A 58-year-old woman presented to our hospital with progressive breathlessness and cough. Her cough, which had not responded to empiric antibiotic therapy initiated by her family physician, had initially developed 6 weeks previously. Two weeks prior to hospital admission, she noted worsening of the cough and the development of breathlessness, with the result that her usually unlimited exercise tolerance was reduced to approximately 20 yards. Her previous medical, occupational, and travel histories were unremarkable, and she had been receiving no regular medication. She was currently a smoker with a total of 20 pack-years. On examination, the patient was centrally cyanosed with resting oxygen saturations of 78% while breathing room air. Her jugular venous pressure was elevated, and there was moderate peripheral ankle edema that was compatible with right heart failure. An examination of her chest revealed a dull percussion note and reduced breath sounds throughout the right hemithorax. Arterial blood gas analysis performed with the patient breathing 1 L of oxygen via nasal cannula demonstrated the following results, consistent with acute-on-chronic type II respiratory failure: pH, 7.27; Po2, 101.5 mm Hg; Pco2, 82.0 mm Hg, and bicarbonate concentration, 36 mmol/L. Renal and liver function test results were normal, as were hematologic parameters, including a CBC with cell differential.