6.5: Compensation
- Page ID
- 10902
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The compensatory response is a fall in bicarbonate level
As can be seen by inspection of the Henderson-Hasselbalch equation (below), a decreased [HCO3 -] will counteract the effect of a decreased pCO2 on the pH. Mathematically, it returns the value of the \( \frac {[HCO_{3}^{-}]} {0.03pCO_{2}} \) ratio towards normal.
\[ pH = pKa + \log \frac {[HCO_{3}^{-}]} {0.03pCO_{2}} \]
Key points regarding compensation in respiratory alkalosis:
- Physicochemical effect: Initially there is an immediate physicochemical change which lowers the bicarbonate slightly.
- Role of Kidney: The effector organ for compensation is the kidney.
- Slow Response: The renal response has a slow onset and the maximal response takes 2 to 3 days to be achieved.
- Outcome: The drop in bicarbonate results in the extracellular pH returning only partially towards its normal value.