6) With increasing altitude, the air becomes thinner, gas molecules are farther

Question

6) With increasing altitude, the air becomes thinner, gas molecules are farther apart, so atmospheric pressure decreases. Atop a 10,000 mountain peak atmospheric pressure is 523 mm Hg. Oxygen still accounts for 21% of the total pressure. Calculate PO2 at this elevation. ________mm (2 pts)

   How does this compare to the PO2 at sea level? (1 pt)

What effect would this elevation have on the pressure gradient between alveolar air and alveolar blood – increase, decrease or no change? (1 pt)

What effect would this pressure gradient have on the ability of oxygen to move into blood – increase, decrease or no change? Explain your answer. (2 pts)

Explanation / Answer

At 10000 mountain peak, atmospheric pressure is 523 mm Hg and pO2 concentration in atmospheric pressure is 21%. So pO2 at that level will be 21% of 523 that is 109.83 mmHg.

At sea level, atmospheric pressure is 760 mmHg and pO2 is around 160 mmHg. Partial pressure of oxygen decreases as the altitude is increased. So at mountain peak PO2 is less than that at sea level.

At this mountain peak, pressure gradient between alveolar air and alveolar blood will decrease because of fall in partial pressure of oxygen in atmosphere.

At mountain peak, decrease in pressure gradient between alveolar air and alveolar blood will decrease the ability of oxygen to move in to blood. This is because the air moves toward the pressure gradient and if this gradient is less the flow rate of oxygen in to the blodd decreases.

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