A 52-Year-Old Man Is Found to Be Tachypneic on the Second

question 499

Multiple Choice

A 52-year-old man is found to be tachypneic on the second day after an uncomplicated upper abdominal ventral hernia repair.  Until now, his postoperative course had been unremarkable, and he has been treated with low-dose morphine for pain control.  The patient says he feels short of breath but has no chest pain.  He has an occasional cough with a small amount of early-morning sputum production.  Other medical conditions include hypertension and hyperlipidemia.  The patient is an active smoker with a 15-pack-year history.  Temperature is 36.7 C (98.1 F) , blood pressure is 123/79 mm Hg, pulse is 90/min, and respirations are 28/min.  BMI is 32 kg/m².  Physical examination shows decreased breath sounds at the right lung base without wheezes or prolonged expiration.  Heart sounds are normal.  There is abdominal distension and diffuse tenderness without rebound.  The surgical incision appears clean and dry.  Chest x-ray reveals a dense opacity at the right lung base.
Arterial blood gas analysis done on room air is most likely to show which of the following?

• A)pH 7.30, PaO₂ 70 mm Hg, and PaCO₂ 54 mm Hg
• B)pH 7.30, PaO₂ 110 mm Hg, and PaCO₂ 22 mm Hg
• C)pH 7.41, PaO₂ 98 mm Hg, and PaCO₂ 38 mm Hg
• D)pH 7.49, PaO₂ 70 mm Hg, and PaCO₂ 27 mm Hg
• E)pH 7.49, PaO₂ 110 mm Hg, and PaCO₂ 50 mm Hg