A 60-Year-Old Man Comes to Your Office Complaining of Dyspnea

Multiple Choice

A 60-year-old man comes to your office complaining of dyspnea (difficult breathing) . His laboratory values are as follows: $\begin{array}{|l|l|l|}\hline& \text {Breathing}& \text {Breathing \( 100 \% \) }\\& \text {air}& \text {\(\mathrm{O}_{2} \text { for } 7 \text { minutes }\) } \\\hline \text { Arterial } \mathrm{PO}_{2}(\mathrm{mmHg}) & 76 & 500 \\\hline \text { Arterial } \mathrm{PCO}_{2}(\mathrm{mmHg}) & 55 & 65 \\\hline \text { Arterial } \mathrm{Hb}(\mathrm{g} / 100 \mathrm{~mL}) & 18 & 18 \\\hline \text { Arterial } \mathrm{O}_{2} \text { saturation (\%) } & 85 & 100 \\\hline \text { Arterial } \mathrm{pH} & 7.35 & 7.20\\\hline\end{array}$
Which of the following diagnoses best explains the laboratory test findings?

A) Patent ductus arteriosus
B) Patent foramen ovale
C) Complete obstruction of the right bronchus
D) Thickened alveolar membrane impairing diffusion
E) Pulmonary fibrosis restricting lung movement