Which acid-base disturbance is expected in a patient who is hyperventilating due to anxiety?

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Multiple Choice

Which acid-base disturbance is expected in a patient who is hyperventilating due to anxiety?

When ventilation drives the disturbance, the key is how CO2 levels affect acidity. Hyperventilating from anxiety means you blow off carbon dioxide faster than it’s produced. CO2 combines with water to form carbonic acid, which releases hydrogen ions and lowers pH. If CO2 is removed rapidly, there are fewer hydrogen ions, so pH rises. That shift creates respiratory alkalosis: low CO2, high pH, due to increased respiration. In contrast, not changing breathing rate would not cause alkalosis; retaining CO2 from hypoventilation would cause respiratory acidosis (low pH, high CO2). Metabolic disturbances would involve changes in bicarbonate or acid production independent of CO2, which isn’t driven by the breathing pattern in this scenario. So the immediate effect of anxiety-driven hyperventilation is respiratory alkalosis.

When ventilation drives the disturbance, the key is how CO2 levels affect acidity. Hyperventilating from anxiety means you blow off carbon dioxide faster than it’s produced. CO2 combines with water to form carbonic acid, which releases hydrogen ions and lowers pH. If CO2 is removed rapidly, there are fewer hydrogen ions, so pH rises. That shift creates respiratory alkalosis: low CO2, high pH, due to increased respiration.

In contrast, not changing breathing rate would not cause alkalosis; retaining CO2 from hypoventilation would cause respiratory acidosis (low pH, high CO2). Metabolic disturbances would involve changes in bicarbonate or acid production independent of CO2, which isn’t driven by the breathing pattern in this scenario. So the immediate effect of anxiety-driven hyperventilation is respiratory alkalosis.

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