Question

Which of the following statements is not true?

• A. The partial pressure of oxygen in oxygenated blood is 95 mm Hg
• B. The partial pressure of oxygen in the alveolar air is 104 mm Hg
• C. The partial pressure of carbon dioxide in the alveolar air is 40 mm Hg
• D. The partial pressure of carbon dioxide in deoxygenated blood is 95 mm Hg

Answer 1

Answer: (D)

Each gas in the mixture exerts a part of the total pressure proportional to its concentration, ie, the partial pressure. This is denoted as “p”,e.g., pO₂, pCO₂.
Partial pressure (mm Hg) of respiratory gases

Tissues

O2	159	104	40	95	40
CO2	0.3	40	45	40	45