FIGURE 1.

Schematic representation of the model capillary with erythrocytes, separated from alveolar space by a single cell layer of alveolar epithelium. (A) In order to reconstruct O₂ and CO₂ pressure gradients along the capillary, it is divided into sections of equal size. The pressure gradient between alveolar space and blood (ΔpO₂) and the resulting flow of oxygen along this gradient is calculated for each section subsequently, as oxygen flow into one section affects pO₂ and thus ΔpO₂ of the next section. Calculation of oxygen diffusion depending on ΔpO₂ is based on Fick’s law (Weibel et al., 1993). (B) According to the pO₂ and pCO₂ gradients along the capillary sections determined in step 1, hemoglobin oxygen saturation (S_HbO2) is calculated for each section. The corresponding Hill equation has been defined and fitted to experimental data (Dash et al., 2016).