ABG pattern in pulmonary hypertension typically shows which pattern?

• A. Metabolic acidosis with normal PaO2
• B. Respiratory alkalosis with hypoxemia
• C. Respiratory acidosis with hypoxemia
• D. Metabolic alkalosis with hypoxemia

Answer: (B)

Pulmonary hypertension often causes V/Q mismatch and diffusion impairment, leading to low oxygen levels in the blood. In response, the body increases breathing to try to raise oxygenation, so patients tend to hyperventilate. This results in a lower PaCO2 and a higher pH, i.e., respiratory alkalosis, while hypoxemia persists. The pattern seen on ABG is thus respiratory alkalosis with hypoxemia. Metabolic disturbances like metabolic acidosis or metabolic alkalosis aren’t the typical result of this physiology, and respiratory acidosis would imply hypoventilation rather than the common hyperventilation seen in this condition.