Only a narrow range of pH is compatible with life (7.35-7.45). Acidosis is a plasma pH 7.45. Buffers keep the pH from changing when acid or base is added to solution. Bicarbonate is the primary extracellular buffer system. This bicarbonate is the transport form of carbon dioxide. Thus, regulation of plasma carbon dioxide levels regulates bicarbonate concentrations and blood pH. Alternatively, bicarbonate levels can be directly regulated.
The lungs regulate carbon dioxide levels. This is a short-term regulation that rapidly responds to changing conditions. Increased carbon dioxide (decreased ventilation) decreases pH. Reduced carbon dioxide (increased ventilation) increases pH.
The most common acid/base imbalance is acidosis. In acidosis, the kidneys excrete H ions to rid the body of acids and reabsorb bicarbonate to add to the buffer pool. Both serve to increase pH and reverse the acidosis.
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