Abstract:
A filter adapted to be placed within a distal end of a hose for use in products such as a convective air warming system for a patient to reduce airborne contamination. A method of providing filtered airflow to a coverlet of a convective air warming system that includes installing a filter in a distal end of a hose of the convective warming system.

Description:
TECHNICAL FIELD 
       [0001]    The present invention is related to an air filtration device. More specifically, the present invention relates to a filtration device for a convective air warming system. 
       BACKGROUND 
       [0002]    The link between airborne contamination and surgical site infection (SSI) has been well established in operating theaters. Airborne contamination consists of all particulate matter suspended in the air; common forms include microbial-laden dust, lint, skin squames, and respiratory droplets. These contaminants are mobilized by air currents and can settle out of the air onto the surgical site. Settled contaminants can contribute to SSI through at least two mechanisms: pathogenic contaminants can be the direct cause of SSI; or non-pathogenic contaminants can enable SSI through the forming of a nidus for pathogen growth and attachment. 
         [0003]    Convective patient warming equipment has been identified as both a source and a mobilizer of airborne contamination. Convective patient warming equipment uses an electrically powered blower and heater to supply heated air to an inflatable coverlet that, in turn, distributes the heated air over a patient&#39;s body. The proximity of the coverlet to the surgical site necessitates exhausted air be free of contamination. However, the air intake of the blower is often located near the floor of the operating room, a location that is typically laden with high levels of settled and airborne contamination. To lessen the risk of distributing these contaminants, some manufacturers incorporate a filter on the unit&#39;s air intake. 
         [0004]    As of late, several problems with such intake filtration systems have been identified which can allow viable pathogens to reside within the system and be admitted emitted into the air stream. First, because the intake filter is located on the negative pressure side of the system, contaminants are able to bypass the filter through leaks along the airflow path. Moreover, airborne contamination is generated by moving components within the blower downstream of the filter and emitted into the air stream. In addition, many intake filters comprise a low filtration efficiency media which has been found to provide an inadequate barrier to pathogen ingress. Finally, intake filtration efficiency degrades due to filter media loading and particulate sloughing. 
         [0005]    Attempts to improve filtration in convective warming systems have failed to adequately address the problem of pathogen residence and emission from the hose. Moreover, a practical means for retrofitting existing convective warming equipment which has inadequate filtration has not yet been provided. 
         [0006]    Thus, a need exists for improved filtering of air flowing through convective patient warming equipment help eliminate viable and non-viable residual airborne contamination in an economical manner. Furthermore, a need exists for existing convective patient warming equipment with inadequate filtration to be retrofitted, in an econmical manner, with the improved filtering capabilities. 
       SUMMARY 
       [0007]    Some embodiments of the invention include a filter adapted to be placed within a distal end of a hose. The filter comprises a support body and a filter element. The support body is adapted to engage a cross-section of the hose to secure the filter within the hose. The filter element is supported by the support body. In some embodiments, the filter element has a surface area greater than the cross-section of the hose. In some embodiments, the filter element is adapted to be coupled to the support body such that the filter element covers the cross-section of the hose. 
         [0008]    Some embodiments of the invention include a filter for a convective patient warm air blanket system that includes a warm air blower and an inflatable patient coverlet, a proximal end of a hose connectable to the blower and a distal end of the hose connectable to the coverlet. The filter may include a support body and a filter element. The support body may be adapted to engage the distal end of the hose and to support the filter element. The filter element has a surface area greater than a cross-section of the hose and is adapted to filter substantially all the air passing from the distal end of the hose. 
         [0009]    Some embodiments of the invention include a method of providing filtered airflow to a coverlet of a convective air warming system. The method may include installing a filter in a distal end of a hose of the convective air warming system where the filter includes a filter element coupled about a support body. The method may also include coupling the distal end of the hose to the coverlet causing air to flow within the hose, through the filter, and into the coverlet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
           [0011]      FIG. 1  is a plan view of an exemplary convective air warming system. 
           [0012]      FIG. 2  is a side-sectional view of a distal end hose connector having a filter according to some embodiments of the invention installed therein. 
           [0013]      FIG. 3  is a perspective view of a filter according to some embodiments. 
           [0014]      FIG. 4  is a perspective view of a filter according to some embodiments. 
           [0015]      FIG. 5  is a perspective view of a filter element according to some embodiments. 
           [0016]      FIG. 6  is a bottom plan view of a support body according to some embodiments. 
           [0017]      FIG. 7  is a side plan view of a distal hose end having a filter according to some embodiments installed therein. 
           [0018]      FIG. 8  is a perspective view of a filter according to some embodiments. 
           [0019]      FIG. 9  is a side sectional view of a distal end hose connector having a filter according to some embodiments of the invention installed therein. 
           [0020]      FIG. 10  is a side sectional view of a distal end hose connector having a filter according to some embodiments of the invention installed therein. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. For purposes of this specification and its claims, the term “hose” should be read to include all portions of a hose and any connectors or extenders located at the distal or proximal ends of the hose, even when such connectors are separately and explicitly described. For example, a groove “within a distal hose end connector attached to a hose,” should be considered “within the hose” as well as “within the distal end connector.” 
         [0022]    With reference to  FIG. 1 , there is shown an exemplary convective air warming system  100  typical of a warming system commonly used in a medical setting. Such systems generally include a heater/blower unit  102  coupled in air flow communication with a coverlet  104  by a hose  106 . The hose  106  includes a proximal end  108  coupled to the heater/blower unit  102  and a distal end  110  coupled to the coverlet  104 . As shown, the coverlet  104  can be draped or otherwise positioned on a patient  112  so as to disperse the warm air delivered by the heater/blower unit  102  over desired surfaces of the patient  112 . Generally, the coverlet  104  is a disposable item to be discarded after each use to prevent the passing of contaminants between successive patients. The heater/blower unit  102  and hose  106 , however, are reusable. In view of this, the distal end  110  of the hose  106  includes a distal hose end connector  114  which can easily be inserted and removed from the coverlet  104  at a hose access point to facilitate swapping out of coverlets. 
         [0023]    Certain embodiments of the invention provide a filter adapted to be placed within the distal end  110  of a hose  106 , such as that of  FIG. 1 . By providing a filter within the distal hose end  110  of the convective air warming system  100 , the invention removes contaminants present in the air stream immediately prior to air delivery from the hose  106 . Moreover, it does so without having to provide a large filter surface area in a disposable product, such as the coverlet. In this manner, embodiments of the invention can be used to retro-fit systems currently in use with improved filtration capabilities at a low cost. 
         [0024]      FIG. 2  depicts an embodiment of a filter  200  including a support body  202  and a filter element  204  according to one embodiment installed within a distal hose end connector  114  attached to a hose  106 . The pictured embodiment can be described as a “negative” filter, because the filter element  204  extends proximally within the hose  106 , rather than protruding out of the distal hose opening  206  or residing on the exterior of the hose  106 . In some embodiments, the support body  202  can be a wire or molded plastic piece adapted to perform two functions: to secure the filter  200  to the inside of the distal hose end  106 ; and, to support the filter element  204  in a shape that maximizes filter media surface area and thus minimizes the pressure drop across the filter element  204 . To secure the filter  200  to the inside of the hose  106 , the support body  202  includes a base  208 . In some embodiments, the base  208  can be used to take advantage of an internal groove  210  within the hose connector  114  located between the connector housing  212  and locking piece  214 . Base  208  of the support body  202  can be inserted to reside within this groove  210 , thereby providing a secure placement of the filter  200  within the hose  106 . 
         [0025]    To minimize the pressure drop across the filter element  204 , support body  202  can maintain the filter element  204  in a shape that maximizes active filter media surface area and minimizes filter face air velocity. The combination of airflow rates and distal end hose diameters used in convective patient warming equipment result in un-favorable conditions for the use of an in-line filter element oriented perpendicular to the direction of bulk airflow  216 . Such a combination could result in excessive pressure drops for even low efficiency filtration media. For higher efficiency filtration media, this problem would only be exacerbated. To solve this problem, certain embodiments of the invention present the filter element  204  oriented at an angle relative to the direction of bulk airflow  216 . For example, in the embodiment of  FIG. 2  the filter element  204  is generally conical. Filter element support portion  218  of the support body  202  provides support to the filter element  204  allowing it to maintain this generally conical shape despite the air pressure exerted by the bulk airflow  216  against the proximal end. 
         [0026]    Increasing the surface area of the filter element  204  not only reduces the pressure drop across the filter  200 , but also enables the use of high efficiency filtration media. Thus, some preferred embodiments include a high efficiency depth type filtration media. A depth type media can provide several advantages over a membrane type filtration media. Notably, depth type filter media can provide increased particulate removal efficiency and increased dirt-holding capability at a lower cost than membrane type filters. However, this is not to say that membrane or other types of filtration media are excluded from the scope of the invention. To the contrary, some embodiments include a filter element comprised of such filtration types. 
         [0027]      FIG. 3  depicts a perspective view of an embodiment of a filter  200  such as that of  FIG. 2 . In this view, the filter element  204  has been partially removed from its installed position to reveal features of the support body  202 . In an installed configuration (see e.g.  FIG. 4 ), the distal end  220  of the filter element  204  would be pulled down to the base  208  of the support body  202  to completely enclose a generally conical volume defined by the filter element  204  and the base  208 . Such a filter  200  may then be inserted within a distal hose end to provide filtering of air passing through the hose. This view illustrates, that in some embodiments, the filter element  204  can be a disposable component of the device. Disposable filter elements  200  can increase the economic efficiency of the device by providing for replacement of only the filter element  204  portion of the filter and reuse of the support body. 
         [0028]    Although, as discussed above, a range of filter element  204  designs and construction techniques are within the scope of the invention, embodiments that form a sock-like shape may have certain ease of use and cost saving advantages. For example, the conical filter element  204  of  FIGS. 3 and 4  can comprise flexible, or semi-rigid filter media die cut from a sheet and joined at a seam  222  by heat seal, adhesive, sewing, or other connection means. In some embodiments, a preferred material for a filter media of this arrangement is Technostat® available from Hollingsworth &amp; Vose Company of East Walpole, Mass. Moreover, in some embodiments, the filter element  204  can include an elastic band  224  or other attachment mechanism at its distal end  220 . This attachment mechanism can secure the filter element  204  to the support body  202  by, for example, cinching the distal end  220  about the base  208  as in  FIG. 4 . Other examples of an attachment mechanism can include snaps, hook-and-loop connector systems, adhesives, pins, staples, and any other suitable connector. Another embodiment of a filter element  204  is shown in  FIG. 5 . In this embodiment, the filter element  204  is generally conical having a plurality of pleats  226  about the surface of the filter media. Pleats  226  can be incorporated into a filter element of any shape and can provide an increased filter media surface area to increase filtration efficiency. Additionally, the embodiment of  FIG. 5  shows a string  228  passing through the filter media around the distal end  220 . String  228  represents yet another example of an attachment mechanism and can be drawn tight to secure the filter element  204  about a support body. 
         [0029]    Referring back to  FIG. 3 , support body  202  can comprise numerous variations. In many embodiments, the support body  202  includes a base  208  and a filter element support portion  218 . The base  208  can be generally ring-shaped and can be adapted to engage a cross-section of a hose. As described above, the base  208  can be adapted to fit within a groove in a distal hose end connector or some other portion of the hose. Alternatively, for example, the base can be sized slightly larger than the cross-section of hose such that when the support body is inserted therein, it exerts pressure radially outward toward the hose wall, thereby frictionally engaging the hose. In other embodiments, a hose engaging mechanism may extend from the base to couple with the hose or receiving mechanisms placed thereon. In still further embodiments, the base may not be ring-shaped, but can instead be semi-circular, squared, or otherwise shaped. In the embodiment of  FIG. 3 , base  208  is a coil of metal wire, having an overlap portion  230 . A coiled base can provide for compressibility of the base which can facilitate insertion into the hose. In other embodiments, the base may be a solid ring made of a molded plastic, metal, rubber, or other suitable material. In a preferred embodiment, the base is made of spring steel wire of a diameter of about 0.100 inches formed into a coiled ring having a diameter of approximately 1.5-2.5 inches. It should be apparent that the design of the support body  202  and its attachment features allow for easy placement of the filter  200  into nearly all distal hose end designs currently in clinical use. As such, embodiments of the invention can provide an easy and reliable means for retrofitting existing convective patent warming equipment with adequate filtration. 
         [0030]    The support body  202  of  FIG. 3  further includes a filter element support portion  218  coupled to the base  208 . As described above, because negative filters extend proximally within the hose in opposition to the direction of bulk airflow, support may need to be provided to the filter element to keep it from collapsing due to airflow pressure. In this embodiment, the filter element support  218  is a rigid, inverse “V”-shaped wire, coupled to the base  208  at attachment points  232 . In large part, the design of the filter element support portion  218  depends on the shape of the filter element  204  being used. An inverse “V” shape is appropriate for use with a conical filter element  204  because this shape provides lateral support to the conical surface from base to peak with minimal obstruction of airflow through the filter  200 . Many other designs too numerous to mention can provide similar and adequate functionality to the “V” shaped exemplary embodiment pictured and such other designs may vary depending upon the type of filter element used. Attaching the filter element support portion  218  can be accomplished by any suitable means such as, for example, welding, adhesive bonding, stapling, or other attachment mechanisms. In some embodiments, the filter element support portion  218  and base  208  can comprise one solid piece, such as for example, a single molded piece of plastic, or a single bent wire. 
         [0031]    In many applications, the distal end of a hose used in convective air warming systems must be flexible. Often, due to the positioning of the coverlet and its air inlet, the hose must be able to make a sharp bend within  6  inches of the distal end. To accommodate this flexibility, many embodiments of the distal hose end filter  200  include a flexible filter element  204  and filter element support portion  218 . For example, a negative filter may include a “V”-shaped filter element support portion comprising a flexible metal wire, such as for example spring steel, so that the point of the “V” may flex out of plane. 
         [0032]    In some embodiments, the support body  202  can include a deformation mechanism to aid in temporarily deforming at least a portion of the support body to facilitate insertion of the filter into a hose. For example,  FIG. 6  shows a bottom plan view of a support body  202  including a deformation mechanism according to some embodiments. Here, the metal wire comprising the base  208  has been bent three times near each end to provide first and second handles  234 ,  236 . A user installing the support body  202  within a hose, can apply pressure at each handle  234 ,  235  causing the first handle  234  to move toward the second handle  236  and the base  208  to flex about a flex point  238  generally opposite the handles  234 ,  236 . This flexing causes the diameter of the base  208  to compress to a suitable diameter for insertion into a hose. One having ordinary skill in the art can appreciate many variations of the described deformation mechanism. For example, a separate handle piece could be welded or otherwise attached to the base to provide a grip for compressing the diameter of the support body. Alternatively, the filter element support portion can, in some embodiments, include attached squeeze points or be used as squeeze points for temporarily deforming the support body. Moreover, a deformation mechanism can extend from the support body in any direction and need not reside within the plane of the base as shown in the embodiment of  FIG. 6 . 
         [0033]      FIG. 7  shows how a filter  200  may be installed according to embodiments of the invention. Here, a hose  106  having a distal end connector  114  is shown. A filter  200  according to one embodiment, is being inserted into the distal opening  206  of the hose  106  in a negative orientation, i.e. so that the filter element  204  remains entirely within the hose  106 . In many embodiments the base  208  of the filter  200  is slightly larger than the distal opening  206  to allow the filter  200  to be secured within the hose  106  as discussed above. To fit the wider base  208  past the narrower distal opening  206 , a user can first compress the base  208  of this embodiment by squeezing according to arrows A. Other filter embodiments may be sized so that no compression is necessary, or may include another deformation mechanism (e.g. the handles  234 ,  236  of  FIG. 6 ). The filter  200  can then be inserted into position within the hose according to arrow B, for example to the position shown in  FIG. 2 . 
         [0034]    In an alternative embodiment, which can be seen by reference to  FIGS. 8 and 9 , the filter  300  comprises a tubular support body  302  having a filter element  304  disposed within. Tubular support body  302  can include a snap ring  306  for securing the filter  300  within the hose  106 , for example in the groove  210  defined by the locking piece  214  and connector housing  212  of a distal hose end connector  114 . A removal tab  308  or other removal mechanism can be coupled to the snap ring  306 . In one embodiment, the removal tab  308  can provide a means for the user to grip the tubular support body and facilitate removal through allowing the application of sufficient force to expand the distal hose end lip  312  by contact with the groove  210 . In another embodiment, pressing upon the removal tab  308  can provide at least partial retraction of the snap ring  306  within the support body  302 , thereby allowing an installed filter  300  to slide through the distal hose opening  206  and be removed from the hose  106 . In such embodiments, the support body  302  can comprise a generally rigid molded plastic or metal tube. A filter element  304  such as one of those described above, may be fixedly coupled to the support body  302  by any suitable means, such as for example, adhesive bonding. Some embodiments further include a filter element support portion  310  within the support body  302  distally positioned relative to the filter element  304 . A filter element support portion  310  can be functionally and structurally similar to the filter element support portion discussed above in reference to other embodiments. Here, the filter element support portion  310  can comprise a metal wire or other component installed within the tubular support body  302 , or may comprise a molded plastic formed in the same process used to mold the support body. 
         [0035]    In yet another embodiment, a filter  400  according to the invention can include a filter element  402  configured to protrude from the distal hose opening  206 . Such an embodiment can be seen in  FIG. 10 . Embodiments including a “positive” filter element  402  can include a support body  404  having a filter element  402  permanently attached thereto. The support body  404  can be of any construction and include variations according to the support body designs discussed above. For example, a suitable support body may comprise a metal wire ring such as the base  208  of support body  202  in  FIG. 3 . The embodiment of  FIG. 10  depicts a filter  400  including a tubular support body  404  similar to that of  FIG. 8 . Tubular support body  404  can comprise a molded plastic and include a snap ring  406  and removal tab  408  for locking the filter  400  in place within a hose, for example in the groove  210  defined by the locking piece  214  and connector housing  212  of a distal hose end connector  114 . 
         [0036]    Filter element  402  can comprise a high efficiency depth filter material as described above. In a positive filter arrangement however, the filter surface area is not maximized by maintaining the filter in a particular arrangement. Rather, the filter element  402  is designed to expand under the pressure of bulk airflow  410 . To this end, a pliable filter element material is desirable because a rigid filter element may not expand properly to present an appropriately sized filter surface area. In use, an appropriately expanded filter element  402  presents a filter element  402  having an inflated shape external of the hose  106 . This inflated shape can assume any number of designs, for example, a bulb shape (as seen in  FIG. 10 ), a skirt shape, a “T”-shape, or any number of other designs, each providing a large filter media surface area through which airflow  410  from the hose  106  must pass before entering the coverlet  104 . Prior to installation in a hose, the filter element  402  can be balled-up, folded, wound, or otherwise stowed within the support body  404  so the filter element  402  is not torn or damaged. Pressure from bulk air flow  410  can cause a stowed filter element  402  to expand to the inflated configuration seen in  FIG. 10 . Following use, the filter  400  may be disposed of with the coverlet  104 , or may be reused. 
         [0037]    In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention.