Self-sealing Pressurized Limb Enclosure

Abstract

Method and system are provided for creating a self-sealing pressurized limb enclosure for the assessment of pressure effects on the limb. Embodiments can be self-sealing in that the seal is created by the positive pressure in the enclosure relative to the external environment and does not necessitate contact pressure at the seal location that exceeds the pressure in the enclosure. The seal accounts for anatomical size differences as well as deformations in the size and shape of the limb due to pressure. Furthermore, the seal maintains function in the presence of skin and tissue movement. In operation, the system can be used by an individual without external assistance.

We claim: 
     
         1 . A limb seal apparatus for use with a pressurizable enclosure, comprising a limb engagement system that allows a limb to pass therethrough, wherein the limb engagement system changes its physical configuration to create an air flow restriction responsive to a pressure gradient between the inside and outside of the enclosure, wherein the air flow restriction is sufficient to result in transmural pressure of zero in the veins of a limb passing through the limb engagement system into the enclosure. 
     
     
         2 . A limb seal apparatus as in  claim 1 , wherein the limb engagement system comprises a flexible sleeve. 
     
     
         3 . A limb seal apparatus as in  claim 2 , wherein sleeve mounts with the enclosure with a gap between an opening in the enclosure and the limb, and wherein the force due to friction between the seal and the limb when the enclosure is pressurized plus the sleeve's resistance to axial deformation is at least equal to the force on the seal due to pressure on the gap at pressures above a first predetermined threshold. 
     
     
         4 . A limb seal apparatus as in  claim 3 , wherein the force due to friction between the seal and the limb when the enclosure is pressurized plus the sleeve's resistance to axial deformation is less than the force on the seal due to pressure on the gap at pressures below a second predetermined threshold. 
     
     
         5 . A limb seal apparatus as in  claim 2 , configured to mount with an opening in a pressurizable enclosure, wherein the sleeve is configured to sealingly engage the pressurizable enclosure at the opening, wherein the sleeve has a length sufficient to engage the opening and to extend a distance along a limb within the enclosure, and allow the distal end of the limb to extend into the enclosure without exerting pressure above a predetermined threshold on the limb when the enclosure is not pressurized relative to ambient, wherein the sleeve is flexible enough to sealingly engage the surface of the limb when the enclosure is pressurized above ambient. 
     
     
         6 . A limb seal apparatus as in  claim 1 , wherein the limb engagement system comprises a closure for an opening into the pressurizable enclosure, wherein the closure is configurable to a first size that allows ingress of a limb into the enclosure, and configurable to a second size that matches the outer shape of the limb closely enough to provide the air flow restriction. 
     
     
         7 . A limb seal apparatus as in  claim 6 , comprising a continuously variable aperture providing an adjustable opening by adjustment of the aperture. 
     
     
         8 . A limb seal apparatus as in  claim 6 , comprising a plurality of overlapping leaves, flexibly mounted with the pressurizable enclosure such that the leaves accommodate ingress of a limb into the volume, and overlap to provide a reduced opening that approximates the size of a limb placed within the overlapping leaves. 
     
     
         9 . A limb seal apparatus as in  claim 1 , wherein the limb engagement system comprises a circulate ring of fibers comprising multiple overlapping fibers that allow entrance of the limb into the pressurizable enclosure through the fibers and that together provide air resistance, wherein the fibers have longitudinal stiffness so as to oppose pressure forces from within the pressurizable enclosure, and radial flexibility to allow entrance of the limb into the enclosure and radial flexibility to allow the fibers to form a seal about the arm when the pressure in the enclosure is above ambient. 
     
     
         10 . A limb seal apparatus as in  claim 2  where the seal changes its physical configuration to obtain a non-positive angular progression configuration at pressures less than 30 cm H20. 
     
     
         11 . A limb seal apparatus as in  claim 2  where the sleeve does not exert pressure above a predetermined threshold when the enclosure is pressurized above ambient. 
     
     
         12 . A limb seal apparatus as in  claim 2  wherein the flexible sleeve is attached to the enclosure and is subject to increasing axial tension due to increasing pressure. 
     
     
         13 . A limb seal apparatus as in  claim 2  wherein the sleeve has a proximal attachment to an aperture allowing access to the interior of the enclosure, and a distal aperture that circumferentially encloses the limb, wherein the sleeve's change in physical configuration are responsive to pressure increases in the enclosure causing the portions of the distal sleeve to compress against the limb while elements of the sleeve in proximity of the aperture experience axial tension. 
     
     
         14 . A limb seal apparatus as in  claim 2 , wherein the sleeve comprises an air resistant material with asymmetric material properties, in a configuration such that the material's resistance to compression is greater aligned with the axis of the limb than orthogonal to the axis of the limb. 
     
     
         15 . A limb seal apparatus as in  claim 2 , wherein the sleeve further comprises a plurality of battens, each batten being stiff in the axial direction, mounted with the sleeve such that the battens resist deformation of the sleeve out of the enclosure. 
     
     
         16 . A limb seal apparatus as in  claim 2 , wherein the sleeve has a rigidity that is greater near the engagement with the opening than distal from the engagement with the opening. 
     
     
         17 . A limb seal apparatus as in  claim 16 , wherein the sleeve has a rigidity that smoothly decreases from the engagement with the opening to a region distal from the engagement with the opening. 
     
     
         18 . A limb seal apparatus as in  claim 16 , wherein the sleeve's thickness, material composition, density, or a combination thereof, changes from a region near the engagement with the opening to a region distal from the engagement with the opening. 
     
     
         19 . A limb seal apparatus as in  claim 2 , wherein the sleeve is configured with accordion folds and has resistance to folding such that pressure above ambient in the volume compresses the accordion folds. 
     
     
         20 . A limb seal apparatus as in  claim 19 , wherein the sleeve material has a low coefficient of friction with the surface of the limb. 
     
     
         21 . A limb seal apparatus as in  claim 19 , wherein the sleeve accordion folds compress at a lower pressure than the sleeve compresses to sealingly engage the limb. 
     
     
         22 . A pressure management system, comprising a pressurizable enclosure and a sealing apparatus as in  claim 1 . 
     
     
         23 . A medical instrument configured to measure a limb in a pressure condition above ambient, comprising a pressure management system as in  claim 22 , and a measurement system mounted with the pressure management system to measure a portion of the limb within the pressure management system. 
     
     
         24 . A limb seal apparatus as in  claim 1 , further comprising one or more pressure sensors, contact sensors, or both, mounted with the limb engagement system.