The BLUE-protocol is an ultrasound approach of lungs and veins, allowing with fine accuracies an immediate diagnosis of an acute respiratory failure among the six causes which regard 97% of patients seen in critical settings: hemodynamic pulmonary edema, pulmonary embolism, pneumonia, COPD, asthma and pneumothorax, mainly. The BLUE-protocol is a fast protocol (less than 3 minutes). It requires a simple unit, uses the ten basic signs of lung ultrasound, and associates signs with locations. Three standardized points per lung are used. BLUE-protocol includes a venous analysis, different from usual habits (we don’t detail), done in the case of normal anterior lung surface The BLUE-protocol generates eight profiles, half devoted to diagnose pneumonia. The A-profile is a “pre-profile”, designing anterior lung sliding with anterior A-lines. It shows normal lung surface, and rules out immediately pneumothorax and hemodynamic pulmonary edema. It generates three profiles. The A-DVT profile means that a DVT was detected, and is 99% specific to pulmonary embolism. The A-V-PLAPS-profile. The PLAPS (posterior or lateral alveolar and/or pleural syndrome) indicates the presence of alveolar and/or pleural change, uni- or bilateral, at a subposterior point accessible in supine patients with short probes, called PLAPS-point. Alone, a PLAPS has no specificiy. Associated to the A-profile, when the venous network is free, it indicates (posterior) pneumonia with 89% accuracy. The nude profile, defined by the A-profile, absence of visible DVT and absence of PLAPS. It is usually associated to asthma or COPD (two diseases gathered because therapy is roughly similar). The B-profile, designing anterior lung sliding with anterior lung rockets indicates usually hemodynamic pulmonary edema. It rules out asthma, COPD, pulmonary embolism. The B-prime profile is a B-profile with abolished lung sliding. It is quite specific to pneumonia (100%). The A-prime profile is an A-profile with abolished lung sliding. It is highly suggestive of pneumothorax. The detection of a lung point will confirm the diagnosis and indicate the size of the pneumothorax. The A/B profile is an half A-profile at one lung, and an half B-profile at the other. It is quite specific to pneumonia. The C-profile indicates anterior lung consolidation, regardless size and number. A minima, it can just give the illusion of an irregular pleural line. It is quite specific to pneumonia (98%). 0One of the most frequent questions regards the non inclusion of the heart in the decision tree. This analysis is associated, not included, to the BLUE-protocol, which makes a direct analysis of the lung (the suffering organ). A simple cardiac sonography, without Doppler, will provide, at this step, major information, if needed. All these data are gathered in a traditional clinical approach, the aim is to provide quick relief of acute dyspnea, and decrease of use of irradiating tests. The BLUE-protocol is at best taught in authorized centres. It uses simple machines, one whole body probe for lungs, veins, heart, others. The BLUE-protocol is a typical illustration of holistic ultrasound.