Hypercapnia refers to the excessive presence of carbon dioxide, or CO2, content in the blood plasma. It is due to inhaling air which is too rich in carbon dioxide, or more often to decreased pulmonary ventilation, which is the case in respiratory failure. Hypercapnia may occur suddenly and cause acidification of the blood called respiratory acidosis. Conversely, if it appears more gradually, the body compensates by raising the levels of bicarbonates, basics, or alkalines which controls this acidity. The symptoms of hypercapnia are fatigue, sweating, loss of consciousness or drowsiness, and increased blood pressure.