Carbon Dioxide in Blood

Carbon dioxide (CO₂) plays an important role in the human body. It is a waste product of cellular metabolism, exhaled by the lungs at the same time that oxygen is inhaled. This waste product is involved in the transportation of oxygen from the blood, to the cells of the body. Reduced carbon dioxide levels result in reduced oxygen in the body tissues and vital organs, resulting in various health issues. CO₂ helps dilate the smooth muscle tissues and helps regulate the cardiovascular system. CO₂ gets converted to carbonic acid, thereby becoming a primary regulator of the alkaline/acid balance of the body. Moreover, CO₂ plays a role in the proper functioning of the digestive system. Thus, carbon dioxide in blood levels plays a very important role in the body. The normal concentration of CO₂ in the bloodstream is 40 mm of Hg.

High Carbon Dioxide in Blood (Hypercapnia)

When the level of CO₂ goes beyond 45 mm of Hg, the condition is called hypercapnia. The levels of CO₂ in the body increase due to hypoventilation, diminished consciousness or lung diseases. Hypoventilation is a condition that occurs when the ventilation is inadequate to perform the necessary gaseous exchange. The lack of adequate ventilation results in increased concentration of CO₂ in the blood. Hypercapnia can also be caused when the body is exposed to environments comprising of high concentrations of CO₂, such as volcanic regions. Inhalation of exhaled CO₂ rich air can also lead to high CO₂ levels in the blood. Some of the mild symptoms of this condition are lethargy, confusion and headaches. The other signs of early hypercapnia encompass:

• Flushed skin.
• Extra systoles.
• Increased blood pressure.
• Reduced neural activity.
• Muscle twitching.

Inadequate ventilation occurs in divers, resulting in an incomplete expulsion of CO₂ from the blood, while exhaling. This happens because divers breathe into a full face diving mask, diving helmet or long snorkel, which fails to permit a complete passage of CO₂ into the environment. This results in inhalation of exhaled CO₂ rich air. Since the diver is constantly exercising, the metabolic activity continues to increase, thereby producing more CO₂. The final result is hypercapnia.

Low Carbon Dioxide in Blood (Hypocapnia)

Hypocapnia refers to the condition of reduced CO₂ levels in the bloodstream and is the opposite condition of hypercapnia. This condition is sometimes aroused by the treatment of medical emergencies, such as hyperkalemia, high blood pressure (hypertension), etc. On the other hand, hypocapnia can also be self induced, by hyperventilation. The state of breathing faster and deeper than necessary is termed as hyperventilation. This over-breathing results in light-headedness and several other undesirable symptoms, that are associated with panic attacks.

Hyperventilation reduces the CO₂ concentration level in the bloodstream, below the normal 40 mm of Hg, thereby resulting in an increased level of pH value. Since CO₂ increases the acidity in the blood, a low CO₂ level leads to increased alkalinity in the blood. This, in turn, leads to the constriction of blood vessels that supply blood to the brain. Moreover, transport of essential electrolytes for the functioning of the nervous system is also reduced. Low level of CO₂ in the bloodstream, can cause cerebral vasoconstriction, thereby resulting in cerebral hypoxia. The symptoms and signs of this are:

• Visual disturbances.
• Anxiety.
• Transient dizziness in the person.
• Muscle cramps.
• Blackouts.

Most of the CO₂ content in the body is in the form of bicarbonate. Thus, when laboratory tests are conducted to check the CO₂ level in the blood, it is actually measuring the blood bicarbonate level. The level of carbon dioxide in blood has to be around 40 mm of Hg, for the proper functioning of the body. Deviations in the amount of carbon dioxide in blood can lead to dizziness, respiratory and cardiac arrest and even death.