Carbon Monoxide Poisoning






How Does Carbon Monoxdie Afferct the Human Body?

Carbon monoxide poisoning occurs after enough inhalation of carbon monoxide (CO).

Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect. Carbon monoxide is a product of incomplete combustion of organic matter due to insufficient oxygen supply to enable complete oxidation to carbon dioxide (CO2).

It is often produced in domestic or industrial settings by motor vehicles that run on gasoline, diesel, propane, methane, or other carbon-based fuels and tools, heaters, and cooking equipment that are powered by carbon-based fuels.

Exposures at 100 parts per million or greater can be dangerous to human health.

Symptoms of mild acute poisoning will include: light-headedness, confusion, headaches, vertigo, and flu-like effects.

Larger exposures can lead to: significant toxicity of the central nervous system and heart, and even death.

Carbon monoxide can also have severe effects on the fetus of a pregnant woman.

Chronic exposure to low levels of carbon monoxide can lead to depression, confusion, and memory loss.

Carbon monoxide mainly causes adverse effects in humans by combining with hemoglobin to form carboxyhemoglobin (HbCO) in the blood. This prevents hemoglobin from releasing oxygen in tissues, effectively reducing the oxygen-carrying capacity of the blood, leading to hypoxia (a condition or state in which the supply of oxygen is insufficient for normal life functions).

Treatment of poisoning largely consists of administering 100% oxygen or providing hyperbaric oxygen therapy, although the optimum treatment remains controversial.

Oxygen works as an antidote as it increases the removal of carbon monoxide from hemoglobin, in turn providing the body with normal levels of oxygen. The prevention of poisoning is a significant public health issue.

Domestic carbon monoxide poisoning can be prevented by early detection with the use of household carbon monoxide detectors. Carbon monoxide poisoning is the most common type of fatal poisoning in many countries.

Historically, it was also commonly used as a method to commit suicide, usually by deliberately inhaling the exhaust fumes of a running car engine.

Modern automobiles, even with electronically-controlled combustion and catalytic converters, can still produce levels of carbon monoxide which will kill if enclosed within a garage or if the tailpipe is obstructed (for example, by snow) and exhaust gas cannot escape normally.

Carbon monoxide is not toxic to all forms of life. Its harmful effects are due to binding with haemoglobin so its danger to organisms that do not use this compound is doubtful. It thus has no effect on photosynthesising plants.

It is easily absorbed through the lungs. Inhaling the gas can lead to hypoxic injury, neurological damage, and even death.

Different people and populations may have different carbon monoxide tolerance levels. On average, exposures at 100 ppm or greater is dangerous to human health.

In the United States, the OSHA limits long-term workplace exposure levels to less than 50 ppm averaged over an 8-hour period. In addition, employees are to be removed from any confined space if an upper limit ("ceiling") of 100 ppm is reached.

Carbon monoxide exposure may lead to a significantly shorter life span due to heart damage.

The carbon monoxide tolerance level for any person is altered by several factors, including activity level, rate of ventilation, a pre-existing cerebral or cardiovascular disease, cardiac output, anemia, sickle cell disease and other hematological disorders, barometric pressure, and metabolic rate.

The acute effects produced by carbon monoxide in relation to ambient concentration in parts per million are listed below:

Concentration Symptoms

35 ppm (0.0035%) Headache and dizziness within six to eight hours of constant exposure
100 ppm (0.01%) Slight headache in two to three hours
200 ppm (0.02%) Slight headache within two to three hours; loss of judgment
400 ppm (0.04%) Frontal headache within one to two hours
800 ppm (0.08%) Dizziness, nausea, and convulsions within 45 min; insensible within 2 hours
1,600 ppm (0.16%) Headache, tachycardia, dizziness, and nausea within 20 min; death in less than 2 hours
3,200 ppm (0.32%) Headache, dizziness and nausea in five to ten minutes. Death within 30 minutes.
6,400 ppm (0.64%) Headache and dizziness in one to two minutes.
Convulsions, respiratory arrest, and death in less than 20 minutes.
12,800 ppm (1.28%) Unconsciousness after 23 breaths. Death in less than three minutes.

Acute poisoning

The main manifestations of carbon monoxide poisoning develop in the organ systems most dependent on oxygen use, the central nervous system and the heart.

The initial symptoms of acute carbon monoxide poisoning include: headache, nausea, malaise, and fatigue. These symptoms are often mistaken for a virus such as influenza or other illnesses such as food poisoning or gastroenteritis.

Headache is the most common symptom of acute carbon monoxide poisoning and is often described as dull, frontal, and continuous.

Increasing exposure produces cardiac abnormalities including fast heart rate, low blood pressure, and cardiac arrhythmia.

Central nervous system symptoms include: delirium, hallucinations, dizziness, unsteady gait, confusion, seizures, central nervous system depression, unconsciousness, respiratory arrest, and death.

Less common symptoms of acute carbon monoxide poisoning include: myocardial ischemia, atrial fibrillation, pneumonia, pulmonary edema, high blood sugar, lactic acidosis, muscle necrosis, acute kidney failure, skin lesions, and visual and auditory problems.

One of the major concerns following acute carbon monoxide poisoning is the severe but delayed neurological manifestations that may occur.

Problems may include difficulty with higher intellectual functions, short-term memory loss, dementia, amnesia, psychosis, irritability, a strange gait, speech disturbances, Parkinson's disease-like syndromes, cortical blindness, and a depressed mood.

Chronic exposure to relatively low levels of carbon monoxide may cause persistent headaches, lightheadedness, depression, confusion, memory loss, nausea and vomiting.

It is unknown whether low-level chronic exposure may cause permanent neurological damage. Typically, upon removal from exposure to carbon monoxide, symptoms usually resolve themselves, unless there has been an episode of severe acute poisoning.

As many symptoms of carbon monoxide poisoning also occur with many other types of poisonings and infections (such as the flu), the diagnosis is often difficult.

A history of potential carbon monoxide exposure, such as being exposed to a residential fire, may suggest poisoning, but the diagnosis is confirmed by measuring the levels of carbon monoxide in the blood. This can be determined by measuring the amount of carboxyhemoglobin compared to the amount of hemoglobin in the blood.

There are many conditions to be considered in the differential diagnosis of carbon monoxide poisoning. The earliest symptoms, especially from low level exposures, are often non-specific and readily confused with other illnesses, typically flu-like viral syndromes, depression, chronic fatigue syndrome, chest pain, and migraine or other headaches.

Initial treatment for carbon monoxide poisoning is to immediately remove the person from the exposure without endangering further people. Those who are unconscious may require CPR on site.

Administering oxygen via non-rebreather mask shortens the half life of carbon monoxide to 80 minutes from 320 minutes on normal air. Oxygen hastens the dissociation of carbon monoxide from carboxyhemoglobin, thus turning it back into hemoglobin.

Due to the possible severe effects in the fetus, pregnant women are treated with oxygen for longer periods of time than non-pregnant people.