Patent Description:
Human breathing involves a large variety of inhalation profiles that a supplemental oxygen system for altitude breathing needs to support. Supplemental oxygen delivery systems for assisted breathing at altitude must be able to support a broad variety of human breathing scenarios and inhalation profiles. For example, inhalation may vary among individuals, whether the individual is speaking, or due to changes in physical workload (or due to other like stressors).

Supplemental oxygen may be conserved via the use of a phased-dilution system, which provides oxygen at the start of an inhalation cycle. Phased dilution may be normally realized by a combination of a "breathing bag" and a dilution valve (e.g., TSO C64 mask). The amount of added oxygen can be reduced by up to <NUM>% in comparison to the AIR825 minimum concentration requirements (provided in continuous dilution mode), as basically the oxygen provided at the beginning of the inhalation cycle gets inhaled deeper into the lungs and chances of exchange into the blood increase. As a result, added oxygen may be significantly reduced compared to a continuous demand dilution system (which provides oxygen throughout the inhalation cycle). <CIT> discloses an oxygen supply system for an aircraft, wherein the said system comprises a control valve, a reservoir bag, a respiration device and a sensor device, wherein the control valve is designed in such a way that oxygen can be supplied to the reservoir bag until a predetermined quantity of oxygen is adjusted in the reservoir bag. The respiration device may be designed in such a way that breathing gas can be provided for a passenger. The sensor device may be designed in such a way that an exhalation is detectable. The reservoir bag may be designed in such a way that a predetermined quantity of oxygen can be metered into the reservoir bag during the exhalation. Moreover the reservoir bag may be designed in such a way that breathing gas can be supplied to the respiration device in a pulse-like fashion. <CIT> discloses an emergency oxygen supply system for use on aircraft in the event of a loss in cabin pressure that is configured for delivering allotments of oxygen and timing the delivery of such allotments to each passenger so as to maximize the efficiency of the transfer of such oxygen into the passenger's bloodstream. The delivery of each allotment is selected so that the entire allotment is available for inhalation into the region of the lung most efficient at oxygen transfer while the volume of the allotment is selected to substantially coincide with the volume of such region of the lung. <CIT> describes an adaptable demand dilution oxygen regulator for use inside a pressurized aircraft cabin, comprising: an oxygen initiation and demand regulation system adapted to be responsive to differential gas pressure in a first altitude range based on a pulmonary capacity of a person flying in the pressurized aircraft cabin, wherein the oxygen initiation and demand regulation system controls flow of pressurized oxygen to a breathing outlet by mixing the pressurized oxygen with aircraft cabin air during the first altitude range; and a cabin air dilution and delivery system coupled to the oxygen initiation and demand regulation system, wherein the cabin air dilution and delivery system is adapted to be responsive to differential gas pressure in a second altitude range, and wherein the cabin air dilution and delivery system gradually stops dilution of the aircraft cabin air and outputs approximately about <NUM>% pressurized oxygen into a breathing apparatus via the breathing outlet during the second altitude range, and wherein the first altitude range and the second altitude range are substantially below a cabin pressure altitude of approximately about <NUM> feet, and wherein the first altitude range is lower than the second altitude range. <CIT> describes an inhaling comprising a main variable-volume chamber, a plurality of secondary variable-volume chambers, mechanicaily connected pistons in each chamber comprising one wall of each chamber, a breathing mask, conduit means connecting the breathing mask with the main variable-volume chamber and the main variable-volume chamber with the secondary variable-volume chambers, check valve means for allowing the passage of gas from the secondary variable-volume chambers into the main variable-volume chamber, a source of fresh breathing mixture, conduit means connecting the secondary variable-volume chambers to the source of fresh breathing mixture, controller means responsive to the pressure in one of the secondary variable-volume chambers for controlling the flow of fresh breathing mixture to said one secondary chamber when the pressure therein is lower than the ambient pressure, and means feeding the other of said secondary chambers with gas exhaled from the mask and with fresh breathing mixture in accordance with a predetermined ambient pressure, the ratio of said exhaled gas to said fresh breathing mixture in terms of volume increasing with an increase in ambient pressure. <CIT> describes a headset comprising: a mounting assembly adapted to be worn on a user's head; and a mask unit supported by said mounting assembly and including a mask body configured to cover at least the nose and mouth region of said user, said mask unit movable between a retracted position where the mask body is proximal to the crown of the user's head, and a deployed position where the mask body is adjacent said nose and mouth region, said mask unit including a gas delivery passageway operable to deliver breathable gas to the mask body when the mask body is in said deployed position thereof.

A similar concept to phased dilution is the application of an oxygen pulse at the beginning of the inhalation. However, pulse-dilution systems are associated with a fixed pulse bolus volume and therefore cannot adapt to variations in workload. Accordingly, the pulse-dilution system must be sized based on maximum workload at maximum intended operational altitude. When the user is at rest or the workload level is low, too much oxygen may be provided. Similarly, at high workload levels and high inhalation peak flows, pulse-dilution systems may fail to cover the full inhalation flow, resulting in dilution in the early phase of the inhalation cycle.

A breathing system incorporating a phased-dilution demand oxygen regulator (PDDOR; e.g., breathing regulator, cutoff device) is disclosed. In embodiments, the breathing system includes a pressurized oxygen source and a breathing mask worn by a user, the breathing mask connected to the oxygen supply via the PDDOR and covering at least the nose and mouth of the user. The PDDOR is connected to a dilution valve for supplying ambient air and a demand valve connected to the supply line, the demand valve controlling the oxygen supply into the supply line. The PDDOR maintains an interior control volume (CV) pressure. When the user begins to inhale through the breathing mask, commencing an inhalation cycle, the negative pressure signals the PDDOR and opens the demand valve. The PDDOR maintains sufficient CV pressure to keep the demand valve open and provide a pure oxygen supply to the breathing mask during an initial phase of the inhalation cycle as the CV pressure drops within. When the CV pressure drops below a lower threshold pressure. the main valve closes, cutting off the pure oxygen supply via the demand valve (and ending the initial demand phase). When the oxygen supply is cut off, the dilution valve unblocks to provide ambient air to the breathing mask.

In some embodiments, the PDDOR includes a pilot valve and one or more membranes configured for reducing the CV pressure by opening the pilot valve.

In some embodiments, the one or more membranes restore the interior CV pressure by closing the pilot valve at the conclusion of the inhalation cycle.

In some embodiments, the one or more membranes include a sensing membrane for receiving the pressure signal from the breathing mask.

In some embodiments, the one or more membranes include a pull membrane configured for closing the main valve.

In some embodiments, the pull membrane closes the main valve in conjunction with a main valve spring.

In some embodiments, the duration of the initial demand phase of the inhalation cycle varies according to the current air pressure and temperature.

In some embodiments, the breathing mask is an oronasal mask.

In some embodiments, the breathing mask is a full-face mask.

A method for regulating oxygen delivery to a user is also disclosed. In embodiments, the method includes receiving, via a breathing regulator, a pressure signal from a breathing mask, the pressure signal corresponding to the beginning of an inhalation cycle and the opening of a demand valve. The method includes providing a pure oxygen supply to the breathing mask via the open demand valve. The method includes reducing an interior control volume (CV) pressure within the breathing regulator. The method includes, when the CV pressure drops below a lower pressure threshold, cutting off the pure oxygen supply by closing a main valve within the breathing regulator. The method includes providing an ambient air supply to the breathing mask via a dilution valve when the oxygen supply is cut off.

In some embodiments, reducing the CV pressure includes opening a pilot valve of the breathing regulator.

In some embodiments, the method includes, when the inhalation cycle has concluded, restoring the CV pressure within the breathing regulator. The method includes, when the CV pressure exceeds an upper pressure threshold, preparing for the next inhalation cycle by opening the main valve.

In some embodiments, restoring the CV pressure includes closing the pilot valve and preparing for the next inhalation cycle by opening the main valve includes blocking the dilution valve via the main valve.

In some embodiments, the method includes providing the pure oxygen supply throughout an initial demand phase of the inhalation cycle.

Broadly speaking, a breathing system incorporating a phased-dilution demand oxygen regulator (PDDOR) is disclosed. The PDDOR allows for a significant reduction in complexity compared to standard pulse oxygen systems and provides better breathing coverage overall while conserving oxygen compared to demand dilution systems. Further, the PDDOR adapts to variations in workload as well as changes in altitude.

Referring now to <FIG>, a breathing system <NUM> is disclosed. In embodiments, the breathing system may be utilized by, e.g., parachutists or by aircraft pilots and crew working in high-altitude environments. The breathing system <NUM> may include a pressurized oxygen source <NUM> (e.g., oxygen cylinder), PDDOR <NUM> (e.g., breathing regulator, cutoff device), dilution valve <NUM>, demand valve <NUM>, and oronasal mask <NUM> worn by a user <NUM>.

In some embodiments, the breathing system <NUM> may be a conventional pulse system retrofitted with the PDDOR <NUM>.

In embodiments, the oronasal mask <NUM> may include a mask that covers just the nose and mouth of the user <NUM> (e.g., used in conjunction with goggles) or a full-face mask, as long as the user's nose and mouth are covered. For example, the PDDOR <NUM> may be connected to the oronasal mask <NUM> by a sensor line <NUM>, such that an inhalation by the user <NUM> may be detected by the PDDOR via the sensor line, e.g., as a negative differential pressure.

In embodiments, the dilution valve <NUM> provides ambient air to the user <NUM> through the oronasal mask <NUM> when in an open (e.g., unblocked) state. Similarly, the demand valve <NUM> is connected to the oxygen source <NUM> via the PDDOR <NUM>, supplying <NUM>% pure oxygen to the user <NUM> through the oronasal mask <NUM> when in an open state.

In embodiments, the breathing system <NUM> differs from and improves upon conventional pulse or demand systems by providing <NUM>% pure supplemental oxygen to the user <NUM> during an initial demand phase of each inhalation cycle, in precise alignment with the inhalation flow. For example, the PDDOR <NUM> may detect the start of an inhalation cycle via the sensor line <NUM>. The initial demand phase starts with the inhalation cycle, when the demand valve <NUM> is opened by inhalation pressure; pure oxygen may flow from the oxygen source <NUM> through the PDDOR <NUM> and the open demand valve <NUM> into the oronasal mask <NUM> as pressure decreases within the PDDOR.

In embodiments, while the control volume (CV) pressure drops within the PDDOR <NUM>, the PDDOR may maintain sufficient CV pressure to keep the demand valve <NUM> open throughout the initial demand phase. For example, when the control volume (CV) pressure drops to a sufficiently low level, the initial demand phase may conclude. The demand valve <NUM> may close, cutting off flow from the oxygen source <NUM> (e.g., except for any oxygen remaining within the PDDOR <NUM>). Concurrently (e.g., or slightly before, to preserve flow to the oronasal mask <NUM>, the dilution valve <NUM> may unblock or open to permit the flow of ambient air to the oronasal mask <NUM>. At the end of the inhalation cycle, pressure within the PDDOR <NUM> may rise in preparation for the next inhalation cycle.

Referring to <FIG>, the PDDOR <NUM> is shown in a standby mode prior to the start of an inhalation cycle. The PDDOR <NUM> may include a main valve <NUM> (e.g., including supply membrane 202a (e.g., main membrane) and main valve spring 202b), sensing membrane <NUM>, pull membrane <NUM>, and pilot valve <NUM> set into a decay orifice <NUM>.

In embodiments, the main valve <NUM> may begin an inhalation cycle in an open state, while the sensing membrane <NUM> may be in a closed state. Inhalation flow on the part of the user (<NUM>, <FIG>) may result in a negative differential pressure within the oronasal mask <NUM> (which also opens the demand valve <NUM>). The negative differential pressure may be detected on the sensor line <NUM> as a pressure signal which triggers a process within the PDDOR <NUM> that closes off the oxygen supply pressure <NUM> from the oxygen source <NUM> (e.g., through the open demand valve <NUM>) after an initial demand phase concludes (e.g., ~<NUM> after the commencement of the inhalation cycle; as noted below, the precise duration of the initial demand phase may vary according to temperature and pressure conditions). The pressure signal corresponding to the negative pressure differential may be detected by the sensing membrane <NUM>, which opens the pilot valve <NUM>; consequently, CV pressure within the PDDOR <NUM> may begin to drop from the peak (e.g., <NUM>-<NUM>%) shown by <FIG> while the dilution valve (<NUM>, <FIG>) remains blocked. However, as noted above, the PDDOR <NUM> may maintain sufficient CV pressure that the demand valve <NUM> remains open throughout the initial demand phase, providing a full oxygen supply from the oxygen source <NUM>. In some embodiments, the drop in CV pressure within the PDDOR <NUM> may be triggered by nonmechanical means other than the pilot valve <NUM>, e.g., electronic or electromagnetic controls.

Referring also to <FIG>, the PDDOR 104a may be implemented and may function similarly to the PDDOR <NUM> of <FIG>, except that within the PDDOR 104a (e.g., <NUM>-<NUM> after the start of the inhalation cycle) CV pressure may continue to fall (e.g., to around <NUM>%, or a closing pressure at <NUM> barg vs. an initial pressure at <NUM> barg), causing the pull membrane <NUM> to pull the supply membrane 202a from its open position (<NUM>) and closing the supply membrane 202a via hysteresis (assisted by the main valve spring 202b) cutting off the flow from the oxygen source <NUM> to the demand valve <NUM> as the pilot valve <NUM> remains open.

In embodiments, any remaining oxygen under pressure within the PDDOR 104a may be inhaled by the user <NUM>. For example, concurrently with, or just before, the CV pressure within the PDDOR 104a deceeds (e.g., drops below) a lower threshold level, the dilution valve <NUM> may unblock, allowing ambient air to take over the inhalation flow supply (in addition to any leak flow through the still-open pilot valve <NUM>) and maintaining a continuous uninterrupted flow (e.g., oxygen/oxygen + ambient air/ambient air) to the user <NUM> through the oronasal mask <NUM>. For example, the dilution valve <NUM> may be associated with a maximum opening pressure just below the minimum supply pressure of the demand valve <NUM>. Accordingly, the dilution valve <NUM> may unblock just before the closing of the demand valve <NUM>. In embodiments, the maximum opening pressure of the dilution valve <NUM> and the minimum supply pressure of the demand valve <NUM> may be configured to minimize the period of overlap between the opening of the dilution valve and the closing of the demand valve. In some embodiments, the PDDOR <NUM>, 104a may include a bypass valve <NUM> allowing manual switching (e.g., by the user <NUM>) between full-oxygen and dilution (e.g., ambient air) modes.

In embodiments, the pilot valve <NUM> may close at the end of the inhalation cycle, causing CV pressure within the PDDOR 104a to rise. When the CV pressure exceeds an upper threshold level, the main valve <NUM> may reopen (as shown by <FIG>) in preparation for the next inhalation cycle.

In some embodiments, the PDDOR <NUM>, 104a may further include mechanical or electronic means (e.g., motor-driven, altitude-dependent/barometric) of presetting or controlling the cutoff time and thus the duration of the initial demand phase.

Referring to <FIG>, the graph <NUM> may plot inhalation flow (<NUM>; e.g., in liters per minute) and inspiration volume (<NUM>; e.g., in liters) over time (<NUM>; e.g., in seconds).

In embodiments, the start of an inhalation cycle (<NUM>) at time zero results in a pressure signal received within the PDDOR (<NUM>, <FIG>; e.g., by the sensing membrane (<NUM>, <FIG>)), causing the demand valve (<NUM>, <FIG>) to open and CV pressure within the PDDOR to drop (e.g., from its approximate peak; e.g., due to the opening of the pilot valve (<NUM>, <FIG>)). For example, the flow of oxygen <NUM> from the oxygen source (<NUM>, <FIG>) to the oronasal mask (<NUM>, <FIG>) may track substantially with the inhalation flow <NUM> during an initial demand phase which concludes when the CV pressure within the PDDOR <NUM> drops below a lower threshold pressure.

In embodiments, around <NUM> after the start of the inhalation cycle, the CV pressure drops sufficiently (e.g., around <NUM>%) to close the main valve (<NUM>, <FIG>), and thereby blocking the demand valve <NUM> (<NUM>), concluding the initial demand phase and cutting off the flow of oxygen <NUM> (e.g., from the oxygen source (<NUM>, <FIG>)). The closing of the demand valve <NUM> may occur immediately after, or concurrently with, the unblocking of the dilution valve (<NUM>, <FIG>). For example, the flow of oxygen <NUM> may trail off as any remaining oxygen within the PDDOR (104a, <FIG>) is inhaled by the user (<NUM>, <FIG>), e.g., along with ambient air provided through the dilution valve <NUM>. When the remaining oxygen is inhaled (<NUM>; e.g., ~<NUM> after the start of the inhalation cycle), the airflow into the oronasal mask <NUM> may consist of ambient air only, plus any leak flow through the still-open pilot valve (<NUM>, <FIG>).

In embodiments, the inhalation cycle may conclude with the closing (<NUM>) of the pilot valve <NUM> (e.g., ~<NUM> seconds after the start of the inhalation cycle). For example, inhalation flow <NUM> may drop to zero, closing the pilot valve <NUM> and restoring CV pressure within the PDDOR 104a.

In embodiments, after the pilot valve <NUM> closes (e.g., ~<NUM> after the conclusion (<NUM>) of the inhalation cycle), CV pressure within the PDDOR <NUM> has risen to a sufficiently high level (e.g., around <NUM>%) to exceed the upper threshold pressure and reopen (<NUM>) the main valve <NUM> in preparation for the next inhalation cycle. It should be noted that the timing and/or duration of the initial demand phase may be pressure-driven and thus may vary with altitude and temperature, as described in more detail below.

Referring to <FIG>, the graph <NUM> may plot inhalation flow 302a-d over time <NUM>. The inhalation flows 302a-d and flow of oxygen 212a, 212d may be implemented and may function similarly to the inhalation flow <NUM> and flow of oxygen <NUM> of <FIG>, except that the rate of inhalation flow 302a-d may vary according to workload. For example, the rate of inhalation flow 302a may correspond to a nominal workload of <NUM> W/kg, and the rates of inhalation flow 302b-d to gradually increasing workloads of <NUM> W/kg, <NUM> W/kg, and <NUM> W/kg respectively.

In embodiments, the control times and operations of the PDDOR (<NUM>, <FIG>) may depend on gas density, and therefore may adapt to changes in absolute pressure (e.g., altitude) and air temperature as well as changes in workload. For example, the inhalation flows 302a-d may correspond to a nominal pressure and temperature, e.g., ground level (<NUM> ft AGL) and <NUM>° C. In each case, the flow of oxygen 212a, 212d may substantially track with the inhalation flow 302a-d throughout an initial demand phase, e.g., of ~<NUM> after the start of the inhalation cycle. Under these conditions the total oxygen volume dispensed (e.g., tidal volume) may increase as workload increases, while the initial demand phase concludes sooner as workload increases (e.g., <NUM> over <NUM>-<NUM> (at the nominal workload, inhalation flow 302a) to <NUM> over <NUM>-<NUM> (at the elevated workload of <NUM> W. kg, 302d)).

Referring also to <FIG>, the graph 400a and the inhalation flows 302e-h may be implemented and may function similarly to the graph <NUM> and the inhalation flows 302a-d of <FIG> and their respective corresponding workloads, except that the inhalation flows 302e-h may correspond to a higher altitude (e.g., <NUM>,<NUM> ft AGL) and lower air temperature (e.g., -<NUM>° C). While the flow of oxygen 212e-h still tracks with the inhalation flow 302e-h throughout the initial demand phase at the higher altitude (and lower temperature and pressure) while the volume of oxygen dispensed remains relatively consistent with the applicable workload, the main valve (<NUM>, <FIG>) remains open for a longer duration (e.g., <NUM>-<NUM> at the nominal workload (inhalation flow 302e) to <NUM>-<NUM> at the elevated workload (inhalation flow <NUM>)). Because the PDDOR <NUM> adapts inherently to changes in altitude, the breathing system <NUM> may be configured for a relatively low basic value for pure oxygen dosing time (e.g., the initial demand phase) and may provide for a potential switch altitude (e.g., from <NUM>% pure oxygen to saving mode) above current levels (e.g., ~<NUM>,<NUM> ft).

In embodiments, given the tidal volumes and cutoff times described above, average oxygen concentrations may be slightly above minimum (e.g., as defined by SAE <NUM> standards for oxygen equipment for aircraft). However, the phased-dilution supply mode of the PDDOR <NUM> operates more efficiently than would a constant-dilution mode and may achieve efficient blood saturation at comparatively reduced oxygen dosing levels as compared to current systems, which may be retrofitted with the PDDOR <NUM> for improved performance with reductions in oxygen consumption and system complexity.

Referring to <FIG>, a method of operation <NUM> may be implemented via the breathing system <NUM> (including a breathing regulator, e.g., the PDDOR <NUM>) and may include the following steps.

At a step <NUM>, the breathing regulator receives a negative pressure signal from a breathing mask (e.g., oronasal or full-face) worn by a user, signaling the beginning of an inhalation cycle. For example, the user may inhale through the breathing mask, initiating the negative pressure signal and generating sufficient pressure to open the demand valve coupled to the oxygen supply. The pressure signal may also indicate the beginning of the initial demand phase within the inhalation cycle.

At a step <NUM>, the breathing regulator provides a full oxygen supply to the user through the breathing mask via the open demand valve. For example, the full oxygen supply may be provided throughout the initial demand phase of the inhalation cycle while the demand valve remains open.

At a step <NUM>, the breathing regulator reduces control volume (CV) pressure within the breathing regulator. For example, a pilot valve may open substantially concurrently with the beginning of the inhalation cycle, such that CV pressure gradually drops throughout.

At a step <NUM>, when the CV pressure is sufficiently reduced to deceed the lower threshold pressure (e.g., <NUM>% of maximum) the pure oxygen supply is cut off by closing a main valve of the breathing regulator. For example, the closing of the main valve may block the flow of pure oxygen to the demand valve.

At a step <NUM>, the breathing regulator provides an ambient air supply (e.g., which may include any residual oxygen remaining in the breathing regulator or in the supply line to the breathing mask) by opening a dilution valve. For example, as the CV pressure approaches the lower threshold pressure where the main valve closes, blocking the demand valve, the dilution valve may open to maintain a continuous uninterrupted flow to the breathing mask.

The method <NUM> may include additional steps <NUM> and <NUM>. At the step <NUM>, after the inhalation cycle ends, the breathing regulator restores the CV pressure. For example, the pilot valve may be closed, causing the CV pressure to increase within the breathing regulator) in preparation for the next inhalation cycle.

Claim 1:
A breathing system (<NUM>) incorporating a phased-dilution demand oxygen regulator (<NUM>), comprising:
at least one pressurized oxygen source (<NUM>);
a breathing mask configured to be worn by a user (<NUM>) and configured to cover a nose and a mouth of the user (<NUM>), the breathing mask coupled to the pressurized oxygen source (<NUM>) by at least one supply line;
a dilution valve (<NUM>) coupled to the supply line, the dilution valve (<NUM>) configured to provide a supply of ambient air to the breathing mask when open;
a demand valve (<NUM>) coupled to the at least one oxygen source (<NUM>) via the supply line;
and
the breathing regulator (<NUM>) coupled to the at least one supply line and to the at least one oxygen source (<NUM>), the breathing regulator (<NUM>) associated with a control volume pressure within the breathing regulator (<NUM>) and comprising at least one main valve (<NUM>), the breathing regulator (<NUM>) configured to:
<NUM>) receive at least one pressure signal from the breathing mask, the pressure signal corresponding to a) a start of an inhalation cycle, b) an initial demand phase of the inhalation cycle, and c) an opening of the demand valve (<NUM>);
<NUM>) provide a pure oxygen supply to the breathing mask via the open demand valve (<NUM>) throughout the initial demand phase;
<NUM>) when the control volume pressure deceeds a lower threshold pressure, cutting off the pure oxygen supply by closing the main valve (<NUM>);
<NUM>) when the main valve (<NUM>) closes, provide the ambient air supply to the breathing mask via the dilution valve (<NUM>);
and
<NUM>) when the control volume pressure exceeds an upper threshold, reopen the main valve (<NUM>) in preparation for a next inhalation cycle.