The First Defense against a Change in Blood pH Is Provided by the Blood Buffers, but the Lungs and Kidneys Must Ultimately Correct the Hydrogen Ion Load

When body pH is threatened by a change in the production or elimination of H⁺, the first line of defense is provided by buffers within the blood and tissues. However, buffers only prevent drastic changes in pH; they cannot correct the problem by increasing or decreasing the elimination of H⁴ or by replacing lost buffering capacity. Ultimately, pH must be corrected by adjustments in ventilation or by changes in renal function. Because the lungs can alter Paco₂ and the kidneys can regulate the concentration of HCO₃^-, the Henderson- Hasselbalch equation has been written as follows: