Patent Publication Number: US-2022219022-A1

Title: Pulsed oxygen delivery system and method for a closed breathing environment

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention is directed to a pulsed oxygen delivery system, and more particularly, to system and method for delivering a pulsed bolus of oxygen to the lungs of a user shortly after the start of inhalation in a closed breathing environment, such as, for example, a pressure suit worn by an astronaut that is required to support extravehicular activities outside of a spacecraft. 
     2. Description of Related Art 
     The pulsed delivery of supplemental oxygen to a user by way of a phase-dilution mask offers known benefits in terms of oxygen utilization efficiency as compared with a continuous flow of oxygen or that sources from the ambient environment, that being administered either at ground level conditions or most notably in low partial pressure environments. These benefits are due to a controlled bolus of oxygen being delivered directly to the lungs shortly after the start of inhalation rather than regions that do not support diffusion of oxygen to the blood stream. In addition, the delivery of the bolus of oxygen in a low ambient pressure environment is such that the volume of oxygen expands significantly to more completely fill the user&#39;s lungs, as compared with normal respiration. Such an effect is particularly noticeable at pressures less than 5.45 psia or 25,000 ft. equivalent. 
     The pulsed dispensing of supplemental and therapeutic oxygen is therefore widely practiced in the commercial aviation industry where the weight and volume occupied by the oxygen storage and supply system are important considerations, as disclosed for example in U.S. Pat. No. 8,733,352. That said, it would be beneficial to provide a pulsed oxygen delivery system for use in a closed breathing environment such as, for example, in a pressure suit worn by an astronaut performing extravehicular activity outside of a spacecraft. 
     SUMMARY OF THE DISCLOSURE 
     The subject invention is directed to a new and useful pulsed oxygen delivery system for a closed breathing environment, a source of gaseous oxygen, a phase dilution type oronasal dispensing mask worn by a user in a closed breathing environment defined by a pressure suit, and a pulse control module for delivering a timed and metered bolus of oxygen from the source of gaseous oxygen to the oronasal dispensing mask upon demand by the user (i.e., shortly after the start of inhalation). 
     The pulse control module includes a pressure manifold having one or more breath sensors for sensing a breath taken by the user and one or more control valve for controlling the duration and amount of oxygen delivered to the dispensing mask. The source of gaseous oxygen includes a pressurized single use storage vessel or a refillable storage vessel, an initiator or mechanical valve for activating or otherwise establishing the flow of oxygen from the storage vessel and a regulator for managing the delivery of oxygen from the storage vessel to the pressure manifold. 
     The storage vessel includes a manifold body defining a first flow passage containing a frangible rupture disc, and the initiator includes an initiator body defining a second flow passage in fluid communication with the first flow passage. Means are provided for rupturing the rupture disc to initiate the flow of oxygen from the storage cylinder to the dispensing mask by way of a supply tube. 
     In one embodiment of the invention, the means for rupturing the rupture disc includes an initiator lance and a pyrotechnic charge for causing the lance to rupture the disc. Alternatively the means for initiating the flow of oxygen could be a mechanical or spring-loaded lance, or the storage vessel could include an oxygen supply valve that is manually or electrically moved from a closed positon to an open positon to initiate the flow of oxygen from the storage vessel. Preferably, the flow of oxygen from the storage vessel is initiated upon the sensing of a valid first breath by the breath sensor, and in the absence of a valid first breath the initiator is activated manually by the application of electrical power. 
     The pulse control module includes a microcontroller unit that is in communication with the pressure manifold, the source of gaseous oxygen and the pressure suit over an electronic interface. The microcontroller unit is programmed to monitor suit pressure and temperature, manifold pressure and temperature, and storage vessel pressure and temperature. The microcontroller unit is further programmed to manage the initiator or state of the oxygen supply valve, the one or more control valves and the one or more breath sensors. Preferably, the pulse control module is powered by primary and secondary power supplies that are isolated and protected from one another. 
     The subject invention is also directed to a method for delivering pulsed oxygen to an enclosed oxygen pressurized breathing environment, which involves providing a source of gaseous oxygen, connecting the source of gaseous oxygen to a phase dilution type oronasal dispensing mask worn by a user in a closed breathing environment defined by a pressure suit, and delivering a controlled bolus of oxygen from the source of gaseous oxygen to the oronasal dispensing mask upon demand by the user. Preferably, the controlled bolus of oxygen is delivered shortly after the start of inhalation. 
     It is envisioned that bolus volume can be controlled in one or more ways. For example, bolus volume could be controlled according to ambient pressure within the pressure suit, bolus volume could be controlled according to oxygen supply pressure and temperature, and/or bolus volume could be controlled according to a user&#39;s level of oxygen blood saturation. 
     Bolus volume could also be controlled so as to maintain a user&#39;s level of oxygen blood saturation in a target range equal to or greater than a defined baseline percentage specific to the user, so as to optimize the volume of oxygen that is required to be dispensed, as disclosed for example in commonly assigned U.S. Patent Application Publication No. 2015/0174359, the disclosure of which is incorporated herein by reference. In this regard, the level of blood oxygen saturation could also be measured by an oximeter or similar means and that information could be sent to the microcontroller unit to control the bolus of oxygen delivered to the user. 
     These and other features of the pulsed oxygen delivery system and method of the subject invention will become more readily apparent to those having ordinary skill in the art to which the subject invention appertains from the detailed description of the preferred embodiments taken in conjunction with the following brief description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those having ordinary skill in the art will readily understand how to make and use the pulsed oxygen delivery system of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to the figures wherein: 
         FIG. 1  is a perspective view of a pressure suit defining a closed breathing environment with which the pulsed oxygen delivery system of the subject invention is employed; 
         FIG. 2  is a schematic representation of the pulsed oxygen delivery system of the subject invention; 
         FIG. 3  is a perspective view of the oxygen supply assembly shown in  FIG. 1 ; 
         FIG. 4  is an enlarged cross-sectional view of the initiator assembly taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is an enlarged cross-sectional view of the manifold and pressure regulator assembly taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a perspective view oxygen controller assembly shown in  FIG. 1 ; 
         FIG. 7  is a functional block diagram of the oxygen controller assembly with system interfaces; and 
         FIG. 8  is a perspective view of phase dilution type oronasal dispensing mask utilized in conjunction with the pulsed oxygen delivery system of the subject invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals identify similar structural features or elements of the subject invention, there is illustrated in  FIG. 1  a closed system breathing environment in the form of a pressure suit  10  with which the pulsed oxygen delivery system  100  of the subject invention is employed. The pressure suit  10  is of the type worn by an astronaut performing extravehicular activities outside of a spacecraft. 
     As discussed in more detail below with reference to  FIG. 2 , the pulsed oxygen delivery system  100  includes a source of gaseous oxygen  200 , an oronasal dispensing mask (i.e., a phase dilution mask)  300  worn by a user in the closed breathing environment defined by pressure suit  10 , and a pulse control module  400  for delivering a timed and metered bolus of oxygen from the source of gaseous oxygen  200  to the oronasal dispensing mask  300  upon demand by the user. Those skilled in the art will readily appreciate that the oronasal mask  300  includes an oral-nasal face piece, inhalation and exhalation valves, and a flexible supply tube that connects the mask  300  to the pulse control module  400 , as described in more detail below with reference to  FIG. 8 . 
     The pulsed oxygen delivery system  100  is adapted and configured to respond to inhalation by delivering a precisely metered bolus volume (pulse) of oxygen directly to the lungs by way of mask  300  shortly after the start of inhalation in preference to regions that do not support diffusion of oxygen to the blood stream. As discussed in more detail below, this bolus volume of oxygen can be varied according to suit pressure conditions or in direct response to actively measured blood oxygen (pulse) saturation SpO 2  levels of the user. The efficiency of the system depends on delivering the pulse early in the inhalation cycle. In order to maintain this level of efficiency, it is important to ensure that the inhalation is detected and pulse delivered in a reliable and timely manner. 
     Referring now to  FIG. 2  in conjunction with  FIG. 6 , the pulse control module  400  is adapted and configured to perform monitor and control function by way of a microcontroller unit (MCU)  420 , which includes an electronics package that employs software. It resides on a circuit board  425  that is preferably manufactured from fiberglass reinforced epoxy, where the circuitry is silk-screened using a solder mask that is conformally coated. The circuit board  425  includes a programmable port  428  for uploading instructions and data to the MCU  420 . 
     The pulse control module  400  further includes a pressure manifold  410  and an electronic microcontroller unit  420 . The pressure manifold  410  includes a manifold housing  460  that acts as a plenum on the circuit board  425  for distributing oxygen to the user. The manifold housing  460  has an inlet  462  for receiving oxygen from the supply source  200  and a pair of outlet fittings  464   a ,  464   b  for communicating with the oronasal mask  300  by way of associated tubing. 
     The pressure manifold  410  further includes a pair of breath sensors  412   a ,  412   b , which act as a vacuum pressure switches for sensing a breath taken by the user, and a pair of solenoid control valves  414   a ,  414   b  for controlling the duration and amount of oxygen delivered to the dispensing mask. Inhalation demand is sensed by the breath sensors  412   a ,  412   b  as a small differential pressure in the supply tube created by inhaling through the mask  300 . The solenoid control valves  414   a ,  414   b  are characterized as 2-way, normally closed with a nominal 20 ms on-off response time. The paired breath sensors and control valves provide for parallel redundant operation of the system. 
     The effective bolus volume is determined by the duration that the dispensing solenoid valve  414   a ,  414   b  is open. Upon sensing a breath, the controller  400  opens the solenoid valve  414   a ,  414   b  to provide a small, metered pulse of oxygen. The controller  400  meters the quantity of oxygen by adjusting the duration that the valve is powered open. This duration is calculated based on the results of a series of equations or by a look up table that reflects the characteristics and response of the dispensing system, but is controlled based on the current suit pressure or the user&#39;s SpO 2  levels. 
     With continuing reference to  FIGS. 2 and 6 , the oxygen control module  400  employs a board mounted solid state MEMs absolute pressure sensor  416  to determine suit pressure and temperature. The pressure measurement is compensated in software for sensor specific coefficients and offsets that are pressure and temperature dependent. In the absence of valid data from the suit pressure sensor  416 , the system defaults to a pre-defined pulse duration basis (IPW). 
     Manifold gas temperature and absolute pressure is monitored by an integrated circuit sensor  415  that is mounted on the controller printed circuit board  425 . A sensing port  417  in the pressure manifold  410  transmits manifold gas directly to that sensor. An LED status indicator array  418  is integrated into the controller board  425 , which illuminates to indicate that a breath was taken on the mask  300  and oxygen was dispensed to that mask. 
     Referring now to  FIG. 2  in conjunction with  FIG. 3 , the source of gaseous oxygen or oxygen supply assembly  200  provides a means by which high pressure oxygen is maintained for supply at a regulated pressure that is less than storage pressure. It includes a pressurized single use storage vessel  212 , an initiator  214  for activating the flow of oxygen from the storage vessel and a regulator  216  for managing the delivery of oxygen from the storage vessel  212  to the pressure manifold  410 . The initiator  214  communicates with the MCU  420  by way of a connector  454  on circuit board  425  shown in  FIG. 6   
     The storage vessel  212  is preferably a non-refillable, single use device, which may be manufactured from a welded stainless steel liner that is structurally supported by a Carbon Fiber Epoxy composite wrapping that is intended to be resistant to outgassing in a persistent low ambient pressure environment. The breathing gas contained in the storage vessel  212  is preferably an oxygen/helium mixture comprising 99.5% oxygen and between 0.25% and 0.50% helium. The helium is used as a challenge gas to perform acceptance leakage tests that verifies the seal between the initiator  214  and the storage vessel  212 . The resulting breathing gas mixture provides satisfactory supplemental oxygen for hypoxia protection. 
     As best seen in  FIG. 5 , pressure regulation is provided by a mechanical single stage piston type regulator  216 . The inlet of the regulator  216  is protected by a porous sintered bronze filter  234 , and pressure is regulated by way of an aluminum piston  236  under the bias of a stainless steel spring  238  and sealed by an O-ring  240 . 
     Referring to  FIGS. 3 and 4 , storage vessel  212  includes a manifold body  218  attached to the inlet of regulator  216 . The manifold body  218  includes a dedicated fill port  215  (see  FIG. 3 ) for filling the vessel  212  with the breathing mixture and defines a first flow passage  220  containing a frangible rupture disc  222 . The initiator  214  includes an initiator body  224  defining a second flow passage  226  in fluid communication with the first flow passage  220 . A mechanism is provided for rupturing the rupture disc  222  to initiate the flow of oxygen from the storage vessel  212  by way of a flexible low pressure supply tube  250  made from polyurethane or the like. 
     As shown in  FIG. 4 , in a preferred embodiment of the subject invention, the mechanism for rupturing the rupture disc  222  includes a tapered brass initiator lance  228  and a pyrotechnic actuator  230  for causing the lance  228  to rupture the disc. Upon sensing a valid first breath, the pulse control module  400  applies power to the pyrotechnic actuator  230  in the high pressure manifold  218 . The electrical detonation of the pyrotechnic actuator  230  of the initiator  214  propels the lance  228  to penetrate the rupture disc  222 . In the event of an overpressure discharge from the rupture disc  222 , the oxygen discharge is directed through a discharge port  232  in the manifold body  218 . 
     Alternatively the mechanism for initiating the flow of oxygen could be a mechanical or spring loaded-lance, or the storage vessel  212  could include a mechanical or solenoid operated valve that is mechanically or electrically moved from a closed positon to an open positon to initiate the flow of oxygen from the storage vessel  212 . Preferably, the flow of oxygen from the storage vessel  212  is initiated upon the sensing of a valid first breath by the breath sensor, and in the absence of a valid first breath the initiator  214  is activated. 
     More particularly, during the activation of the initiator  214 , the control module  400  monitors the electrical resistance of the initiator bridge circuit as a means of verifying whether the initiator  214  has been fired successfully. If the control module  400  determines that the initiator has not been fired, the control module  400  will continue to attempt to activate a further 2 times at 5 seconds intervals, after which the initiator  214  is activated by the application of electrical power. 
     Referring now to  FIG. 2  in conjunction with  FIG. 7 , the microcontroller unit  420  of pulse control module  400  is in electronic communication with the pressure manifold  410 , the source of gaseous oxygen  212  and the pressure suit  10  over an electronic interface  500 . The microcontroller unit  420  is programmed to monitor the suit pressure and temperature sensor  415 , manifold pressure and temperature sensor  416 , and storage vessel pressure and temperature sensor  225 . The microcontroller unit  420  is further programmed to manage the initiator  214  and the initiator drivers circuit  442 , the BIT and mask LEDs  418 ,  424  and the LED drivers  444 , the breath sensors  412   a ,  412   b  and the control valves  414   a ,  414   b  and valve driver circuit  446 . An electronic interface  445  (e.g., CAN BUS) provides communication between the microcontroller  420  and the pressure suit  10  to exchange data specific to functional test and reporting requirements (e.g., for suit maintenance and health). 
     The pulse control module  400  is powered continuously by primary and secondary 28 VDC power supplies  450   a ,  450   b , although other voltages could be used. Preferably, power supplies  450   a ,  450   b  are isolated and protected from one another by way of an input power sense and conditioning circuit  455  monitored by the MCU  420 . Moreover, each power input is transient suppression protected and diode isolated to support segregation requirements at the suit level. These supplies are configured such that any combination of inputs can be used to provide electrical power to the controller  420  by way of a power connector  452 , shown in  FIG. 6 . 
     The oxygen supply system  100  further includes a Built-In-Test (BIT) functionality. In the event that a valid first breath is not detected in the first 15 seconds after power is applied to the oxygen control module  400  (it is normally unpowered), the oxygen control module  400  will perform a BIT to verify, where feasible, functional aspects of the control module  400  relative to its intended use and operation. If a valid breath is sensed at any time thereafter, the control module  400  will respond by proceeding to activate the initiator  214  to start the flow of oxygen to the pressure manifold  410  of the control module  400 . If the supply of oxygen is not controlled by the initiator  214  but using a mechanical or electrical valve, the control module  400  will either signal to electrically open the valve based on the sensing of a valid breath, or act on the presence of oxygen in the case of a mechanical valve. A BIT indicator  424  is provided on the printed circuit board  425 , which is illuminated in response to the outcome of the test and it send a message via the CAN connector  426  to report on the condition of the oxygen supply system  100 . 
     The subject invention is also directed to a method for delivering pulsed oxygen to a closed breathing environment, which involves providing a source of gaseous oxygen  200 , connecting the source of gaseous oxygen to a phase dilution type oronasal dispensing mask  300  worn by a user in a closed breathing environment defined by a pressure suit  10 , and delivering a controlled bolus of oxygen from the source of gaseous oxygen  200  to the oronasal dispensing mask  300  upon demand by the user, wherein the controlled bolus of oxygen is delivered shortly after the start of inhalation. 
     A phase dilution type oronasal dispensing mask  300  is illustrated in  FIG. 8  and it includes a conically shaped mask  312  that provides a comfortable seal against the user&#39;s nose, cheek and chin areas. The mask  312  is fed by a flexible supply tube  314  that communicates with the control module  400 . The mask  312  includes an inhalation valve  316 , which supports the inhalation phase of the breathing cycle and an exhalation valve  318 , which supports the exhalation phase of the breathing cycle. 
     It is envisioned that bolus volume can be controlled in one or more ways. For example, bolus volume could be controlled according to ambient pressure within the pressure suit, bolus volume could be controlled according to oxygen supply pressure and temperature, and/or bolus volume could be controlled according to a user&#39;s level of oxygen blood saturation. Bolus volume could, in addition, also be controlled so as to maintain a user&#39;s level of oxygen blood saturation in a target range equal to or greater than a defined baseline percentage specific to the user, so as to optimize the volume of oxygen that is required to be dispensed, as disclosed in U.S. Patent Application Publication No. 2015/0174359. In this regard, the level of blood oxygen saturation could also be measured by an oximeter or similar means and that information could be sent to the microcontroller unit to control the bolus of oxygen delivered to the user. 
     In situations where the user&#39;s measured SpO 2  is available as a control input, the oxygen controller  400  employs an operation mode pulse-width look-up table stored in non-volatile memory (NVM) resident in the microprocessor  420 . The pulse-width look-up table is indexed such that each SpO 2  entry received represents an increment reflecting the desired SpO 2  baseline specific to the user. The oxygen controller  400  activates the solenoid valve  414   a ,  414   b  for the pulse-width duration determined from the look-up table value corresponding to the index defined from the SpO 2  index value received by CAN bus  445 . Those skilled in the art will readily appreciate that the paired solenoid valves  414   a ,  414   b  are provided for parallel redundancy. In use, only one valve is needed, while the other remains as a “hot” spare if needed. 
     Compared with unassisted breathing from an ambient oxygen environment, as is the case in current suit systems, the utilization of a pulse delivery of oxygen as disclosed herein is seen as an opportunity to provide the following benefits: offset or improve upon any existing oxygen partial pressure deficiency relative to ground conditions; require less oxygen to be carried to support breathing/workload requirements compared with the current approach; and lower suit pressures which may as a result have a corresponding benefit of reducing physical workload thus leading to a reduction in heat generated and CO 2  produced by the occupant that must be accounted for by the environmental control systems and thus, achieve as a result a corresponding reduction in oxygen fire hazard and risk within the suit where the flammability of fuel-like materials is a function of oxygen pressure. 
     While the subject disclosure has been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.