Abstract:
A respiratory effort sensing belt that incorporates a PVDF transducer is constructed such that the transducer is contained within an elastic, moisture impervious plastic envelope and affixed to the envelope are a pair of cam buckles adapted to receive opposed ends of a body-encircling, single-use band. Because of the construction of the sensor module, it may be sterilized for reuse.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    None 
       BACKGROUND OF THE INVENTION 
       [0002]    I. Field of the Invention 
         [0003]    This invention relates generally to apparatus for monitoring respiratory activity in the course of a sleep study and more particularly to a respiratory effort sensor designed such that the sensor electronics and associated leads for connecting the electronics to a polysomnograph machine (PSG) is adapted for connection to a body-encircling band and remains reusable and only the low-cost, body-encircling band position is disposable following a use thereof. 
         [0004]    II. Discussion of the Prior Art 
         [0005]    In published U.S. Application 2008/0275356, there is described a respiratory effort belt that has been marketed by Dymedix Corporation of Shoreview, Minn. for a number of years. It comprises a PVDF film member having first and second metalized major surfaces to which a pair of approximately six foot long tabbed leads is electrically connected. The resulting assembly is permanently affixed to the surface of a body-encircling belt member. Signals are generated when the PVDF film on the belt member is stressed due to stretching as the user breathes in and out. The leads connect to a PSG, allowing the signals to be used in diagnosis and analysis. 
         [0006]    Approximately 95% of the manufacturing cost of the respiratory effort belt resides in its sensor electronics and associated leads while the remaining 5% of the cost resides in the body-encircling belt on which the sensor electronics are affixed. 
         [0007]    For hygienic reasons, most hospital sleep labs dispose of the respiratory effort belts after a use on a given patient. It is, of course, advantageous to reduce the cost of the diagnostic procedure and the present invention achieves this desired result. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with the present invention, there is provided a respiratory effort belt comprising a PVDF film strip having a layer of metallization on opposed major surfaces thereof. First and second insulated conductive leads, each with first and second ends, have the first end of the first lead electrically connected to the layer of metallization on one of the opposed major surfaces and the second lead electrically connected to the layer of metallization on another of the opposed major surfaces. A flexible, elastic, moisture impervious, generally rectangular envelope is made to contain the metalized PVDF film strip and only a distal end portion of the first and second conductive leads. A pair of connectors is releasably attached individually to the first and second ends of the envelope. A disposable elastic or inelastic band, whose length is sufficient to encircle a human&#39;s torso, is adapted to be selectively joined and released to and from the pair of connectors. This allows the band to be disposed of after use while the envelope, with its connectors and containing the sensor element and leads, remains reusable following sterilization. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals in the several views refer to corresponding parts. 
           [0010]      FIG. 1  is a partial frontal view of a respiratory effort belt comprising a preferred embodiment of the present invention; and 
           [0011]      FIG. 2  is an exploded view of the reusable sensor module. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    This description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top” and “bottom” as well as derivatives thereof (e.g., “horizontally”, “downwardly”, “upwardly”, etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “connected”, “connecting”, “attached”, “attaching”, “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece, unless expressively described otherwise. 
         [0013]    Referring first to  FIG. 1 , there is indicated generally by numeral  10  a respiratory effort belt constructed in accordance with the present invention. It is seen to comprise a reusable, sterilizable sensor module  12 , the construction of which is best illustrated in the exploded view of  FIG. 2 . In  FIG. 2 , a strip of polyvinylidine fluoride (PVDF) is identified by numeral  14 . The strip is generally rectangular and deposited on the opposed major surfaces thereof are metallization layers  16  and  18 . An electrical lead  20  has a conductive terminal pad  22  bonded to the metallization layer  16  by a conductive adhesive member  24 . Likewise, an electrical lead  26  has its conductive terminal pad  28  conductively affixed to the metallization layer  18  by means of a conductive adhesive layer  30 . 
         [0014]    The PVDF film  14 , as well as distal end portions of the leads  20  and  26 , is contained within a moisture impervious plastic envelope comprising elastic polymer layers  32  and  34  that are laminated together about the perimeters thereof to form the envelope. 
         [0015]    Without limitation, the resulting module  12  may be about 5 inches in length and about 1½ inches in width. 
         [0016]    Referring again to  FIG. 1 , affixed to the end portions  36  and  38  of the envelope comprising the module  12  are connectors  40  and  42  that are used to releasably couple the module  12  to a body-encircling band  44 . Without limitation, the connectors  40  and  42  preferably comprise cam buckles, many types of which are commercially available. Such cam buckles releasably clamp to the opposed ends  36  and  38  of the envelope comprising the module  12  and permit adjustment of the body-encircling band  44  to a desired degree of snugness. 
         [0017]    It is contemplated that the body-encircling band  44  be of an inexpensive cloth fabric that is relatively inelastic. 
         [0018]    In use, the respiratory effort belt  10  will be placed about a patient&#39;s torso, either about the chest or abdomen, and any slack taken up by tensioning the band with the cam buckle  40  or  42  open and when the tension is deemed appropriate, the cam lever is released, locking the band  44  from moving relative to the module  12 . As the subject breathes, the envelope comprising the sensor module  12 , being elastic, will stretch upon inspiration and shrink during expiration. This places corresponding stresses on the PVDF film element  14  thereby producing, via the piezoelectric effect, electrical output signals on the leads  20  and  26 . 
         [0019]    Upon completion of a patient&#39;s sleep study, the body-encircling band  44  can be separated from the buckles  40  and  42  and properly disposed of. The module  12 , however, can be retained for reuse following sterilization and/or cleaning and only the relatively inexpensive band  44  needs replacement. In that the great majority of the cost resides in the module  12  and because this module is reusable, a substantial savings results for the consumer who need only replace the fabric belt  44  and not the entire respiratory effort belt each time the belt is used. 
         [0020]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices. Also, various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.