Carbon monoxide (CO) is an insidious gas and is produced as a result of combustion of a carbon-containing material. Many people suffer carbon monoxide poisoning due to the lack of visual colour, taste, odour and the absence of a sensory effect caused by this particular gas. CO is one of the most deadly and deceptive of the asphyxiating gases forensic toxicologists have to work with. Many top forensic science colleges in Nashik focus on training students to better-understand the impact of carbon monoxide poisoning in forensic science.
A major cause of accidental death worldwide is carbon monoxide poisoning which is often associated with domestic heating systems, motor exhaust gases, industrial combustion and fires. Deaths from poisoning in medico-legal work can be accidental, suicidal or even homicidal and all these deaths need thorough evaluation, including the scene of death, toxicology and the autopsy findings. Forensically a correct conclusion is dependent on understanding of physical and chemical properties of carbon monoxide, its mechanism of action and the clinical findings and postmortem features.
Physicochemical Properties of Carbon Monoxide
The relative molecular mass of carbon monoxide gas. As it is a diatomic molecule with chemical formula CO it has a relatively small mass compared to air and can readily diffuse across living biological membranes. The solubility of the gas in water is relatively low, but it will readily dissolve in the blood due to its high affinity with haemoglobin. The gas is relatively chemically stable at body temperature and is not corrosive or irritating and therefore the body doesn’t have defensive mechanisms against breathing it in.
Mechanism of Toxic Action
Carbon monoxide damages cells and organisms by impairing oxygen transport and metabolism. It binds haemoglobin at a rate approximately 200-250 times greater than does oxygen creating carboxyhaemoglobin. It reduces delivery of oxygen to the tissues as oxygen will not dissociate from haemoglobin once carbon monoxide has bound to it since binding shifts the oxygen-haemoglobin dissociation curve to the left. In addition to damaging haemoglobin function, carbon monoxide causes cellular injury via binding of it to the protein’s myoglobin and mitochondrial cytochrome oxidase enzymes.
Binding of CO to these enzymes inhibits oxidative phosphorylation resulting in cellular hypoxia and aerobic metabolic dysfunction. Inherent susceptibility to cellular injury resulting from energy failure and metabolic acidosis affects organs that rely on aerobic metabolism the most: central nervous system and myocardium. Neurons and myocardial cells will not survive prolonged hypoxic injury leading to irreversible neuron loss and myocardial injury and fatal arrhythmias.
Clinical Features of CO Poisoning
Clinical manifestations of carbon monoxide are primarily dependent on the level of carboxyhaemoglobin in the body, as well as how long someone has been exposed to carbon monoxide. They may arise insidiously due to lack of definitive signs.
- Initial Symptoms: Headache, fatigue and malaise, dizziness, nausea
- Progressive Symptoms: Severe headache, vomiting, confusion and disorientation, Impaired cognition and judgment, visual disturbances, tachycardia, and dyspnoea
- The condition reaches its most dangerous stage when patients experience complete unconsciousness along with seizures and severe blood pressure drops, and they develop heart rhythm problems and their breathing stops, and they enter a coma, which results in death from brain and heart or breathing system failure
Postmortem Findings in Carbon Monoxide Poisoning
The postmortem examination process gives essential support for diagnosing carbon monoxide poisoning cases, which involve sudden or mysterious deaths.
External Examination
- Due to the carboxyhaemoglobin levels the various parts of the body, including face, nail beds and the lips may also take a pinkish or cherry-red appearance
- The skin appears flushed appearance
- Pulmonary edema causes frothy liquid to appear in the mouth and nostrils
- In fire-related deaths, the presence of soot around the nostrils, mouth, and upper airways indicates inhalation during life
Internal Examination
- The blood sample shows a bright red colour which stays in liquid form, which is a common sign of carbon monoxide poisoning
- Congestive edema in the lungs results in the release of frothy fluid when the lungs are cut
- Blood vessel enlargement and brain swelling are symptoms of hypoxic brain injury
- Prolonged exposure results in bilateral globus pallidus necrosis, which medical experts recognise as a common brain damage pattern
- The heart displays damage to the heart muscle and obstruction of blood flow, particularly in those who already have heart issues
- Systemic hypoxia results in congestion throughout the kidneys, spleen, and liver
Conclusion
The great difficulty in the forensic examination for CO poisoning is that it comes on suddenly, and proceeds very rapidly without showing the usual or distinctive signs. The forensic investigation of carbon monoxide poisoning presents its greatest difficulty because the toxic effects of the substance result from its ability to disrupt oxygen delivery while simultaneously decreasing oxygen availability to cells which harms both brain and heart functions. The correct diagnosis of the condition requires complete scene evidence evaluation together with autopsy results and toxicology test outcomes. The public needs educational programs like B.Sc in Forensic Science that focus on carbon monoxide poisoning because its occurrence can be prevented through proper combustion appliance maintenance.
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