VCO2VA

VCO2VA is a term used in respiratory physiology and clinical monitoring to describe the relationship between carbon dioxide production (VCO2) and alveolar ventilation (VA). The notation VCO2/VA is more common in literature, and VCO2VA can appear as a shorthand in some texts or software. It represents the rate at which CO2 is generated per unit of alveolar ventilation.

In physiology, VCO2 is the metabolic CO2 produced by tissues, measured in milliliters per minute, while VA is the portion of ventilation that participates in gas exchange, typically measured in liters per minute. The quantity VCO2/VA is directly related to the concentration of CO2 in the alveoli and, through the alveolar gas equation, is proportional to alveolar CO2 tension. A commonly cited relation is PACO2 ≈ (VCO2 × 0.863) / VA, indicating that increasing VCO2 or reducing VA raises alveolar CO2 pressure.

Clinically, VCO2/VA (or VCO2 divided by VA) is used to assess ventilatory efficiency and to monitor conditions that affect CO2 elimination, such as anesthesia, critical care ventilation, fever, shivering, sepsis, or metabolic disturbances. A higher VCO2/VA suggests less efficient CO2 removal for a given alveolar ventilation, whereas a lower value indicates more efficient CO2 elimination.

Measurement typically relies on metabolic monitoring that provides simultaneous estimates of VCO2 and VA, or on derived calculations from arterial blood gases and ventilator parameters. Limitations include dependence on steady-state metabolism, accurate ventilation measurements, and assumptions about gas mixing and constants in the alveolar equation. Related concepts include VCO2, VA, PACO2, and the Bohr equation for dead space.