Ideal alveolar gas defined by modal gas exchange in ventilation-perfusion distributions

Abstract

The three-compartment model of lung ventilation-perfusion mismatch postulates definitive alveolar deadspace and "ideal gas" lung compartments, but these are in fact widely different for gases of different blood solubility. Physiologically realistic distributions of ventilation, perfusion and gas exchange instead suggest an individual "ideal" ventilation-perfusion ratio for every gas, where its alveolar-capillary uptake or elimination rate is maximal (modal). For carbon dioxide this "ideal" partial pressure is the mean of the arterial and end-tidal partial pressures.