Abstract:
An obturator prevents the tips or flaps of a duck-bill valve from self-adhering during storage or during sterilization procedures. The obturator holds the tips apart until the end-user is ready to use the valve. The duck-bill valve is used as an air outlet valve in blood reservoirs.

Description:
FIELD OF THE INVENTION 
     This invention relates to a blood reservoir for use in an extracorporeal blood circuit. In particular, this invention relates to a means for preventing self-adhesion of a one-way air outlet valve in the blood reservoir. 
     BACKGROUND OF THE INVENTION 
     In cardiopulmonary bypass operations, a patient&#39;s circulatory system is linked to a heart-lung machine to permit the extracorporeal circulation of blood. In these surgical procedures, a bypass circuit is created where venous blood bypasses the heart and is reintroduced into an artery. Also, cardiotomy blood is scavenged from the surgical site, combined with the venous blood, and reintroduced into the patient. The extracorporeal bypass circuit performs numerous functions, including removing emboli and particulate matter entrained in the blood, regulating the carbon dioxide and oxygen content of the blood, and regulating the blood temperature. 
     In the past, venous blood was filtered and collected in a venous reservoir and the cardiotomy blood was filtered and collected in a cardiotomy reservoir. Work in this art area has included efforts to simplify and improve these systems, as, for example, providing combined venous and cardiotomy reservoir systems. Other work has been directed to simplifying and improving the blood storage, filtration, and defoaming systems for both venous and cardiotomy blood. 
     In some systems, a sealed venous reservoir is used. This allows a vacuum to be pulled in the reservoir for the purpose of assisting the removal of blood from the patient. However, using such sealed systems creates a potential problem. During the surgical procedure, it is possible to develop either over-or under-pressure situations within the sealed reservoir. Either situation can lead to undesirable consequences for the patient. Therefore, it is known to use safety valves which can regulate the pressure within the sealed reservoir so that it does not exceed acceptable positive and negative pressure limits. 
     Safety valves include unidirectional valves such as umbrella valves and duck-bill valves. A unidirectional valve permits the escape of air when there is a positive or negative air pressure within the reservoir. Umbrella valves typically are used to vent negative pressure in a reservoir. Duck-bill valves typically are used to vent positive pressure. This valve includes two tips or flaps and an integral base defining a generally cylindrical opening. The tips or flaps butt against each other preventing the passage of air in or out of the reservoir, responding to positive pressure within the reservoir by spreading apart. Duck-bill valves in current use typically are comprised of silicone materials which are engineered to respond to certain pressures, thus allowing fluid to flow through the valve at desired pressures. 
     We have discovered that the tips or flaps of duck-bill valves used as air outlet valves in blood reservoirs can adhere together after long periods of time or after exposure to adverse environmental conditions. Typically such valves comprise silicone. This self-adhesion is an extremely undesirable situation, as a non-functioning valve can produce a build-up of pressure in a venous reservoir, resulting in reverse blood flow. Thus, a need exists to prevent the self-adhesion of duck-bill valve tips when the duck bill valve is used as a safety valve in blood reservoirs. 
     SUMMARY OF THE INVENTION 
     We have invented a device, termed an “obturator”, which prevents the tips or flaps of a duck-bill valve from self-adhering during storage or during sterilization procedures. The obturator holds the tips apart until the end-user is ready to use the valve. The duckbill valve is used as an air outlet valve in blood reservoirs. 
     In one aspect, this invention is a method for preventing self-adhesion of the tips of a duck-bill valve during sterilization by providing an obturator having a plunger element; and inserting the plunger element between the tips of the duck-bill valve prior to sterilization. 
     The plunger element may be comprised of polymeric materials. Preferably, the plunger element is joined to a cap for ease of insertion and removal. More preferably, the plunger element and the cap are formed or molded from a single piece of plastic. 
     In a second aspect, this invention is a sealed blood reservoir comprising a top, a bottom, and a continuous sidewall, the top and bottom connected to the sidewall to form a sealed housing; the sealed housing defining an interior chamber; the housing having a blood inlet and a blood outlet in flow communication with the interior chamber; a duck-bill valve having two tips and an integral body in communication with the interior chamber; and an obturator comprising a plunger element positioned between and separating the tips of the duck-bill valve. 
     In a third aspect, this invention is a method of preventing pressurization of a sealed blood reservoir by providing a sealed blood reservoir as described above, providing a duck-bill valve having two tips and an integral body in communication with the interior chamber of the reservoir; and inserting a plunger element between the tips of the duck-bill valve, wherein the plunger element prevents the tips of the duck-bill valve from self-adhering. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the obturator according to the present invention. 
     FIG. 2 is a perspective view of the obturator of this invention inserted between the tips of a duck bill valve. 
     FIG. 3 is a cross-sectional view of a hard shell blood reservoir showing the placement of the duck-bill valve and the obturator of the present invention. 
     FIG. 4 is a cross-sectional view of the obturator and valve shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The obturator of this invention is useful with duck-bill valves that are used in closed or sealed blood reservoir systems. A combined cardiotomy and venous blood reservoir is disclosed in U.S. Pat. No. 5,411,705 (Thor et al.), hereby incorporated herein by reference. This type of reservoir can be adapted and made into a sealed reservoir. 
     The Figures illustrate the obturator and its placement in a representative duck-bill valve. The obturator was fabricated from polypropylene and placed in position in a duck-bill valve made of silicone. FIG. 1 shows obturator  10  comprising cap  20  and plunger element  30 . A perspective view of duck-bill valve  40  is with obturator  10  inserted is shown in FIG.  2 . 
     Valve  40  comprises tips  41  and  43  integrally joined to body portion  45  which is itself joined to base  47 . Base  47  may also function as an umbrella valve in response to negative pressure in the reservoir. The plunger element comprises a suitable material. A suitable material is one that is different from the valve material and one that will not chemically react with or adhere to the material of the valve during storage or sterilization procedures. Preferably, the obturator (i.e., the plunger element and the cap) is molded in a single piece from any suitable material. Such materials include, but are not limited to, polymeric materials comprising polyolefins, polytetrafluoroethylene (PTFE; also commercially available under the trade designation TEFLON™). 
     FIG. 3 shows a cross-sectional view of a combined venous and cardiotomy blood reservoir. This reservoir is sealed, that is, fluids such as blood or air do not leak into or out of the reservoir. Similar hard shell reservoirs are disclosed in U.S. Pat. No. 5,411,705 (Thor et al.). This reservoir comprises a rigid housing having a top, a bottom, and a continuous sidewall, where the top and bottom are connected to the sidewall to form an interior chamber. The interior chamber is in communication with a blood inlet and a blood outlet. A duck-bill valve is also in communication with the interior chamber. 
     The interior chamber typically includes a filter unit (not shown) that divides the reservoir into inlet and outlet chambers. These chambers are in fluid communication through the filter unit. A means for filtering and deforming the blood is disposed within the inlet chamber. In the reservoir shown in FIG. 3 rigid housing  102  has a cover  103 , a bottom  104 , and a continuous sidewall  105  forming enclosed reservoir  100 . Preferably, housing  102  is made of clear plastic so that medical personnel can observe the blood level in reservoir  100 . Sidewall  105  and bottom  104  are integrally formed, molded plastic, and cover  103  is a separate plastic lid that fits onto top edge  120  and is sealed to it by means known in the art, such as by ultrasonic welding or by adhering the parts together with adhesive. Alternatively, cover  103  may be integrally molded with the sidewall by know methods. Blood flows into reservoir  100  through cardiotomy blood or venous blood inlets  111  and  113 . The blood flows through filters to blood outlet  114 . Plunger element  30  of obturator  10  is shown inserted between the tips of duck-bill valve  40  which is held in position within portion  50  of cover  103  of the reservoir. 
     FIGS. 3 and 4 show the valve and obturator positioned in the reservoir cover. The reservoir is a sealed system, and typically uses vacuum to assist the removal of blood from a patient. Outlet  60  is positioned at the top of the chamber and is in communication with the outlet chamber. Duck-bill valve  40  is held in position in outlet  60  by portion  50  of cover  103 . Portion  50  is provided with annular projection  52 . Base or umbrella valve  47  forms a seal with the underside of portion  50 . Obturator  10  is inserted between the tips of valve  40 . Cap  20  of obturator  10  fits over annular projection  52 . If a positive pressure builds up in the reservoir, it is released through duck-bill valve  40 . If a negative pressure occurs, this can be equalized by the admission of air through umbrella valve  47 . 
     FIG. 4 shows a cross-sectional view of valve  40  installed on portion  50  of cover  103  of blood reservoir  100 . The valve is in communication with the outlet chamber of the blood reservoir. The obturator is removed from the valve during cardiovascular surgery and permits the flow of air through the valve in the direction of the arrow if there is positive pressure within the reservoir and permits flow of air to the chamber by means of umbrella valve  47  in the event of negative pressure. 
     The utility of the obturator was tested by positioning the obturator plunger between the tips of a silicone duck-bill valve fitted in the housing of a blood reservoir, as illustrated in the Figures. This was sterilized under standard EtO (ethylene oxide) conditions. The obturator was removed. With positive air pressure in the reservoir, the valve tips separated, thereby preventing a positive pressure in the reservoir. 
     In contrast, a reservoir fitted with a silicone duck-bill valve was treated under the same sterilization conditions as above, but without the obturator. The tips of the valve adhered together after conventional sterilization, allowing pressure to build up within thee interior chamber. 
     The obturator is useful when positioned during sterilization procedures and during long-term storage of reservoirs fitted with the valves. The obturator then is removed by the end-user of the blood reservoir before cardiovascular surgery. 
     Although particular embodiments of the invention have been disclosed herein in detail, this has been done for the purposes of illustration only, and is not intended to be limiting with respect to the scope of the appended claims. It is contemplated that various substitutions, alterations, and modifications may be made to the embodiments of the invention described herein without departing from the spirit and scope of the invention as defined by the claims.