In an upright person, which region of the lung has the highest ventilation and perfusion?

In an upright person, which region of the lung has the highest ventilation and perfusion?

• A. Apex
• B. Middle region
• C. Uniform throughout
• D. Base of the lung

Answer: (D)

Gravity creates a vertical gradient in both air reaching the alveoli and blood flowing through the pulmonary vessels. In an upright person, the base sits lower, so hydrostatic pressure in the pulmonary capillaries is higher there, driving more blood to the base and delivering greater perfusion. Ventilation is also greatest at the base because the alveoli there are more compliant and expand more with each breath, whereas the apical alveoli are already stretched and less expandable. So the base region receives more air per breath as well. Putting it together, the base of the lung has the strongest combination of ventilation and perfusion in an upright person, even though the ventilation–perfusion ratio is higher at the apex and lower at the base.

Gravity creates a vertical gradient in both air reaching the alveoli and blood flowing through the pulmonary vessels. In an upright person, the base sits lower, so hydrostatic pressure in the pulmonary capillaries is higher there, driving more blood to the base and delivering greater perfusion.

Ventilation is also greatest at the base because the alveoli there are more compliant and expand more with each breath, whereas the apical alveoli are already stretched and less expandable. So the base region receives more air per breath as well.

Putting it together, the base of the lung has the strongest combination of ventilation and perfusion in an upright person, even though the ventilation–perfusion ratio is higher at the apex and lower at the base.