When there is drop in the blood pH,

When CO₂ levels in the body increases, H⁺ concentration increases, and blood pH decreases. By increasing the rate and depth of breathing, more carbon dioxide can be exhaled. Within minutes this reduces the level of carbonic acid in blood, which raises the blood pH (reduces blood H⁺ level). 

Also drop in pH causes: 

• A decrease in the the affinity of haemoglobin with RBC.
• An increase in the excretion of H⁺ ions from the renal filtrate.