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Pneumothorax is the condition where air is present in the thoracic cavity.
· Stab wounds and other penetrating wounds of the thorax. The negative pressure in the thorax cavity will suck the air into the cavity.
· Barotrauma. If a diver surfaces without exhaling, the air in the lungs will expand due to the lower pressure on the surface. This expansion can rupture the lung and air will enter the thoracic cavity. This can also cause an air embolism. Explosions causing shock waves can also result in rupture of the lungs.
· Medical conditions. Lung pathology such as emphysema can cause pneumothorax. Sometimes young people develop this condition sponta-neously.
The lungs need a negative intra-thoracic pressure for expansion. When a pneumothorax originates, this negative pressure is lost, and the lung collapses. In some conditions air may also enter the thoracic cavity, but be unable to leave it again, usually because of a one-way valve-like action of the tissue. This results in a life-threatening complication, the tension pneumothorax. The increased positive pressure in the thoracic cavity causes decreased blood flow to the heart, and the patient goes into shock and may die.
In a living individual an X-ray of the chest will show the collapsed lung as well as air in the thoracic cavity. In the deceased person the thoracic cavity must be opened under water. This can easily be done by folding back the skin and muscle on the sides of the thorax so that a small reservoir is formed, which is then filled with water. An opening is made below the water level into the thoracic cavity. If there is a pneumothorax, air bubbles will escape into the water.
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