Patent Publication Number: US-2007113848-A1

Title: Respiratory monitoring with cannula receiving respiratory airflows and exhaled gases

Description:
BACKGROUND  
      1. Field  
      In general, the inventive arrangements relate to respiratory care, and more specifically, to improvements in respiratory monitoring.  
      2. Description of Related Art  
      For illustrative, exemplary, representative, and non-limiting purposes, preferred embodiments of the inventive arrangements will be described in terms of medical subjects needing respiratory care. However, the inventive arrangements are not limited in this regard.  
      Now then, referring generally, when a subject is medically unable to sustain breathing activities on the subject&#39;s own, mechanical ventilators can improve the subject&#39;s condition and/or sustain the subject&#39;s life by assisting and/or providing requisite pulmonary gas exchanges on behalf of the subject. Not surprisingly, many types of mechanical ventilators are well-known, and they can be generally classified into one (1) of three (3) broad categories: spontaneous, assisted, and/or controlled mechanical ventilators.  
      During spontaneous ventilation, a subject generally breathes at the subject&#39;s own pace, but various, external factors can affect certain parameters of the ventilation, such as tidal volumes and/or baseline pressures within a system. With this first type of mechanical ventilation, the subject&#39;s lungs still “work,” in varying degrees, and the subject generally tends and/or tries to use the subject&#39;s own respiratory muscles and/or reflexes to control as much of the subject&#39;s own breathing as the subject can.  
      During assisted or self-triggered ventilation, the subject generally initiates breathing by inhaling and/or lowering a baseline pressure, again by varying degrees, after which a clinician and/or ventilator then “assists” the subject by applying generally positive pressure to complete the subject&#39;s next breath.  
      During controlled or mandatory ventilation, the subject is generally unable to initiate breathing by inhaling and/or exhaling and/or otherwise breathing naturally, by which the subject then depends on the clinician and/or ventilator for every breath until the subject can be successfully weaned therefrom.  
      Now then, as is well-known, non-invasive mechanical ventilation can be improved upon by containing and/or controlling the spaces surrounding the subject&#39;s airways in order to achieve more precise control of the subject&#39;s gas exchanges. Commonly, this is accomplished by applying i) an enclosed facemask, which can be sealably worn over the subject&#39;s nose, mouth, and/or both, or ii) an enclosed hood or helmet, which can be sealably worn over the subject&#39;s head, the goals of which are to at least partly or wholly contain and/or control part or all of the subject&#39;s airways. Referring generally, these types of arrangements are known as “interfaces,” a term that will be used hereinout to encompass all matters and forms of devices that can be used to secure subject airways in these fashions.  
      During non-invasive mechanical ventilation, it is increasingly important to monitor the subject&#39;s respiration and/or other respiratory airflows, at least to access the adequacy of ventilation and/or control operation of attached ventilators. For example, interface leaks and/or interface compressions commonly adversely effect a subject&#39;s interpreted and/or real airflow needs. More specifically, since interface disturbances will always be difficult and/or impossible to avoid, a need exists to deal with them appropriately.  
      In accordance with all or part of the foregoing, the inventive arrangements address interface disturbances and respiratory airflows, particularly during non-invasive spontaneous and/or assisted mechanical ventilation.  
     SUMMARY  
      In one embodiment, a cannula receives respiratory airflows, exhaled gases, and ambient airflows.  
      In another embodiment, a cannula receives respiratory airflows, exhaled gases, and interface airflows.  
      In yet another embodiment, a cannula receives i) respiratory airflows and exhaled gases from a subject, and ii) interface airflows from an area near a cannula.  
      In yet still another embodiment, a respiratory monitoring method receives respiratory airflows, exhaled gases, and ambient airflows.  
      In a further embodiment, a respiratory monitoring method receives respiratory airflows, exhaled gases, and interface airflows.  
      In an additional embodiment, a respiratory monitoring method receives i) respiratory airflows and exhaled gases from a subject, and ii) interface airflows from an area near a cannula.  
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
      A clear conception of the advantages and features constituting inventive arrangements, and of various construction and operational aspects of typical mechanisms provided by such arrangements, are readily apparent by referring to the following illustrative, exemplary, representative, and non-limiting figures, which form an integral part of this specification, in which like numerals generally designate the same elements in the several views, and in which:  
       FIG. 1  depicts generic monitoring of a subject&#39;s respiratory airflows.  
       FIG. 2  illustrates a well-known Bernoulli effect, whereby pressures vary in accordance with airflows generated in a pitot tube or the like.  
       FIG. 3  is a sectional side-view of a subject using a nasal cannula within an interface.  
       FIG. 4  is a sectional side-view of a subject using an oral cannula within an interface.  
       FIG. 5  is a sectional side-view of a subject using an oro-nasal cannula within an interface.  
       FIG. 6  is a front view of a subject using the oro-nasal cannula of  FIG. 5  within another interface.  
       FIG. 7  is a flow chart comparing first and second pressure changes to distinguish respiratory and/or non-respiratory events.  
       FIG. 8  is an event table comparing respiratory airflows and interface airflows to determine resulting pressure differentials to distinguish the likely significance of various respiratory and/or non-respiratory events.  
       FIG. 9  is a flow chart determining pressure differentials to distinguish respiratory and/or non-respiratory events.  
       FIG. 10  is an event table determining pressure differentials to distinguish likely respiratory and/or non-respiratory events.  
       FIG. 11  is a front-perspective view of a nasal cannula receiving the following: 
      i) nasal airflows as respiratory airflows; and     ii) interface airflows.    
       FIG. 12  is a front view of the nasal cannula of  FIG. 11 .  
       FIG. 13  is a front-perspective view of an oral cannula receiving the following: 
      i) mouth airflows as respiratory airflows; and     ii) interface airflows.    
       FIG. 14  is a front view of the oral cannula of  FIG. 13 .  
       FIG. 15  is a front-perspective view of an oro-nasal cannula receiving the following: 
      i) nasal airflows and mouth airflows as respiratory airflows; and     ii) interface airflows.    
       FIG. 16  is a front view of the nasal cannula of  FIG. 15 .  
       FIG. 17  is a front view of an oro-nasal cannula receiving the following: 
      i) nasal airflows and mouth airflows as respiratory airflows; and     ii) interface airflows in direct connection through the cannula.    
       FIG. 18  is a cut-away view taken along line  18 - 18  in  FIG. 17 , depicting the direct connection through the cannula in more detail.  
       FIG. 19  is a partial view of a cannula receiving interface airflows in open connection with an interface.  
       FIG. 20  is a simplified pneumatic circuit for sensing pressure differentials between the following: 
      i) respiratory airflows and interface airflows; 
 
 particularly according to a first preferred embodiment, having a single differential pressure transducer. 
   
       FIG. 21  is an alternative view of the pneumatic circuit of  FIG. 20 , particularly having calibration valves, P gage , and/or ventilator control.  
       FIG. 22  is a front-perspective view of an oro-nasal cannula receiving the following: 
      i) nasal airflows as first respiratory airflows;     ii) mouth airflows as second respiratory airflows; and     iii) interface airflows.    
       FIG. 23  is a simplified pneumatic circuit for sensing pressure differentials between the following: 
      i) first respiratory airflows and interface airflows; and     ii) second respiratory airflows and interface airflows; 
 
 particularly according to a second preferred embodiment, having multiple differential pressure transducers. 
   
       FIG. 24  is an alternative view of the pneumatic circuit of  FIG. 23 , particularly having calibration valves, P gage , and/or ventilator control.  
       FIG. 25  is a front-perspective view of an oro-nasal cannula receiving the following: 
      i) nasal airflows as first respiratory airflows;     ii) mouth airflows as second respiratory airflows;     iii) nasal CO 2  and mouth CO 2  as respiratory CO 2 ; and     iv) interface airflows; 
 
 particularly according to a first preferred embodiment, having bifurcated prong capture. 
   
       FIG. 26  is a rear-perspective view of the oro-nasal cannula of  FIG. 25 .  
       FIG. 27  is a cut-away view taken along line  27 - 27  of  FIG. 25 .  
       FIG. 28  is a front-perspective view of an oro-nasal cannula receiving the following: 
      i) nasal airflows as first respiratory airflows;     ii) mouth airflows as second respiratory airflows;     iii) nasal CO 2  and mouth CO 2  as respiratory CO 2 ; and     iv) interface airflows; 
 
 particularly according to a second preferred embodiment, having direct and/or offset prong capture. 
   
       FIG. 29  is a first cut-away view taken along line  29 - 29  in  FIG. 28 .  
       FIG. 30  is a second cut-away view taken along line  30 - 30  in  FIG. 28 .  
       FIG. 31  is a third cut-away view taken along line  31 - 31  in  FIG. 28 .  
       FIG. 32  is a rear-perspective view of an oro-nasal cannula receiving: 
      i) nasal airflows as first respiratory airflows;     ii) mouth airflows as second respiratory airflows;     iii) nasal CO 2  and mouth CO 2  as respiratory CO 2 ; and     iv) interface airflows; 
 
 particularly according to a third preferred embodiment, having a capture enhancer and/or scooped prong capture. 
   
       FIG. 33  is a perspective view of an alternative capture enhancer of  FIG. 32 .  
       FIG. 34  is a pneumatic circuit for sensing pressure differentials between the following: 
      i) first respiratory airflows and interface airflows; and     ii) second respiratory airflows and interface airflows; 
 
 particularly according to the second preferred embodiment of  FIGS. 23-24 , having the multiple differential pressure transducers, as well as exhaled gas sampling, calibration valves, P gage , and/or ventilator control. 
   
       FIG. 35  is a table depicting various combinations of some or all of the variously described attributes.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Referring now to the figures, preferred embodiments of the inventive arrangements will be described in terms of medical subjects needing respiratory care. However, the inventive arrangements are not limited in this regard. For example, while variously described embodiments provide improvements in respiratory care, and more specifically, improvements in respiratory monitoring, such as cannular improvements, particularly suited for use during non-invasive spontaneous and/or assisted mechanical ventilation, other contexts are also hereby contemplated, including various other healthcare, consumer, industrial, radiological, and inspection systems, and the like.  
      Referring now to  FIG. 1 , a sensor  10  is configured to receive at least partial and/or full sampling of a subject&#39;s  12  nasal airflows (“NA”) and mouth airflows (“MA”) as respiratory airflows (“RA”). Preferably, the sensor  10  is in communication with downstream electrical and/or pneumatic circuitry (not shown in  FIG. 1 ) that measures the strength of the respiratory airflows RA and outputs a signal indicative thereof. Accordingly, changes in the nasal airflows NA and mouth airflows MA past the sensor  10  can be detected. More particularly, the term “airflow,” in these contexts, will be used hereinout to encompass generalized disturbances (e.g., compression and/or decompressions) of a column of air held in dynamic suspension between the sensor  10  and subject  12 .  
      Referring now to  FIG. 2 , pressures, which vary with airflow rates, are generated in a tube  14 , such as a pitot tube, by placing an open end  16  thereof in parallel with, or at some intermediate angle to, various airflows. Another, more distal end  18  of the tube  14  terminates at a pressure measuring and/or sensing device  20 , such as an electrical pressure transducer, the output of which varies in accordance with the airflows.  
      Now then, referring more specifically, the pitot-tube is a well-known hollow tube that can be placed, at least partially, longitudinally to the direction of airflows, allowing the same to enter an open end thereof at a particular approach velocity. After the airflows enter the pitot tube, they eventually come to a stop at a so-called stagnation point, at which point their velocity energy is transformed into pressure energy, the latter of which can be detected by the electrical pressure transducer. Bemouli&#39;s equation can be used to calculate the static pressure at the stagnation point. Then, since the velocities of the airflows within the pitot tube are zero at the stagnation point, downstream pressures can be calculated.  
      Referring now to  FIGS. 3-6 , the subject  12  receives ventilator support from a ventilator  22  via a breathing conduit  24 . More specifically, the breathing conduit  24  communicates with the subject  12  between the ventilator  22  and an interface  26 , which, for example, in the embodiment shown in  FIGS. 3-5 , is a generally enclosed mask or facemask  28 , and, in the embodiment shown in  FIG. 6 , is a generally enclosed hood or helmet  30 , the interfaces  26  of which are suitable for maintaining positive airway ventilation pressure within the interface  26 . More specifically, for example, the mask or facemask  28  can be sealably worn over a nose  32  and/or mouth  34  of the subject  12 , while the hood or helmet  30  can be sealably worn over a head  36  of the subject  12 , the sealing of which is designed to at least partly or wholly contain and/or control part or all of the subject&#39;s  12  airways. Accordingly, a sealed area  38  within each interface  26  is created, the area  38  being reasonably sealed from an area  40  external the interface  26 . In other words, interface airflows IA within the area  38  of each interface  26  are generally independent of airflows in the area  40  external from the interface  26 , and/or vice-versa.  
      Now then, as shown in  FIG. 1 , it is also possible to eliminate the interface  26 , in which case the interface airflows IA become ambient airflows AA, particularly as the area  38  within the interface  26  and the area  40  external the interface  26  merge to become indistinct and/or non-separable. In this context, the interface airflows IA and ambient airflows AA are one in the same.  
      Otherwise, each interface  26  is adapted to provide a closed connection between one or more of the subject&#39;s  12  breathing passages, such as the subject&#39;s  12  nasal passages and/or oral passages, and the ventilator  22 . Accordingly, the ventilator  22  and interface  26  are suitably arranged to provide a flow of breathing gases to and/or from the subject  12  through the breathing conduit  24 . This arrangement is generally known as the breathing circuit.  
      In  FIGS. 3-6 , the subject  12  wears a cannula  50 , such as a nasal cannula  52  (e.g., see  FIG. 3 ), oral cannula  54  (e.g., see  FIG. 4 ), and/or oro-nasal cannula  56  (e.g., see  FIGS. 5-6 ). More specifically, each of the depicted cannulas  50  is configured to communicate with and/or receive respiratory airflows RA from the subject  12  and interface airflows IA from the area  38  within the interface  26  and/or ambient airflows AA.  
      Now then, a goal of respiratory care is to detect changes in the subject&#39;s  12  respiratory airflows RA, thereby triggering an appropriate response by the ventilator  22 . However, disturbances to the interface  26  can hinder this objective. For example, if a leak or compression develops at and/or about the interface  26 , the ventilator  22  could mistakenly interpret a respiratory event as a non-respiratory event, and/or vice-versa. For example, if pressure drops within the area  38  of the interface  26 , the ventilator  22  could interpret this pressure drop as indicating the subject&#39;s  12  attempt to initiate inhalation, thus responding accordingly. However, if the pressure drop within the area  38  of the interface  26  was instead triggered by an interface leak somewhere between the subject  12  and the ventilator  22  in the breathing circuit, then the ventilator  22  could likely mis-interpret the pressure drop and/or mis-respond in properly ventilating the subject  12 . Similarly, if pressure increases within the area  38  of the interface  26 , the ventilator  22  could interpret this pressure increase as indicating the subject&#39;s  12  attempt to initiate exhalation, thus responding accordingly. However, if the pressure increase within the area  38  of the interface  26  was instead triggered by interface compression somewhere between the subject  12  and the ventilator  22  in the breathing circuit, then the ventilator  22  could likely mis-interpret the pressure increase and/or mis-respond in properly ventilating the subject  12 . Accordingly, attempts to decrease false reads within the area  38  of the interface  26  are always desired.  
      Referring now more generally, one of the major issues with non-invasive mechanical ventilation are the occurrences of these leaks and/or compressions in the interface  26  and/or breathing circuit. These disturbances result in the ventilator&#39;s  22  inability to accurately assess the respiratory needs and/or efforts of the subject  12 . However, accurately assessing the respiratory needs and/or efforts of the subject  12  is necessary to accurately synchronize the assistance of the mechanical ventilation.  
      Typically, these respiratory needs and/or efforts of the subject  12  have been detected by placing a pressure sensor within the ventilator  22  and/or interface  26 . However, when leaks and/or compressions in the interface  26  occur with conventional pressure sensors, the ventilator  22  only sees a resulting flow or pressure change about the area  38  within the interface  26 , and it interprets it as the subject&#39;s attempt to breath in or out. Accordingly, the ventilator  22  will not provide the proper ventilator support to the subject  12 , particularly if the leaks and/or compressions remain undetected and/or undetectable.  
      Now then, recognition is made of the fact that differences in the respiratory airflows RA and interface flows IA and/or ambient airflows AA can be used to decrease these false reads. More specifically, if precise and accurate determinations can be made between the respiratory airflows RA and interface airflows IA and/or ambient airflows AA, then falsely interpreting what is happening at the area  38  within the interface  26  can be minimized and/or altogether eliminate. For example, if the interface  26  and/or breathing circuit develops a leak, then both the respiratory airflows RA and interface airflows IA will be similarly effected—i.e., they will both trend in parallel and both decrease, in which case the ventilator  22  can suspend interpreting the pressure decrease as the subject&#39;s  12  attempt to inhale. Similarly, if the interface  26  and/or breathing circuit is compressed, then both the respiratory airflows RA and interface airflows IA will be similarly effected—i.e., they will both trend in parallel and both increase, in which case the ventilator  22  can suspend interpreting the pressure increase as the subject&#39;s  12  attempt to exhale. Accordingly, whenever there is a disturbance (e.g., a leak and/or compression) in the interface  26  and/or breathing circuit, pressure at all sensing ports will change by an equal amount, such that all of the relative differential pressures therebetween will remain unchanged. Therefore, only changes in respiratory airflows RA for which there is not a corresponding change in interface airflows IA will be interpreted as a respiratory event, and vice-versa.  
      Referring now to  FIG. 7 , the afore-described principles of operation will be summarized in terms of a flowchart  60 . More specifically, a methodology begins at a step  62 , after which a first pressure change is detected in a step  64 . At a subsequent step  66 , it is determined whether a substantially equivalent second pressure change was detected. If a substantially equivalent second pressure change was not detected in step  66 , then it is concluded that there was a respiratory event, as indicated in step  68 , after which the method then terminates in a step  70  and the ventilator  22  responds appropriately through the breathing conduit  24  and/or breathing circuit. Alternatively, however, if a substantially equivalent second pressure change was detected in step  66 , then it is concluded that there was not a respiratory event, as indicated in step  72 , after which control iteratively returns to step  64  to detect another first pressure change. In this fashion, corresponding differential pressure changes are sensed between the respiratory airflows RA and interface airflows IA and/or ambient airflows AA for properly interpreting the same, particularly as respiratory or non-respiratory events.  
      Referring now to  FIG. 8 , interface leaks and/or interface compressions commonly adversely effect the subject&#39;s  12  interpreted and/or real airflow needs, as previously mentioned. Now then, if the subject&#39;s  12  respiratory airflows RA increase at the same time and/or in the same way that the interface airflows IA increase, then a pressure differential between the two will not develop, signifying a non-respiratory event, such as a likely compression of the interface  26 . In other words, the increase in respiratory airflow RA, while ordinarily signifying a subject&#39;s attempt to breath out, is properly understood in this context to instead likely mean that the interface  26  was compressed, as per the corresponding increase in the interface airflows IA.  
      However, if the subject&#39;s  12  respiratory airflows RA increase at the same time that the interface airflows IA decrease or stay the same, then a pressure differential between the two will develop, signifying a respiratory event, such as the subject&#39;s  12  likely attempt to exhale. In other words, the increase in respiratory airflow RA, while ordinarily signifying the subject&#39;s  12  attempt to breath out, is properly understood in this context to mean that the subject  12  did indeed likely attempt to exhale, as per the corresponding no change or decrease in the interface airflows IA.  
      Similarly, if the subject&#39;s  12  respiratory airflows RA decrease at the same time and/or in the same way that the interface airflows IA decrease, then a pressure differential between the two will not develop, again signifying a non-respiratory event, such as a likely leak at the interface  26 . In other words, the decrease in respiratory airflow RA, while ordinarily signifying the subject&#39;s  12  attempt to breath in, is properly understood in this context to instead likely mean that the interface  26  developed a leak, as per the corresponding decrease in the interface airflows IA.  
      However, if the subject&#39;s  12  respiratory airflows RA decrease at the same time that the interface airflows IA increase or stay the same, then a pressure differential between the two will develop, signifying a respiratory event, such as the subject&#39;s  12  likely attempt to inhale. In other words, the decrease in respiratory airflow RA, while ordinarily signifying a subject&#39;s  12  attempt to breath in, is properly understood in this context to mean that the subject  12  did indeed likely attempt to inhale, as per the corresponding no change or increase in the interface airflows IA.  
      These above-described scenarios are presented in an event table  74  in  FIG. 8 .  
      Referring now to  FIG. 9 , the afore-described principals of operation will be summarized in terms of another flowchart  80 . More specifically, a methodology begins at a step  82 , after which it is determined whether a pressure differential was detected in a step  84 . If a pressure differential was detected in step  84 , then it is concluded that there was a respiratory event, as indicated in step  86 , after which the method then terminates in a step  88  and the ventilator  22  responds appropriately through the breathing conduit  24  and/or breathing circuit. Alternatively, if a pressure differential was not detected in step  84 , then it is concluded that there was not a respiratory event, as indicated in step  90 , after which control iteratively returns to step  84  to detect another pressure differential. In this fashion, corresponding differential pressure changes are sensed between the respiratory airflows RA and interface airflows IA and/or ambient airflows AA for properly interpreting the same, particularly as respiratory or non-respiratory events.  
      Referring now to  FIG. 10 , resulting pressure differentials between the respiratory airflows RA and interface airflows IA generally signify respiratory events, while a lack thereof generally signifies non-respiratory events.  
      These above-described scenarios are presented in an event table  92  in  FIG. 10 .  
      Referring now to  FIGS. 11-12 , a nasal cannula  52  is adapted to receive i) nasal airflows NA, and ii) interface airflows IA. More specifically, the nasal cannula  52  includes one or more nasal prongs  102  that are adapted to fit within one or more nares  104  of the nose  32  of the subject  12 , particularly for communicating with and/or receiving and/or carrying the nasal airflows NA therefrom. The nasal airflows NA are then communicated by and/or received by and/or carried by a body  106  of the cannula  50  from the nasal prongs  102  to a respiratory lumen  108 . More specifically, the nasal cannula  52  is adapted to receive the nasal airflows NA as respiratory airflows RA for communication to a pneumatic circuit (not shown in  FIGS. 11-12 ) via the respiratory lumen  108 . Preferably, the nasal prongs  102  are of suitable size and shape for insertion into the lower portions of the subject&#39;s  12  nares  104  without unduly blocking the nasal airflows NA into the area  38  within the interface  26 .  
      In addition, the body  106  of the cannula  50  preferably contains an interface orifice  110  on an external surface  112  thereof, particularly for communicating with and/or receiving and/or carrying the interface airflows IA therefrom, as received by and/or in the area  38  within the interface  26 . The interface airflows IA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the interface orifice  110  to an interface lumen  114 . More specifically, the cannula  50  is adapted to receive the interface airflows IA for communication to the pneumatic circuit via the interface lumen  114 .  
      Preferably, the respiratory airflows RA and interface airflows IA are received on opposing sides of a dividing partition  116  internally disposed within the body  106  of the cannula  50 . Preferably, this partition  116  is configured to divide the body  106  of the cannula  50  into one or more chambers, at least one of which is configured to receive the respiratory airflows RA and at least one of which is configured to receive the interface airflows IA.  
      Referring now to  FIGS. 13-14 , an oral cannula  54  is adapted to receive i) mouth airflows MA, and ii) interface airflows IA. More specifically, the oral cannula  54  includes one or more mouth prongs  120  that are adapted to fit within the mouth  34  of the subject  12 , particularly for communicating with and/or receiving and/or carrying the mouth airflows MA therefrom. The mouth airflows MA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the mouth prongs  120  to the respiratory lumen  108 . More specifically, the oral cannula  54  is adapted to receive the mouth airflows MA as respiratory airflows RA for communication to a pneumatic circuit (not shown in  FIGS. 13-14 ) via the respiratory lumen  108 . Preferably, the mouth prongs  120  are of suitable size and shape for insertion into the subject&#39;s  12  mouth  34  without unduly blocking the mouth airflows MA into the area  38  within the interface  26 . Preferably, the horizontal location of the mouth prongs  120  may be the saggital midline of the subject&#39;s  12  mouth  34 . If needed and/or desired, however, it can also be offset from the midline, for example, if there are multiple mouth prongs  120  (only one of which is shown in the figure). In either case, the mouth prongs  120  should be located approximately in the center of the mouth airflows MA in and/or out of the subject&#39;s  12  slightly opened mouth  34 .  
      In addition, the body  106  of the cannula  50  preferably contains the interface orifice  110  on the external surface  112  thereof, particularly for communicating with and/or receiving and/or carrying the interface airflows IA therefrom, as received by and/or in the area  38  within the interface  26 . The interface airflows IA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the interface orifice  110  to the interface lumen  114 . More specifically, the cannula  50  is adapted to receive the interface airflows IA for communication to the pneumatic circuit via the interface lumen  114 .  
      Preferably, the respiratory airflows RA and interface airflows IA are received on opposing sides of the dividing partition  116  internally disposed within the body  106  of the cannula  50 . Preferably, this partition  116  is configured to divide the body  106  of the cannula  50  into the one or more chambers, at least one of which is configured to receive the respiratory airflows RA and at least one of which is configured to receive the interface airflows IA.  
      Referring now to  FIGS. 15-16 , an oro-nasal cannula  56  is adapted to receive i) nasal airflows NA and mouth airflows MA, and ii) interface airflows IA. More specifically, the oro-nasal cannula  56  includes the one or more nasal prongs  102  and one or more mouth prongs  120  of  FIGS. 11-14 , particularly for communicating with and/or receiving and/or carrying the nasal airflows NA and mouth airflows MA therefrom. The nasal airflows NA and mouth airflows MA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the nasal prongs  102  and mouth prongs  120  to the respiratory lumen  108 . More specifically, the oro-nasal cannula  56  is adapted to receive the nasal airflows NA and mouth airflows MA as respiratory airflows RA for communication to a pneumatic circuit (not shown in  FIGS. 15-16 ) via the respiratory lumen  108 , particularly as previously described. This is advantageous, for example, since subjects  12  often alternative between breathing through their nose  32  and mouth  34 , particularly if one is or becomes occluded. In this arrangement, respiratory airflows RA can be suitably sampled from either or both of the subject&#39;s  12  oro-nasal passages.  
      In addition, the body  106  of the cannula  50  preferably contains the interface orifice  110  on the external surface  112  thereof, particularly for communicating with and/or receiving and/or carrying the interface airflows IA therefrom, as received by and/or in the area  38  within the interface  26 . The interface airflows IA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the interface orifice  110  to the interface lumen  114 . More specifically, the cannula  50  is adapted to receive the interface airflows IA for communication to the pneumatic circuit via the interface lumen  114 .  
      Preferably, the respiratory airflows RA and interface airflows IA are received on opposing sides of the dividing partition  116  internally disposed within the body  106  of the cannula  50 . Preferably, this partition  116  is configured to divide the body  106  of the cannula  50  into the one or more chambers, at least one of which is configured to receive the respiratory airflows RA and at least one of which is configured to receive the interface airflows IA.  
      In these  FIG. 11-16  embodiments and others, it is generally preferred to locate the interface orifice  110  on an external surface  112  of the cannula  50  that is generally distal or otherwise removed from the subject  12 , particularly to avoid any possible interference therewith and allow the interface airflows IA to be received thereby without undue hindrance, as needed and/or desired.  
      As described in reference to  FIGS. 11-16 , the respiratory airflows RA and interface airflows IA are preferably received on opposing sides of the dividing partition  116  internally disposed within the body  106  of the cannula  50 . Alternatively, this dividing partition  116  can be eliminated by the embodiments shown in  FIGS. 17-19 .  
      More specifically, referring now to  FIGS. 17-18 , the interface airflows IA are directly received by passing the interface lumen  114  through the body  106  of the cannula  50 . More specifically, instead of configuring the partition  116  to divide the body  106  of the cannula  50  into the one or more chambers, that need can be eliminated if the interface airflows IA are directly connected to the interface lumen  114  through the cannula  50 . For example, the dividing partition  116  in  FIGS. 11-16  separated the respiratory airflows RA and interface airflows IA, particularly so as to not co-mingle. This is similarly accomplished in  FIGS. 17-18  by directly connecting the interface lumen  114  to the interface orifice  110  through the body  106  of the cannula  50 , without the need to otherwise partition the body  106  of the cannula  50  into the one or more chambers.  
      Referring now to  FIG. 19 , the interface airflows IA can also be received in open connection with the area  38  within the interface  26 , in which case the interface lumen  114  is in open communication with the area  38  without aid or other support from the body  106  of the cannula  50 . More specifically, this embodiment eliminates the need to provide the dividing partition  116  of the cannulas  50  of  FIGS. 11-16 , as well as the interface orifice  110  on the external surface  112  of the cannula  50 . Rather, the interface orifice  110  is thus in open connection with the area  38  within the interface  26  without benefit of the cannulas  50 .  
      Referring now to  FIG. 20 , the respiratory airflows RA are received from the respiratory lumens  108  of the cannulas  50  of  FIGS. 11-19 , as well as the interface airflows IA from the interface lumens  114 , via a pneumatic circuit  130  adapted in communication therewith. More specifically, the pneumatic circuit  430  includes a differential pressure transducer P for comparing pressure differentials between the respiratory airflows RA and interface airflows IA, particularly according to the inventive arrangements, such as described in  FIGS. 7-10  and all hereinout, for example. By these arrangements, pressure differentials between the respiratory airflows RA and interface airflows IA can be evaluated without regard to whether the respiratory airflows RA and interface airflows IA are individually increasing or decreasing. Rather, the resulting differential pressures therebetween are determined and/or interpreted for their likely significance as respiratory events and/or non-respiratory events (e.g., likely compressions and/or leaks at the interfaces  26  and/or breathing circuit).  
      Referring now to  FIG. 21 , the pneumatic circuit  130  of  FIG. 20  can also be expanded to include a pressure transducer P gage  in communication with the interface lumen  114  for accurately measuring the pressure at the interface lumen  114  relative to ambient pressure. Alternatively, if the pressure transducer P gage  is instead or additionally connected to the respiratory lumen  108 , the gage pressure signal can be compared to the ventilator&#39;s  22  gage pressure signal to assess whether airflows are entering or exiting the subject  12 , thereby serving as a double-check on the differential pressure transducer P.  
      In addition, a first calibration valve  132  (e.g., a zeroing valve) can be placed in parallel with the differential pressure transducer P for short circuiting the interface lumen  114  and respiratory lumen  108 , and a second calibration valve  134  (e.g., another zeroing valve) can be placed in series with the interface lumen  114  and pressure transducer P gage  for calibrating the pressure transducer P gage . In addition, the respiratory lumen  108  can be cleared of any obstructions therewithin (e.g., mucus, etc.) by providing a purge gas source  136  in communication with the respiratory lumen  108  through a valve  138  (e.g., a 2-way solenoid valve) and/or pressure regulator  140  and/or flow restrictor  142 , the latter of which prevents the respiratory lumen  108  from short circuiting with the interface lumen  114  via the purge lines.  
      These purge components (e.g., purge gas source  136 , valve  138 , pressure regulator  140 , and/or flow restrictor  142 ) can purge the respiratory lumen  108  either periodically or continuously, as needed and/or desired. In addition, the purge can come from a variety of suitable sources, such as, for example, the purge gas source  136  (e.g., an air source), a plumed wall supply (not shown), a purge outlet (not shown) on the ventilator  22 , and/or the like.  
      In addition, a power/communication link  144  can also be provided between the pneumatic circuit  130  and ventilator  22 , particularly for controlling the latter. For example, an output signal S from the differential pressure transducer P, which can be integrated with, proximal, or distal the cannula  50  to which it is attached and/or in communication with (but not otherwise shown in  FIGS. 20-21 ), can be directed to the ventilator  22 , which is configured to respond to the pressure differentials. Accordingly, the differential pressure transducer P is configured to effectuate a change in a breathing circuit of a subject  12  in response to the sensed pressure differentials by the differential pressure transducer P, and improved ventilator control is thereby provided, delivering ventilated support that is synchronized with the subject&#39;s  12  own respiratory efforts, leaks and/or compressions notwithstanding.  
      Referring now to  FIG. 22 , the oro-nasal cannula  56  has been re-configured to receive i) nasal airflows NA as first respiratory airflows 1 st  RA, ii) mouth airflows MA as second respiratory airflows 2 nd  RA, and iii) interface airflows IA. More specifically, the oro-nasal cannula  56  includes the one or more nasal prongs  102  and one or more mouth prongs  120  of  FIGS. 11-19 , particularly for communicating with and/or receiving and/or carrying the nasal airflows NA and mouth airflows MA therefrom. However, the nasal airflows NA are communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the nasal prong  102  to a first respiratory lumen  108   a , while the mouth airflows MA are communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the mouth prong  120  to a second respiratory lumen  108   b . More specifically, the oro-nasal cannula  56  is adapted to receive the nasal airflows NA as first respiratory airflows 1 st  RA for communication to the pneumatic circuit (not shown in  FIG. 22 ) via the first respiratory lumen  108   a , while the oro-nasal cannula  56  is adapted to receive the mouth airflows MA as second respiratory airflows 2 nd  RA for communication to the pneumatic circuit via the second respiratory lumen  108   b . Internally within the body  106  of the oro-nasal cannula  56  of  FIG. 22 , the nasal airflows NA and mouth airflows MA are separable and distinct, whereas in  FIGS. 15-18 , for example, they can be combined therewithin the body  106  of the cannula  50 .  
      As previously described, the body  106  of the cannula  50  still preferably contains the interface orifice  110  on an external surface  112  thereof, particularly for communicating with and/or receiving and/or carrying the interface airflows IA therefrom, as received by and/or in the area  38  within the interface  26 . The interface airflows IA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the interface orifice  110  to the interface lumen  114 , as before. More specifically, the cannula  50  is adapted to receive the interface airflows IA for communication to the pneumatic circuit via the interface lumen  114 , and they can be received by either or both of the portions of the cannula  50  that receive the nasal airflows NA (as shown in the figure) and/or the mouth airflows (not shown in the figure, but easily understood).  
      Preferably, the respiratory airflows RA—whether they are the first respiratory airflows 1 st  RA from the nasal airflows NA and/or second respiratory airflows 2 nd  RA from the mouth airflows MA—and interface airflows IA are received on opposing sides of the dividing partition  116  internally disposed within the body  106  of the cannula  50 . Preferably, this partition  116  is configured to divide at least a portion of the body  106  of the cannula  50  into the one or more chambers, at least one of which is configured to receive the above-described respiratory airflows RA and at least one of which is configured to receive the above-described interface airflows IA.  
      Referring now to  FIG. 23 , the first respiratory airflows 1 st  RA are received from the first respiratory lumen  108   a  of the oro-nasal cannula  56  of  FIG. 22 , as well as the second respiratory airflows 2 nd  RA from the second respiratory lumen  108   b , as well as the interface airflows IA from the interface lumens  114 , all via the pneumatic circuit  130 ′ adapted in communication therewith. More specifically, the pneumatic circuit  130 ′ now includes a first differential pressure transducer P 1  for comparing pressure differentials between the first respiratory airflows 1 st  RA and interface airflows IA, as well as a second differential pressure transducer P 2  for comparing pressure differentials between the second respiratory airflows 2 nd  RA and interface airflows IA, particularly according to the inventive arrangements, such as described in  FIGS. 7-10  and all hereinout, for example. By these arrangements, pressure differentials between the first respiratory airflows 1 st  RA and interface airflows IA, as well as between the second respiratory airflows 2 nd  RA and interface airflows IA, can be evaluated without regard to whether the first respiratory airflows 1 st  RA and/or second respiratory airflows 2 nd  RA and interface airflows IA are individually increasing or decreasing. Rather, the resulting differential pressures therebetween are determined and/or interpreted for their likely significance as respiratory events and/or non-respiratory events (e.g., likely compressions and/or leaks at the interfaces  26  and/or breathing circuit).  
      Referring now to  FIG. 24 , the pneumatic circuit  130 ′ of  FIG. 23  can also be expanded to include the pressure transducer P gage  in communication with the interface lumen  114  for accurately measuring the pressure at the interface lumen  114  relative to ambient pressure. Alternatively, if the pressure transducer P gage  is instead or additionally connected to the first respiratory lumen  108   a  and/or second respiratory lumen  108   b , the gage pressure signal can be compared to the ventilator&#39;s  22  gage pressure signal to assess whether airflows are entering or exiting the subject  12 , thereby serving as a double-check on the first differential pressure transducer P 1  and/or second differential pressure transducer P 2 .  
      In addition, a first calibration valve  132   a  (e.g., a zeroing valve) can be placed in parallel with the first differential pressure transducer P 1  for short circuiting the interface lumen  114  and first respiratory lumen  108   a , as well as another calibration valve  132   b  (e.g., another zeroing valve) in parallel with the second differential pressure transducer P 2  for short circuiting the interface lumen  114  and second respiratory lumen  108   b , and a second calibration valve  134  can be placed in series with the interface lumen  114  and pressure transducer P gage  for calibrating the pressure transducer P gage . In addition, the first respiratory lumen  108   a  and/or second respiratory lumen  108   b  can be cleared of any obstructions therewithin (e.g., mucus, etc.) by providing the purge gas source  136  in communication with the first respiratory lumen  108   a  and/or second respiratory lumen  108   b  through a valve  138  (e.g., a 2-way solenoid valve) and/or pressure regulator  140  and/or flow restrictors  142 , the latter of which prevents the first respiratory lumen  108   a  and/or second respiratory lumen  108   b  from short circuiting with the interface lumen  114  via the purge lines.  
      These purge components (e.g., purge gas source  136 , valve  138 , pressure regulator  140 , and/or flow restrictor  142 ) can purge the first respiratory lumen  108   a  and/or second respiratory lumen  108   b  either periodically or continuously, as needed and/or desired. In addition, the purge can come from a variety of suitable sources, such as, for example, the purge gas source  136  (e.g., an air source), a plumed wall supply (not shown), a purge outlet (not shown) on the ventilator  22 , and/or the like.  
      In addition, a power/communication link  144  can also be provided between the pneumatic circuit  130 ′ and ventilator  22 , particularly for controlling the latter. For example, an output signal S from the first differential pressure transducer P 1  and/or second differential pressure transducer P 2 , which can be integrated with, proximal, or distal the cannula  50  to which they are attached and/or in communication therewith (but not otherwise shown in  FIGS. 23-24 ), can be directed to the ventilator  22 , which is configured to respond to the pressure differentials. Accordingly, the first differential pressure transducer P 1  and/or second differential pressure transducer P 2  are configured to effectuate a change in a breathing circuit of the subject in response to the sensed pressure differentials by the first differential pressure transducer P 1  and/or second differential pressure transducer P 2 , and improved ventilator control is thereby provided, delivering ventilated support that is synchronized with the subject&#39;s  12  own respiratory efforts, leaks and/or compressions notwithstanding.  
      In addition, the inventive arrangements can be arranged to monitor exhaled gases, such as carbon dioxide CO 2 , in addition to the respiratory airflows RA and interface airflows IA.  
      Referring now to  FIGS. 25-27 , for example, the nasal prongs  102  and/or mouth prongs  120  can be bifurcated to receive both i) nasal airflows NA and/or mouth airflows MA, as well as ii) nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2 . More specifically, either or both of the nasal prongs NA and/or mouth prongs MA contain an internal dividing wall  150  therewithin to separate collection of i) the nasal airflows NA and/or mouth airflows MA from ii) the nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2 . The nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2  are representative of exhaled gases that can be sampled by the oro-nasal cannula  56  in  FIGS. 25-34 , with other exhaled gases and/or other cannulas  50  being likewise suitably arranged (but not otherwise shown in  FIGS. 25-27 ).  
      More specifically, the oro-nasal cannula  56  includes the familiar one or more nasal prongs  102  and one or more mouth prongs  120  of  FIGS. 11-19 , particularly for communicating with and/or receiving and/or carrying the nasal airflows NA and mouth airflows MA therefrom. However, the one or more nasal prongs  102  and one or more mouth prongs  120  are also now configured to communicate with and/or receive and/or carry the nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2  therefrom as well.  
      As per the particular oro-nasal cannula  56  of  FIG. 22 , it has been re-configured to receive i) nasal airflows NA as first respiratory airflows 1 st  RA, ii) mouth airflows MA as second respiratory airflows 2 nd  RA, iii) interface airflows IA, and iv) respiratory carbon dioxide R CO 2 . As previously described, the nasal airflows NA are again communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the nasal prong  102  to the first respiratory lumen  108   a , while the mouth airflows MA are again communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the mouth prong  120  to the second respiratory lumen  108   b . As previously described, the oro-nasal cannula  56  is again adapted to receive the nasal airflows NA as first respiratory airflows 1 st  RA for communication to the pneumatic circuit (not shown in  FIGS. 25-27 ) via the first respiratory lumen  108   a , as well as again adapted to receive the mouth airflows MA as second respiratory airflows 2 nd  RA for communication to the pneumatic circuit  130 ′ via the second respiratory lumen  108   b.    
      As previously described, the body  106  of the cannula  50  still preferably contains the interface orifice  110  on an external surface  112  thereof, particularly for communicating with and/or receiving and/or carrying the interface airflows IA therefrom, as received by and/or in the area  38  within the interface  26 . Again, the interface airflows IA are then communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the interface orifice  110  to the interface lumen  114 , as before, as well as including arrangements such as i) the dividing partition  116  internally disposed within the body  106  of the cannula  50  to divide the same into the one or more chambers, at least one of which is configured to receive the respiratory airflows RA and at least one of which is configured to receive the interface airflows IA, ii) the direct connection (e.g., see  FIG. 18 ), or iii) the open connection (e.g., see  FIG. 19 )—all as previously described.  
      Now then, while the nasal airflows NA and mouth airflows MA continue to be communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the nasal prongs  102  and/or mouth prongs  120  to the first respiratory lumen  108   a  and/or second respiratory lumen  108   b , the nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2  are also communicated by and/or received by and/or carried by the body  106  of the cannula  50  from the nasal prongs  102  and/or mouth prongs  120  to a respiratory carbon dioxide lumen  152 . More specifically, the oro-nasal cannula  56  is now adapted to receive the nasal carbon dioxide N CO 2  and/or mouth carbon dioxide M CO 2  as the respiratory carbon dioxide R CO 2  for communication to a pneumatic circuit (not shown in  FIGS. 25-27 ) via the respiratory carbon dioxide lumen  152 .  
      As described, the nasal prong  102  and/or mouth prong  120  preferably contain the internal dividing wall  150  therewithin to separate i) the nasal airflows NA from the nasal carbon dioxide N CO 2 , and/or ii) the mouth airflows MA from the mouth carbon dioxide M CO 2 , each preferably having its own receiving orifice  154  at a distal end of the appropriate prong  102 ,  120 .  
      Preferably, the exhaled gas sampling portion of the prong  102 ,  120  is set back from the respiratory sampling portion of the prong by a suitable distance d, as shown in  FIG. 27 . Preferably, this setback is chosen to minimize the interference therebetween, particularly enabling accurate sampling of the exhaled gases. In other words, for example, the particular receiving orifice  154   a  for the nasal airflows NA is preferably non co-planar with the particular receiving orifice  154   b  for the nasal carbon dioxide N CO 2 , as represented by the suitable distance d 1 . In like fashion, for example, the particular receiving orifice  154   c  for the mouth airflows MA is preferably non co-planar with the particular receiving orifice  154   d  for the mouth carbon dioxide M CO 2 , as again represented by the suitable distance d 2 . These suitable distances d 1 , d 2  may be the same or different, with i) d 1 =d 2  (i.e., as shown), or ii) d 1 &gt;d 2 , or iii) d 1 &lt;d 2 , or iv) d 1 =0, and/or v) d 2 =0, as needed and/or desired.  
      If the afore-described setback is carried along the entire length of the prong  102 ,  120 , an arrangement such as that depicted in  FIGS. 28-31  can be achieved, in which the exhaled gas sampling portion of the nasal prong  102 , for example, can instead be carried on the external surface  112  of the body  106  of the cannula  50 , suitably now arranged as one or more exhaled gas orifices  156  for receiving the same. This alternatively eliminates the need to bifurcate the prongs  102 ,  120 , in which the applicable receiving orifices  154   b ,  154   d  for the exhaled gases on the prongs  102 ,  120  can be suitably replaced by the exhaled gas orifices  156  carried on the external surface  112  of the body  106  of the cannula  50 .  
      Also in  FIGS. 28-31 , for example, the bifurcated mouth prong  120  of  FIGS. 25-27 , for example, can be replaced by multiple mouth prongs  120   a ,  120   b , at least one mouth prong  120   a  of which is configured to receive the mouth airflows MA and another of which mouth prong  120   b  is configured to receive the mouth carbon dioxide M CO 2 . Although not necessarily shown in the figures, the multiple prongs  120   a ,  120   b  can again be offset by suitable distance d, as representatively shown more specifically in  FIG. 27  (but equally as applicable here), again as needed and/or desired.  
      While several of the above-described modifications to  FIGS. 25-27  were reflected in  FIGS. 28-31  as applying to one or the other of the nasal prong  102  and/or mouth prong  120 , these modifications were only representatively depicted. For example, while the bifurcated nasal prong  102  was altered to include the exhaled gas orifices  156 , the bifurcated mouth prong  120  can also be similarly altered. Likewise, while the bifurcated mouth prong  120  was altered to include the multiple mouth prongs  120   a ,  120   b , the bifurcated nasal prong  120  can also be similarly altered. Accordingly, any or all of these changes may be made separately and/or together, as needed and/or desired.  
      As previously described in  FIGS. 28-31 , the exhaled gas sampling portion of the nasal prong  102 , for example, can be carried on the external surface  112  of the body  106  of the cannula  50 , suitably arranged as one or more exhaled gas orifices  156  for receiving the same. This arrangement can be further enhanced by a configuration shown in  FIGS. 32-33 , for example, in which the exhaled gas capture by the exhaled gas orifices  156  is assisted by a capture enhancer  158 , such as shield or wall or block or the like, operative in communication therewith. More specifically, the capture enhancer  158  is preferably affixed to the external surface  112  of the cannula  50  by a rib  160  and/or the like, and suitably shaped and sized to channel or otherwise capture the exhaled gases into the exhaled gas orifices  156 . It can take numerous alternative forms as well, such as a scooped prong  162 , for example, to receive the mouth carbon dioxide M CO 2  as well, again suitably shaped and sized to channel or otherwise capture the exhaled gases.  
      While several of the above-described modification to  FIGS. 28-31  were reflected in  FIGS. 32-33  as applying to one or the other of the nasal prong  102  or mouth prong  120 , these modifications were only representatively depicted. For example, while the capture enhancer  158 , such as the shield or wall or block or the like, was applied towards the nasal prongs  102  to assist the nasal carbon dioxide N CO 2  capture, it can be readily applied to the mouth prongs  120  as well to assist the mouth carbon dioxide M CO 2  capture. Likewise, while the scooped prong  162  was applied towards the mouth prongs  120  to assist the mouth carbon dioxide M CO 2  capture, it can be readily applied to the nasal prongs  102  as well to assist the nasal carbon dioxide N CO 2  capture. Accordingly, any or all of these changes may be made separately and/or together, as needed and/or desired.  
      Referring now to  FIG. 34 , the captured exhaled gases can be routed to a gas analyzer  170 . More specifically, in any or all of the  FIG. 25-33  embodiments, the exhaled gases can be analyzed in the area  38  within the interface  26 , particularly as needed and/or desired. Accordingly, the exhaled gases may be drawn out of the cannulas  50  using suction or a pump (not shown). In any event, the pneumatic circuit  130 ′ of  FIG. 24  can now be expanded to include the afore-mentioned gas analyzer  170 , configured to receive the exhaled gases from the respiratory carbon dioxide lumen  152 .  
      In addition, a power/communication link  172  can also be provided between the gas analyzer  170  and ventilator  22 , particularly for controlling the latter. Accordingly, the pneumatic circuit  130 ′ is now configured to effectuate a change in a breathing circuit of a subject  12  in response to the sensed pressure differentials by the first differential pressure transducer P 1  and/or second differential pressure transducer P 2  and the exhaled gases by the gas analyzer  170 , and improved ventilator control is thereby provided, delivering ventilated support that is synchronized with the subject&#39;s  12  own respiratory efforts, leaks and/or compressions notwithstanding, with the remainder of the pneumatic circuit  130 ′ corresponding to  FIG. 24 , now with even more enhanced ventilator control.  
      And referring finally to  FIG. 35 , many of the above-described features are presented in various combinations as a further convenience to the reader in a table  180 .  
      Accordingly, it should be readily apparent that this specification describes illustrative, exemplary, representative, and non-limiting embodiments of the inventive arrangements. Accordingly, the scope of the inventive arrangements are not limited to any of these embodiments. Rather, various details and features of the embodiments were disclosed as required. Thus, many changes and modifications—as readily apparent to those skilled in these arts-are within the scope of the inventive arrangements without departing from the spirit hereof, and the inventive arrangements are inclusive thereof. Accordingly, to apprise the public of the scope and spirit of the inventive arrangements, the following claims are made: