Q: 60-year old patient presented with the compliant of shortness of breath. Patient has 60 pack-year history of smoking. Patient 

sodium is 140meq/l,
 potassium is 4meq/l, 
chloride is 94meq/l, and 
HCO3 is 36meq/l. 

 Patient abg revealed 

pCO2 is 70 and 
pH is 7.31.

 What is the acid base disturbance. 

 A) Metabolic acidosis
 B) Acute Respiratory acidosis 
 C) Chronic Respiratory acidosis 
 D) Mixed Metabolic and Respiratory acidosis 


 Answer: C

Rationale: Patient anion gap is 10 that rules out metabolic acidosis.  For every 10 Torr change in CO₂ change in ph is 0.3 for chronic and 0.8 for acute.  Since the change in torr of CO₂ in this case is 30, and ph is 7.31 that makes it chronic respiratory acidosis.  If it would have been acute that the ph should have been 7.16 (0.08x3=0.24; 7.4-.24=7.16)