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 molecules move from areas of high water concentration to areas of low water concentration through a selectively permeable membrane. A selectively permeable membrane allows small, soluble molecules to pass through it, but prevents large insoluble molecules from passing through.