Chronic salicylate use can cause respiratory alkalosis. Severe salicylate toxicity results in an anion gap metabolic acidosis such as during an overdose. During acute hyperventilation, plasma bicarbonate concentrations fall by approximately 3 mEq/L when the arterial pressure of CO2 falls to about 25 mm Hg. Acute respiratory alkalosis can be caused by anxiety, central nervous system (CNS) disorders, drugs, or fever. Chronic respiratory alkalosis occurs in pregnancy and liver disease as well.