The use of bedside lung ultrasound (LUS) is extremely impactful in the first approach to suspected COVID-19 pneumonia. The LUS signs of interest in COVID-19 include all those which are well known in human ARDS. However, in the diagnosis of COVID-19 some specificities need to be considered.

B-Lines

We may describe COVID-19 pneumonia as a storm of clusters of B-lines, both in separate and coalescent forms, sometimes giving the appearance of a shining white lung. They arise from the pleural line or from small peripheral consolidations and spread down like rays maintaining their brightness without fading. These artifacts represent the typical signs of the disease but can be also observed in other interstitial diseases of various etiologies. However, we observed that one aspect of these artifacts is invariably visualized in pneumonia from COVID-19. It is a shining band-form artifact spreading down from a large portion of a regular pleura, often appearing and disappearing with an on-off effect in the context of a normal A-lines lung pattern visible on the background. This sign is demonstrative of a very acute phase of the early spread of the active disease, when limited areas of viral lesions, corresponding to the ground glass opacities seen at CT scan, alternate with lung parenchyma not yet involved. We think that the name “light beam” more faithfully describes this artifact, because it resembles a large beam of light appearing and disappearing during respiration.

LUS Patterns

All the LUS signs of COVID-19 pneumonia, including the light beam, can be observed in a variety of different lung conditions. However, what gives specificity to LUS is the distribution of the pattern. Bilateral patchy distribution of multiform clusters with representation of all these signs together, sharply alternated to “spared areas,” is typical of the disease. Included in the clusters, evidence of the light beam is crucial to assign a diagnosis of high probability of COVID-19 pneumonia. Any other combination of signs should be considered at intermediate probability and should demand further testing. Finally, some patterns allow to rule-out the disease and orientate towards alternative diagnoses. For instance, a regular pleural line with uniform, homogeneous, and symmetric distribution of B-lines at an intensity that is proportional to the severity of respiratory symptoms, is typical of cardiogenic pulmonary edema. Diffuse irregularities of the pleural line without the typical patchy distribution are more typical of chronic diffuse pulmonary diseases, like fibrosis. Isolated large lobar consolidation with or without effusion and with air bronchograms indicates bacterial infection. Large pleural effusion with atelectatic consolidation of the base of the lung and signs of peripheral recruitment during inspiration demonstrate a compressive origin of the lung condition. The presence of echoic septa or other images inside the effusion demonstrates a different origin of the infection, as SARS-CoV-2 does not give exudate.

The combinations of LUS signs and patterns with the patient’s clinical presentation, including presence or absence of respiratory failure and other confounding respiratory diseases, allow for a LUS guided first diagnosis of COVID-19 pneumonia.

References

References are available upon request.