A little on the gory side, but it is a good demonstration of ventilating lungs.
We were using this at a training day for a different group. In the video, you can see the lungs expand with each breath. If you watch the deflation period, it is much quicker when the PEEP valve is off. When the PEEP valve is in place, the lungs deflate to a certain point but hold some volume. Think of this as maintaining open alveoli that would normally collapse. These are then ready to accept now, oxygenated air with the next ventilation.
If you watch, you can see blebs forming on the right lung, among other places. This is because we have caused injury to the lungs by over-inflating them at times.
This is also a good exercise to watch the effects of hyperventilation on lungs and how they lungs are affected when we ventilate rapidly without giving enough time for them to deflate normally.