Abstract:
An improved manifold assembly useful in patient ventilation/aspiration systems includes a stop cock valve with a hollow stem and a transverse port arranged to permit the stem to be rotated between open and closed positions. In both positions, a ventilating pathway is maintained through the stem between ventilator and patient connection ports of the manifold. In the open position the stem provides a travel pathway for a catheter between the patient connection port and an access port of the manifold. In the closed condition, the stem seals this travel pathway. The improvement provides an arrangement of structure operable to resist imparting shear damage to an inserted catheter, and to provide enhanced feedback to an attendant, as the stem is manually rotated into contact with the catheter.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to valved manifold devices of the type used at the patient intubation interface of neonatal endotracheal ventilation/aspiration systems. It is specifically directed to an improved valve stem interface structured to protect against accidental shearing of fragile aspiration catheters positioned within such manifolds. 
   2. State of the Art 
   Many gas delivery systems, particularly in a hospital or laboratory environment, utilize manifold devices for directing fluid flow. There is a variety of circumstances in which it is necessary or desirable to provide multiple, yet isolated, other path ways through the interior of such a manifold. The manifold is often associated with other components as a system. 
   As an example, closed systems for endotracheal suctioning and ventilating typically include a manifold enabling introduction of ventilating gases and intermittent exhalation of patient breath simultaneously with insertion and operation of a tracheal suctioning catheter. The manifold structure typically includes multiple ports, usually the open ends of respective conduits extending from a common chamber. One such port is interfaced to a patient through a patient connection device. The suction catheter is often included within an assembly which is connectable to a second port of the manifold. The catheter assembly conventionally includes a collapsible plastic envelope positioned entirely to surround the catheter. A practitioner manually externally collapses the envelope onto the external surface of the catheter, and advances the catheter through the manifold into an access tube connected to a patient, retracting the catheter in a similar fashion following the aspiration procedure. 
   The manifold thus provides a first pathway for ventilation gases, and a second pathway for the catheter. The catheter provides isolation from the ventilating gases for fluids withdrawn from the patient through the manifold. When the catheter is withdrawn, it is often desired to continue regulated ventilation through the manifold. In some cases, it is desirable for the catheter assembly to be disconnected from the manifold, without disturbing the ventilation of the patient. It is thus necessary to provide for a gas tight sealing of the pathway formerly occupied by the catheter upon its removal. Early efforts in this connection have involved the provision of auxiliary sealing structures for use in association with the manifold. Eventually, specialized valves were developed for inclusion in a manifold assembly. These valves are structured to provide a travel path for a catheter when catheter suction is needed, while maintaining an adequate seal. 
   Material prior art structures and methods are described, among other places, in U.S. Pat. No. 5,333,607 to Kee, et al.; U.S. Pat. No. 5,354,267 to Niermann, et al.; U.S. Pat. Nos. 5,357,946 and 5,445,141 to Kee, et al.; U.S. Pat. Nos. 5,140,983 and 5,487,381 to Jinotti; U.S. Pat. No. 5,882,348 to Winterton et al.; U.S. Pat. Nos. 5,735,271 and 5,730,123 to Lorenzen et al. and U.S. Pat. No. 5,642,726 to Owens et al. These patents each disclose ventilator manifold devices and systems in which those devices are utilized. The &#39;267 patent, for example, discloses a manifold and a multi-position stop cock valve. The valve is provided with a “Tee” shaped internal stem channel pattern so that the stem may be positioned selectively to wash the internal lumen of a catheter, to irrigate the patient or to accommodate travel of the catheter through the stem to suction the patient. The valve may be plugged directly into an access port of the manifold. Patient ventilation is conducted without respect to the valve through other ports of the manifold. The valve itself constitutes an integral component of a catheter assembly, and must be removed from the manifold with the remainder of that assembly. The &#39;348 patent discloses a valved manifold embodying a multi-position stop cock valve. The ventilation port is transverse the patient interface port, and is thus characterized by more dead air space than is generally regarded as acceptable for neonatal applications. 
   U.S. Pat. No. 6,729,326, issued May 4, 2004, to Winterton, et al., discloses an inexpensive, yet reliable, manifold assembly incorporating a valve positioned to minimize dead air space within the manifold and capable of passing a catheter. The assembly includes a valve that provides a sealed gas flow path through the manifold in both its open and closed conditions with respect to catheter travel. The assembly is particularly useful in neonatal applications, because it is constructed to minimize fluid flow turbulence of ventilating gases and to minimize the likelihood of respiratory therapy fluids introduced through an aspiration catheter from back-washing into the ventilation channel of the manifold. The valve component of the assembly is of the stop cock variety. That is, it comprises a stem or core element which is rotated between open and closed conditions within a housing. In both conditions, an open passageway, comprising a portion of the ventilation circuit, exists through the valve stem. In this arrangement, an aspiration catheter must pass through the interface between the valve stem and the inner wall of the housing to enter and pass through the interior of the stem. The disclosure of the &#39;326 patent is incorporated by reference in its entirety as a portion of this disclosure for its teachings concerning the structure and operation of valved manifolds in medical applications. 
   The aspiration catheters used to aspirate adults or juveniles are sufficiently rugged to resist closure of a valve within which they are positioned. In the event that an operator inadvertently attempts to close the valve, this resistance alerts the attendant, or operator, to the presence of the catheter. Either the catheter can then be removed to permit valve closure, or it is recognized that the catheter should remain in place, and the valve should be left open. Neonatal catheters are relatively fragile, compared to those used for the aspiration of adults or juveniles. While neonatal catheters may be manufactured from similar, or the same, material as catheters for adults, the smaller size of neonatal catheters, and attendant smaller cross-section, renders such catheters more susceptible to damage. In practice, an inadvertent or mistaken effort to close the valve with such a catheter in place can result in severe damage to the catheter. It is conceivable that a distal portion of a neonatal catheter can be completely severed by action of a user closing a valve element, thereby placing an intubated patient at risk of receiving the severed tip as an undesired pulmonary implant. 
   BRIEF SUMMARY OF THE INVENTION 
   This invention provides an improvement to valve structures having an interface between two surfaces movable with respect to each other between open and closed conditions. For simplicity, it is described with particular reference to valves having rotating stems within a valve housing, most notably of the type disclosed by the &#39;326 patent. It is described in this disclosure by reference to neonatal ventilation circuits, although it has other uses, particularly in connection with other medical procedures requiring the passage of a delicate tube through a valve. 
   According to this invention, a recess, which may be regarded as a “pocket,” is provided to operate on a portion of an inserted catheter near the interface between the stem and the internal wall surface of the housing. That is, the pocket receives a portion of a catheter passing through a bore communicating through the housing to the interior of the stem. The pocket is structured and arranged such that as the stem is rotated from its open condition towards its closed condition, the attendant will become aware of resistance to valve closure before the catheter is exposed to damaging shear forces. According to certain embodiments, the pocket is structured such that the stem can be rotated to a closed condition without shearing the catheter. 
   The pocket operates, in part, to change a load condition imposed by the valve components upon the catheter sidewall from an essentially pure applied shear load to a loading condition including a component of force directed along an axis of the catheter, or normal to the shear plane of an applied load on the catheter cross-section. The load condition provided by the invention permits an operator to receive enhanced feedback, compared to the prior art, that the catheter is still in place and must be removed. Furthermore, when undesirably closing a valve onto a catheter, a portion of an applied load on the catheter typically is in a direction operable to separate valve components potentially to provide clearance between sealing members for a squashed catheter. 
   In certain embodiments, the different loading on a catheter afforded by the instant invention permits seal components to separate sufficiently to resist excessively damaging the catheter, even if the valve accidentally is rotated to a substantially closed position. However, the invention provides enhanced feedback to a user to avoid catheter damage. Furthermore, preferred embodiments virtually eliminate risk of shearing off an end portion of a catheter. 
   In any case, the configuration of the pocket generally allows a catheter to be flattened and folded between a stem and its housing, rather than sheared into two pieces. In certain embodiments, the pocket can change an end constraint condition caused by at least one valve component (stem and/or housing), to permit rotation and reorientation of a portion of the catheter held by that component. The reoriented catheter portion is more able to bend and fold to avoid shear induced damage. A currently preferred embodiment reduces a shear stress concentration in an area of an entrapped catheter&#39;s cross-section. 
   The term “shear forces” is used in this disclosure in a broad sense to include all of the pressures and forces inherently applied to the catheter at the interface between the stem and housing as the stem is rotated. The term “damaging” refers to the magnitude of shear forces resulting in a catheter&#39;s becoming subjectively unfit for continued use, having been subjected to those forces. It is recognized that a catheter may be dented, or visibly impacted, by valve actuation. Such denting in an undamaged catheter sometimes may be massaged by a user to return a catheter to an undented configuration. Alternatively, the dented catheter sidewall may creep back to an undented configuration of its own volition. In any case, a damaged catheter is subjectively unfit for continued use. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings, which illustrate what are currently regarded as the best modes for carrying out the invention: 
       FIG. 1  is a side view in section of a valved manifold portion of a conventional 
       FIG. 2  is a side view in section illustrating the manner in which the valved manifold of  FIG. 1  may be connected in operable association with components of a suction catheter assembly; 
       FIG. 3  is a pictorial view of a first valved manifold incorporating the invention, the manifold being shown from its ventilator connection end, with the valve stem rotated approximately 30 degrees from its fully closed condition; 
       FIG. 4  is a view, partially in section, taken along the section line  4 - 4  of  FIG. 3 ; 
       FIG. 5  is an enlarged detail view of the portion of  FIG. 4  labeled “5”; 
       FIG. 6  is a top view of a second valved manifold constructed according to principles of the invention, including a portion of an installed catheter; 
       FIG. 7  is a close-up end view in elevation, looking into the opening of the access port of the manifold of  FIG. 6  (at section  7 - 7  and looking in the direction of the arrows), without an installed catheter; 
       FIG. 8  illustrates a shear-loaded plane located between closing components of both an unmodified valve and one embodiment of a modified valve; 
       FIGS. 9-12  illustrate planar components arranged to better illustrate certain aspects of the invention; and 
       FIG. 13  illustrates a core pin operable to produce a pocket in a molded article according to principles of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate certain details of construction of a ventilation/aspiration arrangement of the type disclosed by the &#39;326 patent. The illustrated arrangement includes a valved manifold assembly, designated generally  22 , which comprises a stem element  23  configured to mount within a valve housing portion  24 . The stem element  23  is integral with a ventilator connection structure  25 , which functions as a knob, in that it may be turned by finger pressure to rotate the stem element  23 . The stem element  23  is structured with an open interior  26 , defined by a continuous wall  27 . When the stem element  23  is installed within the valve housing portion  24 , the open stem interior  26  provides a passageway for ventilation gasses, among other things. The stem element  23  may be rotated between open and closed conditions. In its open condition, a valve stem port  28  through the wall  27  registers with the open interior of port  29  of a catheter entry portion  30  of the valved manifold assembly  22 . In its closed condition, the stem element  23  seals the communication path between the catheter entry portion  30  and the valve housing portion  24 . In both positions of the stem element  23 , a fluid flow pathway (the open stem interior  26 ) remains through the stem element  23 . 
   In  FIG. 2 , the valved manifold assembly  22  is shown in association with a catheter assembly, designated generally  32 . A suction control valve, generally  34 , may be connected to the proximal end  36  of the assembly  32 . A suction catheter  38  is carried within, and is substantially enveloped by, a flexible sheath  40 . The distal end  42  of assembly  32  may be connected to the catheter entry portion  30  of the valved manifold assembly  22 . The catheter  38  may then be selectively extended through or withdrawn from the catheter entry portion  30 . An extended catheter  38  passes through the valve stem port  28  and out through the open stem interior  26  to an extended length beyond distal end  43  of stem element  23 . With the catheter  38  withdrawn, the ventilator connection structure  25  may be rotated to close catheter entry portion  30 . Aspiration/ventilation may then continue through the open stem interior  26  and ventilator connection end  45 . 
     FIG. 3  shows a first valved manifold, designated generally  62 , of this invention from its ventilator connection end  45 . It is constructed generally the same as the valved manifold assembly  22  of  FIG. 1 , except for the modifications described in this specification. Accordingly, like numbers are used to designate corresponding like features. The operation of the valved manifold  62  of this invention is substantially as described by the &#39;326 patent, the disclosure of which is incorporated herein by reference to avoid duplication of description. 
     FIGS. 4 and 5  show internal features embodying the invention; specifically the size and shape of the pocket  64 . Illustrated pocket  64 , adapted for a neonatal application, encompasses about 0.001 additional cubic inches of volume. This pocket  64  resides primarily in the stem element  23  at the interface between the stem element  23  and the interior wall of the valve housing portion  24 . It is shaped and dimensioned to receive and contain a segment of a catheter (not shown) extended through the open stem interior  26 . As the pocket  64  is rotated with the valve stem element  23 , the captured segment of a catheter so positioned can be rotated with the valve to approximately the fully closed position without shearing the catheter. 
   The port  28 A is relatively elongate and approximately oval shaped. The modified port  28 A and pocket  64  permit a catheter to adjust its local orientation relative to the stem interior  26  to a more enhanced degree than would be possible in port  28  structure of  FIG. 1 . Such adjustment in local orientation of the catheter reduces a shearing force applied to the catheter by stem element  23  and catheter entry portion  30 , compared to the prior art. A valved manifold assembly  22  structured according to the invention includes structure, such as pocket  64 , that permits or encourages a catheter to be folded about the body of the valve housing portion  24 , thereby reducing damage to the catheter. The pocket  64  can be structured to permit a catheter to rotate in a direction, from an installed neutral position, to reduce the size of its cross-section that must be folded as a valve is closed. 
   Furthermore, at least a portion of the trailing edge  66  of port  28 A desirably is radiused as illustrated in  FIG. 5 , or otherwise blunted, additionally to change a load applied to a catheter by structure of a closing valve. As modified according to principles of the instant invention, the corner surface of illustrated edge  66  includes a surface having a radius, although such radius need not be a constant value. Radiused edge  66  simply forms a more blunt surface adapted for contact to a catheter sidewall as the valve portion of manifold  62  is displaced in a closing direction. At least a portion of radiused edge  66  presses onto a catheter sidewall in compression as the valve portion of manifold  62  is closed onto the catheter. Such contact with blunt edge  66  tends to crush the catheter, rather than acting like a sharp edge of a pair of scissors and cutting the catheter by way of a substantially pure shear loading. Radiused edge  66  also acts somewhat like a bearing, in that it better slides across a catheter sidewall surface, rather than digging into that surface with the cut-enhancing action of a sharp edge. 
   Still with reference to  FIG. 5 , a portion of a cooperating edge of port  29 A may also be blunted, further to reduce a shear loading on a catheter as a valve portion is closed. The cooperating edge of port  29 A includes that portion which last overlaps the stem structure to form a seal between the catheter entry portion  30  and interior  26  of stem element  23 . However, it must be recognized that blunting structure arranged in a mold cavity and operable to blunt a corner/edge portion of port  29 A requires a more complex core arrangement to permit removal of molded parts. 
   In the improvement, the load applied on the trapped catheter is changed from substantially a pure shear load across a diagonally trapped cross-section of the catheter. Contact onto a catheter sidewall by the radiused edge  66  occurs spaced apart in a normal direction from the shear plane substantially defined by the perimeter of port  29 A at the cylindrical inner surface of the valve housing portion  24 . (Note that the thus-defined shear plane is not a planar geometric element, but is better described as a section of a cylindrical element. In that context, normal may be defined relative to a local portion of such surface). Disposing the contact location of port structure-to-catheter sidewall at a location spaced apart from the shear plane provides a moment arm effective to assist in folding a squashed catheter. The end result is preferentially to deform the catheter, rather than simply cut it by an applied shear load. Consequently, as a practical matter, an attendant attempting to rotate the stem element  23  to its closed condition is more likely to notice resistance well before an emplaced catheter is damaged. 
     FIGS. 6 and 7  illustrate a second valved manifold, generally indicated at  70 , constructed according to principles of the invention. With reference to  FIG. 6 , a horizontal plane may be defined containing axis  72  of stem element  23  and axis  74  of catheter entry portion  30 . An angle α, measured between axis  72  and axis  74 , typically is about 142 degrees. Angle α desirably is oblique, whereby to facilitate insertion of a catheter into open interior  26  in stem element  23 . A second embodiment of a pocket  64 A is formed in the structure of valve housing portion  24  in association with port  29 . Illustrated pocket  64 A may be substantially defined by a volume removed through a Boolean subtraction operation on wall structure of port  29  of a conventional neonatal catheter that is substantially defined by approximately prismatic shapes adapted to provide a moldability-enhancing draft, and a cutting cylinder having a diameter sized approximately in harmony with a diameter of a catheter, such as catheter  38 . As illustrated in  FIG. 7 , an axis of the cutting cylinder lies in a plane passing through axis  74  and oriented at an angle β from a normal to the horizontal plane. It currently is preferred for angle β to be about 15 degrees. However, angle β may be selected from an operable range between about 5 degrees and about 90 degrees. The combination of angles α and β operate in harmony to urge a separation between edge structure of ports  28  and  29 , providing a space in which to receive a catheter without shearing through its cross-section. 
   One effect that certain embodiments of pocket  64 A may have on a load applied to an entrapped catheter, which is pinched between edge structure of cooperating ports in a closing valve, can best be described with reference to  FIGS. 5 and 8 . In a valved manifold assembly  22  having a conventional arrangement of ports  28  and  29 , a stress concentration is imposed at a sharp corner area  78  of a cross section  80  at the shear plane of an entrapped catheter. With reference to  FIG. 8 , illustrated pocket  64 A provides an additional area  82  at the shear plane, effective to reduce an average applied stress across that shear plane, compared to the conventional arrangement. Furthermore, a magnitude of the stress concentration at area  78  is reduced, because the effective sharp corner imposed at area  78  by closing edge structure of the valve is reduced in sharpness. 
   Pocket  64 A can effectively change the shape of the catheter&#39;s cross-section that is loaded in shear to provide a more uniform cross-section thickness, denoted as “T” in  FIG. 8 . With illustrated pocket  64 A, an effective length, in a direction normal to the thickness “T,” of the entrapped cross-section also increases. Because the pocket  64 A effectively enlarges an opening of port  29 A, valve actuation structure (e.g., stem element  23 ) must be rotated by an additional increment to fully close the valve. In one currently preferred embodiment of valved manifold  62 , stem element  23  must be rotated by about an additional 15 degrees to fully close the opening through port  28 A, when compared to an unmodified valved manifold assembly  22  of corresponding size. 
     FIGS. 9-12  illustrate the principles of operation of the invention in structure having less complexity compared to a valved manifold  62 . The structures illustrated in  FIGS. 9-12  include flat plates  90  and  92 . Plate  90  may be regarded as analogous to a stem element  23 , with plate  92  being analogous to a valve housing portion  24 . Of course, the reverse may also be equally workable. Plate  90  carries a conduit bore  94  that can be positioned in registration with, for fluid communication through, conduit bore  96  in plate  92 . The illustrations depicted in  FIGS. 9-12  are cross-sectional views looking at a plane passing though a centerline of the bores  94  and  96 , and extending transversely in a direction of “valve” actuation. Bores  94  and  96  are simple orthogonal cylindrical conduit structures. Bore  94  also carries a pocket  98  disposed at an interface between plate  90  and plate  92 . Pocket  98  is defined, at least in part, by wall  102 . 
   The wall  102  forming pocket  98  desirably is arranged at an angle relative to a local normal N (see  FIG. 12 ) of the shear plane defined by perimeter edge structure including edge  106  and edge  108 . Consequently, a load F applied by wall  102  to the sidewall of an entrapped catheter  110  (see  FIGS. 10 and 12 ) has a component N directed normal to the shear plane, and in addition to the shear component S. “Valve” structures such as illustrated in  FIG. 11  and lacking a pocket (such as pocket  98 ), apply only a load S at the shear plane. A pocket  98  introduces a normal component of load operable to urge edge structure (e.g., edges  106 ,  108 ) defining boundaries of the shear plane in opposite directions effective to separate the seal formed between the plates  90  and  92 . The separated plates  90 ,  92  can therefore provide a space in which the squashed catheter  110  may fit as the “valve” is displaced to a fully closed position. Therefore, the entrapped and squashed catheter  110  is more likely to be spared damage to such an extent that it is no longer serviceable. 
   Wall  102  can be flat (chamfered, as illustrated in cross-section), or radiused, or may have any other operable configuration. The wall  102  of pocket  98  resists digging into a trapped catheter sidewall to resist damaging that catheter. The illustrated wall  102  is one embodiment of a blunt trailing edge. When closing a valved manifold  62 , an operator may therefore receive additional feedback that a catheter improperly is present, compared to an unmodified valved manifold assembly  22 . Wall  102  may be formed to include, or be formed by, a radiused edge  66 . In general, a pocket typically provides structure adapted to slide in a catheter&#39;s axial direction better than the sharp corner or squared-off boundary edge of corresponding port structure of a prior art valved manifold assembly  22 . 
   With reference to  FIGS. 10 and 12 , it may be seen that a portion  112  of the wall  102 , which includes the trailing edge  108 , is adapted to make contact with a sidewall of catheter  110  at a location spaced apart by a distance “d” in a normal direction from a shear plane formed between plates  90  and  92 . The moment generated by the offset distance “d” is operable to urge folding of the catheter  110  with respect to edge  106  as the “valve” structure is displaced towards a closed position. 
   The stem element  23  and valve housing portion  24  of a valved manifold assembly  22  or valved manifold  62  typically are manufactured by injection molding of medical grade plastic, or similar operable material, inside suitably formed tooling. Tooling used to mold prior art valved manifold assemblies  22  typically employs simple cylindrical cores to define bores  28  and  29 . Therefore, valved manifold assembly  22  typically has sharp corners at boundary edges  106  and  108 . Such sharp edges are prone to shearing through delicate catheters  110  at the plane defined by edges  106  and  108  when those valve structures are closed onto an entrapped catheter. Sharp, or substantially squared-off, corner edges of prior art devices dig in and apply a substantially pure shear loading S to an entrapped catheter. 
   In an improved valve, such as valved manifold  62  illustrated in  FIG. 3 , an effort typically is made to create tooling that includes a modified mold cavity having core structure adapted directly to form improved structure, such as pocket  64  with a radiused edge  66 , or alternatively shaped wall  102 . For example,  FIG. 13  illustrates a core, generally indicated at  114 , operable simultaneously to form both of bore  94  and pocket  98  depicted in  FIG. 9 . The mold&#39;s parting line is illustrated at plane  116 . Cylindrical portion  118  is adapted to form bore  94 , with pocket  98  being defined by volume addition  120 . Cylindrical portion  124  may be carried in sliding reception in a mold cavity to permit removal of a molded article, if required. It is within contemplation alternatively to machine improved pocket structure into valve components structured according to the &#39;326 patent, and made using unmodified tooling. 
   Reference in this disclosure to details of the illustrated or other preferred embodiments is not intended to limit the scope of the appended claims, which themselves recite those features regarded as important to the invention. Individual structural features may be used alone, or in combination, to form additional embodiments structured according to principles of the invention. For example, alternatives within contemplation may include any or all of: a pocket  64 , pocket  64 A, and a blunt edge  66 .