Suffocation, Asphyxia, and Fatal Pressure on the Neck

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Suffocation, Asphyxia, and Fatal Pressure on the
Neck
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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.

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The Nature of Asphyxia

• The 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.

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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 60
• Severe fatal hypoxia occurs when oxygen tension
  falls to below 40 mmHg

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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

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Classic Signs of Asphyxia

• certain signs have become known as the classic
  signs of asphyxia
• A pathologist needs to realize that little
  reliance can be placed on them (petichia) 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.

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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

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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.

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Petechial Hemorrhages
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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

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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.

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Suffocation

• Typically 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.

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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.

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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.

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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.

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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.

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Blockages
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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.

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Visible Signs
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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.

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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.

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Autopsy Findings Traumatic Asphyxia
General appearance of the victimshowing obvious
congestion of the face.

• Petechiae observed in theleft upper conjunctiva.

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Autopsy Findings Traumatic Asphyxia

• Intramuscular bleeding in the back of the victim,
• (a) right scapular region,
• (b) left infrascapular region.

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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.
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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.

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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

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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.

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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.

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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.

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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.

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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

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Photo
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Classical features when arrest is delayed
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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.

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Autopsy appearances of MS

• Bruising on the neck
• Abrasions on the neck

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Manual Strangulation with Decomposition present
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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.

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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.

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MS bruising
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Mucosal hemorrhages
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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.

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Artefactual Post-mortem hemorrhage
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Injury to the larynx

• Damage 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.

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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.

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

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

• Appearance of congestion cyanosed forehead.

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The ligature Mark

• The appearance at autopsy depends on the nature
  and texture of the ligature.
• When there is a pronounced pattern 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.

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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.

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Types

• Ligature strangulation by means of a Spanish
  windlass. A penknife has been thrust through
  the knot to twist the ligature tight.

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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.

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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.

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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.

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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.

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• 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.

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• 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.

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• 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.

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• 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.

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

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• Hanging by frontal suspension.
• A leather belt used as a noose.
• Compression has occurred around the whole of the
  neck

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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

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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.

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Auto Erotic Asphyxia
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Auto Erotic Asphyxia
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Auto Erotic Asphyxia
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Auto Erotic Asphyxia
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The End Test Tomorrow