Less than 35 CO2 indicates which acid-base disturbance?

• A. Respiratory Alkalosis
• B. Metabolic Acidosis
• C. Metabolic Alkalosis
• D. Respiratory Acidosis

Answer: (A)

Lower-than-normal PaCO2 means the respiratory system is driving the pH up through increased ventilation. When you breathe faster or deeper, you blow off more carbon dioxide, which reduces carbonic acid in the blood and raises the pH. That pattern is the hallmark of respiratory alkalosis.

In contrast, a high PaCO2 would point to respiratory acidosis, and metabolic disturbances are identified by changes in bicarbonate and pH rather than CO2 alone. If there’s a low CO2, it might occur as a compensatory change in metabolic acidosis, but the primary problem in that scenario isn’t respiratory alkalosis.