Dyspnea is a subjective symptom perceived by the patient as a sensation of breathing discomfort, suffocation, lack of air or difficulty inhaling or exhaling. It is a frequent reason for calling for help (8% of calls). The most seriously ill patients require the dispatch of specialized teams capable of initiating respiratory support in order to reduce the morbidity and mortality of these patients. In France, these teams are medicalized by an emergency physician within the Mobile Emergency Resuscitation Services (SMUR). This is only rarely the case outside France, where specialized paramedical teams (advanced life support paramedic teams) can be dispatched. Apart from their role of initiating possible respiratory support, these teams (SMUR or paramedics) can initiate a diagnostic approach and therapeutics related to the suspected origin of dyspnea. However, there are many diagnoses that can cause dyspnea, and the diagnostic process can be complex. The most common diagnoses described in the prehospital population are: bacterial pneumonia, acute heart failure, and exacerbation of COPD or asthma or pulmonary embolism. Each of these diagnoses requires specific drug treatment, guided by international recommendations. Inappropriate treatment of these pathologies (overtreatment or undertreatment) is common and associated with excess intrahospital mortality. Pleuropulmonary ultrasound (PUS) has shown very interesting diagnostic performance in the intrahospital setting for diagnoses of interest in dyspnea. This performance also appears good in the prehospital setting. In the intrahospital setting, PUS appears to improve the diagnostic approach and appropriate treatments for dyspnea. In the prehospital setting, however, data on this subject are scarce or of limited quality according to the most recent meta-analysis, while the use of this technique is becoming increasingly common in standardized patient care. In addition, the most recent work on the subject included patients in a non-medicalized prehospital system. The use of PUS would allow paramedics to increase the rate of appropriate treatment from 14% to 53%. However, the rate of appropriate treatment expected by a medicalized team is expected to be 62%, and the diagnostic performance of physicians in PUS is probably higher than that of paramedics. These data must therefore be consolidated in a French system before being the subject of higher-level recommendations. The systematic use of PUS during prehospital engagement of a SMUR for dyspnea also may improves the rate of appropriate treatment, even in a context of medicalization of the initial care of patients.