Respiratory Regulation of Acid-Base Balance in Health and Disease

Abstract

Homeothermic mammals, including humans, normally maintain both intracellular and extracellular pH within a rather narrow range of values, with the normal values being approximately 6.9 and 7.4, respectively. Because intracellular pH is difficult to measure, most physiological and clinical evaluations focus on extracellular pH, which is measured in samples of arterial or venous blood. Among the different body compartments, including vascular and extravascular, as well as intra- and extracellular, blood is easily accessible and the pH values in blood are presumed to reflect whole body pH, including the intracellular compartment. Values of blood extracellular fluid pH above 7.7 and below 6.9 in humans can result in morbidity and mortality. A clear understanding of the importance of pH and how to interpret clinically available acid-base data is of utmost importance to the physician.