What occurs due to the back flow of blood in traumatic asphyxia?

In traumatic asphyxia, the mechanism involves a sudden and severe compression of the thoracic cavity, often due to an external force, like a heavy object falling on the chest. This compression leads to an increased intrathoracic pressure, which can disrupt normal blood flow dynamics.

When this increased pressure prevents the normal return of venous blood to the heart, it results in the back flow of blood, primarily affecting the veins. This back flow leads to venous engorgement, particularly in the upper extremities and head. The consequence is that the veins become distended due to the accumulation of blood, creating a characteristic appearance of cyanosis, or a bluish discoloration in these areas. This is a hallmark sign of traumatic asphyxia.

The other options do not correctly describe the phenomenon associated with traumatic asphyxia. While there may be various cardiovascular responses following trauma, the specific effect of venous engorgement in the upper extremities is directly linked to the back flow of blood caused by the interruption of normal venous return due to increased thoracic pressure.