N. K. Burki, MD, PhD

ABSTRACT: The rate at which acute dyspnea develops can point to its cause. A sudden onset strongly suggests pneumothorax (especially in a young, otherwise healthy patient) or pulmonary embolism (particularly in an immobilized patient). More gradual development of breathlessness indicates pulmonary infection, asthma, pulmonary edema, or neurologic or muscular disease. A chest film best identifies the cause of acute dyspnea; it can reveal pneumothorax, infiltrates, and edema. Pulmonary embolism is suggested by a sudden exacerbation of dyspnea, increased ventilation, and a drop in PaCO2. A normal chest radiograph reinforces the diagnosis of pulmonary embolism, which can frequently be confirmed by a spiral CT scan of the chest. Pneumonia can be difficult to distinguish from pulmonary edema. In this setting, bronchoalveolar lavage and identification of the infectious organism may be necessary to differentiate between the 2 disorders.