An 84-year-old woman is admitted to the hospital because of wet gangrene on her right leg. Two days after admission, she becomes increasingly confused and tachypneic. She is intubated and ventilatory support is initiated. ABG shows a PCO2of 41 mm Hg and a PO, of 55 mm Hg. Despite appropriate care, the patient dies from respiratory failure. Further evaluation of this patient is most likely to show which of the following findings?