Bohr equation for physiologic dead space: PaCO2 40 mmHg, PeCO2 28 mmHg. What is Vd/Vt?

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Multiple Choice

Bohr equation for physiologic dead space: PaCO2 40 mmHg, PeCO2 28 mmHg. What is Vd/Vt?

Explanation:
The concept being tested is how the Bohr equation uses the CO2 difference between arterial blood and expired gas to quantify physiologic dead space. The equation is Vd/Vt ≈ (Paco2 − PeCO2) / Paco2. Here, PaCO2 is 40 mmHg and PeCO2 is 28 mmHg, so Vd/Vt = (40 − 28) / 40 = 12/40 = 0.30. This means about 30% of the tidal volume does not participate in gas exchange. That value sits within the normal range (roughly 0.2–0.35). A larger difference would indicate more dead space ventilation.

The concept being tested is how the Bohr equation uses the CO2 difference between arterial blood and expired gas to quantify physiologic dead space. The equation is Vd/Vt ≈ (Paco2 − PeCO2) / Paco2. Here, PaCO2 is 40 mmHg and PeCO2 is 28 mmHg, so Vd/Vt = (40 − 28) / 40 = 12/40 = 0.30. This means about 30% of the tidal volume does not participate in gas exchange. That value sits within the normal range (roughly 0.2–0.35). A larger difference would indicate more dead space ventilation.

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