In some examples, a medical aspiration system includes a vacuum source; a vacuum tube coupled to the vacuum source; a vent tube; and a device configured to convert a constant suction force from the vacuum source into a periodic suction force, the device including a housing configured to receive a portion of the vacuum tube and a portion of the vent tube; a first plunger; a second plunger; and a rotatable cam configured to cause the first plunger to periodically compress the vacuum tube and to cause the second plunger to periodically compress the vent tube.