Note: Descriptions are shown in the official language in which they were submitted.
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TREATMENT OF CARBON MONOXIDE POISONING
FIELD OF THE INVENTION
This invention relates to a therapy for clearing the blood of unwanted carbon
monoxide and anaesthetic chemicals and for rapidly re-oxygenating that has had
it's oxygen
level depleted by environmental conditions i.e. carbon monoxide poisoning or
smoke
inhalation. The invention includes the means of delivering the therapy in a
convenient
manner whether given in-situ, in an ambulance or other emergency response
vehicle, or at the
hospital or other care facility, and whether administered by medical
professionals or
paramedical personnel. The device relates in general to pneumatic/mechanical
control of
respirator gas supply control devices and in particular to gas selection,
automatic shut off of
the carbon dioxide, purging, metering and mixing of the therapeutic gases.
BACKGROUND OF THE INVENTION
Carbon monoxide (CO) is a tasteless, colourless, odourless gas. Thus it is
undetectable by potential victims. The blood prefers CO to oxygen by a ratio
of 200:1. As a
result, relatively small amounts of CO in the air can cause CO poisoning. CO
attaches to
blood forming carboxyhemoglobin, thus starving the brain and other organs and
tissues for
oxygen (02). Carbon monoxide poisoning occurs when carboxyhemoglobin levels
are high
enough to impair cellular functions. Symptoms of carbon monoxide poisoning
include
drowsiness, nausea and possibly death. The CO poisoning rate is significant,
with over
70,000 hospital visits and 10,000 deaths per year in the U.S.
The cellular oxygen starvation from CO poisoning can cause death, or long-
term,
non-reversible health problems (i.e. to the brain, heart or neurological
system). If a CO
poisoning victim does not die, the average body will clear carboxyhemoglobin
at the
following typical rates:
Spontaneous breathing - cleansing half-life = 220 minutes; Breathing pure 02 =
40 minutes;
Hyperbaric chamber = 20 minutes.
While the best current therapy is placing the patient in a hyperbaric chamber,
these
chambers are usually unavailable (only about 700 exist world-wide) and are
rarely used.
Typically these chambers require a"warm-up" time of 2 hours, which largely
negates their
theoretical usefulness. That is, significant permanent damage may have already
occurred
before the treatment can be commenced.
The current therapy of choice is to administer pure 02. As suggested above,
pure 02
would require approximately 2 hours to clear 87.5% of the CO from the
bloodstream (e.g. 40
minutes = 50% of CO is eliminated; 80 minutes = 25%; 120 minutes = 12.5%).
Breathing
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pure 02 has an unfortunate side effect; it lowers the respiratory rate and
reduces the exchange
of gases in the lungs, thereby prolonging the tissue starvation period.
Accordingly, there is a
need for a device that would overcome these disadvantages.
Typical respirator gas supply control devices, particularly those used for
mixing gases
under pressure and feed a delivery line of a respirator, or medical device,
are too large and
bulky to be used in situ or in emergency vehicles. They also require the
operation of a skilled,
medical practitioner to properly administer. A complete system that can be
used by
emergency and paramedical should have a gas selection device, an automatic
shut off of the
carbon monoxide a purging system, metering of the gases and a mixing chamber
to promote a
homogeneous mixture of gases and sized for in-situ or vehicle as well as
hospital emergency
room use. It should be able to use a whole range of different gas storage
systems for input
and demand regulators and facemasks as output. It can not rely on electrical
control of the
gas flow and mixing as power demand for both in situ or emergency vehicle
applications is
already greater than is reasonable to expect. Also electrical power at fire
and other emergency
sites is problematical to provide and higher priority uses get first use of
this power. Finally
battery power is not acceptable as the system must operate every time demanded
regardless of
the interval between demand and maintenance of batteries is a low priority
item for
emergency care providers.
For example, US patent 3,441,041 allows for either atmospheric or compressed
air to
be used for a breathing apparatus but the mixture device is not easily
portable, and requires
adjustment by a trained individual when dealing with a patient to determine if
the by-pass
should be opened or closed and to adjust the compressed air flow based on
respiration
demands and the state of the patient's health.
US patent 4,535,797 discloses a device that uses flow to keep the by-pass open
and
the by-pass is required to open the gas flow valve for the first time. Should
the COZ supply
fail, the 02 supply will shut and the patient's therapy is terminated.
US patent 4,549,563 maintains a constant ratio between two gases, G1 and G2,
by
keeping the pressure of both gases P 1 and P2 constant and keeps P 1 constant
at a set rate of
flow through the use of a pressure limiter.
The device disclosed in US patent 4,549,563 does not provide for automatic
shut off
of the CO2 gas stream should the 02 stream become clogged. This shortcoming
would
expose the patient to an asphixyant and would not revert to the previously
accepted therapy.
In US patent 4,549,563 the practitioner operates the flush system described in
case
the patient requires pure 02 instead of the gas mixer. Such facemasks are
commercially
available and are not shown in the drawings. Also the system in 4,549,563 has
no means of
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purging, which would mean that the second patient would face an incorrect
mixture or if the
system selection was changed, for example from 02 to COZ then the patient
would have to
inhale the incorrect mixture prior to receiving the correct therapeutic gases.
US patent 4,313,436 mixes 02 and other medical gases for patients. It requires
electronic sensing to determine if the gas mixture is correct and if not then
causes a pressure
pulse to close the by-pass thereby allowing only pure 02 to enter the
facemask. The use of
electronics that have a large demand for power, i.e. 4 sensors and an
automatic controller, are
not feasible for in-situ on in vehicle use where power demand is already quite
high and the
most frequent operational problem is dead batteries due to limited maintenance
time. Also
this device has up to 5 separate valves that need to be adjusted by the
medical practitioner to
ensure the patient is receiving the proper gas mixture depending on his state.
This degree of
adjustment is inimical to the use by paramedical and emergency personnel. The
system in
4,313,4361acks a means of purging and only has two selection options, no
mixture or
mixture. Since there is no intermediary stage the operator is not prompted to
purge the
system.
US patent 4,827,965 uses a venturi nozzle to simultaneously meter and mix the
two
gases in proper proportions. This scheme means that pressure of the two gases
varies over the
flow demand regime and that the charge may be stratified. Finally the system
in 4,827,965
does not have a means to shut off the COZ mixture thus potentially exposing
the patient to an
asphixyant. Nor does it allow selection of different options (i.e. 02 only,
off , mix or off).
Nor does it offer a means of purging the system except by drawing off the
first amount of
improper mixture.
Under US patent 5,727,545, one embodiment requires electronic sensing of two
temperatures and a pressure to control the action of four flow regulators. In
a second
embodiment, it requires electronic sensing of two temperatures and a pressure
to control the
action of two flow regulators. The by-pass is driven electronically so that
any failure of the
electrical system would endanger the patient's life. Metering and mixing are
all electronic and
it has no purging means. The use of electronics that have a large demand for
power are not
feasible for in-situ on in vehicle use where power demand is already quite
high and the most
frequent operational problem is dead batteries due to limited maintenance
time.
US patent 4,508,143 discloses the use of a cam actuator to open a valve. It
opens two
poppet valves either automatically or manually. 4,508,143 has no other
features that could
deliver or control the therapeutic gas delivery.
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SUMMARY OF THE INVENTION
The invention provides a therapy clearing the blood of unwanted carbon
monoxide
and anaesthetic chemicals and for rapidly re-oxygenating that has had its
oxygen level
depleted by environmental conditions, i.e. carbon monoxide poisoning or smoke
inhalation.
The invention includes delivering the therapy in a convenient manner in situ,
in an ambulance
or other emergency response vehicle, or at the hospital or other care
facility. It may be
administered by medical professionals or paramedical personnel. The device
relates in general
to respirator gas supply control devices and in particular to gas selection,
automatic shut off of
the carbon monoxide, purging, metering and mixing of the therapeutic gases.
It is a great improvement on the current therapy, using pure 02, in that it is
more
rapidly clears carboxyhemoglobin from the patient's blood stream. Also it does
not lower the
respiratory rate or reduce the exchange of gases in the lungs, thereby
prolonging the tissue
starvation period. In fact the body's autonomous responses in the presence of
a CO2 rich
environment is to increase the rate of respiration (panting) thus further
decreasing the tissue
starvation period. While the method of invention and the use of a hyperbaric
chamber are
both effective, a hyperbaric chamber is impractical for in situ and vehicle
applications due to
their size, cost, long warm up time and requirement for trained medical
practitioner for
operation.
Cellular oxygen starvation from CO poisoning, or smoke inhalation, can cause
death,
or long-term, non-reversible health problems (i.e. to the brain, heart or
neurological system).
In the United States alone there are 70,000 hospital visits and 10,000 deaths
per year due to
CO poisoning. Thus a new therapy that radically improves the outcomes of
patients exposed
to CO poisoning is needed.
The invention also includes a device for delivering the improved therapy for
in situ,
in vehicles (i.e. ambulance or fire truck) and institutional (i.e. hospital)
locations. It avoids
the above-described shortcomings for example where the system requires
electric power to
properly operate, making it impractical for most emergency applications. It
avoids the
requirement for a trained medical practitioner to properly operate and adjust
the system while
monitoring the patient's state of health. It avoids the requirement to add
other required
functions to the system with external components.
The invention optionally includes all the functions required of an integrated
system:
selection of therapy; automatic shut-off of COZ; (i.e. automatic use of
current therapy pure 02)
or in case of 02 interruption automatic use of atmospheric air; precision
metering of both
gases; excellent mixing of both gases; and system purging. One embodiment
allows for the
use of the use of any 02 and COZ supply to accommodate institutional demands
(i.e.
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hospitals). The first embodiment includes a pneumatic control device. The
second
embodiment includes its own portable COz supply to allow use with existing
portable 02
supplies found in all emergency response vehicles. The second embodiment
contains all
items required for the therapy except the external 02 supply.
A cam actuator is used to select the choice of gas that the patient receives
and is a
four-position, rotary, manual switch. It can either be 02, off, 02 /C02, off.
The two
intermediary "off' positions allow for the patient to breathe atmospheric air
and are a
reminder to the operator to purge the system prior to moving to the next
selection position.
Should one of the source gas pressures become too low to maintain a proper
therapeutic gas mixture then the COZ flow would be halted by the shut-off
valve. A COZ shut-
off is operated by differential pressure between the 02 and the COz gas
mixture; failing a
proper supply of 02, the COZ shut-off closes so that only atmospheric air or
02 can be inhaled.
This is acceptable as the system reverts to the previously acceptable therapy.
In case of 02
flow interruption the CO2 flow stops and automatically the patient inhales
atmospheric air
through the facemask by-pass valve.
The pressure of one gas G 1 (02) maintains the flow of the other gas G2 (COZ),
since
P1 keeps the G2 flow passage open. Metering is done separately for each gas
and is
automatic and based on sonic flow of the gases, but accepts sub-sonic flow for
either or both
gases. Metering keeps the flow proportional regardless of outlet demand, and
mixing is done
in a separate chamber where the gas path maximises the chance of a homogeneous
mixture.
The invention relates to an apparatus and method for clearing the blood of
unwanted
carbon monoxide and/or anaesthetic chemicals and for rapidly re-oxygenating
that has had it's
oxygen level depleted, for example by environmental conditions i.e. carbon
monoxide
poisoning or smoke inhalation. The therapy includes respiration by the patient
of a mixture of
CO2 and 02. The apparatus for treating preferably involves administering to
the subject
oxygen from a source of oxygen and carbon dioxide from a source of carbon
dioxide,
comprises:
= an oxygen conduit defining an oxygen inlet and an oxygen outlet, the oxygen
inlet
adapted for fluid communication with the source of oxygen;
= a carbon dioxide conduit defining a carbon dioxide inlet and a carbon
dioxide outlet,
the carbon dioxide inlet adapted for fluid communication with the source of
carbon
dioxide;
= a means for combining the oxygen and the carbon dioxide, the means
downstream
from the oxygen outlet and the carbon dioxide outlet; and
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a means for administering the combined oxygen and carbon dioxide to the
subject.
The invention also includes a portable kit including the apparatus. The
invention also
includes a method for removing carbon monoxide and/or anaesthetic chemicals
from blood
and for rapidly re-oxygenating that has had it's oxygen level depleted,
including
administering to a subject an effective amount of combined oxygen and carbon
dioxide from
the apparatus. The invention also includes the use of the apparatus for
removing carbon
monoxide and/or anaesthetic chemicals from blood and for rapidly re-
oxygenating that has
had it's oxygen level depleted.
Oxygen and carbon dioxide therapy using the apparatus and methods of the
invention
can produce a clearing half-life of about 20 minutes.
The invention relates to an improved therapy for clearing the blood of
unwanted
carbon monoxide and anaesthetic chemicals and for rapidly re-oxygenating that
has had it's
oxygen level depleted by environmental conditions i.e. carbon monoxide
poisoning or smoke
inhalation. The therapy includes respiration by the patient of a mixture of
CO2 and 02. The
invention includes an apparatus and method for delivering the improved therapy
in a
convenient manner whether given in-situ, in an ambulance or other emergency
response
vehicle, or at the hospital or other care facility, and whether administered
by medical
professionals or paramedical personnel, and does not require the use of
electrical power. In
one embodiment, the apparatus acts as a pneumatic control device for the
therapeutic gas
mixture and where 02 and CO2 are stored. Preferably, pressure is regulated
externally, an
external buffer volume is stored externally and/or the demand regulator and
facemask are
connected to the equipment.
The invention also includes a method and apparatus fordelivering the improved
therapy, in the second embodiment, where all necessary functions are delivery
of the
therapeutic gas mixture is self-contained, with the sole exception of the 02
supply.
The invention also includes a control system, in the first embodiment, which
preferably includes: supplied gas shut-off valves; therapy selector switch;
automatic shut-off
valve for CO2 supply to avoid asphyxiating the patient; separate COZ and 02
metering valves;
a common gas mixing chamber; outlet ports to the buffer volume; outlet ports
to the demand
regulator/facemask; a means to purge the system and the buffer volume of
previous gas
mixtures prior to each new use. This system requires external connections to
pressurised CO2
and 02, a buffer volume and the demand regulator/facemask to operate.
The invention also includes a portable apparatus and method of delivering the
improved therapy, for emergency personnel and first aid care givers at the
emergency site, in
the second embodiment, which includes: pressure regulation of supplied 02; COZ
supply
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cylinder; pressure regulation of supplied C02; CO2 and 02 gas shut-off valves;
therapy
selector switch; automatic shut-off valve for CO2 supply to avoid asphyxiating
the patient;
separate COZ and 02 metering valves; a common gas mixing chamber; a buffer
volume; a
demand regulator, hose and facemask; a means to purge the system and the
buffer volume of
previous gas mixtures prior to each new use. This embodiment only requires
connection to an
outside, readily available source of pressurised 02 to operate. The invention
also includes
alternate methods of providing a suitable gas metering orifice. The invention
also includes a
member to filter either or both of the therapeutic gases prior to metering.
The invention also relates to a gas metering and mixing apparatus for gases
under
pressure, particularly for respirators and medical devices, comprising a
plurality of gas
meters, a gas mixer device, a plurality of compressed gas supply lines
connected to said gas
meters, a plurality of mixed gas delivery lines extending out of said gas
mixer device for the
discharge of a mixture of gases from said compressed gas supply lines from
said gas meters
and from said gas mixer device to a demand regulator, hose and facemask and to
a buffer
storage volume, and a means of selecting which gases, 02, mixture or none, are
sourced to
said metering and mixing device and at least an automatic shut-off valve for
one of the
therapeutic gases, C02, which could in excess cause patient asphyxiation
without said shut-off
valve performing its function and with a means of purging the system including
the buffer
volume of mixed gases (or 02 as appropriate). The automatic shut-off valve
preferably
includes means of adjusting said valve to vary the pressure in which it opens.
The invention
also includes a gas metering and mixing apparatus, wherein said metering can
be adjusted to
vary the proportions of the two different therapeutic gases. The apparatus
preferably includes
the use of sonic nozzles to meter said therapeutic gases. The invention also
includes alternate
devices for metering said therapeutic gases. The gas metering and mixing
apparatus includes
the ability to add filtration to the system as a means of protecting the sonic
nozzles. The
invention also includes a gas metering and mixing apparatus which includes the
ability to add
filtration to the system to protect the alternate metering means.
The invention includes an apparatus for treating carbon monoxide poisoning in
a
subject by administering to the subject oxygen from a source of oxygen and
carbon dioxide
from a source of carbon dioxide, comprising:
= an oxygen conduit defining an oxygen inlet and an oxygen outlet, the oxygen
inlet
adapted for fluid communication with the source of oxygen;
= a carbon dioxide conduit defining a carbon dioxide inlet and a carbon
dioxide outlet, the
carbon dioxide inlet adapted for fluid communication with the source of carbon
dioxide;
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= a means for combining the oxygen and the carbon dioxide, the means
downstream from
the oxygen outlet and the carbon dioxide outlet; and
= a means for administering the combined oxygen and carbon dioxide to the
subject.
In a variation, apparatus comprises a gas control means associated with the
apparatus
for controlling the pressure, flow rate and the ratio of the combined oxygen
and carbon
dioxide. The gas control means optionally comprises an oxygen regulator for
controlling
oxygen pressure and a carbon dioxide regulator for controlling carbon dioxide
pressure, the
oxygen regulator located between the oxygen source and the combining means and
the carbon
dioxide regulator located between the carbon dioxide source and the combining
means. The
regulators also control nominal flow rate of the oxygen and carbon dioxide.
In a variation, the control means further comprises an oxygen sonic nozzle
downstream of the oxygen regulator and a carbon dioxide sonic nozzle
downstream of the
carbon dioxide regulator, the nozzles dispensing the oxygen and the carbon
dioxide. The
nozzles dispense the oxygen and the carbon dioxide according to a
predetermined flow rate.
The apparatus preferably also comprises a means for reducing the flow of
carbon dioxide
when the percentage of carbon dioxide in the combined carbon dioxide and
oxygen exceeds
about 6.5% by volume. In another embodiment, the reducing means prevents the
flow of
carbon dioxide.
The invention also includes a variation where the means for reducing the flow
of
carbon dioxide comprises a differential pressure sensor downstream of the
carbon dioxide
source and/or the oxygen source.
Another variation involves the reducing means being located proximate to the
conduits and in fluid communication with the oxygen and the carbon dioxide
sources.
In another variation, the reducing means of the apparatus comprises: a shutoff
member located proximate to the carbon dioxide conduit having an on position
in which the
shutoff member permits the carbon dioxide to communicate from the carbon
dioxide source to
the combining means and an off position in which the shutoff member prevents
the carbon
dioxide from communicating from the carbon dioxide source to the combining
means; an
actuating means for actuating the shutoff member from the on position to the
off position
when the percentage of carbon dioxide in the combined carbon dioxide and
oxygen exceeds
about 6.5% by volume, the actuating means operably connected to the shutoff
member and
responsive to differential pressure in the oxygen conduit and the carbon
dioxide conduit.
Optionally, the actuating means comprises:
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= a piston means in fluid communication with the oxygen conduit, the piston
means located
proximate to the oxygen conduit and including a first position in which the
piston means
is biased away from the oxygen conduit and actuates the shutoff member to the
on
position and a second position in which it is biased towards the oxygen
conduit and
actuates the shutoff member to the off position;
= a biasing means for urging the piston toward the second position;
the piston means normally biased by oxygen toward the first position against
the force of the
biasing means, the piston means being urged toward the second position by the
biasing means
when oxygen pressure decreases in the oxygen conduit.
According to another aspect of the invention, the combining means comprises a
mixing chamber.
In another variation, the administering means of the apparatus comprises a
face-mask
including a conduit in fluid communication with the combining means, the face-
mask adapted
for placement over the face of the subject. The face-mask optionally comprises
a pressure
regulator.
The invention also includes the variation where the apparatus further
comprises a
buffer in fluid communication with the combining means, the buffer including
combined
oxygen and carbon dioxide.
In another variation, the administering means is capable of administering the
combined oxygen and carbon dioxide to the subject in an amount effective to
increase the
breathing rate of the subject. The carbon dioxide is about 3.5 to 6.5 percent
by volume of the
combined oxygen and carbon dioxide.
According to another aspect of the invention, the combined carbon dioxide and
oxygen are in a ratio of about 19:1 by volume.
In a variation, the combined carbon dioxide and oxygen have a pressure of
about 1
atm to 20 psig.
The invention also includes the variation where the oxygen conduit and the
carbon
dioxide conduits are connected to a tubular housing and extend into the
housing.
In another variation, the conduits of the apparatus are defined by the
housing, and are
integrally defined by the housing.
In a variation the apparatus is portable. Portable means that the apparatus
can fit
inside an emergency vehicle and is practical for use in an emergency situation
(for example, it
can preferably be carried by a person). It further comprises optionally a
carbon dioxide tank
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capable of connection to the carbon dioxide conduit. The apparatus is
preferably capable of
fitting in a briefcase. The subject is a mammal, preferably a human. The
apparatus is
preferably operable without electric power. It is optionally pneumatically
powered.
The invention may also include a selector means or device to control the flow
of
carbon dioxide and oxygen. In one embodiment, the selector means may include a
rotary
selector 40. The invention may also include a purging means or device, such as
the valve 140
and port 160 for purging carbon dioxide and oxygen.
Another embodiment of the invention relates to a portable kit for treating
carbon
monoxide poisoning, comprising the apparatus of the invention.
This invention also includes a method of treating carbon monoxide poisoning,
comprising administering to a subject an effective amount of combined oxygen
and carbon
dioxide from the apparatus disclosed. The invention also includes the use of
an apparatus of
the invention for treatment of carbon monoxide poisoning.
The invention includes an apparatus for treating carbon monoxide poisoning in
a
subject by administering to the subject oxygen from a source of oxygen and
carbon dioxide
from a source of carbon dioxide, comprising:
= an oxygen conduit defining an oxygen inlet and an oxygen outlet, the oxygen
inlet
adapted for fluid communication with the source of oxygen;
= a carbon dioxide conduit defining a carbon dioxide inlet and a carbon
dioxide outlet, the
carbon dioxide inlet adapted for fluid communication with the source of carbon
dioxide;
= a device for combining the oxygen and the carbon dioxide, the device
downstream from
the oxygen outlet and the carbon dioxide outlet; and
= a device for administering the combined oxygen and carbon dioxide to the
subject.
The apparatus optionally further comprises a gas control device associated
with the
apparatus for controlling the pressure, flow rate and the ratio of the
combined oxygen and
carbon dioxide.
The control device optionally further comprises an oxygen sonic nozzle
downstream
of the oxygen regulator and a carbon dioxide sonic nozzle downstream of the
carbon dioxide
regulator, the nozzles dispensing the oxygen and the carbon dioxide. The
apparatus
optionally further comprises a device for reducing the flow of carbon dioxide
when the
percentage of carbon dioxide in the combined carbon dioxide and oxygen exceeds
about 6.5%
by volume. The reducing device may comprise:
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= a shutoff member located proximate to the carbon dioxide conduit having an
on position
in which the shutoff member permits the carbon dioxide to communicate from the
carbon
dioxide source to the combining device and an off position in which the
shutoff member
prevents the carbon dioxide from communicating from the carbon dioxide source
to the
combining device;
= an actuating device for actuating the shutoff member from the on position to
the off
position when the percentage of carbon dioxide in the combined carbon dioxide
and
oxygen exceeds about 6.5% by volume, the actuating device operably connected
to the
shutoff member and responsive to differential pressure in the oxygen conduit
and the
carbon dioxide conduit. The actuating device optionally comprises:
= a piston device in fluid communication with the oxygen conduit, the piston
device located
proximate to the oxygen conduit and including a first position in which the
piston device
is biased away from the oxygen conduit and actuates the shutoff member to the
on
position and a second position in which it is biased towards the oxygen
conduit and
actuates the shutoff member to the off position;
= a biasing device for urging the piston toward the second position;
the piston device normally biased by oxygen toward the first position against
the
force of the biasing device, the piston device being urged toward the second
position by the
biasing device when oxygen pressure decreases in the oxygen conduit. The
device described
above may include various means, as described below.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will be described by way of example and with
reference to the
drawings in which:
FIG. 1 is a general cross-sectional view of the first embodiment of the
present invention;
FIG. 2 is a detailed cross-sectional view of the first embodiment of the
present invention;
FIG. 3 is a cross-sectional view of an alternative orifice arrangement;
FIG. 4 is a cross-sectional view of a filtering assembly;
FIG. 5 is a general schematic diagram of the second embodiment of the present
invention; and
FIG. 6 is a detailed schematic diagram of the second embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention comprises a pneumatic control assembly for metering and mixing
02
and CO2 in prescribed proportions. The system would preferably operate
sonically, with
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sonic nozzle orifice sizes and pressures adjusted so that the gases are
delivered in a 95% to
5% ratio by volume (see Marks Standard Handbook for Mechanical Engineers 9th
Edition
1987; John B. Heywood, Internal Combustion Engine Fundamentals, McGraw Hill
1988).
However, other ratios could readily be used: typically a useful range for
carbon monoxide is
from about 3.5 to 6.5 percent of the combined volume. The control system can
be manually
selected to deliver pure oxygen, the O2 - CO2 mixture, or in two "pause"
positions, no gases.
A manual valve would preferably allow system purging by venting all contained
gases to
atmosphere. When operating, the system preferably monitors the 02 and CO2
input pressures.
Should the two pressures become significantly different the system would
automatically stop
the CO2 flow. This feature is desirable because high concentration or pure CO2
delivery
would cause asphyxiation.
The invention relates to an apparatus for treating carbon monoxide poisoning
in a
subject by administering to the subject oxygen from a source of oxygen and
carbon dioxide
from a source of carbon dioxide, comprising:
= an oxygen conduit defining an oxygen inlet and an oxygen outlet, the oxygen
inlet
adapted for fluid communication with the source of oxygen;
= a carbon dioxide conduit defining a carbon dioxide inlet and a carbon
dioxide outlet,
the carbon dioxide inlet adapted for fluid communication with the source of
carbon
dioxide;
= a means for combining the oxygen and the carbon dioxide, the means
downstream
from the oxygen outlet and the carbon dioxide outlet; and
a means for administering the combined oxygen and carbon dioxide to the
subject.
The conduits may be any conduit compatible with safe medical delivery of
carbon dioxide
and oxygen. In one embodiment of the invention, the conduits include a
connecting passage
21 or a flow passage 31 as shown in figure 2 The combining means may include a
mixing
chamber. For example, one embodiment of the invention includes a mixing
chamber 110 as
shown in figure 2. The invention also includes a means for administering the
combined
oxygen and carbon dioxide to the subject. The administering means may comprise
a face-
mask including a conduit in fluid communication with the combining means, the
face-mask
adapted for placement over the face of the subject.
The apparatus preferably also includes a gas control means associated with the
apparatus for controlling the pressure, flow rate and the ratio of the
combined oxygen and
carbon dioxide. The gas control means optionally includes a combination
regulators (for
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example a regulator may be proximate to the oxygen or carbon dioxide source or
the face
mask) and sonic nozzles.
The apparatus optionally also includes a means for reducing the flow of carbon
dioxide when the percentage of carbon dioxide in the combined carbon dioxide
and oxygen
exceeds about 6.5% by volume. In one variation, this means includes a carbon
dioxide shut-
off valve 70. The reducing means optionally includes a shutoff member
including on and off
positions and an actuating means for actuating the shutoff member from the on
position to the
off position when the percentage of carbon dioxide in the combined carbon
dioxide and
oxygen exceeds about 6.5% by volume. The acutating means may include a sensor
80 shown
in figure 2 having a piston means such as the body 81 and a biasing means such
as the spring
86. Other devices for reducing or preventing carbon dioxide flow will be
apparent.
According to the first embodiment, the invention preferably comprises a
pneumatic
control assembly for metering and mixing 02 and COZ in prescribed proportions
for applying
the invented therapy. According to the second embodiment, the invention
comprises a self-
contained apparatus, except for the 02 supply, for administering the invented
CO poisoning
therapy.
Referring to Figure 1, the pneumatic assembly 5 preferably consists of the
following
major components: body; gas selector; CO2 valve; 02 valve; CO2 shut off valve;
differential
pressure sensor; COz metering orifice; 02 metering orifice; and purge valve.
The pneumatic
assembly 5 also consists of 5 ports: COZ inlet port; 02 inlet port; outlet to
demand regulator
and facemask; outlet to buffer volume; and purged gas outlet port. It will be
apparent that
parts of the embodiments of the invention can be omitted or varied.
The system receives pure COZ and 02 at inlet ports 20 and 30 respectively. The
pressures at ports 20 and 30 may be in the operating range of approximately
3.4 bar (50 psig).
The inlet pressures for each gas are pre-set and relatively constant and are
supplied from gas
sources and pressure regulators not shown. Since the human body does not need
precisely
5% CO2, the pressures do not have to be exact. For example, if the input
pressures fluctuated
from 2.8 to 3.8 bar the mass flow rate would only vary by 11.4%, which is
acceptable.
A rotary selection device 40 has two cam lobes to enable 02 or COZ/O2 as
required.
Preferably, the apparatus has four positions, with positive detent stops for
each selection. The
positions are: OFF; MIXTURE: 02; and OFF. The two off positions remind the
operator to
purge the system prior to selecting a gas flow position. As shown, in Figures
1 and 2 both
gases are selected. Accordingly both the COZ valve 50 and the 02 valve 60 are
forced open by
the cam lobes, enabling flow of both gases. If the CO2 and 02 pressures are
nearly equal,
differential pressure sensor 80 opens the CO2 shutoff valve 70, allowing COz
to flow to the
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metering point. Should the COZ pressure significantly exceed the 02 pressure,
sensor 80 will
retract and thereby shut-off valve 70 will close, and the flow of COZ will
stop.
Metering orifices 90 and 100 meter the CO2 and 02 respectively in the correct
proportions. Those orifices are preferably sonic. However, downstream
backpressure may
occasionally rise to the point where the orifices become sub-sonic. That brief
condition is
allowed since it represents low flow, or very shallow breathing on the
patient's behalf. In this
case the volumetric error of the gas mixture is quite low and the therapeutic
value of the gas
mixture is not appreciably diminished. The output of the two gases is combined
in mixing
chamber 110. The two gases collide at an angle to facilitate mixing, as for
example 90 , as
they enter mixing chamber 112, creating turbulence, and promoting mixing. The
mixed gases
pass on to outlet port 120, which is connected to a conventional demand type
regulator and
facemask (not shown). When the patient inhales, the demand regulator withdraws
the
inspiratory volume from the gas-mixture port 120. When the patient exhales,
the demand
regulator isolates the facemask from 120 and vents the expiratory gases to
atmosphere. The
system is assumed to store a quantity of the gas mixture in a buffer volume,
to support large
instantaneous demands. Outlet port 130 provides a connection between the
buffer volume
and the regulator port 120.
After usage, depressing purge valve 140 purges the system. That is, all gases
stored
in the apparatus and in the buffer volume are vented to port 160.
Figure 5 shows a second embodiment of the invention 200, which includes the
following major components: carrying case 210; COZ supply 220; COz regulator
230; 02
regulator 240; control system 5; buffer volume 250; demand regulator 260; low
pressure hose
270; face mask 280; purge line 290.
Preferably, the apparatus is enclosed in a portable case 210, to which all of
the
components would be mounted. This case is preferably the size of a briefcase.
The apparatus
includes a medium pressure storage system, for example a conventional cylinder
220 for
storage of CO2. Preferably the dimensions of the cylinder are 3" in diameter
and 16" long.
As the CO2 stored pressures might in practice range between 3 and 100 bar, a
metal or
composite cylinder would preferably be used (such cylinders are commercially
available).
The stored CO2 would be connected to a regulator 230, which reduces pressure
to a low,
relatively constant pressure (preferably about 3.4 bar). At extreme pressure,
accuracy is not
required, and a single stage unbalanced regulator would be acceptable
(numerous such
devices are commercially available). The regulated COz would then be sealably
connected to
the pneumatic control device S described in the first embodiment above.
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An 02 input and regulation system 240 would receive unregulated 02 from an
external source via a quick disconnect. Preferably, the 02 pressure would
range from 3.4 to
160 bar. The received 02 is connected to a regulator (part of 240) which
reduces its pressure
to a low, relatively constant pressure (typically 3.4 bar). At extreme
pressure, accuracy is not
required, a single stage unbalanced regulator would be acceptable (numerous
such devices are
commercially available). The regulated 02 would then be sealably connected to
the
pneumatic control device 5 described in the first embodiment above.
Depending on the selector position, control device 5 would then deliver no
gas, pure
02, or the invented therapeutic gas-mixture to both a cylindrical buffer
volume 250 and to a
demand regulator 260. The pressure in the buffer volume would normally swing
between
atmospheric pressure and approximately 20 psig, with its maximum pressure
being the
regulated pressures (approximately 3.4 bar). Accordingly, the buffer volume is
preferably a
low cost metal or plastic cylinder, fabricated from tubing (e.g. spherical
ends are not required)
preferably having dimensions of 4" in diameter and 8" long.
When the patient inhales, the demand regulator senses the sub-atmospheric
pressure
at its outlet port and opens its flow valve to restore a slightly positive
pressure (about 1 to 1.5
kPa). Thus the inhalation event causes the demand regulator 260 to withdraw
gas from the
control system 5 and deliver that gas to the facemask 280. During inhalation,
the demand
regulator's valve throttles the flow to match the inspiratory volume demanded.
Such demand
regulators are commercially available When the patient stops inhaling, the
pressure starts to
rise above the 1 to 1.5 kPa set pressure and the demand regulator shuts off. A
simple valve
(preferably a rubber flapper or umbrella valve) in the outlet chamber 260
vents the outlet
gases to atmosphere whenever an overpressure exists. Such an overpressure
condition exists
every time the patient exhales.
The outlet of the demand regulator 260 is connected to a conventional facemask
280
by preferably a flexible low-pressure hose 270. The items 260, 270, and 280
are readily
available commercial parts.
Figure 2 shows the control system 5 preferably housed in a non-sparking body
10,
such as brass to prevent inadvertent problems in the presence of the 02 gas.
Regulated CO2
(having a preferred inlet pressure of approximately 3.4 bar) is received at
any suitable inlet
port 20, such as a threaded female port. After entering port 20, the CO2 would
pass through a
connecting passage 21 and enter valve chamber 22. If the COZ valve 50 is open
(as shown),
the CO2 passes through the space between the valve seat 23 and the valve seal
55. If the valve
50 is shut (not shown), gas flow is prevented by seal 55 resting on seat 23.
As shown, CO2
flows through the annular space between throat area 24 and the actuator tip 45
and into
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interconnecting passage 25. Connecting passage 25 is permanently sealed after
construction
by a conventional ball 11 and plug 12 system.
COz then passes through 25 (and around 81a) into valve chamber 26. If the COz
shut-
off valve 70 is closed (not shown), seal 75 sitting on valve seat 13 blocks
CO2 flow. If valve
70 is open (not shown), the COz passes through the space between the valve
seat 13 and the
valve seal 75. CO2 then passes through the throat area 27 and into connecting
passage 28.
From passage 28 the gas turns an angle to facilitate mixing (for example about
90 ) as it
passes into orifice chamber 29. All of the flow passages (21, 25, 28), flow
annuli (23-45, 27-
81a), and valve-seat clearances (23-55, 13-75) are chosen so as to be non-
restrictive to flow
when compared to the calibrated restriction presented by orifice insert 90.
Orifice insert 90 meters the CO2 in accordance with the ideal gas law. The
insert 90
is comprised of a body 91 with threaded section 92 for retaining the component
in bore 14.
An o-ring 93 (or other appropriate seal), seals the outside diameter of insert
90 to the inside
diameter of cavity 29 so that all COz flow must pass through the centre of
orifice insert 90.
The actual metering section of orifice insert 90 is comprised of a converging
inlet section 95,
a straight throat area 96 (which is the metering orifice) and a diverging
pressure recovery
section 97. Two holes 94 in the outlet face of orifice insert 90 allow the
insert to be tightened
by means of a special tool.
CO2 exiting orifice insert 90 enters bore 14, then turns turns an angle such
as to
facilitate mixing (for example, about 90 ) as it enters connecting passage
110. This angular
turn creates turbulence, which helps to mix the CO2 and 02. Connecting passage
110
intersects mixing chamber 112, which is in direct communication with outlet
port 120.
Preferably port 120 is typically a female port, with threaded section 121, and
is connected to a
demand regulator. Gas in chamber 112 is also in communication with outlet port
130.
Preferably, port 130 is typically a female port, with threaded section 131,
and is connected to
a buffer volume.
Regulated 02 (having a preferred inlet pressure of approximately 3.4 bar) is
received
at any suitable inlet port 30, such as a threaded female port. After entering
port 30, the 02
would pass through a connecting passage 31 and enter valve chamber 32. If the
02 valve 60
is open (as shown), the 02 passes through the space between the valve seat 33
and the valve
seal 65. If the valve 60 is shut (not shown), gas flow is prevented by seal 65
resting on seat
33. As shown, 02 flows through the annular space between throat area 34 and
the actuator tip
48 and into interconnecting passage 35.
02 then passes through 35 into valve chamber 16. The 02 passes through the
annular
gap between chamber 16 and the "nose" 87b of adjuster 87 and on into orifice
chamber 37.
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Some 02 may also flow in the annular gap between 16 and spring 86. All of the
flow
passages (31, 35, 37), flow annuli (16-87b, 16-86), and valve-seat clearance
(33-65) are
chosen so as to be non-restrictive to flow when compared to the calibrated
restriction
presented by orifice insert 100.
Orifice insert 100 meters the 02 in accordance with the ideal gas law. The
insert 100
is comprised of a body 101 with threaded section 102 for retaining the
component in bore 15.
An o-ring 103 (or other appropriate seal), seals the outside diameter of
insert 100 to the inside
diameter of cavity 37 so that all 02 flow must pass through the centre of
orifice insert 100.
The actual metering section of orifice insert 100 is comprised of a converging
inlet section
105, a straight throat area 106 (which is the metering orifice) and a
diverging pressure
recovery section 107. Two holes 104 in the outlet face of orifice insert 100
allow the insert to
be tightened by means of a special tool.
02 exits the orifice insert 100 and the mixing chamber 112, which is in direct
communication with outlet port 120. During periods where the mass flow is
entering the
buffer volume, the 02 gas stream continues straight through 112, and collides
with the COz
gas stream at right angles, thus promoting mixing. The mixed gases then pass
from 112 into
port 130 for delivery to the buffer volume. During periods where the mass flow
is passing to
the demand regulator, the 02 turns 90 in order to pass from mixing chamber
112 into outlet
port 120. The turbulence from turning 90 and from the 02 and COZ impinging
one another at
90 promotes mixing. From 112, the mixed gas (or 02 only if this operation is
selected) enter
port and is connected to a demand regulator.
The flow diameters seen by the metered and mixed gases (14, 15, 110, 112) are
preferably sized so as to minimize pressure drop at high instantaneous flow
rates. The
nominal maximum inspiratory flow rate is assumed to 60 standard litres per
minute.
Preferably, a rotary selector 40 is used to actuate COZ and 02 valves 50 and
60.
Selector 40 has two cam lobes, 42 and 43, which select COZ and 02
respectively. The lobes
are presumed to provide four positions: OFF; MIXTURE; 02; and OFF. This
arrangement
always allows the user to select the other therapeutic gas stream (than that
currently used) or
OFF with one click of the selector. Additionally to move from one therapeutic
gas stream to
another requires two clicks of the selector as a reminder to the operator to
purge the system
prior to selecting the second therapeutic gas stream. Accordingly, the
selector preferably
includes a conventional ball-spring-detent system (not shown) so that the
selector stops at
each position. If the cam lobes are on a single plane (as shown), the selector
would rotate
through no more than 180 . If continuous 360 rotation were desired, the two
cams would be
placed on separate planes.
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As shown in Figure 2, cam lobe 42 has engaged COZ actuator 44 and moved it to
its
maximum open position. The actuator tip 45 engages a recess 56 in piston 54,
lifting 54 off
of valve seat 23. The end of tip 45 would typically be hemispherical and
recess 56 would
typically be conical or hemispherical so that the two parts would move freely
and smoothly.
Actuator 44 slides in bore 17 preferably machined into body 19, and is sealed
to that bore by
o-ring 46 (or other appropriate seal). The height of the cam lobe 42, from the
base circle of
41 would typically be such a fraction of sealing diameter of seat 23 such as
to ensure that the
valve seal 55 does not impact the flow rate when piston 54 is in its open
position, for example
about 40%. Piston 54 rides in a companion bore in body 51, with suitable
radial clearance.
Spring 57 acts to move piston 54 to its closed position when cam lobe 42 is
not selecting CO2.
In that case, the force from spring 57 must overcome the friction from o-ring
46 and provide
the force needed to create an effective seal between 55 and 23. As shown,
adjuster 58, sealed
by o-ring 58a to body 51, is available to set the pre-load from spring 57. A
special tool
engaging the two holes 59 in its face turns adjuster 58. The valve body 51 is
retained in body
10 by thread 52, and sealed from external leakage by o-ring 53. A special tool
engaging the
two holes 51a in its face tightens the valve body 51.
As shown in Figure 2, cam lobe 43 has engaged 02 actuator 47 and moved to its
maximum open position. The actuator tip 48 engages a recess 66 in piston 64,
lifting 64 off
of valve seat 33. The end of tip 48 is preferably hemispherical and recess 66
is preferably
conical or hemispherical so that the two parts move freely and smoothly.
Actuator 47 slides
in bore 18 preferably machined into body 10, and is sealed to that bore by o-
ring 49 (or other
appropriate seal). The height of the cam lobe 43, from the base circle of 41
is preferably at
least 40% of sealing diameter of seat 33. That value ensures that the valve
seal 65 does not
impact the flow rate when piston 64 is in its open position. Piston 64 rides
in a companion
bore in body 61, with suitable radial clearance. Spring 67 acts to move piston
64 to its closed
position when cam lobe 43 is not selecting 02. In that case, the force from
spring 67 must
overcome the friction form o-ring 49 and provide the force needed to create an
effective seal
between 65 and 33. As shown, adjuster 68, sealed by o-ring 68a (or other
appropriate seal) to
body 61, is available to set the pre-load from spring 67. A special tool
engaging the two holes
69 in its face turns adjuster 68. The valve body 61 is retained in body 10 by
thread 62, and
sealed from external leakage by o-ring 63(or other appropriate seal). A
special tool engaging
the two holes 61a in its face tightens the valve body 61.
Referring to Figure 2, sensor 80 is comprised of body 81 which slides in bore
19
machined into body 10, and is sealed to that bore by o-ring 83 (or other
appropriate seal). The
outer diameter of body 81 is reduced in area 81a so as to minimize the flow
restriction in
connecting passage 25. Sensor tip 82 operates against lever 79, which moves
through an arc
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CA 02371161 2001-10-24
WO 00/64522 PCT/CAOO/00481
to raise piston 74 off of valve seat 13. Specifically, the right end of lever
79 rests against the
bottom ledge of groove 79a, which is in body 10, and acts as a pivot point for
79. Lever 79
passes through slot 78 in piston 74, with the 78-74 contact point serving to
raise or lower 74.
The end of tip 82 is preferably hemispherical so that lever 79 will move
freely and smoothly.
When the pressures in chambers 16 and 27 (OZ and C02) are roughly equal,
spring 86 acts to
move sensor 81 to its fully open position, moving piston 74 off of seat 13,
and enabling CO2
to flow. Adjusting the pre-load on spring 86 by turning adjuster 87 largely
sets the C02-02
differential pressure required to close sensor 80. Adjuster 87 slides in bore
16 and is sealed to
that bore by o-ring 88 (or other appropriate seal). A special tool engaging
the two holes 89 in
its face preferably tightens the adjuster 87. Its position is retained by
thread 87a. The fully
open position of sensor 80 is controlled by lip 84 on body 81 engaging a seat
85 machined in
the end of bore 16.
The fully open position of sensor 81 preferably provides a gap (13-75) such as
to
ensure that the valve seal does not impact the flow rate when piston 74 is in
its open position,
as for example, at least 40% of the sealing diameter of seat 13. Piston 74
rides in a
companion bore in body 71, with suitable radial clearance. Spring 77 acts to
move piston 74
to its closed position when sensor 81 retracts to disable COz flow.
The mixed gas in chamber 112 is communicated to the input of purge valve 140
by
passage 111. Valve 140 includes a plunger 153 attached to seat 151 by thread
152. Seat 151
is normally closed against the protruding seal profile 150 of elastomeric
sea1149 (or other
suitable sealing material), preventing the flow of gases into the purge port
161. This normally
closed state is maintained by spring 155 acting against purge body 141 and
pushbutton 156, to
maintain a closing force on the 150-151 seal interface. Plunger 153 slides in
bore 147 of body
141 and is sealed to that bore by o-ring 154 (or other suitable sealing
means). Body 141 is
retained in body 10 by thread 142 and sealed from external leakage by o-ring
143 (or other
suitable sealing means). Body 141 is preferably tightened by a special tool,
which engages
the two holes 144 on the rear face of 141. When pushbutton 156 is depressed,
seat 151 moves
away from seal 150 admitting purge gas into the annular space between throat
157 and
plunger pin 158. The purge gas then passes into the annular space between bore
147 and pin
158. The outside diameter of body 141 has an annular relief 145, which is
intersected by four
through holes 146. The 145-146 system allows purge gas in the 147-158 cavity
to pass first
into connecting chamber 159 and then into the purge port 160. Port 160 is
typically a female
port with thread 161.
As shown in Figure 6, a briefcase-sized system 200 would include all of the
items
needed to provide the therapeutic gas mixture, except for 02 storage. As
ambulances,
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WO 00/64522 PCT/CAOO/00481
emergency vehicles, fire trucks and hospitals, or other health institutions,
already have 02
storage available, there is no benefit to including the 02 storage system in
such a device.
The apparatus preferably includes a suitcase type of enclosure 210, which
would
house and mount all of the equipment. The largest item is most likely the COZ
storage system
220. System 220 preferably includes a COZ source 221, capable of operating at
least 100 bar.
The outlet of 221 accommodates a cylinder valve 222, with a manual shut-off
valve 223 for
switching COZ sources, an outlet port 224, and a quick connect 225. Quick
connect 225
would be permanently attached to a line 226, which delivers the unregulated
COz to the
pressure regulator 230. Preferably, a full COz cylinder would preferably
contain enough CO2
to handle two therapy events of 30 minutes each, at 60 litres per minute
inspiratory flow at
5% CO2 by volume. The COz cylinders 221 would be replaced routinely (and after
each use)
and re-filled as an unrelated activity.
The COz regulator 230 includes an inlet 232, a main regulator section 231, and
an
outlet 233. The regulating section 231 preferably comprises a single stage,
non-balanced
conventional pressure regulator. The output of the regulator would be
permanently connected
to the inlet port 20 of control device 5 (previously described).
The 02 is preferably sourced externally. The 02 circuit 240 includes a portal
241 in
the suitcase 210 through which a quick-connect 242 passes. Quick connect 242
is connected
to line 243 which routes the input 02 to pressure regulator 244. The 02
regulator 244 includes
an inlet 245 and an outlet 246. The regulating section 244 preferably
comprises a single
stage, non-balanced pressure regulator. Commercial devices are readily
available. The
output of the regulator is permanently connected to the inlet port 30 of
control device 5
(previously described).
Control device 5 includes a selector 40, to choose 02, Mixture, or no gases. A
button
153 would be used to purge the system after use, with purge gases being vented
to port 160.
Purged gases would be plumbed through line 291 to a terminal vent fitting (or
quick connect)
292, passing through a portal 293 in the carrying case.
The gas output of control device 5 would appear at ports 120 and 130. Port 130
would be permanently connected to a buffer volume 250. As buffer 250 typically
sees only
20 psig, it would preferably be of inexpensive construction, such as from thin
wall metal pipe
with simple end caps. Preferably, the dimensions of the buffer volume are 4"
diameter by 8"
in length.
Port 120 is connected to a demand-type regulator 260 (previously described).
At a
minimum, regulator 260 would include an inlet 261, a main regulator section
262, an over
CA 02371161 2001-10-24
WO 00/64522 PCT/CAOO/00481
pressure relief valve 263, and an outlet 264. Regulator 260 is connected to a
conventional
facemask 280 by a conventional flexible hose 270.
For example, Figure 3 shows an alternative orifice arrangement. Certain
combinations of design criteria (buffer volume, COZ and 02 pressure, and
maximum and
minimum respiratory rates) can require very small orifice sizes. In such
cases, the design
format shown for orifices 90 and 100 may be impractical to machine. For
example, orifice
size could be as small as 0.003", which is very difficult to mechanically
machine using
conventional methods. Accordingly, an alternative orifice arrangement is
provided, as shown
in Figure 3, orifice insert 170 includes an outer body 171, machined
conventionally. Body
171 has a similar o-ring sealing diameter 171, and the same o-ring (103) as
inserts 90 and
100. Body 171 includes a conventional o-ring gland 173. A similar body outside
diameter
174 would be used, along with the same thread 102, as seen in 90 and 100. Body
171
includes a converging inlet section 178, terminating at face 177, with a
relatively large
terminal outside diameter 179. A preferably thin, circular, flat orifice plate
180 would be
inserted from the rear of body 171 and is seated against the face 177. The
orifice plate
preferably comprises metal substrate with a small through hole 181. Electron
discharge
machining, laser drilling, mechanical micro machining, and chemical micro-
machining means
can reliably produce such small holes. The hole 181 would be the actual
metering orifice, and
the thickness of the plate 180 would provide the desired throat depth. Plate
180 is held in
body 171 by a plug 190. Plug 190 threads into 171 via thread 192, and would
seal to 180 and
171 by seal 182. Plug 190 creates a chamfer type o-ring gland via surface 197
and sits against
the orifice with surface 196. Where practical, plug 190 may preferably have a
second throat
section 195 and a diverging pressure recovery section 194. Plug 190 is
preferably tightened
into body 171 via a special tool engaging two holes 193 in its rear face. A
commercially
available thread sealant would lock plug 190 to orifice insert 170 so that it
would function as
an integral piece and could be installed and removed from body 10 without the
two pieces
separating.
A filtration means is optionally provided to keep the orifices clean. In the
case of
very small orifices, there could be a concern about foreign particles lodging
in and blocking
the metering orifices. In such a case, a filter element could be included in
each orifice. As
shown in Figure 4, filter element 199 could be press fitted into a recess 198
in insert 170.
Such filter elements are commercially available and could include a wire
screen, a sintered
(porous) brass or porous fabric.
It will be appreciated that the above description relates to the preferred
embodiments
by way of example only. Many variations on the apparatus for delivering the
invention will
21
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WO 00/64522 r%, i iq.twwvoL*o i
be obvious to those knowledgeable in the field, and such obvious variations
are within the
scope of the invention as described and claimed, whether or not expressly
described.
22
