What are the odds for a collapsed lung to fix itself?

Low: A totally collapsed lung from a pneumothorax will generally not reinflate. A pneumothorax occurs when there is a puncture in the lung much like a balloon and air escapes into the space between the chest and lung. If the leak is small and heals over by itself quickly, there is a small chance the lung could reinflate but generally it requires a small vacuum tube be placed between lung and chest.

Size: Smaller collapse often heals. Larger may need drainage. The hole in the lung from trauma or spontaneous collapse can potentially seal in just a few days (like a scab). The lung tissue takes longer to fully heal, depending on type of injury. If from trauma, associated chest wall injury (rib fractures, etc...) as well as chest tube site may take weeks to months to heal.