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 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.
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
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
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.
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.
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.
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.
“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.
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.
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.
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.
Autopsy Findings: Traumatic Asphyxia Petechiae observed in theleft upper conjunctiva. General appearance of the victimshowing obvious congestion of the face.
Autopsy Findings: Traumatic Asphyxia Intramuscular 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
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.
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.
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.
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 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.
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.
Types Ligature 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.