Rate of Elimination of Labeled Carbon Dioxide From the Body

¹ From the Department of Physiology, School of Medicine, University of Southern California, Los Angeles, and the Scripps Metabolic Clinic, La Jolla, California

When C¹⁴-labeled bicarbonate is injected intravenously about 10% of it is exhaled within 30 seconds by the lungs before it is mixed with body CO₂. Labeled CO₂ that has escaped elimination by the lungs is mixed with body CO₂ in a complex manner. The CO₂ in those tissues with a high blood flow equilibrates very rapidly with that of the blood. Resting muscle and skin need at least 5 minutes for equilibration with the CO₂ of the blood. Calculations of body CO₂ pool based on the assumption of complete instantaneous equilibrium between blood and tissues are not valid. The manner of elimination of labeled CO₂ produced in metabolism is complex and does not simulate that following intravenous or intraperitoneal injection of labeled bicarbonate.

This article has been cited by other articles:

				K. Roecker, E. Landaw, H. Striegel, F. Mayer, and H.-H. Dickhuth First-pass effect of an intravenous bolus of [13C]bicarbonate displayed breath-by-breath J Appl Physiol, June 1, 2001; 90(6): 2181 - 2187. [Abstract] [Full Text] [PDF]