Lavage is defined as the washing out of hollow organs by copious injection and reinjection of liquid.  Gastric lavages, for example, are used for a wide variety of medical situations including poisonings, upper GI bleeding, ulcers, etc.  The normal current method of performing such a gastric lavage involves the insertion of a tube into a patients's stomach through his nose or mouth. 
According to principles disclosed in U.S. Pat.  Nos.  4,842,581, 4,872,866, and 5,049,135 one lavage apparatus for delivering lavage solution quickly and efficaciously to a patient comprises a rigid housing defining side-by-side parallel irrigation and aspiration cylinders in which plungers are inserted from first ends thereof.  The irrigation and aspiration cylinders have respective irrigation and aspiration check-valves at second ends thereof and inlet and outlet check-valves at sides thereof.  An anti-venturi septum extends to an intersecting line from the second ends of the cylinders.  This septum comprises two tapered, semi-circular-in-cross-section, baffles which meet at a sharp V-shaped apex which also forms a U-shaped intersection line to provide a full opening between a separate common exchange tube and both cylinders.  The separate common exchange tube, with the common nozzle is attached to the housing surrounding the second ends of the cylinders and said septum.  The internal size of the nozzle is about the same size as the inlet and outlet openings at the sides of the cylinders. 
Check-valves disclosed in the above-mentioned U.S. Patents comprise flat resilient membranes attached to an exterior transverse wall of a valve bore which flex to open when pressure is exerted into the bore of the check-valve and return to a flat, closed disposition against the transverse wall of the valve when pressure is exerted in an opposite direction against the resilient membrane.  One of the problems related to the use of flat membrane check-valves, as noted in U.S. Pat.  Nos.  4,842,581 and 4,872,866, is jamming such as is caused by incomplete valve passage of non-liquid or high viscosity matter which is a common by-product of lavage procedures.  In an attempt to find a solution for the jamming problem, flow orifice reducing shelves are installed in the flow path of the lavage solution upstream from the valves in order to allow larger surface-area membrane valves to be used because larger surface area flat membrane check-valves are not as susceptible to jamming as smaller surface area flat membrane check-valves.