What causes the bluish or reddish facial discoloration after traumatic asphyxiation?

The bluish or reddish facial discoloration after traumatic asphyxiation is primarily caused by high pressure on the chest leading to blood being forced into the face and neck. When the chest is compressed due to trauma, such as in cases of asphyxiation, it can obstruct venous return from the head and upper body. This obstruction leads to increased venous pressure, which results in blood pooling in the face and neck, causing the characteristic discoloration.

While decreased blood flow to the brain and asphyxiation from lack of oxygen are indeed critical factors in understanding the physiological responses to traumatic asphyxiation, they do not directly cause the discoloration. Additionally, an allergic reaction is not relevant in this context, as facial discoloration is not typically a symptom of such reactions, especially in the case of trauma-related conditions. Understanding the mechanics of chest compression can help clarify why facial discoloration occurs in these scenarios.