Acute dyspnea is a frequent cause of access to the Emergency Department. Differentiation between cardiogenic and respiratory causes does not always seem simple and certain, causing a delay in initiating targeted therapies and prolonging the patient's stay in the emergency department. The basic elements for the diagnosis remain the history and the objective examination, supplemented by the execution of an electrocardiogram, a determination of blood parameters and the execution of a chest X-ray. The limits of radiological semeiotics, related to a low sensitivity to high specificity, promote other methods available to the first aid physician. Specifically, the determination of the natriuretic B-type peptide and transthoracic ultrasound is proposed as a method, recognized and validated by the recent letter on the patient bed, relatively easy to execute, fast learning, fast execution and non-invasive (referring to "ultrasound"). The sensitivity and specificity of both methods are high (86.7% and 93%, respectively) in the diagnosis of alveolus-interstitial syndrome, simplifying and accelerating the differential diagnosis of acute dyspnea.