Step 3:
Compensation: each time the pCO2 changes, the normal kidney changes HCO3 to try to keep the pH at 7.40. This change is called compensation. The reverse is also true, when the kidney changes the HCO3 in the system, the lungs (respiratory system) try to adapt by changing the pCO2 to keep the pH at 7.40. If the changes are followed by an appropriate compensation, then it is termed a simple acid base process and the steps stop here. If the changes are not as described below, then there is a second acid base disorder. This second acid base disorder is named for the system that is doing the compensation.