Respiratory regulation of acid base balance:

This is the second line of defense against acid base abnormalities.

1. When there is increase in the carbon dioxide concentration in the blood it can decrease the pH (increase in Hydrogen ion) and leads to acidosis.
2. Therefore, during acidosis respiratory center is activated and causes hyperventilation so that more amount of carbon dioxide is eliminated from the lungs (by lowering H₂CO₃).

          Carbon dioxide is continually formed in the tissues by the intracellular metabolic processes, and then it diffuses from cells to interstitial fluid and the blood. Finally, this carbon dioxide is transported to the lungs and diffused to alveoli and expired out.

However, this cannot last for long time and renal regulation is operated.