Hypocapnia

From Ask Dr Wiki

Hypocapnia or Hypocapnea, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation.

Hypocapnia is the opposite of hypercapnia.

Even when severe, hypocapnia is normally well tolerated. However, hypocapnia causes cerebral vasoconstriction, leading to cerebral hypoxia and this can cause transient dizziness, visual disturbances, and anxiety. A low partial pressure of carbon dioxide in the blood also causes alkalosis (because CO₂ is acidic in solution), leading to lowered plasma calcium ions and nerve and muscle excitability. This explains the other common symptoms of hyperventilation —pins and needles, muscle cramps and tetany in the extremities, especially hands and feet.

Hypocapnia is sometimes induced in the treatment of the medical emergencies, such as intracranial hypertension and hyperkalaemia.

See also

• Hypercapnia, increased level of carbon dioxide
• Hyperventilation syndrome, which is often associated with hypocapnia