Unexplained dyspnea.

Dyspnea is a common symptom that is difficult to define and can result from a wide variety of causes. This complex sensation that arises from multiple stimuli involves both subjective perceptions and objective reactions. In the assessment of patients with dyspnea, use of a systematic approach to determine the precipitating factors and the degree of breathlessness is important. Although many diseases may produce dyspnea, two thirds of the cases result from a pulmonary or cardiac disorder. Neuromuscular and psychogenic causes should also be considered. A comprehensive history, physical examination, and basic laboratory tests are important in the initial assessment; however, the diagnosis may depend on specialized testing, the results of which may differ from the initial clinical impression. Initial testing should include electrocardiography, chest roentgenography, hemoglobin determination, thyroid function, and spirometry with use of a bronchodilator. More specialized evaluation includes detailed pulmonary function testing and echocardiography. As shown in our illustrative case, cardiopulmonary exercise testing is important for evaluation of unexplained dyspnea when initial test results are nondiagnostic. Accurate diagnostic data are critical for choosing appropriate treatment.