Which ABG pattern is characteristic of respiratory alkalosis?

Which ABG pattern is characteristic of respiratory alkalosis?

• A. High pH with low PCO2
• B. Low pH with high PCO2
• C. Low pH with low PCO2
• D. High pH with high PCO2

Answer: (A)

Respiratory alkalosis occurs when ventilation increases enough to blow off CO2, reducing the acid that CO2 forms in the blood. Less CO2 means less carbonic acid, so hydrogen ion concentration falls and the pH rises. The telling ABG pattern is a high pH with a low PCO2, reflecting the primary drop in CO2 from hyperventilation. If the situation persists, the kidneys begin to compensate by excreting bicarbonate, which can bring pH down toward normal over time (more pronounced in chronic cases). This pattern helps distinguish it from respiratory acidosis (low pH with high PCO2) and metabolic disturbances, which would not show a high pH paired with a low CO2.

Respiratory alkalosis occurs when ventilation increases enough to blow off CO2, reducing the acid that CO2 forms in the blood. Less CO2 means less carbonic acid, so hydrogen ion concentration falls and the pH rises. The telling ABG pattern is a high pH with a low PCO2, reflecting the primary drop in CO2 from hyperventilation. If the situation persists, the kidneys begin to compensate by excreting bicarbonate, which can bring pH down toward normal over time (more pronounced in chronic cases). This pattern helps distinguish it from respiratory acidosis (low pH with high PCO2) and metabolic disturbances, which would not show a high pH paired with a low CO2.