size.
[0134] FIG. 22 shows yet another embodiment for the nebulizing
catheter. In this embodiment, a nebulizing catheter 340 has a main
shaft portion 344 that has a gas lumen 348 and a liquid lumen 352.
The gas lumen 348 terminates distally in a gas orifice 356. Located
in the distal end of the liquid lumen 352 is a liquid tubular
extension 360. The liquid tubular extension 360 forms an angle so
that a distal liquid orifice 364 is in alignment with the flow of
gas out the distal gas orifice 356. In this embodiment, the liquid
lumen 352 has an I.D. in the range of 0.010 to 0.020 inches. The
gas lumen 348 has an I.D. of approximately 0.10 to 0.020 inches.
The liquid tubular extension 360 is formed of a stainless steel
tube with an O.D. of 0.018 inches and an I.D. of 0.012 inches. The
distal gas orifice 356 has an I.D. of 0.010 inches. The stainless
steel extension tube 360 forms a right angle so that the distal
liquid orifice 364 is at a right angle and aligned with the distal
gas orifice 356. The distal gas orifice 356 and the distal liquid
orifice 364 are positioned as close together as possible, and in
one embodiment, these orifices are approximately 0.010 inches
apart.
[0135] FIG. 23 shows an alternative embodiment of the nebulization
catheter shown in FIG. 22. In this embodiment, the nebulization
catheter 340 has an additional lumen 365. This additional lumen 365
may have an I.D. of approximately 0.020 inches. This additional
lumen 365 may be used for an optical fiber viewing scope 366 for
illumination and visualization of the distal end of the
nebulization catheter 340. The optical viewing scope 366 may be
permanently installed in the catheter 340 or preferably may be
removable. A distal end 367 of the lumen 365 is open or covered
with a transparent lens so that the area distal of the catheter 340
can be observed via an optical viewing device connected to a
proximal end of the optical fiber 366. This enables a physician to
observe the alignment of the distal end of the nebulization
catheter and also observe the nebulization when it occurs. The gas
orifice 356 may be located so that the pressurized gas that is
expelled helps to keep the distal end of the viewing lumen 365
clear. An optical fiber viewing channel may be incorporated into
any of the embodiments of the nebulization catheter disclosed
herein. When the additional lumen 365 is occupied by a removable
viewing scope, it may be used for other purposes such as pressure
sensing, gas sampling, over pressure relief, or other diagnostic or
therapeutic purposes. Alternatively, another lumen may be provided
for these purposes.
[0136] The embodiment of FIG. 23 also shows opposing orifices. As
in the embodiment of FIG. 22, a tubular extension 360 extends
distally of the end of the catheter shaft and is oriented at an
angle, e.g. 90 degrees, to the direction of the axis if the
catheter shaft. The tubular extension 360 opens to a distal liquid
orifice 364 from which the liquid being conveyed in the lumen 352
exits. In this embodiment, a second tubular extension 363
communicates with the gas lumen 348 and opens to a distal gas
orifice 367. The second tubular extension 363 is also oriented
relative to the axis of the catheter shaft, e.g. by 90 degrees, so
that is aimed toward the distal liquid orifice 364 in order to
nebulize the liquid exiting from the liquid orifice 367.
[0137] FIG. 24 shows still another embodiment of the nebulizing
catheter. In this embodiment, a nebulizing catheter 368 has a main
shaft section 372 with a gas lumen 376 and a liquid lumen 380.
Tubular extensions 384 and 388 extend the gas and liquid lumens 376
and 380 from the main shaft section 372 to a distal tip of the
catheter 368. The distal portion of the shaft forms a tapered
region 392 that surrounds the tubular extensions 384 and 388 and
causes them to be angled toward each other. The tubular extension
388 for the liquid lumen 380 extends slightly distally of the
distal end of the tubular extension 384 of the gas lumen 376 so
that a distal liquid orifice 396 is in alignment with the flow of
gas from a distal gas orifice 400. In this embodiment, the distal
liquid orifice 396 has an O.D. of 150 microns and an I.D. of 20
microns. The gas orifice 400 has an I.D. of approximately 0.018
inches.
[0138] FIGS. 25 and 26 show an alternative embodiment of the
nebulizing catheter 368 shown in FIG. 24. In FIGS. 25 and 26, the
tubular extensions 384 and 388 of the gas lumen 376 and the liquid
lumen 380 are formed with sealable tips. Specifically, the gas
tubular extension 384 has a sealable tip 408 and the liquid tubular
extension 388 has a sealable tip 412. Alternatively, only the
liquid lumen 380 has the sealed tip 412 and the gas lumen 376 has
an open distal orifice. The sealable tips may be formed by heating
the material from which the tubular extensions are made to reform
the walls of the plastic material so as to form a closed slit. This
is represented in FIG. 26. When pressurized gas and liquid are
conveyed through the lumens 376 and 380, the slits forming the tips
408 and 412 dilate thereby permitting the gas and liquid to exit to
from the aerosol, as illustrated in FIG. 25. However, when the
pressure in the lumens 376 and 380 falls below a threshold, the
tips 408 and 412 close thereby sealing off the lumens, as
illustrated in FIG. 26. The embodiment 404 of the nebulizing
catheter is used with pulsation of the gas and/or liquid supplies.
In order to pulse the generation of aerosol to coincide with a
patient's inhalation, the pressure to the gas and/or the liquid
lumens can also be pulsed. When the pressure in either of the
lumens falls below a threshold, the tips 408 or 412 close. By
closing off the flow of liquid at the tip 412 during the period
when the aerosol is not being generated, it is possible to reduce
any drooling from the tip of the catheter.
III. Nebulization with Counterflow
[0139] As mentioned above, control of nebulized particle size and
plume shape are important considerations affecting the efficacy of
the therapy. In many applications, it is preferable to have as
small a particle size as possible combined with as little forward
velocity as possible. Some of the embodiments described below
accomplish these objectives through use of counterflow
arrangements.
[0140] FIG. 27 shows a nebulization catheter 416 that can be
located inside of an endotracheal tube as in the previously
described embodiments. The nebulization catheter 416 has a coaxial
tubular arrangement with an outer tube 417 surrounding an inner
tube 418 so that a liquid delivered from a distal liquid orifice
419 of the inner tube 418 is nebulized by the flow of a pressurized
gas delivered in a distal direction from the annular region between
the inner and outer tubes at the distal orifice 420 of the outer
tube 417. In addition, another lumen 428 extends through the shaft
of the nebulization catheter 416. This additional lumen 428
connects to a distal tubular extension 432. The tubular extension
432 extends distally of the distal end of the nebulization catheter
416. A distal end 436 of the distal tubular extension 432 curves
back on itself so that a distal orifice 440 of the tubular
extension 432 is oriented in a proximal direction back at the
orifices 419 and 420 of the inner and outer tubes. The additional
lumen 428 also carries a pressurized gas which is directed in a
proximal direction by the orifice 440 against the direction of the
aerosol plume generated by the gas and liquid exiting the orifices
419 and 420. The gas from the additional lumen 428 presents a
counterflow to the gas from these orifices thereby slowing down the
velocity of the particles generated from these orifices. In a
preferred embodiment, the distal tubular extension 432 may be
formed of a suitable material such as stainless steel needle stock.
The O.D. of the nebulization catheter in this embodiment may be
similar to the other nebulization catheter embodiments described
above, e.g. O.D of approximately 0.038 inches. The distal tubular
extension 432 may have an O.D. of approximately 0.013 inches and an
I.D. of approximately 0.009 inches. In this embodiment, the outer
tubular member of the nebulization catheter may have an O.D. of
approximately 0.013 inches and an I.D. of approximately 0.009
inches and the inner tubular member may have an O.D. of
approximately 0.003 inches and an I.D. of approximately 0.0015
inches.
[0141] FIG. 28 shows another embodiment of the present invention
for a nebulizing catheter 448 that incorporates a counterflow
arrangement. Like the embodiments described above, in this
embodiment the nebulizing catheter 448 may be located in an
endotracheal tube (not shown). The nebulization catheter 448 has a
distal section 452 that curves back on itself. The nebulization
catheter 448 has distal orifices 453 and 454 that generate a plume
of nebulized particles in a reverse, i.e. proximal, direction. Also
located in the nebulization catheter 448 is another lumen 456 for
carrying a pressurized gas. The additional lumen 456 has a distal
orifice 460 oriented in a distal direction. The distal orifice 460
of the additional lumen 456 is aligned with respect to the distal
orifices 452 and 453 of the nebulization catheter 448 so that the
flow of gas from the additional lumen 456 slows down the velocity
of the nebulization plume generated from the nebulization catheter
448. The aerosol plume generated by the nebulization catheter
reverses direction and is delivered to the lungs carried by the
inhalation of air through the endotracheal tube or by the flow of
gas from the additional lumen 456 or a combination thereof.
[0142] FIGS. 29 and 30 show another embodiment of a counterflow
nebulization catheter arrangement. In FIGS. 29 and 30, a nebulizing
catheter 464 is used with an endotracheal tube 468. A nebulization
catheter 464 has a distal tip 472 from which a liquid medicine
delivered from a distal liquid orifice is nebulized by a flow of
pressurized gas from a gas orifice located adjacent to the liquid
orifice. The nebulizing catheter 464 shown in FIG. 30 extends
distally of the endotracheal tube 468 and has a distal section 476
that curves back on itself. The nebulization catheter 464 has
distal orifices that generate a plume of nebulized particles in a
reverse, i.e. proximal, direction back toward the distal opening of
the endotracheal tube 464. In order to maintain a proper reverse
orientation and to prevent snagging, the nebulization catheter 464
includes a wire 480 that extends from the tip 472 of the
nebulization catheter 464. The wire 480 is secured to a portion of
the shaft of the nebulization catheter proximal of the tip. The
wire 480 can be secured by means of a heat shrunk tube 484 located
on a shaft 488 of the catheter to hold the end of the wire 480.
Although some aerosol may impact the wire 480, a wire having a
small diameter is used to minimize losses due to such impaction.
Moreover, the overall improved efficiency due to reduction in
aerosol impaction on the walls of the trachea or other airway
passage is expected to more than compensate for any losses due to
impaction on the wire 488.
[0143] In the embodiment shown in FIG. 30, the nebulization
catheter 464 directs a nebulization plume in a reverse direction
back toward the distal opening of the endotracheal tube 468. The
nebulization plume from the nebulization catheter encounters the
flow of air from the endotracheal tube 468 during the inhalation
phase of the patient. The inhalation of air through the
endotracheal tube 468 causes the nebulized medicine to reverse
direction and carries it to the lungs. It is noted that the
reversal of direction of the nebulization plume has the effect of
minimizing the aerosol particle velocity. It is also noted in the
embodiment shown in FIG. 30 that the endotracheal tube 468 is
provided with an inflatable cuff 492 located around the distal
portion.
IV. Other Nebulization Catheter Embodiments
[0144] In the embodiments described above, the velocity of the
nebulization plume was reduced by use of a counterflow of gas in an
opposite direction. In the embodiment of FIGS. 31 and 32, the
velocity of the nebulization particles is reduced in another
manner. In FIG. 31 a nebulization catheter 496 has a liquid lumen
500 terminating in a distal liquid orifice 504 and a one or more
gas lumens 508 terminating in one or more distal gas orifices 512.
The liquid delivered through the liquid lumen 500 is nebulized by
the pressurized gas flowing out the plurality of gas orifices 512.
The nebulization catheter 496 also includes one or more additional
lumens 516 that terminate in additional distal orifices 520. These
lumens 516 are used to deliver a vacuum (negative pressure) at the
distal orifices 520. The vacuum is provided by a suitable vacuum
source (not shown) connected to proximal ends of the additional
lumens 516. The vacuum delivered by the additional lumens 516 helps
withdraw the pressurized gas delivered by the lumen 508 after it
has nebulized the liquid delivered by the liquid lumen 500. Without
the vacuum provided by the additional lumens 516, the pressurized
gas delivered by the distal gas orifices 512 may continue to impart
energy to the nebulized liquid particles delivered by the distal
liquid orifice 504 thereby causing them to be propelled with a
forward velocity. Instead, the vacuum scavenges at least some of
the pressurized gas after it has nebulized the liquid so that the
forward velocity of the liquid particles can be reduced. In order
to facilitate scavenging of the pressurized gas, the distal liquid
orifice 504, the distal gas orifices 512, and the distal vacuum
orifices 520 all open into a distal cavity 524 formed by an outer
tubular extension 528 of the nebulizing catheter 496. The distal
extension 528 has a closed distal end 532 with a small aperture 536
located therein to emit the nebulized liquid particles with a low
forward velocity. With the nebulizing gas removed, the aerosol
particles are carried forward primarily only by their inertia.
[0145] The embodiment of the nebulization catheter 496 shown in
FIG. 31 includes a vacuum line 516 as a means to reduce the forward
velocity of the nebulization plume. Provision of vacuum line 516 to
the tip of a nebulization catheter 496 can serve an additional
function of balancing the gas flow and pressure delivered to the
airway in which the nebulization catheter is located. This may be
useful to prevent excess airway pressure generated by the catheter
flow particularly in smaller airways or where a neutral flow
balance may be desired. This may particularly be desired when the
nebulization catheter is provided with an inflatable cuff that
occludes the airway passage at the distal end of the nebulization
catheter. The flow balance may be controlled with a closed or
partially closed pumping system where a gas pump 537 with a single
intake and outlet would be connected to the respective vacuum and
gas supply lumens 516 and 508 of the catheter. Both the driving gas
and vacuum would be balanced and regulated by the pump speed. A
vacuum or pressure vent port 538 could be incorporated into the
respective vacuum or pressure lines if a positive or negative flow
balance was desired. If flow balance is a concern, but not velocity
reduction, it is not important where the air flow is removed at the
distal tip of the catheter and accordingly, the distal end
extension 532 may not be needed. Alternatively, a flow balance may
be maintained with separate a pressure and vacuum source through
the use of regulators, restrictive capillary tubes or orifices, or
flow sensors and flow control valves incorporated into the pressure
and vacuum supply lines.
[0146] FIG. 33 shows another embodiment of a nebulization catheter
540 that incorporates a feature to reduce the forward velocity of
the nebulized liquid particles. The nebulization catheter 540 has a
main shaft portion 544 having a liquid lumen 548 and a pressurized
gas lumen 552. The lumens 548 and 552 terminate in distal orifices
556 and 560. The pressurized gas flow from the orifice 560
nebulizes the liquid exiting from the orifice 556. The nebulization
catheter 540 includes a distal spacer tube 564. The spacer tube 564
has a length of approximately 2-3 mm and an inside diameter larger
than the outside diameter of the nebulization catheter shaft 544.
Because the inside diameter of the spacer tube 564 is larger than
the airflow lumen and orifice, the velocity of air and entrained
particles is reduced as they pass through the spacer tube 564 and
out a distal opening 568 thereof. In addition, the spacer tube 564
may have one or more apertures or holes 572 through a wall thereof
close to the proximal end of the spacer tube at its connection to
the main shaft 544. These holes 572 draw in air to the inside of
the spacer tube 564 thereby causing drag due to turbulence and
reducing the velocity of the aerosol as it exits the spacer tube.
The holes 572 may also slow the flow of particles through the
spacer tube by causing drag turbulence.
[0147] The spacer tube 564 also serves to protect the distal
orifices 556 and 560 of the nebulization catheter from coming into
contact with any part of the endotracheal tube, trachea, or other
airway passage thereby helping to maintain optimum tip operation
and to prevent damage to it during handling and insertion. In an
alternative embodiment, if only the tip protection feature is
desired, the spacer tube 564 of FIG. 33 may be provided without the
apertures 572. In such an alternative embodiment, the spacer tube
564 may be provided in a shorter length, e.g. 1 mm.
[0148] FIG. 34 shows another embodiment of a nebulization catheter
576 used with an endotracheal tube 580. The endotracheal tube 580
may be a conventional endotracheal tube. The nebulization catheter
576 provides for a nebulization plume with a reduced forward
velocity by imparting a spiral component to the liquid particle
flow. The nebulization catheter 576 has a distal tip 584 from which
a liquid medicine delivered from a distal liquid orifice is
nebulized by a flow of pressurized gas from a gas orifice located
adjacent to the liquid orifice. The nebulization catheter 576 is
positioned coaxially in the endotracheal tube 580. A centering
device 585 may be used to aid in centering the nebulization
catheter 576. Located along a portion of the nebulization catheter
576 proximal from the tip 584 is a second gas orifice 588. This
second gas orifice 588 may open to the same gas lumen that
communicates with the nebulizing gas orifice at the distal tip 584
or alternatively, the second gas orifice 588 may connect to
another, separate gas lumen. The second gas orifice 588 is oriented
to direct a pressurized flow of gas in a spiral, distal direction
along the distal end of the nebulization catheter 576. To
accomplish this, the second gas orifice 588 may be formed by an
inclined opening or with a deflection foil to direct the flow of
gas in the appropriate spiral direction. The spiral flow of
pressurized gas travels along the distal portion of the nebulizing
catheter 576 inside the endotracheal tube 580. The spiral flow of
gas entrains the aerosol generated from the distal end 584 of the
nebulizing catheter imparting a spiral flow component to the
aerosol plume. This has the effect of reducing the forward velocity
component of the liquid particle flow as it leaves the endotracheal
tube 580.
[0149] FIG. 35 shows an alternative method for using the
nebulization catheter 576 of FIG. 34. In FIG. 35, the nebulization
catheter 576 is shown extended distally of the distal end of the
endotracheal tube 580 so that the distal portion of the
nebulization catheter 576 including the second gas orifice 588 is
located in an airway passage. Taking into account the size of the
airway passage, the nebulization catheter 576 with the second gas
orifice 588 would operate similarly to the method shown in FIG. 34
and generate a spiral gas flow to reduce the forward velocity of
the aerosol plume.
[0150] Another embodiment of a nebulizing catheter 592 is shown in
FIGS. 36 and 37. This embodiment of the nebulizing catheter 592 can
be used with a separate endotracheal tube (not shown). The
nebulizing catheter 592 includes a main shaft 596 having a central
lumen 600 and one or more additional lumens 604 located around the
central lumen 600. In this embodiment, the central lumen 600 is
used for the flow of a pressurized gas and the additional
peripheral lumens 604 are used for the delivery of the liquid
medicine. The lumens 600 and 604 terminate distally in orifices 608
and 612, respectively. Located at a distal end of the nebulizing
catheter 592 and immediately adjacent the orifices 608 and 612 is a
diffuser 616. In one embodiment, the diffuser 616 is composed of a
generally disk-shaped body that is sized to deflect the flow of gas
from the orifice 608 of the central lumen 600 past the liquid
orifices 612 thereby nebulizing the liquid medicine. A small gap
(or venturi area) 620 between the diffuser 616 and the distal end
of the main shaft section 596 of the catheter 92 provides favorable
flow characteristics for generating the aerosol. The diffuser 616
may be connected to a retaining wire 624 that is located in the
central lumen 600. The retaining wire 624 may be used to secure the
diffuser 616 to the distal end of the nebulizing catheter 592.
Also, the retaining wire 624 may be used to pulse the generation of
aerosol by reciprocation of the diffuser. It is noted that the
aerosol produced by this embodiment has a substantially radial
velocity component and may have only a small forward velocity
component. In addition, a centering device, such as wings 625, may
be attached to the diffuser 616.
[0151] FIG. 38 shows an alternative embodiment of the diffuser 616.
In FIG. 38, the diffuser 616 is formed of a loop that has its ends
located in two apertures in the nebulization catheter shaft tip and
a middle portion directly in front of the distal gas orifice 608.
The loop may be formed of a metal or polymer wire or other
material. The loop could be formed by an extrusion method or
molded.
[0152] Referring to FIG. 39, there is an alternative embodiment of
the nebulization catheter system. A nebulization catheter 627 is
located in an endotracheal tube 628. The nebulization catheter 627
includes a coaxially arranged outer tube 629, a middle tube 630,
and an inner tube 631. Liquid delivered through a lumen of the
inner tube 631 is nebulized by pressurized gas delivered in the
annular region 632 between the inner tube 631 and the middle tube
630. In addition, pressurized gas is also delivered from a
secondary gas supply that communicates with the annular region 633
between the middle tube 630 and the outer tube 629. The secondary
gas supply may be used to help provide the desired plume shape and
velocity. For example, the secondary gas supply delivered from the
outer tube 629 can be used to provide a coaxial sheath of air that
helps minimize impaction of the nebulized aerosol on the walls of
the trachea or other airway passage. Alternatively, the secondary
air supply may be used to impart additional forward velocity to the
aerosol plume. With the embodiment of FIG. 39, the additional air
flow can be provided by the secondary gas supply via region
633.
[0153] In the embodiments discussed above, nebulization is provided
at a distal tip of a catheter by directing a pressurized gas from a
distal orifice across another distal orifice from which the liquid
medicine is delivered. As shown in several of the embodiments
above, one way to deliver the liquid from the distal orifice is via
a lumen that extends through the catheter to a proximal end. This
construction provides efficient operation for many types of
medication delivery. In many cases, the distal liquid medicine
orifice is subject to a negative pressure due to the pressurized
gas flow across it. This negative pressure may in many applications
be sufficient to draw the liquid out of the orifice in order to
nebulize it. If pulsing of the aerosol is desired, the pressure of
the gas lumen can be pulsed thereby resulting in pulsed generation
of the aerosol. By increasing the gas pressure, it may be possible
to also increase the aerosol output.
[0154] In other situations, it may be preferable to apply a
positive pressure to the liquid, such as at the proximal end of the
liquid lumen, in order to deliver liquid from the distal liquid
orifice, it is necessary. This positive pressure applied to the
liquid lumen may be the same as that applied to the gas lumen (e.g.
35-50 psi) or alternatively may be different (less than the gas
lumen). If it is desired to pulse the nebulization of the liquid,
this can be accomplished by applying pulses of pressure to the
column of liquid via the proximal end of the liquid lumen or
reservoir. It may also be preferred to synchronize the
pressurization of the gas in the gas lumen with the pressurization
of the liquid lumen. In addition to applying the positive pressure
to the liquid lumen in pulses to generate a pulsed aerosol from the
distal orifice, if it may be preferred in an alternative embodiment
to apply a small negative pressure immediately after each positive
pressure pulse in order to draw the liquid at the distal orifice
back into the liquid lumen to thereby avoid drooling. In a
preferred embodiment, the portion of the nebulization catheter in
which the liquid lumen is formed may be composed of a relatively
low compliance material to transmit pressure pulses to the distal
end with minimum attenuation.
[0155] A full length liquid lumen may have disadvantages in certain
situations. For example, pulsing of the liquid from the distal
orifice may not correspond to or follow closely with the
application of pressure to the proximal end due to attenuation of
the pressure pulse over the length of the catheter. In addition,
applying pressure to the proximal end of the liquid lumen in order
to transmit pressure to discharge the liquid from a distal orifice
requires that the lumen be filled with the liquid. In some
situations, this is more medicine than would be required by the
patient and might result in waste.
[0156] The embodiment in FIG. 40 addresses these concerns by
controlling the pressurization of the liquid as close as possible
to the distal liquid orifice, thereby reducing the effects of
catheter compliance and attenuation. In FIG. 40, a nebulization
catheter 652 has a main body 656 having a gas lumen 660 that
extends from a proximal end (not shown) to a distal gas orifice
664. The main body 656 also includes a distal liquid medicine
reservoir 668. In the embodiment shown in FIG. 40, the liquid
reservoir 668 is located in a distal portion of the main shaft 656
of the catheter 652. The liquid reservoir 668 is preferably close
to the distal tip of the nebulizing catheter 652. The liquid
reservoir 668 is filled with the medicine to be delivered. If the
amount of medicine is small in volume, the liquid reservoir may
also be correspondingly small. This embodiment is especially
suitable for the delivery of small volumes of medicine such as 0.1
to 0.5 ml, e.g. single use. The reservoir 668 may be pre-filled
during the manufacturing stage of the catheter. The reservoir 668
may be formed by plugging a lumen of the catheter at a distal
location. Alternatively, the liquid reservoir 668 may also extend
back to the proximal end of the catheter, thereby forming a liquid
lumen, and communicate with a proximal port as described with
respect to the other embodiments discussed herein. This may be
required if the lumen is made of a non-compliant material. In yet
another alternative embodiment, the liquid reservoir may be formed
in a balloon located externally of the catheter shaft 656.
[0157] A filter 672 and plug 676 occupy positions in the distal end
of the liquid lumen/reservoir 668. A distal tubular extension 680
extends from the plug 676 and communicates with the liquid
lumen/reservoir 668. The tubular extension 680 has a distal orifice
684 aligned with the distal gas orifice 664 so that a pressurized
gas exiting the gas orifice 664 nebulizes the liquid exiting the
liquid orifice 684. The distal liquid orifice may have a sealable
cap or wax-like covering associated therewith that can be opened
when the nebulization catheter is put into use. In a distal section
of the main shaft 656 of the catheter 652, the gas lumen 660 and
the liquid lumen 668 are separated by a flexible, distendable wall
or membrane 688. In the embodiment of FIG. 40, pulsing of the
aerosol is accomplished by pulsing of the gas pressure in the gas
lumen 660. When the pressure in the gas lumen 660 is high, it
causes the flexible wall 688 between the gas and liquids lumens 660
and 668 to distend into the liquid lumen 668. This is represented
by the dashed line in FIG. 40. When this occurs, the pressure from
the gas lumen 660 is transmitted to the liquid lumen 668 and liquid
medicine is forced out the distal liquid orifice 684. When the
pressure applied to the gas lumen 660 is low, the distendable wall
688 recovers its original position. It is noted that when the
distendable wall 680 recovers its original position, it may cause a
negative pressure at the distal liquid orifice 684 which may cause
the liquid to withdraw slightly into the tubular extension 680
thereby reducing the occurrence of liquid drooling at the tip. In
addition, it is noted that the delivery of liquid from the distal
liquid orifice 680 may not occur immediately upon application of a
high gas pressure to the gas orifice since it will take some time
for the bladder 688 to distend. This means that gas will be flowing
steadily at a high pressure from the distal gas orifice when the
liquid begins to flow from the distal liquid orifice. This also may
provide cleaner aerosol delivery and reduce the occurrence of
drooling of liquid at the tip.
[0158] An alternative embodiment of the nebulization catheter 652
shown in FIG. 40 may be made using a flexible, but inelastic
material for the bladder wall 688. If the bladder wall 688 were
flexible, but inelastic, the pressurized gas passing past the
liquid orifice 684 would create a negative pressure (venturi
effect) thereby drawing out the liquid and nebulizing it. A
continuous or preferably an intermittent gas supply to the venturi
area would provide this negative pressure. The bladder wall may be
provided with a vent to facilitate discharge.
[0159] In order to manufacture a nebulization catheter with
compliant and non-compliant regions, as described above, the
catheter may be co-extruded using different compounds or polymers
to optimize the physical properties of the different wall sections.
It may be preferred to use high energy radiation to crosslink the
polymer material in the formation of the bladder wall.
V. Alignment of the Aerosol Plume
[0160] The embodiments described above are directed to developing
an optimum nebulization plume. It is further recognized that
another factor that contributes to the efficiency of the
nebulization is the position of the nebulization catheter relative
to the anatomical environment. For example, even if the
nebulization catheter being used develops an optimal plume, the
delivery efficiency of the catheter may be significantly impaired
if the plume is directed into the wall of the endotracheal tube,
the trachea or other airway passage. Accordingly, proper location,
orientation, and alignment of the nebulization catheter in the
anatomy can be an important factor contributing the delivery of
medicine via a nebulization catheter. In general, it is preferable
to align the catheter coaxially in the airway passage in which it
is located.
[0161] It is also noted that an endotracheal tube, if present, can
adversely effect delivery of aerosol from a separate nebulization
catheter. For example, an endotracheal tube has an inner diameter
that is smaller than the diameter of the trachea so that if the
nebulization takes place inside the endotracheal tube, a portion of
the aerosol may impact the inner wall of the endotracheal tube and
thereby be wasted. Most conventional endotracheal tubes have a
curved distal end that is relatively rigid so that when it is in
place in the trachea of a patient, the distal end of the
endotracheal tube is oriented off center. This can affect the
orientation of a nebulization catheter located in the endotracheal
tube causing it direct its aerosol into the trachea wall even if
the nebulization catheter is positioned so that its distal end is
located distally of the endotracheal tube. In general, it is
desirable to allow the aerosol particles to avoid impaction for
several centimeters after the aerosol is produced so that the
aerosol particles can lose their velocity and become entrained in
the inspiratory airflow.
[0162] The embodiment of the invention in FIG. 41 is directed at
providing improved alignment of a nebulization catheter in a
patient's trachea. In FIG. 41, an endotracheal tube 700 is
positioned in a trachea 704 of a patient. The endotracheal tube 700
is of a type that has an inflatable cuff 708 located around a
distal exterior side to facilitate positioning and alignment of the
endotracheal tube 700 in the trachea 696. Extending through and out
of a distal end of the endotracheal tube 700 is a nebulization
catheter 712. The nebulization catheter 712 may be similar to any
of the embodiments of the nebulization catheter described above.
Located around a distal portion 716 of the nebulization catheter
712 is a spring centering apparatus 720. The spring centering
apparatus 720 includes a retainer ring 724 fixed to the shaft of
the nebulization catheter 712 and a plurality of arms 728 connected
to the ring 724. In one embodiment, there are three arms 726. The
arms 726 are flexible and resilient. The arms 726 may be made of a
spring tempered metal or a suitable plastic. Located at the end of
each of the arms 726 opposite its connection to the ring 724 is a
ball 727. The spring centering apparatus 720 is deployed by first
positioning the nebulizing catheter 712 including the spring
centering apparatus in the lumen 728 of the endotracheal tube 700.
The arms 726 are formed so that they assume a size larger than the
diameter of the trachea or airway passage. Accordingly, when the
centering device is positioned in the endotracheal tube 700, the
arms are resiliently deformed into a compressed configuration with
the balls 727 close to the shaft of the nebulizing catheter 712. To
deploy the centering device, the nebulizing catheter 712 is
advanced out the distal end of the endotracheal tube 700. When the
balls 727 are advanced out the endotracheal tube 700, they spring
out to an expanded size and engage the walls of the trachea or
other airway passage. The balls 727 provide a relatively smooth
surface to limit irritation or injury to the trachea walls or other
airway passage. With the arms expanded, the nebulizing catheter is
centered in the trachea or other airway passage so that a plume
discharged from a distal end of the nebulizing catheter has minimal
contact with the walls of the trachea or other airway passage. When
it is necessary to remove the nebulizing catheter 712, it can be
withdrawn in a proximal direction back into the endotracheal tube
700. In a preferred embodiment, the arms are formed of a thin
resilient wire or polymer, preferably less than approximately 0.015
inches in diameter. The arms and/or the balls may be made of, or
coated with, a radiopaque material. It is an advantage of the
embodiment of the centering device shown in FIG. 41 that it is
located somewhat in advance of the distal end of the nebulization
catheter. This positions the arms 726 of the centering device in
the portion of the trachea or other airway passage into which the
aerosol will be initially flowing. Thus, the centering device
orients the distal tip of the nebulization catheter relative to the
portion of the trachea or other airway passage beyond the distal
tip thereby helping to reduce impaction along this portion.
[0163] FIG. 42 shows an alternative embodiment of the nebulization
catheter. A nebulization catheter 729 is used with an endotracheal
tube as described above. The nebulization catheter 729 includes a
centering device 730. The centering device 730 includes a plurality
of arms 731 that are formed to resiliently extend outward from the
axis of the catheter shaft to engage the wall of the patient's
trachea or airway passage or the interior of an endotracheal tube
depending upon the desired location of the distal end of the
nebulization catheter. At the ends of each of the arms 731 are
balls 732. The proximal ends of the arms 731 are formed of wires
733 that extend through lumens 734 in the shaft of the catheter
729. Each of the lumens 734 has a distal opening 735 from which an
arm can extend. The distal openings are approximately 0.10-1 cm
from the distal end of the catheter shaft. The proximal ends of the
wires 733 exit the lumens 734 of the nebulization catheter via
openings 736 that are close to the proximal end of the catheter in
a portion of the catheter that would normally be outside the
patient's body during use. Thus, the proximal ends of the wires 733
are accessible to the physician during use. By pulling and pushing
on the proximal ends of the wires 733, the portion of the arms 731
that extend from the openings 735 can be adjusted. Thus, the arms
731 can be adjusted from a fully retracted to a fully advanced
position by pulling or pushing on the proximal ends of the wires
733. In addition, since the proximal ends can of the wires 733 be
adjusted in any intermediate position between the fully retracted
and fully advanced positions, the physician can adjust the size of
the centering device 730 to any appropriate size, as desired.
Because the wires 733 should assume a desired shape when advanced
out of the lumens in which they are contained during positioning,
it is preferable that they be formed of a material that has shape
memory properties so that the desired expanded shape can be
imparted to the wires during manufacture. In one embodiment, the
wires may be formed of nitinol.
[0164] In one preferred embodiment, a second centering device 737
is also provided. The second centering device 737 is located on the
shaft of the nebulization catheter 729 proximally from the first
centering device 730. The second centering device 737 may be formed
of resilient wings formed of a material such as plastic or metal
that extend radially outward from the shaft. The second (or
proximal) centering device 737 helps keep the distal portion of the
catheter 729 in alignment.
[0165] FIG. 43 shows another alternative embodiment of the present
invention. A nebulizing catheter 738 is shown which may be similar
to the catheter 20 of FIG. 1. The nebulizing catheter 738 includes
a centering device 739. The centering device 739 includes a wire
loop 740 located at a distal end of the catheter. One end 741 of
the loop 740 connects to the distal end of the nebulizing catheter
shaft. The other end 742 of the wire loop 740 enters an opening 743
in the shaft that communicates with a lumen 744 that extends to a
proximal end of the catheter 738. A proximal end 745 of the wire
exits the lumen 744 via an opening 746 in a proximal portion of the
nebulizing catheter which is normally outside the patient's body
during use. The size of the wire loop 740 can be adjusted by
advancing or withdrawing the proximal end 745 of the wire. In this
embodiment, it can be determined that the centering device is fully
retracted when the wire 745 cannot be withdrawn any further. The
position of the distal end of the nebulization catheter can also be
determined by the resistance to further retraction caused when the
loops or arms engage the distal end of the endotracheal tube. When
in an expanded size, the wire loop 740 engages the walls of the
trachea or airway passage or the interior of the endotracheal tube
depending upon where the distal end of the nebulizing catheter is
positioned. The size of the wire loop 740 can be adjusted from a
fully reduced size to a fully expanded size as well as intermediate
sizes. With the embodiment of FIG. 43, the size of the loop can be
adjusted to different size airway passages in different patients or
alternatively the size of the loops can be adjusted to different
airway passages in the same patient if the physician desires
relocating the nebulizing catheter to different locations in a
patient's respiratory tract. In a one preferred embodiment, more
than one wire loop may be provided at the distal end of the
nebulizing catheter. It is noted that the wire loop 740 of this
embodiment may also be used in for facilitating positioning over a
guide wire in a manner similar to loop 106 shown in FIG. 9.
[0166] FIGS. 44 and 45 show another alternative embodiment of the
present invention. A nebulizing catheter 747 has a shaft portion
748 and a wire loop 749 extending from a distal end of the shaft
748. In this embodiment, the wire loop 749 is connected at each end
750 and 751 to the distal end of the catheter shaft 748. A
retractable sheath 752 is positioned over the nebulizing catheter
shaft 748. The sheath 752 can be advanced and withdrawn relative to
the catheter shaft 748. When it is desired to maneuver the
nebulizing catheter into a desired position in the respiratory
tract of a patient, the sheath 752 is advanced over the loop 749 to
maintain a low profile, as shown in FIG. 45. When the distal end of
the nebulizing catheter is suitably positioned, the sheath 752 is
then retracted, as shown in FIG. 44, allowing the loop 749 to
expand to its expanded size to center and align the distal end of
the nebulizing catheter in the respiratory tract. In one
embodiment, the loop 749 is formed of a superelastic material such
as nitinol.
[0167] As noted above, proper positioning and alignment of the
nebulization catheter can be an important factor affecting drug
delivery efficiency. In general, it is preferable to position the
tip of the nebulizing catheter as closely to the central region of
the trachea (or other respiratory passage, such as the bronchi) as
possible. It is further noted that even if the catheter can be
centered relative to the trachea, if a section proximal to a
centering device is misaligned, it can affect the directional
orientation of the tip. This situation is represented in FIG. 46 in
which a nebulizing catheter 753 is centered, but the tip is not
properly aimed to provide an optimum plume. This potential problem
can be overcome by using an embodiment of the invention shown in
FIG. 47. In FIG. 47, a nebulizing catheter 754 is located in a
trachea 755 of a patient. The nebulizing catheter 754 extends out
the end of an endotracheal tube 756. A first centering apparatus
757 is located on a main shaft 760 of the nebulizing catheter 754
close to the distal end 764. The first centering device 757 may be
similar to the centering devices shown in FIGS. 41-45. A second
centering device 768 is located axially along the nebulizing
catheter shaft 760 proximally from the first centering device 757.
The second centering device 768 may be the same as the first
centering device 757. As shown in FIG. 47, the two centering
devices 757 and 768 not only serve to position the nebulization
catheter 7754 centrally in the trachea, but also serve to align the
nebulizing catheter tip to expel the plume along a central axis of
the trachea.
[0168] The proximal centering device 768 may be substituted by
another type of centering device or may employ the endotracheal
tube 756 for this purpose, as shown in FIG. 48. If the endotracheal
tube is used to assist in centering the nebulization catheter, it
may incorporate a distal, elongated occlusion cuff 772 or balloon
to coaxially align it accurately in the trachea. Most conventional
endotracheal tubes are provided with a curvature to facilitate
positioning the trachea of a patient. In addition, most
conventional endotracheal tubes are relatively stiff. These factors
may result in the misalignment of the distal end of the
endotracheal tube relative to a patient's trachea as illustrated in
FIGS. 46 and 47. In order to use the endotracheal tube for
centering of the nebulization catheter, it is preferable to make
the tip of the endotracheal tube straighter and/or more flexible
than in conventional endotracheal tubes to ensure proper
concentricity with the occlusion balloon and the trachea. An
endotracheal tube with a straighter and more flexible tip is shown
in FIG. 48. In addition, the endotracheal tube may be provided with
a centering or aiming device 776 for aligning the nebulization
catheter 754. In the embodiment of FIG. 48, the aiming device 776
is formed by a plurality of flexible or resilient wings the extend
from the wall of the endotracheal tube 756 toward an axially
central position.
[0169] Appropriate centering and aiming of the nebulization
catheter can be affected by anatomical factors. It is noted that in
some circumstances, it is preferable to position the distal tip of
the nebulization catheter into either bronchus of the lungs or even
into separate bronchia. Positioning of the nebulizing tip closer to
the alveoli may enhance drug delivery efficiency. In a situation in
which it is desired to place the nebulizer tip in both bronchi of
the lungs, a nebulizing catheter 780 with dual tips can be
employed, as shown in FIG. 49. When using a dual tip catheter such
as shown in FIG. 49, centering and aiming can be important
considerations because of the narrower air passages in each of the
bronchi. To provide for centering and aiming of a dual tip
nebulizing catheter, each of the tips 784 and 788 may be provided
with its own centering apparatus, such as 792 and 796. These
centering devices may be similar to the centering devices described
above. Alternatively, the centering devices 792 and 796 may be
formed of arms or struts, made of a flexible or resilient material,
that bow out from the shafts of each of the tips 784 and 788, as
shown. These struts may be formed with a shorter length in order to
fit into smaller airway passages or alternatively they may be made
to provide a range of deployment sizes to accommodate different
airway passages.
[0170] As an alternative to providing a nebulizing catheter with
dual tips 784 and 788 as shown in FIG. 49, if delivery of
aerosolized medicine into separate branches of the lungs is
desired, it may be preferred to use a nebulizing catheter with a
single nozzle tip that has multiple orifices or jets aimed toward
the desired branches.
[0171] With respect to all the centering devices described above,
it is noted that some aerosol may impact the wires or loops that
form the centering devices and accordingly, the centering devices
are preferably constructed of wires or other materials having a
small diameter or cross section to minimize losses due to such
impaction. Moreover, the overall improved efficiency due to the
reduction in aerosol impaction on the walls of the trachea or other
airway passage is expected to more than compensate for any losses
due to impaction on the centering device.
[0172] Another alternative means for centering the distal end of a
nebulization catheter in the air passage is to use part of the
pressurized gas for a pneumatic centering device. Air jets
generated from two or more outward directed orifices spaced evenly
around the outer circumference of the nebulizing catheter near the
tip can be used to center the catheter in the airway. This
alternative may help avoid irritation and provide additional
advantages compared to physical centering devices.
[0173] Another alternative way to help center the nebulizing
catheter in the patient's airway passage is to use a balloon or
wire centering device placed near the nebulizing catheter tip. The
balloon or wire centering device can be temporarily inflated to
double check the placement of the nebulizing catheter tip in
relation to the endotracheal tube tip. To use this feature the
nebulizing catheter is advanced beyond the endotracheal tube tip
using markings on the proximal shaft to judge the distance. The
centering device or balloon would then be expanded to a diameter
larger than the endotracheal tube and the catheter retracted until
the centering device or balloon could be felt engaging with the
endotracheal tube tip or until the endotracheal airflow was
obstructed.
VI. Operation and Flow Control
[0174] As mentioned above, the driving gas used to pressurize the
gas lumen may be pure (e.g. 100%) oxygen at a pressure of 35-50
psi. Other gases and pressures may be used with suitable
adjustments to provide for the desired particle size. The
pressurized gas also may be humidified by a bubbler or other
suitable means and warmed, if necessary.
[0175] Regarding the liquid lumen, one way to deliver the liquid
drug through the nebulizing catheter is by a manually operated
syringe. To delivery a liquid drug in this manner, a syringe
containing the liquid medicine to be nebulized is connected to the
liquid port on the manifold connected to a proximal end of the
nebulizing catheter. Then, the liquid is injected while the
pressuring gas is being supplied to the nebulizing catheter via the
gas inlet port on the nebulizing catheter manifold. Using a
manually operated syringe is reliable, easy to use, and may be
preferred when it is desired to deliver only a small amount of
medication.
[0176] In a preferred embodiment, the liquid drug is delivered to
the nebulizing catheter from a pressurized source. A pressurized
source for the liquid medicine can provide for a generally higher
and more uniform pressure. A high pressure assists in clearing any
blockages that may occlude the liquid lumen. Pressurization of the
liquid lumen also can ensure that all the liquid drug is evacuated
from the catheter tip. In addition, use of a liquid pressurization
source can provide for drug delivery for a longer period of time or
a drug delivery that is timed or pulsed to coincide with operation
of a ventilator, if used. In a preferred embodiment, the same
pressure source (at 50 psi) that is used to provide the gas
pressurization can also be used to provide for pressurization of
the liquid. Some ventilators have an auxiliary port that are used
for externally located nebulizers. The pressure flow from this
auxiliary port may be used as a pressure source to drive the liquid
and gas supplies of the embodiments of the nebulizing catheter
considered herein. Alternatively, a sensor located in the flow from
this auxiliary port may be used to trigger another control device
that operates the pressurized liquid and gas supplies.
[0177] In a preferred embodiment, the generation of the aerosol can
be synchronized with the inhalation of the patient. In one
embodiment, this can be accomplished with a manually operable
control gas valve on the gas pressure line to the liquid input
port. This may be suitable when the medicine can be delivered in a
short period of time, e.g. a few respiratory cycles. Alternatively,
when it is preferred to deliver the medicine for an extended period
of time, it may be preferred to employ a system that can
automatically deliver medicine via the nebulizer from a source of
liquid medicine. In such a system, the gas and/or liquid flow are
triggered by the patient's respiratory cycle with the use of an
electronic pressure sensor and relay actuator.
[0178] An important factor relating to effective delivery of
medication via a nebulizing catheter is the flow control system for
pressurizing and supplying the gas and liquid to the proximal end
of the nebulization catheter. In many circumstances, it is
envisioned that medication will be delivered to the patient via a
nebulization catheter that is in place in the patient over an
extended period of time, such as several hours or days. In such
circumstances, it would be preferred to use a system that
automatically delivers the proper dosage of medication from a
supply of the medicine to the patient at the proper rate, and
further that can operate automatically and unattended. Further, it
would be preferred to provide a means to detect when the supply is
running low so that either the nebulization catheter can be
disconnected or a new supply provided. FIGS. 50 and 51 show several
embodiments of a reservoir and pressurization system for use with a
nebulizing catheter.
[0179] Referring to FIG. 50, a reservoir and pressurization
assembly 800 is connected to a proximal end of a nebulization
catheter. The nebulization catheter may be similar to any of the
embodiments described above. The assembly 800 has a gas inlet port
804 that can connect to an external pressurized gas supply. The
external pressurized gas supply may be the main gas supply of the
hospital or may be provided by another unit. The external gas
supply may provide oxygen at 50 psi. The gas inlet port 804
communicates with an airflow passageway 808 defined by and
extending through the assembly 800. The assembly 800 includes a gas
output port 812 that communicates with the fluid flow passageway
808 and which connects to a gas inlet port of the nebulization
catheter (not shown). The gas output port 812 is located
immediately downstream of the gas inlet port 804. Located in the
fluid flow passageway 808 downstream of the gas outlet port 812 is
a filter 816. The filter 816 is preferably a hydrophobic filter
that allows the passage of gas but which would prevent the backflow
of any liquid. Located downstream of the filter 816 in the fluid
flow passageway 808 is an injection port and reservoir 820. This
port 820 communicates with a supply of the liquid fluid medication
to be supplied to the nebulizing catheter. Located next in the
fluid flow passageway 808 is a capillary tube drug reservoir 824.
The capillary tube reservoir 824 is comprised of a length of
plastic tubing adapted to hold a supply of the liquid medication to
be delivered. In the embodiment shown, the capillary tube reservoir
consists of a helical coil of transparent tubing. Located
downstream of the capillary tubing reservoir 824 is a liquid outlet
828 that connects to a liquid inlet port of the nebulization
catheter (not shown). With the embodiment shown in FIG. 50, the
transparent capillary tubing 824 provides a convenient and reliable
way to ascertain the supply of medication to the nebulizing
catheter. The capillary tubing because of its length is capable of
containing a suitable supply of the medication. When the attending
medical personnel observe that the medication is about to run out,
a new supply can be readily provided. The clear capillary tube
allows easy visualization of the drug flow by watching the gas-drug
meniscus travel down the tube. Instead of relying on direct
observation by medical personnel, the capillary tubing may be used
with an automatic detection device, e.g. a photocell, that provides
an alarm to the medical personnel upon detection that the
medication is running out in the capillary tubing or that the
meniscus has ceased moving due to a blockage. A blockage may also
be detected by detection of an increase in pressure.
[0180] FIGS. 51 and 52 show another embodiment of a fluid reservoir
and pressurization assembly 832. This embodiment includes a gas
inlet 836, a fluid flow passageway 840, a liquid medicine supply
vent 844, a filter 848, a capillary channel section 852, and an
outlet port 856. In this embodiment, the filter 848 is located
downstream of the filling vent 844. The filter 848 allows the
pressurized gas to push the liquid drug during use but prevents the
liquid drug from backing up to the vent during filling. In this
embodiment, a second injection port 860 is provided downstream of
the capillary section 852 and a second filter 864 is located
downstream of the second injection port 860. The second filter 864
is preferably a filter having approximately a 20 .mu.m retention.
Also, in this embodiment, the capillary section 852 may be composed
of a planar section 865. The planar section 865 may be a piece of
plastic having a winding channel molded, routed or otherwise formed
therein. The planar section 868 is preferably colored to provide
suitable contrast with the liquid solution flowing therethrough. A
transparent flat plastic cover is positioned over the winding
channel of the planar section 865 to form the closed channel of the
capillary section. The fluid channel in the capillary section
preferably has an I.D. of approximately 2 mm. The second inlet port
864 provides an additional means to add medication to the
nebulizing catheter liquid flow. When the capillary channel in the
section 852 has been filled, the gas is used to pressurize the tube
and force the fluid to the catheter tip. The second filter 864 acts
as a restrictive orifice to precisely meter the flow to the
nebulizing catheter. The clear capillary channel allows easy
visualization of the drug flow by watching the gas-drug meniscus
travel down the tube. The narrow tube makes the flow appear to move
quickly even at slow delivery rates. Thus, any flow interruption
can be easily observed. The capillary tubing section also ensures
that almost 100% of the drug is delivered to the catheter tip since
there is no dead space in the line except at the injection port
860.
[0181] During ventilation of a patient with an endotracheal tube,
especially when intubation that takes place for a long period of
time, it is considered desirable to humidify the air being
delivered. When a nebulization catheter is used for delivery of
medicine, either in conjunction with an endotracheal tube or even
without an endotracheal tube, it is possible to utilize the
nebulization catheter for providing humidification in addition to
medicine delivery. An embodiment of a flow delivery system for a
nebulizing catheter incorporating humidification is shown in FIG.
53. A suitably large reservoir 866 holds sterile water or saline.
The reservoir 866 is connected to the liquid supply lumen 867 of a
nebulization catheter 868. Solution is drawn into the nebulization
catheter 868 from the reservoir 866 by negative pressure at the
catheter tip, gravity, a pump in the solution supply line distal of
the reservoir, or by pressurizing the reservoir by a suitable
means.
[0182] Medicine may be added to the humidification water in at the
following ways. In a first alternative, the medicine is added to
the isotonic saline in the solution reservoir 866 thereby providing
for high dilution and slow, continuous delivery of the medicine
along with the water. In second alternative, the medicine is
introduced into the solution supply line 867 via an injection port
869 between the reservoir 866 and the liquid lumen of the catheter
868. The medicine may be delivered to the injection port of the
solution supply line from a solution reservoir system such as
system 800 of FIG. 50. Using this latter alternative, a more
concentrated dose of the medicine can be delivered at the specific
time preferred by the physician. It may also be preferable to
include a molecular sieve, check valve or air trap 870 between the
reservoir 866 and the injection port to the to ensure that the
medicine cannot flow or diffuse backwards into the reservoir
866.
[0183] When delivering medicine to the lungs or when delivering
water for humidification, it may be desired to heat the liquid
prior to delivery. This may especially be appropriate since
expanding gases which are associated with the nebulization of
liquids may remove heat from the body. In order to address this
concern, a heating element 871 may be associated with the liquid
supply line 867 to the nebulizing catheter 868. This heating
element 871 may include an electric coil wound around the supply
line 867 or may use a heated water flow in a tubing wound around
the supply line 867. The heating element 871 may be used in
embodiments that provide for humidification as well as those that
do not. Alternatively, the heating element 871 may be associated
with the gas supply line or with the liquid reservoir 866,
[0184] It is generally considered preferable to operate the
nebulizing catheter so as to generate an aerosol that is carried by
a patient's inhalation to the lungs. This requires a pulsing of the
aerosol generation so that it is timed to coincide with the
inhalation of the patient. If the patient is intubated, the timing
of the nebulization can be synchronized with the operation of the
ventilator. It is recognized that it may be preferable to begin the
nebulization slightly in advance of, at, or slightly after, the
beginning of the inhalation period in order to account for the
distance between the nebulization tip and the alveoli. Also, it may
be preferable to stop the nebulization slightly before the end of
the inhalation period in order to avoid wasting aerosol after the
inhalation flow has stopped.
[0185] This continuous pulsing of the aerosol can be accomplished
by a system 872 as shown in FIGS. 54 and 55. FIGS. 54 and 55 show a
portion of the flow control system for a nebulizing catheter. A
flow line 876 has an inlet 880 and an outlet 884. The flow line 876
may be formed of a soft (e.g. compliant) tube. The inlet 880
connects to the source of liquid medicine and in particular may
attach to the liquid outlet (828 or 856) of the liquid reservoirs
shown in FIGS. 50-52. The flow line outlet 884 in FIGS. 54 and 55
connects to the liquid inlet port on the manifold of the nebulizing
catheter, such as port 32 in FIGS. 1 and 2. Located around a
portion of the flow line 876 is an actuator piston 888. The
actuator piston 888 includes a solenoid pinch valve 892 that can
impinge upon the portion of the liquid flow line 876 extending
therethrough thereby pinching it off. The actuator piston 888 is
connected to and operated by a controller that receives input from
the ventilator (such as from the auxiliary port used for an
external nebulizer) so that the actuator piston 888 is operated to
open and close the flow line synchronous with the inhalation and
exhalation phases of the ventilator. Instead of a solenoid piston,
a metering valve or reversible syringe pump may be used.
[0186] In a preferred embodiment, the flow control system 872 uses
a dual solenoid arrangement to provide a draw-back feature. Pulsing
of the liquid flow by actuation of the actuator piston 888 may
result in some liquid being left at the distal nebulizer liquid
orifice when the pressure is turned off. This may result in small
amounts of liquid drooling from the distal liquid orifice tip since
the liquid is not being expelled under controlled pressure
conditions. In order to limit the occurrence of such drooling, a
draw back feature is provided in the flow control system. The draw
back feature is provided by a second solenoid 896 which is
associated with a bladder 900 that communicates with the flow line
876. The bladder 900 communicates with the flow control line 876
downstream of the actuator piston 888. A small amount of fluid
(liquid/air) occupies the bladder 900. The bladder is composed of
an elastic material that is formed with a tendency to recover to an
expanded size. When the actuator piston 888 opens to allow the flow
of fluid to the distal end of the nebulizing catheter, the second
solenoid 896 moves to a closed position thereby compressing the
bladder 900 and squeezing fluid out of it into the fluid flow line
876, as shown in FIG. 54. During the exhalation stage of the
ventilation cycle, the actuator piston 888 closes to shut off the
flow of fluid to the distal end of the nebulizing catheter. When
the actuator piston 888 closes, the second solenoid 896 opens, as
shown in FIG. 55. This allows the bladder 900 to resiliently
recover to its expanded size, and when it does, it draws fluid into
it from the fluid flow line 876. Because the fluid flow line 876 is
closed proximally at the actuator piston 888, when the bladder
draws fluid into it from the fluid flow line 876, it draws fluid
from the distal end of the fluid flow line that connects to the
nebulizing catheter liquid lumen. This causes the entire column of
liquid in the liquid lumen of the nebulizing catheter to move
slightly in a reverse direction (i.e. proximally) thereby moving
the liquid away from the distal orifice. In this manner, the flow
control system of FIGS. 54 and 55 allows the draw back of liquid in
the flow line in a reverse direction during the exhalation phase of
the ventilator when the liquid flow line is shut off.
VII. Selective Nebulization Therapy Delivery
[0187] When delivering medication with a nebulizing catheter, it
may be desirable to deliver the medication to only one of the
bronchi of the lungs and not the other or to only certain bronchia
and not others. A reason for this type of selective therapy may be
that only one area of the lungs requires medication. An embodiment
of the invention shown in FIG. 56 facilitates selective delivery of
a medication via a nebulizing catheter to only one bronchus. In
FIG. 56, an endotracheal tube 904 is positioned in a trachea 908 of
a patient. A nebulizing catheter 912 is positioned in the
endotracheal tube 904. This nebulizing catheter 904 may be similar
to the embodiments described above. This nebulizing catheter 904
may even be of the type that is non-removably incorporated into the
endotracheal tube. A second catheter 916 extends distally of the
endotracheal tube 904. The second catheter 916 may be positioned in
the ventilation lumen 920 of the endotracheal tube 904. The second
catheter 916 includes a lumen through which a low flow pressurized
gas can be conveyed. A proximal end of the second catheter 916
extends out of the proximal end of the endotracheal tube 904
through a suitable fitting, such as the fitting described in U.S.
Pat. No. 5,078,131 (Foley). A suitable source of pressurized gas is
attached to a proximal end of the second catheter 916. This gas
source may be the same gas source used for the pressurized gas
lumen of the nebulization catheter 912. A distal end 928 of the
second catheter 916 is positioned in the bronchus 932 other than
the bronchus to which it is desired to deliver nebulized
medication. Pressurized gas is delivered through the second
catheter 916 out an orifice 936 in the distal end thereof. The
delivery of pressurized gas out the distal end 936 of the second
catheter 916 causes the pressure level in the bronchus 932 to be
slightly greater than in the other bronchus. Accordingly, when the
nebulizing catheter 912 generates an aerosol of liquid medicine, it
will tend to flow with the inhalation stream from the endotracheal
tube 904 to the bronchus other than the one with the second
catheter 916. In this manner, one of the bronchi of the lungs, or
even selected bronchia, can be selectively medicated using a single
nebulization catheter positioned in the endotracheal tube.
VIII. Timing of Nebulization
[0188] As mentioned before, in order to deliver the nebulized
medicine to the lungs, it is preferred that the medicine is carried
by the inhalation of the patient. A number of factors affect the
efficiency of the medicine delivered this way. The following
embodiments are directed to improving drug delivery efficiency
taking into account some of these factors.
[0189] If the patient is intubated, it may be possible to
synchronize the timing of the nebulization pulse with the patient's
ventilation. In one embodiment, this may be accomplished by
providing an interface between the ventilator and the nebulizer. In
some circumstances it may be preferred to provide other means for
triggering the nebulization. For example, the ventilator being used
may not provide a suitable interface. Also, the ventilator may not
provide sufficiently accurate information concerning the patient's
respiration to enable the nebulization catheter to operate with
highest efficiency. In such situations, it may be preferred to
utilize one or more separate sensors to obtain information that can
be used to trigger and operate the nebulization catheter.
[0190] Referring to FIG. 57, there is a nebulizing catheter 944
positioned in an endotracheal tube 948 located in the trachea 952
of a patient. A proximal end of the endotracheal tube 948 is
connected to a ventilator 956. In order to obtain physiological
information concerning the patient's respiration for use in timing
the generation of nebulization pulses by the nebulization catheter
944, one or more sensors may be used. For example, a first sensor
960 may be located on a distal end of the endotracheal tube 948. In
addition, a sensor 964 may be positioned on the nebulization
catheter 944. Another sensor 968 may be positioned on a separate
device, such as a separate catheter 972 which is located further
distally in the respiratory system. In addition, a sensor 976 may
be positioned in the ventilator circuit of the ventilator 956 or in
a ventilator auxiliary port, if available, or elsewhere on the
patient. These sensors 960, 964, 968, and 976 may be types of
sensors that measure pressure, flow or a physiological parameter of
the patient, such as muscle contraction, electophysiological
activity, etc. In alternative embodiments, one or more of these
sensors may be used.
[0191] FIGS. 58 and 59 show alternative embodiments of nebulization
catheters that incorporate sensors. In FIG. 58, a nebulization
catheter 980 is shown. This nebulization catheter 980 may be
similar to the nebulization catheter in FIG. 11. In FIG. 58, a main
shaft 984 includes a plurality of lumens with a centrally located
lumen 988 used to deliver a liquid medicine and a plurality of
lumens 992 located peripherally around it used to deliver a
pressurized gas. One of the peripheral lumens 996 is not used for
pressurized gas delivery, but instead is used for sensing purposes.
This may be accomplished by forming an aperture 1000 through a wall
of the main shaft 984. The aperture communicates with the sensing
lumen 996. The aperture 1000 may be open or may be covered with a
flexible diaphragm that permits transmission of pressure across it.
A pressure sensing device may be located at a proximal end of the
nebulizing catheter. The pressure at the distal end of the
nebulizing catheter can be sensed by the proximally located sensing
device via the sensing lumen 996. This could rely on pneumatic
sensing of the distal air pressure. Because of the effect of the
distal gas pressurization orifice, pressure sensing through the
sensing lumen 996 may be used for purposes of gross overpressure
for safety purposes. Alternatively, the pressure sensing lumen 996
may be used during periods of time when a pressurizing gas is not
being delivered to sense the patient's physiological airway
pressure.
[0192] FIG. 59 shows another embodiment of a pressure sensing
nebulization catheter. This embodiment is similar to the embodiment
of FIG. 58 except that a sensor 1004 is located at a distal end of
the catheter 980, specifically in the aperture 1000. In this
embodiment, the sensor 1004 is a pressure transducer. Wire leads
1008 extend proximally from the sensor 1004 via the lumen 996.
Instead of measuring pressure, the sensor 1004 could measure the
flow at the distal end of the catheter. This may be accomplished by
piezoelectric, optical, Hall effect, or other types of sensor
technologies. The sensor may also be of a fiber optic type.
[0193] Although the embodiments of FIGS. 58 and 59 show sensing
apparatuses associated with a nebulization catheter, these same
types of sensors could also be used in the endotracheal tube 948,
the separate catheter 972, or the ventilator 956 of FIG. 57 or the
ventilator circuit.
[0194] The sensor outputs information to a controller 1012 that
operates the flow control portion 1013 of the nebulization catheter
system. The flow control portion may include the flow control
assembly 872 (shown in FIG. 55) as well as include the control
functions for gas pressurization. The controller 1012 may have
preset triggering parameters or may be user adjustable. The
controller 1012 may use airway flow, pressure, or physiological
activity as a basis for controlling the flow control assembly 1013.
The controller 1012 may provide for pulsing based upon any one of
the following modes: (1) a controlled volume (bolus) of medicine is
delivered with each pulse; (2) medicine is delivered until a
physiological condition is sensed, e.g. exhalation; or (3) medicine
is delivered for a fixable time interval, e.g. 2 seconds. These
modes of operation may be selectable by the physician based upon
the preferred treatment taking into account the patient's
condition, the type of medicine being delivered, etc.
[0195] It may also be desired to regulate the delivery of aerosol
so that it is not delivered with every inhalation. As mentioned
above, one concern with delivery of an expanding gas is the cooling
effect that it may have on the body. This can be a factor with high
gas flow rates. Accordingly, it may be preferable to deliver
aerosol on every other inhalation or every third inhalation, and so
on. Alternatively, it may be preferred to deliver aerosol for
certain periods of time, e.g. 5 minutes every hour. Therefore, by
alternating aerosol delivery, the cooling effect associated with it
can be reduced.
IX. Alternative Embodiments
A. Nebulizing Catheter Incorporated in Endotracheal Tube
[0196] The various embodiments of nebulizing catheters, disclosed
above, have been described as being either adapted for use in
conjunction with a separate endotracheal tube, or adapted to be
used without an endotracheal tube. If used with an endotracheal
tube, the embodiments of the nebulizing catheter disclosed above
are preferably removable from the endotracheal tube if one is
present. It is noted that many of the embodiments of the present
invention disclosed herein may also be used in conjunction with a
nebulization catheter that is non-removable from an endotracheal
tube, i.e. in which the nebulizing catheter is incorporated into
and forms part of the endotracheal tube. An endotracheal tube that
provides for nebulized medication delivery is described in a patent
application filed by Dr. Neil R. MacIntyre on Mar. 10, 1992
entitled "Endotracheal Tube Adapted for Aerosol Generation at
Distal End Thereof", the entire disclosure of which is incorporated
herein by reference. According to a system developed by Dr.
MacIntyre, there is provided an endotracheal tube that provides for
nebulization of a medication at a distal end thereof. According to
Dr. MacIntryre's system, an endotracheal tube includes two
additional, separate lumens, in addition to its main ventilation
lumen used for the patient's breathing airflow. A medication in a
liquid form is conveyed through one of the additional lumens and a
pressurized gas is conveyed through the other lumen. The two
additional lumens have distal openings near the distal end of the
endotracheal tube airflow lumen. The distal opening of the
pressurized gas lumen directs the pressurized gas across the distal
medication lumen opening thereby nebulizing the liquid medication
so that it can be delivered to the patient's lungs. It is intended
that the present invention covers embodiments of nebulization
catheters that are non-removable relative to an endotracheal
tube.
B. Aerosol Generation with Porous Material
[0197] FIG. 60 shows another catheter 1060 for producing an
aerosol. The catheter 1060 generates an aerosol, or aerosol-like
plume by use of a porous material or sponge located in a lumen of
the catheter. The catheter 1060 has a main shaft 1064 with a lumen
1068 through which liquid medicine is conveyed under pressure and a
lumen 1072 through which a gas is conveyed under pressure. A porous
material 1076 is located in a distal end of the shaft 1064 so that
both lumens 1068 and 1072 convey their contents into the porous
material 1076. The porous material 1076 may be a porous
polyethylene made by Porex. Alternatively, the porous material may
be a polymer sponge or other polymer material. Located in the main
shaft 1064 distal of the porous 1076 is an end cap 1080 with an
orifice 1084 located therein. The orifice is small and maintains a
positive back pressure in the catheter shaft and porous material
area. The end cap 1080 is separated from the distal side of the
porous material 1076 by a small gap 1082. The liquid and gas
delivered under pressure to the porous material 1076 migrate
through the porous across the gap 1082 toward the aperture 1084.
The liquid and gas become intermixed under pressure and as they are
expelled from the fine tip orifice the gas expands and disperses
the liquid particles into fine droplets. Upon discharging through
the aperture 1084, the medicine forms tiny droplets, e.g. an
aerosol. The aerosol is conveyed to the lungs of the patient in a
manner similar to that described in the embodiments above. An
advantage of using a porous material or sponge at the distal liquid
orifice is that it reduces drooling of the liquid.
C. Secondary Aerosol Generation
[0198] In some situations it may be desirable to modify the primary
aerosol spray generated by a nebulization catheter. One way that
this can be accomplished is by causing the primary aerosol spray to
impact upon a baffle placed in its path, the velocity and direction
of the spray can be altered and the size of the distribution of the
aerosol can be modified creating a secondary aerosol. Impaction
upon a properly located baffle can break up large aerosol particles
creating a finer aerosol mist. The baffle also deflects or diffuses
the airstream carrying the particles reducing their forward
velocity and altering their direction. This can lessen impaction on
the carina or airways and enhance the entrainment of the particles
into the inspiratory flow. Embodiments of nebulizing catheters
incorporating an impaction baffle to provide a secondary aerosol
are shown in FIGS. 61-64.
[0199] Referring to FIG. 61, a nebulization catheter 1140 has a gas
lumen 1142 and a liquid lumen 1144 located in a shaft 1146 of the
catheter. The gas lumen 1142 conveys a pressurized gas to a distal
gas orifice 1148 and the liquid lumen 1144 conveys liquid to a
distal liquid orifice 1150. A baffle 1152 connects to a baffle
extension tube 1154 so that the baffle 1152 is located distally of
the liquid orifice 1150. The baffle 1152 is preferably located as
close to the solution orifice 1150 as possible without interfering
with the generation of the primary aerosol.
[0200] Some of the primary aerosol that is not broken into fine
particles may remain on the baffle 1152 and build up over time
forming a thin liquid film on the surface of the baffle 1152. If
this film is left to build up, it will form droplets that either
fall or are blown off the baffle. These droplets may become quite
large and of little or no therapeutic value representing a waste of
the solution.
[0201] In order to recirculate this film of solution, the baffle
1152 may be used to collect and return the liquid solution to a
liquid supply lumen 1144 To achieve this, the baffle may have with
one or more orifices 1158 or porous material on its surface of the
baffle 1152 for the collection of the film of solution. The
orifices 1158 drain into or through the baffle, and are in fluid
communication with the solution supply lumen 1144 via a lumen
located inside of the extension tube 1154. The lumen inside the
extension tube 1154 may communicate directly with the solution
lumen 1144 or extension thereof.
[0202] In the embodiment of FIG. 61, the negative pressure
generated at the nebulization orifice 1150 by the gas flow over it
is used to draw the recirculated solution from the baffle
recirculation orifice 1158 via the lumen in the extension 1154 and
out the liquid orifice 1150 again. In this case, the recirculation
orifices 1158 or surface should be in an area of higher ambient
pressure than the solution orifice 1150 to cause the recirculation
of the fluid. This may be accomplished by locating the collection
orifices 1158 on a distal side of the baffle 1152 opposite the
solution and gas orifices 1150 and 1148. The flow of new solution
(from the proximally located solution reservoir) pumped into the
solution lumen 1144 should be less than the flow drawn from the
solution orifice 1150 to ensure that least some of the solution
from the baffle 1152 is recirculated to the orifice 1150.
[0203] FIG. 62 shows another embodiment of a nebulization catheter
that incorporates a baffle for the purpose of generating a
secondary aerosol. This embodiment is similar to the nebulization
catheter in FIG. 61 with the exception that the recirculated fluid
is drawn back into a recirculation lumen 1160 in the catheter shaft
1146. The recirculation lumen 1160 communicates with the liquid
lumen 1144 at a junction 1162 at which location the recirculated
solution is mixed with newly supplied liquid in the solution lumen
1144.
[0204] FIG. 63 shows another alternative embodiment. This
embodiment is similar to the embodiment of FIG. 62 except that the
recirculated solution is routed from the baffle 1152 to the
recirculation lumen 1160 and then to a separate solution orifice
for re-nebulization. This dedicated solution orifice 1161 is also
located at the catheter tip near a gas orifice 1148 to produce
nebulization. The aerosol generated from this separate orifice 1161
is directed into the common baffle 1158 to break it into smaller
particles and a portion of the solution will again remain on the
baffle and be recirculated. This approach can eliminate the
difficulties of balancing the flow of new and recirculated solution
to a single solution orifice.
[0205] Referring to FIG. 64, there is another embodiment of a
nebulizing catheter incorporating a baffle for the generation of a
secondary aerosol. In this embodiment, a nebulizing catheter 1170
has a shaft 1172 with a liquid lumen 1174 connected to a liquid
supply 1176. A gas lumen 1178 connects to a pressured gas source
1180. The liquid lumen 1174 communicates with a distal liquid
orifice 1182 and the gas lumen communicates with a distal gas
orifice 1184. A baffle 1186 is located in front of the liquid
orifice 1182. Aerosol impacting on the baffle 1186 produces a
secondary aerosol that flows around the baffle 1186. A residue film
of liquid migrates around the baffle 1186 and enters into baffle
orifices 1190 located on the distal side of the baffle 1186. The
baffle orifices 1190 communicate with a recirculation lumen 1192
that extends through the catheter shaft to a reservoir 1194 located
outside of the body where the recirculated solution is combined
with non-recirculated solution pumped from a proximal drug
reservoir. The flow of recirculated and non-recirculated solution
into the system should be carefully balanced to match the amount of
aerosol generated. To achieve this, flow metering and pumping
strategies can be employed.
D. Nebulization Catheter with Pressurized Propellant-Drug
Canister
[0206] In the embodiments described above, medicine is delivered in
liquid form to the distal liquid orifice. In another embodiment,
illustrated in the diagram of FIG. 65, the medicine may be mixed
with a propellant and maintained under pressure and delivered under
pressure to the distal tip of a nebulizing catheter 1198. A
pressured medicine-liquid propellant mixture could be supplied from
a pressurized canister 1200 such as those used as a component of a
metered or non-metered dose inhaler. By using a propellant, an
aerosol could be generated from the distal end 1202 of the catheter
even without the addition of the pressurized nebulizing gas.
However, the delivery of pressurized gas 1204 from the distal end
of the nebulization catheter would be used to assist in breaking up
any larger medicine particles and also assist dispersing the
aerosolized drug solution delivered through the catheter as well as
help shape the aerosol plume. For example, the delivery of the
pressurized, nebulizing gas may assist in shielding the aerosol
generated by the medicine-liquid propellant mixture and help avoid
losses due to impaction.
E. Nebulizing Function Incorporated in Suction Catheter
[0207] As mentioned above, the nebulizing catheter can be
incorporated into another device, such as an endotracheal tube,
either removably or non-removably. Another such device into which a
nebulizing catheter can be adapted is a suction or aspiration
catheter. A suction catheter is sometimes used in conjunction with
patients who are intubated. A suction catheter has an O.D. and a
length such that it can be inserted through the ventilation lumen
of an endotracheal tube. The suction catheter is used to aspirate
fluids and mucin secretions that collect in the respiratory tract
of in the endotracheal tube of a patient who is intubated. A
conventional suction catheter is inserted down the ventilation
lumen of the endotracheal tube and out the distal end. A mucolytic
agent may be instilled as a liquid via a lumen of the suction
catheter to help in the withdrawal of mucin from the trachea or
bronchi. The suction catheter may then be withdrawn from the
endotracheal tube and either disposed or retained in a sterile
sheath connected to a proximal end of the endotracheal tube so that
it can be reinserted into the endotracheal tube again.
[0208] A nebulizing catheter can be incorporated into a suction
catheter so that a single device can perform both the functions of
aspiration and nebulization for aerosol delivery. In an alternative
embodiment of the present invention, the nebulizing catheter, such
as described above, could be incorporated into a suction catheter
so that a single catheter can provide both functions. This could be
accomplished by provided any of the embodiments of the nebulization
catheter described above with a separate lumen for the purpose of
providing a suction to withdraw fluid from a patient's respiratory
tract. Combining the functions of a suction catheter and
nebulization catheter into a single device has the advantages of
avoiding the expense of separate products as well as avoiding the
inconvenience of inserting and withdrawing separate devices.
[0209] Embodiments of a suction catheter combined with a
nebulization catheter are shown catheter is FIGS. 66-73. FIGS.
66-70 show a suction catheter assembly 1220. The suction catheter
assembly 1220 includes a suction catheter shaft 1222 slidably
located inside of a flexible sheath 1224. A suction lumen 1225
extends through the suction catheter shaft 1222. A proximal
manifold 1226 includes a port 1228 for connecting a vacuum source
to the suction catheter lumen 1225. A valve 1230 operates to open
and close the port 1228. A distal sleeve 1232 provides for
connecting to an endotracheal tube such that the suction catheter
shaft 1222 can be inserted into the endotracheal tube by pushing
the proximal manifold 1226 toward the distal sleeve 1232. The
distal sleeve 1232 may include a manifold for connection to a flush
port 1233. A seal 1235 located in the sleeve 1232 closely bears on
the suction catheter shaft to remove mucous or other unwanted
materials that can be removed via the flush port 1233. The shaft of
the suction catheter may be provided with a low friction, e.g.
hydrophilic, coating to reduce adhesion of mucous.
[0210] The suction catheter assembly 1220 includes two additional
lumens 1234 and 1236. These lumens 1234 and 1236 are located in a
wall of the suction catheter shaft 1222. These lumens 1234 and 1236
communicate with distal orifices 1238 and 1240 located at a distal
end of the suction catheter shaft 1222. These lumens 1234 and 1236
are used to deliver a liquid medicine and a pressurized gas for
nebulizing the liquid medicine, as described above. Also located at
a distal end of the suction catheter shaft 1222 are suction
openings 1242.
[0211] The suction catheter assembly 1220 can be used in a
conventional manner to remove mucin from the trachea and from the
bronchi. The suction catheter assembly 1220 can also be used to
deliver medicines to the lungs as an aerosol by means of the
nebulizing lumens 1234 and 1236. The nebulizing lumens can also be
used to deliver mucolytic agents as an aerosol. Because the fine
aerosol delivered by the nebulizing lumens can be carried by a
patient's inspiratory airflow into the bronchi, the mucolytic agent
can be delivered further into bronchi compared to a suction
catheter that merely instills or generates a coarse spray of a
mucolytic agent. In addition, the flow velocity produced by the gas
pressurization lumen may be used to assist in breaking up mucous at
the end of the suction catheter.
[0212] When using the suction catheter assembly 1220, it can be
positioned so that a distal end of the suction catheter shaft 1222
is close to the distal end of the endotracheal tube 1250 as shown
in FIG. 68 or alternatively the suction catheter shaft 1222 can be
positioned so that it extends past the distal end of the
endotracheal tube 1250 as shown in FIG. 70. As shown in FIG. 70,
the suction catheter shaft 1220 may be formed with a distal
curvature so that the distal end can be brought into proximity with
the tracheal wall.
[0213] Rather than incorporate the nebulizing lumens into the wall
of the suction catheter, it may be preferably in many situations to
use a conventional suction catheter with a stand-alone nebulizing
catheter. The stand-alone nebulizing catheter may be similar to any
of the embodiments described above. A suction catheter and a
nebulizing catheter can readily be used together with the
alternative versions of the manifolds shown in FIGS. 71-73.
[0214] Referring to FIG. 71, an endotracheal tube 1252 has a
proximal end with a single port 1254. A suction catheter 1256 has a
distal manifold 1258. The distal manifold 1256 could be formed as
part of the suction catheter 1256 or could be provided as a
separate component. The suction catheter manifold 1258 connects to
the single port 1254 of the endotracheal tube 1252. The manifold
1258 has a first port 1260 for connecting to a ventilator and a
second port 1264 for connecting to a proximal end of a nebulizing
catheter 1266. As shown in FIG. 71, the nebulizing catheter 1266
includes a sterile sheath 1268 which is similar to the sheath
included on the suction catheter 1262. In the embodiment of FIG.
71, the suction catheter 1256 and the nebulizing catheter 1266 are
positioned alternately inside the ventilation lumen of the
endotracheal tube 1252. The suction catheter or the nebulizing
catheter can be withdrawn temporarily and maintained in its sterile
sheath while the other is being used.
[0215] Referring to FIG. 72 there is another arrangement for
connecting a suction catheter and nebulizing catheter to an
endotracheal tube. In this embodiment, a manifold 1270 connects to
the proximal end of the endotracheal tube 1252. The manifold 1270
has port 1274 for receiving the nebulizing catheter 1266 and a
second port 1276. A distal manifold 1278 of a suction catheter 1280
connects to the second port 1276. The suction catheter manifold
1278 has a port 1282 for connecting to the ventilator. This
arrangement can be used similarly to the arrangement of FIG.
71.
[0216] FIG. 73 shows still another arrangement for connecting a
suction catheter and a nebulizing catheter to an endotracheal tube.
In this embodiment, the endotracheal tube 1252 is provided with a
proximal end that includes dual ports. A first port 1284 receives
the nebulizing catheter 1266. The second port 1286 may be connected
to either directly to a ventilator or may be connected to a distal
end of a suction catheter (not shown) in a conventional manner.
[0217] In another alternative embodiment (not shown), the
nebulizing catheter could be positioned down the suction lumen of
the suction catheter.
[0218] FIG. 74 shows another embodiment of a suction catheter also
incorporating a nebulization of an aerosol. In FIG. 74, a suction
catheter 1400 is extends from the ventilation lumen of an
endotracheal tube 1250. The suction catheter 1400 includes distal
suction orifices 1402 located close to the distal end of the
suction catheter shaft. Located along the suction catheter shaft
proximally of the suction orifices 1402 are one or more pairs of
liquid and gas orifices 1404. The liquid and gas orifice pairs 1404
are located with respect to each other to produce an aerosol of the
liquid being delivered to the liquid orifice as in the previous
embodiments. The nebulization orifices 1404 are oriented radially
from the suction catheter shaft to direct the aerosol delivered
from the nebulization orifices 1404 toward the airway passage wall.
In one embodiment, the aerosol being delivered is a mucolytic
agent. The suction provided by the suction orifices draws the
mucolytic agent delivered from the nebulization orifices as well as
mucous treated by the mucolytic agent in a distal direction into
the suction orifices 1402.
[0219] Another embodiment of the suction catheter with aerosol
delivery is shown in FIG. 75. A suction catheter 1410 is located in
a ventilation lumen of the endotracheal tube 1250. As in the
previous embodiment, the suction catheter 1410 has a distal suction
orifice 1412 for removing mucous from the airway passage. In
addition, the suction catheter 1410 also includes distal gas and
liquid orifices 1414 located in proximity to each other to produce
a aerosol. The liquid and gas orifices are located in a distal
extension 1416 of the suction catheter shaft so that they are
distal of the suction orifice 1412. The liquid and gas nebulization
orifices 1414 are oriented in a proximal direction toward the
suction orifice 1412. The distal extension 1416 is formed to bring
the nebulization orifices 1414 close to the wall of airway passage
so that the aerosol delivered from the nebulization orifices 1414
washes the airway passage wall. As in the previous embodiment, the
aerosol delivered may be a mucolytic agent to facilitate suctioning
of the mucous out of the airway passage. The pressurized gas flow
may be used to contribute to the dislodgement of mucous from the
airway passage walls.
F. Nebulization with Vibration
[0220] A vibrating orifice, a screen with multiple orifices or
perforations, or a vibrating wire located at the distal tip of the
nebulizing catheter may also be employed to assist in the
generation of fine aerosol particles. The vibration may be
generated by electromechanical, hydraulic, pneumatic, or
piezoelectric means. The vibrations may be generated at the tip of
the catheter, in the shaft, or extracorporeally.
[0221] One embodiment of a nebulizing catheter incorporating a
vibrating tip is shown in FIG. 76. A nebulizing catheter 1300
includes a shaft 1302 through which extend a lumen 1304 for the
delivery of a liquid medicine and a lumen 1306 for the delivery of
a pressurized gas. The liquid lumen 1304 communicates with a distal
liquid orifice 1308 and the gas lumen 1306 communicates with a
distal gas orifice 1310 located at a distal end of the nebulizing
catheter shaft. At the tip the orifices 1308 and 1310 may be
drilled or formed in a piezoelectric material 1314 or may be
drilled or formed in an orifice insert, plate, tube or screen
mechanically attached to the tip such that the vibrations of the
material are transferred to orifices. Although both the gas and
liquid orifices may be vibrated, alternatively only the liquid
orifice may be vibrated. In still a further embodiment, the entire
shaft of the catheter may be vibrated so that the vibrations are
transferred to the tip. The vibrations may be amplified by
mechanical means to increase the amplitude of the orifice
oscillation. Two electrical lead wires 1316 and 1318 may be used to
conduct bipolar or unipolar pulses from an extracorporeal generator
and control circuit to the piezoelectric material 1314. The
amplitude and frequency of the orifice vibrations may be adjusted
to optimize aerosol production based on the gas and solution flow
rates, the orifice configuration, and the desired size of the
aerosol particles. The generation device would be provided with a
current leakage sensor to terminate its operation in the event it
detects current leakage in the system. The vibrations can be pulsed
to coincide with inspiration and also to control heat generated by
vibration at the tip. One or more gas supply lumens and orifices at
the catheter tip can be used to assist in the dispersion and
transport of the particles produced at the vibrating orifice.
[0222] In a further alternative embodiment, the orifice may be
vibrated by means of a vibrating wire connected to the orifice that
is caused to vibrate from a generator connected to the proximal
end. In still a further embodiment, a vibrating wire, similar to
the wire tip shown in FIGS. 16-19, may extend distally past a
non-vibrating orifice to cause aerosolization of a liquid delivered
from the orifice that impinges onto the vibrating wire. In a still
further embodiment, the tip may be vibrated remotely, e.g. from a
source outside the body, by means of a magnetic field.
[0223] A liquid supply to the catheter tip can also be rapidly
pulsed to cause small droplets to be ejected at the solution
orifice. This may cause a finer aerosol to be developed than by
feeding a continuous stream of solution to the orifice. The
pulsation can be accomplished by rapidly expanding and contracting
all or part of the solution reservoir (including the lumen). The
expansion and contraction of the reservoir can be caused by
electromechanical, hydraulic, pneumatic, or piezoelectric actuators
forming the reservoir, within the reservoir or moving flexible
portions of the reservoir. Such an embodiment is shown in FIG. 76.
A nebulizing catheter 1500 includes a shaft 1502 having a gas lumen
1502 connected to a source of pressurized gas 1504 and a liquid
medicine lumen 1506 connected to a source of liquid medicine 1508.
Included in the liquid medicine source 1508 is a means for
imparting compression waves or pulsation into the liquid. The waves
are indicated in the liquid at 1509. The wave imparting means may
be a transducer 1510 or other similar device. The vibration
inducing device 1510 may be driven by a frequency generator 1513 at
a frequency greater than 100 hertz. The vibrations induced in the
liquid may be focussed or directed toward the distal liquid orifice
1514.
[0224] In the case where the vibrations are generated at a location
proximal of the tip, the nebulizing catheter shaft may incorporate
a mechanical means in the shaft or near the orifices capable of
transmitting or amplifying the pulsations. In the embodiment of
FIG. 77, a wire 1516 may extend from the pulsation generating means
1510 into the liquid lumen 1506 to help convey the vibrations 1509
to the distal orifice 1514. The pulsations imparted to the liquid
may be used to generate an aerosol from the distal liquid orifice
1514 or alternatively may be used in conjunction with the
pressurized gas delivered through the gas lumen 1502 for enhanced
aerosolization. The amplitude and frequency of the orifice
vibrations may be adjusted to optimize aerosol production based on
the gas and solution flow rates, the orifice configuration, and the
desired size of the aerosol particles.
[0225] The volume dispersed from the liquid orifice 1514 by each
pulse should be less than approximately 10 microliters and the
pulsation should occur at a frequency greater than 100 Hertz,
although smaller volumes and faster frequencies may be used to
produce a finer aerosol. It is preferable that the reservoir and
lumens be constructed or a material of minimal compliance to ensure
minimal attenuation of the pulsation. The gas supply orifice at the
catheter tip can be used to assist in the dispersion and transport
of the particles produced at the solution orifice. These micro
pulsations can be incorporated into a series with pauses between
them to coincide with the patient's inspiratory phase.
G. Other Method for Aerosol Generation
[0226] The above embodiments describe a nebulization catheter in
which an aerosol is generated by directing a pressurized gas
through a catheter near an orifice from which the liquid to be
nebulized exits. It is considered to be within the scope of the
invention described herein to use other means or agents to generate
an aerosol for delivery of a medication to the respiratory tract.
For example, the above embodiments may be used in conjunction with
devices that utilize other means to generate an aerosol of a liquid
medication. A liquid delivered by a single liquid lumen may be
nebulized by applying ultrasonic energy to the liquid,
electrospray, steam, or a micropump similar to those used in ink
jet type printers. These alternative approaches to nebulization may
be substituted for the use of a pressurized gas for some of the
embodiments described above, or may be combined with pressurized
gas or with each other to produce an aerosol of the liquid
medication.
[0227] The nebulization catheter embodiments described herein could
also be used in other types of nebulizers that are used externally
of a patient's respiratory system, such as small volume nebulizers
(SVN), humidification nebulizers, or nebulizers used for ocular or
nasal drug administration. When used in such other types of
nebulizers, the embodiments of the nebulization catheter disclosed
herein provide for a fine aerosol without the potential
disadvantages of impacting the liquid on a baffle or recirculating
the liquid medicine on a continuous basis which are common in such
nebulizers.
[0228] It is intended that the foregoing detailed description be
regarded as illustrative rather than limiting and that it is
understood that the following claims including all equivalents are
intended to define the scope of the invention.
* * * * *