Patent Publication Number: US-2021187230-A1

Title: Oxygen-capnography mask for continuous co2 monitoring

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/670,877 filed Aug. 7, 2017, which claims the benefit of U.S. Provisional Patent Application No. 62/373,170, entitled “OXYGEN-CAPNOGRAPHY MASK FOR CONTINUOUS CO 2  MONITORING,” filed Aug. 10, 2016, which is herein incorporated in its entirety for all purposes. 
    
    
     FIELD 
     The present disclosure relates to face masks for delivering oxygen to, and monitoring gases (e.g., carbon dioxide) exhaled from, a patient and, more particularly, to a face mask that impedes dilution of an exhaled gas by a delivered gas, and vice versa. 
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     A human respiratory cycle includes a sequence of events during which a human inhales and exhales a given volume of air through the respiratory system. The respiratory system includes the lungs that, during breathing, take in oxygen and expel carbon dioxide, a waste gas. An exchange of oxygen and carbon dioxide in the lungs can be evaluated, for example, by measuring oxygen saturation level in the blood and concentration of exhaled carbon dioxide. After carbon dioxide is exhaled, another respiratory cycle begins with the next breath. 
     Normal levels of both blood oxygen saturation and concentration of exhaled carbon dioxide can attest to the healthiness of the respiratory system. However, even if one&#39;s blood oxygen saturation level is normal, there may still be respiratory dysfunction that may be caused by the inability of body cells to use oxygen that is absorbed in the blood. In general, the higher the incompetence of body cells to exploit, the lower the level of the carbon dioxide produced by these cells and, consequently, the lower the concentration of the carbon dioxide that the subject exhales. 
     Face masks for subjects suffering from, prone to, or susceptible to breathing problems typically include an oxygen port for delivering oxygen to a subject at a designated rate and a carbon dioxide port for sampling exhaled carbon dioxide. Conventional masks that include the two ports have some drawbacks. One drawback is that the sampled carbon dioxide gas is diluted by the oxygen gas flow, which has to be delivered to the subject continuously. Diluting the carbon dioxide gas by the oxygen (or by any other gas for that matter) decreases. Another drawback of conventional face masks is that the carbon dioxide sampling port is distant from the subject&#39;s nose and mouth, which may also detrimentally affect the carbon dioxide concentration measurement due to, for example, the flow dispersion pattern of the exhaled CO 2 . Another drawback of conventional face masks is that the carbon dioxide sampling port has to stay in a same position relative to the subject&#39;s nose and mouth in order to have a reliable CO 2  concentration measurement. However, the carbon dioxide sampling port in conventional face masks is prone to movement due to movement of the subject&#39;s head. In addition, positioning a CO 2  sampling port within a stagnation space within the oxygen mask causes a re-breathing effect where, in some breathing regimens, the concentration level of the CO 2  near, or at, the sampling port may deviate from the actual end-tidal values. (In a capnogram, which is a CO 2  waveform displayed by a capnograph, an end-tidal CO 2  (EtCO 2 ) is the partial pressure of CO 2  at the end of an exhaled breath.). These drawbacks (to name a few) can result in an inaccurate measurement of the concentration of exhaled carbon dioxide.  FIG. 1  illustrates an example of a face mask  100  for monitoring exhaled CO 2  while administering oxygen. Face mask  100  typically includes latex-free soft medical grade resin  110  that makes the mask comfortable for subjects to wear. Mask  100  includes a face side  120  and a ‘tubing’ side  130 . Tubing side  130  includes an oxygen delivering port  140  via which oxygen can be administered to the mask wearer, and a CO 2  sampling port  150  via which CO 2  exhaled by the mask wearer can be monitored. 
     Carbon dioxide sampling port  150  has a longitudinal axis  152 . Patient&#39;s nose  160  has a longitudinal nostril axis  162 . CO 2  sampling port  150  (and also the adjacent oxygen port  140 ) is at an acute angle  170  relative to longitudinal nostril axis  162  such that CO 2  sampling port  150  and oxygen port  140  are placed between the nose ( 160 ) and mouth  170  of the patient. In such mask configuration neither CO 2  sampling port  150  nor oxygen port  140  is clearly aligned with any of nose  160  or mouth  170 . Indiscriminately placing CO 2  sampling port  150  and oxygen port  140  in the way shown in  FIG. 1  results in the drawbacks described above. 
     A slightly better solution is shown in  FIG. 2 , which shows a face mask similar to a face mask that is manufactured by MERCURY MEDICAL, a U.S. company manufacturing airway management devices. Referring to  FIG. 2 , mask  200  includes a ‘sit’, or ‘knee’,  210  that is oriented ( 220 ) approximately at a right angle relative to nostril orientation  230  of nose  240 . Mounting oxygen delivering port  250  and CO 2  sampling port  260  on sit/knee  210  of mask  200  better aligns them with nostril orientation  230 . (CO 2  sampling port  260  has an alignment  270  that forms an acute angle  280  with nostril orientation  230  that is smaller than acute angle  170  in  FIG. 1 .) However, mask  200  does not really solve the problems described above since mask  200  has issues similar to those related to mask  100  because CO 2  sampling port  260  is distant from the patient&#39;s mouth and nose. Therefore, at least in terms of exhaling carbon dioxide, neither of mask  100  and mask  200  is preferable over the other. 
     It would be beneficial to have a face mask that minimizes mutual interference between the two functions—delivering of oxygen to a subject and sampling of CO 2  exhaled by the subject. It would also be beneficial to have a face mask that is capable of measuring concentration of CO 2  with the same efficiency and accuracy independently of whether the subject breathes through his nose, mouth, or both. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     A face mask for delivering oxygen to, and sampling carbon dioxide exhaled from, a subject includes an internal partition wall (“IPW”) that divides the mask into a subject respiratory space (“SRS”) that primarily contains carbon dioxide exhaled by the subject, and a subject oxygen reservoir (“SOR”) space that primarily contains oxygen. The partition wall includes one or two holes to which naris conduits are respectively connected. The naris conduit(s) is(are) positioned in proximity to the subject&#39;s nares to closely obtain carbon dioxide samples. The naris conduits are configured such that they enable oxygen to flow from the SOR space to the SRS during inhalation while quickly expelling traces of CO 2 , and such that exhaled CO 2  quickly fills up the naris conduits during exhalation while expelling oxygen traces back to the SOR Thus, forming a SRS in the mask prevents dilution of CO 2  during exhalation and, therefore, results in a more accurate measurement of CO 2  concentration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are illustrated by way of example in the accompanying figures with the intent that these examples not be restrictive. It will be appreciated that for simplicity and clarity of the illustration, elements shown in the figures referenced below are not necessarily drawn to scale. Also, where considered appropriate, reference numerals may be repeated among the figures to indicate like, corresponding or analogous elements. Of the accompanying figures: 
         FIG. 1  (prior art) shows an oxygen mask provided with a CO 2  sampling port; 
         FIG. 2  (prior art) illustrates an oxygen/capnography mask which is a variant of the oxygen mask of  FIG. 1 ; 
         FIG. 3A  illustrates an oxygen/capnography mask with an internal partition wall according to an example embodiment; 
         FIG. 3B  shows the internal partition wall of  FIG. 3A ; 
         FIG. 3C  shows a naris conduit according to an example embodiment; 
         FIG. 4A  shows an oxygen/capnography mask with small internal partition wall according to another example embodiment; 
         FIG. 4B  shows the internal partition wall of  FIG. 4A ; 
         FIG. 4C  illustrates a side-view of mask of  FIG. 4A ; 
         FIG. 5A  illustrates an oxygen/capnography mask with an internal partition wall that is laid over the patient&#39;s face according to another example embodiment; 
         FIG. 5B  shows the internal partition wall of  FIG. 5A ; 
         FIG. 6A  illustrates an oxygen/capnography mask with an internal partition wall according to yet another example embodiment; 
         FIG. 6B  shows the internal partition wall of  FIG. 6A ; 
         FIG. 7A  illustrates an oxygen/capnography mask with an internal partition wall according to still another example embodiment; 
         FIG. 7B  shows the internal partition wall of  FIG. 7A ; 
         FIG. 8  shows a perforated internal partition with naris conduits according to an example embodiment; 
         FIG. 9  shows a perforated internal partition without naris conduits according to another example embodiment; 
         FIG. 10A  illustrates an oxygen/capnography mask with an oxygen dispenser according to an example embodiment; 
         FIG. 10B  shows the oxygen dispenser of  FIG. 10A ; 
         FIG. 11A  illustrates an oxygen/capnography mask with an oxygen dispenser according to another example embodiment; 
         FIG. 11B  shows the oxygen dispenser of  FIG. 11A ; 
         FIG. 12A  illustrates an oxygen/capnography mask with an oxygen dispenser according to yet another example embodiment; 
         FIG. 12B  shows the oxygen dispenser of  FIG. 12A ; and 
         FIG. 13A  illustrates a naris conduit with a CO 2  sampling port according to example embodiments; 
         FIG. 13B  illustrates a naris conduit with a CO 2  sampling port according to example embodiments; and 
         FIG. 13C  illustrates a naris conduit with a CO 2  sampling port according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but may nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The oxygen mask subject of the present disclosure includes a partition wall for operationally separate between the oxygen delivering function on the one hand, and the carbon dioxide sampling function on the other hand. as described in detail below, mask has a mask internal space and is configured to be laid over a face of a subject. The mask has an internal partition wall that is positioned inside the mask and defines, in the mask internal space, a subject respiration space (SRS) and a subject oxygen reservoir (SOR). In some embodiments, the internal partition wall may generally include a first naris conduit that extends from the inner partition wall into the SRS and into the SOR, and provides, through the internal partition wall, a bi-directional fluid flow channel between the SRS and the SOR. (When the mask is laid over the face of a subject, the first naris conduit is configured to be positioned in close proximity to the subject nares.) The internal partition wall may also include a first carbon dioxide conduit whose distal end is connected to the first naris conduit and is in fluid flow communication with an interior space of the first naris conduit. In other embodiments, the internal partition wall may also include a second naris conduit that extends from the inner partition wall into the SRS and into the SOR, and provides, through the internal partition wall, a bi-directional fluid flow channel between the SRS and the SOR. (When the mask is laid over the face of a subject, the first naris conduit is configured to be positioned in close proximity to the subject nares.) The internal partition wall may also include a second carbon dioxide conduit whose distal end is connected to the second naris conduit and is in fluid flow communication with an interior space of the second naris conduit. 
       FIG. 3A  shows a person  300  wearing a domed oxygen/capnography face mask  310  on her/his face  302  according to an example embodiment of the present invention. Mask  310  includes a dome (convex) shaped side having an apex  320  and an open side base  322  opposite to apex  320 . (The mask&#39;s open side, or mask&#39;s base,  322  is designed to fit snugly onto a patient&#39;s face, using a relatively soft seal for example.) Mask  310  includes a generally flat ‘oral-nasal’ internal partition wall (IPW)  330 . ( FIG. 3B  shows IPW  330  more clearly.) IPW  330 , which is positioned inside the domed mask  310  and fully covers the patient&#39;s nares and mouth, internally divides mask  310  into two spaces. One main space of mask  310  is referred to herein as a subject respiration space (SRS). The SRS is a mask space or cavity defined by or between IPW  330  and the mask&#39;s base  322  (and/or with subject&#39;s face  302 ) when mask  310  is laid over the subject&#39;s face. The other main space of mask  310  is referred to herein as a subject oxygen reservoir (SOR). The SOR is a mask space or cavity defined by or between IPW  330  and mask&#39;s apex  320 . 
     Mask  310  may include an oxygen port  340  to deliver oxygen to the patient, and a CO 2  port  350  to extract samples of the CO 2  exhaled by the patient. Oxygen port  340 , which may be a relatively short tube (e.g., two centimeters long), may be mounted anywhere on mask  310 , provided that it can fill up the subject oxygen reservoir (SOR) with oxygen, hence the term ‘oxygen reservoir’. Carbon dioxide port  350  is coupled to the subject respiration space (SRS) via a CO 2  tube  352  and corresponding tubing manifold. Structural constraints related to the location of CO 2  port  350  on mask  310  may be more lenient relative to the structural constraints related to the location of oxygen port  340  because CO 2  port  350  is connected to the naris conduits via a tubing system (e.g., via CO 2  conduits  381  and  383 ), so positioning of CO 2  port  350  is flexible, as opposed to oxygen port  340  whose positioning affects the mixing dynamics of the two gasses. 
     Mask  310  may also include an IPW adjustment mechanism to adjust the (and after the adjustment to maintain the adjusted) spatial location and orientation of IPW  330  in mask  310 , so that, when in use, IPW  330  is operationally maintained at an optimal distance from, and in optimal orientation with respect to, the patient&#39;s face in terms of breathing and CO 2  monitoring efficacy. The adjustment mechanism may be connected to IPW  330  and operable via a user (e.g., physician) through holes in mask  310 . By way of example, the gap adjustment mechanism may include three elongated adjustment rods or shafts  360 ,  362  and  364 . (Other numbers of adjustment rods or shafts may be used.) Mask  310  may include three external through holes  361 ,  363  and  365  through which adjustment rods or shafts  360 ,  362  and  364  may respectively be individually and independently pushed deeper into the mask (that is, pushed forward or closer to the patient&#39;s face), or pulled back (that is, away from the patient&#39;s face). Adjustment rods or shafts  360 ,  362  and  364  may be set such that IPW  330  is maintained at some distance from the face of the patient so that it does not touch the face. 
     Through holes  361 ,  363  and  365  and adjustment rods/shafts  360 ,  362  and  364  may be configured such that the lengthwise position of each adjustment rod or shaft in the respective through hole in mask  310  is maintained by a static friction force that exists between the rod or shaft and the hole. The friction force may, nevertheless, enable a user (e.g., physician) to adjust the lengthwise position of each rod or shaft by pushing the rod or shaft into the mask or pulling it back by applying a force that is large enough to overcome the static friction. Mask  310  may also include two pressure relief openings  370  and  372  that enable exhaled air with high CO 2  concentration flow to flow out of the mask due to slight overpressure that is produced by continues oxygen inflow, to thus prevent building up of excessive pressure inside the mask and rebreathing phenomena when a patient rebreathes part of a previously exhaled air with high CO 2  concentration. Of course, any other suitable adjustment mechanism may be used. 
     One naris conduit  380 , or two naris conduits  380  and  382 , may be mounted to, or through, IPW  330  and positioned in close proximity to the subject&#39;s nares when the mask is laid over the face of the subject. A naris conduit (e.g., naris conduit  380 ) may extend from IPW  330  into the SRS and into the SOR, to provide, through IPW  330 , a bi-directional fluid flow channel between the SRS and the SOR 
     Referring to  FIG. 3B , IPW  330  may include (e.g., by forming therein) three breathing openings: two ‘nares’ breathing openings (“NBOs”) that are positioned in close proximity to the patient&#39;s nares  384 , and a mouth breathing opening (“MBO”)  390  that is positioned in close proximity to the patient&#39;s mouth, when mask  310  is laid over the face of a subject. Two naris conduits (e.g., tubes)  380  and  382  are respectively mounted to the two NBOs. Each of naris conduits  380  and  382  passes through a respective opening in IPW  330  and extends outwardly from IPW  330  into the subject respiration space (SRS) and also into the subject oxygen reservoir (SOR), thus providing a bi-directional fluid flow channel between the SRS and the SOR, as described herein. Naris conduits  380  and  382  are ‘breathing conduits’ because they are used for both delivering oxygen to the patient and releasing (for extracting samples of) the CO 2  that the patient exhales. The way naris conduits  380  and  382  function is described in more detail below, for example in connection with  FIG. 3C . MBO  390  provides a passage between the SOR and the SRS, so that oxygen may freely pass from the SOR to the SRS. During exhalation through the mouth, a CO 2  conduit  392  may be used to extract CO 2  samples. Carbon dioxide conduit  392 , which may be positioned in a region near the mouth, is in fluid flow communication with the SRS. 
     A CO 2  extraction tubing system (“ETS”) is attached to IPW  330  in order to monitor CO 2  that is exhaled from the patient&#39;s nares and mouth. Depending on the number of naris conduits that the IPW includes (one naris conduit; e.g., naris conduit  380 , or two naris conduits; e.g., naris conduits  380  and  382 ), the CO 2 ETS may respectively include a first CO 2  conduit (e.g., CO 2  conduit  381 ) and a second CO 2  conduit (e.g., CO 2  conduit  383 ). A distal end of each CO 2  conduit is connected to a respective naris conduit such that it is in fluid flow communication with an interior space of that naris conduit. The distal end of the first CO 2  conduit (e.g., CO 2  conduit  381 ) may be positioned in close proximity to a first naris (one of patient&#39;s nares  384 ,  FIG. 3B ), and the distal end of the second CO 2  conduit (e.g., CO 2  conduit  383 ) may be positioned in close proximity to a second naris (the other naris of nares  384 ). In some other embodiments, the CO 2  ETS may also include CO 2  conduit  392  that has a distal end that is positioned in proximity to the patient&#39;s mouth (and in fluid flow communication with the SRS.) Each of CO 2  conduits  381 ,  382  and  392  has a proximal end that may be connected to a common CO 2  conduit  352  via a tubing manifold. (Carbon dioxide conduit  381 , CO 2  conduit  383  and CO 2  conduit  392  may be connected to the CO 2  port  350  via common conduit  352 ). 
     During use of mask  310 , oxygen is constantly provided to mask  310  via oxygen port  340 , and oxygen constantly fills up the SOR space inside mask  310 , ready to be inhaled by the patient. During inhalation, oxygen is delivered to the patient through naris conduits  380  and  382 , and also through mouth breathing opening (MBO)  390 . Most of the oxygen that is contained in mask  310  is contained in the oxygen reservoir part of the mask (in the SOR space), and it is readily available for the patient during inhalation. When the patient exhales CO 2  (CO 2  enriched air), the exhaled CO 2  quickly supersedes/displaces oxygen in the SRS part of mask  310 , and, in particular, the oxygen in nares conduits  380  and  382 , and the oxygen adjacent to the CO 2  conduit  392 . Since the volume of the spaces in nares conduits  380  and  382  and around the patient&#39;s mouth are relatively small (e.g., relative to an amount of oxygen and CO 2  exchange during one breath cycle), the exhaled CO 2  supersedes most, if not all, of the oxygen in these spaces quickly, thus preventing dilution of CO 2  and enabling a more reliable sampling of the exhaled CO 2 , and, therefore, a more reliable measurement of the concentration level of CO 2 . 
     Referring to  FIG. 3C , reference numeral  330 ′ is a symbolic representation of inner partition wall (IPW)  330  that separates between the SRS space and the SOR space. The description of naris conduit  380  also applies to naris conduit  382  (with CO 2  conduit  381  replaced with CO 2  conduit  383 ), as each of naris conduit  380  and naris conduit  382  is primarily intended for a different naris of the patient. ‘A naris conduit primarily intended for a particular naris’ means that a particular naris conduit; e.g., naris conduit  380 , may deliver more oxygen to the ‘intended’ naris, which is the naris adjacent to that naris conduit, though some of the oxygen that pass through the particular naris conduit may reach the other naris, and, similarly, most of the CO 2  exhaled from a particular naris reaches the ‘intended’ naris conduit, which is the adjacent naris conduit, though some CO 2  may reach the other naris conduit.) 
     Naris conduit  380  is substantially perpendicular to, and extends outwardly from both sides of, IPW  330 ′ (that is, from it extends from the ‘SRS’ side of IPW  330 ′ into the SRS space, and from the ‘SOR’ side of IPW  330 ′ into the SOR space), and thus naris conduit  380  provides a bi-directional fluid flow channel between the SRS and the SOR spaces. Naris conduit  380  includes a CO 2  extraction hole  384  to which CO 2  conduit  381  is fixedly mounted. The distal end of conduit  381  may be aligned with the surface of naris conduit  380  or protrude into internal space  385  of naris conduit  380 , and be in fluid flow communication with internal space  385  of naris conduit  380 . 
     Naris conduit  380  has a length L and an internal diameter D. Carbon dioxide conduit  381 , which is fixedly connected to naris conduit  380 , has a diameter d (d&lt;D), as shown in  FIG. 3C . The values of L and D, and the ratio R=d/D, may be optimized in terms of fluid dynamics according to expected breathing characteristics (e.g., breathing cycle, breathing efficacy, etc.) of patients, and also in terms of re-breathing effect (e.g., minimizing this effect). For example, the values of L, D and R may be set such that, during a breathing-in phase of a breathing cycle, CO 2  traces from the previous exhalation phase are quickly expelled (evacuated) from space  385  inside naris conduit  380  through conduit  381 , and, space  385  is quickly filled up with oxygen so that oxygen (or oxygen-enriched air) is readily available to the patient during inhalation. In addition, the values of L, D and R may be set such that, during a breathing-out phase of the breathing cycle, the CO 2  exhalation dynamics (e.g., CO 2  pressure and flow rate) can quickly clear space  385  from oxygen (e.g., by expelling the oxygen from naris conduit  380  back into the SOR) and fill up space  385  with CO 2 . (By ‘quickly’ is meant before the relevant breathing phase ends.) The effect of the optimization of the values of L, D and R is that during inhalation, the patient inhales only, or mostly, oxygen or oxygen-enriched air, and during exhalation the CO 2  sampling system receives CO 2  with genuine concentration level. In other words, the better the optimization of the values of L, D and R, the lesser the amount of oxygen that dilutes CO 2  samples during exhalation, and the lesser the amount of CO 2  in the inhaled oxygen. (When the values of L, D and R are optimized, the amount of oxygen diluting the CO 2  sample is negligible.) 
     During inhalation of oxygen, the subject, by breathing in, creates a sub-atmospheric pressure that draws from the oxygen reservoir (SOR) into the patient&#39;s respiratory space (SRS), and ultimately into the subject&#39;s lungs, only the amount of oxygen that is required for breathing, while the remainder of the oxygen contained in the SOR is held in reserve (and partially flows out of mask  310  through pressure relief openings  370  and  372 ), ready for use during subsequent inhalations. 
     By creating two, separate, spaces by partition wall  330 —one space which is the subject respiratory space, and another space which primarily contains oxygen—and manipulating the exchange of oxygen and CO 2  in the nares conduits  380  and  382 , and near mouth opening  390 , the oxygen inhaled by a patient is not diluted, or only negligibly diluted, by the exhaled CO 2 , and the CO 2  exhaled by the patient is not diluted, or only negligibly diluted, by oxygen at least in those (‘interference-free’) spaces from which CO 2  conduit  381 ,  383  and  392  extract CO 2 . Because partition wall  330  is large enough to cover the subject&#39;s airways (nose and mouth) and CO 2  is sampled directly from the subject&#39;s airways, the concentration level of the CO 2  exhaled from the subject&#39;s airways (and passes through CO 2  conduit  381 ,  383  and  392 , and finally through CO 2  sampling port  350 ) remains substantially the same even when the mask slightly moves on the subject&#39;s face. In addition, since the CO 2  conduit  381 ,  383  and  392  cover the subject&#39;s two nostrils and mouth, and partition wall  330  is large, partition wall  330  averages the CO 2  exhaled by the various patient&#39;s airways. Therefore, an issue that may exist in other types of oxygen masks, regarding whether a patient breathes only through the nose (through one naris or through both nares) or only through the mouth, is non-existent in mask  310  or in its variants. 
       FIG. 4A  shows an oxygen/capnography mask  410  with an internal partition wall (IPW)  430  worn on a subject  400  according to another example embodiment of the present invention. IPW  430 , which is positioned inside the domed mask, is smaller than IPW  330  of  FIGS. 3A-3B  and is positioned in proximity to the patient&#39;s nares. (While IPW  330  fully covers the patient&#39;s nares and mouth (and, therefore, IPW  330  includes an extra breathing opening  390  for the patient&#39;s mouth, IPW  430  does not include a mouth breathing opening.) IPW  430  is kept at distance from the patient&#39;s face by using an adjustment mechanism that includes, in this example, adjustment rod or shaft  460 ,  462  and  466 . In this embodiment, IPW  430  is smaller than IPW  330  and partly covers the nares and mouth of the patient. 
     IPW  430  includes two naris breathing openings to which two naris conduits  480  and  482  are respectively connected in a similar way as shown in  FIGS. 3A-3B . To naris conduits  480  and  482  are respectively connected CO 2  conduit  481  and CO 2  conduit  483  that function and are optimized in a similar way as CO 2  conduit  381  and CO 2  conduit  383  of  FIGS. 3A-3C . 
     A carbon dioxide conduit  492  is positioned near, or in close proximity to, the patient&#39;s mouth and functions in a similar way as CO 2  conduit  392  of  FIGS. 3A-3B . CO 2  conduits  481  and  482  are positioned adjacent, or in close proximity, to the patient&#39;s nares and function in a similar way as CO 2  conduits  381  and  382  of  FIGS. 3A-3B . Carbon dioxide conduits  481 ,  482  and  492  have a proximal end, and the proximal ends of the three conduits may be connected to a common CO 2  conduit  452  via a tubing manifold. Mask  410  may also include: (1) an oxygen port  440  to deliver oxygen to the subject oxygen reservoir (SOR) space inside oxygen/capnography mask  410 , and (2) a CO 2  sampling port  450  that is connected to CO 2  conduit  452  through which exhaled carbon dioxide may be extracted by a CO 2  sampling system. ( FIG. 4B  shows IPW  430  and its tubing system more clearly.) 
       FIG. 4C  shows a schematic view of mask  410  of  FIG. 4A . Mask  410 ′ includes a flat IPW  430 ′ that is roughly or approximately “L” shaped. One ‘leg’ (leg  420 ) of L-shaped IPW  430 ′ is positioned in proximity to the patient&#39;s nares, so it includes two naris conduits (naris conduits  480 ′ and  482 ′) to which CO 2  conduits  481  and  483  are respectively connected in order to obtain therefrom CO 2  samples from the CO 2  that is exhaled from the patient&#39;s nose. The other leg (leg  422 ) of L-shaped IPW  430 ′ is positioned in proximity to the patient&#39;s mouth, so it includes a through hole to which CO 2  conduit  492  is connected in order to obtain CO 2  samples exhaled from the patient&#39;s mouth. IPW  430  (and IPW  430 ′) has similar benefits as IPW  330  and is subjected to similar optimization it terms of dimensions. An angle α between the legs  420  and  422  of IPW  430 ′ may be subjected to optimization in terms of separation between oxygen and CO 2  during breathing. An elongated conduit fixation member  460  may be connected to IPW  430 ′ (e.g., to leg  422 ), on the one hand, and to conduit  452 ′, on the other hand, and keep the CCO 2  2 tubing, as a whole, in place inside the mask. Also shown in  FIG. 4C  are oxygen port  440 ′, CO 2  port  450 ′ and a CO 2  conduit that collects CO 2  samples from CO 2  conduits  481 ′,  483 ′ and  492 ′. 
       FIG. 5A  shows an oxygen/capnography mask  510  with an internal partition wall (IPW)  530  worn on a subject  500  according to another example embodiment. IPW  530 , which is positioned inside the domed mask, is similar to IPW  330  in the sense that it also includes two includes two naris conduits  580  and  582  and a mouth breathing opening. IPW  530  differs from IPW  330  in that IPW  530  is somewhat larger than IPW  330  and includes a perimeter  520  that is adapted to tightly fit onto, and touch, the face of the patient. IPW  530  may be regarded as a small mask inside mask  510 .  FIG. 5B  shows IPW  530  and the CO 2  tubing more clearly. IPW  530  is larger than IPW  330  and covers the nose tip and the mouth of the patent. 
       FIG. 6A  shows an oxygen/capnography mask  610  with an internal partition wall (IPW)  630  according to another example embodiment. IPW  630  is very small relative to IPWs  330 ,  430  and  530 , and is positioned near the nares of the patient. IPW  630 , which is positioned inside the domed mask, has a size that complies with the width of the nares; that is, IPW  630  may have a size that is similar to (e.g., somewhat smaller than, or somewhat larger than) the width of the subject&#39;s nose. (The size of an IPW can be reduced to any size that still imparts it the functionalities and benefits described herein.) IPW  630  may be shaped like a scoop in order to more efficiently capture CO 2  from the patient&#39;s nares in a region where the CO 2  cannot be washed away by oxygen. (The patient may breathe normally via the mouth without affecting, or be effected by, the breathing and CO 2  monitoring via IPW  630 .) By way of example, IPW  630  includes at least one naris conduit, which is shown at  680 . (Naris conduit  680  is similar to, and functions in a similar way as, naris conduits  380 ,  480  and  580 . Naris conduit  680  may also be subjected to a similar optimization calculation.) IPW  630  may be positioned in a region between the patient&#39;s upper lip and nose, and naris conduit  680  may be centered between the two nares in order to capture CO 2  that is exhaled from both nares. A CO 2  conduit  620  is connected between a through hole in naris conduit  680  and a CO 2  port  650  so that CO 2  can be extracted from naris conduit  680  and delivered to a CO 2  monitoring system via CO 2  port  650 . IPW  630  is kept at distance from the patient&#39;s face by using an adjustment mechanism that includes, in this example, adjustment rod or shaft  660 ,  662  and  666 . ( FIG. 6B  shows IPW  630  more clearly.) 
     IPW  630  may be made of a flat thin plastic material whose surface has an area that is small but large enough to produce, during exhalation, a dynamic CO 2  pressure that is high enough to expel oxygen from the region between the patient&#39;s nose and mouth, leaving there only, or mostly, CO 2  from which CO 2  samples can be extracted through CO 2  conduit  620 . 
       FIG. 7A  shows an oxygen/capnography mask  710  with an internal partition wall (IPW)  730  according to another example embodiment. IPW  730 , which is positioned inside the domed mask, is similar to IPW  630  in terms of size. (IPW  730  is also very small relative to IPWs  330 ,  430  and  530 , and is positioned near the nares of the patient.) IPW  730  differs from IPW  630  in that IPW  730  does not include naris conduits. Instead, two CO 2  conduits  781  and  783  are connected to CO 2  extracting openings in IPW  730  and function in a similar way as CO 2  conduits  381  and  383  of  FIGS. 3A-3C . 
     IPW  730  may be shaped like a scoop in order to more efficiently capture CO 2  from the patient&#39;s nares in a region where the CO 2  cannot be washed away by oxygen. (The patient may breathe normally via the mouth without affecting, or be effected by, the breathing and CO 2  monitoring via IPW  730 .) IPW  730  may be positioned in a region between the patient&#39;s upper lip and nose, and the openings in IPW  730 , to which the distal ends of CO 2  conduits  781  and  783  are connected, may respectively be positioned in front of the two nares in order to capture CO 2  that is exhaled from them. The proximal ends of CO 2  conduits  781  and  783  may be connected to a CO 2  conduit  752  whose other end is connected to a CO 2  port  750  so that CO 2  can be extracted from IPW  730  and delivered to a CO 2  monitoring system via CO 2  port  750 . IPW  730  is kept at distance from the patient&#39;s face by using an adjustment mechanism that includes, in this example, adjustment rod or shaft  760 ,  762  and  766 . ( FIG. 7B  shows IPW  730  more clearly.) 
     IPW  730  may be made of a flat thin plastic material whose surface has an area that is small but large enough to produce, during exhalation, a dynamic CO 2  pressure that is high enough to expel oxygen from the region between the patient&#39;s nose and mouth, leaving there only, or mostly, CO 2  from which CO 2  samples can be extracted through CO 2  conduit  752 . 
       FIG. 8  shows an inner partition wall (IPW)  830  according to another example embodiment. IPW  830  is similar to IPW  330  with the exception that IPW  830  is perforated, with the perforation slits or holes shown at  884 . IPW  330  includes two naris conduits ( 880  and  882 ), a mouth breathing opening  890 , and CO 2  tubing that includes three CO 2  conduits ( 881 ,  883  and  892 ) that are connected to a common CO 2  conduit  852 . 
     IPW  830  differs from IPW  330  in that it contains perforation slits or holes. (Some of the perforation slits or holes are shown at  884 , though all of the perforation slits or holes in IPW  830  are referenced by reference numeral  884 .) Using perforation slits or holes such as, or similar to, perforation slits or holes  884 , is beneficial because such perforation may prevent under-pressure condition in the subject respiration space (SRS) during inhalation and over-pressure condition in the SRS during exhalation, and thus facilitates breathing when a patient has breathing difficulties such as breathing in oxygen. Perforation slits or holes  884  also reduce the re-breathing effect, which is a breathing condition in which the patient breathes in CO 2  that is not timely washed away (from the SRS part of the mask) before inhaling oxygen. The size and arrangement (e.g., location, density) of perforation slits or holes  884  may be manipulated in order to optimize IPW  830  in terms of, for example, ease of breathing, re-breathing effect, and CO 2  sampling efficacy. For example, the closer the perforation slits or holes to a CO 2  ‘sampling point’ (e.g., naris conduit  880  or  882 ) in the IPW, the denser the perforation slits/holes. In another example, the closer the perforation slits or holes to the CO 2  sampling point in the IPW, the smaller the slits/holes (e.g., the smaller their diameter). By way of example, perforation slits or holes  884  are evenly distributed in IPW  830 , and all slits/holes have a similar size. 
       FIG. 9  shows an inner partition wall (IPW)  930  according to another example embodiment. IPW  930  is similar to IPW  830  in the sense that it, too, includes three CO 2  conduits (conduits  981 ,  983  and  992 ) and perforation slits or holes (some of which are shown at  982 , though reference numeral  982  refers to all perforation slits or holes in IPW  930 ). However, IPW  930  differs from IPW  830  in that IPW  930  does not include a mouth breathing opening and naris conduits. Instead, multiple perforation slits or holes, for example perforation slits or holes  920 , are used instead of one large mouth breathing opening, and, in addition, CO 2  conduits  981 ,  983  and  992  are respectively directly connected to IPW  930  via CO 2  sampling, or access, points in IPW  930 , where the CO 2  sampling, or access, points in the IPW may be perforation slits or holes; e.g., perforation slits or holes  981 ′,  983 ′ and  992 ′. 
     The size and arrangement (e.g., location, density) of the perforation slits or holes  982  may be manipulated in order to optimize functionality of IPW  930  in terms of ease of breathing, the re-breathing effect, and CO 2  sampling efficacy. For example, the closer the perforation slits or holes to a CO 2  sampling, or access, point (e.g., CO 2  sampling point  981 ′), the denser the slits/holes. In another example, the closer the slits or holes to a CO 2  sampling point (e.g., CO 2  sampling point  983 ′), the smaller the slits/holes (e.g., the smaller their diameter). By way of example, perforation slits or holes  982  are evenly distributed in IPW  930 , and all slits/holes have a similar size. A CO 2  sampling point may be, for example, a naris conduit (e.g., naris conduit  880  or  882 ), as in  FIG. 8 , or, in the absence of a naris conduit, a perforation slit or hole (e.g., perforation slits or holes  981 ′,  983 ′,  992 ′), as shown in  FIG. 9 . 
       FIG. 10A  shows an oxygen/capnography mask  1010  according to another example embodiment. Mask  1010  may include an IPW  1030  that may be similar to IPW  630 . Mask  1010  includes an oxygen port  1040 . Distal end  1042  of oxygen port  1040 , which resides in mask  1010 , may include a gas disperser  1020  (e.g., sprinkler, scatterer, sprayer, etc.) for dispersing (e.g., by spraying) oxygen into the oxygen reservoir part of mask  1010 , which is most of the space inside mask  1010 . Spraying oxygen into mask  1010  has a benefit over transferring it in the form of gas jet (as is the case with oxygen port  340  in  FIG. 3A , for example) because an oxygen jet causes turbulences inside the mask (e.g., mask  310 ,  FIG. 3A ), and turbulences inside the mask detrimentally affect (e.g., disrupt) oxygen inhalation and CO 2  sampling (because turbulences mix up the two gasses). Gas disperser  1020  is shown more clearly in  FIG. 10B , which is described below. Referring to  FIG. 10B , gas disperser  1020  may include, at its distal end  1042 , a hollow base part  1070  on top of which is mounted a hollow pointed, or tapering, member  1050  having an angle β (e.g., β=30 degrees). Pointed or tapered member  1050  may have a plurality of gas outlets, or vents,  1060  for dispersing oxygen (that is, through which oxygen can be dispersed; e.g., sprayed out) into the oxygen reservoir space of mask  1010 . The gas dispenser at the distal end of an oxygen port may be or include a pointed cap that is fixedly kept at distance from a hollow base. Such structure results in ‘peripheral’ dispersion of oxygen through an opening formed by the distance between the cap and the hollow base.  FIGS. 11A-11B and 12A-12B , which are describe below, show example pointed cap like gas dispensers. (A gas dispenser may include another cap or a cap similar to the cap shown in  FIGS. 11A-11B and 12A-12B .) 
       FIG. 11A  shows an oxygen/capnography mask  1110  according to another example embodiment. Mask  1110  may include an IPW  1130  that may be similar to IPW  630 . Mask  1110  includes an oxygen port  1140 . A distal end  1142  of oxygen port  1140 , which resides in mask  1110 , may include a disperser  1120  for dispersing oxygen in the oxygen reservoir part of mask  1110 , which, in this embodiment, may occupy most of the space inside mask  1110 . Distributing oxygen into mask  1010  in the way described below has a benefit over transferring oxygen in the form of gas jet (as is the case with oxygen port  340  in  FIG. 3A , for example) because an oxygen jet causes turbulences inside the mask (e.g., mask  310 ,  FIG. 3A ), which has drawbacks as described above in connection with  FIGS. 10A-10B . 
     Gas disperser  1120  is shown more clearly in  FIG. 11B , which is described below. Referring to  FIG. 11B , gas disperser  1120  may include, at its distal end  1142 , a hollow base part  1180  on top of which, though distanced from base part  1180 , is mounted a pointed, tapering or conical, cap  1150  having an angle γ (e.g., γ=120 degrees). Pointed cap  1150  is fixedly distanced from base part  1180  by elongated spacing members  1170 ,  1172  and  1174 . The distance between the base of pointed cap  1150  and the base member  1180  results in a gas outlet, or vent,  1160  through which oxygen flows out into the subject oxygen reservoir (SOR) space of mask  1110  in the form of a gas ‘cloud’. 
       FIG. 12A  shows an oxygen/capnography mask  1210  according to another example embodiment. Mask  1210  may include an IPW  1230  that may be similar to IPW  1130 . Mask  1210  includes an oxygen port  1240 . Distal end  1242  of oxygen port  1240 , which resides in mask  1210 , may include a gas disperser  1220  for distributing oxygen in the oxygen reservoir part of mask  1210 , which is most of the space inside mask  1210 . 
     Gas disperser  1220  is shown more clearly in  FIG. 12B , which is described below. Referring to  FIG. 12B , gas disperser  1220  may include, at its distal end  1242 , a hollow base part  1230  on top of which, though distanced from base part  1230 , is mounted a pointed cap  1250  that is similar to pointed cap  1150  of  FIGS. 11A-11B , except that pointed cap  1250  is mounted on base part  1230  with the cap&#39;s apex  1252  turning to, or facing, the opposite direction; that is, towards base part  1230 . Pointed cap  1250  is fixedly kept at distance from base part  1230  by elongated spacing members similar to those that keep pointed cap  1150  at distance from base part  1130 . The distance between the base of pointed cap  1250  and the base member  1230  results in a gas outlet, or vent,  1260  through which oxygen flows out into the SOR space of mask  1210  in the form of a gas ‘cloud’.  FIGS. 10A-10B, 11A-11B and 12A-12B  show some example gas dispersers. Alternative (e.g., other or similar) types of gas dispensers may be used. 
       FIGS. 13A-13C  show various structures of naris conduits according to example embodiments. Referring to  FIG. 13A , a naris conduit  1310  includes a longitudinal axis  1320  and is attached to or mounted on an IPW (the IPW is shown symbolically at  1330 ) such that IPW  1330  defines, or separates between, a subject respiration space (SRS) and a subject oxygen reservoir (SOR). Naris conduit  1310  (or its longitudinal axis  1320 ) may be perpendicular to IPW  1330 , or it may be at an angle with respect to IPW  1330 . Naris conduit  1310  also includes a CO 2  conduit  1340 . Carbon dioxide conduit  1340  may be a short, straight, tube that is mounted on, and protrudes only outwardly from, body  1350  of naris conduit  1310 . Carbon dioxide conduit  1340  may protrude from body  1350  of naris conduit  1310  perpendicularly. Carbon dioxide conduit  1340  includes an open channel that is in fluid flow communication with inner space  1360  of naris conduit  1310 . During inhalation, oxygen fills up naris conduit  1310  with oxygen while oxygen is transferred ( 1370 ) through naris conduit  1310  from the SOR side to the SRS side. During exhalation, CO 2  exhaled by the patient forcedly expels oxygen from the interior space  1360  of naris conduit  1310  back into the SOR side, and some of the exhaled CO 2  (the CO 2  samples) are extracted ( 1380 ) through CO 2 conduit  1340  (and through a connecting tube) by a CO 2  monitoring system. 
     Referring to  FIG. 13B , naris conduit  1312  is structurally similar to naris conduit  1310  except for the CO 2  conduit: the CO 2  conduit of (connected to) naris conduit of  1312  protrudes from body  1352  of naris conduit  1312  both outwardly (the part protruding outwardly is shown at  1390 ) and inwardly (into internal space  1362  of naris conduit  1312 ; the part protruding inwardly is shown at  1392 ). Distal end  1313  of the CO 2  conduit may reach, or be aligned with (e.g., coincide with), longitudinal axis  1322  of naris conduit  1312 , or it may be shorter such that it is misaligned with longitudinal axis  1322 . 
     Referring to  FIG. 13C , naris conduit  1314  is structurally similar to naris conduits  1310  and  1312  except for the CO 2  conduit: like in  FIG. 13B , CO 2  conduit  1315  of naris conduit of  1314  protrudes from body  1354  of naris conduit  1314  both outwardly, as shown at  1394 , and inwardly (into internal space  1364  of naris conduit of  1314 ), as shown at  1396 . However, CO 2  conduit  1315  is an “L” shaped tube having two tube sections or legs: one tube section or leg (an ‘outlet’ part, shown at  1394  and  1396 ) that is mounted on body  1354  and transfer CO 2  samples to a CO 2  monitoring system, and another tube section or leg (an ‘inlet’ part, shown at  1317 ) that is directed towards (it faces) the SRS side in order to collect CO 2  samples. Tube section  1317  may be parallel to (e.g., coincide with) longitudinal axis  1324  of naris conduit  1314 , or it may slant with respect to longitudinal axis  1324  of naris conduit  1314 . 
     Various aspects of the techniques disclosed herein are combinable with various types of binary-gas or multi-gas face masks. Although the discussion herein relates to face masks for delivering oxygen and sampling exhaled carbon dioxide gases, the techniques are not limited in this regard. 
     While certain features have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art, and the appended claims are intended to cover all such modifications and changes.