In general, a rib fracture is not a life-threatening injury. However, rib fractures can lead to complications including a collapsed lung. Also known as atelectasis, a partial or complete collapse of the lung occurs when the air sacs in the lungs do not expand with air.  When you have a broken rib, it is common to breathe lightly avoid fully filling the lungs with air. This can lead to atelectasis. Breathing exercises can help to prevent this from happening.