Mechanical asphyxiation is a medical event where breathing ceases due to a physical obstruction or compression of the respiratory system. It involves an interruption of oxygen supply. It interferes with the ability to inhale and exhale air. Understanding this event involves recognizing the physical forces that cause it.
Defining Mechanical Asphyxiation
Mechanical asphyxiation occurs when the body is deprived of oxygen as a result of physical interference with breathing. The term “mechanical” signifies that an external force or physical obstruction directly prevents air from reaching the lungs or restricts their ability to expand and contract. This physical disruption distinguishes it from other forms of oxygen deprivation.
For instance, chemical asphyxiation involves substances that interfere with oxygen uptake or utilization at a cellular level, such as carbon monoxide replacing oxygen in the blood. In contrast, mechanical asphyxiation is concerned with physical impediments to respiration.
How Mechanical Asphyxiation Occurs
Mechanical asphyxiation manifests through several distinct physical processes that disrupt normal respiration. One mechanism involves the obstruction of airways, where something physically blocks the mouth, nose, or throat, preventing air from entering the respiratory tract. This can be an object, a person’s hand, or internal swelling that closes off the air passages.
Another way mechanical asphyxiation happens is through external compression of the airways or chest. Pressure applied to the neck can compress the trachea, blocking the flow of air, or it can compress blood vessels, reducing oxygen supply to the brain. Similarly, pressure on the chest or abdomen can prevent the diaphragm and rib cage from moving adequately, hindering lung expansion and air intake.
A third process involves the restriction of respiratory movements, where physical constraints prevent the chest wall or diaphragm from functioning properly. This often occurs when the body is held in a position that limits the natural expansion and contraction needed for breathing. Such restrictions can make it impossible to inhale or exhale sufficient air, even if the airways themselves are clear.
Common Forms of Mechanical Asphyxiation
There are several common scenarios in which mechanical asphyxiation can occur, each involving specific physical interactions that impede breathing. Strangulation involves external compression of the neck, often by hands, a ligature, or another object. This pressure can obstruct both the airways and blood vessels.
Suffocation refers to the blockage of external airways, such as the mouth and nose, or the prevention of air from entering the lungs. This can happen if a person’s face is covered by an object like a pillow or plastic bag, or if they are in an airtight space where oxygen is depleted. Choking, by contrast, is caused by an internal obstruction of the airway, when food or a foreign object becomes lodged in the throat. This prevents air from reaching the lungs.
Traumatic asphyxia results from intense compression of the chest and abdomen due to an external force, such as being crushed under a heavy object or in a crowd. This compression prevents the chest from expanding, making breathing impossible and forcing blood back into the veins of the head and neck. Positional asphyxia occurs when a person’s body position restricts their ability to breathe adequately, often unintentionally. This can happen if an individual is unable to reposition themselves, leading to a compromised airway or limited chest expansion, particularly in situations involving physical restraint or immobility.
Physiological Impact
When mechanical asphyxiation occurs, the body experiences physiological changes due to the lack of oxygen. The most direct consequence is a decrease in blood oxygen levels, known as hypoxia. Simultaneously, the body’s ability to exhale carbon dioxide is impaired, leading to an increase in carbon dioxide levels, termed hypercapnia.
These changes quickly affect the brain, which is sensitive to oxygen deprivation. Within minutes, brain cells can suffer damage, potentially leading to loss of consciousness. Prolonged hypoxia can result in irreversible brain injury. The heart is also impacted, as it struggles to pump oxygen-depleted blood, which can ultimately lead to a reduction in heart function and cardiac arrest.