<P> Hypercapnia is the opposite of hypocapnia, the state of having abnormally reduced levels of carbon dioxide in the blood . The word is from the Greek hyper = "above" or "too much" and kapnos = "smoke". </P> <P> Symptoms and signs of early hypercapnia include flushed skin, full pulse, tachypnea, dyspnea, extrasystoles, muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure . According to other sources, symptoms of mild hypercapnia might include headache, confusion and lethargy . Hypercapnia can induce increased cardiac output, an elevation in arterial blood pressure, and a propensity toward arrhythmias . Hypercapnia may increase pulmonary capillary resistance . In severe hypercapnia (generally PaCO greater than 10 kPa or 75 mmHg), symptomatology progresses to disorientation, panic, hyperventilation, convulsions, unconsciousness, and eventually death . </P> <P> Hypercapnia is generally caused by hypoventilation, lung disease, or diminished consciousness . It may also be caused by exposure to environments containing abnormally high concentrations of carbon dioxide, such as from volcanic or geothermal activity, or by rebreathing exhaled carbon dioxide . It can also be an initial effect of administering supplemental oxygen on a patient with sleep apnea . In this situation the hypercapnia can also be accompanied by respiratory acidosis . </P> <P> Hypercapnia is generally defined as a blood gas carbon dioxide level over 45 mmHg . Since carbon dioxide is in equilibrium with carbonic acid in the blood, hypercapnia can drive serum pH down, resulting in a respiratory acidosis . Clinically, the effect of hypercapnia on pH is estimated using the ratio of the arterial pressure of carbon dioxide to the concentration of bicarbonate ion, P CO / (HCO). </P>

Why does carbon dioxide increase in the body