Recent advances in acid-base physiology and in the epidemiology of acid-base disorders have refined our understanding of the basic control mechanisms that determine blood pH in health and disease. These refinements have also brought parity between the newer, quantitative and older, descriptive approaches to acid-base physiology. This review explores how the new and older approaches to acid-base physiology can be reconciled and combined to result in a powerful bedside tool. A case based tutorial is also provided.