A medical valve assembly includes a tube extending between a first tube end and a second tube end to define a passageway extending along a longitudinal axis between the ends. A plunger plate extends radially from the second tube end of the tube, and a valve housing surrounds the tube about the second tube end and extends from a first valve housing end to a second valve housing end. The valve housing includes a flange extending radially inwardly from the second valve housing end and disposed in spaced relationship with the plunger plate to define a distance dimension D extending therebetween. An elastomeric seal is compressed between the plunger plate and the flange, and one of the valve housing and the tube is axially movable relative to the other to vary the distance between said plunger plate and said flange and adjust an inner diameter of the elastomeric seal.
