Abstract:
Described herein is a mask for delivery of gas, such as oxygen, to a patient and useable in a naso-gastric intubation procedure without disruption of the seal between the mask and the patient&#39;s face. The body of the mask includes a fenestration or opening through which the naso-gastric tube may be inserted. The fenestration is preferably shaped to support the tube in a manner that is comfortable for the patient and that eliminates or minimizes the amount of gas lost to the atmosphere outside the mask. In at least some embodiments, the fenestration is closed when a tube is not inserted therethrough so that the mask may be used normally without loss of the gas through the fenestration.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application is related to U.S. patent application Ser. No. 13/105,738 entitled ADJUSTING A VENTILATION MASK, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,757 entitled CORRUGATED FLEXIBLE SEAL OF A VENTILATION MASK, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,773 entitled NASAL PASSAGE OPENER OF A VENTILATION MASK, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,782 entitled A CARBON-DIOXIDE SAMPLING DEVICE FOR NONINVASIVELY MEASURING CARBON DIOXIDE IN EXHALED BREATH, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,840 entitled A CARBON-DIOXIDE SAMPLING SYSTEM FOR ACCURATELY MONITORING CARBON DIOXIDE IN EXHALED BREATH, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,793 entitled INTERCHANGEABLE INSERTS, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,807 entitled LATERAL GAS LINE CONFIGURATION, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,821 entitled QUICK DONNING HEADGEAR, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,829 entitled SMART CONNECTIONS, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,851 entitled NON-INVASIVE VENTILATION EXHAUST GAS VENTING, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,861 entitled NON-INVASIVE VENTILATION FACIAL SKIN PROTECTION, filed May 11, 2011. 
     This Application is related to U.S. patent application Ser. No. 13/105,871 entitled NON-INVASIVE VENTILATION FACIAL SKIN PROTECTION, filed May 11, 2011. 
     BACKGROUND 
     Non-invasive ventilation involves the delivery of fresh respiratory gases to a patient through a non-invasive means such as a mask, hood, or helmet rather than through an invasive means such as an endotracheal tube inserted via an oral, nasal, or tracheal opening in a patient. Continuous positive airway pressure (CPAP) ventilation and bi-level ventilation are two specific techniques of non-invasive ventilation. CPAP ventilation, as implied by the name, provides a continuous pressure of air during ventilation which maintains the airway in an open state and thus can fill the lungs with air thus requiring less work from respiratory muscles. CPAP is often used for patients with respiratory failure or near respiratory failure and for individuals with sleep apnea. Hi-level or variable level ventilation is often used for sleep apnea patients and for non-invasive ventilation for respiratory insufficiency or failure in institutional and home setting and is similar to CPAP, except that pressure is varied during inspiration and expiration. For example, pressure is lowered during expiration to ease exhalation. Compared with invasive ventilation, non-invasive ventilation can result in lower patient stress levels and lower trauma to patient airways. As such, non-invasive ventilation techniques offer more patient comfort than invasive ventilation techniques. 
     There are three major components involved in non-invasive ventilation: a ventilator which is an item of hardware which supplies fresh respiratory gas(es); a patient interface such as a mask; and a breathing circuit (i.e., tubes and connectors) that couple the ventilator with mask such that the fresh respiratory gases can be supplied to the patient for breathing. There are generally two techniques of non-invasive ventilation that are commonly in use: single limb, and dual limb. 
     Single limb breathing circuit applications involve blowing high flow levels of fresh respiratory gas into the patient interface, and relying on vent ports in the patient interface for allowing exhaled respiratory gases to exit the patient interface into the atmosphere. Vent ports or vents are designated leakage points that allow for a controlled leakage, or venting, of fresh respiratory gases in order to maintain a desired pressure of respiratory gases within a patient interface and to clear exhaled carbon dioxide. “Single limb” refers to the fact that a ventilation limb or limbs coupled with a patient interface only supply fresh respiratory gas and do not provide a return path for exhaled gases. As such, in some “single limb” applications a fresh respiratory gas supply tube may split into two or more tubes/limbs that allow fresh respiratory gas to enter a patient interface via more than one location. Because of the presence and reliance on vents, single limb non-invasive ventilation is also referred to as vented non-invasive ventilation. 
     Dual limb breathing circuit applications involve respiratory gases being blown into a patient interface via a first limb and exhaust gases being evacuated from the patient interface via a second, separate limb. Because of the second limb which is used for evacuation of exhaust gases, no vents are needed in the patient interface for venting exhaust gases into the atmosphere. Because no vents are required, dual limb non-invasive ventilation is also referred to as non-vented non-invasive ventilation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this application, illustrate embodiments of the subject matter, and together with the Description of Embodiments, serve to explain the principles of the embodiments of the subject matter. Unless noted, the drawings referred to in this brief description of drawings should be understood as not being drawn to scale. 
         FIG. 1  shows a front perspective view of an example non-invasive ventilation system, in accordance with various embodiments. 
         FIG. 2  is rear perspective of a patient interface of a non-invasive ventilation system, in accordance with various embodiments. 
         FIG. 3  shows a front perspective view of patient interface of a non-invasive ventilation system and illustrates a removal/insertion of an interchangeable patient interface insert, in accordance with an embodiment. 
         FIG. 4  shows a front perspective view of patient interface of a non-invasive ventilation system and illustrates an interchangeable patient interface insert which includes a self-sealing access port, in accordance with an embodiment. 
         FIG. 5  shows a front perspective view of patient interface of a non-invasive ventilation system and illustrates an interchangeable patient interface insert which includes a breath sampling port, in accordance with an embodiment. 
         FIG. 6  shows a front perspective view of patient interface of a non-invasive ventilation system and illustrates a self-sealing gastric tube insertion region disposed within the facial skin interface, in accordance with an embodiment. 
         FIG. 7  shows a front perspective view of a doffed patient interface of a non-invasive ventilation system, in accordance with an embodiment, and also illustrates an interchangeable patient interface insert which includes built-in filter media, in accordance with an embodiment. 
         FIGS. 8A and 8B  shows front perspective views of patient interfaces of a non-invasive ventilation system which are configured with a zygomatic facial interface and illustrate interchangeable patient interface inserts which include an aviator style fresh respiratory gas interface, in accordance with various embodiments. 
         FIG. 9  shows a method for adjusting a ventilation mask, in accordance to an embodiment. 
         FIG. 10  shows a method for adjusting a ventilation mask, in accordance to an embodiment. 
         FIG. 11  shows a method for assisting in opening a nasal passage, in accordance to an embodiment. 
         FIG. 12  shows a front perspective view of a non-invasive patient interface with carbon-dioxide sampling device for non-invasively measuring carbon dioxide in exhaled breath, in accordance with an embodiment. 
         FIG. 13  shows a cross-sectional view of the non-invasive patient interface of  FIG. 12  illustrating the carbon-dioxide sampling device including a carbon dioxide collector, in accordance with an embodiment. 
         FIG. 14  shows a schematic diagram of a carbon-dioxide analyzer for converting a sample of exhaled breath from the patient into a measurement of carbon dioxide content in the sample of exhaled breath from the patient, in accordance with an embodiment. 
         FIG. 15  shows a schematic diagram of an alternative embodiment for the carbon-dioxide analyzer for converting a sensor signal form a carbon-dioxide sensor into a measurement of carbon dioxide content in a sample of exhaled breath from the patient, in accordance with an embodiment. 
         FIG. 16  shows a flowchart of a method for non-invasively measuring carbon dioxide in exhaled breath, in accordance with an embodiment. 
         FIG. 17  shows a schematic diagram of a carbon-dioxide sampling system for accurately monitoring carbon dioxide in exhaled breath, in accordance with an embodiment. 
         FIG. 18  shows a front perspective view of the non-invasive patient interface of a combined non-invasive patient interface and carbon-dioxide sampling system, in accordance with an embodiment. 
         FIG. 19  shows a schematic diagram of a carbon-dioxide analyzer including a carbon-dioxide sensor configured to sense a level of carbon dioxide in exhaled breath of the patient, in accordance with an embodiment. 
         FIG. 20  shows a schematic diagram of a combination carbon-dioxide measurement display and recorder, in accordance with an embodiment. 
         FIG. 21  shows a flowchart of a method for accurately monitoring carbon dioxide in exhaled breath, in accordance with an embodiment. 
         FIG. 22  is a flow diagram of an exemplary method for accessing a respiratory opening of a patient without removing a ventilation mask in accordance with an embodiment. 
         FIG. 23  is shows a front perspective view of a doffed patient interface of a non-invasive ventilation system with a smart component, in accordance with an embodiment, and also illustrates a ventilator with capability of determining system configuration, in accordance with an embodiment. 
         FIG. 24  is a flow diagram of an exemplary method for determining continuity of a ventilation system in accordance with an embodiment. 
         FIG. 25  is a flow diagram of an exemplary method for determining configuration of a ventilation system in accordance with an embodiment. 
         FIGS. 26A-26C  illustrate detail views of a self-sealing tube insertion region, according to various embodiments. 
         FIG. 27  illustrates a replaceable filter cartridge, in accordance with an embodiment. 
         FIG. 28  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal and a facial skin interface, according to an embodiment. 
         FIG. 29  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal and a facial skin interface, according to an embodiment. 
         FIG. 30  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal and a facial skin interface, according to an embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. While the subject matter will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the subject matter to these embodiments. On the contrary, the subject matter described herein is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope. Furthermore, in the following description, numerous specific details are set forth in order to provide a thorough understanding of the subject matter. However, some embodiments may be practiced without these specific details. In other instances, well-known structures and components have not been described in detail as not to unnecessarily obscure aspects of the subject matter. 
     Overview of Discussion 
     Herein, various embodiments of a non-invasive ventilation patient interface, system, and components thereof are described. Various embodiments described herein can be utilized across the spectrum of non-invasive ventilation, from spontaneously breathing patients who need some respiratory assistance to patient who are unable to breathe without mechanical assistance. For purposes of the present description, it should be appreciated that many of the described patient interface embodiments may be utilized with both single limb and dual limb ventilation applications, and may in many cases be switched over from one to another by reconfiguring a ventilator and in some instances reconfiguring or replacing one or more components. Description begins with a general discussion of major components and features associated with the non-invasive ventilation technology described herein. This general discussion provides a framework of understanding for more particularized description which follows in thirteen separate sections. These thirteen sections are dedicated and focused on detailed discussion of particular features and concepts of operation associated with one or more embodiments of the described non-invasive ventilation technology. 
     Major Components and Features 
       FIG. 1  shows a front perspective view of an example non-invasive ventilation system  100 , in accordance with various embodiments. Non-invasive ventilation system  100  comprises three major components, patient interface  110  (also referred to herein as mask  110 ), breathing circuit  140 , and ventilator  160 . Ventilator  160  supplies fresh breathable respiratory gas such as oxygen or other repertory gas(es). Breathing circuit  140  fluidly couples the fresh respiratory gas from ventilator  160  to patient interface  110 . Patient interface  110  sealably couples in a controlled seal (controlled in the sense that intentional leaks are permitted while unintentional leaks are reduced or eliminated) over at least one respiratory opening of patient  101  to form a hollow chamber into which fresh respiratory gas is coupled via breathing circuit  140 . Although patient interface  110  is illustrated in  FIG. 1  and throughout as covering both the nasal and oral cavities (nose and mouth), some embodiments may cover only a nasal cavity or oral cavity, or may capture the entire face or head of a patient. Thus, in general, embodiments of patient interface  110  can be said to couple in a controlled seal over a respiratory opening of a patient, where a respiratory opening may include a nasal cavity, an oral opening, both the nasal and oral cavities of a patient, the entire face of a patient (encompassing the nasal and oral cavities), or the entire head of a patient (encompassing the nasal and oral cavities). 
     As illustrated, respiratory gas tube  141  and y-piece  142  provide a tubular path for fluidly coupling limbs  143  and  144  of patient interface  110  with ventilator  160 . In some embodiments, y-piece  142  may include one or more swiveling portions to relieve torque and allow for articulation of breathing circuit  140 . In some embodiments, limbs  143  and  144  may both be inhalation gas supply lines for supplying fresh respiratory gas for breathing by patient  101 . In other embodiments, one of limbs  143  or  144  acts as an inhalation gas supply line, while the other of limbs  143  and  144  acts as an exhalation gas collection line for collecting exhaust gas (exhaled breath and unused respiratory gases) from patient  101 . Although limb  143  is illustrated herein as a single tube, it is appreciated that, in some embodiments, limb  143  may be a plurality of smaller tubes. Such a configuration of limb  143  facilitates the plurality of smaller tube lying more or less flatly against and flexibly following the contour of the face of patient  101  or of a side strap of head strap system  111 . Similarly, although limb  144  is illustrated herein as a single tube, it is appreciated that, in some embodiments, limb  144  may be a plurality of smaller tubes. Such a configuration of limb  144  facilitates a the plurality of smaller tubes lying more or less flatly against and flexibly following the contour of the face of patient  101  or of a side strap of head strap system  111 . 
     In one embodiment, respiratory gas tube  141  fluidly couples with ventilator  160  via a respiratory gas port  161 . All though not depicted in  FIG. 1 , in some embodiments, ventilator  160  may include a plurality of respiratory gas ports and/or other ports such as exhaled gas return port(s) and/or a carbon dioxide monitoring port. In some embodiments, respiratory gas port  161  and/or other connections and tubes in breathing circuit  140  may, among other things, self-identify to ventilator  160  whether patient interface  110  is a vented or non-vented patient interface and/or whether patient interface  110  is a neonatal, child, or adult patient interface. Furthermore, in some embodiments, connectors and ports of breathing circuit  140  are designed such at they only couple with compatible components. Thus, in one embodiment, neonatal connectors would only couple with a neonatal patient interface and a neonatal respiratory gas port  161 . In one embodiment, child connectors would only couple with a child patient interface and a child respiratory gas port  161 . In one embodiment, adult connectors would only couple with an adult patient interface and an adult respiratory gas port  161 . These and other features of a “smart connection” protocol will be described further herein in a separate section below. 
     Anti-asphyxia valve(s)  145  ( 145 - 1 ,  145 - 2 ) are provided, in some embodiments, as a safety mechanism in case the flow of fresh respiratory gas fails or is interrupted. Anti-asphyxia valves  145  fail in an open position in the external atmosphere, so that the anti-asphyxia valve will open to the atmosphere to keep the patient from suffocating. 
     Patient interface  110  comprises a frame  125 , a facial skin interface  130 , a compliant nose bridge seal  135 , a domed front portion  120  (which may be fixed or may be a removable/interchangeable insert), and a head strap system  111 . 
     Head strap system  111  includes a plurality of side straps  112  ( 112 - 1 ,  112 - 2 , and  112 - 3 ,  112 - 4  (not visible in  FIG. 1 , but illustrated in  FIG. 7 )) which couple with frame  125 . Upper left side strap  112 - 1  and lower left side strap  112 - 2  couple head strap system  111  from a left lateral portion of frame  125  around the posterior skull of patient  101  and to upper right side strap  112 - 3  and lower right side strap  112 - 4 . Upper right side strap  112 - 3  and lower right side strap  112 - 4  couple with a right lateral portion of frame  125 . Side straps  112  are adjustable such that they may apply an adjustable securing force to secure nose bridge seal  135  and facial skin interface  130  of patient interface in position over one or more respiratory openings of patient  101 . Adjustment of side straps  112  facilitates adjusting the fitment and seal of facial skin interface  130  to accommodate variety of patient facial sizes and shapes. 
     Side straps  112  couple with retention portions of frame  125 , while limbs  143  and  144  swivelably couple with gas ports (also referred to as orifices) disposed as portions of frame  125 . These retention portions and gas port connection features/orifices are be better illustrated and farther discussed in conjunction with  FIG. 7 . 
     Facial skin interface  130  is coupled with nose bridge seal  135  and is disposed between frame  125  and the chin and cheek regions of patient  101 . The general structure of facial skin interface  130  is such that there is a flexible material in contact with the face of patient  101 , this allows for some movement of the patient while maintaining a seal with the face of patient  101  so that respiratory gases do not uncontrollably leak out from between facial skin interface  130  and the facial skin of patient  101 . The flexible material may be silicone, Thermo Plastic Elastomer (TPE), two-layer or multi-layer plastic, a material of variable wall thickness, a combination of elastic and plastic materials, or other flexible material(s) that are known in the art. Herein flexible means that the material is capable of flexing to conform to a surface, such as a facial feature of a patient. In some embodiments, the flexible material is thinner at locations where it will contact the face of a patient and it gets more and more thick the further it gets from the patient contact area. This increasing thickness provides some increased rigidity and provides structure. Herein, “rigid” means that a material does not tend to flex to conform to a surface, such as a facial feature of a patient. While rigidity is desired in some portions of a patient interface, lack of flexibility in regions of a patient interface which come into contact with facial skin contributes to increased unintentional leakage and also creates pressure points which can skin necrosis in a relatively short period of time. Necrosis is the premature death of skin cells and can be caused by pressure point trauma and decreased blood circulation as a result of pressure applied to facial skin by a patient interface. As will be further described, in some embodiments facial skin interface  130  may incorporate one or more additional features to allow for increased flexibility (e.g., to allow some movement and articulation of facial skin interface  130 ) in order to alleviate pressure points and improve patient comfort while still maintaining fit such that patient ventilation is not disrupted by uncontrolled leakage of respiratory gases. Segmented sections, corrugations, ridges, bladders, and bellows are some examples of these additional features. 
     In general, human nasal bridge has only a very thin layer of skin covering the nasal bone structures and flexible nasal cartilage. Because of this, the nasal bridge very susceptible to skin necrosis caused by pressure points. Additionally, portions of the nasal passages very easily pinch, crush, or slightly collapse in response to applied pressure. Compliant nose bridge seal  135  couples with left and right lateral portions of facial skin interface  130  and also couples between an upper portion of frame  125  and the nasal bridge of patient  101 . Compliant nose bridge seal  135  is very flexible and, as such, complies with the shape of the nasal bridge of patient  101  in response to donning of patient interface  110 . Although side straps  112  of head strap system  111  provide a securing force, the positioning of side straps  112  on frame  125  allow this securing force to be distributed via frame  125  to facial skin interface  130 . In this manner, facial skin interface  130  mostly or entirely transfers the securing force to the chin and cheek bone/zygomatic arch regions of the face of patient  101 , while little of none of the securing force is transferred to the nasal bridge of patient  101 . Instead of relying on securing force of head strap system  111  to form a seal, compliant nose bridge seal  135  employs one or more other mechanisms such as corrugated sections, inflatable/inflated bladders, medical grade foam, and/or adhesive. In some embodiments, as will be described herein, when an adhesive, such as a hydro gel or pressure sensitive adhesive is utilized, nose bridge seal  135  may actually be configured to expand outward from the sides of the nose of patient  101  so as to impart a negative or outward force on the nasal bridge region of patient  101 , while still performing a sealing function. Such an outward force will slightly open the nasal passageways of patient  101 , rather than pinching them closed. 
     Domed front portion  120  is, in one embodiment, made of a transparent material which allows a medical care professional visibility of the oral and nasal cavities of patient  101 . Domed front portion  120  is sealably coupled with frame  125  and, in conjunction with nose bridge seal  135 , facial skin interface  130 , and frame  125 , forms a breathing chamber from which patient  101  may inhale fresh respiratory gas and into which patient  101  may exhale. In vented non-invasive ventilation, domed front portion  120  may include one or more exhaust gas vent ports  123  that allow expulsion of exhaust gas from patient interface  110  in response to exhalation of patient  101 . In some embodiments, the size and arrangement of vent ports  123  is selected to allow fresh respiratory gases to escape at a predetermined flow rate in order to assist in controlling the pressure the fresh respiratory gases near a respiratory opening (nose, mouth, or nose and mouth) of patient  101 . 
     As previously described, in some embodiments domed front portion  120  is a removably coupled portion of patient interface  110 . In removably coupled embodiments, domed front portion  120  may be removed from patient interface  110  while the remainder of patient interface  110  remains in place on patient  101 . Such removal of a removable coupled domed front portion  120  can be accomplished for a variety of reasons, including: to facilitate oral care of patient  101 , to facilitate administration of oral or aerosolized medication to patient  101 , to improve comfort of patient  101 , to facilitate speech of patient  101 , to clear debris (e.g., vomit, saliva, blood, etc.) from the airway or from within patient interface  110 , and facilitate insertion and/or removal of oral or nasal tubes or medical instruments. As will be described, in some embodiments, one or more different features may be incorporated into a domed front portion  120 . In some embodiments, a domed front portion  120  may be removed and interchangeably replaced with another domed front portion (which may offer a feature not included in the replaced domed front portion  120 ). A variety of different interchangeable versions of removable domed front portion  120  are illustrated and described herein. Removably coupled versions of domed front portion  120  may be referred to herein as “interchangeable patient interface inserts,” “interchangeable functional inserts,” “interchangeable inserts,” “removable inserts,” “inserts,” or the like. 
     As is described herein, in some embodiments, a domed front portion  120  may have a function or support some medical function or procedure, and thus a domed front portion  120  may be changed out to change functions or to facilitate performing a variety of medical functions. It is further appreciated that, in some embodiments, domed front portions  120  may be configured to operated with a person of a certain size (e.g., a child, an adolescent, a grown person, an obese person, etc.). For example, vent holes disposed in a domed front portion  120  may be configured for a predetermined breathing rate/gas flow for a person of a particular size. In some embodiments, a domed front portion  120  can thus be inserted into patient interface  110  based upon the size of a patient  101  being ventilated. 
       FIG. 2  is rear perspective of a patient interface  110  of a non-invasive ventilation system  100 , in accordance with various embodiments. Limbs  143  and  144  (not visible) have been swiveled to a forward position and hang downward toward the chest of patient  101 . As illustrated in  FIG. 2 , head strap system  111  defines a somewhat circular opening  211  (it maybe perfectly circular or may be somewhere between circular and oval in shape). It is appreciated that circular opening  211  may be devoid of material or may be covered by a fabric or other material. Moreover, circular opening  211  may be molded and/or may be defined by a plurality of slits made to open a region within head strap system  111 . In some embodiments, head strap system  111  is constructed from semi-rigid material with an o-frame feature, defined by the coupling of side straps  112 - 1  and  112 - 3  to the upper left and right lateral portions of frame  125 . This O-frame feature captures the top of the head while circular opening  211  cradles the occipital region of the rear skull of patient  101 . The semi-rigid construction of head strap system  111  provides some amount of inherent rigidity so that when it is in storage, it can be collapsed or folded; but when it&#39;s removed from collapsed storage, it easily and naturally returns to a general head shaped structure, so that it is visibly obvious how to position and install head strap system  111  on patient  101  when donning patient interface  110 . In this manner, there is no need to sort out where the front, back, top, or bottom is located. In one embodiment, patient interface  110  is packaged with head strap system  111  already pre-attached with frame  125 , so that when unpackaged the semi-rigid structure of head strap system  111  causes it to look somewhat like a helmet that can just be pulled quickly over the head and face area of patient  101 , much like putting on a catcher&#39;s mask. 
     Also depicted in  FIG. 2  is a quick release rip cord type pull-tab  212 . The positioning of the quick release pull tab  212  may be in different locations than illustrated and additional pull-tabs may be included in some embodiments. As illustrated, pull-tab  212  is located near the upper posterior skull and couples with head strap system  111 . Pull-tab  212  is easy to access and grasp by both a patient and by a medical care professional. Pull-tab  212  provides a grasping point which assists it doffing patient interface  110  in an expeditious fashion in case of emergency or claustrophobia of patient  101 . 
       FIG. 3  shows a front perspective view of patient interface  110  of a non-invasive ventilation system  160  and illustrates removal/insertion of an interchangeable patient interface insert  120 A, in accordance with an embodiment. As depicted, interchangeable patient interface insert  120 A is in the removed position. Interchangeable patient interface insert  120 A includes exhaust gas vent ports  123 , and is thus designed for use in a vented non-invasive ventilation application. Interchangeable patient interface insert  120 A includes one or more tabs  302  (one visible) which correspond with, and seat into, slots  303  that are disposed in the semi-elliptical rim  304  of frame  125 . Be applying a pinching pressure on grip regions  121 - 1  and  121 - 2  (as illustrated by arrows  301 ), interchangeable patient interface insert  120 A can be compressed slightly so that tabs  302  can be seated into slots  303  and interchangeable patient interface insert  120 A can be removably coupled with frame  125 . Reversal of the installation process allows for the removal of interchangeable patient interface insert  120 A. 
       FIG. 4  shows a front perspective view of patient interface  110  of a non-invasive ventilation system  100  and illustrates an interchangeable patient interface insert  120 B which includes a self-sealing access port  401 , in accordance with an embodiment. Self-sealing access port  401  may have one or more slits or openings through which a tube, such as tube  403  may be sealably inserted through interchangeable patient interface insert  120 B. As depicted in  FIG. 4 , self-sealing access port  401  comprises one or more slits  402 . In some embodiments, as depicted, slits  402  may intersect at right angles in the shape of a plus sign. Self-sealing access port  401  provides an opening through which a medical professional can perform procedures such as a bronchoscopy, as it gives access for a bronchoscope or other tubing or medical devices/instruments which may be inserted into the oral or nasal cavities of the patient. This allows for insertion of tubes/devices/instruments and performance of some medical procedures without removing patient interface  110 . Instead of doffing patient interface  110  to insert a tube or perform a procedure, interchangeable patient interface insert  120 B can be installed (if not already installed) and the procedure can be conducted/tubing inserted through interchangeable patient interface insert  120 B. This allows insertion of some tubing and performance of some medical procedures, which involve oral or nasal passages, while still performing noninvasive ventilation. For example, interchangeable patient interface insert  120 B allows for bronchoscopy to be performed on a sicker ventilated patient, which such a procedure could not otherwise be performed on, without removing the ventilation. Additionally, tube  403  or other device/instrument can be left in place within self-sealing access port  401 . In some embodiments, self-sealing access port  401  is sized, shaped, and configured such that it can couple with a nebulizer, metered dose inhaler, or other therapeutic device or drug delivery device, so that that flow from the attached device is directed towards a mouth and/or nose of patient  101 . 
       FIG. 5  shows a front perspective view of patient interface  110  of a non-invasive ventilation system  100  and illustrates an interchangeable patient interface insert  120 C which includes a breath sampling port  501 , in accordance with an embodiment. As illustrated, interchangeable patient interface insert  120 C does not include the exhaust gas vent ports that were included on interchangeable patient interface insert  120 A and interchangeable patient interface insert  120 B. In one embodiment, this can be because exhaust gas vent ports are disposed elsewhere in patient interface  110 . In another embodiment, this is because interchangeable patient interface insert  120 C is designed for use with non-vented non-invasive ventilation in which fresh respiratory gas for inhalation is supplied by one limb (e.g., limb  143 ) and exhaust gas (exhaled breath and unused respiratory gases) is expelled from patient interface and collected via another limb (e.g., limb  144 ). Interchangeable patient interface insert  120 C includes a breath sampling port  501  to which a breath sampling line  546  may be coupled in order to capture a sample of exhaled breath from within patient interface  110 . Breath sampling line  546  may then couple a captured exhaled breath sample to a carbon dioxide analyzer or other analyzer. 
     In one embodiment, a slight concavity is defined on the interior portion of interchangeable patient interface insert  120 C to form a breath scoop  502 . Breath scoop  502  is designed so that it is positioned in a region roughly centered on the upper lip of patient  101  so that it can briefly capture exhaled breath in a location where it can not be quickly washed away by a cross-flow between limbs  143  and  144 . In other embodiments, instead of being a simple concavity defined on the interior side of interchangeable patient interface insert  120 C, breath scoop  502  may be a separate structure, coupled in approximately the same location on the interior side of interchangeable patient interface insert  120 C. In embodiments which include breath scoop  502 , breath sampling port  501  sealably couples breath sampling line  546  with breath scoop  502 . Breath sampling line  546  operates to couple a captured exhaled breath sample to a carbon dioxide analyzer or other analyzer. Techniques for conducting breath sampling will be discussed further in a separate section herein. 
       FIG. 6  shows a front perspective view of patient interface  110  of a non-invasive ventilation system  100  and illustrates a self-sealing gastric tube insertion region  630  disposed within or coupled with facial skin interface  130 , in accordance with an embodiment. In  FIG. 6 , limbs  143  and  144  are shown swiveled downward such that that drape down toward the chest of patient  101 . This swiveling allows for the fresh respiratory gas to be provided from the front side of patient  101  instead of from the rear/overhead of patient  101 . This provides an option for patient comfort. 
     As depicted in  FIG. 6 , a gastric tube  647  has been inserted through a self-sealing an opening  632  defined in gastric tube insertion region  630 , near the left cheek of patient  101 . Gastric tube  647  may be a venting tube, feeding tube, or the like, and may be orogastric or nasogastric. A breath sampling tube or other tube may be inserted in a similar manner to that of tube  647 . In one embodiment, where facial skin interface  130  includes a plurality of flexible bladder sections or corrugations, insertion region  630  may be a gap between two of the flexible bladders or corrugations which provides an opening  632  for insertion of tube  647 . Herein, a corrugation is a series of convolutions that define peaks and valleys in the sealing material, and which can flexibly expand and contract by expanding and contracting the corrugations. Air pressure supplied, by ventilator  160  may inflate the bladders and cause them to seal about tube  647  inserted in a gap that exists between the bladders. The bladders then transfer the securing force (provided from head strap system  111  to frame  125 ) around the inserted tube  647  such that the tube is not driven into the facial skin of patient  101  to create a pressure point. In another embodiment, as depicted, patient interface  110 , includes an arched portion/bridge  631 , which provides a rigid or semi-rigid structure to shield tube  647  and opening  632  from the restraining forces which are normally transferred to facial skin interface  130  from head strap system  111 , and then from facial skin interface  130  to the facial skin of patient  101 . This prevents this restraining force from causing a pressure point by compressing tube  647  into the skin of patient  101 . In one embodiment, a cushioning material  633 , such as foam, silicone, or TPE surrounds opening  632  and provides a sealing function for self-sealing about tube  647  when inserted in opening  632 , sealing opening  632  when tube  647  is not inserted in opening  632 , and sealing to the facial skin of patient  101 . 
     In one embodiment, all or part of insertion region  630 , opening  632 , cushioning material  633 , and/or bridge  631  is/are configured to breakaway facial skin interface  130 . That is, one or more of these portions may be removably coupled with facial skin interface  130 . By constructing one or more of portions  631 ,  632 , and/or  633  such that they may be broken away from the rest of patient interface  110 , the remainder of patient interface  110  can be removed/doffed from patient  101  without removing tube  647  from patient  101  as would typically be required if tube  647  was inserted through some other opening in a conventional mask/patient interface. In a similar, when tube insertion region  630  is a gap between a pair of bladders or corrugations, tube  647  can be slipped from between the gap and can remain inserted in patient  101  while patient interface  110  is removed/doffed. 
       FIG. 7  shows a front perspective view of a doffed patient interface  110  of a non-invasive ventilation system  100 , in accordance with an embodiment, and also illustrates an interchangeable patient interface insert  120 D which includes built-in filter media  123 A, in accordance with an embodiment.  FIG. 7  illustrates the manner in which the semi-rigid structure of head strap system  111  retains the general shape of a helmet, even in a doffed configuration. 
     In one embodiment, filter media  123 A can be used in conjunction with or in place or exhaust gas vent ports  123  which have been depicted elsewhere herein. Typically, exhaust gas vent ports  123  are open to the atmosphere. This allows blowout of exhaled gases into the atmosphere, which may be undesirable or even dangerous to a care giver in some patient care circumstances. Instead of open vent holes, in one embodiment, filter media  123 A is included or alternatively utilized. Filter media  123 A provides a controlled pressure drop in addition to filtering contagions from exhaled gases as the exhaled gases pass through. In some embodiments, the filter media  123 A can simultaneously filter and vent, thus eliminating the need have separate vent holes. Media such as, but not limited to, filter cloth (e.g., cotton, polyester, or bamboo) or open cell foam may be utilized to form filter media  123 A. A variety of factors including one or more of composition, thickness, surface area, and porosity of the media of filter media  123 A can be selected, in some embodiments, to both filter contagions and provide a designated and intentional flow/leak rate to control internal pressure of patient interface  110 . In one embodiment, interchangeable patient interface insert  120 D can be removed and replaced with a new interchangeable patient interface insert  120 D when filter media  123 A becomes clogged, soiled, or has surpassed its recommended replacement interval. In another embodiment, filter media  123 A is, itself, replaceable. 
     In the enlarged view afforded by  FIG. 7 , a plurality of bladders  736  are visible which are disposed in compliant nose bridge seal  135 . Bladders  736  may be filled with air, gas, or liquid upon manufacture of patient interface  110 , in one embodiment. In another embodiment, fresh respiratory gas flow may be utilized (selectively in some embodiments), to inflate bladders  736 . Although not illustrated in  FIG. 7 , in some embodiments, such bladders are also disposed around selected portions or the entirety of the periphery of facial skin interface  130 . 
       FIG. 7  also illustrates, fasteners  726  ( 726 - 1 ,  726 - 2 ,  726 - 3 ,  726 - 4 ) to which side straps  112  ( 112 - 1 ,  112 - 2 ,  112 - 3 ,  112 - 4 ) may be buckled or otherwise fastened. In some embodiments, fasteners  726  are permanently coupled or removably coupled (i.e., snapped) into positioning tracks  727  ( 727 - 1 ,  727 - 2 ) along which the position of a fastener  726  may be adjusted. When snap type fasteners  726  are utilized, unsnapping one or more fasteners  726  provides a means for quick disconnect of side straps  112 , which allows patient interface  110  to quickly doffed. Slide adjustment allows for the positioning of fasteners  726  and helps adjust fasteners  726  to divert securing force way from compliant nose bridge seal  135  and the bridge of the nose of patient  101 . Additionally, positioning tracks  727  allow adjustment of the pitch and of patient interface  110  with respect to the face of patient  101 . 
     In some embodiments hook and or similar type of fastening may be utilized to secure a side strap  112  or other component. For example, regions  715  ( 715 - 1 ,  715 - 2 ,  715 - 3 ) illustrate regions where either hook material or loop material may be disposed such that it may be mated with its complimentary hook/loop component disposed on the end portion of a side strap  112  or on a positioning sleeve  748  associated with a tube or other component. When hook and loop type (or similar) fastening is utilized to secure ends of side straps  112 , a means for quickly doffing patient interface is provided by undoing the hook and loop fastening. 
     In some embodiments, a side strap  112  may change colors or change from opaque to somewhat translucent, transparent in response to a level of force induced stress on the strap which is indicative of a level of force or strap tightening that is considered to be so tight as to cause necrosis if not loosened. For example, an opaque side strap  112  of any color may stretch slightly and become translucent or transparent enough that a color change is noticeable in response to the stress of the side strap being stretched into an over tight state. Similarly, in some embodiments, an opaque side strap  112  of any color may stretch slightly and become translucent or transparent enough that that an embedded colored thread (e.g., a red thread) becomes visibly exposed in response to the stress of the side strap being stretched into an over tight state. An example of such an embedded colored thread  712  is shown  FIG. 7  as being visible on the rear (patient facing) side of side strap  112 - 4  at all times. In various embodiments, embedded thread  712  would only become visibly exposed on the opposite, non-patient facing side of side strap  712 - 4  in response to over tightening of side strap  112 - 4 . It is appreciated that some or all of side straps  112  may include such a color changing and/or embedded thread feature to indicate over tightened conditions. In some embodiments, embedded thread  712  may be embedded such that it is not visible at all, even on the non-patient facing side of a side strap  712 , until the side strap  712  becomes stretched into an over tightened state. 
     Orifices  722  ( 722 - 1 ,  722 - 2 ) are openings disposed, in one embodiment, in frame  125 . Limb  143  is illustrated as being sealably coupled with respiratory gas delivery orifice  722 - 1  which provides an entry port for fresh respiratory gas from ventilator  160 . Similarly, limb  144  is illustrated as being sealably coupled with respiratory gas delivery orifice  722 - 2  which provides a second entry port for fresh respiratory gas from ventilator  160  in a vented configuration. In a non-vented configuration, limb  143  or  144  may be used to transport exhaust gases away from patient interface  110 . In such a non-vented embodiment, orifice  722 - 2  may then comprise an exhaust gas orifice. 
       FIG. 8A  shows a front perspective view of a patient interface  110 A of a non-invasive ventilation system  100  configured with a zygomatic facial interface  831  and illustrating an interchangeable patient interface insert  120 E which includes an aviator style fresh respiratory gas interface  822 , in accordance with an embodiment. By aviator style, what is meant is that the flesh respiratory gases enter the patient interface at approximately a midline position on the front of the patient interface rather than from one or both lateral sides of the patient interface. 
     In  FIG. 8A , an alternative, aviator style, vented non-invasive ventilation breathing circuit  840  is illustrated. Breathing circuit  840 , in some embodiments, comprises respiratory gas supply tube  841 , swivel connector pieces  842 A and  842 B, limb  843 , anti-asphyxia valve  845 , and aviator style fresh respiratory gas interface  822 . Anti-asphyxia valve  845  operates in the same manner as the previously described anti-asphyxia valve  745 . Interchangeable patient interface insert  120 E is removable/replaceable by compressing grip regions  121 - 1  and  121 - 2  toward one another. In one embodiment, interchangeable patient interface insert  120 E, anti-asphyxia valve  845 , limb  843 , and swivel connector piece  843 A are coupled together and supplied as a single removable/replaceable unit. Limb  843  couples with respiratory gas supply tube  841  via a torque relieving swivel coupling provided by swivel connector pieces  842 A and  842 B which form an omni-directional swivel to relieve torque and prevent kinking and twisting of breathing circuit  840 . Respiratory gas supply tube  841  couples with ventilator  160  (not visible in  FIG. 8A ) in a similar manner as previously described, for respiratory gas tube  141 . In one embodiment, gas supply tube  841  may similarly utilize a “smart connection” to ventilator  160 . Ribs  848  configured into limb  843  and/or ribs  849  configured into gas supply line  841  provide for torque relief and flexibility, which facilitate patient comfort and ease of movement while patient interface  110 A is donned. In some embodiments, swivel portions  842 A and  842 B may be omitted and gas supply tube  841  and limb  843  may be a continuous piece of flexible tubing. 
     The zygomatic arch is a bony structure, but it also typically has a thicker layer of fatty tissue than the bridge of the nose, which is generally thin-skinned and has little in the way of cushioning. Because of the thin-skin on the bridge of the nose pressure points on the bridge of the nose quickly disrupt blood flow and create necrosis. Zygomatic facial interface  831  provides wing like extensions ( 831 - 1  and  831 - 2 ) of facial skin interface  130  which transfer securing forces of patient interface  110  to the zygomatic arch areas (cheek bones) of patient  101  and also spread the securing forces over a larger surface area of facial skin that other facial skin interfaces illustrated herein. By spreading securing forces to the zygomatic arch, over a larger facial skin surface area, and away from the bridge of the nose, zygomatic facial interface  831  further reduces the securing force (if any) which is transferred to nose bridge seal  135 . Zygomatic facial interface  831  spreads securing forces over a larger surface area of facial skin, and onto zygomatic arch structure. In one embodiment, either or both of facial skin interface  130  and zygomatic facial interface  831  may incorporate a plurality of structural features such as corrugations, ridges, or bladders  836 . One of the major differences between a corrugation/ridge and a bladder is internal, as a bladder may be adjustably filled with a gas or fluid, while a corrugation/ridge cannot. Even though designed to be inflatable filled, a bladder may still have a bumpy exterior appearance which makes it look similar to and in some respects function similar to a corrugation/ride. In one embodiment, bladders  836  are similar in structure and function to bladders  736  and provide cushioning and allow for some flexibility and movement of patient interface  110 A while still maintaining an intact facial seal with patient  101 . 
     In one embodiment, patient interface  110 A also includes an extended chin portion  832 . Oral-nasal masks are intended to capture both the mouth and nose. Extended chin portion  832  helps keep the patient&#39;s mouth closed in an oral mask or an oral-nasal mask. This can increase patient comfort. In one embodiment, extended chin portion  832  may include a bellows feature (not visible) that expands/contracts in response to movement of the chin of patient  101 . This allows patient  101  to slightly open his/her mouth or extend his/her chin without compromising the seal of patient interface  110 A and allowing respiratory gas to uncontrollably leak. 
     In  FIG. 8A , side straps such as  112 - 2  couple with fasteners such as fastener  826 . As depicted, fastener  826  is permanently or removably coupled into a track  827  along which it may be positioned. Slide-to-release mechanism  828  is utilized to lock fastener  826  in a desired position within track  827  or to unlock fastener  826  so that it may be slidably positioned in track  827 . It is noted that in  FIGS. 7 and 8 , strap positioning features are located near the face of patient  101  so that they are easily accessible for adjustment by patient  101  or by a care giver. 
     Although zygomatic facial interface  831 , extended chin portion  832 , slide-to release-mechanism  828 , and interchangeable patient interface insert  120 E are illustrated together in  FIG. 8A , these features may be utilized separately. For example, zygomatic facial interface  831  can be incorporated into patient interface  110  which is illustrated in  FIGS. 1-7 . Similarly, an aviator style fresh respiratory gas interface  822  may be utilized in patient interface  110 A which does not include zygomatic facial interface  831 . 
       FIG. 8B  is an aviator style patient interface similar to  FIG. 8A  in all regards (wherein like numerals refer to like components) except that an interchangeable patient interface insert  120 F with an aviator style fresh respiratory gas interface  822 B has replaced interchangeable patient interface insert  120 E and aviator style fresh respiratory gas interface  822 . As can be seen patient interface  120 F includes anti-asphyxia valve  845 B. As illustrated in  FIG. 8B , aviator style fresh respiratory gas interface  822  utilizes an alternative breathing circuit  840 B which comprises a ribbed respiratory gas supply tube  841  that connects directly gas interface  822 B without the use of an elbow, and which, in some embodiments, does not include a swivel connector piece. 
     Section 1 
     Adjusting a Ventilation Mask 
     Mask  110  includes a sealing portion (e.g., compliant nose bridge seal  135  and/or facial skin interface  130 ). In various embodiments, the sealing portion includes bladders, as described above. For example, compliant nose bridge seal  135  includes bladders  736  and facial skin interface  130  includes bladders  836 . In one embodiment, bladders  736  extend substantially along the entire length of compliant nose bridge seal  135 . Similarly, in another embodiment, bladders  836  extend substantially along the entire length of facial skin interface  130 . 
     In various embodiments, mask  110  is adjusted by fluidly adjusting the bladders (e.g., bladders  736  and  836 ). In particular, mask  110  is adjusted by inflating the bladders by gas, air, or liquid or any combination thereof. Also, mask  110  is adjusted by deflating the bladders. 
     In one embodiment, the bladders are fluidly connected to ventilator  160 . For example, each bladder is fluidly connected to ventilator  160  via a tube. The tube may be similar to line  546  or tube  647 . In such an embodiment, each bladder is fluidly separate from one another and each bladder is fluidly connected to ventilator  160 . 
     Alternatively, two or more bladders (e.g., adjacent bladders or non-adjacent bladders) may be fluidly connected to one another. As such, the fluidly connected bladders are fluidly separate from other bladders or other fluidly connected bladders. 
     In another embodiment, the bladders are fluidly connected to an inflation source. Such as, but not limited to, a pressure tank. 
     Mask  110  may be adjusted for a variety of reasons. For example, mask  110  may be adjusted in response to a detected unintentional leak. 
       FIG. 9  depicts an embodiment of a method  900  for adjusting a ventilation mask. 
     At  910  of method  900 , a ventilative state of mask  110  is measured. It is understood that mask  110  is placed over a nose and/or mouth of a patient, wherein a sealing portion of mask  110  is for establishing a fluid seal between mask  110  and the patient, and wherein the sealing portion comprises a plurality of bladders. 
     It is also understood that “ventilative state,” used herein, is any state of system  100  that is measurable and facilitates in determining whether or not there is an unintentional leak between mask  110  and patient  101 . For example, a ventilative state can be, but is not limited to, pressure, airflow, etc. 
     In one embodiment, at  912 , airflow is measured. In another embodiment, at  914 , pressure is measured. 
     In various examples, ventilative states (e.g., airflow, pressure) of non-invasive ventilation system  100  are measured. The ventilative states can be measured by ventilator  160  or other measuring devices. 
     The measuring can occur by obtaining information of ventilative states at various locations within system  100 . For example, ventilative states can be measured at mask  110 , at breathing circuit  140  and/or ventilator  160 . 
     At  920 , an unintentional leak of the fluid seal is determined based on a measured change of the ventilative state. For example, if the measured pressure and/or airflow in system  100  falls outside of a prescribed or expected range, then it is determined that there is an unintentional leak of the fluid seal. An unintentional leak between mask  110  and patient  101  may occur due to a variety of reasons (e.g., patient may accidentally bump mask  110 , patient  101  may move mask  110 , etc.). As a result, a ventilative state of system  100  may change. 
     At  930 , a bladder is adjusted to seal the unintentional leak. For example, at least one bladder (e.g., at least one of bladders  736  or  836 ) is adjusted. In particular, if there is a gap (e.g., unintentional leak) between a bladder and patient  101 , then the bladder can be adjusted (e.g., inflated) to seal the gap. 
     In one embodiment, at  931 , a bladder is automatically adjusted to seal the unintentional leak. For instance, in response to measured change in the ventilative state (e.g., lower pressure) which is indicative of an unintentional leak between mask  110  and patient  101 , a bladder is automatically inflated (e.g., by ventilator  160 ) to facilitate in sealing the unintentional leak. Alternatively, a bladder is manually adjusted. 
     In another embodiment, at  932 , bladders are sequentially adjusted. For example, in response to a measured change in the ventilative state outside an expected or prescribed range, a first bladder is inflated. If the ventilative state still remains outside and expected or prescribed range, another bladder is inflated, such as an adjacent bladder to the first bladder, and so on, until the ventilate state returns to the expected range and thus the unintentional leak is sealed. Alternatively, a bladder inflated subsequent the first inflated bladder, is not adjacent to the first bladder. 
     In a further embodiment, at  933 , bladders are automatically adjusted according to a pre-defined pattern. For example, the inflation of bladders can initiate at an arbitrary first bladder and continue clockwise or counterclockwise from the first bladder, until the unintentional leak is sealed. In another example, a first bladder, located at a position with a highest probability of unintentional leakage, is initially automatically adjusted. A second bladder, located at a position with a second highest probability of unintentional leakage, is subsequently adjusted, and so on, until the unintentional leak is sealed. 
     In another embodiment, at  934 , a bladder is adjusted such that a measured ventilative state returns to a prescribed ventilative state. For example, in response to a ventilative state falling out of a prescribed or expected range, a bladder is adjusted to stop the unintentional leak. As a result of adjusting the bladder, the ventilative state returns to a prescribed ventilative state in a prescribed ventilative state range which is indicative of a proper seal between mask  110  and patient  101 . 
     In one embodiment, at  935 , more than one bladder is simultaneously adjusted. For example, all of the bladders disposed in compliant nose bridge seal  135  are simultaneously adjusted. In another embodiment, all of the bladders disposed on pressure points of patient  101  are simultaneously adjusted. 
     Moreover, mask  110  may be adjusted to decrease necrosis. 
       FIG. 10  depicts an embodiment of a method  1000  for adjusting a ventilation mask to decrease necrosis. 
     At  1010  of method  1000 , mask  110  is fluidly sealed to a patient  101 , wherein the mask comprises a plurality of bladders (e.g., bladders  736  and  836 ) in physical contact with the patient. 
     At  1020 , a bladder is adjusted to decrease necrosis. For example, a bladder(s) is adjusted to decrease pressure at a pressure point. It should be appreciated that a bladder(s) can be adjusted to decrease necrosis similarly to bladders being adjusted as described in method  900 . 
     In one embodiment, at  1022 , a bladder is adjusted (e.g., deflated) to decrease pressure on a pressure point of the patient. 
     In another embodiment, at  1024 , inflate a bladder of the plurality of bladders to decrease necrosis. For example, bladders surrounding a pressure point are inflated to decrease necrosis. 
     In a further embodiment, at  1026 , a bladder is deflated to decrease necrosis. For example, a bladder disposed on a pressure point is deflated to decrease necrosis. 
     In one embodiment, at  1028 , a bladder(s) is automatically adjusted to decrease necrosis. For example, after a predetermined amount of time, a bladder(s) located on or about a pressure point are automatically adjusted to decrease necrosis. 
     Section 2 
     Corrugated Flexible Seal of a Ventilation Mask 
     Mask  110  includes a sealing portion (e.g., compliant nose bridge seal  135  and/or facial skin interface  130 ). In various embodiments, the sealing portion is a corrugated flexible seal. For example, the sealing portion includes bladders  736  and  836  (also referred to as corrugations or ridges). The ridges are disposed along the corrugated flexible seal and configured for physical contact with patient  101 . 
     In general, the corrugated flexible seal (in particular, the ridges of the corrugated flexible seal) allows for some flexibility and movement of patient interface  110  while still maintaining an intact facial seal with patient  101 . 
     In one embodiment, corrugated flexible seal is configured to establish a fluid seal over the nose of patient  101 . For example, a fluid seal occurs between ridges  736  of compliant nose bridge seal  135  and the nose bridge of patient  101  (see  FIG. 7 ). With respect to ridges  736 , their length, depth, and width (frequency) may vary in some portions of the compliant nose bridge. 
     In another embodiment, the corrugated flexible seal is configured to establish a fluid seal around the nose and/or mouth of patient  101 . For example, a fluid seal occurs around the nose and/or mouth of patient  101  by ridges  736  of compliant nose bridge seal  135  and ridges  836  of facial skin interface  130 . 
     Corrugated flexible seal (in particular, ridges  736  and/or ridges  836 ) is configured to move or flex in a plurality of axes and/or directions. This allows for flexibility and movement of patient interface  110  while still maintaining an intact facial seal. 
     Ridges  736 , as depicted in  FIG. 7 , extend along the width of compliant nose bridge seal  135 . In other words, the length of each ridge extends in a direction from the tip of the nose towards the eyes of patient  101 . Moreover, ridges  736  are disposed along the length of nose bridge seal  135 . 
     Rides  836 , as depicted in  FIG. 8 , extend along the width of facial skin interface  130 . Moreover, ridges  836  are disposed along the length of facial skin interface  130  (and zygomatic facial interface  831 ). With respect to ridges  836 , their length, depth, and width (frequency) may vary in some portions of facial skin interface  130  and or zygomatic facial skin interface  831 . Also, in some embodiments, the length of ridges  736  is longer than the length of ridges  836 . 
     In various embodiments, the ridges of the corrugated flexible seal have different shapes. For example, ridges  836  can have different shapes from one another and/or have different shapes than ridges  736 . Elsewhere herein, microgrooves are described. It should be appreciated that ridges and valleys of corrugations are much larger in depth and width than microgrooves. For example, in some embodiments corrugations are at least an order of magnitude larger than microgrooves. It is appreciated that one or more microgrooves may be configured into a corrugation, in some embodiments. 
     Section 3 
     Nasal Passage Opener of a Ventilation Mask 
     In various embodiments, mask  110  includes a nasal passage opener. The nasal passage opener is configured for facilitating in opening of a nasal passage (or nasal valve). The nasal passage opener is disposed over a nasal passage (or nasal valve) of patient  101  when mask  110  is sealed on the face of patient  101 . Opening up the nasal passages (valves) can assist in decreasing the rate of breathing and/or patient effort in breathing. 
     In one embodiment, the nasal passage opener is compliant nose bridge seal  135 . For example, when compliant nose bridge seal  135  is placed over the nasal passage, the shape of compliant nose bridge seal  135  assists in opening the nasal passage, such as with an outward springing force which pulls open the nasal passages. As a result, the nasal passage is assisted in opening. 
     In another embodiment, patient interface  110  interacts with and slightly laterally stretches the cheek skin of patient  101 , where the cheek skin is the skin starting at the lateral edges of the nose and extending laterally as far as the skin above the zygomatic arches. This lateral stretching of the cheek skin pulls the nasal passages slightly laterally to a more open state. With reference to FIGS.  1  and  3 - 7 , in some embodiments, the positioning of side straps  112 - 1  and  112 - 3  assists in providing lateral pressure to facial skin interface  130  to effect the lateral stretching of the cheek skin. With reference to  FIG. 8A , zygomatic facial interface portions  831 - 1  and  831 - 2  and the positioning of side straps  112 - 1  and  112 - 3 , in some embodiments, act in concert to slightly laterally stretch the cheek skin of patient  101 . It should be appreciated that this cheek skin stretching operates in a similar fashion to the Cottle test, which is used to evaluate nasal valve stenosis. As a result of bilateral facial skin stretching the nasal passage is assisted in opening. 
     In another embodiment, the nasal passage opener is a fluidly adjustable bladder or bladders (e.g., bladders  736 ), as described in Section 1. For example, bladders  736  are inflated at the nasal passage. The inflation provides force onto portions of the nasal passage, which may pull the nasal passage into a more open state, such as by adhesively pulling the nasal passages open in certain regions and/or laterally stretching cheek skin of a patient. As a result, the nasal passage is assisted in opening. 
     In some embodiments, one or more of facial cheek skin stretching may be utilized, a compliant nose bridge seal, and inflatable bladders may be used in combination for opening the nasal passages of patient  101 . 
     In one embodiment, the nasal passage opener is integrated with mask  110 . Alternatively, the nasal passage opener is removable from mask  110 . 
       FIG. 11  depicts an embodiment of a method for assisting in opening a nasal passage. 
     At  1110 , a ventilation mask is sealed over a face of a patient, wherein the ventilation mask is disposed over a nasal passage. For example, mask  110  is sealed over the face of patient  101 , wherein mask  110  is disposed over a nasal passage. 
     At  1120 , nasal passage is assisted in opening by the ventilation mask disposed over the nasal passage. For example, the nasal passage is assisted in opening by compliant nose bridge seal disposed over the nasal passage and/or by lateral cheek skin stretching provided by mask  110 . 
     In one embodiment, at  1122 , a cross-sectional area of a nasal passage is increased. For example, the cross-sectional area of the nasal passage is increased because of the nasal passage opener. 
     In another embodiment, at  1124 , a bladder is adjusted to assist in opening of the nasal passage. For example, a single bladder is inflated to urge in the opening of a nasal passage. 
     In a further embodiment, at  1126 , a plurality of bladders is adjusted to assist in opening of the nasal passage. For example, a plurality of bladders (e.g., bladders  736 ) are inflated, such that it urges open the nasal passage. As a result, the cross-sectional area of the nasal passage is increased. 
     Section 4 
     A Carbon-Dioxide Sampling Device for Noninvasively Measuring Carbon Dioxide in Exhaled Breath 
     With reference now to  FIG. 12 , in accordance with an embodiment, a front perspective view  1200  is shown of a non-invasive ventilation patient interface  110 , which is also referred to herein as a mask  110 , with carbon-dioxide sampling device  1201  for non-invasively measuring carbon dioxide in exhaled breath. Patient interface  110  includes a carbon-dioxide sampling device  1201 , straps  112 - 1 ,  112 - 2  and  112 - 3 , an inhalation gas supply line  144 , which is also referred to herein as limb  144  of the breathing circuit  140 , and an exhalation gas collection line  143 , which is also referred to herein as limb  143  of the breathing circuit  140 . The inhalation gas supply line may be identified with limb  144  of the breathing circuit  140 , as previously described; and, the exhalation gas collection line may be identified with limb  143  of the breathing circuit  140 , as previously described; however, these identifications of the inhalation gas supply line and the exhalation gas collection line are by way of example, without limitation thereto, as other implementations of the inhalation gas supply line and the exhalation gas collection line are within the spirit and scope of embodiments described herein. In addition, patient interface  110  may also include a y-piece  142 , as previously described, which functions as a gas-line coupling. 
     With further reference to  FIG. 12 , in accordance with an embodiment, the carbon-dioxide sampling device  1201  is configured to non-invasively measure carbon dioxide in exhaled breath. The carbon-dioxide sampling device  1201  includes a breath-sampling chamber  1210 , and a carbon-dioxide collector  502 , which is also referred to herein as breath scoop  502 . The carbon-dioxide collector  502  may be identified with the breath scoop  502 , as previously described; however, this identification of the carbon-dioxide collector  502  is by way of example, without limitation thereto, as other implementations of the carbon-dioxide collector  502  are within the spirit and scope of embodiments described herein. The breath-sampling chamber  1210  is configured to be disposed over a patient&#39;s mouth and/or nose, and configured to seal with a patient&#39;s face preventing unintentional leakage of respiratory gases from the breath-sampling chamber  1210 . By way of example without limitation thereto, the breath sampling chamber  1210  includes a frame  125 , a facial skin interface  130 , a compliant nose bridge seal  135 , and an interchangeable patient interface insert  120 C, which have been previously described. The carbon-dioxide collector  502  is disposed in the breath-sampling chamber  1210 . The carbon-dioxide collector  502  is configured to be disposed in proximity to, and outside of, the nose and/or mouth of the patient  101 , and to collect a sample of exhaled breath from the patient  101 . The straps  112 - 1 ,  112 - 2  and  112 - 3  are configured to hold the breath-sampling chamber  1210  in place over the patient&#39;s mouth and/or nose, and to apply tension to make a seal with a patient&#39;s face preventing unintentional leakage of respiratory gases from the breath-sampling chamber  1210 . The inhalation gas supply line  144  is coupled with the breath-sampling chamber  1210 , and is configured to transport oxygen gas to the patient  101 . The exhalation gas collection line  143  is coupled with the breath-sampling chamber  1210 , and is configured to remove exhaled gases from the breath-sampling chamber  1210 . 
     With further reference to  FIG. 12 , in accordance with an embodiment, patient interface  110  also includes an interchangeable insert  120 C that is disposed at a front of the breath-sampling chamber  1210 . The carbon-dioxide sampling device  1201  also includes a breath-sampling line  546 , as previously described. Thus, patient interface  110  also includes a breath-sampling line  546  configured to transport a sample of the exhaled breath from the patient  101  collected by the carbon-dioxide collector  502 . The interchangeable insert  120 C includes a breath-sampling port  501  that is configured to couple the breath-sampling line  546  with the carbon-dioxide collector  502 . The breath-sampling line  546  is configured to transport a sample of exhaled breath from the patient  101  collected by the carbon-dioxide collector  502 . A portion of the breath-sampling line  546  proximate to the breath-sampling chamber  1210  is securely attached to the breath-sampling chamber  1210 , and is configured to prevent accidental interference by the patient  101  with the breath-sampling line  546 . By way of example, the breath-sampling chamber  1210  may be configured as a respiration chamber of a breathing mask  110 , without limitation thereto. 
     With further reference to  FIG. 12 , in accordance with an embodiment, the carbon-dioxide sampling device  1201  may also include a carbon-dioxide indicator  1220  that is configured to indicate when a threshold level of carbon dioxide is exceeded in the exhaled breath from the patient  101 . Thus, patient interface  110  includes the carbon-dioxide indicator  1220  that is configured to indicate when a threshold level of carbon dioxide is exceeded in the exhaled breath from the patient  101 . The carbon-dioxide indicator  1220  includes a visible portion that is configured to change an appearance of the visible portion when a threshold level of carbon dioxide is exceeded in the exhaled breath from the patient  101 . The carbon-dioxide indicator  1220  may also include a visible portion that is configured to change color when a threshold level of carbon dioxide is exceeded in the exhaled breath from the patient  101 . The carbon-dioxide indicator  1220  may be mounted conspicuously on a portion of the carbon-dioxide sampling device  1201  to be readily observable by an attendant of the patient  101 . 
     With reference now to  FIG. 13 , in accordance with an embodiment, a cross-sectional view  1300  is shown of patient interface  110  taken along line  13 - 13  of  FIG. 12 .  FIG. 13  illustrates the carbon-dioxide sampling device  1201  including the breath-sampling chamber  1210 , and a carbon-dioxide collector  502 . As shown in  FIG. 13 , component parts of the breath-sampling chamber  1210  are also shown in cross-section, for example, frame  125 , facial skin interface  130 , compliant nose bridge seal  135 , and interchangeable patient interface insert  120 C, covering the patient&#39;s mouth and/or nose. Thus, the breath-sampling chamber  1210  is configured to be disposed over a patient&#39;s mouth and nose, as shown. In other embodiments, a similar breath-sampling chamber may be disposed over only the nose or only the mouth of a patient. The breath-sampling chamber  1210  is also configured to seal with a patient&#39;s face preventing unintentional leakage of respiratory gases from the breath-sampling chamber  1210 . The carbon-dioxide collector  502  is disposed in the breath-sampling chamber  1210 , and is fluid dynamically isolated from flow of fresh respiratory gases such that exhaled breath may be captured therein and directed toward breath-sampling line  546 . The carbon-dioxide collector  502  is configured to be disposed in proximity to, and outside of, a respiratory opening (nose, mouth, or nose and mouth) of the patient  101 , and to collect a sample of exhaled breath from the patient  101 . As shown in  FIG. 13 , the carbon-dioxide collector  502  includes an upper portion  502 - 1  of the breath scoop  502 , a lower portion  502 - 2  of the breath scoop  502 , and a breath-scoop channel  502 - 3 . The upper portion  502 - 1  of the breath scoop  502  and the lower portion  502 - 2  of the breath scoop  502  are designed to capture the patient&#39;s breath either from the nose or the mouth of the patient  101 , is indicated by the respective arrows in  FIG. 13  directed from the patient&#39;s nose and mouth, with substantially no dilution with respiratory gases supplied to the patient  101 . The breath-sampling line  546  is also shown in  FIG. 13 ; unlike other elements of the figure, the breath-sampling line  546  is not shown in cross-section, but rather, lies generally outside of the plane of the figure, for the purpose of facilitating the description. The carbon-dioxide collector  502  communicates with the breath-sampling line  546  through the breath-sampling port  501 . Thus, the carbon-dioxide collector  502  is configured to collect a sample of the exhaled breath from the patient  101  that is substantially undiluted by respiratory gases supplied for the patient&#39;s breathing. 
     With further reference to  FIG. 13 , in accordance with an embodiment, the carbon-dioxide sampling device  1201  may further include a carbon-dioxide sensor (not shown) that is configured to sense a level of carbon dioxide in the exhaled breath of the patient  101 , and to output a carbon-dioxide sensor signal commensurate with the level of carbon dioxide. In one embodiment, the carbon-dioxide sensor may be co-located with the carbon-dioxide collector  502 , so that a sensor signal commensurate with the content of carbon dioxide in the breath of the patient  101  may be obtained as close as possible to the source of exhaled breath, yet non-invasively. Thus, the carbon-dioxide collector  502  may include the carbon-dioxide sensor. 
     With reference now to  FIGS. 14 and 15 , in accordance with alternative embodiments, a schematic diagram  1400  is shown of a carbon-dioxide analyzer  1401  of one embodiment in  FIG. 14 ; and, a schematic diagram  1500  is shown of a carbon-dioxide analyzer  1401  of an alternative embodiment in  FIG. 15 . The carbon-dioxide sampling device  1201  may also include the carbon-dioxide analyzer  1401  of either embodiment. As shown in  FIG. 14 , the carbon-dioxide analyzer  1401  is configured to determine, from a sample of exhaled breath from the patient  101 , a measurement of carbon-dioxide content in the sample of exhaled breath from the patient  101 . As shown in the alternative embodiment of  FIG. 15 , for example, for a carbon-dioxide sensor that may be co-located with the carbon-dioxide collector  502 , the carbon-dioxide analyzer  1401  is configured to convert a sensor signal received from the carbon-dioxide sensor into a measurement of carbon dioxide content in the sample of exhaled breath from the patient  101 . The carbon dioxide analyzer  1401  also includes a carbon-dioxide analysis protocol executor  1402  to provide an accurate measurement of carbon dioxide content in the sample of the exhaled breath from the patient  101  that is substantially unaffected by dilution from respiratory gases supplied for the patient&#39;s breathing. Both the carbon-dioxide analyzer  1401  and the carbon-dioxide analysis protocol executor  1402  may include: hardware, firmware, hardware and software, firmware and software, hardware and firmware, and hardware and firmware and software, any of which are configured to assist in the analysis of the sample of exhaled breath from the patient  101  to obtain a measurement of carbon dioxide content that is substantially undiluted by respiratory gases supplied for the patient&#39;s breathing. Moreover, the carbon-dioxide analyzer  1401  and the carbon-dioxide analysis protocol executor  1402  may be configured as separate electronic devices that are separate from any ventilator  160  used to ventilate a patient  101  with respiratory gases. The carbon-dioxide analyzer  1401  and the carbon-dioxide analysis protocol executor  1402  may include, by way of example without limitation thereto, a computer system. 
     With reference now to  FIG. 16 , in accordance with an embodiment, a flowchart  1600  is shown of a method for non-invasively measuring carbon dioxide in exhaled breath of a patient. The method includes the following operations. At  1610 , a carbon-dioxide collector is disposed in proximity to, and outside of, the nose and mouth of the patient. At  1620 , a sample of exhaled breath is collected from the patient. The sample of the exhaled breath from the patient is substantially undiluted by respiratory gases supplied for the patient&#39;s breathing, for example, as described above, by means of the breath scoop  520 . The method may further include the following operations. At  1630 , a level of carbon dioxide in the exhaled breath of the patient is sensed with a carbon-dioxide sensor. At  1640 , a sensor signal is output that is commensurate with the level of carbon dioxide. At  1650 , the sensor signal is converted into a measurement of carbon dioxide content in the sample of exhaled breath from the patient with the carbon-dioxide analyzer. In addition, at  1660 , a carbon-dioxide analysis protocol may be applied to provide an accurate measurement of carbon dioxide content in the sample of the exhaled breath from the patient that is substantially unaffected by dilution from respiratory gases supplied for the patient&#39;s breathing. 
     Section 5 
     A Carbon-Dioxide Sampling System for Accurately Monitoring Carbon Dioxide in Exhaled Breath 
     With reference now to  FIG. 17 , in accordance with an embodiment, a schematic diagram  1700  is shown of a carbon-dioxide sampling system  1701  for accurately monitoring carbon dioxide in exhaled breath. Herein, “accurately” refers to measuring carbon dioxide levels closely to their actual (true) values. The carbon-dioxide sampling system  1701  includes a ventilator  160 . The ventilator  160  is configured to ventilate a patient  101  with respiratory gases. The ventilator  160  includes a carbon-dioxide sampling control unit  160 - 1 , and a carbon-dioxide analyzer  1401 . Although similar to the carbon-dioxide analyzer  1401  described above, in contrast with the carbon-dioxide analyzer  1401  described above, the carbon-dioxide analyzer  1401  is configured as an integral part of the ventilator  160 , and therefore, is also configured as an integral part of the carbon-dioxide sampling system  1701 . The carbon-dioxide sampling control unit  160 - 1  is configured to control the timing of sampling of carbon dioxide in the exhaled breath of a patient  101 , and to control the timing of an analysis of exhaled gases by the carbon-dioxide analyzer  1401 . The carbon-dioxide sampling control unit  160 - 1  may include: hardware, firmware, hardware and software, firmware and software, hardware and firmware, and hardware and firmware and software, any of which are configured to assist in the sampling of the sample of exhaled breath from the patient  101  to obtain a measurement of carbon dioxide content that is substantially undiluted by respiratory gases supplied, for the patient&#39;s breathing. Thus, the carbon-dioxide sampling control unit  160 - 1  is configured to control collection of a sample of exhaled breath from the patient  101  that is substantially undiluted by respiratory gases supplied for the patient&#39;s breathing. 
     With further reference to  FIG. 17 , in accordance with an embodiment, the ventilator  160  further includes a ventilation timing unit  160 - 2 . The ventilation timing unit  160 - 2  may include: hardware, firmware, hardware and software, firmware and software, hardware and firmware, and hardware and firmware and software, any of which are configured to assist in ventilating a patient  101  at regular intervals based on measured levels of carbon dioxide in the breath of the patient  101 . The carbon-dioxide analyzer  1401  is configured to regulate the ventilation timing unit  160 - 2  to ventilate a patient  101  at regular intervals based on measured levels of carbon dioxide in the breath of the patient  101 . The carbon dioxide analyzer  1401  may also include an analysis protocol executor  1402  to provide an accurate measurement of carbon dioxide content in the sample of the exhaled breath from the patient  101  that is substantially unaffected by dilution from respiratory gases supplied for the patient&#39;s breathing, as previously described. 
     With further reference to  FIG. 17 , in accordance with an embodiment, the carbon-dioxide sampling system  1701  may also include a breath-sampling chamber  1210 . As previously described, the breath-sampling chamber  1210  is configured to be disposed over a respiratory opening of a patient (nose, mouth, or nose and mouth), and is configured to seal with a patient&#39;s face preventing unintentional leakage of respiratory gases from the chamber. Moreover, the breath-sampling chamber  1210  is configured to be coupled to the ventilator  160 , as an integral part of the carbon-dioxide sampling system  1701 . The carbon-dioxide sampling system  1701  may further include a carbon-dioxide collector  502 , as previously described, which is disposed in the breath-sampling chamber  1210 . The carbon-dioxide sampling system  1701  may further include an exhalation-gas collection line  143 , as previously described, coupled to the breath-sampling chamber  1210  configured to collect exhaled gases in a breath exhaled by the patient  101 , and to transport the exhaled gases to the carbon-dioxide analyzer  1401 . 
     With reference now to  FIG. 18 , in accordance with an embodiment, a front perspective view  1800  is shown of patient interface  110  of a combined non-invasive ventilation patient interface  110  and carbon-dioxide sampling system  1701 . The combined interface  110  and system  1701  includes patient interface  110 , and a carbon-dioxide sampling system  1701 , as described above in the discussions of  FIGS. 9 and 14 , respectively. The breath-sampling chamber  1210  includes a respiration chamber of a breathing mask  110 . The combined patient interface  110  and carbon-dioxide sampling system  1701  may further include a separate breath-sampling line  546  that is configured to transport a sample of the exhaled breath from the patient  101  to the carbon-dioxide analyzer  1401 . The combined patient interface  110  and carbon-dioxide sampling system  1701  may also include an inhalation gas supply line  144  and an exhalation gas collection line  143 . The inhalation gas supply line  144  is coupled with the breath-sampling chamber  1210 , and is configured to transport oxygen gas to the patient  101 . The exhalation gas collection line  143  is coupled with the breath-sampling chamber  1210 , and is configured to remove exhaled gases from the breath-sampling chamber  1210 . In an alternative embodiment, the exhalation gas collection line  143  may be configured to transport a sample of the exhaled breath from the patient  101  to the carbon-dioxide analyzer  1401 , instead of the separate breath-sampling line  546 . The exhalation-gas collection line  143  is securely attached, to the breath-sampling chamber  1210 , and is configured to prevent accidental interference by the patient  101  with the exhalation-gas collection line  143 . The combined patient interface  110  and carbon-dioxide sampling system  1701  may also include a carbon-dioxide indicator  1220 , as previously described in the discussion of  FIG. 12 . The carbon-dioxide indicator  1220  is configured to indicate when a threshold level of carbon dioxide is exceeded in the exhaled breath from the patient  101 . The carbon-dioxide indicator  1220  is mounted conspicuously on a portion of the mask  110  to be readily observable by an attendant of the patient  101 . 
     With reference now to  FIG. 19 , in accordance with an embodiment, a schematic diagram  1900  is shown of the carbon-dioxide analyzer  1401 . The carbon-dioxide analyzer  1401  may further include a carbon-dioxide sensor  1901 . The carbon-dioxide sensor  1901  is configured to sense a level of carbon dioxide in the exhaled breath of the patient  101 , and to output a sensor signal commensurate with the level of carbon dioxide. The carbon dioxide analyzer  1401  may also include a sensor-signal converter  1902 . The sensor-signal converter  1902  may include: hardware, firmware, hardware and software, firmware and software, hardware and firmware, and hardware and firmware and software, any of which are configured to convert the sensor signal into a measurement of carbon dioxide content in the sample of the exhaled breath from the patient  101 . Thus, the sensor-signal converter  1902  is configured to convert the sensor signal into a measurement of carbon dioxide content in the sample of the exhaled breath from the patient  101 . The carbon-dioxide analyzer  1401  may further include an analysis protocol executor  1402 . The analysis protocol executor  1402  is configured to provide an accurate measurement of carbon dioxide content in the sample of the exhaled breath from the patient  101  that is substantially unaffected by dilution from respiratory gases supplied for the patient&#39;s breathing, as previously described. The carbon-dioxide sensor  1901  may include an infra-red detector  1901 - 1 , and a source of infra-red radiation  1901 - 2 . The infra-red detector  1901 - 1 , by way of example, without limitation thereto, may be a semiconductor photo-diode. The infra-red detector  1901 - 1  is configured to measure the absorbance of infra-red radiation at a frequency within an absorption band of carbon dioxide for the infra-red radiation, and to generate a sensor signal commensurate with the level of carbon dioxide based on absorbance. 
     With reference now to  FIG. 20 , in accordance with an embodiment, a schematic diagram  2000  is shown of a combination  2001  of a carbon-dioxide measurement display  2001 - 2  and a carbon-dioxide measurement recorder  2001 - 1 . The carbon-dioxide measurement recorder  2001 - 1  may be a computer system and/or the memory of a computer system, without limitation thereto. As shown in  FIG. 20 , the carbon-dioxide measurement display  2001 - 2  may be configured to display data from the ventilator  160 , for example, such as: respiration rate, indicated by the sinusoidal waveform on the carbon-dioxide measurement display  2001 - 2 ; the activity of the ventilator  160  in supplying respiratory gases, for example, oxygen, to the patient  101 , indicated by the square-wave waveform; and, a textual display of the partial pressure of carbon dioxide in exhaled breath, P E CO 2 . As shown in  FIG. 20 , the partial pressure of carbon dioxide in exhaled breath may be displayed as a decimal number in units of pressure, given in units of millimeters of mercury (mm Hg), without limitation thereto. 
     With reference now to  FIG. 21 , in accordance with an embodiment, a flowchart  2100  is shown of a method for accurately monitoring carbon dioxide in exhaled breath of a patient. The method includes the following operations. At  2110 , a sampling of carbon dioxide in an exhaled breath of a patient is timed with a carbon-dioxide sampling control unit. 
     At  2120 , the timing of an analysis of gases in an exhaled breath of a patient is controlled with a carbon-dioxide analyzer. The carbon-dioxide sampling control unit is configured to control collection of a sample of the exhaled breath from the patient that is substantially undiluted by respiratory gases supplied for the patient&#39;s breathing. Therefore, the collection of the exhaled breath sample may be timed not to coincide with a time when respiratory gases, for example, oxygen, are being supplied to the patient. The method may also include the following operation. At  2130 , a ventilation timing unit is regulated to ventilate a patient at regular intervals based on measured levels of carbon dioxide in the breath of the patient. In addition, at  2140 , a carbon-dioxide analysis protocol may be applied to provide an accurate measurement of carbon dioxide content in the sample of the exhaled breath from the patient that is substantially unaffected by dilution from respiratory gases supplied for the patient&#39;s breathing. 
     Section 6 
     Interchangeable Inserts 
     Various embodiments provide a ventilation mask with a removable insert. In one embodiment, the front portion of the mask is removable to enable access to a respiratory opening region such as either the mouth, nose region, or both the mouth and nose regions of a patient without requiring removal of the entire mask and strap system. The nose region would comprise at least the nasal (nose) opening and may further comprise one to several centimeters surrounding the nasal opening. The mouth region would comprise at least the oral (mouth) opening and may further comprise one to several centimeters surrounding the oral opening. This enables quick access to the mouth and/or nose region while simultaneously ventilating the patient. 
     The removable insert enables a caregiver access to the mouth and/nose region of the patient that would be inaccessible with a conventional ventilation mask on the patient. With a conventional mask, the entire mask and strapping system would need to be removed to gain access to the nose and/or mouth region of the patient. Thus, the removable insert of saves considerable time because mask adjustment is significantly reduced, especially when access to the mouth and/or nose region of the patient is desired. 
     The removable insert enables the patient to perform many tasks while being simultaneously ventilated. For example, a patient can eat, take medication, brush teeth, talk, etc., with the insert removed. It should be appreciated that the patient is still ventilated even with the removable section of the mask removed from the frame portion. 
     Referring back to  FIG. 1 , domed front portion  120  is removable from frame portion  125  to enable access to the mouth and/or nose region of the patient without requiring removal of the frame portion  125  from the patient. In this embodiment, the mouth and/or nose region of the patient can be accessed without removing or adjusting strapping system  111 . 
     Referring back to  FIG. 3 , a front perspective view of patient interface  110  of a non-invasive ventilation system  160  is shown and illustrates removal/insertion of an interchangeable patient interface insert  120 A, in accordance with an embodiment. As depicted, interchangeable patient interface insert  120 A is in the removed position to enable access to the nose and/or mouth region of the patient. Interchangeable patient interface insert  120 A includes exhaust gas vent ports  123 , and is thus designed for use in a vented non-invasive ventilation application. Interchangeable patient interface insert  120 A includes one or more tabs  302  (one visible) which correspond with, and seat into, slots  303  that are disposed in the semi-elliptical rim  304  of frame  125 . Be applying a pinching pressure on grip regions  121 - 1  and  121 - 2  (as illustrated by arrows  301 ), interchangeable patient interface insert  120 A can be compressed slightly so that tabs  302  can be seated into slots  303  and interchangeable patient interface insert  120 A can be removably coupled with frame  125 . Reversal of the installation process allows for the removal of interchangeable patient interface insert  120 A. 
     It is appreciated that when the removable insert  120 A is in the removed position, the patient is still receiving gas flow from limb  143  because the airflow enters the frame portion  125  of the mask. The removable insert enables simultaneous ventilation and access to the mouth and/or nose region of the patient. 
     In one embodiment, the removable insert includes a graphic or color on the outside surface (facing away from the patient) so the patient can have a customized look. For example, a portion of the removable insert may be opaque or a color such as orange, red, or blue (or configured with multiple colors). Some non-limiting examples of a graphic include: a handlebar mustache, stars, a rainbow, a beard, chin whiskers, a monster face, a smiley face, etc. In another embodiment, the inside surface of the removable insert is scented, such as with cinnamon scent, mint scent, citrus scent, bubble gum scent, or other scent, to provide a pleasing scent to the patient while being ventilated. It is appreciated that the removable insert  120 A may be dosed with medication for a controlled release to the patient via either a nasal entry or mouth entry. 
     In another embodiment, therapeutic devices can be incorporated with the removable insert. For example, a bite plate on the inside surface can be incorporated into the removable insert to function as both a bite plate and a cover for the mask. It is appreciated that any number of therapeutic devices could be incorporated with insert  120 A on the inside surface (facing patient) and/or on the outside surface (facing away from the patient). 
     The removable insert may also be coated in the inside surface with an anti-fogging layer to reduce fogging on the inside surface. Anti-fog coating assists in maintaining a transparent surface which allows an unimpeded view of the nose and lips of a patient, so that a caregiver may easily assess the patient without requiring removal of either patient interface  111  or removable insert  120 A (or other removable insert  120  which is coated with anti-fog coating on its interior surface). 
     Referring now to  FIG. 22 , a method  2200  for accessing a mouth and/or nose region of a ventilated patient is provided. In one embodiment, access to the mouth and/or nose region of a patient is provided while simultaneously ventilating the patient. With method  2200  of, mouth and/or nose region access can be achieved without requiring removal of the mask or mask strapping system from the patient. At  2202 ,  2200  includes ventilating the patient. 
     At  2204 , method  2200  includes accessing a frame portion of a mask surrounding the mouth and/or nose region of the patient wherein the frame region is coupled with a semi-rigid retention strap for maintaining positive pressure between the frame portion and the mouth region of the patient. 
     At  2206 ,  2200  includes removing a removable insert that is configured to physically attach and detach from the frame portion without requiring removal of said frame portion or said retention strap from said patient while simultaneously ventilating the patient. 
     After the removable insert is removed, access to the nose and/or mouth region of the patient is achieved while simultaneously ventilating the patient. 
     It is appreciated that the replaceable insert can be used for any number of functions. For example, the removable insert can be selected to provide a therapeutic function to the patient such as a bite block, drug delivery, oral and/or nasal care, feeding, suction, etc. The removable inserts can be configured with any number of ports, filters, drug delivery systems, etc., and can also be colored or include a graphic design. The removable insert enables access to the nose and/or mouth region of the patient while not interrupting ventilation of the patient or requiring removal of the mask from the patient. 
     Section 7 
     Lateral Gas Line Configuration 
     Various embodiments described herein include a lateral configuration of gas delivery limbs coupled with a ventilation mask. The lateral configuration can be used in single limb applications as well as multiple limb applications. However, a dual configuration using bilateral limbs facilitates a cross flow of air across a respiratory opening region (i.e., at least the nose opening and/or mouth opening) of a patient which purges dead space and thus improves ventilation of the patient. In one embodiment, the lateral gas line configuration enables ventilation of a patient even with a removable front portion of the mask in the removed position. This lateral configuration of the gas delivery limbs facilitates access to the nose and/or mouth region of the patient while simultaneously ventilating the patient. While only bilateral limbs are depicted (limb on each lateral side of a patient interface and thus on each side of a patient&#39;s face when donned), it is appreciated that only one lateral limb, on either lateral side of the patient interface, may be utilized in some embodiments. 
     The lateral gas line configurations described herein are also configured to improve comfort and stability of the mask on the patient. For example, in one embodiment, a gas limb is coupled with the mask via a swivel connection which enables the gas limb to swivel with respect to the mask. The swivel mount(s) between the gas limb and the mask frame enables free movement of the gas limb(s) without imparting torque on the mask itself. By reducing the torque on the mask frame, even pressure can be achieved between the mask and the patient, thus improving patient care and comfort. 
     Referring back to  FIG. 1 , a bilateral gas line configuration is shown. Breathing circuit  140  includes limbs  143  and  144  which are shown to be disposed in a lateral configuration with respect to the temporal region of the patient. The limb ( 143 ,  144 ) may be coupled to the frame portion  125  via a swivel port connection which enables the limb to rotate with respect to the frame portion  125  without imparting torque to the frame portion of the mask. It is appreciated that the swivel connection between the frame portion  125  and the limb enables the limbs to be moved from a lateral position to a front position shown in  FIG. 2  where the limb  143  is shown to be rotated to the front of the patient. In this embodiment, the limbs  143 ,  144  are positioned such that the patient can lay on the side of their head without having a breathing tube in the way or interfering with ventilation. In one embodiment, limbs  143  and  144  are coupled at Y connector  142  where the Y connector  142  includes one or more swivel connectors. 
       FIG. 3  shows a bilateral gas line configuration with breathing limbs  143  and  144  positioned laterally with respect to the patient&#39;s head. In this embodiment, a front removable insert  120 A is shown in the removed position. With the lateral gas line configuration described herein, ventilation can occur with the front removable insert in the removed position because the gas flow is configured to flow across a respiratory opening region i.e., at least the nose opening and/or mouth opening) of the patient. With the removable insert in the removed position, gas flow can still be delivered to the patient. The described lateral gas line configurations facilitate simultaneous ventilation of a patient while enabling access to the mouth and/or nose region of the patient. 
     Referring back to  FIG. 7 , one or more limb of breathing circuit  140  may be coupled with strap system  111 . For example, region  715  may include a fastener to removably couple limb  143  to side strap  112  of strap system  111 . In this embodiment, at least one portion of the breathing circuit  140  is configured in a parallel relationship with a strap  112  of strap system  111 . It is appreciated that orifices  722  may be configured as swivel connections that enable swivel movement of the connected device or tube. 
     In one embodiment, gas delivery orifices  722  are non-concentric with respiratory opening regions (mouth opening region and nasal opening regions) of a patient. In other words, gas delivery orifice(s)  722  are shifted laterally, away from the midline, with respect to any of these openings. Furthermore, gas delivery orifice  722 - 1  and  722 - 2  are shifted laterally with respect to front portion  120 ; that is, they do not define an opening through any part of front portion  120 . 
     Section 8 
     Quick Donning Headgear 
     Various embodiments include a quick donning headgear for patient ventilation. The quick donning headgear described herein enables quick and intuitive application and removal of the headgear so as to improve patient care and reduce time spent donning and removing the headgear from the patient. 
     In some embodiments, the headgear apparatus includes a semi-rigid strap system that enables intuitive application to the patient. The semi-rigid straps maintain a head-shape of the strap system even when not in use. The semi-rigid design enables faster donning of the headgear as opposed to conventional strap systems because the straps are already pre-arranged in the proper configuration prior to use, thus reducing the effort and/or time involved in applying and/or removing the device. The semi-rigid shape also requires less adjustment compared to conventional strapping systems because it is already in the shape of a human head. It is appreciated that any portion(s) of head strap  111  may include a ridged or semi-rigid material. It is also appreciated that the semi-rigid material may be flexible. 
     Referring back to  FIG. 1 , head strap  111  includes side straps  112  ( 112 - 1 ,  112 - 2 ,  112 - 3  and  112 - 4  (not visible in  FIG. 1 , but illustrated in  FIG. 7 ). In one embodiment, any portion of straps  112  could be formed of a ridged or semi-rigid material and/or may have elastic properties. In one embodiment, straps  112  retain a head like shape when not applied to a patient. 
     In one embodiment, straps  112  may include a portion that is semi-rigid and also flexible so that the head shape can be expanded for larger patients without requiring adjustment of straps  112  at the frame portion  125 . The head-shape of the strap system  111  also enables greater securing force distribution between the patient&#39;s skin and the mask structure because less adjustment is required. Depending on the configuration (nasal, oral, or oral/nasal) of a patient interface  110  which is utilized with strap system  111 , the head-shape of the strap system  111  evenly distributes the force around either the patient&#39;s mouth region, nose region, or both the mouth region and nose region to reduce possible skin irritations and improve patient comfort. 
     Referring back to  FIG. 7 , in some embodiments, one or more of side straps  112  may be configured to change color, such as from opaque to translucent or from opaque to transparent, or from a lighter shade to a darker shade, in response to stress being applied to the side strap  112  which is indicative of over tightening of the side strap  112 . Similarly, in some embodiments, one or more of side straps  112  may be configured to change color, such as from opaque to translucent or from opaque to transparent, or from a lighter shade to a darker shade such that an embedded colored thread  712  becomes visibly exposed via the non-patient facing side of a side strap  112  in response to stress being applied, to the side strap  112  which is indicative of over tightening of the side strap  112 . 
     Referring back to  FIG. 2 , the quick donning headgear system  111  may include a quick release tab  212  that can be used, for rapid removal of the patient interface  110  from the patient in the event of an emergency. The quick release tab  112  can also be used in donning of the headgear to as to adjust the position of the strap system  111  on the patient&#39;s head. 
     The semi-rigid construction of head strap system  111  provides some amount of inherent rigidity so that when it is in storage, it can be collapsed; but when it&#39;s removed from collapsed storage, it easily and naturally returns to a general head shaped structure, so that it is visibly obvious how to position and install head strap system  111  on patient  101  when donning patient interface  110 . In this manner, there is no need to sort out where the front, back, top, or bottom is located. In one embodiment, patient interface  110  is packaged with head strap system  111  already pre-attached with frame  125 , an that when unpackaged the semi-rigid structure of head strap system  111  causes it to look somewhat like a helmet that can just be pulled quickly over the head and face area of patient  101 , much like putting on a catcher&#39;s mask. 
     Section 9 
     Smart Connections 
     Various embodiments include “smart connectors” for use with patient ventilators, “Smart” refers to a feature that is user friendly and aids in or prevents misconnections with a ventilator that would configure ventilation improperly for a patient. The smart connectors enable proper configuration of a ventilation system and also can be used to determine continuity of the system. For purposes of the present description, the term “continuity” is used to describe the physical continuity of the ventilation system, meaning that correct parts are used and that the correct parts are properly connected and functioning properly. 
     In one embodiment, physical similarities and dissimilarities of various ventilation components are used to enable compatible parts to couple together while preventing dissimilar or non-compatible parts from being used. In this way, non-compatible parts are not physically able to couple with non-compatible parts, thus preventing an improper configuration of the system from being used with a patient. Moreover, with respect to the proper connection point, there may be only one orientation in which a smart connector can be coupled to the connection point on the ventilator (in order to prevent inadvertent misconnection). This may be accomplished via design feature (shape), labeling, color coding, or combination of these features. In another embodiment, identifiers such as color, barcode, RFID, etc. are used to distinguish similar and dissimilar parts. 
     For example, in one embodiment, different classes of parts (e.g., for various patient populations, flow rated, type of ventilation, etc.) can be configured to have unique connector ends that only enable compatible parts to mate with. The special physical configuration of various parts also prevents non-compatible parts to be used. 
     In another embodiment, the ventilation parts can be color coded. In this embodiment, parts with the same color can be considered compatible and can be used together. Parts with different colors can be considered non-compatible and should not be used together. When looking at a ventilation configuration, a part with a different color from the rest is easily identified as non-compatible and should be replaced with a compatible part with the same color as the rest. In one embodiment, different ventilation methods (e.g., single or dual limb) have different colors indicating different uses. In another embodiment, different colored parts are used to differentiate parts for different patient populations. 
     In another embodiment, parts with different colors can be compatible. In this embodiment, semi-transparent parts of various colors can be used to create “good” colors and “bad colors.” For example, a yellow part can be combined with a blue colored part to create a “good” color of green while a blue part combined with a red part create a “bad” color of purple. It is appreciated that any number of colors, patterns, pictures or any other unique markings could be used in accordance with the embodiments described herein to distinguish ventilation parts. 
     In another embodiment, various parts of the ventilation system can include a machine readable code or identifier that enables tracking and monitoring of the parts of the ventilation system. For example, in one embodiment, one or more parts of the ventilation system include a barcode or RFID tag that enables identification of the parts and enabled determination of system configuration. In this embodiment, part compatibility can be verified and system configuration can be verified. In one embodiment, the ventilator includes a reader that can read the identifier associated with the parts to determine compatibility and/or system configuration. 
     In another embodiment, one or more parts of the ventilation system include an electrical lead for enabling a continuity check of one or more portions of the ventilation system. When various parts with the wire lead are coupled, a continuous wire lead is established between the parts. A signal can be passed through the lead to check the lead is continuous. In this embodiment, inadvertent disconnection between any of the parts can be detected, thus improving patient care and ventilation functions. 
     Referring to  FIG. 23 , a ventilator  160  is shown comprising a signal reader  2300  and a configuration determiner  2305 . The breathing circuit  140  includes a wire lead  2304  for enabling the signal reader  2300  to determine continuity of at least a portion of breathing circuit  140 . In one embodiment, the signal reader  2300  provides a signal to the electrical lead  2304  and determines continuity based on the signal returned. 
     In one embodiment, the signal can also be used to determine a configuration of the ventilation system. For example, various parts can have electrical components that enable the signal reader to identify which parts are in the system and can determine their configuration based on sending and receiving a signal over electrical leas  2304 . 
     In another embodiment, one or more parts of the ventilation system include a machine readable identifier such as an RFID or barcode. In this embodiment, the signal reader  2300  is configured to read the corresponding barcode and/or RFID to perform system configuration and continuity checks. It is appreciated that in one embodiment, the configuration determiner  2305  is also configured to determine configuration information based on the RFID signal and/or barcode information. 
     Referring to  FIG. 24 , a method  2400  for checking continuity of a breathing circuit is provided. At  2402 , a signal is provided, to a first end of an electrical lead of a breathing circuit. In one embodiment, one or more parts of the ventilation system include a wire lead that can be used to transmit a signal to determine continuity of that part and/or any parts coupled with that part. 
     At  2404 , the signal is transmitted to a second end of the electrical lead. Provided the electrical lead is continuous, at  2406 , the signal is received at a second end of the electrical lead and at  2408 , it can be determined that the breathing circuit is continuous based on the received signal. 
     Provided the electrical lead is non-continuous, at  2410 , the signal is not received at a second end of the electrical lead and at  2412 , it can be determined that the breathing circuit is non-continuous based on the received signal. At this point, an alert can be generated to signal the breathing circuit is discontinuous and may need to be reconfigured. 
     Referring now to  FIG. 25 , a method  2500  for determining configuration of a breathing circuit is provided. At  2502 , a signal is provided at a first end of an electrical lead of a breathing circuit. At  2504 , the signal is transmitted to a second end of the electrical lead. At  2506 , the signal is received at the second, end, of the electrical lead. At  2508 , configuration of the breathing circuit is determined based on the signal received. 
     In one embodiment, as the signal is transmitted through the electrical lead, any number of modifications to the signal could be performed by any number of components in the system. The modification of the signal enables the signal reader  2300  of  FIG. 23  to determine configuration of the breathing circuit. For example, a “smart” connector may include a microchip that enables access to real-time data associated with the part or the ventilation system as a whole. 
     Section 10 
     Tube Placement in Non-Invasive Ventilation 
       FIGS. 26A-26C  illustrate detail views of a self-sealing tube insertion region  630 , according to various embodiments. Some embodiments of a self-sealing tube insertion region  630  were previously described in conjunction with  FIG. 6 , and  FIGS. 26A-26C  further extrapolate on those embodiments. 
     As illustrated, in  FIG. 26A , bridge  631  and cushioning material  633  (which defines and includes self-sealing tube opening  632  may be removably coupled with facial skin interface  130 , in one embodiment. For example, bridge  631  may be coupled to facial skin interface  130  via an adhesive with a low shear force which may be used one or more times without exhausting its adhesion abilities. Additionally or alternatively, bridge  631  may be positioned and then held in place (as depicted in  FIG. 6 ) by the securing force which is supplied by head strap system  111 . By being removably coupled with facial skin interface  130 , a portion of the tube insertion region can be decoupled from patient interface  110  when patient interface  110  is doffed. Tube  647  may be an orogastric tube, nasogastric tube, or carbon dioxide sampling tube. If tube  647  is orogastrically or nasogastrically inserted into patient  101 , then this portion of tube insertion region can be decoupled from patient interface  110  when patient interface  110  is doffed. This allows the tube  647  to remain in place, without being removed or having its function interfered with in anyway by the doffing of patient interface  110 . 
     As depicted in  FIG. 26A  self-sealing tube insertion region  630  can be coupled or decoupled with facial skin interface  130  and self-seals about tube  647  when tube  647  is disposed in opening  632 , between the facial skin of patient  101  facial skin interface  130 . As previously described, bridge  634  diverts this securing force around tube  647  while tube  647  is inserted in opening  632 . Cushioning material  633  may be foam, silicone, TPE, or other cushioning material. In one embodiment, bridge  631  and cushioning material  633  may be the same material but in different thicknesses or configurations to provide different structural functionality (e.g., bridging versus cushioning/sealing). Cushioning material  633  seals opening  632  when tube  647  is not present expanding to fill opening  632  which may be a piercing through cushioning material  633 . Similarly, cushioning material  633  conforms to tube  647 , when inserted into opening  632 , and self-seals around tube  647  to prevent unintentional leakage of gases from patient interface  110 . 
     As depicted in  FIG. 26B , in one embodiment, opening  632  may be a slit  632 A defined within cushioning material  633 . Tube  647  may be an orogastric tube, a nasogastric tube, a carbon dioxide sampling tube, a respiratory gas sampling tube, or other type of tube. Tube  647  can be inserted and removed from slit  632 A without affecting positioning or function of tube  647 . For example, if tube  647  is orogastrically or nasogastrically inserted into patient  101 , tube  647  may be inserted or removed into slit  632 A without removing tube  647  or disturbing the function of tube  647 . Slit  632 A comprises a self-sealing tube receiving opening, in that cushioning material  633  expands to removably seal about tube  647  when tube  647  is disposed in slit  632 A. Similarly, cushioning material expands to seal slit  632 A closed when tube  647  is not present. In some embodiments a removable, reusable (e.g., low shear force, low tack) adhesive is applied within slit  632 A to facilitate sealing of slit  632 A when no tube is present in slit  632 A and to facilitate removable sealing of slit  632 A about a tube  647  (when inserted). 
     As depicted in  FIG. 26C , in one embodiment, opening  632  may be a gap  632 B defined in a bladder feature  836  of facial skin interface  130 . Gap  632 B functions in a similar fashion to slit  632 A. Gap  632 B may be defined in a single bladder  836  or in a space between a pair of adjacent bladders  836 . For example, if tube  647  is orogastrically or nasogastrically inserted into patient  101 , tube  647  may be inserted or removed into gap  632 B without removing tube  647  or disturbing the function of tube  647 . Gap  632 B comprises a self-sealing tube receiving opening, in that bladder feature  836  removably seals about tube  647  when tube  647  is disposed in gap  632 B. This sealing can be due to one or more factors such as compressing of bladder feature  836  by the securing force supplied by head strap system  111  and/or by inflation of bladder(s)  836  by inhalation gases present within patient interface  110  and supplied from ventilator  160  (or by other source of gas or fluid). For example, the bladder(s)  836  may be sealably inflated around tube  647 . Similarly, bladder feature  836  seals gap  632 B closed when tube  647  is not present. In some embodiments a removable, reusable (e.g., low shear force, low tack) adhesive is applied within gap  632 B to facilitate sealing of gap  632 B when no tube is present in gap  632 B and to facilitate removable sealing of gap  632 B about a tube  647  (when inserted). As can be seen, tube  647  can be received in and removed front gap  632 B independently of the donning and doffing of patient interface  110 . When tube  647  is inserted within gap  632 B, bladder feature  836  diverts the securing force (supplied by head strap system  111 ) around tube  647  such that tube  647  is not pressed against the facial skin of patient  101  to form a pressure point. 
     Section 11 
     Non-Invasive Ventilation Exhaust Gas Venting 
     As described previously with reference to  FIG. 7 , in one embodiment, filter media  123 A can be used in conjunction with or in place or exhaust gas vent ports  123  which have been depicted elsewhere herein. Typically, exhaust gas vent ports  123  are open to the atmosphere. Instead of open vent holes, in one embodiment, filter media  123 A is included in addition to vent ports  123  or alternatively utilized to replace vent ports  123 . Filter media  123 A filters contagions (e.g., bacteria, viruses, drugs (in particular aerosolized or nebulized drugs), and/or chemicals) from the exhaust gas which is exhausted through filter media  123 A. The exhausted gas may comprise exhaled breath, excess fresh respiratory gas, or a combination thereof. In addition to filtering, filter media  123 A diffuses the gases that are exhausted there through. Filter media can be composed of any known type of respiratory gas filter media, including, but not limited to, paper, activated carbon, synthetic woven fiber (e.g., polyester, Gortex® or similar expanded polytetrafluoroethylene (ePTFE)), open cell foam, glass fiber, natural woven fiber (e.g., bamboo, cotton), or combination thereof. 
     In some embodiments, filter media  123 A provides a controlled pressure drop in addition to filtering contagions from exhaled gases as the exhaled gases pass through. This controls an expulsion flow of exhaled breath and can also control an intentional leak rate of fresh respiratory gases front within patient interface  110 . Such intentional leak rate control can manage the pressure of fresh respiratory gases within patient interface  110  such that a desired pressure range of continuous positive airway pressure is achieved. A variety of factors including one or more of composition, thickness, layers, surface area, and porosity of the media of filter media  123 A can be selected, in some embodiments, to either filter contagions, provide a designated flow/intentional leak rate to control internal pressure of patient interface  110 , or both. 
     In some embodiments, the filter media  123 A can simultaneously filter and vent, thus eliminating the need have separate vent holes. In one embodiment, interchangeable patient interface insert  120 D can be removed and replaced with a new interchangeable patient interface insert  120 D when filter media  123 A becomes clogged, soiled, or has surpassed its recommended replacement interval. In another embodiment, filter media  123 A is, itself, replaceable. 
     In some embodiments, filter media  123 A may be imbued with one or more substances. For example in one embodiment, filter media  123 A may be imbued with a fragrance such as cinnamon, mint, peppermint, spearmint, wintergreen, citrus, fruit, bubblegum or the like in order to mask odors of exhaust gases which are not eliminated by filter media  123 A. In one embodiment, filter media  123 A, may be imbued with a desiccant (e.g., silica, activated charcoal, or the like) in order to assist in controlling moisture level on the interior of patient interface  110  to reduce fogging and/or to improve patient comfort, and in order to maintain filter media  123 A in a dry state which is can kill viruses and is non-conducive to formation of funguses. Along these lines, transparent portions of domed front portion  120  or similar interchangeable insert  120 D (and the like) may have interior portions coated with an anti-fog coating to prevent fogging and to maintain transparency both for patient comfort and so that medical personnel may easily view inside of patient interface  110 . In one embodiment, filter media  123 A is imbued with an antibacterial, antimicrobial, and/or antifungal substance (e.g., silver, an antibiotic, etc.) 
       FIG. 27  illustrates a replaceable filter cartridge  2724 , in accordance with some embodiment. Filter cartridge  2724  is shown in an uninstalled state. Arrow  2750  illustrates where filter cartridge  2724  may be snap fit or otherwise coupled with interchangeable insert  120 D, or a similar interchangeable or non-interchangeable domed front portion  120 . This is one mechanism for changing for replacing filter media  123  when clogged or past a time of suggested usability. In other embodiments, filter media  123 A is an integral portion of interchangeable insert  120 D (rather than a replaceable cartridge), and the entirety of interchangeable insert  120 D is removed and replaced in order to replace filter media  123 . In some embodiments a larger portion of interchangeable insert  120 D may be composed of filter media  123  than depicted in  FIG. 27  or other figures herein. For example, in some embodiments up to the entire visible exterior surface of interchangeable insert  120 D may be composed of one or some combination of filter materials. 
     Section 12 
     Non-Invasive Ventilation Facial Skin Protection 
     Many features for skin protection have been discussed previously herein. Additional features which may be used alone or in combination with the previously discussed skin protection features (or with other skin protection features that are described in Section 13) include features which eliminate fluid via wicking and/or purging, and features which utilize an imbued substance to actively soothe/protect the facial skin in one or more areas which receive contact from a patient interface as a result of non-invasive ventilation. 
       FIG. 28  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal  135  and a facial skin interface  130 , according to an embodiment. As illustrated by enlarged detail  2801 , the skin contacting portion of facial skin interface  130  is configured with a plurality of micro-grooves  2825  which provide small passageways between skin contacting peaks  2824  which allow air flow. In one embodiment, micro-grooves  2825  may be 0.075 inches or narrower in width, in another embodiment some of micro-grooves  2825  may be 0.050 inches or narrower in width. In one embodiment, some or all of microgrooves  2825  may be between 0.075 and 0.005 inches in width. When patient interface  110  is donned and coupled with ventilator  160 , pressurized, fresh respiratory gas flows through micro-grooves  2825  in a controlled and intentional leak as illustrated by gas flow path  2826 . This controlled and intentional leak facilitates a controlled purging of moisture by both forcing moisture out through micro-grooves  2825 , and by evaporating moisture. This controlled leak assists in purging moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between facial skin interface  130  and the facial skin of patient  101  that is in contact with facial skin interface  130  when patient interface  110  is donned. In one embodiment, micro-grooves  2825  may be a removable/replaceable component which is removably coupled with facial skin interface  130 . Thus when micro-grooves  2825  get clogged or exceed a recommended service time, this replaceable component can be replaced. 
     As illustrated in  FIG. 28  by enlarged detail  2833 , the skin contacting portion of compliant nose bridge seal  135  may additionally or alternatively be configured with a plurality of micro-grooves  2835  which provide small passageways between skin contacting peaks  2834  which allow air flow. In one embodiment, micro-grooves  2835  may be 0.075 inches or narrower in width, in another embodiment some of micro-grooves  2835  may be 0.050 inches or narrower in width. In one embodiment, some or all of microgrooves  2835  may be between 0.075 and 0.005 inches in width. When patient interface  110  is donned and coupled with ventilator  160 , pressurized fresh respiratory gas flows through micro-grooves  2835  in a controlled and intentional leak as illustrated by gas flow path  2836 . This controlled and intentional leak facilitates a controlled purging of moisture by both forcing moisture out through micro-grooves  2835 , and by evaporating moisture. This controlled and intentional leak assists in purging moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between compliant nose bridge seal  135  and the facial skin of patient  101  that is in contact with compliant nose bridge seal  135  when patient interface  110  is donned. In one embodiment, micro-grooves  2835  may be a removable/replaceable component which is removably coupled with compliant nose bridge seal  135 . Thus when micro-grooves  2835  act clogged or exceed a recommended service time, this replaceable component can be replaced. 
     As illustrated in  FIG. 28 , in one embodiment, facial skin interface  130  additionally or alternatively includes an extended chin portion  832 , which may include a chin bellows  2850  and/or a jaw bellows  2855 . Chin bellows  2850  and jaw bellows  2855  each include a plurality of bellows formed of a cushioning material such as silicone. In various embodiments, chin bellows  2850  and/or jaw bellows  2855  may be formed of the same material as facial skin interface  130 . Chin bellows  2850  expands and contracts in response to up and down movement of the chin of patient  101 , such as when patient  101  opens and closes his/her mouth during speaking. Jaw bellows  2850  is inboard of the sealing surface of facial skin interface  130 , and expands and contracts in response to up, down, and side-to-side movement of the jaw of patient  101 , such as when patient  101  opens and closes his/her mouth during speaking, yawning, or for a medical procedure accomplished through an open front portion of patient interface  110 . The expansion and contraction provided by chin bellows  2850  and/or jaw bellows  2855  allows for some linear and/or side-to-side movement of the mouth, chin and/or jaw of patient  101  while maintaining contact between facial skin interface  130  and the face of patient  101 . This can increase patient comfort and decrease the need to constantly manually adjust patient interface  101  in response to unintentional leaks caused by movement of the jaw and/or chin of patient  101 . Additionally, a caregiver or patient may access an oral or nasal opening or region through a removable insert  120  and jostle or move portions of patient interface  110  without causing unintentional leaks. This is because the accordion like bellows features of chin bellows  2850  and/or jaw bellows  2855  allow for some flexing movement such that outer portions of patient interface  110  while the facial skin contacting portions remain undisturbed or relatively undisturbed in their seating against the facial skin of the patient. 
       FIG. 29  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal  135  and a facial skin interface  130 , according to an embodiment. As illustrated by enlarged detail  2901 , the skin contacting portion of facial skin interface  130  comprises a porous material  2925  (e.g., open cell foam) which provides a plurality of small openings and small passageways in/near its surface, due to the porosity. When patient interface  110  is donned and coupled with ventilator  160 , pressurized fresh respiratory gas flows through porous material  2925  in a controlled and intentional leak as illustrated by gas flow path  2926 . This controlled and intentional leak facilitates a controlled purging of moisture by both forcing moisture out through the pores of porous material  2925 , and by evaporating moisture. This controlled and intentional leak assists in purging moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between facial skin interface  130  and the facial skin of patient  101  that is in contact with facial skin interface  130  when patient interface  110  is donned. In one embodiment, porous material  2925  may be a removable/replaceable component which is removably coupled with facial skin interface  130 . Thus when porous material  2925  gets clogged or exceeds a recommended service time, this replaceable component can be replaced. 
     As illustrated in  FIG. 29 , the skin contacting portion of compliant nose bridge seal  135  may additionally or alternatively be configured with a similar porous material  2935  which provide small passageways and openings in/near its surface, due to the porosity. When patient interface  110  is donned and coupled with ventilator  160 , pressurized flesh respiratory gas flows through pores of porous material  2935  in a controlled and intentional leak as illustrated by gas flow path  2936 . This controlled and intentional leak facilitates a controlled purging of moisture by both forcing moisture out through pores of porous material  2935 , and by evaporating moisture. This controlled leak assists in purging moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between compliant nose bridge seal  135  and the facial skin of patient  101  that is in contact with compliant nose bridge seal  135  when patient interface  110  is donned. In one embodiment, porous material  2935  may be a removable/replaceable component which is removably coupled with compliant nose bridge seal  135 . Thus when porous material  2935  gets clogged or exceeds a recommended service time, this replaceable component can be replaced. 
     As illustrated in  FIG. 29 , in one embodiment, facial skin interface  130  additionally or alternatively includes an extended chin portion  832 , which may include a chin bellows  2850  and/or may include a jaw bellows  2850 . 
       FIG. 30  illustrates a perspective view of the skin contacting portion of a compliant nose bridge seal  135  and a facial skin interface  130 , according to an embodiment. As illustrated by enlarged detail  3001 , the skin contacting portion of facial skin interface  130  is comprises a wicking material  3025  (e.g., a woven cloth such as cotton, wool, bamboo, polyester micro fiber, or other known wicking materials) which provides a surface that naturally wicks fluids and moisture. In some embodiments, the wicking surface of facial skin interface  130  may be textured. This wicking property assists in wicking moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between facial skin interface  130  and the facial skin of patient  101  that is in contact with facial skin interface  130  when patient interface  110  is donned. In one embodiment, wicking material  3025  may be a removable/replaceable component which is removably coupled with facial skin interface  130 . Thus when wicking material  3025  gets clogged, saturated, or exceeds a recommended service time; this replaceable component can be replaced. In some embodiments, the wicking material  3024  may be porous enough to exhibit purging properties as well as wicking properties. Arrow  3026  illustrates the direction of gas flow through a porous wicking material  3024 . 
     As illustrated in  FIG. 30 , the skin contacting portion of compliant nose bridge seal  135  may additionally or alternatively be configured with a similar wicking material  3035  (e.g., a woven cloth such as cotton, wool, bamboo, polyester micro fiber, or other known wicking materials) which provides a textured surface that naturally wicks fluids and moisture. Wicking material  3035  provides a textured wicking surface for interfacing with nasal skin of patient  101  when patient interface  110  is donned. This wicking property assists in wicking moisture and thus preventing accumulation of fluids (e.g., sweat, condensation, or the like) and/or eliminating fluids from within facial interface  110  (the portion which covers nose and/or mouth openings when donned) and from between compliant nose bridge seal  135  and the facial skin of patient  101  that is in contact with compliant nose bridge seal  135  when patient interface  110  is donned. In one embodiment, wicking material  3035  may be a removable/replaceable component which is removably coupled with compliant nose bridge seal  135 . Thus when wicking material  3035  gets clogged, saturated, or exceeds a recommended service time; this replaceable component can be replaced. In some embodiments, wicking material  3034  may be porous enough to exhibit purging properties as well as wicking properties. Arrow  3036  illustrates the direction of gas flow through a porous wicking material  3034 . 
     As illustrated in  FIG. 30 , in one embodiment, facial skin interface  130  additionally or alternatively includes an extended chin portion  832 , which may include a chin bellows  2850  and/or may include a jaw bellows  2850 . 
     In some embodiments, all or a portion of facial skin interface  130 , compliant nose bridge seal  135 , micro-grooves  2825 , porous material  3925 , and/or wicking material  3025  is imbued with one or more substances which actively soothe/protect the facial skin in one or more areas which receive contact from a patient interface as a result of non-invasive ventilation. Such substances may include one or more of an antibacterial substance (e.g., tricolsan, silver, or other known substances with antibacterial and/or antifungal properties), an emollient, and/or a vasodilator. An imbued antibacterial can prevent/destroy a bacteria and/or a fungus which may inhabit the environment where facial skin of a patient contacts or is enclosed by patient interface  110 . An imbued emollient softens and moisturizes the skin, and can thus assist in prevention of chafing, rashes, and skin necrosis caused by prolonged contact between patient interface  110  and facial skin of patient  101 . A imbued vasodilator dilates (widens) blood vessels by relaxing smooth muscle cells of the vessel walls, thus improving blood flow in facial skin. Such improved blood flow can assists in preventing necrosis that can occur if patient interface  110  causes a pressure point on facial skin of patient  101 , or can prolong the amount of time that patient interface  110  can be worn without damaging facial skin of patient  101 . 
     In some or all embodiments, all or portions of facial skin interface  130  may be treated with a low shear force adhesive such that a slight tackiness (similar to that of a Post-It® note) is achieved. This tackiness improves mask stability, thus reducing the amount of sliding and decreasing irritation to the skin caused by constant sliding and shifting. 
     Section 13 
     Non-Invasive Ventilation Facial Skin Protection 
     Referring again to  FIG. 8A , a patient interface which includes a zygomatic facial interface  831  ( 831 - 1 ,  831 - 2 ) is illustrate, according to an embodiment. In one embodiment, zygomatic facial interface is an extension of or is coupled with facial skin interface  130 . In one embodiment, first zygomatic interface portion  831 - 1  sealably interfaces with facial skin covering a left zygomatic arch region of patient  101 , while second zygomatic interface portion sealably interfaces with facial skin covering a right zygomatic arch region of patient  101 . In response to application of a securing force for securing patient interface  110  and facial skin interface  130  over a mouth and/or nose opening of said patient, first portion  831 - 1  and second portion  831 - 2  spreading the securing force away from a nasal bridge of patient  101  and onto to the left and right zygomatic arch regions of patient  101 . The securing force is supplied by a head strap system, such as or similar to head strap system  111 , which supplies the securing force in response to donning of patient interface  110 . In one embodiment, zygomatic facial interface  831  may comprise a plurality of bladders  836 , which may be inflated with a fluid or may be inflated with fresh respiratory gas supplied by ventilator  160 . In some embodiments, zygomatic facial interface  831  includes a moisture purging feature (e.g., micro-grooves  2825  and/or porous material  3025 ) which contacts facial skin of patient  101  and which allows/facilitates a controlled and intentional leak of fresh respiratory gas between the moisture purging feature and the facial skin of patient  101 . In one embodiment, zygomatic facial interface  831  includes a wicking feature (e.g., wicking material  3025 ) which contacts facial skin of patient  101  and wicks fluid from the contacted facial skin. In one embodiment, a skin contacting region of zygomatic facial interface  831  is imbued with at least one of an emollient, an antibacterial, and a vasodilator. In one embodiment, a skin contacting region of zygomatic facial interface is imbued with two or more of an emollient, an antibacterial, and a vasodilator. 
     In various embodiments, a patient interface  110  which utilizes zygomatic facial interface  831  may include extended chin portion  832  (which may further include chin bellows  2850 ). It is appreciated that other features described herein may be included, in various combinations with a patient interface  110  which includes zygomatic facial skin interface  831 . For example, in some embodiments, a patient interface  110  which utilizes zygomatic facial interface  831  may include compliant nose bridge seal  135 , corrugations, jaw bellows, tube insertion region, microgrooves, porous material, wicking material, and nasal passage opening features, among other features. 
     Although features have been illustrated and described herein as applied to oral/nasal patient interfaces which seal about the mouth and nose openings of a patient, it is appreciated that the features described herein may also be applied to patient interfaces which seal only about a mouth opening of a patient or only about a nose opening of a patient. 
     The foregoing descriptions of specific embodiments have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the presented technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The figures and embodiments were chosen and described in order to best explain the principles of the presented technology and its practical application, to thereby enable others skilled in the art to best utilize the presented technology and various embodiments with various modifications as are suited to the particular use contemplated. While the subject matter has been described in particular embodiments, it should be appreciated that the subject matter should not be construed as limited by such embodiments, but rather construed according to the following claims.