Respiratory acidosis compensatory changes

As described above, high therapeutic doses of salicylate are associated with a primary respiratory alkalosis and compensatory renal acidosis. Subsequent changes in acid—base status generally occur only when toxic doses of salicylates are ingested by infants and children or occasioncdly after large doses in adults. 

The concentration of CO2 in blood is usually represented as FCO2, the partial pressure of CO2. Bicarbonate concentration can be regarded as the metabolic component of acid-base homeostasis while CO2 can be regarded as the respiratory component. Thus a primary change in one of these components as a result of a clinical condition can result in a compensatory change in other component. Raised blood PCO2 occurs in respiratory acidosis (as in chronic obstructive airway disease] and compensated metabolic alkalosis. Low blood PCO2 is found in respiratory alkalosis (hyperventilation) and in compensated metabolic acidosis. 

---