Respiratory System Structure and Gas Exchange (3B) Practice Test

In an ex vivo perfused-lung experiment, investigators decreased alveolar surface area by selectively collapsing a fraction of alveoli while keeping the remaining alveoli ventilated and perfused. Total pulmonary blood flow and inspired O$_2$ fraction were held constant. Which result is most consistent with this manipulation?

A physiologic study induced bronchoconstriction in a subset of airways using an inhaled agent, creating regions with low ventilation relative to perfusion. Mixed venous blood entering the lungs was unchanged. Which arterial change is most consistent with this ventilation–perfusion mismatch?