Patent Publication Number: US-11654255-B2

Title: Jet pump adaptor for ventilation system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/020,032, filed Sep. 6, 2013 and entitled “JET PUMP ADAPTOR FOR VENTILATION SYSTEM,” the entire disclosure of which is wholly incorporated by reference herein. 
    
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to systems and methods for controlling delivery of a pressurized flow of breathable gas to a patient and, more particularly, to an adaptor or attachment which is suitable for integration into the patient circuit of a ventilation system, such as a non-invasive open ventilation system, is configured for attachment to any standard ventilation mask, and is outfitted with a jet pump to facilitate the entrainment of ambient air. 
     2. Description of the Related Art 
     As is known in the medical arts, mechanical ventilators comprise medical devices that either perform or supplement breathing for patients. The vast majority of contemporary ventilators use positive pressure to deliver gas to the patient&#39;s lungs via a patient circuit between the ventilator and the patient. The patient circuit typically consists of one or two large bore tubes (e.g., from 22 mm ID for adults to 8 mm ID for neonatal) that interface to the ventilator on one end, and a patient mask on the other end. Most often, the patient mask is not provided as part of the ventilation system, and a wide variety of patient masks can be used with any ventilator. 
     Current ventilators are designed to support either “vented” or “leak” circuits, or “non-vented” or “non-leak” circuits. In vented circuits, the mask or patient interface is provided with an intentional leak, usually in the form of a plurality of vent openings. Ventilators using this configuration are most typically used for less acute clinical requirements, such as the treatment of obstructive sleep apnea or respiratory insufficiency. In non-vented circuits, the patient interface is usually not provided with vent openings. Non-vented circuits can have single limb or dual limb patient circuits, and an exhalation valve. Ventilators using non-vented patient circuits are most typically used for critical care applications. 
     Vented patient circuits are used only to carry gas flow from the ventilator to the patient and patient mask, and require a patient mask with vent openings. When utilizing vented circuits, the patient inspires fresh gas from the patient circuit, and expires CO2-enriched gas, which is typically purged from the system through the vent openings in the mask. When utilizing non-vented dual limb circuits, the patient inspires fresh gas from one limb (the “inspiratory limb”) of the patient circuit and expires CO2-enriched gas from the second limb (the “expiratory limb”) of the patient circuit. Both limbs of the dual limb patient circuit are connected together in a “Y” proximal to the patient to allow a single connection to the patient mask. When utilizing non-vented single limb circuits, an expiratory valve is placed along the circuit, usually proximal to the patient. During the inhalation phase, the exhalation valve is closed to the ambient and the patient inspires fresh gas from the single limb of the patient circuit. During the exhalation phase, the patient expires CO2-enriched gas from the exhalation valve that is open to ambient. 
     In the patient circuits described above, the ventilator pressurizes the gas to be delivered to the patient inside the ventilator to the intended patient pressure, and then delivers that pressure to the patient through the patient circuit. Very small pressure drops develop through the patient circuit, typically around 1 cmH2O, due to gas flow though the small amount of resistance created by the tubing. Some ventilators compensate for this small pressure drop either by mathematical algorithms, or by sensing the tubing pressure more proximal to the patient. 
     In the prior art, ventilation systems are know which integrate either a venturi or a jet pump. Generally speaking, a venturi functions to speed up a fluid in a tube using a restrictor to create negative pressure. In contrast, a jet pump uses a high speed jet in ambient air to facilitate the entrainment of ambient air. Along these lines, the prior art includes ventilation systems which incorporate entrainment masks and are used for the purpose of delivering air in combination with another therapeutic gas (e.g., oxygen) to a patient. For example, high flow oxygen delivery systems exist that include an air entrainment mask which, in addition to being designed to fit over the patient&#39;s nose and mouth and to connect to oxygen supply tubing, comprises a jet orifice and air entrainment ports. Oxygen under pressure is forced through a small jet orifice entering the mask. The velocity increase causes a shearing effect distal to the jet orifice, which in turn causes room air to be entrained into the mask via the ports formed therein. These oxygen therapy entrainment systems are used to, among other things, deliver proper mixtures of air and oxygen. 
     However, the prior art is generally lacking in providing non-invasive open ventilation systems wherein a jet pump, as opposed to a venturi, is integrated into the tubing of a patient circuit, rather than into the patient interface or mask of the patient circuit. The present invention, as will be described in more detail below, addresses this deficiency in the prior art. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an adaptor or attachment which is suitable for integration into the patient circuit of a ventilation system, such as a non-invasive open ventilation system, is configured for attachment to any standard ventilation mask, and is outfitted with a jet pump which creates pressure and flow by facilitating the entrainment of ambient air. The preferred patient interface used in conjunction with the adaptor of the present invention is a non-vented (or non-leak) nasal mask or full face mask (FFM). However, the adaptor may also be used in conjunction to a traditional vented nasal mask or full face mask, such as those used for continuous positive airway pressure (CPAP), bi-level PAP or bi-level therapy. 
     In accordance with a first embodiment of the present invention, the adaptor comprises a base element and a nozzle element which are operatively coupled to each other. More particularly, the nozzle element may be rotatably connected to the base element as allows for the rotation of the nozzle element relative to the base element. The base element defines a standard 22 mm ISO taper connector which allows for the releasable attachment of the adaptor to any standard ventilation mask. The base element further defines a throat and at least one entrainment port facilitating a path of fluid communication between the throat and ambient air. 
     The nozzle element includes a jet nozzle, and a connector which is adapted to facilitate the fluid coupling of the nozzle element to a bi-lumen tube of the patient circuit, such bi-lumen tube defining both a gas delivery lumen and a sensing lumen which is fluidly isolated from the gas delivery lumen. The connector includes both a delivery port and a sensing port. The jet nozzle and the delivery port collectively define a gas delivery line or lumen which fluidly communicates with the throat of the base element, and is placeable into fluid communication with the delivery lumen of the bi-lumen tube. In addition, the nozzle and base elements, when attached to other, collectively define a pressure sensing line or lumen which is fluidly isolated from both the delivery lumen and the throat, and is placeable into fluid communication with the sensing lumen of the bi-lumen tube. In this regard, a portion of the sensing lumen is defined by the base element (including the sensing port thereof), with another portion of the sensing lumen being defined by the nozzle element. These separate portions of the sensing lumen are brought in fluid communication with each other when the nozzle element is connected to the base element. The jet nozzle, in combination with the throat and the entrainment port, creates a jet pump within the adaptor. It is contemplated that the nozzle element can be molded with different jet nozzle sizes in order to change the performances of the jet pump (e.g., more or less pressure or flow) and can further be color coded so that the user can easily understand the jet pump performance provided thereby. 
     In the patient circuit outfitted with the adaptor, the jet pump in the patient circuit is able to generate a maximum pressure of about 30 cm H2O (and preferably about 20 cm H2O), and a peak flow of about 100 l/min (and preferably 60 l/min). Pressure and flow are generated in a manner wherein the breathable gas (O2, air, or other mixtures of breathable gas) is delivered to the jet nozzle of the jet pump and ambient air is entrained through the entrainment port. The flow of pressurized air is delivered to the patient through the standard ISO taper connection with the non-vented mask. The pressure sensing line of the adaptor is used to sense the pressure in the mask or to trigger a breath when breath-by-breath ventilation is provided by the ventilation system. In the first embodiment, the gas exhaled by the patient may be exhausted through the entrainment port. It is further contemplated that an HME and/or antibacterial filter can be connected between the jet pump and the connector of the mask. 
     In accordance with a second embodiment of the present invention, the jet pump of the adaptor may be equipped with an anti-asphyxia valve (AAV) in order to reduce the back pressure during exhalation. More particularly, an exhalation valve or AAV may be used to decrease expiratory pressure in the case when the throat of the jet pump is too small or in case of failure of the ventilator or gas source. The valve may incorporate a conical diaphragm valve that is stretched to seal against one or more exhalation ports of the adaptor (which are separate from the entrainment port) when there is positive pressure and flow in the jet pump, and opens in a manner unblocking the exhalation ports when the jet pump is not activated (i.e. during exhalation). The same function can be achieved thorough the use of a flapper valve as an alternative to the aforementioned diaphragm. 
     In accordance with a third embodiment of the present invention, the jet pump of the adaptor may be equipped with a exhalation/positive end expiratory pressure (PEEP) valve (or a connection for a third party PEEP valve). More particularly, the jet pump may incorporate a piloted exhalation valve. The valve can be piloted between on/off states or could be piloted in a proportional fashion to achieve positive end expiratory pressure (PEEP) control by using the pressure in the delivery line that feeds the jet nozzle via a pilot line. In this way, the valve opens and closes in sync with the breathing pattern of the patient. During inhalation, when the jet flow is delivered to the jet pump, the valve is closed by the high pressure in the nozzle delivery lumen. During exhalation there is either no flow delivered by the jet nozzle (and hence no pressure in the delivery lumen) and the valve opens, or a small flow and pressure can be maintained in the delivery lumen so that the jet pump can create back pressure in the throat against exhalation and the valve can be servoed with positive pressure to vary the resistance. This latter system results in a controllable PEEP value and requires a careful sizing and matching of the jet pump performances at low flow and the PEEP valve characteristic. This is made easier using a closed loop control over the pressure sensed by the sensing lumen of the patient circuit. The valve can also be used as a PEEP valve by using a spring to maintain PEEP and the pilot line to close during inhalation. In this embodiment the PEEP value can be adjusted by changing the pre-load of the spring (e.g., by rotating a portion of the housing). Optionally, for a better PEEP control, a non-return valve (e.g. an umbrella valve) can be used to close the throat of the jet pump during exhalation. 
     In accordance with a fourth embodiment of the present invention, the jet pump of the adaptor may employ a fixed PEEP valve in the shape of, for example, a flapper valve at the end of the throat. The valve is normally close (i.e., rests against the throat of the jet pump) and opens during inhalation when positive pressure and flow are established by the jet flow coming from the jet nozzle. During exhalation the jet flow is suspended and the valve returns in its close state. On the surface of the valve a plurality of holes ensure that the exhaled gas can be evacuated to the ambient by building a back pressure sufficient to maintain PEEP in the patient&#39;s airways. A range of different valves can be realized so that different PEEP values can be achieved. Color coding can be used to identify the PEEP value. The perforated flapper valve is just one of several modalities which may be used to achieve the same function. Along these lines, the perforations on the flapper could be replaced by grooves on the sealing surface of either the valve or the seat of the throat. The umbrella valve can be used in a similar fashion, with or without orifices/holes within the same. 
     The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein: 
         FIG.  1    is a front perspective view of an exemplary prior art mask suitable for use in conjunction with any jet pump adaptor constructed in accordance with the present invention; 
         FIG.  2    is a front perspective view a jet pump adaptor constructed in accordance with a first embodiment of present invention; 
         FIG.  3    is a bottom view of the jet pump adaptor shown in  FIG.  2   ; 
         FIG.  4    is a cross-sectional view taken along line  4 - 4  of  FIG.  3   ; 
         FIG.  5    is a bottom view of the base element of the jet pump adaptor shown in  FIGS.  2 - 4   ; 
         FIG.  6    is a cross-sectional view taken along line  6 - 6  of  FIG.  5   ; 
         FIG.  7    is a rear perspective view of the nozzle element of the jet pump adaptor shown in  FIGS.  2 - 4   ; 
         FIG.  8    is a front perspective view of the nozzle element of the jet pump adaptor shown in  FIGS.  2 - 4   ; 
         FIG.  9    is a graphical representation of typical characteristic curves corresponding to the functionality of the jet pump adaptor of the first embodiment, the curves being parameterized with jet flow; 
         FIG.  10    is a cross-sectional view a jet pump adaptor constructed in accordance with a second embodiment of present invention; 
         FIG.  11    is a cross-sectional view a jet pump adaptor constructed in accordance with a third embodiment of present invention; and 
         FIG.  12    is a cross-sectional view a jet pump adaptor constructed in accordance with a fourth embodiment of present invention. 
     
    
    
     Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings for which the showings are for purposes of illustrating preferred embodiments of the present invention only, and not for purposes of limiting the same,  FIG.  1    depicts an exemplary prior art patient interface or mask  10  suitable for use with the jet pump adaptor  12  of the present invention, as will be described in more detail below. As indicated above, the preferred patient interface used in conjunction with the adaptor  12  of the present invention is a non-vented (or non-leak) nasal mask or full face mask, the mask  10  being a non-vented full-face mask. In this regard, the mask  10  comprises a body portion  14  which is sized and configured to cover the nose and mouth of a patient. In addition to the body portion  14 , the mask  10  includes a tubular connector portion  16  which is fluidly coupled to the body portion  14 . As also indicated above, though the adaptor  12  is preferably used in conjunction with the non-vented mask  10 , the same may also be used in conjunction with a traditional vented nasal mask or full face mask. 
     The adaptor  12  as constructed in accordance with a first embodiment of the present invention is shown with particularity in  FIGS.  2 - 8   . The adaptor  12  comprises of base element  18  (as shown in  FIGS.  5  and  6   ) and a nozzle element  20  (as shown in  FIGS.  7  and  8   ) which are operatively coupled to each other. More particularly, the nozzle element  20  may be rigidly, rotatably, or threadably connected to the base element  18  in a manner which will be described in more detail below, the rotatable and threadable connections allowing for the selective rotation of the nozzle element  20  relative to the base element  18 . 
     As is best seen in  FIGS.  2 - 6   , the base element  18  includes a connector  22  which is preferably a standard 22 mm ISO taper connector. In this regard, due to its preferred structural attributes, the connector  22  allows for the releasable attachment of the base element  18 , and hence the adaptor  12 , to any standard ventilation mask, including the exemplary mask  10  shown in  FIG.  1   . In this regard, by way of example, the connector  22  is adapted to receive and releasably accommodate the connector portion  16  of the mask  10 . In addition to the connector  22 , the base element  18  defines a throat  24 . More particularly, the throat  24  is defined by a tubular wall  19  which has a generally circular cross-sectional configuration and protrudes into the interior of the connector  22 , as seen in  FIGS.  4  and  6   . The configuration shown in  FIGS.  4  and  6   , wherein the tubular wall  19  protrudes into the interior of the connector  22 , is exemplary only, and is used to reduce the overall length of the adaptor  12 . Adaptors for ISO tapers smaller than 22 mm may have a different architecture and, more particularly, may be longer than the adaptor  12 . The wall  21  defines a distal end or rim  21 . That end of the throat  24  circumvented by the rim  21  fluidly communicates with the interior of the connector  22 . The base element  18  also defines at least one air entrainment port  26  which fluidly communicates with the throat  24 . More particularly, as is also apparent from  FIG.  6   , the entrainment port  26  facilitates the fluid communication of the throat  24  with ambient air. Still further, the base element  18  defines an elongate pressure sensing line or lumen  25  which extends in side-by-side relation to, but is fluidly isolated from, the throat  24 . Like the throat  24 , one end of the pressure sensing lumen  25  terminates at the rim  21  of the wall  19  and fluidly communicates with the interior of the connector  22 . In this regard, a portion of the pressure sensing lumen  25  extends through the wall  19 . The opposite end of the pressure sensing lumen  25  terminates at a recess  27  which is formed within that end of the base element  18  opposite the end defined by the connector  22 . The use of the recess  27  will be described in more detail below. In the base element  18 , an aperture or opening  23  extends between the throat  24  and the bottom, innermost surface of the recess  27 . 
     As best seen in  FIGS.  2 - 4  and  7 - 8   , the nozzle element  20  includes a jet nozzle  28  and a connector  30  which is adapted to facilitate the fluid coupling of the nozzle element  20 , and hence the adaptor  12 , to a bi-lumen tube of a patient circuit including the adaptor  12  and mask  10 . Though not shown, such bi-lumen tube defines both a gas delivery lumen and a sensing lumen which is fluidly isolated from the gas delivery lumen. The jet nozzle  28  has a generally frusto-conical external configuration or shape, and protrudes from a circularly configured mandrel portion  29  of the nozzle element  20 . The connector  30  of the nozzle element  20  includes both a tubular gas delivery port  32  and a tubular pressure sensing port  34  which, as best seen in  FIG.  7   , reside within a common recess  31 . The recess  31  is formed within that end of the nozzle element  20  opposite that defined by the distal end the jet nozzle  28  protruding from the mandrel portion  29 . 
     In the adaptor  12 , the recess  27  formed within the base element  18  has a configuration which is complementary to that of the mandrel portion  29  of the nozzle element  20 . In accordance with the present invention, three (3) different attachment modes may be achieved between the base and nozzle elements  18 ,  20 . In a first attachment mode, the base and nozzle elements  18 ,  20  are rigidly secured to each other. More particularly, the circularly configured mandrel portion  29  is advanced into the complementary, circularly configured recess  27  and secured therein by way of, for example, glue, a weld, or a press fit. In a second attachment mode, the base and nozzle elements  18 ,  20  are rotatably connected to each other. In this regard, the rotatable connection of the nozzle element  20  to the base element  18  is facilitated by the slidable receipt of the circularly configured mandrel portion  29  into the complementary, circularly configured recess  27 . In a third attachment mode, the base and nozzle elements  18 ,  20  are threadably connected to each other. Though not shown, the threadable connection of the nozzle element  20  to the base element  18  may be facilitated by the engagement of male threads formed on the circularly configured mandrel portion  29  to complementary female threads formed within the circularly configured recess  27 . As is seen in  FIG.  4   , in any of the aforementioned attachment modes, the advancement of the mandrel portion  29  into the recess  27  is limited by the abutment of a shoulder  40  defined by the nozzle element  20  and circumventing the mandrel portion  29  thereof against an end surface  42  defined by the base element  18  and circumventing the recess  27  form therein. Both prior to and when such abutment occurs during the advancement of the mandrel portion  29  into the recess  27 , an annular gap or channel  44  of a prescribed width is defined between the outer, distal surface of the mandrel portion  29  and the bottom, innermost surface defined by the recess  27 . 
     The advancement of the mandrel portion  29  into the recess  27  facilitates the concurrent advancement of the jet nozzle  28  through the opening  23 . In this regard, as further seen in  FIG.  4   , in the opening  23  is preferably formed to have a diameter which is only slightly less than that of the base of the jet nozzle  28  which extends to the outer, distal surface of the mandrel portion  29 . This is done so that when the jet nozzle  28  is advanced through the opening  23 , a gas-tight (albeit slidable or rotatable) coupling is formed by the interference between the jet nozzle  28  and the circumferential surface of the base element  18  defining the opening  23 . A similar gas-tight coupling or fit is also preferably achieved between the circumferential outer surface defined by the mandrel portion  29  and the circumferential inner surface defined by the recess  27  when the mandrel portion  29  is advanced into the recess  27 . When the shoulder  40  is abutted against the end surface  42 , the jet nozzle  28 , by virtue of having been advanced through the complementary opening  23 , protrudes into the throat  24  of the base element  18  and is visible within the entrainment port  26 . The aforementioned channel  44  circumvents the base of the jet nozzle  28 . It is contemplated that the opening  23  may be outfitted with a seal, the configuration of which provides for the aforementioned gas-tight coupling of the jet nozzle  28  to the base element  18 , yet allows for the rotation of the jet nozzle  28  within the opening  23  in the event either the rotatable or threadable attachment modes between the base and nozzle elements  18 ,  20  are implemented in the adaptor  12 . 
     In the nozzle element  20 , the jet nozzle  28  and the gas delivery port  32  of the connector  30  collectively define a gas delivery line or lumen  36  which fluidly communicates with the throat  24  of base element  18  when the nozzle element  20  is coupled to the base element  18 . As is also most easily seen in  FIG.  4   , when the nozzle element  20  is connected to the base element  18 , the gas delivery lumen  36  and the throat  24  extend along a common axis A, with the axis of the pressure sensing lumen  25  of the base element  18  extending in spaced, generally parallel relation to such axis A. The gas delivery lumen  36  and the throat  24  collectively define a gas delivery conduit of the adaptor  12 . The gas delivery lumen  36 , and hence the gas delivery conduit, is placeable into fluid communication with the gas delivery lumen of the bi-lumen tube in a manner which will be described in more detail below. 
     As best seen in  FIGS.  4 ,  7  and  8   , the pressure sensing port  34  of the connector  30  partially defines a pressure sensing line or lumen  38  of the nozzle element  20 . That end of the pressure sensing lumen  38  opposite the end defined by the pressure sensing port  34  terminates at the outer, distal surface of the mandrel portion  29 , as seen in  FIG.  8   . When the nozzle element  20  is connected to the base element  18 , the pressure sensing lumen  36  also extends in spaced, generally parallel relation to the axis A, with the pressure sensing lumens  25 ,  38  and intervening channel  44  collectively defining a pressure sensing conduit of the adaptor  12 . Since, as indicated above, the pressure sensing lumen  25  of the base element  18  is formed to fluidly communicate with the recess  27  thereof, such pressure sensing lumen  25  thus fluidly communicates with the channel  44  when the nozzle element  20  is connected to the base element  18 . Similarly, since the channel  44  is annular and circumvents the jet nozzle  28  as indicated above, the pressure sensing lumen  38  is maintained in a constant state of fluid communication with the channel  44 , irrespective of the orientation of the nozzle element  20  relative to the base element  18  if it is rotatably or threadably connected thereto. As such, the integrity of the pressure sensing conduit of the adaptor  12  collectively defined by the pressure sensing lumens  25 ,  38  and intervening channel  44  is not compromised by any rotation of the nozzle element  20  relative to the base element  18  during use of the adaptor  12 , assuming that the nozzle element  20  is not rigidly attached to the base element  18 . Further, irrespective of whether the nozzle element  20  is rigidly, rotatably or threadably connected to the base element  18 , the inclusion of the channel  44  in the pressure sensing conduit allows the pressure sensing lumen  25  to be disposed further radially outward relative to the axis A in comparison to the pressure sensing lumen  38  while being maintained in a constant state of fluid communication therewith by the channel  44 . The pressure sensing lumen  38 , and hence the pressure sensing conduit, is placeable into fluid communication with the pressure sensing lumen of the bi-lumen tube in a manner which will be also described in more detail below. 
     It is contemplated that the adaptor  12  as described above will be integrated into a patient circuit wherein a main delivery tube, and more particularly the aforementioned preferred bi-lumen tube, is used to facilitate the fluid communication between a flow generator or ventilator and the adaptor  12  (and hence the mask  10  coupled to the adaptor). More particularly, the bi-lumen tube is advanced into the recess  31  such that the gas delivery port  32  of the connector  30  is coaxially aligned with an advanced into the gas delivery lumen of the bi-lumen tube. Similarly, the pressure sensing port  34  of the connector  30  is coaxially aligned with and advanced into the pressure sensing lumen of the bi-lumen tube. As will be recognized, is contemplated that the cross-sectional configuration of the gas delivery lumen of the bi-lumen tube will be complementary to the configuration of the gas delivery port  32  of the connector  30  such that the gas delivery port  32  is frictionally maintainable within the gas delivery lumen of the bi-lumen tube upon being advanced therein. Similarly, the cross-sectional configuration of the pressure sensing lumen of the bi-lumen tube will preferably be complementary to the configuration of the pressure sensing port  34  of the connector  30  such that the pressure sensing port  34  is frictionally maintainable within the pressure sensing lumen of the bi-lumen tube upon be advanced therein. Bonding agents such as glue, or other techniques, can also be used to retain the bi-lumen tube within the nozzle element  20 . As is further seen in  FIG.  7   , the distal end portion of the pressure sensing port  34  preferably has a tapered configuration to assist in the advancement thereof into the pressure sensing lumen of the bi-lumen tube. As will be recognized by those of ordinary skill in the art, the advancement of the bi-lumen tube into the recess  31  is limited by the abutment of the corresponding end of such bi-lumen tube against the bottom, innermost surface defined by the recess  31 . 
     In the adaptor  12 , the gas delivery conduit (as defined by the gas delivery lumen  36  through the jet nozzle  28  and the throat  24 ) in combination with the entrainment port  26  creates a jet pump when pressurized gas is introduced into the gas delivery conduit by the bi-lumen tube coupled to the adaptor  12 . In a patient circuit outfitted with the adaptor  12 , is contemplated that such jet pump will be able to generate a maximum pressure of pressure of about 30 cm H2O (and preferably about 20 cm H2O), and a peak flow of about 100 l/min (and preferably 60 l/min). Pressure and flow are generated in a manner wherein a breathable gas (O2, air, or other mixtures of breathable gas) is delivered to the jet nozzle  28  of the jet pump and ambient air is entrained through the entrainment port  26 . The flow of the pressurized gas mixture (including the entrained air) is delivered to the patient through the connector  22  and the mask  10  coupled thereto. The gas exhaled by the patient may be exhausted through the entrainment port  26 . Though not shown in  FIGS.  2 - 8   , is contemplated that a heat and moisture exchange device (HME) and/or an anti-bacterial filter can be connected between the jet pump and the connector portion  16  of the mask  10 . 
     It is contemplated that in the adaptor  12 , the nozzle element  20  can be molded with anyone of a multiplicity of different sizes of the jet nozzle  28  in order to selectively change the performance of the jet pump (e.g., more or less pressure or flow). Further, it is contemplated that the nozzle element  20  may be color-coded so that the user can easily understand the jet pump performance provided thereby. Along these lines, it is further contemplated that the adaptor  12  may be configured such that the nozzle element  20  thereof may be switched out to one having an alternative configuration so as to selectively modify the performance of the adaptor  12 . 
     In the adaptor  12 , the performance of the jet pump is predominately driven by the geometric factors of the size of the jet nozzle  28  (nozzle size), the size of the throat  24  (throat size), and the distance from the distal end of the jet nozzle  28  to the end of the throat  24  as circumvented by the base of the wall  19  disposed furthest from the rim  21  (nozzle-to-throat distance). In the adaptor  12 , it is contemplated that the throat size will be fixed, and that if the base and nozzle elements  18 ,  20  are rigidly or rotatably secured to each other, the nozzle-to-throat distance will be fixed as well. On the other hand, if the base and nozzle elements  18 ,  20  are threadably secured to each other, the nozzle-to-throat distance may be varied to selectively modify the performance characteristics of the jet pump, as will be described in more detail below. However, even the case of a rigid or rotatable connection between the base and nozzle elements  18 ,  20 , the nozzle size may be varied as indicated above, so as to selectively adjust or modify the performance of the jet pump. Along these lines, it is further contemplated that if the base and nozzle elements  18 ,  20  are rigidly or rotatably secured to each other, an even wider range of variation in the jet pump range can be achieved by pairing every nozzle element  12  with a base element  18  in which the throat size and the nozzle-to-throat distance have been designed to optimize performance. However, a similar range of increased performance can also be achieved by only varying nozzle size and having variable jet flow. This is possible when using the adaptor  12  in a non-invasive open ventilation system instead of connecting it to a fixed flow source. Along these lines, the outfitting of the adaptor  12  with the pressure sensing conduit allows for the implementation of the adaptor  12  in, for example, a close pressure loop control with an non-invasive open ventilation system. The range of variability of performance of the jet pump with the jet flow is depicted graphically in  FIG.  9   . The graph is a typical characteristic curve of the jet pump where the curves are parameterized with the jet flow, and demonstrate that increasing the jet flow increases the jet pump performances. The embodiment of the adaptor  12  shown and described above, as well as those embodiments described below, can also be used with a flow regulator instead of within a non-invasive open ventilation system. This practically means that the user will select a fixed flow value for the jet nozzle  28 , with the performances of the jet pump being represented by a single line corresponding to the set jet flow in the graph of  FIG.  9   . 
     Though the structural and functional features of the adaptor  12  as assembled using the attachment mode wherein the base and nozzle elements  18 ,  20  are rigidly secured to each other could be implemented in a unitary construction rather than a two-piece construction, the use of the two-piece construction provides certain manufacturing advantages and economies. More particularly, by having a two-piece construction, a generic base element  18  may be provided, with any one of a multiplicity of nozzle elements  20  each having differently configured jet nozzles  28  being rigidly secured to the base element  18  in the aforementioned manner. As indicated above, the nozzle elements  20  may be color-coded, thus providing a visual indication of the performance features of the adaptor  12  even subsequent to the rigid attachment of the base and nozzle element  18 ,  20  to each other. 
     As indicated above, the base and nozzle elements  18 ,  20  may be threadably secured to each other to allow for selective variations or adjustments in the nozzle-to-throat distance for purposes of modifying the performance characteristics of the jet pump. In this regard, in the threadable connection attachment mode described above, the rotation of the nozzle element  20  in a clockwise direction relative to the base element  18  would effectively shorten the nozzle-to-throat distance. Conversely, the rotation of the nozzle element  20  in a counter-clockwise direction relative to the base element  18  would effectively lengthen the nozzle-to-throat distance. 
     Referring now to  FIG.  10   , there is shown an adaptor  112  constructed in accordance with a second embodiment of the present invention. The adaptor  112  comprises the adaptor  12  shown in  FIGS.  2 - 8    and described above, but enhanced in a manner wherein the jet pump is equipped with an exhalation or anti-asphyxia valve (AAV)  146  in order to reduce the back pressure during exhalation. More particularly, the valve  146  may be used to decrease expiratory pressure in the case when the throat  24  of the jet pump is too small or in case of failure of the ventilator or gas source. 
     In the adaptor  112 , the valve  146  comprises a generally cylindrical, tubular housing  148  which includes at least one, and preferably a pair of exhalation ports  150  formed therein. The housing  148  is attached to the connector  22  of the base element  18 , and is releasably engageable to the connector portion  16  of the mask  10 . The valve  146  further comprises a resilient, conical diaphragm  152  which is disposed within the interior of the housing  148 , and is selectively movable between open and closed positions relative thereto. As seen in  FIG.  10   , the end of the diaphragm  152  of greatest diameter is defined by a radially extending flange portion thereof which is captured between the housing  148  and the distal end or rim of the connector  22  of the base element  18 . 
     When there is positive pressure and flow in the jet pump of the adaptor  112 , the diaphragm  152  is stretched to its closed position to seal against (and thus close or block) the exhalation ports  150  (which are separate from the entrainment port  26 ). Conversely, when the jet pump is not activated (i.e. during exhalation), the diaphragm  152  moves to the open position shown in  FIG.  10   , thus unblocking the exhalation ports  150 . The same function can be achieved thorough the use of a flapper valve as an alternative to the aforementioned diaphragm  152 . 
     Referring now to  FIG.  11   , there is shown an adaptor  212  constructed in accordance with a third embodiment of the present invention. The adaptor  212  comprises the adaptor  12  shown in  FIGS.  2 - 8    and described above, but enhanced in a manner wherein the jet pump is equipped with a exhalation/positive end expiratory pressure (PEEP) valve. More particularly, the jet pump of the adaptor  212  comprises a piloted exhalation valve  246 . 
     The valve  246  comprises a housing  248  which is attached to the connector  20  of the base element  18 . As seen in  FIG.  11   , the housing  248  defines a hollow interior chamber  249  which fluidly communicates with the interior of the connector  20 . The housing  248  has a generally circular cross-sectional configuration, with the interior chamber  249  thereof (when viewed from the perspective shown in  FIG.  11   ) defining a lower section which protrudes from the connector  20  and is of a first diameter, and a distal upper section which is of a second diameter exceeding the first diameter. The lower and upper sections of the interior chamber  249  are separated from each other by a continuous, annular shoulder  250  defined by the housing  248 . 
     Disposed within the upper section of the interior chamber  249  and extending diametrically there across is a resilient diaphragm  252  of the valve  246 . When viewed from the perspective shown in  FIG.  11   , the diaphragm  252  effectively segregates the upper section of the interior chamber  249  into an upper region and a lower region, the lower region extending to the shoulder  250 . The housing  248  includes at least one exhaust port  251  which is formed therein and fluidly communicates with the lower region of the upper section of the interior chamber  249 . The upper region of the upper section of the interior chamber  249  is preferably placed into fluid communication with the gas delivery lumen  36  or the gas delivery lumen of the bi-lumen tube of the exemplary patient circuit including the adaptor  212  via a pressure line  254  extending therebetween. 
     In the valve  246 , the diaphragm  252  is selectively movable between an open position (shown in  FIG.  11   ) and a closed position. When the diaphragm  252  is in its open position, an open fluid flow path between the interior of the connector  20  and ambient air is defined by, in succession, the lower section of the interior chamber  249 , the lower region of the upper section of the interior chamber  249 , and the exhaust port  251  formed in the housing  248 . When the diaphragm  252  is actuated to its closed position, the same is effectively seated and sealed against the shoulder  250  in a manner effectively blocking the exhaust port  251  from fluid communication with the lower section of the interior chamber  249 , and hence the interior of the connector  20 . The valve  246  may further optionally include a spring  256  which is disposed within the upper region of the upper section of the interior chamber  249 , and extends between the approximate center of the diaphragm  252  and a corresponding section of the interior surface of the housing  248 . 
     Due to its inclusion of the diaphragm  252 , the valve  246  of the adaptor  212  can be piloted between on/off states or may be piloted in a proportional fashion to achieve positive end expiratory pressure (PEEP) control by using the pressure in the gas delivery lumen  36  or the gas delivery lumen of the aforementioned bi-lumen tube of the patient circuit that feeds the jet nozzle  28  via the gas delivery lumen  36 . As indicated above, this pressure is delivered is to the valve  246 , and in particular the diaphragm  252  thereof, by the pressure line  254 . In this way, the valve  246  opens and closes in sync with the breathing pattern of the patient. During inhalation, when the jet flow is delivered to the jet pump of the adaptor  212 , the diaphragm  252  of valve  246  is closed by the high pressure in the gas delivery lumen  36  or the gas delivery lumen of the aforementioned bi-lumen tube. During exhalation there is either no flow delivered by the jet nozzle  28  (and hence no pressure in the gas delivery lumen  36 ) and the diaphragm  252  of the valve  246  opens, or a small flow and pressure can be maintained in the gas delivery lumen  36  so that the jet pump can create back pressure in the throat  24  against exhalation and the valve  246  can be servoed with positive pressure to vary the resistance. This latter system results in a controllable PEEP value and requires a careful sizing and matching of the jet pump performances at low flow and the PEEP characteristic of the valve  246 . This is made easier using a closed loop control over the pressure sensed by the pressure sensing lumen of the patient circuit comprising the pressure sensing conduit of the adaptor  212  and the pressure sensing lumen of the bi-lumen tube. The valve  246  can also be used as a PEEP valve by using the spring  256  (if included) to maintain PEEP and the pilot line  254  to facilitate the closure of the diaphragm  252  during inhalation. In this embodiment the PEEP value can be adjusted by changing the pre-load of the spring  254  (e.g., by rotating a portion of the housing  248 ). Optionally, for a better PEEP control, a non-return valve  258  (e.g. an umbrella valve) can be used to close the throat  24  of the jet pump throat during exhalation. As shown in  FIG.  11   , the valve  258  preferably resides within the interior of the connector  22 , and is selectively engageable to the rim  21  of the wall  19  in a manner which will effectively close the corresponding end of the throat  24 . 
     Referring now to  FIG.  12   , there is shown an adaptor  312  constructed in accordance with a fourth embodiment of the present invention. The adaptor  312  also comprises the adaptor  12  shown in  FIGS.  2 - 8    and described above, but enhanced in a manner wherein the jet pump is equipped with a fixed PEEP valve in the shape of, for example, a flapper valve  346  cooperatively engaged to the wall  19  at the rim  21  thereof, and thus disposed at the end of the throat  24 . The flapper valve  346  is normally closed (i.e., rests against the throat  24  of the jet pump, and in particular the rim  21  of the wall  19 ) and opens during inhalation (as shown in  FIG.  12   ) when positive pressure and flow are established by the jet flow coming from the gas delivery lumen  36  via the jet nozzle  28 . The flapper valve  346  also opens in the case of a failure of the source of breathable gas as a result of a negative pressure being established on the patient side of the flapper valve  346  due to the respiratory effort of the patient. During exhalation, the jet flow is suspended and the flapper valve  346  returns in its closed state. The flapper valve  346  preferably includes a plurality of holes or perforations  348  therein to ensure that the exhaled gas can be evacuated to the ambient via the entrainment port  26  by building a back pressure sufficient to maintain PEEP in the patient&#39;s airways. Any one of a range of flapper valves  346  have differing configurations can be selectively used so that different PEEP values can be achieved in the adaptor  312 . Along these lines, color coding can be used to identify the PEEP value corresponding to the particular flapper valve  346  integrated into the adaptor  312 . The perforated flapper valve  346  is just one of several modalities which may be used to achieve the same function. Along these lines, the perforations  348  in the flapper valve  346  could be replaced by grooves on the sealing surface thereof, or grooves formed within the seat of the throat  24 , i.e., the rim  21  which circumvents the distal end of the throat  24 . The same functions may also be achieved by using, for example, and umbrella valve or any other non-return valve having a design which lends itself to the implementation of the working principle exemplified by the adaptor  312 . 
     As indicated above, in each of the above-described embodiments, the jet nozzle  28 , in combination with the throat  24 , the entrainment port  26  and the gas delivery lumen  36 , creates a jet pump within the adaptor  12 ,  112 ,  212 ,  312 . As explained above, the present invention contemplates the use of various techniques to selectively vary the performance attributes of the jet pump as may be need to provide a prescribed therapeutic treatment. However, the jet pump, in any embodiment, is operative to provide a prescribed level of pressure and flow to the mask  10  with the use of a small diameter main gas delivery tube (e.g., the aforementioned bi-lumen tube) within the patient circuit. 
     This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.