Final answer:
Bluish or reddish facial discoloration following a traumatic asphyxiation is caused by high pressure on the chest, leading to congestion of blood in the veins of the face and neck and subsequent cyanosis.
Step-by-step explanation:
The underlying cause of bluish or reddish facial discoloration following traumatic asphyxiation typically involves high pressure on the chest. This pressure can lead to blood being forced backward from the right side of the heart, specifically the right atrium, into the veins of the face and neck. This buildup and congestion of blood in the veins can cause the bluish or reddish discoloration seen during asphyxiation. The phenomenon is essentially a severe form of congestive cyanosis, which is when the skin turns bluish due to poorly oxygenated blood. While traumatic asphyxiation often involves external forces compressing the chest, it is different from the congenital heart conditions like tetralogy of Fallot, which can lead to a 'blue baby' syndrome due to a defect in the heart’s structure and an insufficient supply of oxygenated blood. Both conditions, however, result in cyanosis, which is a hallmark indicator of insufficient oxygenation in the body.