Respiratory Acidosis and Alkalosis

Respiratory acid-base disorders are those disturbances in acid-base equilibrium that are expressed by a primary change in CO2 tension (Pco2) and reflect primary changes in the body’s CO2 stores (i.e., carbonic acid). A primary increase in Pco2 (and a primary increase in the body’s CO2 stores) defines respiratory acidosis or primary hypercapnia and is characterized by acidification of the body fluids. By contrast, a primary decrease in Pco2 (and a primary decrease in the body’s CO2 stores) defines respiratory alkalosis or primary hypocapnia and is characterized by alkalinization of the body fluids. Primary changes in Pco2 elicit secondary physiologic changes in plasma [HCO3ˉ] that are directional and proportional to the primary changes and tend to minimize the impact on acidity. This review presents the pathophysiology, secondary physiologic response, causes, clinical manifestations, diagnosis, and therapeutic principles of respiratory acidosis and respiratory alkalosis. This review contains 4 figures, 3 tables, and 59 references. Key words: Respiratory acidosis, respiratory alkalosis, primary hypercapnia, primary hypocapnia, hypoxemia, pseudorespiratory alkalosis