Suffocation, Asphyxia, and Fatal Pressure on the Neck

The Nature of Asphyxia• asphyxia - absence of pulsation. The

true meaning of the term is best described as pressure on the neck associated with cardiac arrest.

• The long and short of it is that a lack of oxygen leads to cell death.

• Anything that leads to lack of oxygen can be called asphyxia, but terms like hypoxia or anoxia are more accurate.

The Nature of AsphyxiaThe following conditions may be considered to be defects in the chain or respiration and are examples of asphyxia:

– Absence of oxygen tension in the atmosphere such as reduced barometric pressure, or replacement by carbon dioxide.

– Obstruction of the external respiratory orifices as in smothering or gagging.

– Blockage of internal respiratory passages.– Restriction of respiratory movements.– Disease of the lungs that reduces gas exchange– Reduction in cardiac function – Reduced ability of the blood to transport oxygen– Inability of the peripheral tissue cells to utilize the

oxygen being delivered to them.

Mechanical Asphyxia• The normal oxygen in the blood

according to the age and health of the subject.

• Young and middle aged adults have almost complete saturation of their arterial blood with oxygen. 90 – 100 mmHg middle age 60 – 85 mmHg persons over 60Severe fatal hypoxia occurs when oxygen

tension falls to below 40 mmHg

terms to know• A number of terms apply somehow to

asphyxia, some of which are confusing and inexact:– Suffocation – the general term used to indicated death

from lack of oxygen– Smothering – (more specific) indicates blockage of the

external air passages– Gagging – fabric or adhesive tape occludes the external

passages– Choking – refers to blockage of the upper air way– Throttling – refers to strangulation usually by hand– Strangulation – is the most specific term indicating the

use of either the hands or ligature as a means of applying external pressure to the neck

Mechanical Asphyxia• There have been reported cases

where a violent struggle occurs between arresting officers and a drunken or drugged offender in which the death occurs later.

• The death is obscure and almost untraceable at autopsy but has been described as catecholamine-induced cardiac arrhythmia from an exaggerated adrenal response.

Classic Signs of Asphyxia• certain sings have become known as the

“classic sins of asphyxia • A pathologist needs to realize that little

reliance can be placed on them in the absence of other confirmatory evidence.

• In many cases of undoubted asphyxia these signs are absent and, conversely, they are often present in some degree in deaths that can be shown to be non-hypoxic in nature.

• In other words, each of the signs must be looked at IN DEPTH during autopsy.

Classic Signs of Asphyxia • Petechial Hemorrhages

– Small pin-point collections of blood lying in the skin, sclera or conjunctivae and under the thoracic serous membranes.

– A common misnomer is that they occur from the rupture of capillaries, when they in fact come from rupture of venules. (ruptured capillaries would be invisible to the naked eye)

– Most commonly seen of the face and eyes.

– Also known as Ocular Petechiae

Significance of Petechiae• Remember, the appearance of

Petechiae must be noted but not always as an indicator to asphyxia.

• Position of the body after death as well as an enumerable amount of other factors can lead to the appearance of Petechiae.

• Typically, Petechiae are used in conjunction with other evidence to indicated asphyxia.

Petechial Hemorrhages

Classic Signs of Asphyxia• Congestion and edema:

– Even more nonspecific than Petechiae but is also the result of obstructed venous return.

– Congestion of often associated with tissue swelling, and thus can often times be associated with trauma.

– Conditions such as pneumonia will also lead to marked pulmonary edema.

– Drug overdoses are also common causes of raised pulmonary edema

Classical Signs of Asphyxia

• Cyanosis– Cyanosis is derived from the Greek word

for “Dark Blue.”– The color of blood depends on the absolute

quantity of oxyhemoglobin and reduced hemoglobin present in the erythrocytes.

– Constriction of the neck traps venous blood with decreased oxygenated hemoglobin, which leads to the bluish color.

– Cyanosis may be overshadowed by hypostasis.

SuffocationTypically the reduction of oxygen in the

atmosphere by physical replacement by other gases such as carbon monoxide or dioxide.

In domestic circumstances, death may be seen where a heating apparatus has removed oxygen in the absence of ventilation.

In a different variety of hypoxic deaths, children may asphyxiate by being confined in a small air space.

Smothering• This term refers to death from

mechanical occlusion of the mouth and nose.

• Death may occur either by occluding substance pressing down on the facial orifices, or by the passive weight of the head pressing down.

• It is extremely hard to prove intent.• Pressure marks are rarely distinguished

from normal post mortem changes.

“Overlaying” of infants• Condition with a pedigree as ancient

as the old testament.• Mentioned in the book of Kings, in

which two women who claim the same child, as the other infant was overlain.

• The recent decline in SIDS deaths is attributed to mothers awareness of baby position as well as the use of cots and cribs.

Gagging• Variation on smothering where a

pad or gag is fixed over the face.• At first the device admits air, but

as gets soaked with either saliva or mucus becomes impervious and asphyxia occurs.

• Often times related to robbery and violent crimes.

Choking

• Refers to blockage of internal airways.• Usually occurs between the larynx and

primary bifurcation of the main bronchus.

• Foreign bodies account form most choking deaths.

• False teeth and hemorrhages following dental or ear surgeries are common occurrences also.

Blockages

Traumatic Asphyxia• Refers to the mechanical fixation of

the chest.• Important because it shows the most

evident signs of classical asphyxia.• Signs include face and neck grossly

discolored.• Eyes and sclera are engorged with

blood to a point of obliterating the whites of the eyes.

Visible Signs

Traumatic Asphyxia: Case history• A 58-year-old man who had visited an inmate in prison

got into trouble with the prison officers. • The prison warden ordered him to leave the prison, but

the visitor disobeyed this order and assaulted the warden.

• Although the man was immediately arrested for obstructing the warden in the performance of his duties, he reacted extremely violently.

• Therefore, six prison officers immediately restrained him in the prone position.

• According to the statements of the prison officers, the victim lost some of his strength in 1-2 min after being restrained and nearly completely in 7-8 min.

• After about 10 min passed, the victim showed no signs of resistance, yet the prison officers had to keep restraining him following the order of their superiors, who had inspected the situation.

• After 14-15 min had passed, a policeman arrived at the scene and the prison officers relaxed their restraint on the victim. The victim had already undergone cardiopulmonary arrest.

Autopsy Findings: Traumatic Asphyxia

Petechiae observed in theleft upper conjunctiva.

General appearance of the victimshowing obvious congestion of the face.

Autopsy Findings: Traumatic AsphyxiaIntramuscular bleeding in the back of the victim,(a) right scapular region, (b) left infrascapular region.

Autopsy Findings: Traumatic Asphyxia

Multiple fractures of the ribs accompanying the bleeding in the surrounding soft tissues;

(a): right first through fourth ribs and

(b): left first and ninth ribs.

Postural Asphyxia• Closely tied to traumatic asphyxia.• When a person remains in a certain

position long enough to stop respiration.

• Such situations included being trapped, drunken or drugged state, or mechanical impediment.

• Such positions usually entail inversion of at least the upper part of the body.

Postural Asphyxia• Drunk who

attempted to climb through a window above his door when he could not locate his keys. He passed out in this position and died as a result

Mechanism Death by fatal pressure on the neck

Pressure on the neck may arise from manual strangulation, ligature, hanging, direct blows, arm-locks and a variety of accidental lesions.

Strangulation classically was thought of as occlusion of the airway, but now is thought to encompass many factors.

Airway occlusion• Occurs either from direct

compression of the larynx or trachea or from lifting the larynx so that the pharynx is closed by the root of the tongue.

• Various experiments have been done to try to estimate the amount of force needed to close the airway and blood vessels, but it is difficult to translate the varied results.

Occlusion of the neck veins

• Factor most commonly associated with the classical signs of congestion, cyanosis and edema with obvious Petechial hemorrhages.

• Experiments done have show that as little as 2kg of force applied to the neck is enough to destroy the jugular return.

Compression of the carotid arteries

• Much less common than venous occlusion.

• Arteries are typically blocked by the sterno mastoid muscles and thus require much more force to be occluded.

• 4 minutes of carotid artery occlusion is enough to commit brain death.

• Cases with severe hypothermia can extend the time of this occlusion with regards to recovery.

Nerve effects• Pressure on the baroreceptors situated

in the carotid sinuses can result in a condition called bradycardia.– Bradycardia = slowing of the heart.– This mechanism works through a reflex

arch.– Because these impulses are a reflex arch,

the brains need for oxygen is bypassed and the heart slows, significant oxygen reduction can be noted

• Also called reflex cardiac arrest

Photo

Classical features when arrest is delayed

Manual Strangulation• Common method of homicide• Most often associated with power

and size of assailant.• Most commonly seen in domestic

homicides• Also common in sex related

homicides.• Rarely committed by women unless

committed on a child.

Autopsy appearances of MS

• Bruising on the neck

• Abrasions on the neck

Manual Strangulation• Manual

strangulation with bruising from the assailant and fingernail abrasions from the victim. The face is pale as a result of rapid vasovagal cardiac arrest before congestive signs could appear.

Internal appearances in MS

• Bruising may be visible internally• At autopsy, it is critical to release

venous pressure before dissecting the neck to avoid artefactual hemorrhages.

• This is done by excising the jugular after opening the neck.

• Radiography may be performed before the neck is opened.

• Careful layer by layer dissections can then be carried out.

MS bruising

Mucosal hemorrhages

Bleeding behind the larynx

• Bleeding over the front of the larynx is usually genuine if venous pressure was released before dissection.

• The best way to release this venous pressure is incising the jugulars or removing the brain.

• Banding on the esophagus is also a common finding in normal autopsies and not to be confused with strangulation.

Artefactual Post-mortem hemorrhage

Injury to the larynxDamage may occur in many ways

–The superior thyroid horns are often fractured as a result of bi-lateral compression of the larynx.–Fractured hyoid bones are often observed although, in younger subjects, calcification has not fully set in.

Strangulation by ligature• May consist of a wide variety of

objects, some not obviously suited for the purpose.

• Cords, wires, ropes, and some belts are strong enough to cause death.

• A U-shaped ligature is often times sufficient to occlude the airway.

• In the majority of cases the ligature is crossed over itself after passing a full circle around the neck.

Fracture of the left laryngeal horn with a hemorrhage. The body was recovered from a lake based on the confession of the assailant.

External Appearances

Appearance of congestion cyanosed

forehead.

After removal of ligature (scarf) the typical bruises are observed.

The ligature Mark• The appearance at autopsy depends

on the nature and texture of the ligature.

• When there is a pronounced patter such as a weave of a chord pattern abrasions are commonly noted.

• Fabric sometimes leaves marks that are difficult to interpret.

• Fabric may also leave a sharp mark which may be confused for a chord.

Types• Self strangulation

by ligature with three turns around the neck and a complex knot. There was no doubt from the circumstances that the deceased committed suicide.

TypesLigature strangulation

by means of a “Spanish windlass.” A penknife has been thrust through the knot to twist the ligature tight.

Position of the ligature mark

• The geometry of the mark is important to interpret the fatal events.

• In cases of suicide, the ligature typically does not have a “crossover” mark.

• In cases of homicide, the “crossover” is evident.

• The cross may be at the side, front of back depending on the positions of the victim and assailant.

Hanging• Form of ligature strangulation in

which the force applied to the neck is derived from the gravitational drag of the weight of the body or part of the body.

• Total suspension is not needed • Judicial hangings often times saw

victims families pulling on the legs of the victim to shorten the agony.

Suicidal and Accidental hanging

• Today almost all hanging is accidental or suicidal.

• Death is most often cause by reflex cardiac arrest from pressure on the carotid structures.

• This is evident when victims are found with pale faces rather than hemorrhagic congested faces.

Common Methods Used• Most hangings are self suspensions• Typically a thin rope is attached to some

high point.• The lower end is secured to the neck with

some form of slip knot while the victim is standing on a support.

• The support is then removed to suspend the weight.

• Suspension is often times not high enough to keep the victims feet off of the floor.

• The weight of the upper torso leaning into the noose is often sufficient to cause reflexive cardiac arrest.

• Victim who used two neck ties to suspend himself from a hook placed on his door. The hook gave way and he was found lying on the floor dead.

• Notice the pale, uncongested face indicating a rapid cardiac arrest.

Suspension with a fixed knot in the chord so that there is a segment of skin free from the mark where the chord rises toward the knot. This is a common feature in domestic homicides.

• Inmate who had a torn up sheet and attached both ends to a water tap and is leaning into the loop in a sitting position.

A deep hanging mark showing the high position under the chin rising to the back of the neck. The spiral weave of the rope is clearly imprinted in the skin. The dark tint of the face is racial not congestive.

The position of the hanging mark on the neck can vary.

• Top - is the usual position with a fixed noose and high suspension point

• Middle – if a slipknot is used the tightness of the deeply impressed loop tends to find the smallest circumference3 on the neck.

• Bottom – if the suspension point is low, the subject may lean away and the mark can be horizontal.

• Hanging by frontal suspension.

• A leather belt used as a noose.

• Compression has occurred around the whole of the neck

Features of Sexual Asphyxias

• The basic mechanism is the production of cerebral hypoxia.

• This hypoxia is achieved by constriction of the neck by ligature which can be voluntarily tightened and loosened.

• Some procedures use other means for creating hypoxia such as anesthetic agents such as “huffing”

Features of Sexual Asphyxias

• The most common feature is a ligature connected to some compression device of the hands and feet which releases the ligature upon relaxing the legs and hands.

• This feature allows for release in cases where the victim passes out.

• Malfunctions in this release are what lead to accidental ligature deaths.

• Often times hypoxia is produced by position or placing head in a plastic bag.