Question

Describe how COPD can affect the body’s acid-base balance, explaining how this condition develops (pathogenesis). Discuss the mechanisms of body compensation that would occur as an attempt to recover homeostasis?

Answer 1

In COPD patients, chronically elevated carbon dioxide shifts the normal acid-base balance toward acidic. There is the retention of carbon dioxide which is hydrated to form carbonic acid. Carbonic acid is a weak and volatile acid that quickly dissociates to form hydrogen and bicarbonate ions. This results in respiratory acidosis. This primary event is characterized by increased pCO2 and a fall in pH on arterial blood gas analysis.

The adjustment of the pH by the kidneys is much more effective in chronic respiratory acidosis, and it can be better tolerated as compared to the acute phase. In chronic respiratory acidosis in COPD patients, the body tries to compensate by retaining more bicarbonate to overcome acidosis. The renal compensation sets in and the kidneys adapt to excrete carbon dioxide in the form of carbonic acid and reabsorb more bicarbonate. It usually takes about 3 to 5 days for the maximum response. This helps in maintaining acid-base balance near normal and prevents the pH to become dangerously low