<unk><unk>  can result from puncture of parts of the respiratory or gastrointestinal systems.  Particularly in the chest and neck, air may become trapped as a result of penetrating trauma (e.g., gunshot wounds or stab wounds) or blunt trauma. Infection  (e.g., gas gangrene) can cause gas to be trapped in the<unk>  tissues.<unk><unk>  can be caused by medical procedures and medical conditions that cause the pressure in the alveoli of the lung to be higher than that in the tissues outside of them.  Its most common causes are pneumothorax and an improperly functioning chest tube. It can also occur spontaneously due to rupture of the alveoli, with dramatic signs.  When the condition is caused by surgery it is called surgical<unk> . The term spontaneous<unk><unk>  is used when the cause is not clear.<unk><unk>  is not usually serious in and of itself, but the underlying causes, such as pneumothorax, can be.
Subcutaneous emphysema causes
Air embolism causes
Aspiration pneumonia causes
Pleurisy causes
Pulmonary edema causes
Pneumomediastinum causes
Acute bronchitis causes
Hemothorax causes