At high altitude (>5,000 feet), draw volume may be:

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Multiple Choice

At high altitude (>5,000 feet), draw volume may be:

The key idea is that gas volumes depend on ambient pressure. As you rise above 5,000 feet, barometric pressure falls. When you take a deep breath, the amount of air you can draw into the lungs is influenced by that external pressure. At lower ambient pressure, the same chest wall expansion does not push as many gas molecules into the lungs, so the drawn volume of gas (measured without correcting for pressure) is smaller. In other words, the lungs can move air, but the amount of air present per liter of ambient gas is less at higher altitude, so the measured draw volume decreases unless volumes are corrected to standard conditions (STPD). Clinically, this is why pulmonary function measurements taken at altitude often appear reduced unless you apply appropriate standardization.

The key idea is that gas volumes depend on ambient pressure. As you rise above 5,000 feet, barometric pressure falls. When you take a deep breath, the amount of air you can draw into the lungs is influenced by that external pressure. At lower ambient pressure, the same chest wall expansion does not push as many gas molecules into the lungs, so the drawn volume of gas (measured without correcting for pressure) is smaller. In other words, the lungs can move air, but the amount of air present per liter of ambient gas is less at higher altitude, so the measured draw volume decreases unless volumes are corrected to standard conditions (STPD). Clinically, this is why pulmonary function measurements taken at altitude often appear reduced unless you apply appropriate standardization.

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