Aquarium air pump?
No. The article I saw showed a sophisticated build with various valves, a bellows bag and hydraulics, as well as a computer board and software. Via software, one could set the pump interval, and air pressure. It would operate the bellows to push air into the lungs, close off valves and open other valves, then evacuate the carbon dioxide exhalation from the lungs, then repeat. I imagine the cost of the components to be between $100 to $200. The author showed that it is possible to build your own ventilator with your 3D printer and some hardware that works like the hospital models (the low-cost models).