Pericardial tamponade.
Blunt or penetrating trauma may cause bleeding into the tough fibrous sac that surrounds the heart, the pericardial sac. Since this sac cannot expand outward very much with the filling blood, the result is inward compression of the heart. This is known as cardiac tamponade or pericardial tamponade. The compression of the ventricles prevents adequate ventricular filling, leading to a reduction in preload, stroke volume, and cardiac output. A reduction in cardiac output leads to hypotension. A pulmonary contusion is bleeding within the lung tissue. With a hemothorax, the thoracic cavity is filled with blood rather than air.