A Pneumothorax is a collection of free air in the chest cavity (thoracic cavity) that causes the lung to collapse. Pneumothorax may occur on its own in the absence of underlying disease; this is termed Spontaneous Pneumothorax. Pneumothorax may also occur because of an injury or underlying lung disease. A Pneumothorax arising as a result of lung disease or injury requires immediate treatment. Treatment may include insertion of a Chest Tube or aspiration of the free air in the chest cavity by using a Decompression Needle.