A 64-year-old woman is admitted to the hospital after the acute onset of left-sided weakness. She has had a large right cerebral stroke and is confined to bed. On the fifth hospital day, her oxygen saturation is noted to be reduced to 90% on room air. She feels fine, the neurologic weakness is unchanged, blood pressure is 130/90 mm Hg, and pulse 80/min. Examination of the chest reveals decreased fremitus, dullness to percussion, and absent breath sounds in the left lower lung. There is also a tracheal shift towards the left side.For the above patient with abnormal pulmonary physical findings, select the most likely diagnosis.

Careful physical examination can be very useful in diagnosing many common pulmonary disorders. Atelectasis and large pleural effusions both can present with decreased fremitus, dullness or flatness to percussion, and absent breath sounds. In atelectasis, tracheal shift, if present, is toward the affected side, and the opposite for a large pleural effusion. Asthma's most typical manifestations are prolonged expiration and diffuse wheezing. However, impaired expansion, decreased fremitus, hyperresonance, and low diaphragms can also be found. A complete pneumothorax results in absent fremitus, hyperresonance or tympany, and absent breath sounds. Lobar pneumonia is characterized by consolidation with increased fremitus, dullness, and auscultatory findings of bronchial breathing, bronchophony, pectoriloquy, and crackles.