Blood Gas Analysis and Acid-Base Disorders

Abstract

Human body maintain homeostasis by many physiological processes which keep a fine tuning of pH between 7.35 to 7.45. This pH enables various essential processes like oxygen delivery to tissue, maintaining protein structure in the proper configuration and helps in carrying out various biochemical reactions smoothly. Two types of acids contribute to daily acid load-respiratory (or volatile) acids and metabolic (or fixed) acids. Respiratory acid is carbon dioxide produced by complete oxidation of carbohydrates and fatty acids [1]. Although CO2 itself is not an acid as per Bronsted-Lowry system as it does not contain a hydrogen, instead it has a potential to create an equivalent amount of carbonic acid (H2CO3). Daily basal CO2 production is 12, 000 to 13, 000 mmols/day. All acids other then H2CO3 are fixed acids as those are not eliminated by lungs. These acids are produced due to incomplete metabolism of carbohydrates (e.g. lactate), fats (e.g. acetoacetate or b-hydroxybutyrate) and protein (e.g. sulphate, phosphate) and are eliminated by kidneys. Daily production is about 70 to 100 mmoles of H+ per day in an adult.