Forensic Pathology - Asphyxia and Anoxia Vocabulary

Vocabulary flashcards defining key forensic pathology terms related to asphyxia, anoxia, classical postmortem signs, suffocative mechanism types, and related clinical conditions.

Asphyxia

Derived from the Greek term meaning 'absence of pulse', it actually refers to a state of hypoxia or anoxia and is considered a partial misnomer.

Hypoxia

A life-threatening physiological condition characterized by a partial lack of oxygen.

Anoxia

A complete lack of oxygen that eventually leads to demise; it is the preferred and technically more accurate term ('Anoxia Deaths').

Anaemic Anoxia

A form of anoxia where blood cannot carry enough oxygen due to low or abnormal haemoglobin (e.g., iron deficiency anaemia).

Toxic Anoxia

A state in which toxins prevent blood from binding to available oxygen (e.g., carbon monoxide poisoning).

Stagnant Anoxia

A condition in which blood does not reach the brain and organs even if oxygen levels are satisfactory, seen especially in cardiovascular events like myocardial infarction.

Anoxic Anoxia

A condition where not enough oxygen is made available to the body (e.g., suffocation) or around the body or to the lungs (e.g., choking).

Congestion

A classic sign of asphyxia marked by reddish discolouration of the skin of the face and head, caused by obstruction preventing venous return to the heart and filling the venous system.

Oedema

Extra-cellular tissue swelling caused by the transudation of fluid from veins due to increased venous pressure from obstructed venous return.

Cyanosis

Blue discolouration of the skin due to deoxygenated blood ($51\,g$ of reduced haemoglobin per $100\,ml$ in living individuals); it is independent of gravity and present both antemortem and postmortem.

Hypostasis

Postmortem pooling of blood in dependent body parts producing a bluish-pink discolouration that is dependent on gravity and present only in the postmortem interval.

Petechial Haemorrhages

Pin-point collections of blood ranging from $0.1\,mm$ to $2\,mm$ lying in the skin, sclera, conjunctivae, or under thoracic serous membranes, caused by an acute rise in venous pressure rupturing over-distended venules.

Suffocation

Asphyxia caused by a decreased oxygen tension in inspired air, resulting from low barometric pressure or displacement of oxygen by inert gases such as $N_2$ and $CO_2$.

Smothering

Asphyxia caused by the physical obstruction of external airways (mouth and nose) by an impervious object (e.g., hand, sheet) or mobile solid (e.g., grain, sand).

Choking

Asphyxia caused by physical obstruction of the internal airways (between the pharynx and bifurcation of the trachea) by foreign objects or acute obstructive lesions.

Bolus Death (Café Coronary Syndrome)

Sudden death resulting from vaso-vagal inhibition caused by a large bolus of food becoming lodged in the pharynx or larynx.

Vaso-vagal Inhibition

Rapid onset of cardiac arrest causing death immediately or within seconds due to sensory impulses traveling via glossopharyngeal nerves to the medulla and returning via vagal parasympathetic innervation to the heart.

Carboxyhaemoglobin

The compound formed when carbon monoxide binds to haemoglobin $250$ times more strongly than oxygen, causing tissue hypoxia and toxic anoxia.

Traumatic Asphyxia

Also known as crush asphyxia; mechanical fixation of the chest preventing respiratory movements required for inspiration and expiration.

Positional Asphyxia

Inability to breathe due to remaining in a specific body position for a prolonged period of time without being able to make sufficient respiratory movements against body weight.