What might be responsible for his lowered vital capacity

Vacuum

760 mm

Vacuum

760 mm

Atmospheric pressure

Sea level

Atmospheric pressure

Sea level

■ Figure 16.19 The measurement of atmospheric pressure.

Atmospheric pressure at sea level can push a column of mercury to a height of 760 millimeters. This is also described as 760 torr, or one atmospheric pressure.

Inspired air

Alveolar air

h2o

Variable

47 mmHg

CO2

000.3 mmHg

40 mmHg \

O2

159 mmHg

105 mmHg \

N2

601 mmHg

568 mmHg )

Total pressure

760 mmHg

760 mmHg

■ Figure 16.20 Partial pressures of gases in inspired air and alveolar air at sea level. Notice that as air enters the alveoli its oxygen content decreases and its carbon dioxide content increases. Also notice that air in the alveoli is saturated with water vapor (giving it a partial pressure of 47 mmHg), which dilutes the contribution of other gases to the total pressure.

These two gases thus contribute about 99% of the total pressure of 760 mmHg:

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Essentials of Human Physiology

Essentials of Human Physiology

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