11 - pressure to the neck and asphyxia deaths

failure in supply of adequate amounts of oxygen

classification of asphyxia by pathophysiological mechanism: e.g. due to displacement of environmental oxygen by other gases; consumption of oxygen without replacement; confinement in sewers etc.

failure to transfer oxygen from the environment into the blood

classification of asphyxia by pathophysiological mechanism: e.g. external/internal obstruction in smothering, choking and hanging, extrinsic/intrinsic compromise of thoracic cage function in mechanical/traumatic asphyxia or chest wall trauma; and reduced oxygen binding capacity of the blood in carbon monoxide toxicity

failure of transport of oxygen due to a breakdown in supply or uptake, or a problem with blood flow due to local vascular compression reducing cerebral blood flow

classification of asphyxia by pathophysiological mechanism: e.g. hanging and strangulation

failure of cells to take up oxygen

classification of asphyxia by pathophysiological mechanism: e.g. cyanide impeding cellular utilisation of oxygen by damaging enzyme systems - chemical asphyxia

complex cases/combined mechanisms

classification of asphyxia by pathophysiological mechanism: e.g. drowning and hanging: combined venoarterial occlusion, upper airway obstruction from lifting of the tongue, and tracheal compression

dyspnoea phase

asphyxia sequence of events: increased respiratory rate and effort, cyanosis, and increased heart rate and blood pressure

convulsive phase

asphyxia sequence of events: loss of consciousness, laboured respiratory movements, facial congestion/petechiae, altered heart rate and blood pressure (variable), and involuntary micturition/defecation

pre-terminal respiratory phase

asphyxia sequence of events: irregular respirations, alternating apnoea and gasps, failure of respiration and circulation centres in the brain, and transient tachycardia

terminal phase

asphyxia sequence of events: respiratory arrest, hypotension, feeble, irregular heart rate, then asystole; pupils dilate and reflexes are lost

petechial hemorrhages, congestion and edema, cyanosis, right heart congestion and abnormal body fluidity

classical signs of asphyxia (4)

petechial hemorrhages

(Most important to the forensic pathologist) __in the skin of the face and the lining of the eyelids.

tardieu spots

subdural petechial haemorrhages

mechanical, non-mechanical, miscellaneous

types of asphyxia (3)

strangulation, hanging, choking, compression asphyxia, smothering

types of mechanical asphyxia (5)

carbon monoxide, cyanide, other asphyxiants

types of non-mechanical asphyxia (3)

drowning

types of miscellaneous asphyxia (1)

suffocation, strangulation, mechanical asphyxia, drowning

classification of asphyxia in forensic contexts: types of asphyxia (4)

smothering, choking, confined spaces/entrapment vitiated atmosphere

classification of asphyxia in forensic contexts: types of suffocation (3)

ligature, manual, hanging

classification of asphyxia in forensic contexts: types of strangulation (3)

positional, traumatic

classification of asphyxia in forensic contexts: types of mechanical asphyxia (2)

asphyxia

classification of asphyxia in forensic contexts: forensic situations where a body does not receive or utilise adequate amounts of oxygen

suffocation

classification of asphyxia in forensic contexts: a broad term encompassing asphyxia due to vitiated atmosphere and smothering associated with deprivation of oxygen

smothering

classification of asphyxia in forensic contexts: obstruction of the air passages above the epiglottis, including the nose, mouth, and pharynx

choking

classification of asphyxia in forensic contexts: obstruction of the air passages below the epiglottis

strangulation

classification of asphyxia in forensic contexts: asphyxia by closure of the blood vessels and/or air passages of the neck as a result of external pressure on the neck

ligature strangulation

classification of asphyxia in forensic contexts: pressure on the neck is applied by a constricting band tightened by a force other than the body weight

hanging

classification of asphyxia in forensic contexts: pressure on the neck is applied by a constricting band tightened by gravitational weight of the body or part of the body

manual strangulation

classification of asphyxia in forensic contexts: external pressure on neck structure by hands, forearms or other limbs

mechanical asphyxia

classification of asphyxia in forensic contexts: asphyxia by restriction of respiratory movements either by position of the body or external chest compression

positional asphyxia

classification of asphyxia in forensic contexts: the position of the individual compromises the ability to breathe

traumatic asphyxia

classification of asphyxia in forensic contexts: caused by external chest compression by a heavy object

drowning

classification of asphyxia in forensic contexts: asphyxia by immersion in a liquid

greek

The word 'asphyxia' originates from __ , meaning 'absence or lack of pulsation'.

absence or lack of pulsation

The word 'asphyxia' originates from Greek, meaning '__'.

asphyxia

In forensic medicine, it often refers to a physical obstruction between the mouth/nose and the alveoli, although other mechanisms exist where oxygen cannot be utilized at the cellular level without airway obstruction.

hypoxia

partial asphyxia

anoxia

complete asphyxia

asphyxiants

are defined as gases, liquids, solids (or metabolites) that deprive the body of oxygen by displacing it from the lungs or interfering with oxygen transport by haemoglobin or mitochondrial oxidative phosphorylation.

strangulation

Pressure applied to the neck by a ligature, hands, etc..

hanging

Pressure applied to the neck by a ligature combined with body weight.

choking

Physical obstruction within the airways.

compression asphyxia

pressure applied to the chest or abdomen, interfering with breathing

smothering

Physical obstruction of the mouth/nose preventing breathing

10-30 seconds

Petechiae can be produced rapidly, perhaps after __ of compression in a living victim

fatal

Asphyxial insults are not always __; the outcome depends on the nature, degree, and length of the insult.

sequelae, persistent vegetative state

Survivors may have no long-term effects, or they may suffer neurological damage (__) if oxygen deprivation is prolonged.

pressure to the neck, obstruction/occlusion of the airways, pressure to the chest/abdomen

types of mechanical asphyxial mechanisms (3)

manual, ligature strangulation, hanging

types under pressure to the neck (3)

obstruction of jugular veins, obstruction of carotid arteries, stimulation of carotid sinus baroreceptors, elevation of the larynx and tongue

Circumferential or direct pressure to the sides of the neck can cause: (4)

obstruction of jugular veins

Impaired venous return from head to heart (leading to congestion, cyanosis, petechiae).

obstruction of carotid arteries

If severe, causes cerebral hypoxia and collapse.

stimulation of carotid sinus baroreceptors

At the common carotid artery bifurcation, leading to a neurologically mediated cardiac arrest (vagal inhibition/reflex cardiac arrest). Stimulation sends impulses via the carotid sinus nerve (glossopharyngeal) to the brainstem, leading to parasympathetic impulses via the vagus nerve to the heart, causing profound bradycardia and potentially asystole.

elevation of the larynx and tongue

Closing the airway at the pharynx level. The trachea is more resistant to compression.

2 mins

Filmed hangings suggest lack of recognizable respiratory movements after ~__

7.5 mins

Filmed hangings suggest lack of muscle movements after ~__.

vagal inhibition

may explain sudden deaths with minimal neck pressure and the absence of classic asphyxial signs in some hangings. Therapeutic carotid sinus pressure can be unpredictable and has caused deaths.

manual strangulation

Definition: Pressure applied with hands (possibly forearms/limbs). A common mode of homicide.

manual strangulation

External signs include bruises and abrasions on the front/sides of the neck and lower jaw; patterns can be difficult to interpret due to the dynamic nature of assault. Fingertip bruises (rounded/oval, up to ~2 cm) and fingernail scratches (linear/crescent) from the assailant or victim may be seen

superior horns of the thyroid cartilage

manual strangulation: Injury to the __ is particularly vulnerable. Suspected fractures need microscopic confirmation.

greater horns of the hyoid bone

manual strangulation: Injury to the __ occurs less frequently. Calcification/ossification with age makes hyoid/thyroid cartilage less flexible and more prone to fracture

ligature strangulation

Definition: Pressure applied by a constricting item (scarf, belt, etc.). Can be homicidal, suicidal, or accidental.

ligature strangulation

Characterized by a clear demarcation of congestion, cyanosis, and petechiae above the ligature

ligature mark

ligature strangulation: A __ is usually present, reflecting the constriction and sometimes the pattern of the ligature material. Documentation (measurement, photography) is important. Wide or soft ligatures may leave little evidence.

suspension point

ligature strangulation: Distinguished from hanging by the absence of a ___ pattern.

ligature strangulation

Ligature marks typically encircle the neck horizontally, possibly with discontinuities (clothing/hair) or crossover marks

ligature strangulation

Post mortem, marks may appear as brown, parchmented bands due to drying of abraded skin

hanging

Definition: Suspension of the body by the neck, with pressure from body weight on a ligature

hanging

Complete suspension is not necessary; death can occur in sitting, kneeling, or half-lying positions.

hanging

A ligature mark is common, often a deep indentation, and discontinuous at the suspension point (sides, back, or front). A mark rising at the sides to an inverted V suggests a suspension point at the back.

pneumomediastinum, cervical emphysema

hanging: Attempts to breathe against upper airway obstruction can lead to __ (air in chest) and _ (air in neck tissues).

hanging

Absence of classic signs, even in full suspension, suggests rapid death, potentially involving carotid sinus pressure and neurogenic cardiac arrest.

autoerotic asphyxia

Definition: Fatalities during solitary sexual activity.

autoerotic asphyxia

Involves neck compression (device, restraint) to cause cerebral hypoxia and heighten sexual response. Primarily involves men. Death results from failure of safety devices or misjudgement

choking, suffocation, smothering

types under obstruction or occlusion of the airways

choking

Accidental internal obstruction of upper air passages by an object or substance (bolus obstruction)

cafe coronary

Complete, abrupt upper airway obstruction by a food bolus (often meat) occluding the oesophagus and larynx. Symptoms mimic heart attack (sudden onset). If complete, prevents breathing, speech, and coughing; death can be silent and quick, found at autopsy

suffocation

Fatal reduction of oxygen concentration in inspired air

suffocation

Can occur in environments with displaced oxygen (decompressed cabin, silo) or physical obstruction (plastic bag over head)

smothering

Physical occlusion of the nose and mouth

smothering

If the victim resists, injuries around the mouth and nose may be present (bruising, abrasion, laceration to lips/mouth, gum bruising in edentulous). Subcutaneous bruising may be found upon dissection. Difficult to diagnose at post mortem as it may leave no asphyxial signs.

compression, positional

types under pressure to the chest or abdomen (2)

compression asphyxia

Due to external weight or pressure (e.g., trapped in trenches, under machinery, crushed by crowds). Results in marked asphyxial signs. also known as traumatic or crush asphyxia

positional asphyxia

Due to an awkward body position preventing effective breathing. also known as postural asphyxia

positional asphyxia

Occurs when individuals get trapped (e.g., in railings, windows, between bed and wall) or are restrained in positions that limit breathing.

positional asphyxia

The victim is usually unable to escape due to impaired consciousness/cognition (intoxication, neurological disease) or misinterpretation of their struggle as resistance.

positional asphyxia

Diagnostic criteria include: deceased found in a position preventing adequate breathing, scene/circumstances suggesting self-placement (no third party), inability to move due to impairment, no internal airway obstruction, no CO/gas toxicity, and no significant natural disease explaining death.