What happens to pH during respiratory acidosis?

What happens to pH during respiratory acidosis?

• A. pH decreases (low pH) due to CO2 retention.
• B. pH increases (high pH).
• C. pH remains the same.
• D. pH increases due to bicarbonate retention.

Answer: (A)

In respiratory acidosis, the drive, or ventilation, is insufficient, so carbon dioxide builds up in the blood. CO2 combines with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. The extra hydrogen ions increase acidity and cause the pH to fall. The relationship is captured by the equation pH = 6.1 + log([HCO3-]/(0.03 × PaCO2)); when PaCO2 rises, the ratio skews toward acidity, lowering pH. In the short term, pH drops due to CO2 retention. Over time, the kidneys can compensate by retaining bicarbonate, which can raise pH toward normal, but that is a compensatory process, not the immediate effect.

In respiratory acidosis, the drive, or ventilation, is insufficient, so carbon dioxide builds up in the blood. CO2 combines with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. The extra hydrogen ions increase acidity and cause the pH to fall. The relationship is captured by the equation pH = 6.1 + log([HCO3-]/(0.03 × PaCO2)); when PaCO2 rises, the ratio skews toward acidity, lowering pH. In the short term, pH drops due to CO2 retention. Over time, the kidneys can compensate by retaining bicarbonate, which can raise pH toward normal, but that is a compensatory process, not the immediate effect.