Lung Ultrasound in the Critically Ill.

Until recently, the lung was considered “forbidden territory” for ultrasound. With lung ultrasound, however, the amount of lung consolidation and pleural effusion can be assessed semiquantitatively. Lung ultrasound consists of the identification of 10 signs, and there are several well-established protocols such as the BLUE (Bedside Lung Ultrasonography in Emergency) protocol for diagnosing acute respiratory failure and the FALLS (Fluid Administration Limited by Lung Sonography) protocol for managing acute circulatory failure. The BLUE protocol is a fast protocol that defines eight profiles, correlated with six diseases seen in 97% of patients admitted to the intensive care unit (ICU). With this protocol, it becomes possible to differentiate between pulmonary edema, pulmonary embolism, pneumonia, chronic obstructive pulmonary disease, asthma, and pneumothorax [1]. The FALLS protocol uses the potential of lung ultrasound for the early demonstration of fluid overload at an infra-clinical level [2]. It is used in patients with acute respiratory failure, allowing a sequential search for obstructive, cardiogenic, hypovolemic, and distributive shock using simple real-time echocardiography in combination with lung ultrasound, with the appearance of B lines considered to be the endpoint of fluid therapy. In addition, ultrasound can help to guide airway management in a patient with acute respiratory distress who needs to be intubated and mechanically ventilated (PINK protocol). In a patient with acute respiratory distress who is often ventilated and difficult to transport, computed tomography (CT) is not an easy option, and lung ultrasound can help to predict difficult airway and proper endotracheal tube size, or to confirm proper endotracheal tube placement with avoidance of desaturation during CT [3]. In addition, lung ultrasound can be used to determine the cause of fever distinguishing pneumonia from atelectasis [4], and to rule out pneumothorax, hypovolemia, pulmonary embolism and pericardial tamponade in cardiac arrest (SESAME protocol) [5]. In the critical care setting, lung ultrasound is increasingly used, as it allows bedside visualization of the lungs. Critical care ultrasound is a combination of simple protocols, with lung ultrasound being a basic application, allowing the assessment