What is the correct interpretation of these ABGs? pH 7.35, HCO3 18, PCO2 30?

• A. Acute metabolic acidosis with no compensation
• B. Respiratory alkalosis
• C. Metabolic acidosis with partial respiratory compensation
• D. Normal acid-base status

Answer: (C)

The main idea is to read ABGs by pairing pH with the primary change in bicarbonate and the compensatory change in PCO2. A low bicarbonate shows metabolic acidosis. When the body tries to compensate for metabolic acidosis, the respiratory system lowers CO2 by blowing off more air, so the PCO2 drops.

Here the bicarbonate is 18, confirming metabolic acidosis. The PCO2 is 30, which means the lungs are actively compensating by reducing CO2. The pH is 7.35, which sits at the lower end of the normal range, indicating that the compensation has begun and has brought the pH closer to normal but has not fully normalized it. This pattern is best described as metabolic acidosis with partial respiratory compensation.