A 43-year-old woman comes to the physician for a 1-week history of shortness of breath. Physical examination shows no abnormalities. Laboratory studies are shown:
Arterial pCO2 31 mmHg
Arterial pO2 90 mmHg
Arterial O2 content 13% (NR 17-21)
Which of the following is the most likely explanation for these findings?
Edema secondary to increased pulmonary capillary hydrostatic pressure
Edema secondary to reduction of pulmonary capillary oncotic pressure
Methemoglobinemia
Mismatch of A-a gradient
Residence at high altitude
