Positional asphyxia occurs when the position of a person’s body interferes with their respiration, resulting in death from asphyxia or suffocation. At death, the victim must be found in a position that interferes with pulmonary gas exchange (breathing). Such a position may range from one that causes obstruction of the mouth and nose, to one that causes restriction of the chest and diaphragm.
The inability of the victim to escape this position must be explained. In positional asphyxia death unrelated to restraints, unconsciousness due to acute alcohol intoxication is the most frequent explanation of the victim’s inability to escape from asphyxiating posture. All other causes of death –natural or unnatural, medical or traumatic, must be explored by autopsy and excluded to a reasonable degree of medical certainty.
Petechial haemorrhages on the face and neck, due to rupture of small venules on application of pressure. Pressure may be severe enough in strangulation to rupture larger plexus of venules producing larger echymoses. Second most common place for petechial haemorrhages is chest especially visceral and parietal pleura, due to negative pressure developed in an increased effort to inspire. Petechial haemorrhages are seldom seen in hanging and not seen at all in drowning. They might be seen in some bleeding disorders as well.
Cyanosis is most commonly seen on the face, especially the lips. Cyanosis is the bluish discolouration of face due to reduced oxygenated haemoglobin.
Other Increased fluidity of blood and enlargement and engorgement of right heart is also found, but these findings are not included in the classical signs of asphyxia. In manual strangulation, arterial supply is not hampered while venous drainage of head and neck is obstructed, leading to more leakage of fluid from veins. This results in bulging of eyes, protrusion of tongue, oedema and congestion.