Kangaroos Breathing- Negative pressure is created in the lungs by lowering the diaphragm and expanding the ribcage, a mechanism used to draw air into the lungs (called inspiration). This is possible because air follows a pressure gradient moving from an area of higher pressure (atmospheric air) to an area of lower pressure (the air sacs of the lungs (i.e. the intraalveolar space)). Kangaroos are pretty special because they actually use less energy to breathe during hopping than used at rest.