SUFFOCATION : ASPHYXIA

Author: Dr. J.A.J. Ferris

 

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.

 

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.

 

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.

 

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.

 

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.

 

 

DEFINITION

 

The physiological definition of "asphyxia" is complex and often means more than hypoxia.  In the field of forensic pathology, asphyxia is considered to be a consequence of a struggle to breathe against some mechanical interference with respiration.

 

General Autopsy Findings in Asphyxial Deaths:

 

The following are general findings in death by asphyxia.  Their prominence will vary with individual cases and petechial hemorrhages, in particular, may be completely absent, or extremely rare.  It is also important to note that all of the findings in asphyxial deaths may be found, on occasion, in other circumstances.

 

1.             Pulmonary edema, with froth in trachea and bronchi.

2.             Bulky, crepitant and over‑distended lungs.

3.             Right ventricular dilatation.

4.             Petechial hemorrhages on the conjunctival and facial tissue, usually above the level of the airway obstruction in strangulation cases.

 

Suffocation

 

Suffocation results from the mechanical obstruction to the entry of air into the lungs by obstruction of the external respiratory orifices.  Common agents used are plastic bags, soft pillows, or soft materials used to occlude the mouth and nostrils.

 

Smothering can be homicidal, suicidal, or accidental.  In homicidal suffocation, there is usually considerable physical disparity between the assailant and victim, or the victim is debilitated by drugs or injury.

 

Scene investigation may not be helpful.  Some cases of Sudden Infant Death Syndrome have been erroneously attributed to overlying by the mother.

 

The autopsy findings are subtle and injuries may be completely absent.  Examination of a suicidal death by suffocation with a plastic bag usually reveals moisture on the face and on the inner surface of the bag.

 

In homicidal suffocations, there may be fingernail scratches, or bruises to the face, or tears to the buccal mucosa.  There may be marks associated with use of a tape or a gag.  If neck compression does not occur, petechial hemorrhages may not be found.  The diagnosis of suffocation may be impossible to establish with certainty on the basis of the postmortem examination alone.


 

Upper Airway Obstruction (Choking)

 

The usual mechanisms of asphyxia in choking are mechanical obstruction of the airway, usually involving the pharynx, larynx and trachea.

 

The most common situation is the so‑called "cafe coronary".  Victims are usually intoxicated, or have pre‑existing neurological debilitation.  Choking occurs suddenly while eating.  The obstructing foreign body may be removed prior to autopsy.  Children may choke on small toy objects, nuts or grapes.

 

The vast majority of choking deaths are accidental.  Suicides and homicides occur very rarely.

 

Inhalation, or aspiration, or gastric contents as a primary event is extremely unusual.  When aspiration occurs, drugs, such as alcohol, a head injury, or serious neurological disease process should be sought.  Significant aspiration of gastric contents during an epileptic seizure is relatively unusual.

 

The autopsy findings in choking, again, may be subtle, particularly if the occluding object has been removed.  Petechiae may be present if significant retching has occurred.  There may be injuries to the buccal mucosa, related to resuscitation.  The right ventricle of the heart is dilated and the lungs hyperinflated and possibly edematous.  Inhalation of blood may play a significant accelerating role in trauma cases, such as those associated with facial fractures.  Aspiration is usually the mechanism of death and not the cause of death and a complete autopsy and toxicological examination are necessary to identify these modifying factors.

 

Hanging

 

As in most asphyxial deaths, hanging can be suicidal, accidental, or homicidal, but suicidal hangings are by far the most common.

 

Hanging deaths result from compression of the airway and neck vessels as a result of suspension in such a manner that the force acting on the ligature is that of all or part of the weight of the body.

 

Examination of the scene is important.  The posture, position and method of hanging and ligature used must all be examined and injuries, other than those attributable to hanging, require careful assessment and interpretation.  It is important to remember that complete suspension is not necessary.  In most hanging deaths, the ligature and ligature mark lie above the thyroid prominence, with a point of suspension usually behind one ear.  Frontal knots are unusual.  The appearance of the ligature mark varies with the type of ligature used and with the physical characteristics of the individual neck.  Soft broad ligatures may not leave any recognizable marks.  In most cases, the ligature does not completely encircle the neck.

 

Successful hanging can be accomplished in a variety of positions, including a semi‑reclining sitting or lying position.  The only requirement is for sufficient sustained pressure to be applied to the neck.

 

The findings at autopsy and hanging include the ligature mark, which is usually abraded and parchmented and may, depending on the ligature used, show specific patterning.  The deepest furrow is opposite the point of suspension and fades as it approaches the knot.  Scratches, in relation to the ligature mark, with the appearance of fingernail scratches, should be documented and investigated.

 

Petechial hemorrhages are usually completely absent, when the full weight of the body acts on the ligature, but are present in varying degrees of prominence, when the victim is only partly suspended.  Layered neck dissection usually shows completely absent, or only minimal, bruising into the soft tissue.  Dissection of the carotid arteries may show occasional linear traction type tears.  Fractures of the vertebrae do not occur unless there is a significant drop, such as a judicial hanging.

 

Accidental hangings are far more common in children, than in adults.  They are frequently the result of articles of clothing caught up in machinery.

 

Auto‑erotic asphyxial deaths usually involve males and occur in isolated or secluded sites.  There may be evidence of transvestitism, bondage, mirrors, cameras, etc.

 

Ligature and Manual Strangulation

 

Strangulation results when the application of a constricting force to the neck is such that the force exerted is other than that of the weight of the body.  The two types of strangulation include manual strangulation and strangulation by ligature.  The victims are usually women, children, or the elderly.  Ligature suicides can occur, but the ligatures must be fashioned in such a manner that the pressure on the neck is maintained after loss of consciousness.

 

At autopsy, in cases of ligature strangulation, the ligature mark is usually horizontal and crosses the neck in the region of the lower end of the thyroid cartilage.  Particularly with ridges on thin ligatures, a furrowed mark will be evident.  Large bulky ligatures may not leave any surface evidence of injury to the neck.  Petechial hemorrhages to the face and conjunctiva are usually prominent, as are the usual signs of asphyxia in the lungs and heart.  A layer by layer dissection of the neck should be performed, with the neck incision extending up to the level of the mastoid processes.  Serial photographs should document the distribution and pattern of bruising to the soft tissue and muscle.

 

Pure ligature strangulation is relatively uncommon and there is usually an associated manual component.  Consequently, fractures of the hyoid and thyroid are seen, due to compression of these structures against the cervical vertebrae.  Other associated injuries should be carefully sought for and documented, such as scratches to the face, or neck, or bruising to the extremities.  Evidence of an associated sexual assault should also be sought.  Decomposition may render marks difficult, or impossible, to recognize.

 

Mechanism of Death in Neck Compression

 

In hanging, unconsciousness is rapid, due to obstruction of circulation to the brain.  Significant obstruction of the carotid arteries can occur with a tension of approximately ten pounds.  Vascular obstruction is the main mechanism, leading to death with neck compression.

 

In ligature and manual strangulation, incomplete carotid occlusion is expected to occur and the struggle may continue for a period of time.  This accounts for the injuries and petechial hemorrhages evident at autopsy in strangulation cases.  As in all cases of neck compression, the rapidity of death can be effected by susceptibility of the victim to carotid sinus stimulation.  Neck holds used by the police may be extremely dangerous and there is some evidence that cocaine intoxication increases susceptibility to sudden cardiac arrest from vagal inhibition.

 

Crush or Traumatic Asphyxia

 

These situations occur when external compression of the chest prevents effective respiratory moments.  These deaths are almost always accidental and occur in situations, such as pinning of the victim beneath an overturned car, or in crowds or mob panics.  In this category also falls the procedure, "burking".

 

At autopsy, there is evidence of severe congestion and cyanosis above the level of compression frequently with a sharp line of demarcation.  Petechial hemorrhages are prominent and may be confluent above the point of compression.  There may be associated sternal, or spinal, fractures and interstitial emphysema.

 

Positional Asphyxia

 

Position alone can cause death.  Victims suspended upside down in industrial accidents may die as a result of the effects of the abdominal organs compressing the diaphragmatic movement necessary for respiration.  Acute positional flexion of the neck in a deeply intoxicated individual may result in hypoxia and subsequent death.

 

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