Looking at the Whole Picture

A CLINICAL PROBLEM-SOLVING article by Carol Donagh, Galway University Hospital, Ireland.
A 50-year-old woman presented with rapidly progressive shortness of breath. Five months earlier, she had received a diagnosis of invasive breast carcinoma and had undergone mastectomy. Her fifth cycle of chemotherapy was completed 10 days before presentation.
On examination, an arterial blood gas analysis showed a pH of 7.47, a partial pressure of oxygen of 49 mm Hg, and a partial pressure of carbon dioxide of 31 mm Hg. A chest radiograph showed no focal abnormality. A transthoracic echocardiogram revealed normal biventricular function, normal valves, and an estimated pulmonary-artery pressure of 22 mm Hg.
This degree of hypoxemia in a patient with a clear lung examination and a normal chest X-ray increases physician's suspicion that she has a pulmonary embolism of thrombotic, septic, or cancerous origin is most likely, given the underlying breast cancer, potential hypercoagulability, and presence of an infusion port.
CT pulmonary angiography showed no filling defects in the pulmonary artery, and the lung parenchyma appeared normal. On the fifth hospital day, after a brief mobilization from her bed to a chair, the oxygen saturation decreased to 78% while the patient was breathing ambient air. The nurses noted that the patient's hypoxemia was substantially worse when she was lying on her left side. [Original Articles]