The carbon dioxide-bicarbonate system is the most important of the body’s buffer systems (others include intracellular proteins, hemoglobin, plasma proteins, and constituents of bone). The bicarbonate buffer system modulates pH in both intra- and extra-cellular body fluids.
Bicarbonate, present in most body fluids, constitutes a large reservoir of buffer called the alkali reserve. Bicarbonate reacts with the hydrogen ion to form carbonic acid, which exists in equilibrium with carbon dioxide.
With hydrogen ion ingestion or production by metabolizing tissues, bicarbonate converts it to carbonic acid and, ultimately, to carbon dioxide and water. And the carbon dioxide is eliminated by the lungs.
The system pH in which these reactions take place is calculated using the Henderson-Hasselbalch equation.
However, from a clinical perspective, using blood gas analysis, it makes more sense to express the concentration of H2CO3 as the partial pressure of CO2 times the solubility factor for CO2.
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- Grippi, MA. 1995. “Gas exchange in the lung”. In: Lippincott's Pathophysiology Series: Pulmonary Pathophysiology. 1st edition. Philadelphia: Lippincott Williams & Wilkins. (Grippi 1995, 137–149)
- Grippi, MA. 1995. “Clinical presentations: gas exchange and transport”. In: Lippincott's Pathophysiology Series: Pulmonary Pathophysiology. 1st edition. Philadelphia: Lippincott Williams & Wilkins. (Grippi 1995, 171–176)
- Grippi, MA and Tino, G. 2015. “Pulmonary function testing”. In: Fishman's Pulmonary Diseases and Disorders, edited by MA, Grippi (editor-in-chief), JA, Elias, JA, Fishman, RM, Kotloff, AI, Pack, RM, Senior (editors). 5th edition. New York: McGraw-Hill Education. (Grippi and Tino 2015, 502–536)
- Tino, G and Grippi, MA. 1995. “Gas transport to and from peripheral tissues”. In: Lippincott's Pathophysiology Series: Pulmonary Pathophysiology. 1st edition. Philadelphia: Lippincott Williams & Wilkins. (Tino and Grippi 1995, 151–170)
- Wagner, PD. 2015. The physiologic basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases. Eur Respir J. 45: 227–243. PMID: 25323225