Which condition is defined by PCO2 below 35 mmHg due to severe anxiety or hypoxia?

Which condition is defined by PCO2 below 35 mmHg due to severe anxiety or hypoxia?

• A. Respiratory acidosis
• B. Respiratory alkalosis
• C. Metabolic acidosis
• D. Metabolic alkalosis

Answer: (B)

Low PCO2 (<35 mmHg) due to rapid breathing from anxiety or hypoxia signals respiratory alkalosis. When ventilation increases, more CO2 is washed out of the blood, lowering PaCO2. Since CO2 forms carbonic acid in the blood, its decrease raises pH, producing alkalemia. The body can compensate over time by kidneys excreting bicarbonate, which helps bring pH back toward normal. This differs from metabolic disorders, where the primary change is in bicarbonate rather than CO2; respiratory acidosis would involve high CO2 from reduced ventilation, and metabolic disturbances involve bicarbonate shifts independent of ventilation.

Low PCO2 (<35 mmHg) due to rapid breathing from anxiety or hypoxia signals respiratory alkalosis. When ventilation increases, more CO2 is washed out of the blood, lowering PaCO2. Since CO2 forms carbonic acid in the blood, its decrease raises pH, producing alkalemia. The body can compensate over time by kidneys excreting bicarbonate, which helps bring pH back toward normal. This differs from metabolic disorders, where the primary change is in bicarbonate rather than CO2; respiratory acidosis would involve high CO2 from reduced ventilation, and metabolic disturbances involve bicarbonate shifts independent of ventilation.