sis, ultrasound can be useful in the ICU and has also been used to monitor recovery from diaphragmatic paralysis [84].

Extrathoracic Lymph Nodes

Sonography using a high-frequency linear probe is a practice tool for the assessment of benign and malignant lymph nodes in conjunction with clini-

cal data. Lymph nodes appear on ultrasound as ovoid form structures with a relatively hypoechoic cortex and hyperechoic medulla because of the presence of hilum (Fig. 30.14a, b). Similar characteristics of lymph nodes are seen during the endobronchial ultrasound bronchoscopy (EBUS).

Some are long and thin and their center becomes larger during the healing reaction of an inflammatory process. The definitive assessment should be done by histological

confirmation; however, the existence of sonomorphological criteria can assist the physician in the study. A rounded shape, loss of the echogenic hilum, asymmetrical or nodular thickening of the cortex, and cystic necrosis are signs of malignant involvement [28] (Fig. 30.15a, b). Changes in size are seen in inflammatory processes (seldom exceed 20 mm) and malignant diseases. Extracapsular spread in a malignant node is characterized by a loss of clarity or irregularity of the node capsule. Microcalcifications may be seen within metastatic nodes from papillary and medullary thyroid carcinomas, breast cancer and in tuberculous infection. In tuberculosis, lymph

nodes may be enlarged and hypoechoic. Marked echogenic central zone, known as “hilar fat sign” represent fat and connective tissue in the center of an active lymph node. This sign is seen during the healing phase of inflammatory processes [28]. Age-related changes include cortical atrophy and fatty replacement [75, 85]. Ultrasound has a wellestablished role in the evaluation of extra-tho- racic lymph nodes, and reveals suspicious lymph nodes in a high number of patients with lung cancer. Guided biopsy in non-palpable nodes increases the possibility to prove malignat extension, that is N3/M1 stage, avoiding more invasive diagnostic procedures [86].

Intervention andTherapeutics Guided by Chest Ultrasound

There is little doubt that concerns about patient safety in pleural interventions have been a major driving force behind the increased uptake of CUS by clinicians other than radiologists over the past decade. Basic use of CUS allows the safe and accurate identifcation of pleural uid and other relevant anatomical structures, such as the underlying lung, heart, diaphragm, and abdominal viscera. The global evidence that supports the use of CUS as an adjunct to pleural intervention and the associated reduction in risk to patients is overwhelming (Fig. 30.16). CUS assessment should be considered an essential “gold standard” before any pleural intervention for suspected uid [86].

However, CUS does not guarantee appropriate site selection for intervention and might encourage clinicians to venture outside the anatomical safe triangle, since uid is often most easily seen

posteriorly where the costodiaphragmatic recess permits the greatest accumulation with the patient sitting upright.

The role played by CUS in improving patient safety does not end when the procedure begins. Other than providing the ability to allow real-­time guidance of any pleural intervention, CUS also offers the operator an opportunity to identify any iatrogenic complications as early as possible. Postprocedural ultrasound screening at the site of intervention can identify either active bleeding from the parietal pleural surface or the rapid accumulation of highly echogenic uid within the pleural space, demonstrating a swirling or gradient effect as heavier cellular material is deposited in the more dependent part of the collection (Fig. 30.17).

CUS can be used to recognize iatrogenic pneumothorax following procedures such as thoracentesis, transbronchial lung biopsy or image-­ guided lung biopsy, using key ultrasonographic features such as the presence of a lung point, or absence of B-lines and lung sliding.

COVID and Chest Ultrasound

CUS use has increased as a diagnostic and monitoring tool in critically-ill patients [87]. Ultrasonographic patterns mentioned previously have been useful for assessing pneumonia, atelectasis, pleural effusion, pulmonary edema, pneumothorax, and acute respiratory distress syndrome (ADRS) [88, 89], as well as for monitoring respiratory response in patients with invasive ventilation [90, 91]. In this regard, lung ultrasound score (LUS) is a semiquantitative index for assessing lung aeration loss and prediction of clinical outcomes in acute severe coronavirus disease 2019 (COVID-19) patients [92]. LUS evaluates lung parenchyma following a twelve-zone examination of the thorax [93]. Anterior (midclavicular line), lateral (midaxillary line), and posterior (paravertebral line) chest regions are divided in two (superior and inferior) (Fig. 30.18a, b). Posterior exploration is performed when a patient is able to sit or tilt sideways. When this is not possible, it was substituted

with posterior axillary line exploration. Both high or low-frequency transducers can be used, though linear high-frequency probe is preferred because of the defnition of pleural line. The transducer is placed longitudinal to the ribs to enhance the acoustic window. Each region is then scored following recommendations for point-of-­ care CUS [94]: lung sliding with A-lines or fewer than three isolated B-lines score 0; multiple well-­ defned B-lines (B1) score 1; multiple coalescent B-Lines (B2) or white lung score 2; and subpleural consolidation (C-profle) scores 3 (Fig. 30.19). The sum of the scores defned the LUS, ranging from 0 to 36 points [93]. A LUS ε 24 points is associated with a poor outcome at 30 days (ICU admission and mortality). The presence of B2-lines and C-profle is related to different thoracic CT-scan features such as consolidation and ground glass opacity; and are also related to lung fbrosis and diffuse alveolar damage in lung parenchyma [92]. LUS can be used in the followup­ in COVID-19 patients, in addition to diaphragmatic examination.