U.S. patent application number 11/596027 was filed with the patent office on 2008-02-07 for intermittent dosing of nitric oxide gas.
Invention is credited to Bevin B. McMullin, Chris Miller, Alex Stenzler.
Application Number | 20080029093 11/596027 |
Document ID | / |
Family ID | 35394664 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080029093 |
Kind Code |
A1 |
Stenzler; Alex ; et
al. |
February 7, 2008 |
Intermittent Dosing Of Nitric Oxide Gas
Abstract
A method and corresponding device are described for combating
microbes and infections by delivering intermittent high doses of
nitric oxide to a mammal for a period of time and which cycles
between high and low concentration of nitric oxide gas. The high
concentration of nitric oxide is preferably delivered
intermittently for brief periods of time that are interspersed with
periods of time with either no nitric oxide delivery or lower
concentrations of nitric oxide. The method is advantageous because
at higher concentration, nitric oxide gas overwhelms the defense
mechanism of pathogens that use the mammalian body to replenish
their thiol defense system. A lower dose or concentration of nitric
oxide gas delivered in between the bursts of high concentration
nitric oxide maintains nitrosative stress pressure on the pathogens
and also reduces the risk of toxicity of nitric oxide gas.
Inventors: |
Stenzler; Alex; (Long Beach,
CA) ; Miller; Chris; (North Vancouver, CA) ;
McMullin; Bevin B.; (Surrey, CA) |
Correspondence
Address: |
SIDLEY AUSTIN BROWN & WOOD LLP (LAIP GROUP)
555 W. FIFTH ST., SUITE 4000
LOS ANGELES
CA
90013
US
|
Family ID: |
35394664 |
Appl. No.: |
11/596027 |
Filed: |
May 11, 2005 |
PCT Filed: |
May 11, 2005 |
PCT NO: |
PCT/US05/16427 |
371 Date: |
November 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60570429 |
May 11, 2004 |
|
|
|
Current U.S.
Class: |
128/203.25 ;
128/203.12; 424/718 |
Current CPC
Class: |
A61M 16/0833 20140204;
A61M 2016/003 20130101; A61M 2016/102 20130101; A61M 16/0666
20130101; A61H 33/14 20130101; A61M 2205/3327 20130101; A61M
2202/0275 20130101; A61P 31/04 20180101; A61M 2205/3334 20130101;
A61M 16/122 20140204; A61M 16/202 20140204; A61M 16/12 20130101;
A61M 16/024 20170801; A61M 16/204 20140204; A61M 16/201 20140204;
A61P 31/10 20180101; A61K 33/00 20130101; A61M 16/04 20130101; A61M
16/0003 20140204; A61P 31/12 20180101 |
Class at
Publication: |
128/203.25 ;
128/203.12; 424/718 |
International
Class: |
A61K 33/08 20060101
A61K033/08; A61M 15/00 20060101 A61M015/00 |
Claims
1. A method of delivering nitric oxide to a mammal, the method
comprising the steps of: providing a source of nitric oxide gas;
diluting the nitric oxide gas; alternately administering, for a
number of cycles, the nitric oxide gas to the mammal at a first
concentration ranging from about 80 ppm to about 400 ppm of nitric
oxide gas for a first period of time and at a second concentration
of nitric oxide gas lower than the first concentration for a second
period of time.
2. The method of claim 1 wherein the second period of time is
longer than the first period of time.
3. The method of claim 1 wherein the first concentration of nitric
oxide gas ranges from about 160 ppm to about 300 ppm.
4. The method of claim 1 wherein the second concentration of nitric
oxide ranges from about 20 ppm to about 40 ppm.
5. The method of claim 1 wherein the first period of time is about
30 minutes and the second period of time is about 3.5 hours.
6. The method of claim 1 wherein the step of administering is
through inhalation of the nitric oxide gas.
7. The method of claim 1 wherein the step of administering is
topical application of the nitric oxide gas.
8. A method of delivering nitric oxide to mammal, the method
comprising the step of administering to a mammal a first
concentration of nitric oxide gas for a number of time periods that
are interspersed with intervals in between wherein a second
concentration of nitric oxide is administered during the
intervals.
9. The method of claim 8 wherein the second concentration of nitric
oxide gas is lower than the first concentration of nitric oxide
gas.
10. The method of claim 9 wherein the second concentration of
nitric oxide gas is less than about 80 ppm.
11. The method of claim 8 wherein the first concentration of nitric
oxide gas is at a concentration sufficient to kill or inhibit the
growth of microbes.
12. The method of claim 11 wherein the microbes are selected from a
group consisting of bacteria, mycobacteria, viruses and fungi.
13. The method of claim 8 wherein the step of administration is
through inhalation of the nitric oxide gas.
14. The method of claim 8 wherein the step of administering is
topical application of the nitric oxide gas.
15. A device for delivery nitric oxide gas comprising: a source of
nitric oxide gas; a source of diluent gas; a delivery interface
adaptable for delivery of the nitric oxide gas from the source to a
mammal; a gas mixer for mixing the nitric oxide gas with the
diluent gas; a controller that communicates with the gas mixer
wherein the controller comprises logic for setting a nitric oxide
delivery profile comprising at least two different concentrations
of nitric oxide gas and for automatically switching between the at
least two different concentrations of nitric oxide gas on a timed
basis.
16. The device of claim 15 wherein the delivery profile further
comprises at least a first and a second time period corresponding
respectively to each of the at least two different concentration of
nitric oxide gas.
17. The device of claim 16 wherein the first time period is shorter
than the second time period.
18. The device of claim 15 wherein the gas mixer comprises a T or Y
shaped tubing connection and a flow control valve.
19. The device of claim 15 wherein the gas mixer comprises a gas
blender.
20. The device of claim 15 wherein the delivery interface comprises
a bathing unit for topical delivery of nitric oxide gas to a
surface of the body.
21. The device of claim 15 wherein the delivery interface comprises
an interface selected from a group consisting of facial mask, nasal
insert, and endotracheal tube.
22. The device of claim 15 further comprising a nitric oxide gas
analyzer for measuring the concentration of nitric oxide gas
flowing to the delivery interface, wherein the nitric oxide gas
analyzer sends signals to the controller.
23. A device for delivery nitric oxide gas comprising: a source of
nitric oxide gas at a first concentration; a source of breathable
gas; a delivery interface adaptable for delivery of the nitric
oxide gas from the source to a mammal; a switch valve downstream of
the source of nitric oxide gas and upstream of the delivery
interface, said switch valve for directing the flow of nitric oxide
gas from the source to the delivery interface; a controller
controlling the switch valve and which commands the switch valve to
switch between the source of nitric oxide gas and the source of
breathable gas on a timed basis.
24. The delivery device of claim 23 wherein the source of
breathable gas comprises nitric oxide gas at a concentration lower
than the first concentration of nitric oxide gas.
Description
FIELD OF THE INVENTION
[0001] The field of the present invention relates to methods and
devices for delivery of exogenous or gaseous nitric oxide gas to
mammals.
BACKGROUND OF THE INVENTION
[0002] NO is an environmental pollutant produced as a byproduct of
combustion. At extremely high concentrations (generally at or above
1000 ppm), NO is toxic. NO also is a naturally occurring gas that
is produced by the endothelium tissue of the respiratory system. In
the 1980's, it was discovered by researchers that the endothelium
tissue of the human body produced NO, and that NO is an endogenous
vasodilator, namely, an agent that widens the internal diameter of
blood vessels.
[0003] With this discovery, numerous researchers have investigated
the use of low concentrations of exogenously inhaled NO to treat
various pulmonary diseases in human patients. See e.g., Higenbottam
et al., Am. Rev. Resp. Dis. Suppl. 137:107, 1988. It was
determined, for example, that primary pulmonary hypertension (PPH)
can be treated by inhalation of low concentrations of NO. With
respect to pulmonary hypertension, inhaled NO has been found to
decrease pulmonary artery pressure (PAP) as well as pulmonary
vascular resistance (PVR). The use of inhaled NO for PPH patients
was followed by the use of inhaled NO for other respiratory
diseases. For example, NO has been investigated for the treatment
of patients with increased airway resistance as a result of
emphysema, chronic bronchitis, asthma, adult respiratory distress
syndrome (ARDS), and chronic obstructive pulmonary disease, (COPD).
In 1999, the FDA approved the marketing of nitric oxide gas for use
with persistent pulmonary hypertension in term and near term
newborns. Because the withdrawal of inhaled nitric oxide from the
breathing gas of patients with pulmonary hypertension is known to
cause a severe and dangerous increase in PVR, referred to as a
"rebound effect", nitric oxide must be delivered to these patients
on a continuous basis.
[0004] In addition to its effects on pulmonary vasculature, NO may
also be introduced as a anti-microbial agent against pathogens via
inhalation or by topical application. See e.g., WO 00/30659, U.S.
Pat. No. 6,432,077, which are hereby incorporate by reference in
their entirety. The application of gaseous nitric oxide to inhibit
or kill pathogens is thought to be beneficial given the rise of
numerous antibiotic resistant bacteria. For example, patients with
pneumonia or tuberculosis may not respond to antibiotics given the
rise of antibiotic resistant strains associated with these
conditions.
[0005] Clinical use of nitric oxide for inhalation has
conventionally been limited to low concentration of nitric oxide
given the potential toxicity. The toxicity may stem from binding of
nitric oxide to hemoglobin that give rise methemoglobin or from the
conversion of nitric oxide gas to nitrogen dioxide (NO.sub.2).
However, to overwhelm pathogenic defense mechanisms to nitric
oxide, it is desirable to deliver nitric oxide at a higher
concentration (e.g., between 150 ppm to 250 ppm, and even to 400
ppm) than has traditionally been used clinically for inhalation.
Thus, a need exists for a delivery method that is effective against
combating pathogens and minimizing the risk of toxicity.
SUMMARY OF THE INVENTION
[0006] It is envisioned that a method and device delivering
intermittent high doses of nitric oxide for a period of time and
which cycles between high and low concentration of nitric oxide is
desirable, useful, and overcomes the problems of toxicity. The high
concentration of nitric oxide is preferably delivered
intermittently for brief periods of time that are interspersed with
periods of time with either no nitric oxide delivery or lower
concentrations of nitric oxide. This keeps the exposure to the high
concentrations of nitric oxide required to overwhelm the nitric
oxide defense mechanisms of the pathogens to an average level that
is safe for humans to inhale.
[0007] In a preferred embodiment, high concentration of nitric
oxide may be delivered at a concentration between 80 ppm to 300
ppm, preferably between 150 ppm to 250 ppm, and more preferably
between 160 ppm to 200 ppm. Low concentration of nitric oxide
preferably is delivered at a concentration between zero (0) ppm to
80 ppm, and preferably at a concentration of 20 ppm to 40 ppm.
[0008] The time periods may vary and in a wide range that
preferably will deliver a dose of x time of 600 to 1000 ppmhrs per
day. For example, the method would deliver 160 ppm for 30 minutes
every four hours with 20 ppm delivered for the 3.5 hours between
the higher concentration delivery. High concentration may also be
delivered for a period of time between 10 minutes to 45 minutes,
and the low concentration is preferably delivered for a period of
time longer than the period of time in which the high concentration
is delivered. However, it may also be delivered for the same length
of time as the high concentration of nitric oxide with less number
of cycles to achieve substantially the same amount of ppmhrs of
nitric oxide per day. Thus, the high and low concentrations are
alternately delivered, and the cycling of the delivery can be for a
day, two days, three days, or any other time prescribed by a
physician.
[0009] Devices for the delivery of nitric oxide are commercially
available and may include continuous flow devices, flow matching
devices, or pulse dose devices. For example, the FDA has already
approved three different nitric oxide delivery systems in the
United States: AeroNOx.RTM. Delivery System and the ViaNOx DS
System (Pulmonox, Canada) and the INOvent.RTM. Delivery System
(Datex-Ohmeda, Wis.). Other devices have also been described in
literature and various publications and patents (e.g., U.S. Pat.
No. 6,581,599, which is incorporated here by reference in its
entirety).
[0010] In another aspect to the invention, the device for use to
deliver intermittent high doses of nitric oxide may include a
source of nitric oxide gas (e.g., nitric oxide gas in compressed
gas cylinders), controller (e.g. an electronic controller or
microprocessor), nitric oxide analyzer, and timer in which the
concentration of nitric oxide delivered is automatically changed on
a timed basis to a concentration set by the operator and for a set
period of time defined by the operator. The device would include
logic (e.g. software or firmware) that allows for setting of two
different nitric oxide concentrations and with separate time
settings for the delivery of each concentration. The device may
also include gas mixers (such as gas blenders or combinations of
flow control valves and T or Y shaped tube connections), tubings, a
source of diluent gas (e.g. room air, oxygen, or inert gas), and
electronically regulated needle valves or other valve mechanism for
controlling the release of nitric oxide gas, or the diluent gas, or
both.
[0011] Alternatively, the device may also include two sources of
nitric oxide gas, in which one source provides the high
concentration of nitric oxide and the other source provides the low
concentration of nitric oxide. A switch valve (preferably
electronically controlled) is then provided to switch the flow of
nitric oxide gas from the high concentration to the low
concentration, or vice versa, based on a predefined time. A third
source of diluent gas may also be provided to dilute the nitric
oxide gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1-3 illustrate schematic representations of various
embodiments of a nitric oxide delivery device according to one
aspect of the present invention.
[0013] FIG. 4 illustrates the logic for setting the alternating
delivery profile for high and low concentrations of nitric oxide
gas.
[0014] FIG. 5 illustrates the logic for delivering alternating high
and low concentrations of nitric oxide gas.
[0015] FIG. 6 shows the effect on survival of S. aureus (ATCC#
25923) when alternately exposed to NO gas (gNO) exposure at 160 ppm
nitric oxide gas for 30 minutes and 20 ppm for 3.5 hours for a
total exposure time of 24 hours.
[0016] FIG. 7 shows the effect on survival of P. aeruginosa (ATCC#
27853) when alternately exposed to NO gas (gNO) exposure at 160 ppm
nitric oxide gas for 30 minutes and 20 ppm for 3.5 hours for a
total exposure time of 24 hours.
[0017] FIG. 8 shows the effect on survival of P. aeruginosa
(clinical strain from Cystic Fibrosis) when alternately exposed to
NO gas (gNO) exposure at 160 ppm nitric oxide gas for 30 minutes
and 20 ppm for 3.5 hours for a total exposure time of 24 hours.
[0018] FIG. 9 shows the effect on survival of E. coli when
alternately exposed to NO gas (gNO) at 160 ppm nitric oxide gas for
30 minutes and 20 ppm for 3.5 hours for a total exposure time of 24
hours.
[0019] FIG. 10 shows the effect on survival of a MshA mycothiol
deficient mutant Mycobacterium smegmatis and its wild type
counterpart when exposed to 200 ppm NO gas (gNO).
[0020] FIG. 11 shows the level of mycothiol in wild type
Mycobacterium smegmatis when exposed to 400 ppm NO gas (gNO)
compared to exposure to air.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] It is currently believed that at higher concentration,
nitric oxide gas overwhelms the defense mechanism of pathogens that
use the mammalian body to replenish their thiol defense system. The
thiol defense system may include for example, the mycothiol for
mycobacterium or glutathione for other bacteria. Once this defense
mechanism is depleted, the pathogen is defenseless against the
killing effects of nitric oxide. A lower dose or concentration of
nitric oxide gas delivered in between the bursts of high
concentration nitric oxide maintains nitrosative stress pressure on
the pathogens to prevent them from rebuilding their defense system
to an adequate level. Thus, a preferred therapeutic or delivery
profile for combating pathogens may comprise the delivery of a
first concentration of nitric oxide gas for a number of time
periods interspersed with intervals in between wherein a second
concentration of nitric oxide is administered during the intervals.
The first concentration is preferably at a high concentration
sufficient to kill or inhibit microbial growth. For example, the
first concentration may range from about 80 ppm to 400 ppm, more
preferably between 150 to 250 ppm and most preferably between 160
ppm to 200 ppm.
[0022] The second concentration is preferably at low concentration
of nitric oxide gas such as ranging from 20 to 80 ppm.
Alternatively, it should also be understood that the second
concentration can also be zero ppm or close to trace amount of
nitric oxide gas.
[0023] Turning now to the figures, FIGS. 1-3 illustrate various
embodiments of a nitric oxide delivery device for use with the
present invention. FIG. 1 shows, in its most general sense, a NO
delivery device 2 that includes a source of nitric oxide gas 8
adapted for delivery of the NO gas to a mammal through a delivery
interface 6. FIG. 1 illustrates one preferred embodiment of the
invention.
[0024] In FIG. 1, the NO gas source 8 is a pressurized cylinder
containing NO gas. While the use of a pressurized cylinder is the
preferred method of storing the NO-containing gas source 8, other
storage and delivery means, such as a dedicated feed line (wall
supply) can also be used. Typically, the NO gas source 8 is a
mixture of N.sub.2 and NO. While N.sub.2 is typically used to
dilute the concentration of NO within the pressurized cylinder, any
inert gas can also be used. When the NO gas source 8 is stored in a
pressurized cylinder, it is preferable that the concentration of NO
in the pressurized cylinder fall within the range of about 800 ppm
to about 10,000 ppm. Commercial nitric oxide manufacturers
typically produce nitric oxide mixtures for medical use at around
the 1000 ppm range. Pressurized cylinders containing low
concentrations of NO (e.g., less than 100 ppm NO) can also be used
in accordance with the device and method disclosed herein. Of
course, the lower the concentration of NO used, the more often the
pressurized cylinders will need replacement.
[0025] FIG. 1 also shows a source of diluent gas 14 as part of the
NO delivery device 2 that is used to dilute the concentration of
NO. The source of diluent gas 14 can contain N.sub.2, O.sub.2, Air,
an inert gas, or a mixture of these gases. It is preferable to use
a gas such as N.sub.2 or an inert gas to dilute the NO
concentration at lower concentration since these gases will not
oxidize the NO into NO.sub.2 as would O.sub.2 or air. Nevertheless,
for inhalation applications for delivery of high concentration of
NO where higher concentration of nitrogen may already be present,
the NO flow may be supplemented or diluted with oxygen to prevent
the displacement of oxygen by nitrogen that may lead to
asphyxiation. It is preferred, especially when delivering higher
concentration of NO gas that delivery line downstream of the
injection site or gas blender be minimized to reduce the risk of
formation of NO.sub.2.
[0026] The source of diluent gas 14 is shown as being stored within
a pressurized cylinder. While the use of a pressurized cylinder is
shown in FIG. 1 as the means for storing the source of diluent gas
14, other storage and delivery means, such as a dedicated feed line
(wall supply) can also be used. The source of diluent gas can also
be a ventilator, air pump, blower, or other mechanical device that
moves breathable air.
[0027] The NO gas from the NO gas source 8 and the diluent gas from
the diluent gas source 14 preferably pass through pressure
regulators 16 to reduce the pressure of gas that is admitted to the
NO delivery device 2. The respective gas streams pass via tubing 18
to a gas blender 20. The gas blender 20 mixes the NO gas and the
diluent gas to produce a NO-containing gas that has a reduced
concentration of NO compared to NO gas contained in the source 8.
Preferably, a controller 36 controls the gas blender through
electrical connection line 42 such that gas blender can be set to
mix the gases to the desired NO concentration (e.g., 160 ppm-200
ppm for the high concentration period, and 20-40 ppm for the low
concentration period) and output via tubing 24.
[0028] An optional flow control valve 22 can be located downstream
of the gas blender 20 to control the flow of the NO gas to the
delivery interface 6. The flow control valve 22 can include, for
example, a proportional control valve that opens (or closes) in a
progressively increasing (or decreasing if closing) manner. As
another example, the flow control valve 22 can include a mass flow
controller. The flow control valve 22 controls the flow rate of the
NO-containing gas that is input to the delivery device 6.
[0029] The delivery interface 6 can be any type of interface
adaptable for delivery of the gas to a mammal. For example, if the
NO gas is to be delivered to the mammal's airways or lungs, the
delivery interface 6 may include a facial mask, nasal insert, or
endotracheal tube that interface with the mammal's respiratory
system. It should be understood that the types of delivery
interface 6 should not be limiting and depends on the specific
applications and locations for the delivery of the gas. In another
example, if the NO gas is to be delivered topically to a surface of
the body such as a skin or eye, a surface of an organ such heart,
stomach, etc., a bathing unit as described in U.S. Pat. No.
6,432,077, issued to one of the inventors may be used. U.S. Pat.
No. 6,432,077 is hereby incorporated by reference as if fully set
forth herein. Still further example of a delivery interface 6 may
an interface to a dialysis circuit or extracorporeal circuitry
wherein the NO gas is delivered directly to the blood or body
fluids so as to expose the blood or body fluids to NO gas. Such
delivery interface are described, for example, in U.S. patent
application Ser. No. 10/658,665, filed on Sep. 9, 2003, which is
hereby incorporated by reference in its entirety.
[0030] Still referring to FIG. 1, the delivery device 2 preferably
includes a controller 36 that is capable of controlling the flow
control valve 22 and the gas blender 20. The controller 36 is
preferably a microprocessor-based controller 36 that is connected
to an input device (not shown). The input device may be used by an
operator to adjust various parameters of the delivery device such
as NO concentration and therapy/exposure time periods. An optional
display can also be connected with the controller 36 to display
measured parameters and settings such as the set-point NO
concentration, the concentration of NO flowing to the delivery
interface 6, the concentration of NO.sub.2, the flow rate of gas
into the delivery interface 6, the total time of therapy/delivery,
and/or the number of cycles for alternating between high and low
concentrations of NO gas.
[0031] The controller preferably includes a timer for counting down
the time periods of the NO gas delivery at the different
concentrations. Moreover, the controller preferably includes logic
such as firmware or software programs for executing the alternate
delivery of high and low concentration of NO gas at pre-set or user
programmable time periods. The processes for execution by such
logic are illustrated in FIGS. 4 and 5.
[0032] The controller 36 also preferably receives signals through
signal line 48 from NO analyzer 40 regarding gas concentrations if
such analyzer 40 are present within the delivery device 2. Signal
lines 42 and 44 are connected to the gas blender 20 and flow
control valve 22 respectively for the delivery and receipt of
control signals.
[0033] In another embodiment of the nitric oxide delivery device,
the controller 36 may be eliminated entirely and the gas blender 20
may be set manually at the desired high or low concentration of
nitric oxide gas. The time period may also be tracked manually and
at the appropriate set time period, the gas blender is adjusted to
either increase to the high concentration NO gas or decrease to the
low concentration NO gas. The flow rate of the gas into the
delivery interface 6 may be pre-set or adjusted manually.
[0034] FIG. 2 shows an alternative embodiment of a nitric oxide
delivery device 52 in which the desired concentration of NO gas is
achieved by mixing with a T or Y shaped connection 70 based on the
flow rates of the NO gas flowing from the NO gas source 8 and the
diluent gas flowing from the diluent gas source 74. The respective
flow rates are controlled via the flow control valves 72 and 75.
Mixing of the gases starts at the T or Y shaped connection point 70
and continues through the delivery line 78. An NO analyzer 80
samples the gas mixture at a juncture close to the delivery
interface to determine the NO concentration of the gas mixture
flowing to the delivery interface 76. The measured NO concentration
is then fed back through signal line 88 to the controller 86, which
in turn processes the information by comparing the measured NO
concentration with the set desired NO gas concentration. The
controller 86 then adjusts the flow control valves 72 and 75, if
appropriate, by sending control signals through lines 82 and 84
such that the flow rate(s) may be adjusted in order to achieve the
desired concentration of NO gas flowing to the delivery interface
76. It should be understood that the controller 86 may similarly
include all the features discussed above in connection with
controller 36 in FIG. 1. Likewise, the delivery interface 76 may be
adapted similarly to the delivery interface 6, as described in
connection with FIG. 1.
[0035] FIG. 3 illustrates yet another embodiment of a nitric oxide
delivery device in accordance to one aspect of the present
invention. In this delivery device 102, instead of having gas
mixers (e.g., gas blender or T or Y-shaped connection), the
delivery device 102 utilizes a switch valve 104 to switch between a
high concentration NO gas source 106 and a low concentration NO gas
source 108. The switch valve 104 is controlled by the controller
116 that at the appropriate time switches between the high and low
concentration of NO gas according to the present invention. It
should be understood that the low concentration NO gas source 108
can also be replaced with non-NO gas source such as air, if the
desired period of low NO concentration is zero ppm of NO gas.
[0036] Referring now to FIGS. 4 and 5, process flows are
exemplified that may be executed by logic (firmware or software)
programmed into the controllers 36, 86, and 116. FIG. 4 illustrates
a process flow for setting up the desired concentrations and time
periods for NO gas delivery starting from Step 400 "START." At Step
405, the logic enters the setup subroutine for setting the desired
NO concentrations and time periods. At Step 410, the logic verifies
if there are concentration values set for the NO delivery profile.
If values are already set, then the process proceeds to Step 415 to
verify the values set for the time periods of delivery. If no
values have yet been set for the NO concentrations, then the logic
calls a subprocess comprising of steps 412 and 414 is called to set
the 1.sup.st and 2.sup.nd NO concentration for the therapeutic
profile to be delivered. For example, the 1.sup.st NO concentration
may be set for about 160 ppm to 300 ppm of NO gas to be delivered
and the 2.sup.nd concentration may be set for 0 ppm to 80 ppm of NO
gas to be delivered. The values of the NO concentrations set are
then used by the controller to set the gas blender or the flow
control valves in the process illustrated in FIG. 5.
[0037] After the values of NO concentrations have been set, the
logic then proceeds to set the time periods for the delivery of the
NO gas in Step 415. If the time periods have not yet been set, then
a subprocess comprising steps 417 and 149 is called in which a
first time period corresponding to the 1.sup.st NO concentration
and a 2.sup.nd time period corresponding to the NO concentration
are set.
[0038] After the values of NO concentrations and the time periods
have been set, the logic then proceeds to set the number of cycles
of alternating 1.sup.st and 2.sup.nd concentration of NO gas to be
delivered. Alternatively, a total therapy time can be set in which
the delivery of NO gas will cease at the end of the total therapy
time. If the total therapy time or number of cycles have not been
set, then a subprocess comprising of step 422 is called and these
values are set. Afterwards, the setup process is ended and the
device is ready to deliver NO gas for therapy.
[0039] FIG. 5 illustrates a process flow for execution by the logic
in controller 36, 56, and 116, for the alternating delivery of high
and low concentration of NO gas. The START THERAPY in step 500 can
be started once the NO gas delivery values in FIG. 4 has been
entered. At Step 505, the controller 36 (FIG. 1) may then send a
control signal through line 42 to the gas blender to set the
appropriate gas blender settings to achieve the 1.sup.st
concentration of NO gas, the value of which was set in the setup
process of FIG. 4. This process may also include feedback control
from the NO analyzer 40 (FIG. 1) to the controller 36 such that the
control of the gas blender may be fine tuned in that the actual NO
gas concentration being delivered to the delivery interface 6
matches the set NO gas concentration.
[0040] Alternatively, the controller at Step 505 may send control
signals to the flow control valves 72 and 75 (FIG. 2) to set the
appropriate flow rates for the mixing of the gases to achieve the
1.sup.st concentration set in the setup process of FIG. 4. This
process may similarly include feedback control from the NO analyzer
80 (FIG. 2) to the controller 56. In yet another embodiment, the
controller at Step 505 may set the switch valve 104 (FIG. 3) to
select for delivery the NO gas from a source corresponding to the
1.sup.st concentration of NO gas set in the setup process of FIG.
4.
[0041] Delivery of NO gas proceeds in accordance with the settings
in Step 505. At step 510, the timer comprised in the controller 36,
56, or 116 compares the value of the 1.sup.st time period set in
FIG. 4 with the actual countdown in time. If the time period has
not elapsed, then the gas blender, flow control valves, or switch
valve settings remain the same in Step 512. If the 1.sup.st time
period has elapsed, then step 515 sets the gas blender, flow rates,
or switch valve settings to that corresponding to the 2.sup.nd
concentration of NO gas, the value of which was set in the process
of FIG. 4. Delivery of NO gas then proceeds on the 2.sup.nd
concentration until the 2.sup.nd time period elapsed.
[0042] At the completion of the second time period, the logic
proceeds to step 525 inquiring into whether the set number of
cycles of total therapy time has elapsed. If the set number of
cycles or total therapy time has been reached, the therapy ends in
Step 530. Otherwise, the process repeats steps 505, 510, 515, and
525.
Further Examples of Delivery Methods
[0043] The implementation of the intermittent delivery of high
doses of NO gas can be by many means. For example, delivery by
inhalation or to the respiratory airway can be made to
spontaneously breathing mammals or those managed with mechanical
ventilation. With respect to spontaneously breathing mammals,
delivery can be achieved via many of previously described gas
delivery systems such as masks or nasal cannulas. The device for
these mammals may include flowmeter or flow sensor to detect the
onset of breathing (e.g., inhalation vs. exhalation) such that the
nitric oxide gas would be delivered only when the mammal inhales.
Mechanically ventilated mammals would have the nitric oxide
delivered into the inspiratory limb of the ventilator circuit and
may similarly be triggered only when the ventilator cycled a breath
into the mammal.
[0044] In both of these implementations, the pattern of nitric
oxide delivery may vary depending on the targeted location of the
infection within the mammal's lungs and the desire to have the
least concentration of nitric oxide residual in the delivery
circuit. For example, if the infection were in the air sacs of the
lungs, the nitric oxide could be turned off towards the end of the
breath when the gas was going to be delivered only to the airways.
As an alternative, if the infection were only in the airways, then
the starting gas might have a lower concentration of nitric
oxide.
[0045] Furthermore, it is preferred that the injection site for NO
gas delivery be close to the patient's airway when using higher
concentrations of NO gas so as to reduce the time for conversion to
NO.sub.2. This minimizes the dwell time of the NO gas in the
delivery line before inhalation. Alternatively, the delivery system
may utilize a bolus injection of a high concentration at a time
point within the breath and allow the dilution of the NO to occur
within the lungs.
[0046] While embodiments of the present invention have been shown
and described, various modifications may be made without departing
from the scope of the invention. The invention, therefore, should
not be limited, except to the following claims, and their
equivalents.
Experimental Results
[0047] The effectiveness of the intermittent high dose delivery of
nitric oxide gas in combating microorganisms was tested and
verified. Briefly, the experimental methods were as follows.
Inoculums of varying bacteria was prepared to a suspension of
2.5.times.10.sup.8 cfu/ml, and diluted 1:1000 in sterile normal
saline. Three milliliters of the inoculums were used per well in a
sterile culture place. Exposure of the inoculums were performed in
an exposure chamber, which has been described for example, in
Ghafarri, A. et al., "A direct nitric oxide gas delivery system for
bacterial and mammalian cell cultures," Nitric Oxide. 12(3):129-40
(May 2005), which is hereby incorporated by reference as if fully
set forth herein. The inoculums were exposed to 160 ppm of NO gas
at a flow rate of 2.5 liters per minute for 30 minutes followed by
exposure to 20 ppm of NO gas for 3.5 hours. The exposure to high
and low concentrations of NO gas was repeatedly cycled every 4
hours for 24 hours. At various times (e.g., 0, 4, 8, and 12 hours),
samples were taken and plated to determine the survivability of the
bacteria as determined by counting cfu/ml.
[0048] FIGS. 6-9 show the survival of various bacteria used in the
experiment with NO gas compared to exposure to air as control. As
seen in these figures, cycling exposure to high and low
concentrations of nitric oxide is an effective method of killing
the bacteria. While it was observed that the effectiveness of
cycling exposure to high and low concentrations over a longer
period of time, was similar to that of continuous exposure to high
concentration, cycling exposure provides a better safety profile in
minimizing the risk of methemoglobin formation.
[0049] Additional studies were performed to test the hypothesis
that the effect of NO gas in killing microorganisms is related to
thiol function. Based on studies with various microorganisms, it
was observed that Mycobacteria are less sensitive to NO gas damage.
This may be due to Mycobacteria having an exceptional thiol,
mycothiol, that maintains the redox balance in the cell and
protects the cell from nitrosative and oxidative stress. In order
to test this hypothesis, sensitivities to NO gas was compared
between mycothiol-deficient Mycobacterium smegmatis Mutant MshA to
its wild type counterpart, mc.sup.2155 by exposing both strains to
200 ppm of NO gas. MshA is an enzyme needed in mycothiol
biosynthesis.
[0050] FIG. 10 shows that the mycothiol-deficient MshA mutant was
more sensitive to NO gas than its wild type counterpart and was
killed in less time than its wild type counterpart.
[0051] Further experiments were conducted to assay and measure the
mycothiol level using HPLC in wild type M. smegmatis after exposure
to 400 ppm NO gas and were compared to mycothiol level after
exposure to air. FIG. 11 shows that upon exposure to 400 ppm of NO
gas, the level of mycothiol in the mycobacterium was reduced
compared to exposure to air.
[0052] Thus, these results show the NO gas may likely act to
deplete mycothiol, which is the mechanism by which the
mycobacterium protects itself against oxidative stress.
[0053] In other bacteria, it is believed that the analogous
molecule to mycothiol in mycobacteria is glutathione. The
glutathione pool may normally act to protect the bacteria from
endogenous NO and H.sub.2O.sub.2, which are released by macrophages
against pathogens. Delivery of exogenous NO gas may thus act to
overwhelm the glutathione pool, eliminating bacterial protection
from H.sub.2O.sub.2, and binding iron based enzymes causing O.sub.2
consumption cessation and electron transport center disruption and
freeing metal ions into the bacterial cytosol. The free oxygen,
metal ions, NO, and hydrogen peroxide further produce reactive
nitrogen and oxygen species as well as metal ions that damage the
bacteria's DNA by deamination. Thus, it is believed that cycling or
alternating delivery of concentration of NO gas sufficient to
overwhelm the glutathione defense mechanism for a period of time
and a lower concentration of NO gas may be effective in combating
microbes such as bacteria, mycobacteria, and fungi while at the
same time exhibit a better safety profile.
[0054] Microbes may also include viruses. While viruses do not by
themselves have thiol based detoxification pathways, they may still
be inherently more susceptible to nitrosative stress. NO may
inhibit viral ribonucleotide reductase, a necessary constituent
enzyme of viral DNA synthesis and therefore inhibit viral
replication. Nitric oxide may also inhibit the replication of
viruses early during the replication cycle, involving the synthesis
of vRNA and mRNA encoding viral proteins. With viruses also
depending on host cells for detoxification of the body's defense
pathways, the direct cytotoxic mechanisms of NO entering the host
cells and the intracellular changes it produces, could also account
for the viricidal effects through viral DNA deamination. Thus, it
is believed that the cycling or alternating delivery of NO gas at
high and low concentrations may also be effective against
viruses.
* * * * *