Understand the four categories of hypoxemia. In the upright lung gravity causes a pleural pressure gradient to alter distribution of ventilation and a hydrostatic pressure gradient to alter distribution of blood flow. Yes, because the base of the lung both ventilates more than the apex and receives more cardiac output than the apex thereby matching ventilation. Alveolar gas at the apex will be higher in oxygen and lower in carbon dioxide than the at the base. At the base of the lung the is 0.6.
Perfusion increases more rapidly from the apex to the base then does ventilation.
The base is relatively over-perfused and thus will have lower oxygen and higher carbon dioxide gas tensions. If there is no ventilation then alveolar and pulmonary capillary partial pressures are the same as the mixed venous blood. If there is no perfusion then alveolar partial pressures are the same as the inspired gas tensions. The net effects of combining pulmonary capillary flow from regions with different depends upon the gas contents of the mixing blood streams. 76 mmHg and not 92.5 mmHg.