A Review of Early Experience in Lung Ultrasound in the Diagnosis and Management of COVID-19

Abstract

A novel coronavirus (2019-nCoV) was identified as the cause of a cluster of pneumonia in Wuhan, China, at the end of 2019. Since then more than eight million confirmed cases of coronavirus disease 2019 (COVID-19) have been reported around the globe. The current gold standard for etiologic diagnosis is reverse transcription-polymerase chain reaction analysis of respiratory-tract specimens, but the test has a high false-negative rate owing to both nasopharyngeal swab sampling error and viral burden. Hence diagnostic imaging has emerged as a fundamental component of current management of COVID-19. Currently, high-resolution computed tomography is the main imaging tool for primary diagnosis and evaluation of disease severity in patients. Lung ultrasound (LUS) imaging has become a safe bedside imaging alternative that does not expose the patient to radiation and minimizes the risk of contamination. Although the number of studies to date is limited, LUS findings have demonstrated high diagnostic sensitivity and accuracy, comparable with those of chest computed tomography scans. In this note we review the current state of the art of LUS in evaluating pulmonary changes induced by COVID-19. The goal is to identify characteristic sonographic findings most suited for the diagnosis of COVID-19 pneumonia infections.

Keywords: COVID-19; coronavirus; lung imaging; lung ultrasound; pneumonia; point of care ultrasound (POCUS).

Fig. 1

Normal aerated lung ultrasound showing the horizontal reverberation artifacts (A-lines) of the pleural line (red arrows). The characteristic appearance of two ribs and the pleural line in between is often referred to the “bat sign.” Reprinted with permission from Miller (2016).

Fig. 2

M-mode image for a normal lung, demonstrating lung sliding (the “seashore sign”). Reprinted with permission from Miller (2016).

Fig. 3

Probe positioning according to the BLUE protocol. Reprinted with permission from Miller (2016).

Fig. 4

Lung ultrasound image showing vertical artifacts (B-lines) indicating the presence of a pathology associated with increase in lung tissue density. Reprinted with permission from Miller (2016).

Fig. 5

Lung ultrasound image showing a small anterior consolidation area with indistinct margins (red arrow). Reprinted with permission from Miller (2016).

Fig. 6

Lung ultrasound images of multiple COVID-19 cases demonstrating different patterns of B-lines. (a) B-lines and waterfall sign in the right posterior upper area (red arrow), with an unsmooth pleural line. (b) The pleural line in the right posterior lower area is unsmooth and thin, with diffused B-lines and white-lung sign; A-lines have disappeared. (c) B-lines in the left posterior lower area, with A-lines having disappeared; small patchy lesions are observed, and the pleural line is discontinuous (red arrow). Reprinted with permission from Huang et al. (2020).

Fig. 7

Lung ultrasound images for confirmed COVID-19 cases obtained with a linear-array probe showing pleural-line irregularities. (a) The local pleural line in the right posterior lower area is unsmooth and the roughness is discontinuous. (b) The pleural line in the left posterior upper area is interrupted and discontinuous. Reprinted with permission from Huang et al. (2020).

Fig. 8

Lung ultrasound images acquired using a linear-array probe. (a) Interrupted pleural line and patchy consolidation in the left posterior lower area, with fixed B-lines. The origin point is round and dull, and the subpleural area thickened. Color Doppler flow imaging shows no blood flow signal. (b) The pleural line in the right posterior upper area is interrupted and disappears. There is an air bronchogram sign in the strip and faint consolidation, and the connecting surface of the lung tissues is rough and unsmooth, with B-lines. (c) Discontinuous pleural line in the right posterior lower area and strip consolidation and air bronchogram sign, with a large number of B-lines. Reprinted with permission from Huang et al. (2020).

Fig. 9

Lung ultrasound image for confirmed COVID-19 patient scanned with a convex-array probe showing large areas of consolidation in the right posterior upper area and air bronchogram sign (yellow arrow). The pleural line is interrupted. Reprinted with permission from Huang et al. (2020).

Fig. 10

Color Doppler ultrasound image for confirmed COVID-19 case showing no blood flow signal in the peri-pulmonary consolidation of the left posterior upper area, a significantly different finding from that of common inflammatory bacterial pneumonia. Reprinted with permission from Huang et al. (2020).

Fig. 11

Serial lung ultrasound images from a 35-y-old emergency physician who tested positive for COVID-19. (a) Scattered B-lines in both lungs, with thickened pleural line, at an early stage of the disease. (b) Diffused B-lines (white-lung sign) with disease progression. (c) Subsequent subpleural consolidation in a later stage of the disease. Reprinted with permission from Tung-Chen (2020).