What happens to the ratio of oxygenated hbo2(aq) to deoxygenated hb(aq), i. e. , when there is a high pressure of oxygen, po2(g), in the lungs?

The chemical equilibrium representing the reaction of hemoglobin with oxygen is,

In the lungs, where the partial pressure of oxygen is high, the above equilibrium shifts towards the products according to the LeChattelier's principle, as the pressure of one of the reactants is increased. This leads to the formation of more oxyhemoglobin.

In the cells, where the partial pressure of oxygen is low, the equilibrium shifts towards left that is hemoglobin.

Therefore the ratio of oxyhemoglobin to hemoglobin increases as the partial pressure of oxygen is high in the lungs.