Drowning Mechanisms and Asphyxia Quiz

Asphyxia

• Asphyxia is the lack of oxygen. It's also characterized by the absence of pulsation, and encompasses any factor interfering with oxygen transfer
• Different types of hypoxia (anoxia) include hypoxic, anemic, stagnant, and histotoxic hypoxia.

Types of Anoxic (Hypoxic) Anoxia

• Ambient: Decreased oxygen content in the atmosphere, such as at high altitudes or in the presence of irrespirable gases (CO2, CO, N2, etc.)
• Central: Depression of the respiratory center, caused by central depressants (like barbiturates), medulla herniation, or electric shock.

Types of Mechanical (Violent) Asphyxia

• Occlusion of respiratory openings (smothering): Blocking the mouth and nose.
• Occlusion of respiratory passages in the neck (strangulation, throttling, hanging): Blocking the trachea in the neck.
• Prevention of respiratory movements (traumatic asphyxia): Compressing the chest and abdomen.
• Internal airway obstruction by foreign body (choking): Blocking the airways from inside by objects.

Anemic Anoxia

• Decreased oxygen-carrying capacity of blood due to:
  • Abnormal hemoglobin (e.g., COHb in carbon monoxide poisoning, methemoglobin in nitrate toxicity)
  • Massive blood loss (hemorrhage)
  • Hemolysis (breakdown of red blood cells) caused by toxins, incompatible blood transfusion, etc.

Stagnant Anoxia (Stagnant Hypoxia)

• Reduced oxygen delivery per unit of time due to interference in blood flow to tissues.
  • Advanced heart failure
  • Vagal or histaminic shock

Histotoxic Anoxia (Histotoxic Hypoxia)

• Diminished ability of cells to utilize oxygen.
  • Cyanide poisoning
  • Exposure to extreme cold

Asphyxial Deaths

• Different degrees of asphyxia result from external factors and internal factors
  • Absence or reduction of oxygen tension in the external atmosphere
  • Obstruction of external respiratory orifices (smothering or gagging)
  • Blockage of internal respiratory passages

Further Details Regarding Asphyxia

• Restriction in respiratory movements (e.g., traumatic asphyxia), or diseases preventing/reducing gas exchange in the lungs (pulmonary edema).
• Reduction in cardiac function that inhibits oxygenated blood circulation
• Limited oxygen transport by the blood in cases of severe anemia
• Issues within the body tissues that hinder the cells' utilization of oxygen (such as cyanide poisoning).

Stages of Mechanical/Violent Asphyxia

Stage 1: Dyspnea

• Physiological response to hypoxia, stimulating the respiratory center.
• Symptoms include dyspnea (forced expiration then inspiration), apprehension, irritability, gasping, and blue lips.

Stage 2: Convulsions

• Cerebral irritation due to anoxia and CO2 accumulation.
• Symptoms like cyanosis, constricted pupils, hypertension, loss of consciousness, protruded tongue, prominent eyeballs. Capillary rupture can result in petechial hemorrhages (Tardieu spots).

Stage 3: Irregular Breathing

• Loss of consciousness characterized by irregular breathing (Cheyne-Stokes respiration), deepening cyanosis, dilated and fixed pupils, hypotension, weak and rapid pulse, arrhythmias, flaccidity of muscles, and loss of reflexes.
• Death often occurs within 5 minutes.

Classical Signs of Asphyxia: Petechial Hemorrhage

• Small pin-point collections of blood under skin, sclera, conjunctiva, and thoracic membranes.
• Vary in size (millimeters - 2 cm)
• Tardieu's spots relate to petechial hemorrhages restricted to the visceral pleura.
• Bleeding originates from small venules, not capillary rupture.

Other Signs of Asphyxia

• Congestion and edema: Swelling and redness of the face, lips, tongue, and internal organs.
• Cyanosis: Bluish discoloration due to reduced hemoglobin levels (absolute amount, not proportion).

Suffocation

• Death caused by reducing oxygen in the inhaled air (e.g., cabin failure in high altitudes, fires).

Smothering

• Mechanical blockage of the nose and mouth. Examples include; overlaying infants, sudden infant death syndrome (SIDS), and plastic bag suffocation.

Choking

• Blockage of the internal airways (pharynx to trachea).
  • Causes include foreign bodies, dentures, acute obstructive lesions (e.g., diphtheria, epiglottitis), aspiration of vomit, etc.
  • Can lead to pure asphyxia (signs of congestion and petechiae) or neurogenic cardiac arrest.

Traumatic Asphyxia

• Mechanical compression of the chest and abdomen. Examples are crushing in crowds.

Postural Asphyxia

• Extended period of remaining in a specific position that restricts venous return to the heart; trapped individuals or those in states like drunkenness or drug use.

Fatal Pressure on the Neck

• Common in forensic practices. Pressure causes airway occlusion, compression of veins, pressure on arteries, resulting in vagal cardiac arrest.

Manual Strangulation (Throttling)

• Common homicide method, often seen in domestic killings (husband-wife), sex crimes, and child abuse.
• Rarely performed by a woman (except on children), and men rarely strangle men of equal strength.
• Autopsy findings could show signs of bruising and abrasions, bruising marks, fingernail/linear scratches, fractured hyoid bones, and superior thyroid horn fractures.

Strangulation by Ligature

• Mostly homicidal.
• The ligature encircles the neck horizontally, lower than in hanging.
• Often has a crossover point.
• Hyoid bone fracture less common than in manual strangulation.

Hanging

• Ligature strangulation with the force deriving from the weight of the body or part of the body pulling on the neck (e.g., using ropes -judicial hanging).
• Usually associated with complete suspension/dislocation of the cervical spine, leading to spinal cord traction, or brain stem disruption.
  • complete vs. incomplete hanging, and its implications on the point of suspension as reflected in the skin marks.

Accidental Hanging

• Can occur in sexual asphyxia cases (auto-erotic or masochistic), or in children.

Drowning

• Prevention of air entering the lungs due to submersion in water or other fluids.
  • Can be accidental (fishermen, bathers, etc.), suicidal (common amongst females), or homicidal (rare).

Drowning Pathophysiology

• Water inhalation causes absorption into the bloodstream, electrolyte imbalances, and various accompanying effects. Death can occur within 2-5 minutes of complete submersion.

Drowning Mechanisms of Death

• Fresh water: Large water volume leads to hemodilution (reducing sodium, increasing potassium), hemolysis (red blood cell rupture), circulatory overload, potentially hyperkalemia, ventricular fibrillation, and death 4 to 5 minutes.
• Salt water: Water in the lungs causes severe edema and creates a hypertonic environment. The result is reduced blood volume (hemoconcentration), hypovolemia, shock, and subsequent asphyxia. Death may take 10 to 12 minutes to develop.

Drowning Phases

• Submersion: Struggle, leading to exhaustion.
• Breath holding: Continued until carbon dioxide builds up, stimulating breathing, followed by inhalation of water.
• Gulping of water: Coughing and vomiting, followed by loss of consciousness.
• Unconsciousness and convulsions: Further involuntary respiratory movements, and water aspiration. Respiratory failure can come before or after cardiac failure. Death commonly occurs within 2-3 minutes (though some longer periods of submersion result in some survival).

Postmortem Drowning Findings

• Face and conjunctiva congestion
• Fine froth (may contain blood), due to the water-air mixture, present in the nose and mouth.
• Goose skin (cutis anserina). Peeling skin, and wrinkling of hands from prolonged immersion.
• Stomach may contain water, mud, or algae for evidence (diatom tests— useful in differentiating true drowning from other submersions or simulated events).

Mechanisms of Death in Drowning

• Direct causes: Immediate death due to mechanical anoxia or hypothermia.
• Indirect causes: Reflex cardiac inhibition (e.g., from cold water), traumatic injuries
• Secondary drowning (post-immersion syndrome): Survival after initial submersion episode, resulting in complications like edema, inflammation, and potential pulmonary problems like pneumonia.

Test your knowledge about the mechanisms of death associated with drowning, including the effects of hemolysis, vagal stimulation, and different kinds of hypoxia. This quiz covers a range of critical concepts including secondary drowning and conditions leading to various types of asphyxia. Dive into these complex physiological processes and solidify your understanding!