Anatomical backgrounds on gas exchange parameters in the lung

Figure 9 O₂-CO₂ diagram and ventilation-perfusion line. A: O₂-CO₂ diagram, in which solid and dotted lines indicate gas R lines and blood R lines, respectively. Intersection of these two lines denoted by red circle provides a single ventilation-perfusion value and corresponding unique pair of P_O2 and P_CO2; B: Ventilation-perfusion line constructed by connecting each intersection of gas R lines and blood R lines. I: Inspired point; a: Arterial point; v: Mixed venous point. See text for further explanation. Adopted from ref[87].