Case 327.

A 58-year-old man who was an active smoker was admitted twice to the intensive care unit (ICU) of a tertiary referral thoracic center for severe hypercapnic acute respiratory failure and persistent bilateral chest radiograph opacities that were unchanged over the course of the two ICU admissions within a 3-month period (Fig 1). He had obesity (body mass index, 36 kg/m2), stage 3 vascular chronic renal insufficiency, and hebephrenic schizophrenia treated with haloperidol, carbamazepine, and cyamemazine. He reported chronic dyspnea on exertion, which worsened for 6 months. At the second ICU admission, he was afebrile, with a blood pressure of 160/72 mm Hg and pulse oximetry of 93% on 6 L/min oxygen therapy through a nonrebreathing mask. Physical examination showed signs of respiratory failure with wheezing and active abdominal expiration, bilateral pulmonary crackles without chest pain, hemoptysis, clubbing, or signs of cardiac failure. He had no peripheral lymphadenopathy and no enlarged spleen. Blood gases (on 6 L/min oxygen) showed respiratory acidosis (pH, 7.15 [normal range, 7.38-7.42]; Pao2 level, 67 mm Hg [normal range, 80-100 mm Hg]; Paco2 level, 102 mm Hg [normal range, 38-42 mm Hg]; Hco3- level, 29 mmol/L [normal range, 22-27 mmol/L]). Noninvasive ventilation was initiated. Imaging performed during the second ICU hospitalization included noncontrast chest CT (Fig 2), MRI of the chest without contrast enhancement (Fig 3), and fluorine 18 fluorodeoxyglucose PET/CT (Fig 4).