COVID-19 and Lung Ultrasound: Reflections on the "Light Beam".

During the COVID-19 pandemic Lung Ultrasound (LUS) has clearly succeeded as a formidable tool in the management of SARS-CoV-2 infection. A multitude of scientific papers, webinars and social media discussions has celebrated LUS benefits in the last few months, more than ever. LUS is based on the interpretation of artifacts, and different combinations of basic LUS artifacts can detect different pathologies. We discuss the need to identify new artifacts for new diseases.

The COVID‐19 pandemic is posing several challenges and every health system worldwide is struggling. At the beginning of this pandemic, we published a provocative article suggesting to routinely use “more ultrasound and less stethoscope” in the evaluation of suspected COVID‐19 patients. In particular, we highlighted one benefit: the possibility of obtaining clinical examination, blood tests and imaging at bedside with one operator, allowing a comprehensive examination, reducing the risk of SARS‐CoV‐2 exposure of other health workers and stratifying the patient's risk. Since then, there has been an explosion of literature, webinars and social media discussions on the role of Lung Ultrasound (LUS) during the COVID‐19 pandemic. In our Institution, we documented that LUS performed in the emergency department has a predictive role in determining the outcome of the patient, in terms of need of admission, death or failure of ventilation (submitted).

We read with great interest the article by Volpicelli and colleagues. They described an artifact that named “light beam”, “being observed invariably in most patients with COVID‐19 pneumonia”, a “broad, lucent, band‐shaped, vertical artifact moves rapidly with sliding, at times creating an “on–off” effect”, “arises from an entirely regular pleural line interspersed within areas of normal pattern or with separated B‐lines”. In their opinion, this is a “typical artifact”, consistent with the “patchy” localizations of COVID‐19 pneumonia.

We use LUS routinely in our practice. We report, as examples, two cases of pulmonary tuberculosis (supplementary video 1 and 2) in which we noticed LUS features suggestive of “light beam”. In these cases, as in those described by Volpicelli, LUS shows well‐defined, focal areas of confluent B lines.

LUS evaluates artifacts generated by the ultrasound/air interaction. Being artifacts, they are influenced by the machine, probe, settings, and probe positioning. Also in their paper, the light beam showed on “Video_Add_Convex1” is not seen on “Video_Add_Linear1” using a different probe.

The physical bases of artifacts are still far from being explained, although Soldati and colleagues have been studying these issues for years. Not by chance, researchers of the Italian Academy of Thoracic Ultrasound proposed a standardization of the acquisition protocol of LUS in COVID‐19 patients, stressing mainly the need to share the acquisition protocol, including the machine settings, and developed free software to collect videos from all over the world in order to understand, all together, the role of LUS in the COVID‐19 pandemic. The main semeiotic of LUS artifacts is still based on A‐lines, vertical artifacts (isolated or confluent), white lung, pleural effusions and consolidations. We are of the opinion that the light beam is a patchy area of white lung, as we see it in several conditions. Other terms could generate confusion, particularly if they are given at the beginning of a pandemic, without confirmatory data.

Finally, we believe that a current priority in the field of LUS research is to define the LUS pattern(s) seen with COVID‐19 with a large study that addresses sensitivity/specificity of the different patterns. The radiology community has been successful in standardizing the terminology of chest radiography and chest computed tomography. The same would need to be done for LUS.

Supplementary video 1

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Supplementary video 2

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