Respiratory alkalosis, or primary hypocapnia, occurs when alveolar ventilation exceeds that required to eliminate the carbon dioxide produced by tissues. Concurrent decreases in Paco₂, increases in pH, and compensatory decreases in blood HCO₃⁻ levels are associated with respiratory alkalosis. Respiratory alkalosis can be acute or chronic, with metabolic compensation initially consisting of cellular uptake of HCO₃⁻ and buffering by intracellular phosphates and proteins. Chronic respiratory alkalosis results in longer-lasting decreases in renal reabsorption of HCO₃⁻; the arterial pH can approach near-normal values.