For demonstrating that this dogma was wrong, deciphering the artifact code was the easy part, but publishing was the hard one, far from finished. Many doctors thought that lung ultrasound was unfeasible. At this time, although an old idea, ultrasound was not routine in the ICUs and had neglected this vital organ.

We used ultrasound first in 1983, on occasion in François Fraisse’s ICU in 1985–1989, then since 1989 in François Jardin’s ICU, using the on-site 1982 ADR-4000 devoted to cardiac assessment, in actual fact suitable for whole body and lung assessment and not larger than nowadays laptops. This review will show that ultrasound can be used instead of CT in many cases. Lung ultrasound would be of minor interest if the usual tools (bedside radiography, CT) did not have drawbacks (irradiation, low information content for radiography, need for transportation…). The possibility of exploring the lung using ultrasound, at the bedside and noninvasively, is gaining popularity among intensivists. The BLUE-protocol and FALLS-protocol allow simplification of expert echocardiography, a clear advantage when correct cardiac windows are missing. Its integration can provide a new definition of priorities. Lung ultrasound is a holistic discipline for many reasons (e.g., one probe, perfect for the lung, is able to scan the whole-body). A 1992, cost-effective gray-scale unit, without Doppler, and a microconvex probe are efficient.

Other aims of lung ultrasound are decreasing medical irradiation: the LUCIFLR program (most CTs in ARDS or trauma can be postponed), a use in traumatology, intensive care unit, neonates (the signs are the same than in adults), many disciplines (pulmonology, cardiology…), austere countries, and a help in any procedure (thoracentesis). It makes sequential search for obstructive, cardiogenic, hypovolemic, and distributive shock using simple real-time echocardiography (right ventricle dilatation, pericardial effusion), then lung ultrasound for assessing a direct parameter of clinical volemia: the apparition of B-lines, schematically, is considered as the endpoint for fluid therapy. Pulmonary edema, e.g., yields anterior lung rockets associated with lung sliding, making the “B-profile.” The FALLS-protocol adapts the BLUE-protocol to acute circulatory failure. Pulmonary edema, pulmonary embolism, pneumonia, chronic obstructive pulmonary disease, asthma, and pneumothorax yield specific profiles. It includes a venous analysis done in appropriate cases. The BLUE-protocol is a fast protocol (<3 minutes), which allows diagnosis of acute respiratory failure. All of these disorders were assessed using CT as the “gold standard” with sensitivity and specificity ranging from 90% to 100%, allowing ultrasound to be considered as a reasonable bedside “gold standard” in the critically ill. Two more signs, the lung pulse and the dynamic air bronchogram, are used to distinguish atelectasis from pneumonia. It requires the mastery of ten signs: the bat sign (pleural line), lung sliding (yielding seashore sign), the A-line (horizontal artifact), the quad sign, and sinusoid sign indicating pleural effusion, the fractal, and tissue-like sign indicating lung consolidation, the B-line, and lung rockets indicating interstitial syndrome, abolished lung sliding with the stratosphere sign suggesting pneumothorax, and the lung point indicating pneumothorax. Lung ultrasound is a basic application of critical ultrasound, defined as a loop associating urgent diagnoses with immediate therapeutic decisions.

Lung viscosity definition