Find a transparent hard plastic bottle, cut off the bottom of the bottle and seal it with a rubber mold. You can cut the balloon open for use.

The bottle mouth is filled with a balloon, and the balloon mouth is connected with the syringe through a plastic tube or a rubber tube to imitate the lung, and air or water is filled as a medium. By pushing and pulling the syringe, we can imitate the breathing of the lungs and the movement of the diaphragm.