A patient presents with a pH of 7.2, a PaCO2 of 40 mmHg, and a bicarbonate level of 20 mEq/L. What is the most likely diagnosis?

A Respiratory acidosis
B Metabolic acidosis ✓
C Respiratory alkalosis
D Metabolic alkalosis

Explanation

The patient's pH is low (acidic), and the bicarbonate level is also low. This suggests a metabolic acidosis, which is confirmed by the normal PaCO2 level.

Source

Harrison's Principles of Internal Medicine
Electrolytes and Acid-Base Balance Pathophysiology Acid-Base Disorders Hard MEDICAL Confidence: high