A closed suction catheter includes a valve assembly and a manifold. A catheter tube is attached to the valve assembly and slidably secured within the manifold. The closed suction catheter may include one or more features for promoting an effective, safe, and efficient process for suctioning mucus and other fluids from a patient's lungs, and for cleaning the various components of the catheter system. For example, the closed suction catheter may include a tube wiper having a reinforced leading ridge and/or an internal ledge for efficiently wiping the catheter tube. The valve assembly may include a locking mechanism having a slider unit, a cam arm, and/or ribs that engage openings in the slider unit for maintaining a valve stem in proper alignment and an actuator on the valve assembly in a locked position. The closed suction catheter may include several other features, as well.