Asphyxia is defi ned as an interruption of any stage of the supply or transport of oxygen between the environment and the organs.
This can occur by obstructing the airways or respiration in general, the oxygen-transporting medium blood, blood circulation, and the environment.
Classification
Distinction is made between external and internal asphyxia.
External Asphyxia
Occurs when oxygen is unable to reach the pulmonary alveoli due to insuffi cient atmospheric oxygen.
Generally insuffi cient levels of atmospheric oxygen (environmental asphyxia).
Obstruction of respiratory excursions of the chest (e.g., burking or positional asphyxia).
Obstruction of the afferent airways due to external mechanical compression (e.g., manual strangulation) or obturation (e.g., food aspiration or “bolus death”).
Signs of external asphyxia include:
Facial congestion and cyanosis.
Petechiae in the facial skin and conjunctivae.
Reddening and swelling of the base of the tongue and pharyngeal wall.
Rapid and intensive onset of dark blue-violet livor mortis.
Internal Asphyxia
Occurs when atmospheric oxygen supply and transport to the pulmonary alveoli are intact, but oxygen–hemoglobin binding and/or the delivery of hemoglobin-bound oxygen to the organs and tissues is impaired.
Carbon monoxide or cyanide poisoning.
Signs of internal asphyxia include:
Hyperemia of internal organs.
Small bloodless spleen.
Pulmonary hyperinflation.
Dilatation of the right ventricle.
Ecchymosis beneath the serous membranes of the visceral pleura (Tardieu spots when occurring beneath the pleura).
Fluidity of postmortem blood due to increased fibrinolysis.
Vacuoles and fat droplets in hepatocytes, blood extravasation into the heart, kidneys, and liver, as well as ganglion cell necrosis (depend on the type and duration of the mechanism causing death).
Important Note
None of the signs of asphyxia in internal organs is conclusive for asphyxia, and they merely have indicative value.
Key Terms
Dyspnea: Diffi culty in breathing, respiratory distress.
Apnea: Respiratory arrest.
Hypoxia: Diminished oxygen concentration in blood, organs, and tissues.
Ischemia: Restricted blood supply, resulting in lack of oxygen and increase in carbon dioxide and lactate levels.
Mechanical Trauma Involving Occlusion of Airways
Occluding the external airways with a soft cover.
Aspiration of fluids, including water (drowning) or blood (skull base fracture with loss of gag reflexes).
Aspiration of solid material resulting in airway occlusion (e.g., sand after submersion in sand).
Placing a tightly fitting plastic bag over the head.
Foreign body airway obstruction (“bolus death”).
External obstruction of respiratory excursions of the chest and simultaneous airway obstruction (“burking”).
Death due to positional asphyxia, particularly in individuals in a highly excited state or following drug abuse (excited delirium).
Gagging, i.e., introducing a foreign object into the mouth and throat.
General Pathophysiology of Asphyxia
External asphyxia refers primarily to an interruption in external oxygen supply, including lack of oxygen in small enclosed spaces, inhalation of gases, and high-altitude death.
Associated with hypercapnia and dyspnea.
Hypoxic asphyxia occurs when carbon dioxide can still be inhaled, leading to a final reduction in respiratory drive, an euphoric state, and an acute loss of consciousness.
The process of asphyxia typically lasts 3–5 min, subdivided into several phases lasting 1–2 min each, but can last longer depending on the pathomechanism.
Findings may include petechiae in the sclerae, conjunctivae, face, and oral mucosa on external autopsy examination and beneath the serous membranes above the diaphragm and petechiae on internal autopsy examination.
Strangulation may also lead to congestive petechiae and fine hemorrhages on the inner surface of the epicranial aponeurosis and in the temporal muscles.
Particular Constellations in Asphyxial Deaths
Autopsy findings are insufficiently characteristic and need to be consistent with a concrete sequence of events to determine asphyxial deaths.
Positional Asphyxia (Physical Restraint)
Fatalities in abnormal physical positions that cause constriction of breathing and cardiac circulation.
Restraint asphyxiation in excited delirium is seen in police custody, hospitals, etc.
Includes death in an upright position, on hyperflexion of the neck and obstruction of the airways, in a head-down position, and in a crucifixion position.
Compression of the chest can occur with accidents in wheelchairs.
Acute cardiac and respiratory arrest may ensue, particularly following prior cocaine and amphetamine consumption along with catecholamine release.
Risk Factors and Symptoms
State of high excitement.
Significant alcohol and/or drug intoxication.
Restraint in a prone position.
Respiratory obstruction due to partial occlusion of the airways or constriction of respiratory excursions of the chest.
Massive perspiration and increased body temperature.
Strong respiration with the mouth opened widely and unusual respiratory sounds.
Abrupt cessation of resistance.
Pallor or bluish skin discoloration, impaired consciousness, convulsions, and involuntary defecation, urination, or increased salivation.
Important Considerations for Police and Medical Personnel
Once actual restraining measures have ceased, highly excited detainees should be immediately moved out of a prone position into a lateral or upright position.
Vital parameters should be closely monitored and potential preexisting conditions such as heart damage and hypertension should be considered.
Police trainees should be educated on risk factors and preventive measures.
Physicians should be appropriately qualified and call for measures to reduce the risk of positional asphyxia and encourage appropriate monitoring.
Autoerotic Accidents
These cases are clearly of an accidental nature where Victims are generally alone and certain circumstances can be reconstructed that indicate a mechanism of sexual gratification
Attention should be paid to paraphernalia indicating exhibitionistic, masochistic, or sadistic tendencies; transvestite, and fetishistic components.
Bondage may include “hog-tying” in either a horizontal or vertical position.
Pornographic material, nude photographs, women’s erotic underwear, or apparatus for the purposes of self-photography are frequently found.
Aspiration
Foreign material aspiration can cause partial or complete airway displacement and can be detected microscopically in the peripheral bronchi.
Impaired swallowing and gag reflexes, either due to alcohol intoxication or neurological deficit following craniocerebral trauma, often represent a causal factor.
Gagging
A subtype of asphyxia caused by forcing a foreign object into the mouth and throat, displacing the nasopharyngeal space.
Cases of self-gagging are seen in the context of autoerotic activity or with suicidal intent.
Cases where the gag has been removed following death small injuries to the mouth region may support the suspicion of gagging.
Finding in Gagging victims
Distinct signs of asphyxial suffocation are usually found: petechiae, hemorrhages in the auxiliary respiratory muscles and at the base of the tongue, as well as facial congestion.
Perioral abrasions and gag marks at the corners of the mouth and on the cheeks may be visible.
In other cases, the gagging material is chosen spontaneously, such as grass and leaves.
Other Forms of Asphyxia
Placing a Plastic Bag over the Head: The anoxic asphyxia occurs following oxygen consumption with a low dead-space volume of air in the plastic bag.
Exit bags are considered by the disabled community as a threat to the lives of care-dependent individuals (criminal offense in some countries).
Death Caused by obstructing the airways primarily occurs when the perpetrator is physically stronger than his/her weak victim with no, or only discrete, fi ndings of asphyxia
Bolus Death: airways with asphyxial suffocation or reflex cardiac arrest (vasovagal reflex evoked by stimulation of the autonomic nerve plexus of the laryngeal inlet).
Heavy intoxicated individuals as well as craniocerebral trauma patients commonly affected.
Thoracic compression and fixation, usually in an expiration position, Rapid compression related produces copious dense petechiae.
Burking: The physically stronger perpetrator obstructs respiratory excursions obstruction by obstruction external airways.
The composition of air at approximately 21 % O 2 , around 78 % N 2 (+ noble gases), and 0.03 % CO 2 barely changes pressure up to an altitude of 100 m.