U.S. patent application number 17/175779 was filed with the patent office on 2021-08-26 for cannula for minimizing dilution of dosing during nitric oxide delivery.
The applicant listed for this patent is Mallinckrodt Hospital Products IP Unlimited Company. Invention is credited to Craig Flanagan, Simon Freed, John Klaus, Thomas Kohlmann, Martin D. Meglasson, Manesh Naidu, Parag Shah.
Application Number | 20210260327 17/175779 |
Document ID | / |
Family ID | 1000005570283 |
Filed Date | 2021-08-26 |
United States Patent
Application |
20210260327 |
Kind Code |
A1 |
Flanagan; Craig ; et
al. |
August 26, 2021 |
Cannula For Minimizing Dilution Of Dosing During Nitric Oxide
Delivery
Abstract
Described are nasal cannulas that improve the precision of the
delivered dose for nitric oxide therapy by reducing the dilution of
nitric oxide. The nasal cannulas may reduce the total volume and
potential for retrograde flow during nitric oxide therapy through
the design of the specific dimensions of the flow path and/or
having check valves in the nitric oxide delivery line and/or having
a flapper or umbrella valve dedicated to nitric oxide delivery. The
nasal cannulas may also use materials that limit oxygen diffusion
through the cannula walls. The nosepiece for these cannulas may be
manufactured by a molding technique.
Inventors: |
Flanagan; Craig; (Belmar,
NJ) ; Freed; Simon; (Providence, RI) ; Klaus;
John; (Cottage Grove, WI) ; Kohlmann; Thomas;
(McFarland, WI) ; Meglasson; Martin D.;
(Bloomsbury, NJ) ; Naidu; Manesh; (Randolph,
NJ) ; Shah; Parag; (Morristown, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mallinckrodt Hospital Products IP Unlimited Company |
Dublin |
|
IE |
|
|
Family ID: |
1000005570283 |
Appl. No.: |
17/175779 |
Filed: |
May 4, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15790300 |
Oct 23, 2017 |
10918819 |
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17175779 |
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14096548 |
Dec 4, 2013 |
9795756 |
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15790300 |
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61733134 |
Dec 4, 2012 |
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61784238 |
Mar 14, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 16/0672 20140204;
A61M 16/0666 20130101; A61M 16/0858 20140204; A61M 2202/0208
20130101; A61M 16/06 20130101; A61M 16/0677 20140204; A61M
2202/0275 20130101; A61M 2206/10 20130101; A61M 16/208 20130101;
A61M 2207/00 20130101 |
International
Class: |
A61M 16/06 20060101
A61M016/06 |
Claims
1.-20. (canceled)
21. A method of administering nitric oxide for treating pulmonary
hypertension, the method comprising: administering a pulse of a gas
comprising nitric oxide to a patient in need thereof, wherein the
pulse is administered through a nasal cannula comprising a cannula
nosepiece comprising a nitric oxide flow path having a volume that
is less than 50% of a volume of pulse of the gas comprising nitric
oxide.
22. The method of claim 21, wherein the nasal cannula comprises: a
first lumen, a second lumen, and a third lumen: the first lumen
being a first therapeutic gas lumen for delivering the gas
comprising nitric oxide to the patient, the second lumen being a
triggering lumen, and the third lumen being a second therapeutic
gas lumen for delivering a gas comprising oxygen to the patient;
and wherein the cannula nosepiece has separate flow paths to the
patient for each of (i) the first therapeutic gas lumen, (ii) the
triggering lumen, and (iii) the second therapeutic gas lumen.
23. The method of claim 21, wherein the nasal cannula comprises a
first lumen for delivering the gas comprising nitric oxide to the
patient and a second lumen, wherein the first lumen has a smaller
inner diameter than an inner diameter of the second lumen.
24. The method of claim 21, wherein the pulse of gas comprising
nitric oxide has a volume less than 1 mL.
25. The method of claim 21, wherein the nitric oxide flow path is
less than 40% of the volume of pulse of the gas comprising nitric
oxide.
26. The method of claim 21, wherein the nitric oxide flow path has
a volume less than or equal to 0.035 mL.
27. The method of claim 21, wherein the nasal cannula at least one
of inhibits mixing of nitric oxide and oxygen in the cannula
nosepiece and reduces delivery of nitrogen dioxide to the
patient.
28. A method of administering nitric oxide for treating pulmonary
hypertension, the method comprising: administering a plurality of
pulses of a gas comprising nitric oxide to a patient in need
thereof, wherein the plurality of pulses is administered through a
nasal cannula comprising a cannula nosepiece comprising a nitric
oxide flow path having a volume that is less than 50% of a volume
of each of the plurality of pulses of the gas comprising nitric
oxide.
29. The method of claim 28, wherein the nasal cannula comprises: a
first lumen, a second lumen, and a third lumen: the first lumen
being a first therapeutic gas lumen for delivering a gas comprising
nitric oxide to the patient, the second lumen being a triggering
lumen, and the third lumen being a second therapeutic gas lumen for
delivering a gas comprising oxygen to the patient; and wherein the
cannula nosepiece has separate flow paths to the patient for each
of (i) the first therapeutic gas lumen, (ii) the triggering lumen,
and (iii) the second therapeutic gas lumen.
30. The method of claim 28, wherein the nasal cannula comprises a
first lumen for delivering the gas comprising nitric oxide to the
patient and a second lumen, wherein the first lumen has a smaller
inner diameter than an inner diameter of the second lumen.
31. The method of claim 28, wherein each of the plurality of pulses
of the gas comprising nitric oxide has a volume less than 1 mL.
32. The method of claim 28, wherein the nitric oxide flow path is
less than 40% of the volume of each of the plurality of pulses of
the gas comprising nitric oxide.
33. The method of claim 28, wherein the nitric oxide flow path has
a volume less than or equal to 0.035 mL.
34. The method of claim 28, wherein the nasal cannula at least one
of inhibits mixing of nitric oxide and oxygen in the cannula
nosepiece and reduces delivery of nitrogen dioxide to the
patient.
35. A method of administering nitric oxide to a patient, the method
comprising: administering a plurality of pulses of a gas comprising
nitric oxide to the patient, wherein the plurality of pulses is
administered through a nasal cannula comprising a cannula nosepiece
comprising a nitric oxide flow path having a volume that is less
than 50% of a volume of each of the plurality of pulses of the gas
comprising nitric oxide.
36. The method of claim 35, wherein the nasal cannula comprises: a
first lumen, a second lumen, and a third lumen: the first lumen
being a first therapeutic gas lumen for delivering a gas comprising
nitric oxide to the patient, the second lumen being a triggering
lumen, and the third lumen being a second therapeutic gas lumen for
delivering a gas comprising oxygen to the patient; and wherein the
cannula nosepiece has separate flow paths to the patient for each
of (i) the first therapeutic gas lumen, (ii) the triggering lumen,
and (iii) the second therapeutic gas lumen.
37. The method of claim 35, wherein the nasal cannula comprises a
first lumen for delivering the gas comprising nitric oxide to the
patient and a second lumen, wherein the first lumen has a smaller
inner diameter than an inner diameter of the second lumen.
38. The method of claim 35, wherein each of the plurality of pulses
of the gas comprising nitric oxide has a volume less than 1 mL.
39. The method of claim 35, wherein the nitric oxide flow path is
less than 40% of the volume of each of the plurality of pulses of
the gas comprising nitric oxide.
40. The method of claim 35, wherein the nasal cannula at least one
of inhibits mixing of nitric oxide and oxygen in the cannula
nosepiece and reduces delivery of nitrogen dioxide to the patient.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation under 35 U.S.C. .sctn.
120 of U.S. patent application Ser. No. 15/790,300, filed Oct. 23,
2017, which is a continuation under 35 U.S.C. .sctn. 120 of U.S.
patent application Ser. No. 14/096,548, filed Dec. 4, 2013, now
U.S. Pat. No. 9,795,756, which claims, under 35 USC .sctn. 119(e),
the benefit of U.S. Provisional Application No. 61/733,134, filed
Dec. 4, 2012 and U.S. Provisional Application No. 61/784,238, filed
Mar. 14, 2013, the contents of each of which are hereby
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] Embodiments of the present invention generally relate to the
field of methods and devices for nitric oxide delivery.
BACKGROUND
[0003] Nitric oxide (NO) is a gas that, when inhaled, acts to
dilate blood vessels in the lungs, improving oxygenation of the
blood and reducing pulmonary hypertension. Because of this, nitric
oxide is provided as a therapeutic gas in the inspiratory breathing
gases for patients with pulmonary hypertension.
[0004] Typically, inhaled NO is delivered in a carrier gas from a
high pressure source (such as a pressurized cylinder) to the
patient at or near ambient pressure by means of a respiratory tube
for ICU ventilator bound or anesthesia patients or a nasal cannula
for spontaneously breathing patients. It is particularly
challenging to deliver an accurate and consistent dose to the
patient through a nasal cannula as dilution of the dose can occur
through retrograde flow and diffusion of other gases.
[0005] Delivery of NO may require transit through a nasal cannula.
During patient inhalation and exhalation, a driving pressure
gradient can cause retrograde flow in the nasal cannula supply
lumen, thereby diluting the NO dose in the cannula with exhaled
gas. In addition, diffusion of ambient gasses can occur through the
cannula itself during the transit time of NO through the cannula.
Oxygen is of specific concern as it reacts with NO to form nitrogen
dioxide (NO.sub.2) thereby reducing the NO concentration. This is
further exacerbated by the fact that patients on NO may also
require oxygen therapy. Both of these issues can dilute the
delivered dose of NO during inhaled NO therapy.
[0006] Accordingly, there is a need for new methods and apparatuses
for preventing dilution of dosing within the delivery conduit of a
nitric oxide delivery apparatus.
SUMMARY
[0007] Aspects of the present invention relate to improved nasal
cannulas that minimize retrograde flow and permeation of oxygen
during NO therapy while allowing NO delivery to both nares of the
nostril. Such cannulas may reduce dilution of the delivered dose by
using cannula materials that limit oxygen diffusion through the
cannula walls and/or utilize cannula configurations that prevent
mixing of co-delivered O.sub.2 and NO and/or reduce retrograde
diffusion through the patient end of the cannula. Aspects of the
present invention also relate to methods of minimizing the dilution
of the NO dose. Other aspects pertain to methods of treatment
utilizing these nasal cannulas and/or methods of administration.
Other aspects of the invention relate to methods of manufacturing
multi-lumen cannulas and their nosepieces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawing. It is to be noted, however,
that the appended drawing illustrates only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0009] FIGS. 1A and 1B show the pneumatic paths for the NO, oxygen
and trigger lines in a tri-lumen cannula;
[0010] FIG. 2 shows three lumina integrated into a single cannula
head;
[0011] FIG. 3 shows a cross-section of an integrated three-lumina
cannula;
[0012] FIGS. 4A and 4B show the pneumatic paths for the NO, oxygen
and trigger lines in a quad-lumen cannula;
[0013] FIG. 5 shows four lumina integrated into a single cannula
head;
[0014] FIGS. 6A and 6B show details of duck bill check valves;
[0015] FIGS. 6C and 6D show details of umbrella check valves;
[0016] FIG. 7 shows a nasal cannula with an umbrella or flapper
valve for delivering NO;
[0017] FIG. 8 shows retrograde flow during inspiratory breathing
along with pulsed delivery;
[0018] FIG. 9 shows retrograde flow during both inspiratory and
expiratory breathing;
[0019] FIGS. 10A and 10B show cross-flow between two nasal cannula
prongs;
[0020] FIG. 11 shows a nasal cannula with two lumina of different
sizes;
[0021] FIGS. 12A and 12B show two embodiments of incorporating a
valve into the NO delivery line;
[0022] FIG. 13 shows a dual-lumen cannula for co-delivering NO and
O.sub.2;
[0023] FIG. 14 shows retrograde flow for various cannula
configurations;
[0024] FIGS. 15A-C show the cannula configurations for Tests 1-3 of
FIG. 14;
[0025] FIG. 16 shows a nasal cannula with a triple lumen
nosepiece;
[0026] FIG. 17 shows a molded triple lumen nosepiece prior to
assembly;
[0027] FIG. 18 shows the nasal prong of the assembled molded triple
lumen nosepiece; and
[0028] FIG. 19 shows a perspective and a two-dimensional
representation of a nasal prong with a NO lumen proximal to and
within a trigger lumen.
DETAILED DESCRIPTION
[0029] Methods of delivering inhaled nitric oxide (NO) should
ideally be optimized to ensure accurate and consistent delivery of
the dose to the patient. Typically, NO is delivered at relatively
low volumetric percent concentrations in a carrier gas. Nitrogen is
a common carrier gas for NO delivery because nitrogen is
non-reactive with NO, but other inert carrier gases such as helium
may be used. Delivery of the NO/N.sub.2 gas mixture to the patient
typically requires that the gas travel from a high pressure NO
source (such as a pressurized cylinder) to the patient at or near
ambient pressure by means of a respiratory tube for ICU ventilator
bound or anesthesia patients or a nasal cannula for spontaneously
breathing patients. This travel of the NO is ideally devoid of
contact with other gasses, such as ambient air, oxygen, carbon
dioxide, etc., until the gas enters the patient's upper respiratory
tract. However, in practice, this is not easily achieved.
Specifically, oxygen and ambient air can enter the delivery system
at a number of points as follows: [0030] During the connection of
the high pressure source (typically cylinder) to the delivery
device [0031] During the NO gas transit through the cannula (by way
of diffusion across the cannula wall) [0032] During the
inhalation/exhalation cycle when a driving pressure gradient seeks
to reverse flow in the nasal cannula NO supply lumen producing
mixing within the cannula with ambient air
[0033] The dilution of NO during pulsed NO therapy may be
problematic because only a small volume of NO is delivered to the
patient. For example, the NO-containing gas may be administered in
pulses less than 1 mL. With small pulse volumes, even small volumes
of retrograde flow or diffused gases may be significant because the
NO dose may be diluted.
Materials:
[0034] One or more embodiments of the present invention relate to a
nasal cannula that addresses one or more of these above sources of
oxygen/NO contact and thereby dilution of the intended NO dose. One
particular source of oxygen that may be minimized is the transit of
oxygen across the cannula walls. In one or more embodiments, a
cannula is provided that includes a smaller inside diameter (ID)
delivery tube/lumen for NO. This smaller ID tube reduces the
transit time of the NO molecules through the cannula, thereby
reducing the time available for oxygen to diffuse across the walls
of the cannula and oxidize the internal NO into NO.sub.2.
[0035] Another approach to minimize the oxygen contact provided by
oxygen diffusion across the cannula walls is to use a wall material
that minimizes the oxygen diffusion rate. Accordingly, in some
embodiments, the cannula wall comprises a material with a low
oxygen diffusion coefficient. Polyvinyl chloride (PVC) is currently
a common material for constructing nasal cannulas, but it is not
optimal for reducing oxygen diffusion through the cannula walls.
Accordingly, some embodiments provide using urethane or another
similar soft material. In some embodiments, the urethane or other
soft material includes an additive to enhance the resistance to
oxygen diffusion. Examples of suitable additives include oxygen
resistant polymers such as polyvinylidene chloride (PVDC), ethylene
vinyl alcohol (EVOH), polyamide (PA) or similar materials.
Alternatively, PVC may be used as the cannula material, but one or
more additives such as oxygen resistant polymers may be
incorporated to reduce the oxygen diffusion coefficient of the
material. The oxygen resistant polymers may be incorporated into
the urethane or other cannula material through co-extrusion. Such
an extrusion may be achieved with a dual head extruder.
Pneumatic Configurations:
[0036] Another potential source of nitric oxide dilution is from
retrograde flow in the nasal cannula. Retrograde flow, also known
as cross flow, is a phenomenon in which ambient air flows in
opposite directions between the two delivery prongs of the nasal
cannula. As shown in FIG. 10A, during normal pulsed delivery, NO
flows out of both nasal prongs of the cannula. However, during the
static phase between pulses, ambient air can flow in a circular
motion in through one prong and out the other prong as shown in
FIG. 10B. The degree of retrograde flow depends on the pressure
difference between the nares during both the inhalation and
exhalation phase. The pressure difference between the nares can
vary depending on the person's breathing pattern, placement of the
nasal prongs and the degree of misbalance between the nasal flow
during breathing. Retrograde flow results in dilution and washout
of the NO in the nasal prongs and flow path. This can cause a delay
or reduction in the delivered dose. Furthermore, air may react with
nitric oxide in the nasal cannula, thus forming NO.sub.2 and
further diluting the NO concentration.
[0037] Accordingly, aspects of the present invention also provide
nasal cannulas that may minimize the retrograde flow in the nasal
cannula. Such nasal cannulas may include a means of delivering
oxygen and therapeutic gas containing NO, and may be able to
transmit pressure transients associated with inhalation-based gas
flow triggering. If the cannulas deliver oxygen in addition to NO,
the oxygen may be provided by an oxygen conserver or an oxygen
concentrator.
[0038] In one or more embodiments, the nasal cannula has two lumina
(i.e. a dual-lumen cannula). FIG. 11 shows an exemplary dual-lumen
cannula that delivers nitric oxide in a separate lumen than is used
to deliver oxygen and/or trigger the delivery device. The NO lumen
carries therapeutic gas comprising NO from the NO delivery device
to the patient. The trigger lumen does not deliver gas to the
patient, but instead establishes fluid communication between the
patient's nares and a trigger sensor in the NO delivery device.
When the patient begins a breath, a drop in pressure occurs in the
nares. This pressure signal is communicated through the trigger
lumen to the trigger sensor, which then senses that the patient has
begun inspiration. The trigger sensor can then send a signal to a
CPU in the NO delivery device so that the CPU will open a control
valve to deliver NO to the patient, such as a pulse of NO in a
carrier gas.
[0039] As shown in FIG. 11, in some embodiments the lumen that
carries the nitric-oxide containing gas may have a smaller inner
diameter than the other lumen such as the triggering lumen. In
these embodiments, the cannula may reduce dilution by at least two
potential mechanisms: 1) the cannula may minimize mixing of oxygen
and NO by two means, first a reduction in retrograde flow into the
small ID NO carrying lumen due to the smaller, ID, second the
volume of gas per unit length is reduced thereby reducing the bulk
volume of gas mixing occurring; and 2) the narrow ID produces a
narrow jet of gas flow which effectively minimizes O.sub.2/NO
mixing during NO delivery until much further into the nasal cavity.
The diameter of the small lumen may be minimized by engineering
design such that it is as small as reasonably possible without
producing confounding upstream effects on the flow delivery
mechanics of the device. In some embodiments, the ratio of the ID
of the NO lumen to the ID of the trigger lumen may be 1:1, 1:1.2,
1:1.3, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6,
1:7, 1:8, 1:9, 1:10, 1:12, 1:15, 1:20, 1:25 or 1:30.
[0040] Also, the geometry of the nasal cannula lumina may be
optimized to prevent retrograde flow. Thus, in addition to circular
or parabolic cross-sections, the cross-section of any of the nasal
cannula lumina described herein may be square, rectangular,
triangular or any other regular or irregular shape to minimize dose
dilution. When one or more cross-sectional areas are not circular,
then the ratio of inner diameters may be the square root of the
ratio of the surface areas of the two lumina sections.
[0041] Alternatively, a dual-lumen cannula may have a first lumen
for oxygen delivery and a second lumen for delivery of NO and
transmitting the pressure signal for the trigger sensor. Such a two
lumina configuration is shown in FIG. 13. In this configuration,
the first lumen carries oxygen from the oxygen
conserver/concentrator to the nosepiece of the cannula. The second
lumen delivers NO from the nitric oxide delivery device to the
patient and delivers the pressure-based triggering signal from the
patient to trigger sensor of the nitric oxide delivery device. Both
lumina would be constructed to "tee" to both nares and thus be in
unobstructed fluid communication with both nares as shown in FIG.
13.
[0042] The first lumen for carrying oxygen may be constructed with
lumen inner diameter geometry consistent with industry norms. For
instance, nasal cannulas with rated 6 LPM oxygen delivery capacity
typically provide an oxygen lumen inner diameter of approximately
0.080'' at or near the nosepiece.
[0043] The second lumen of the this dual-lumen cannula may have a
geometry unique to the gas delivery objectives of the nitric oxide
delivery system. Nitric oxide delivery systems which pulse nitric
oxide gas into the patient are believed to have optimal clinical
efficacy when a pulse or flow of nitric oxide is delivered to the
patient as early in the inspiratory phase as possible. Therefore,
any pneumatic delays would not be optimal. Further, the shape of
the flow waveform as delivered by the nitric oxide delivery system
is, optimally, not distorted during transit from the device to the
patient. In addition, the transit of the pressure signal from the
patient indicative of inspiratory effort preferably is not
delayed/distorted when in transit from the patient back to the
device. Finally, the volume of potential nitric oxide mixing with
either exhaled gas or ambient gas is preferably minimized to reduce
the potential for oxidation of nitric oxide at the nosepiece of the
cannula, which again can produce NO.sub.2 which dilutes the NO dose
and is a known respiratory irritant.
[0044] In order to achieve the goals described above for the second
lumen, there are several competing metrics of lumen ID optimization
as noted below: [0045] a. Reduce NO.sub.2 formation->Reduce
lumen ID [0046] b. Maintain volumetric NO dosing
accuracy->Reduce lumen ID [0047] c. Reduce NO flow
distortion->Lumen ID within certain bounds [0048] d. Minimize
trigger signal attenuation or delay->Increase lumen ID
[0049] Therefore, an optimal inner diameter dimension of the second
lumen would address all of these concerns to ensure adequate device
performance. Such optimal ID dimensions may vary depending on the
volume of NO-containing gas delivered by the nitric oxide delivery
device. For example, a nitric oxide delivery device may deliver
pulses of NO-containing gas with a minimum dose volume of 0.35 mL.
In order to ensure volumetric dosing accuracy, it is preferable
that no more than 10% of the dose can be lost due to ambient bleed
of NO in between inspiratory efforts. Such a bleed can occur during
the exhalation phase in which imbalances in the flow out of the
nostrils results in a "high flow nostril" and a "low flow nostril."
Flow into the prong from the high flow nostril may result in flow
of out of (gas loss out of) the prong of the low flow nostril. This
gas, which is located in the "U" shaped portion of the tee'd lumen,
is lost to ambient during the exhalation phase and would consist of
NO therapeutic gas. Therefore, one or more embodiments of the
present invention limit the internal volume of this "U" shape to be
no more than 10% of the minimum dose volume (i.e. 0.035 mL for a
0.35 mL pulse of therapeutic gas), thus ensuring acceptable NO loss
to ambient during the exhalation phase. Such a requirement of 0.035
mL requires a lumen ID within the "U" segment of no more than
0.046'' given a prong length of 8 mm and a prong spacing of 16 mm.
Therefore, a lumen ID significantly larger than 0.046'' would not
be advantageous to maintaining dose volume accuracy for minimum
dose volumes of 0.35 mL. Of course, it is understood that the
mathematics of this construct would be modified by systems with
larger or smaller minimum dose volumes appropriately, or with
different prong lengths and/or prong spacing. One skilled in the
art can perform the required calculations to determine the ID
required to provide a desired volume in the "U" section so that it
does not exceed 10% of the dose volume. Furthermore, depending on
the required accuracy for the dosing, the internal "U" volume or
other volume available for cross-flow may be less than 50%, 45%,
40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 4%, 3%, 2% or 1% of the dose
volume.
[0050] In addition to the volumetric dosing accuracy concern,
another concern is that the second lumen ID not produce gas flow
distortion. However, given that gas flow in a nitric oxide system
may use restrictors which are significantly smaller in inner
diameter than a NO lumen ID of 0.046 inches, such distortion may
not actually occur.
[0051] Finally, the inner diameter of the second lumen preferably
does not produce undue signal propagation delay from the patient to
the device. Such delay is believed to occur as pneumatic tubes
behave as first order pneumatic low pass filters and attenuate
higher bandwidth signal components. Modification of the inner
diameters is known to change the band pass characteristics of the
filtering effect. However, as noted earlier, the inner diameter (at
the U) may be fixed to a certain maximum ID based on the required
dose delivery accuracy of the system. Therefore, in order to
minimize the effects of the potentially frequency attenuated
pressure signal, two measures can be taken. First the upstream
(close to device) diameter of the second lumen may be adjusted to
widen (optimize) the band pass characteristics of the cannula. This
may ensure that unneeded compressible volume is unavailable
upstream of the nose piece restriction (0.046'' ID restriction).
This reduces the compressible volume in the cannula and effectively
increases the bandpass characteristics of the cannula. The second
measure which can be taken is to trigger the initiation of pulse
delivery on the device not based on a threshold pressure level (the
magnitude of which can which can be delayed by frequency
attenuation) but by triggering the device based on a pattern of
sloping pressure indicative of patient effort. Such a slope may be
reduced in magnitude by the filtering characteristics of the
tubing, however, the slope will still be present for algorithmic
triggering decisions by the device. However, such a triggering
implementation is optional.
[0052] Accordingly, in some embodiments, the dual lumen cannula
would have an oxygen lumen in the range from 0.05 to 0.12'' ID
(such as about 0.080'' ID) which tees at the nosepiece and is in
fluid communication with both nares. It would also have a second
(nitric oxide) lumen (similarly in fluid communication with both
nares) with an internal tubing diameter dictated by volumetric
dosing accuracy considerations and the second lumen may have an ID
in the range from 0.01 to 0.08'' (such as about 0.046'' ID) with
upstream tubing adjusted to optimize the bandpass performance of
the system. Finally, device triggering methodologies based not on
pressure thresholds, but based on pressure slope trends can also be
employed to improve overall timely delivery of dosing to the
patient.
[0053] Other pneumatic configurations for the nasal cannula may
utilize different numbers of lumina. In one or more embodiments,
the nasal cannula has three lumina (i.e. a tri-lumen cannula). FIG.
1A shows an exemplary set of pneumatic paths of the three
individual lumen from a nitric oxide delivery device to the
patient. The three lumina may include a NO lumen, a trigger sensor
lumen and an oxygen lumen. The oxygen lumen carries an
oxygen-enriched gas (such as oxygen-enriched air or substantially
pure oxygen) from an oxygen source to the patient. The oxygen
source may be a typical oxygen pulsing device, or may be a port on
the NO delivery device that delivers the oxygen-enriched gas. FIG.
1B shows the three lumina aggregated into a single cannula. In
FIGS. 1A and 1B, the NO lumen is tee'd at some point between the
patient and the NO delivery device. Further, the oxygen and trigger
lumina are also tee'd at some point between the device and the
patient and might be tee'd in two locations, such as having an
additional tee in the cannula head at the two nasal prongs.
[0054] Again, all three of the lumina may be integrated into a
single cannula. FIG. 2 shows one such method for integration of the
three lumina at the head (nose bridge fitting) of the cannula. The
separation of the pneumatic paths or lumina in FIG. 2 is by means
of partitions or diaphragms within the head and prongs of the
cannula. The NO supply traverses to the head through a lower gas
resistance source to higher resistance orifices integrated into the
prongs of the cannula. All lumina are separated by a diaphragm
partition within the head of the cannula and within the prongs of
the cannula, which prevents mixing of the fluid streams in the
separate lumina.
[0055] The tubes of the cannula carry backwards towards the patient
and may be affixed to each other so as to produce a clean single
element umbilical between the cannula head and the device as shown
in FIG. 3, which provides a cross-section. Alternately, the three
lumina can be extruded through a single die producing a multi-lumen
tube.
[0056] As can be seen from FIG. 2, the NO delivery tube may
decrease in inner diameter (ID) once the tubing enters the head of
the nasal cannula. Accordingly, in one or more embodiments, the
pneumatic resistance is greater in the prongs of the nasal cannula
than in the tubing carrying the NO from the NO delivery device to
the cannula head. Such a device may have many advantages. In some
embodiments, the smaller ID tubing of the dedicated NO delivery
lumen will allow for: [0057] Short gas transit times [0058] Reduced
inspiratory/expiratory phase retrograde flow of ambient air into
the lumen (reduced according to Knudsen diffusion which states that
diffusion rate is proportionate to the mean free path length of the
gas molecule which is reduced with smaller ID) [0059] Increased gas
resistance to flow (smaller ID tubing produces gas flow resistance
which is inversely proportional to the fourth power of tubing
radius by Poiseuille's Law). [0060] Reduced volume in the tee'd
loop of the NO delivery lumen
[0061] All of the above may serve to reduce the potential for
retrograde flow and/or reduce the volume of retrograde flow and/or
reduce the contact or contact duration between NO and other gasses
including oxygen in the cannula. This will reduce the dilution of
NO and thereby increase the precision of the delivered NO dose.
[0062] The ID of the NO lumen may decrease from a maximum ID to a
minimum ID. In some embodiments, the ratio of the minimum ID to the
maximum ID of the NO lumen may be 1:1, 1:1.2, 1:1.3, 1:1.5, 1:2,
1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:7, 1:8, 1:9 or
1:10.
[0063] The trigger lumen ID may be comparatively much larger than
the NO lumen ID. Trigger pressure drop on inhalation must be
transmitted through this cannula lumen with the smallest possible
loss of signal magnitude to the NO delivery device which in turn
uses this pressure signal to deliver pulsed NO. Again, in some
embodiments, the ratio of the ID of the NO lumen to the ID of
trigger lumen may be 1:1, 1:1.2, 1:1.3, 1:1.5, 1:2, 1:2.5, 1:3,
1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:12,
1:15, 1:20, 1:25 or 1:30.
[0064] The oxygen lumen may also be larger than the NO lumen to
minimize oxygen flow resistance and to reduce gas flow speed at the
prongs which could serve to interfere with the triggering pressure
signal due to gas flow effects such from Bernoulli's principle. As
with the trigger lumen, in some embodiments the ratio of the ID of
the NO lumen to the ID of the oxygen lumen may be 1:1, 1:1.2,
1:1.3, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6,
1:7, 1:8, 1:9, 1:10, 1:12, 1:15, 1:20, 1:25 or 1:30.
[0065] Another pneumatic configuration is shown in FIGS. 4A and 4B.
Like the pneumatic configurations shown in FIGS. 1A and 1B, this
configuration separates the pneumatic paths of the NO, oxygen and
trigger. However, unlike the configuration shown in FIGS. 1A and
1B, in the configuration shown in FIGS. 4A and 4B, the NO flow
delivery paths to each nostril are kept separate and distinct and
have their own pneumatic delivery source at the NO delivery device.
Accordingly, this configuration has four lumina (i.e. a quad-lumen
cannula).
[0066] One potential benefit of the quad-lumen approach is to
prevent movement of gas through the tee'd delivery loop of the NO
supply line during exhalation. This may reduce NO/oxygen contact.
However, unlike the tri-lumen cannula, use of the quad-lumen
cannula may require dedicated pneumatic circuitry for each NO
lumen.
[0067] FIG. 5 shows one potential method for achieving this
configuration at the cannula head. As with the tri-lumen cannula,
the quad-lumen cannula fuses the lumen of the cannula into a single
umbilical between the cannula head and the device.
[0068] With any of the pneumatic configurations described herein,
there may be other modifications of the cannula to improve NO
dosing. In one or more embodiments, provided is a nasal cannula
with one or more check valves in the nitric oxide delivery line.
This configuration may be combined with one of the multi-lumen
configurations described above. The check valves(s) help to prevent
retrograde gas movement into the NO supply lumen during
inhalation/exhalation. Such a check valve might consist of any low
cracking pressure check valve which is placed at some point in the
NO delivery path. Such check valves may include, but are not
limited to, duckbill valves or umbrella valves. Exemplary duck bill
valves are shown in FIGS. 6A and 6B and exemplary umbrella valves
are shown in FIGS. 6C and 6D. These check valves may be miniature
check valves so to have the proper dimensions to fit in the NO
delivery lumen.
[0069] In one or more embodiments, provided is an NO delivery
cannula having a small flapper or umbrella check valve at the head
of the cannula allowing pulses of NO to be delivered to the general
nose/mouth area during device NO pulsing. An exemplary
configuration of a nasal cannula with such a flapper or umbrella
valve is shown in FIG. 7. This configuration would allow NO to flow
into either/both open nares upon inhalation. The O.sub.2 and
trigger lumen may be combined (as shown in FIG. 7) or kept separate
to improve the signal-to-noise performance of the trigger lumen.
Such a configuration with the flapper valve would prevent
retrograde flow of oxygen into the NO delivery path thereby
reducing the potential for dilution of the dose. A diaphragm or
other barrier separates the NO delivery line from the
O.sub.2/trigger line at the cannula head to prevent mixing.
[0070] This pneumatic configuration may be combined with any of the
other pneumatic configurations described above.
[0071] In one or more embodiments, also provided is a nasal cannula
incorporating an impermeable or semi-permeable membrane. The
membrane may be movable or fixed but can be actively or passively
moved when needed, that separates the NO containing gas or material
from the O.sub.2 containing gas or material until the NO needs to
be delivered to the patient. This membrane may reduce one or more
of the contact time, surface area and diffusion rate between the NO
and O.sub.2 containing gases. This may reduce the formation of
NO.sub.2, which dilutes the intended NO delivery concentration.
[0072] In some embodiments of the membrane, a normally-closed valve
at the tip of the NO containing cannula prevents air from
contacting the NO containing gas inside the cannula until the valve
opening is triggered (e.g. by a drop in pressure caused by
inhalation by the patient or by the positive pressure caused by the
delivery device as it attempts to deliver the NO containing gas to
the patient). When the valve opening is triggered, the NO is then
delivered to the patient. One embodiment of such a valve is shown
in FIG. 12A.
[0073] In one or more embodiments, also provided is a system to
expel the gas or other NO containing material that does come in
contact with O.sub.2 containing gas or material, which may have
otherwise formed NO.sub.2 in this mixture. The system may
subsequently allow another part of the NO containing gas or
material that has minimal or no NO.sub.2 to be delivered to the
patient Again, this NO.sub.2 formation could serve to dilute the NO
dose before delivery to the patient.
[0074] In some embodiments of this system, this system may comprise
an electromechanical valve system that actuates to pump out a fixed
or adjustable amount of gas mixture that might contain NO.sub.2
through a separate orifice than the cannula opening to the patient.
The system may then actuate to pump the NO containing gas or
material to the patient. One embodiment of such a system is shown
as a 3-way valve in FIG. 12B.
[0075] The membrane and/or valve system may be combined with any of
the other pneumatic configurations described above.
Manufacturing of Multi-Lumen Nasal Cannulas
[0076] As described above, the individual lumen of a multi-lumen
cannula may be separately manufactured and then affixed to each
other, or the multiple lumina can be extruded through a single die
producing a multi-lumen tube.
[0077] According to one or more embodiments, the multi-lumen
nosepiece of the multi-lumen cannulas described herein may be
manufactured by the following molding technique. For example, the
cannula may have a triple lumen cannula nosepiece for separate
oxygen, nitric oxide and triggering lumina. In one or more
embodiments, the design of the nosepiece for the triple lumen
cannula involves three lumens, two with inner diameters of
approximately 0.080'' (for oxygen and triggering) and one with a
smaller inner diameter of approximately 0.045'' (for nitric oxide)
as shown in FIG. 16. However, this configuration may not be readily
molded by typical injection molding techniques as the small lumen
would require an injector pin (of outer diameter 0.045'') which is
too small to be robust in a molding tool designed to last for many
uses, such as a million or more shots.
[0078] Accordingly, one approach to manufacture the multi-lumen
cannula nosepiece is to mold two halves in urethane, PVC, silicone
or other low durometer elastomer with the internals of the large
lumen defined by larger injector pins (outer diameter 0.080'') and
with small half lumen indents defining the outline of the small
lumen. These two halves would then be folded and bonded together,
preferably with a bonding technique which does not produce residue
or flash such as RF welding, to form a whole nosepiece. FIG. 17
shows one embodiment to circumvent the injector pin limitation with
the small ID lumen being defined by indents in the halves, the two
halves would be molded flat in one shot with a webbing holding the
halves together and providing gross alignment during the folding
and bonding process. Optionally, the molded halves may comprise
integral holes and mating cylindrical tabs or other complementary
members so that the halves will be properly aligned when they are
folded together. The webbing may also be optional if appropriate
complementary indexing members on the two halves ensure that the
two portions forming the outer wall of the NO lumen will be
properly aligned. The assembled nosepiece allows for three lumen
inputs and tee's each lumen input within the internals of the
nosepiece proper. FIG. 18 shows a perspective view of the nasal
prong of the multi-lumen cannula nosepiece of FIG. 17 after the two
halves have been assembled.
[0079] Again, the lumen ID may be adjusted as described in the
previous sections. For example, the ID of the oxygen lumen may
range from 0.05 to 0.12'', the ID of the trigger lumen may range
from 0.05 to 0.12'', and the ID of the NO lumen may range from 0.01
to 0.08''. In some embodiments, the IDs of the oxygen lumen and the
trigger lumen may both be in the range from 0.07'' to 0.09'' (such
as about 0.08'') and the ID of the NO lumen may be in the range
from 0.035 to 0.055'' (such as about 0.045'').
[0080] An alternate embodiment shown in FIG. 19 involves ensuring
that the small NO lumen exits proximal to and within the larger
trigger lumen. This embodiment ensures that any tip blockage of the
larger trigger lumen (for which there is not a purge capability)
would be blown out by the function of the NO pulse. The geometry of
this embodiment must be carefully modeled to ensure that all NO in
the larger trigger lumen reaches the respiratory system during
inspiration and is not left behind to be swept out during
exhalation.
Methods of Treatment
[0081] Any of the nasal cannulas described herein may be used in
nitric oxide therapy to treat appropriate diseases. For example,
the cannulas may be for pulsed NO therapy to treat chronic
obstructive pulmonary disease (COPD) or pulmonary arterial
hypertension (PAH). For these diseases, the delivery of the
appropriate dose amounts and appropriate dose timing may be very
important. For COPD, the NO may need to be pulsed early in
inspiration, such as the first half of inspiration. If NO is not
delivered in the right amount or at the right time, reversal of
hypoxic vasoconstriction may occur, which would worsen the
patient's condition. Furthermore, the dose amount may be very
important for PAH because sudden discontinuation of therapy can
lead to serious events such as rebound hypertension. Thus,
significant dilution of the NO dose should be minimized for these
diseases. Any of the cannula materials, configurations or methods
described herein may be used to minimize dilution of the NO dose
during NO therapy.
EXAMPLES
[0082] FIG. 8 shows an example of retrograde flow during
inspiratory breath along with pulsed delivery. FIG. 9 shows an
example of retrograde flow during both inspiratory and expiratory
breath.
[0083] The retrograde flow for various nasal cannula configurations
was tested. Typical nasal cannulas that deliver to both nares
result in significant retrograde flow as shown in Test 1 of FIG.
14. The nasal cannula configuration of Test 1 is shown in FIG. 15A.
For Test 2, the interconnect between the two prongs was occluded to
increase the distance between the prongs to approximately 19 inches
in the hopes that would eliminate the retrograde flow. The nasal
cannula configuration of Test 2 is shown in FIG. 15B. As shown in
Test 2 of FIG. 14, while the total volume of retrograde flow could
be reduced, it was not eliminated. Further occluding the pathway
with a 7 foot distance between the prongs, as shown in FIG. 15C,
had minimal further impact, as shown in Test 3 of FIG. 14.
Surprisingly, it was found that the only way tested that completely
eliminated the retrograde flow was when separate circuits were used
for the NO delivery to each nare.
[0084] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment"
means that a particular feature, structure, material, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the invention. Furthermore, the
particular features, structures, materials, or characteristics may
be combined in any suitable manner in one or more embodiments.
[0085] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It will be apparent to those
skilled in the art that various modifications and variations can be
made to the method and apparatus of the present invention without
departing from the spirit and scope of the invention. Thus, it is
intended that the present invention include modifications and
variations that are within the scope of the appended claims and
their equivalents.
* * * * *