Abstract:
A heat and moisture exchange unit for use with a patient breathing circuit. The unit includes a housing, an MDI port assembly and a heat and moisturizing medium. The housing forms a patient-side port, a ventilator-side port, and a containment region between the patient-side port and the ventilator-side port. The MDI port assembly includes a frame projecting into the containment region and configured to receive a portion of a metered dose dispenser. The frame terminates at an outlet end, forming a flow passage. The heat and moisturizing medium is maintained within the containment region so as to define a medium face most proximate the outlet end of the MDI port assembly. The unit is characterized by the absence of a body between the outlet end and the medium face.

Description:
FIELD 
       [0001]    The present disclosure relates generally to components for a patient breathing circuit. More particularly, the present disclosure relates to a heat and moisture exchange (“HME”) unit useful with a patient breathing circuit. 
       BACKGROUND 
       [0002]    The use of ventilators and breathing circuits to assist in patient breathing is well known in the art. The ventilator and breathing circuit provides mechanical assistance to patients who are having difficulty breathing on their own. During surgery and other medical procedures, the patient is often connected to a ventilator to provide respiratory gases to the patient. One disadvantage of such breathing circuits is that the delivered air does not have a humidity level and/or temperature appropriate for the patient&#39;s lungs. 
         [0003]    To provide air with desired humidity and/or temperature to the patient, an HME unit can be fluidly connected to the breathing circuit. As a point of reference, HME is a generic term, and can include simple condenser humidifiers, hygroscopic condenser humidifiers, hydrophobic condenser humidifiers, etc. 
         [0004]    In general terms, HME units consist of a housing that contains a layer of heat and moisture retaining media or material (“HM media”). The HM media has the capacity to retain moisture and heat from the air that is exhaled from the patient&#39;s lungs, and then transfer the captured moisture and heat to the ventilator-provided air of the inhaled breath. The HM media can be formed of foam, paper or other suitable materials that are untreated or treated, for example, with hygroscopic material. 
         [0005]    While the HME unit addresses the heat and humidity concerns associated with ventilator-provided air in the breathing circuit, other drawbacks may exist. For example, it is fairly common to introduce aerosolized medication particles into the breathing circuit (e.g., via a nebulizer) for delivery to the patient&#39;s lungs. However, where an HME unit is present in the breathing circuit, the medication particles will not readily traverse the HM media and thus not be delivered to the patient. 
         [0006]    In addition, the HM media can become clogged with the droplets of liquid medication, in some instances leading to an elevated resistance of the HME unit. One approach for addressing these concerns is to remove the HME unit from the breathing circuit when introducing aerosolized medication. This step is time consuming, subject to errors and can result in the loss of recruited lung volume when the circuit is depressurized. 
         [0007]    Alternatively, various HME units have been suggested that incorporate intricate bypass structures/valves that selectively and completely isolate the HM media from the airflow path. For example, existing bypass-type HME units employ a bypass structure that is internal or through the HM media. While viable, these and other bypass-type HME units are difficult to operate (e.g., requiring a caregiver to rotate two frictionally fitting housing units relatively to each other) and/or are relatively complex and thus expensive. 
         [0008]    In light of the above, a need exists for improved HME units having an HM media bypass feature that addresses one or more of the problems associated with conventional bypass-type HME units. 
       SUMMARY 
       [0009]    Some aspects of the present disclosure relate to a heat and moisture exchange unit for use with a patient breathing circuit. The unit includes a housing, an MDI port assembly and a heat and moisture medium. The housing forms a patient-side port, a ventilator-side port, and a containment region between the patient-side port and the ventilator-side port. 
         [0010]    The MDI port assembly includes a frame projecting into the containment region and configured to receive a portion of a metered dose dispenser. The frame terminates at an outlet end, forming a flow passage. The heat and moisturizing medium is maintained within the containment region to define a medium face most proximate the outlet end of the MDI port assembly. The unit is characterized by the absence of a body between the outlet end and the medium face in some embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. 
           [0012]      FIG. 1  is a simplified illustration of an example patient breathing circuit with which an HME unit in accordance with principles of the present disclosure is useful. 
           [0013]      FIG. 2  is a simplified illustration of another example breathing circuit with which the HME unit in accordance with principles of the present disclosure is useful. 
           [0014]      FIG. 3  is a perspective view of an HME unit for use in conjunction with an embodiment of the present disclosure. 
           [0015]      FIG. 4  is a top view of the HME unit. 
           [0016]      FIG. 5  is a bottom view of the HME unit. 
           [0017]      FIG. 6  is a side view of the HME unit. 
           [0018]      FIG. 7  is a first end view of the HME unit. 
           [0019]      FIG. 8  is a second end view of the HME unit. 
           [0020]      FIG. 9  is a sectional view of the HME unit taken along a line A-A in  FIG. 4 . 
           [0021]      FIG. 10  is sectional view of the HME unit taken along a line B-B in  FIG. 6 . 
           [0022]      FIG. 11  is an angled end view of the HME unit taken along a line C-C in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. 
         [0024]    As illustrated in detail below, aspects in accordance with principles of the invention relate to an HME unit or apparatus useful with a patient breathing circuit. As a point of reference,  FIG. 1  illustrates one such breathing circuit  10  as including a number of flexible tubing segments that are connected in between a patient  12  and a ventilator (not shown). The breathing circuit  10  of  FIG. 1  is a dual limb breathing circuit, and can include a source of pressurized air  14 , an HME unit  16  (shown in block form) in accordance with the present disclosure, and a nebulizer  18 . 
         [0025]    With the one non-limiting example of the breathing circuit  10  in mind, a patient tube  20  is provided that connects the patient  12  to the HME unit  16 . An end of the patient tube  20  that interfaces with the patient  12  can be an endotracheal tube that extends through the patient&#39;s mouth and throat and into the patient&#39;s lungs. Alternatively, it also may be connected to a tracheostomy tube (not shown in  FIG. 1 , but referenced at  46  in  FIG. 2 ) that provides air to the patient&#39;s throat and thereby to the patient&#39;s lungs. 
         [0026]    Extending on an opposite side of the HME unit  16  is a connector  22 , for example a Y-connector. The Y-connector  22  can be connected to additional tubing; for example, an exhalation tube  24  (commonly referred to as the “exhalation limb”) that allows exhaled air to leave the breathing circuit  10 . A second tube  26  (commonly referred to as the “inhalation limb”) is connected to a ventilator (not shown). 
         [0027]    By way of further reference,  FIG. 2  illustrates an alternative breathing circuit  40  with which the HME unit  16  of the present disclosure is useful. The breathing circuit  40  is a single limb breathing circuit that again serves to fluidly connect a ventilator (not shown) with the patient  12 . 
         [0028]    With the single limb breathing circuit  40 , the patient tube  20  fluidly connects the patient  12  and the HME unit  16 . A single tube  42  extends from the HME unit  16  opposite the patient  12 . The ventilator (not shown) is directly connected to the HME unit  16  via a tube  42 . When desired, the single limb breathing circuit  40  (as well as the dual limb breathing circuit  10  of  FIG. 1 ) can be connected to a tracheostomy tube  46 . 
         [0029]    With the above general explanation of breathing circuits in mind, one configuration of an HME unit  50  useful as the HME unit  16  ( FIGS. 1 and 2 ) is illustrated in  FIGS. 3-11 . The HME unit  50  includes a housing  52 , a heat and moisture media (HM media)  54  and an MDI port  56 . Details on the various components are provided below. In general terms, however, the housing  52  includes a first port  58 , a second port  60  and an intermediate section  62 . 
         [0030]    The HM media  54  is sized and shaped for placement within a containment region of the intermediate section  62 . In this regard, the HM media  54  can assume a variety of forms known in the art that provide heat and moisture retention characteristics, and typically is or includes a foam material. Other configurations are also acceptable, such as paper or filler-type bodies. In more general terms, then, the HM media  54  can be any material capable of retaining heat and moisture regardless of whether such material is employed for other functions such as filtering particles. 
         [0031]    With some constructions, the HM media  54  has a generally rectangular shape, defining opposing, first and second major surfaces  70 ,  72 . Upon final assembly, the HM media  54  is arranged such that the first major surface  70  fluidly faces the first port  58 , whereas the second major face  72  fluidly faces the second port  60 . 
         [0032]    The configuration of the HME unit  50  may facilitate detaching the first port  58  from the second port  60  to replace the HM media  54 . Alternatively, the HME unit  50  may be configured such that the entire unit is replaced if the HM media  54  becomes fouled or otherwise unusable. 
         [0033]    As illustrated in  FIG. 9 , the HM unit  50  thereby orients the HM media  54  such that a relatively large HM media surface area (i.e., the first or second major surface  70 ,  72 ) is presented within a first flow path A, yet overt airflow restrictions are minimized. More particularly, flow along the first airflow path A progresses through a thickness of the HM media  54 , where the thickness may be less than a length or width of the HM media  54 . As such, resistance to normal patient breathing through the HME unit  50  is minimized. 
         [0034]    An optional filter  64  may be included with the HME unit  50  to remove particles that may foul or otherwise decrease the performance or life span of the HM media  54 . The filter  64  may be positioned in the containment region  62  adjacent the second major face  72  such that the filter  64  is fluidly open to the ventilator-side port. As a point of reference, with embodiments in which the HME unit  50  does not include the optional filter  64 , the containment region  62  can have a volume of not more than 30 mL in some embodiments; alternatively, with constructions including the filter  64 , the containment region  62  can have a volume of not more than 60 mL. 
         [0035]    The MDI port assembly  56  includes a frame  80  that projects into the containment region  62 , as illustrated in  FIGS. 9-11 . The MDI port assembly  56  is adapted to receive a portion of a metered dose dispenser (not shown). The frame terminates at an outlet end  82 , forming a flow passage  84 . The size and shape of the flow passage  84  may be varied, depending on the material being dosed through the MDI port assembly  56 . The outlet end  82  is between the first port  58  and the first major surface  70 . A distance between the outlet end  82  and the medium face  70  is not greater than about 0.5 inches. 
         [0036]    When it is not desired to use the nebulizer  14 , it is possible to disconnect the nebulizer  14  from the MDI port  56  and then insert a plug (not shown) into the MDI port  56  to thereby enable the patient breathing circuit  10 ,  40  to be pressurized as well as to prevent pathogens or other objects from entering the breathing circuit  10 ,  40 . 
         [0037]    The HME unit  50  may also include a resistance indicator (not shown). The resistance indicator can assume a variety of forms, and generally serves to identify instances where a differential pressure or resistance across the HME unit  50  has exceeded a predetermined value. 
         [0038]    The resistance indicator is in fluid communication with the second port  60  along the first flow path A, and is thus exposed to an internal pressure differential within the HME unit  50  across the HM media  54 . The resistance indicator can be mechanical (e.g., silicone diaphragm) and/or incorporate electronic components. 
         [0039]    When triggered (i.e., in the presence of an excessive pressure differential across the HM media  54 ), the resistance indicator provides a warning or other indication to a caregiver of a potentially problematic state of the HME unit  50  (e.g., the HM media  54  is overly resisting airflow). 
         [0040]    In this regard, where the resistance indicator is internally disposed within the housing  52 , one or more exterior walls associated with the housing  52  and located in close proximity to the resistance indicator can be at least partially transparent such that the resistance indicator is viewable through the housing  52 . 
         [0041]    During use, the HME unit  50  is fluidly connected to a patient breathing circuit; for example, the breathing circuit  10  of  FIG. 1  or the breathing circuit  40  of  FIG. 2 . The patient tube  20  is fluidly connected to the first port  58 , and the second port  60  is fluidly connected to tubing connected to the ventilator (not shown). Thus, the first port  58  serves as a patient side port and the second port  60  serves as a ventilator side port. 
         [0042]    Thus, airflow to and from the patient  12  via the HME unit  50  must pass through the HM media  54  (as well as the optional secondary filter  50  where provided), with the HM media  54  absorbing moisture and heat from exhaled air, and then transferring moisture and heat to the inhaled air provided to the patient&#39;s lungs. 
         [0043]    It is contemplated that features disclosed in this application, as well as those described in the above applications incorporated by reference, can be mixed and matched to suit particular circumstances. Various other modifications and changes will be apparent to those of ordinary skill.