A resuscitation bag (bag valve mask resuscitator or BVM or BVMR) or other similar ventilation device (for example: anesthesia bag) includes a structure that allows a selectable, and repeatable volume be delivered to patients. The reservoir of the BVMR is formed from elastic, gastight material in the form of an elongated hollow body, with an essentially circular cross section. A range of motion control (ROMC) structure controls, or selectively limits the range of motion or collapse of the elastic bag to limit or control the volume expelled from the bag to the patient.