ASPHYXIA
Outlines
INTRODUCTION
PATHOPHYSIOLOGY
ETIOLOGY
I. mechanical
ii. Pathological
iii. Toxic or chemical
iv. Environmental
V. traumatic
vi. Positional
vii. Iatrogenic
CLASSIFICATION: physical- choking, aspiration, smothering, strangulation, drug overdose, birth asphyxia, seizures
: Chemical – carbon monoxide, cyanide, hydrogen sulphide
CLINICAL FEATURES: Tardier’s spot, voiding of urine, stool, etc
Introduction
Asphyxia is the condition where the body either doesn't get enough oxygen to continue normal function or has too much carbon dioxide to function properly. Without adequate oxygen, nerve cells in the brain begin to die in about 2-4 minutes, and cell death is irreversible. It is a condition caused by interference with the exchange of oxygen and carbon dioxide in the body. Asphyxia literally means ‘defective aeration of blood ‘due to any cause.
Pathophysiology of Asphyxia
Interference between inspired air and lungs or decreased oxygen in the inspired air due to various etiologic factors, which are discussed below, will cause reduced amount of oxygen reaching the lungs which means less blood will be oxygenated i. e. oxygen tension in blood will be low. Body tissues will receive less oxygen so there will be accumulation of carbon dioxide and ATP break down products. These causes capillary dilation and increased permeability which causes pooling of blood and tissue congestion. Due to pooling of blood, venous return will be less to the lungs so that less blood will be available for oxygenation causing asphyxia.
Etiology of Asphyxia
It can be:
i. Mechanical/violent: Mechanical interference to the passage of air into the respiratory tract by Closure of the external respiratory orifices by closing the nose and the mouth (e.g. smothering). Closure of the air passages by external pressure
On the neck (e.g. hanging, strangulation and throttling), or impaction of foreign bodies (e.g. gagging and choking). Occlusion of the respiratory tract and lungs by
fluid (e.g. drowning). Pressure on the chest in a stampede or collapse of a building (e.g. traumatic asphyxia).
ii. Pathological: Entry of oxygen to the lungs is prevented by disease of the upper respiratory tract or lungs, e.g. laryngeal edema, spasm, tumors or abscess.
iii. Toxic or chemical: Cessation of the respiratory movements due to paralysis of the respiratory center in poisoning with morphine, barbiturates or strychnine. Inhibition of oxidative processes in the tissue preventing the use of oxygen in the
blood, e.g. cyanide poisoning.
iv. Environmental: Breathing in vitiated atmosphere, as in high altitude, climbing or flying, or inhalation of carbon monoxide (CO), sewer gas or pure helium.
V. Traumatic: Blunt trauma to the thorax may result in pneumothorax, hemothorax or pulmonary embolism that will interfere with oxygenation and ventilation by compressing otherwise healthy parenchyma.
vi. Positional/postural: Positional asphyxia is due to abnormal body position that prevents adequate gas exchange. In alcoholics or addicts, where the person is unconscious and the upper portion of the body is lower than rest, or neck is forcibly flexed on the chest which prevents normal respiratory movements. Deaths in such cases are diagnosed based on circumstantial evidence in combination with excluding other significant underlying causes of death. Positional/restraint asphyxia may occur in hogtying (individual is placed in a prone position, their hands are cuffed together behind their back, and their ankles are bound and tied to their wrists).
vii. Iatrogenic: It is seen during anesthesia
Classification
It is proposed to classify asphyxia in forensic context in four main categories: suffocation, strangulation, mechanical asphyxia, and drowning. Suffocation subdivides in smothering, choking, and confined spaces/entrapment/vitiated atmosphere. Strangulation includes three separate forms: ligature strangulation, hanging, and manual strangulation. As for mechanical asphyxia, it encompasses positional asphyxia as well as traumatic asphyxia.
Physical Asphyxia
One type of asphyxia is called "physical” or "mechanical."It happens when a force or object keeps you from breathing.
Lots of accidents can lead to it. Some examples of physical asphyxia are:
Choking. This is when food or an object gets stuck in your airway and blocks air from getting to your lungs. The elderly have a greater chance of this happening to them, especially those who live alone, wear dentures, or have trouble swallowing. Babies and toddlers also have higher odds of choking on large pieces of food or things they put in their mouths.
Aspiration. It's different from choking. Aspiration happens when something you eat or drink "goes down the wrong pipe “and enters your airway or lungs. The substance crowds out the air in your body. Drowning is the most common type of aspiration.
Suffocation (smothering). Suffocation happens when something heavy covers the face or chest and prevents you from breathing. It also occurs when you are in a place where oxygen runs out, such as a closed-in, airtight space.
Strangulation. If a cord or rope or other object long enough to go around your neck presses on the airway, it blocks air from getting to your lungs.
Drug overdose. Opioids affect your breathing. When you take too high a dose, it can slow down your breathing to the point that your body does not take in enough oxygen.
Birth asphyxia. Sometimes, an unborn child may get too little oxygen during pregnancy. This might happen, for example, because of a lack of oxygen in the mother's blood, or problems with the placenta. During delivery, the baby can also not get oxygen because of umbilical cord problems or a long labor.
Seizure. It can cause asphyxia in several ways. Epileptic seizures may make your breathing suddenly pause (also called apnea), and lower oxygen in your body to life-threatening levels. Also, during a seizure, your body may move in such a way that your airway gets covered, blocking your breathing.
Illnesses or injuries, like heart failure, a broken neck, or an allergic reaction that causes airways to swell and close, can also cause physical asphyxia.
Chemical Asphyxia
Another type of asphyxia is called "chemical."In this type, a chemical keeps oxygen from reaching your cells.
Chemicals that can cause asphyxia include:
Carbon monoxide. This is a colorless, odorless gas that comes from burning different types of fuel. If you breathe in too much of it, the gas builds up in your body and replaces the oxygen in your blood.
Cyanide. It keeps cells from taking oxygen in. You're at risk of cyanide poisoning if you breathe smoke during a fire, have contact with certain industrial chemicals, or work in jobs like mining or metalworking.
Hydrogen sulfide. This gas smells like a rotten egg. It can come from sewage, liquid manure, sulfur hot springs, and natural gas. If you breathe in too much, it can prevent oxygen from entering your cells, much like cyanide does.
Examples of injuries or illnesses that can cause asphyxiation can include: Collapsed lung, Inhalation of toxic fumes (like carbon monoxide), Whooping cough, Diphtheria (bacterial infection), Croup, Heart failure, Swollen veins in the head or neck, Paralysis, Asthma, Broken neck, High blood pressure, Allergic reaction, Sleep apnea, Drug overdose
CLINICAL FEATURES
Asphyxia can lead to unconscious, loss of muscle power which causes capillary stasis and engorgement that increases intracapillary pressure. Asphyxia decreases oxygen tension and reduces Hb which leads to cyanosis and congested viscera. Asphyxia also damages capillary endothelium and increases capillary permeability. Increased intracapillary pressure and congested viscera rupture the capillaries. The ruptured capillary along with increased permeability will lead to Tardieu’s spot. Asphyxia also causes sphincters relaxation which causes voiding of urine, stool, semen