Hyperventilation

Hyperventilation (also called overbreathing) occurs when the rate and quantity of alveolar ventilation of carbon dioxide exceeds the body's production of carbon dioxide. A person may regularly hyperventilate, a condition called hyperventilation syndrome.

When alveolar ventilation is excessive, more carbon dioxide will be removed from the blood stream than the body can produce. This causes the concentration of carbon dioxide in the blood stream to fall and produces a state known as hypocapnia. The body normally attempts to compensate for this metabolically. If excess ventilation cannot be compensated metabolically, it will lead to a rise in blood pH. This rise in blood pH is known as respiratory alkalosis. When hyperventilation leads to respiratory alkalosis, it may cause a number of physical symptoms: dizziness, tingling in the lips, hands or feet, headache, weakness, fainting and seizures. In extreme cases it can cause carpopedal spasms (flapping and contraction of the hands and feet).

There are factors that initiate hyperventilation and others can sustain it; for example, physiological stress or a feeling of anxiety can initiate it; anxiety may also sustain it.

Other factors that initiate or sustain hyperventilation include reduced air pressure at high altitudes, head injury, stroke, respiratory disorders such as asthma and pneumonia, cardiovascular problems such as pulmonary embolisms, anemia, and adverse reactions to certain drugs.

Hyperventilation can also be mechanically produced in people on respirators and can also be brought about voluntarily, by taking many deep breaths in rapid succession.