Why a Chest Tube is Placed. A chest tube is placed for a variety of reasons. One reason, as you mentioned, is to help the lung re-inflate when someone has a collapsed lung, also known as a pneumothorax. In that circumstance, a chest tube is inserted along the side of the ribs to allow the lung to reinflate.
A. Osmosis is the passive movement of water from an area high in water concentration, across a semi-permeable membrane, to an area low in water concentration.
Water moving down finds symbolism in rivers which represent the linear flow of time. The most extreme form of water in downward movement is in waterfalls offering the most extreme symbolism of uncontained downward moving water. Water at its most passive is symbolized by lakes and ponds and other small bodies of water.