PŘEHLEDOVÉ ČLÁNKY / REVIEW ARTICLES Imaging of COVID-19 in critical care with a focus on chest ultrasound | 65 / Anest intenziv Med. 2023;34(2):61-68 / ANESTEZIOLOGIE A INTENZIVNÍ MEDICÍNA www.aimjournal.cz the lungs is reproducible and can quantify pulmonary involvement [37–40]. A complete examination of all the lung zones (anterior and posterior divided by mid‑axillary line) needs to be performed. Each zone is scored in four degrees from 0-3 depending on the pattern of B‑lines and A‑lines that is visualised by the investigator. By assessing each zone, one should be able to describe and quantify the perceived lung changes which will eventually culminate to a score, the maximum of which is 36 (Tab. 1). An overall degree of alveolo‑interstitial syndrome can be quantified as mild disease (score 1-5), moderate disease (score 5-15), severe disease (score > 15) [15, 16, 37]. Pulmonary changes due to COVID-19 can be seen on CUS as an interstitial profile with singular or confluent B‑lines originating from the surface of the pleura and a thickened and irregular pleural line (resulting in diminished lung sliding). With further progression, small patchy subpleural consolidations are seen; then, the evolution and progression of these subpleural consolidations can be found in a picture mirroring the pattern of ARDS that would necessitate ventilatory support [7, 8, 13, 23] (Figs. 2 and 7). CUS can also help to triage a patient to admission to hospital or even to an intensive care unit. If a patient is exhibiting symptoms of COVID-19 and presents with the A‑pattern/profile, significant COVID-19 pneumonia can be largely excluded. With a progression from the prevailing A‑profile in the anterior and apical regions towards the B‑lines, the question raises as to how many B‑lines and what B‑line density there are as they correlate with ground‑glass opacities, consolidations, and crazy paving seen on a CT scan. The condition is easier to diagnose with progression to the confluent B‑lines, lung consolidation with or without dynamic bronchogram, and the 3rd to 4th degree of the alveolo‑interstitial syndrome often with pleural enhancement (Fig. 4). At this stage, CUS findings are highly specific for some of the advanced stages of ARDS including COVID-19 related (Fig. 6) and, therefore, the patient will likely require ICU admission [6, 23, 38, 41]. Volpicelli has suggested triaging patients based on CUS finding into four groups as follows: 1) high probability CUS pattern; 2) intermediate probability CUS pattern; 3) alternate CUS pattern; and 4) low probability CUS pattern [1, 41]. This triaging system also allows for finding probable alternate diagnoses that may be masquerading as the COVID-19 disease. The intermediate pattern with less dense B‑lines (e.g., B4-7) may not correlate with the aforementioned CT picture of COVID-19 interstitial pneumonitis or ARDS, and those patients may benefit from a CT examination to confer a differential diagnosis [6, 42] (Figs. 3 and 4). The high probability CUS group has been described as potentially indicating peripheral ground‑glass opacities on CT and, thus, as a compelling predictor of an impending positive RT‑PCR test. The light beam sign (described as a linear artefact seen emerging and disappearing with respiration) in early disease seen in the high probability LUS group has been described as a CUS sign potentially Fig. 6. CUS findings of severe COVID-19: A enhancing pleura with multiple B3-4 lines, B thickened pleura with coalescent B-lines on the left side of the image, correlating with ground-glass opacities; C thickened pleura due to inflammation; D pleural space after drainage of pneumothorax due to barotrauma; note the chest drain in between the pleural layers confirming full lung expansion (35); E coalescent B-lines, 3rd degree alveolo-interstitial syndrome and ARDS Tab. 1. CUS derived lung score, adapted from Bouhemad and Mongodi (37, 38). Pleural involvement is described as subpleural consolidations and thickened pleura. Tissue-like pattern = consolidation Lung score Description Classic interpretation on LUS Modified interpretation on LUS Score 0 Normal aeration A lines, 2 B-lines maximum A-lines, 2 B-lines maximum Score 1 Moderate loss of aeration ≥ well-spaced B lines Involvement of the pleura < 50 % Score 2 Severe loss of aeration Coalescent B lines Involvement of the pleura > 50 % Score 3 Complete loss of aeration Tissue-like pattern Tissue-like pattern
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