As CO2 levels increase, the equations moves to the right and the concentration of H+ ions also increases. More H+ means more acidic, or a lower pH. Conversely, decrease CO2, equation moves to the left, decreasing [H+] ion.
Increase respiratory rate: increase O2 and CO2 gradient. High O2 concentration in lungs therefore more goes into the circulatory system: increase O2 in blood. Low CO2 concentration in lungs (exchanging more CO2 from lungs to atm) decrease CO2 in blood because the gradient is causing CO2 to move from the circulatory system to the lungs. Decrease in CO2, equation moves to the right, increase pH/basicity.
Decrease in respiratory rate, decrease of O2 intake/in blood, increase CO2 in blood (CO2 accumulation in lung [reservoir]), decrease in pH/ increase acidity.
I think this is right, haven't taken physiology classes for a while now. You may want to check an introductory phys book/course. I remember going over this then.