According to Adelson, asphyxia is a state in a living organism in which there is an acute lack of oxygen available for cell metabolism associated with the inability of the body to eliminate the excess of carbon dioxide. The supply of oxygen to the blood and body tissues is reduced below the normal working level due to interference in the process of respiration. The three main stages of asphyxia are Stage of Dyspnea, Stage of Convulsion, Stage of Exhaustion, and respiratory failure.
Asphyxia is considered a state in which hypoxia and hypercapnia happen. Hypoxia of the tissue means the lack of supply of oxygen to the body and hypercapnia means the increased level of carbon dioxide retention in the blood and tissues. The other two terms usually used along with asphyxia are anoxia which means lack of oxygen supply to the body and tissues and hypoxia which is a condition in which there is an inadequate or reduced supply of oxygen to tissues.
Once asphyxia sets in, it causes anoxia and then a vicious cycle of asphyxia sets in. As the oxygenation of blood decreases asphyxia leads to capillary dilation, engorgement, and stasis of blood. This results in a decrease in venous blood flow and therefore a decrease in the pulmonary flow of blood.
All of these reduces the level of oxygenated blood in the lungs. The normal oxygen content of the arterial blood with 90% saturation of Hb ranges from 90-100 mm Hg. When it reduces to 60 mm Hg, it will cause hypoxia. Severe hypoxia happens at a level of 40 mm Hg and 20 mm Hg that leads to the death of a person.
Types of Asphyxia
Mechanical Asphyxia: This is caused due to the restriction of the flow of air into the body by mechanical means like smothering, gagging, choking, hanging, or strangulation.
Traumatic Asphyxia: This is caused by pressure and fixation of the chest and abdomen. Stampede, person crushed under a vehicle, person crushed by fall of a wall or building collapse or earthquake, pneumothorax due to penetrating injury to the chest can be the various traumatic causes.
Environmental Asphyxia: This is due to lack of oxygen in the environment like at places of high altitude, a person trapped in well or granary, respiration in enclosed space.
Toxic Asphyxia: This type of asphyxia happens due to the intake of any poisonous substance like opium, carbon monoxide, cyanide, gelsemium.
Pathological Asphyxia: Pathological causes such as consolidation, pleural effusion, acute edema of glottis or any such presence of disease in the respiratory passage or inside the lung prevents oxygenation cause asphyxia.
Signs and Symptoms
The specific signs and symptoms of asphyxia include Cyanosis, Congestion of organs, Petechial Hemorrhages, Pulmonary Edema. The non-specific signs are Fluidity of Blood and Dilation of Right Chamber of the heart.
Cyanosis: It indicates the bluish coloration of the skin or the mucous membrane. It can be seen prominently in regions with abundant capillary and venous circulation like the lip, tip of the nose, nails, earlobes and tip of the tongue. The reduced hemoglobin causes the dark coloration of the blood. There must be at least 5 gm of reduced hemoglobin per 100 mL blood before cyanosis becomes evident. In situations where the dermis is dark, marked anemia, cyanosis may not be evident. The signs of cyanosis should not be confused with postmortem lividity.
Congestion of Organs: Hypoxia will cause decreased oxygen tension in blood, reduced hemoglobin and capillary dilation, engorgement, and stasis of blood. The stasis of blood in the capillaries will cause the congestion of organs.
Pulmonary Edema: It is the condition where there is an excess of fluid accumulation in the lung alveoli due to the increased pulmonary pressure and associated anoxia.
Petechial Hemorrhages: It is the small-point collection of blood that will vary in size from a tenth of a millimeter to about two millimeters. If it is more than two millimeters, then it is called ecchymoses. This is caused by an acute rise in the venous pressure which causes over-distention and rupture of thin-walled venules in the lax tissue, eyelids, pleura epicardium.
Fluidity of Blood: Earlier it was considered that anoxia/hypoxia will cause the release of fibrinolysin enzymes from the vessel wall resulting in the fluidity of the blood.
The purpose of breathing is to convey oxygen from the atmosphere into the lungs and remove carbon dioxide but when this process is arrested, it will cause asphyxia. Mild cases of asphyxia can be treated, but when asphyxia happens due to mechanical or traumatic reasons it results in the death of the person.