A 49-year-old man has a pulmonary embolism that completely blocks blood flow to his left lung. As a result, which of the following will occur?

Question

Quizplus · Accepted Answer

[VII B 2]. Alveolar $\mathrm{P}_{2}$ in the left lung will equal the $\mathrm{PO}_{2}$ in inspired air. Because there is no blood flow to the left lung, there can be no gas exchange between the alveolar air and the pulmonary capillary blood. Consequently, $\mathrm{O}_{2}$ is not added to the capillary blood. The ventilation/perfusion (V/Q) ratio in the left lung will be infinite (not zero or lower than that in the normal right lung) because $\mathrm{Q}$ (the denominator) is zero. Systemic arterial $\mathrm{PO}_{2}$ will, of course, be decreased because the left lung has no gas exchange. Alveolar $\mathrm{PO}_{2}$ in the right lung is unaffected.

A 49-Year-Old Man Has a Pulmonary Embolism That Completely Blocks PO2\mathrm{PO}_{2}PO2​

A 49-Year-Old Man Has a Pulmonary Embolism That Completely Blocks $\mathrm{PO}_{2}$