Which of the following is TRUE about paial pressures of alveolar gases?
In a normal person, the mixed venous paial pressure of carbon dioxide is 45 mm Hg and alveolar paial pressure of carbon dioxide is 40 mm Hg. An equilibrium is reached in about 0.25 of a second, or about the same time as that for oxygen. The diffusivity of carbon dioxide is about 20 times that of oxygen, but the paial pressure gradient is normally only about 5 mm Hg for carbon dioxide, whereas it is about 60 mm Hg for oxygen. Carbon dioxide transfer is therefore normally perfusion-limited, although it may be diffusion-limited in a person with an abnormal alveolar-capillary barrier. Ref: Levitzky M.G. (2007). Chapter 6. Diffusion of Gases. In M.G. Levitzky (Ed), Pulmonary Physiology, 7e.
Alveolar PCO2 is more than mixed venous pCO2
Alveolar pO2 is less than pO2 of expired air
Alveolar pCO2 is twice that of the room air
Mixed venous pCO2 is more than alveolar pCO2