Tissue carbon dioxide measurement as an index of perfusion: What have we missed?

SummarySupported by experimental data, an exciting research topic is the characterization of tissue anaerobic metabolism by the measurement of tissue carbon dioxide (CO2) production. Under conditions of tissue hypoxia a decrease in VO2 is associated with a decrease in aerobic CO2 production, while an anaerobic CO2 production could occur. The rise in partial pressure of CO2 (PCO2) has been proposed to be a valuable, earlier and better marker of tissue hypoxia than conventional marker, such as serum lactate level, although potential mechanisms involved remain debated. Tissue PCO2 reflects metabolic alterations due to perfusion failure in actively metabolized tissues (heart, kidney and brain),11 and 12 and in sites more accessible for clinical practice (buccal, sublingual and skin). In this paper we consider the physiology of tissue PCO2, and outline recent data of both experimental and clinical studies supporting the use of PCO2 as a global marker of the adequacy of hemodynamic to cellular respiration.