This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ABG Analysis Simplified, Subject name: Medicine
Lab values: pH 7.42, paCO2- 25, HCO3- 18. Interpret- 
Select and explain. 
A. Metabolic acidosis, paially compensated, B. Respiratory acidosis, paially compensated, C. Respiratory acidosis, fully compensated, D. Respiratory alkalosis, fully compensated
D: Respiratory alkalosis, fully compensated
Answer: D: Respiratory alkalosis, fully compensated 
Explanation: pH - 7.42 (N) PaCO2 - 25 (low) since Value of pH is towards alkaline side,low pCO2 explains alkaline pH.(Respiratory alkalosis) HCO3 - 18 (low) | in CO2 = 40-25 = 15 * For chronic change for every 10 mmHg fall in PCO2- HCO3 | by 4 mEq. HCO3 to be | by 4 x1 .5 = 6 HCO3 = 18 -means compensation is going fine . since pH is normal so we can say that condition is fully compensated so this is the case of Respiratory alkalosis,fully compensated.