PaCO2 (mmHg) |
Expected bicarbonate = 24 - ((Baseline PCO2 - Patient's PCO2)/5)
NOTE: Baseline PCO2 default should be 40.
Interpretation: If patient's bicarb is higher than expected, a superimposed metabolic alkalosis is present. If it is lower, a superimposed metabolic acidosis is present.
Acute respiratory alkalosis should result in HCO3 drop by 2 mmol/L for every 10 mmHg decrease from pCO2
Since the limit of compensation varies between 12 and 20, value less than 20 should be cautiously judged.
Reference:
Doyle DJ. A Synopsis of Acid-Base Analysis. http://acidbase.homestead.com/ABG_Analysis_Rev_2.0.pdf. Update Jan 2006. Last assessed June 2013