A patient with bicarbonate of 30, high CO2, and low pH is likely to have _____ respiratory failure.

• A. Acute
• B. Chronic
• C. Acute on chronic
• D. Hypercapnic

Answer: (B)

When CO2 remains elevated over time, the kidneys compensate by retaining bicarbonate, which raises the HCO3– level. A bicarbonate of 30 mEq/L in the setting of high CO2 and a low pH indicates that the body has had time to develop metabolic compensation for a chronic CO2 retention. That pattern points to chronic respiratory failure with ongoing acidemia, rather than an acute process where bicarbonate has not yet risen.

In contrast, acute respiratory failure would typically show a smaller rise in bicarbonate because there hasn’t been enough time for renal compensation, and pH would be more profoundly acidemic. The term hypercapnic describes the presence of high CO2 but doesn’t specify duration or compensation; the elevated bicarbonate here makes chronic respiratory failure the best fit.