Ventilation pattern

Since you have a LOT of acid in your blood (metabolic acidosis), your body will try to compensate by removing acid. One way it does this is by removing CO2 from your body (because when CO2 meets H2O, they can become carbonic acid). The chemoreceptors in your body will sense the increase in acidity, and send a message to your respiratory center telling it to make you breathe faster.

When you breathe faster, you'll blow out more CO2, resulting in a decrease in PCO2. PO2 as far as I know shouldn't really change much because your blood is pretty good at completely saturating itself. If anything, it may increase a little.