Carbon dioxide in clinical testing is typically reported as total CO2, the majority of which exists as bicarbonate (HCO3−) in blood. Biochemically it is an inorganic anion central to the bicarbonate buffer system that buffers H+ ions and helps stabilize blood pH. The relationship between CO2, bicarbonate, and pH was formalized in acid–base physiology through the Henderson–Hasselbalch concept and later clinical gas and chemistry measurements. Physiologically, CO2 and bicarbonate link respiration and metabolism: tissues produce CO2, lungs remove gaseous CO2, and kidneys regulate bicarbonate reabsorption and excretion. Because multiple organs contribute, total CO2 is a useful systemic marker that reflects combined respiratory, renal, and metabolic processes rather than a single tissue source.

Higher total CO2 values generally reflect greater bicarbonate concentration and can be associated with alkalinizing shifts or compensation for chronic respiratory conditions; they can also arise from altered kidney handling of bicarbonate. Lower total CO2 values typically indicate reduced bicarbonate and are associated with acidifying shifts, increased acid load, or compensatory changes from altered breathing. Interpretation depends on the broader clinical picture: electrolytes, blood gases, kidney function, glucose and metabolic markers, and respiratory status are needed to distinguish whether CO2 changes reflect metabolic processes, respiratory compensation, or lab/collection factors.

Cardio Zoomer includes total CO2 to assess systemic acid–base balance as one part of metabolic and organ-function evaluation. Variations in CO2 connect metabolic load, kidney function, and respiratory patterns to vascular and cardiac physiology, helping clinicians place acid–base status alongside lipids, inflammation, and genetic risk when tailoring prevention and monitoring strategies.