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Old 01-18-2012
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Default Uptake of gases

Figure 2-13 illustrates uptake of two gases (nitrous oxide and carbon monoxide) from alveolar air to pulmonary capillary blood. Based on this information what can we conclude about carbon monoxide?
FIG. 2-13




A.
it does not dissolve in blood

B.
it does not interact with hemoglobin

C.
it has equilibrated with pulmonary capillary blood

D.
it is a diffusion-limited gas
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D diffusion limited gas
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Ans D.......
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Old 01-19-2012
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Ans C

CO is very soluble so it will equillibrate with blood
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The plot shows that carbon monoxide fails to equilibrate with pulmonary capillary blood during the time that blood is exposed to alveolar air. Since pulmonary partial pressure rises to only a few percent of alveolar partial pressure, carbon monoxide is a diffusion-limited gas. In contrast, nitrous oxide, which does equilibrate, is a perfusion-limited gas (choice E). Carbon monoxide does cross the respiratory membrane (choice C), dissolve in pulmonary capillary blood (choice A), and binds with hemoglobin (choice B). In fact, its affinity for hemoglobin is about 250-fold greater than that of oxygen.
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