A collapsed lung, medically termed pulmonary collapse, can manifest in two distinct forms: pneumothorax and atelectasis. These two conditions have differing etiologies and treatment approaches. Pneumothorax, commonly known as a collapsed lung, occurs when air leaks into the space between the lung and the chest wall (pleural space). This often results from the rupture of a small air sac (bleb) on the lung surface, leading to air accumulation that exerts external pressure on the lung, preventing it from fully expanding. Atelectasis, on the other hand, involves the collapse of a section or lobe of the lung due to insufficient air entry. This can be caused by an obstruction within the airway, such as a mucus plug, or external compression from a tumor or other mass, which prevents air from reaching specific areas of the lung, leading to their collapse.